CHEMICAL ANALYSIS OF OILS, FATS, AND WAXES CHEMICAL ANALYSIS OF OILS, FATS, WAXES AND OF THE COMMERCIAL PRODUCTS DERIVED THEREFROM FOUNDED ON BENEDIKT’S SECOND EDITION OF ‘ANALYSE DER FETTE’ BY Dr. J. LEWKOWITSCH, F.I.C., F.C.S. CONSULTING AND ANALYTICAL CHEMIST, AND CHEMICAL ENGINEER ; EXAMINER IN SOAP MANUFACTURE, AND IN FATS AND OILS, INCLUDING CANDLE MANUFACTURE, TO THE CITY AND GUILDS OF LONDON INSTITUTE SECOND THOROUGHLY REVISED AND ENLARGED EDITION TP CT71 14*7 ILonlion MACMILLAN AND CO., Limited NEW YORK: THE MACMILLAN COMPANY 1898 A ll rights reserved PREFACE TO THE SECOND EDITION The gratifying fact that the First Edition has been exhausted in so comparatively short a time could but act as an incentive to me to increase, as far as possible, the usefulness of this work. The daily use of the book in the laboratory showed me the necessity for a more logical exposition, and accordingly the subject- matter of Chapters i.-viii. has been entirely rearranged, and to some extent amplified and rewritten. Separate chapters have been assigned to the Saponification of Fats and Waxes, and to the Chemistry of Resin, the importance of the matter fully justifying this step. Special attention has been paid to the Chapters ix. to xii., and nearly all the tables have been either re-cast or enlarged. This Second Edition claims, therefore, to be a thoroughly revised one. The new matter—not always consisting of abstracts of recently published papers—has been worked into and amalgamated with the context. I believe that no paper published on our subject during the last few years has escaped my attention; but in accordance with the principles laid down in the Preface to the First Edition, I have excluded matter which seemed to me of doubtful value, and relegated to footnotes those publications that appeared to be of minor im¬ portance. I hope that my criticism may meet with the approval of my pro¬ fessional brethren, for, in my opinion, the reader of a work of this kind does not merely want a compilation of facts, but also desires opinion for guidance. Where new methods or new lines of research have appeared likely to lead to an extended knowledge, I have taken care to point this VI OILS, FATS. AND WAXES out, and I hope that such hints may help to swell the ranks of workers, whose lines have been sadly thinned by the premature deaths of such eminent investigators as Benedikt and Alder Wright. The footnotes refer for more detailed information in the first instance to the pages of the Journal of the Society of Chemical Industry , it being assumed that this review is in the hands of every reader. Wherever that journal does not give an abstract of the original paper, other journals are used as reference in the order of easy accessibility to the majority of chemists. I have some doubts as to the advisability of adding a chapter on reagents and a series of tables frequently required in the laboratory, but the book being out of print, the consideration of this matter must be left for a subsequent edition. J. LEWKOWITSCH. December 1897 . PREFACE TO THE FIRST EDITION There has not hitherto been any English work dealing exclusively with the chemical analysis of Oils, Fats, and Waxes. I was on the point of writing one, in compliance with a wish expressed to me by several friends, when I was asked by Professor Benedikt to render his German work, Die Analyse der Fette und JFachsarten, into English, with such alterations as I thought necessary. As his book is undoubtedly the best on that subject, I thought, instead of adding to the number of text-books, it would be more useful to found on it an English edition, and to increase its usefulness as far as I was able. My task has therefore been a threefold one, to wit—to translate, revise, and enlarge the German work. Little can be said under the first head. A literal translation of the text, as far as it was retained, was, of course, out of the ques¬ tion. Especially when describing analytical processes the almost epic breadth in which our Continental brethren indulge made it necessary to leave out many details which would be found wearisome by English chemists. The revising of the work was the most important part of my task. I have often asked myself the question whether the writer of a book of this kind should not have himself tested all the methods he puts before his readers. But, on the one hand, it is impossible to personally examine every little modification or process, the description of which helps to swell the literature of our subject, whilst on the other hand to neglect this lays one open to the charge of hasty and presumptuous criticism. In revising I had to be guided by such experience as I have gained during many years devoted to the chemistry of Fats and Oils yin OILS, FATS, AND WAXES in the laboratory, as well as in the works which it has been my lot to manage both in this country and on the Continent. If this experience has led me to criticise somewhat freely, I trust I have not transgressed the limits which ought to be observed; but I consider that criticism is decidedly necessary in this branch of applied chemistry, abounding as it does with papers and communications, the contents of which can only have been new to their writers. Therefore the reader is con¬ stantly referred to the pages of the Journal of the Society of Chemical Industry —our own Jahresberichte —and other easily accessible journals. No useful purpose would be served by pointing out at length the numerous additions that have been made and the alterations which have been found necessary ; of these every page bears evidence. It may, however, be stated briefly that obsolete processes have been abridged or entirely left out, and that the arrangement of the subject- matter has been altered so as to suit practical requirements. A special feature is the tabular form adopted for the constants of the individual oils, fats, and waxes. In Chapters ix. -xii. large portions have been entirely re-written, and differ so widely from the original, that they may be regarded as substantially new, and in Chapter xi. a system of classification has been given which appeared to me the most natural one, at any rate in the present state of our knowledge. The enlarging has consisted, in the first instance, in devoting more space to the work of English and American chemists than would naturally be the case in a German publication. The new work in fat analysis published during the last four years has been embodied in the text, and all information up to the last weeks whilst the book has been in the press has been included. A large number of my own experiments and observations have been extracted from my note-books and published here for the first time. Thus the bulk of the book has been almost doubled notwithstanding extensive abridgments. The responsibility for these alterations and additions rests with me. My object has been throughout to place a book before my colleagues, containing in a handy and easily accessible form all the information which is required in the practice of the analytical and technical chemist,—in short, a compendium such as I should have wished to have beside me for my own reference in the laboratory. Great as the temptation has been to the contrary, the description of technical processes has been compressed within the narrowest limits, PREFACE IX and only those points have been emphasised which are required to give the analyst the necessary clue as to the lines to be adopted in the course of analysis. I trust also that the scientific aspect of the subject has not been lost sight of, as indeed it ought not to be, for, to quote from Benedikt’s preface, “The analysis of fats presents an almost complete system, such as is found in no other branch of technical organic analysis,—a system which will admit of application in the examination of ethereal oils, resins, balsams, and substances of a similar nature. For these reasons the analysis of fats and waxes may serve the student as the best introduction to the study of organic technical analysis.” It is hoped that, through the amalgamation of scientific accuracy with practical knowledge, a Avork has been produced that by its com¬ pleteness may prove useful to the analytical, technical, and scientific chemist, as well as to the teacher of chemistry. In conclusion, I wish to acknowledge my great indebtedness to my friend, Mr. William McDonnell Mackey, who has carefully read both the MS. and the proofs, with a view to making corrections in the language and freeing the text from any idiomatic harshness J. LEWKOWITSCH. February 1895. CONTENTS CHAPTER I PHYSICAL AND CHEMICAL PROPERTIES OF FATS AND WAXES PAGE Fats (Liquid and Solid) ....... 1 Chemical constitution of fats. Preparation and properties of pure glycerides ...... .1 Monostearin, 2. Distearin, 3. Triacetin, 3. Tributyrin, 3. Triisovalerin, 4. Trilaurin, 4. Trimyristin, 4. Tripalmitin, 4. Tristearin, 4. Triarachin, 4. Tricerotin, 5. Trimelissin, 5. Triolein, 5. Trielaidin, 5. Trierucin, 5. Tribrassidin, 5. Triricinolein ....... 5 Foreign substances in fats ....... 3 Fi - ee fatty acids in fats ....... 7 Properties of fats and fatty oils ...... 8 Rancidity of fats . . . . . . . .11 Behaviour with reagents . . . . . . .13 Waxes (Liquid and Solid) ..... .14 Chemical constitution of waxes. Preparation and properties of pure waxes ......... 14 Cetyl palmitate, 15. Octodecyl palmitate, 15. Ceryl palmitate, 15. Myricyl palmitate, 15. Cetyl stearate, 15. Ceryl cerotate, 15. Cocceryl coccerate, 15. Cholesteryl palmitate, 16. Cholesteryl oleate, 16. Cholesteryl stearate, 16. Isocholesteryl stearate . 16 Foreign substances in waxes . . . . . .16 Free fatty acids and free alcohols in waxes . . . .16 Properties of waxes . . • • • ■ .17 CHAPTER II SAPONIFICATION OF FATS AND WAXES Saponification of fats . . • • • • .18 Purification of alcohol . . • • • • .19 Cold saponification . ...... 20 Saponification of waxes ....... 22 iii'ilMHI xii OILS, FATS, AND WAXES CHAPTER III CONSTITUENTS OF FATS AND WAXES PAGE A. ACIDS..26 Occurrence of fatty acids ....... 26 Properties of fatty acids ....... 27 Melting points, 27. Boiling points, 30. Solubility, 30. Action on indicators, 31. Methylorange, 31. Plienolphthalein, 32. Litmus, 33. Lacmoid, 33. Viscosity of fatty acids, 33. Salts of fatty acids, 33. Salts of the alkali-metals, 33. Hydrolysis of soaps, 35. Metallic soap . . . . . . . .41 I . Acids of the Acetic Series, C„H 2 „0 2 . . . .42 Acetic acid, 42. Butyric acid, 42. Isovaleric acid, 43. Isobutylacetic acid, 43. Caprylic acid, 44. Capric acid, 44. Umbellulic acid, 44. Laurie acid, 44. Myristic acid, 45. Isocetic acid, 45. Palmitic acid, 46. Daturic acid, 47. Margaric acid, 47. Stearic acid, 47. Arachidic acid, 49. Behenic acid, 49. Lignoceric acid, 49. Carnaiibic acid, 50. Hyamic acid, 50. Cerotic acid, 50. Melissic acid ..... 51 II. Acids of the Oleic Series, C„H 2 n _ 2 0 2 . . . .52 Tiglic acid, 53. Acids C 12 H 22 O 2 and C 14 H 26 O 2 , 53. Hypogseic acid (Gai'dic acid), 53. Physetoleic acid, 53. Lycopodic acid, 54. Asellic acid, 54. Oleic acid, 54. Elai'dic acid, 57. Iso-oleic acid, 57. Rapic acid, 58. Doeglic acid, 58. Jecoleic acid, 59. Erucic acid, 59. Brassidic acid, 59. Iso-erucic acid 60 III. Acids of the Linolic Series, C„H2„_ 4 02 . ... . 60 Elseomargaric acid, 60. Linolic acid, 60. Tariric acid, 61. Millet oil acid ........ 61 IV. Acids of the Linolenic Series, C„H2 n -60 2 . . .62 Linolenic acid, 62. Isolinolenic acid, 62. Jecoric acid . . 62 V. Acids of the Series C re H2n-80 2 ..... 63 Isanic acid, 63. Therapic acid . . . . .63 VI. Hydroxylated Acids, C n H 2 „0 3 ..... 63 Lanopalmic acid, 63. Acid C 21 H 42 O 3 , 64. Cocceric acid . . 64 VII. Acids of the Eicinoleic Series, C„H 2 /l _20 3 . . .64 Ricinoleic acid, 64. Ricinisoleic acid, 64. Ricinelaidic acid, 65. Ricinic acid ....... 66 VIII. Acids of the Series C n H 2 u0 4 ..... 66 Diliydroxylated acids, 66 . Dihydroxystearic acid, 66 . Lanoceric acid ........ 66 Appendix to the Fatty Acids ..... 67 I. Hydroxylated Acids ...... 68 1. Monohydroxylated acids, C„H 2 „ 0 3 . . . .68 /3-Hydroxystearic acid, 68 . a-Hydroxystearic acid, 69. Stearolactone ...... 69 CONTENTS xiii PAGE I. Hydkoxylated Acids— continued. 2 . Dihydroxylated acids, C n H 2n 04 . . . .69 Tigliceric acid, 69. Dihydroxypalmitic acid, 70. Di- hydroxyasellic acid, 70. Dihydroxystearic acid, 70. Dihydroxystearidic acid, 70. p-Dihydroxystearic acid, 70. Dihydroxyjecoleic acid, 70. Dihydroxybehenic acid, 70. Isodihydroxybehenic acid, 71. Para- dihydroxy behenic acid . . . . .71 3. Trihydroxystearic acids, CisH^OaCOH^ . . .71 Trihydroxystearic acid, 71. a-Isotrihydroxystearic acid, 71. £!-Isotrihydroxystearic acid . . .71 4. Tetrahydroxystearic acid, CjsHaoO^OHh (Sativic acid) . 72 5. Hexahydroxystearic acids, CisH 3 0 O 2 (OH ) 8 . . .72 Linusic acid, 72. Isolinusic acid .... 72 II. Dibasic Acids ....... 72 Suberic acid, 73. Azelaic acid ..... 73 B. ALCOHOLS. 73 I. Alcohols of the Ethane Series, C m H>„ +2 0 . . .73 Cetyl alcohol, 74. Octodecyl alcohol, 74. Carnaiibyl alcohol, 74. Alcohol C 24 H 50 O, 75. Ceryl alcohol, 75. Isoceryl alcohol, 75. Myricyl alcohol (Melissyl alcohol) . . . .75 II. Alcohols of the Allylic Series, C„H 2 „0 . 75 Lanolin alcohol, 76. Alcohols C 15 H 30 O and C 3 G H 72 0, 76. Psyllo- stearyl alcohol . . . . . . .76 III. Alcohols of the Glycolic Series, C n H 2 „ + 2 0 2 . . .76 Alcohol C^HggOo, 76. Cocceryl alcohol . ... 76 IV. Alcohols of the Series C m H 2 n+ 2 0 3 . . . .77 Glycerol, 77. Ethers of glycerol, 80. Reactions of glycerol, 80. Isoglycerol . . . . . . .83 V. Alcohols of the Aromatic Series . . . .83 Cholesterol, 83. Isocholesterol, 85. Phytosterol . . 86 CHAPTER IV DETERMINATION OF FOREIGN MATTERS OF A NON-FATTY NATURE, AND PREPARATION OF THE FATTY SUBSTANCE FOR ANALYSIS 1. Sampling .... ..... 87 2 . Estimation of water ....... 88 3. Determination of foreign matters of a non-fatty nature in fats . . 88 4. Determination of fat . . . . . .90 5. Preparation of the fat for examination ..... 92 6 . Determination of inorganic substances in the fatty matter . . 95 Sulphur, 95. Phosphorus, 97. Chlorine, 97. Metals, 97. Copper, 98. Lead, 98. Iron ....... 99 7. Preparation of the insoluble fatty acids of a fat for examination . . 99 8 . Weighing of the fat for analysis . . . . . .101 XIV OILS, FATS, AND WAXES CHAPTER Y PHYSICAL METHODS OF EXAMINING FATS AND WAXES PAGE 1. Consistency and viscosity . . . . . • .102 Viscosimeters, 105. Redwood’s viscosimeter, 107. Saybolt’s, 109. Engler’s 109 2. Spectroscopical examination . . . . • .113 3. Determination of the refractive power . . . . .113 Abbe’s refractometer, 115. Butyro-refractometer, 116. Pulfrich’s refractometer, 117. Oleo-refractometer . . . .119 4. Rotatory power of the plane of polarisation .... 120 5. Microscopical appearance ....... 121 6. Electrical conductivity ....... 121 7. Critical temperature of dissolution ...... 122 8. Determination of the specific gravity . . . • .123 Sprengel’s picnometer, 125. Specific gravity of solid fats . . 128 9. Melting and solidifying points . . . . • .130 Solidifying points of fats, 132. Solidifying points of fatty acids, 133. Solidifying or freezing points of oils, 135. Freezing mixtures . 136 CHAPTER VI CHEMICAL METHODS OF EXAMINING FATS AND WAXES 1. Ultimate Analysis of Fats and Waxes . . . .137 2. Qualitative Examination of Fats of known Origin by strictly Scientific Methods ...... .138 A. Examination of the acid constituents ..... 139 Examination of the volatile acids, 139. Examination of the non-vola¬ tile acids, 140. Fractional crystallisation, 140. Oxidation of the liquid acid, 141. Fractional distillation . . . 144 B. Examination of the basic constituents. . . . .146 3. General Methods of Quantitative Analysis of Fats, or Mixed Fats and Waxes ....... 147 A. Quantitative Reactions . . . . . • .147 i. The acid value . . . . . • .148 ii. The saponification value (Kottstorfer value), 151. Saponifica¬ tion equivalent . . . ■ • .153 iii. The ether value . . . . • • .154 iv. The Reichert-Meissl value, 154. Baryta value. . . 159 v. The Hehner value . . . • • .160 vi. The acetyl value. ...... 162 vii. The (bromine or) iodine value, 167. (a) Bromine value, 167 (b) Iodine value ..... 170 CONTENTS XY PAGE B. Quantitative Determination of some Constituents of Fats and Waxes . 181 i. F ree fatty acids and neutral fat; mean molecular weight of the fatty acids . . . . . . .182 ii. Diglycerides . . . . . . .190 iii. Soluble (volatile) and insoluble (non-volatile) fatty acids . 191 iv. Saturated and non-saturated fatty acids—Proportion of liquid and solid acids in the insoluble fatty acids . . .192 v. Mixed palmitic, stearic, and oleic acids, other non-volatile fatty acids being absent, 196. Determination of oleic acid, 197. Determination of stearic acid, 198. Determination of palmitic acid, 199. Determination of oleic, palmitic, and stearic acids ....... 201 vi. Approximate determination of liquid fatty acids — oleic and linolic ....... 202 vii. Hydroxy acids ....... 204 viii. Lactones—Inner anhydrides ..... 206 ix. Glycerol, 207. Determination of glycerol by titration with caustic potash, 208. Determination of glycerol by oxidation processes, 208. Determination of glycerol by the acetin process ....... 213 x. Higher aliphatic alcohols ..... 213 CHAPTEE VII DETECTION AND QUANTITATIVE DETERMINATION OF UNSAPONI- FIABLE MATTER IN FATS AND WANES 1. Detection of Unsaponifiable Matter. . . . .217 2. Quantitative Determination of Unsaponifiable Matter . . 218 i. Gravimetric methods . . . . . . 218 ii. Volumetric methods ... . . . . . 222 3. Detection of Small Quantities of Fat in Mineral Oils . . 223 4. Examination of the Unsaponifiable Matter .... 224 i. Liquid unsaponifiable substances, 224. Mineral oils, 224. Tar oils, 225. Resin oils, 225. Discrimination between mineral, resin, and tar oils ........ 225 ii. Solid unsaponifiable substances ..... 229 CHAPTEE VIII DETECTION AND QUANTITATIVE DETERMINATION OF RESIN IN FATS OR FATTY ACIDS i. Properties of resin ........ 234 ii. Detection of resin when admixed with fats, fatty acids, and waxes . 238 iii. Quantitative determination of resin in neutral fats . . . 239 iv. Quantitative determination of resin acids in admixture with fatty acids . 240 b xvi OILS, FATS, AND WAXES PAGE 1. Barfoed’s method, 240. 2. Gladding’s method, 241. 3. Twitchell’s method ........ 244 v. Quantitative determination of resin in admixture with fats or fatty acids and unsaponifiable matter ...... 249 vi. Separation of resin from fatty matter ..... 250 CHAPTER IX APPLICATION OF PHYSICAL AND CHEMICAL METHODS TO THE SYSTEMATIC EXAMINATION OF FATTY OILS AND LIQUID WAXES Organoleptic Methods . . . . . . 252 A. Application of Physical Methods in the Identification of Indi¬ vidual Oils and Recognition of their Purity . . . 254 i. Specific gravities of fatty oils and liquid waxes . . . 254 ii. Solidifying points of fatty oils, 259. Melting and solidifying points of some fatty acids ....... 260 iii. Optical methods of examination ..... 261 Spectroscopical examination ..... 261 Refractometric examination ..... 261 Polarimetric examination ...... 267 iv. Viscosimetric examination ...... 268 v. Difference in the solubility of oils as a means of identification . 269 Solubility in alcohol ...... 269 Solubility in acetic acid, Valenta’s test .... 270 Solubility in carbolic acid . . . . .274 vi. Other physical properties . . . . . .274 Cohesion figures . . . . . . .274 Pattern test........ 275 Electrical conductivity . . . . . .275 vii. Critical temperature of dissolution . . . . .276 B. Application of Chemical Methods in the Identification of Indi¬ vidual Oils and Recognition of their Purity . . . 277 Liquid waxes 277. Fish, liver, and blubber oils, 278. Drying and non-drying oils . . . . . . .279 1. Ela'idin test ........ 280 2. Sulphur chloride test ....... 282 3. Oxygen absorption test. Livache test..... 285 4. Thermal tests ...... . . 291 Thermal reaction with sulphuric acid : Maumene test . . 291 Thermal reaction with sulphur chloride .... 298 Thermal reaction with bromine ..... 300 5. Quantitative reactions . . . . . 302 Saponification values....... 302 Hehner values ....... 306 Reichert (Meissl) values ...... 306 Iodine (and Bromine) values ..... 307 Acetyl values . . . . . . 313 6. Qualitative reactions ....... 313 Colour reactions . . . . . . .314 Distinction between animal and vegetable oils . . . .317 CONTENTS XVII CHAPTER X APPLICATION OF PHYSICAL AND CHEMICAL METHODS TO THE SYSTEMATIC EXAMINATION OF SOLID FATS AND WAXES PAGE 1. Specific gravities of solid fats and waxes ..... 321 2. Melting and solidifying points of solid fats and waxes . . . 323 3. Melting and solidifying points of the mixed fatty acids from fats and waxes ......... 325 4. Behavionr with solvents ....... 328 5. Hehner values . ....... 328 6. Reichert-Meissl values ....... 329 7. Saponification values ....... 329 8. Iodine (and Bromine) values ...... 329 9. Acetyl values ........ 333 Thermal tests ....... 333 Sulphur chloride test ....... 333 Refractive index........ 333 CHAPTER XI DESCRIPTION OF NATURAL FATS AND WAXES : METHODS OF EXAMINING THEM AND DETECTING ADULTERATIONS A. OILS AND FATS. GLYCERIDES 336 I. Oils or Liquid Fats ....... 336 1. Vegetable Oils ....... 336 (1) Drying Oils . . . . . .336 Linseed oil . . . . . 336 Japanese wood oil . . . . . 345 Lallemantia oil . . . . .347 Hemp seed oil . . . . . 348 Walnut oil—Nut oil ..... 350 Poppy seed oil ..... 352 Niger seed oil ..... 354 Sunflower oil ...... 356 Fir seed oil . . . . . . . 358 Madia oil . . . . . . 360 Candle nut oil ..... 362 Isano (Ungueko) oil. . . 362 Mohamba oil ...... 363 Garden rocket oil . . . .363 Henbane seed oil . . . . 365 Celosia oil . . . . . 365 Indian laurel oil ..... 365 Tobacco seed oil ..... 365 Weld seed oil ...... 366 OILS, FATS, AND WAXES xviii PAGE (2) Semi-drying Oils ...... 336 a. Cotton seed oil group . . . . 336 Cameline oil (German Sesame oil) . . . 337 Soja bean oil . . . . . 389 Pumpkin seed oil . . . . .371 Maize oil—Corn oil . . .372 Kapok oil ..... 375 Cotton seed oil . . . . . .375 Sesame oil (Gingili oil, Teel oil) . . . 335 Basswood oil . . . . 393 Beechnut oil . . . . . 393 Brazil nut oil . . . . . 395 j3. Rape oil group ...... 397 Garden cress oil ..... 397 Hedge mustard oil .... 399 Rape oil [Colza oil] ..... 399 Black mustard oil .... 407 White mustard oil .... 409 Radish seed oil . . . . . .411 Jambo oil ..... 413 y. Castor oil group ...... 413 Croton oil ..... 414 Curcas oil (Purging nut oil) .... 416 Grape seed oil . . . . . . 418 Castor oil ..... 420 (3) Non-drying Oils ...... 426 Cherry kernel oil . . . . . 426 Cherry laurel oil . . . . . 428 Apricot kernel oil . . . . . 428 Plum kernel oil ..... 430 Peach kernel oil ..... 432 Wheat-meal oil . . . . 434 Acorn oil ...... 434 Almond oil . . . . . . . 435 Sanguinella oil ..... 440 Californian nutmeg oil .... 441 Arachis oil (Peanut oil, Earthnut oil) . . . 441 Rice oil ...... 447 Tea seed oil . . . . . . . 447 Pistachio oil . . . . . . . 449 Hazelnut oil . . . . . . . 449 Olive oil ...... 451 Olive kernel oil ..... 464 Coffee berry oil . . . . .465 Ungnadia oil . . 466 Ben oil ... . 467 Strophantus seed oil . . 467 Secale oil . . . . 468 CONTENTS xix PAGE 2. Animal Oils ....... 468 (1) Marine Animal Oils ...... 469 a. Fish oils . . . . . . .470 Menhaden oil . . . . .470 Sardine oil. Japan fish oil . . . 472 /3. Liver oils . . . . . .474 Cod liver oil. Cod oil. Coast cod oil . . .475 Shark liver oil. Haddock liver oil. Skate liver oil . 489 y. Blubber oils ...... 490 Seal oil.490 Whale oil.492 Dolphin oil (Black fish oil) .... 495 Porpoise oil . . . . • 497 (2) Terrestrial Animal Oils ..... 499 Sheep’s foot oil ..... 499 Horses’ foot oil ..... 501 Egg oil ...... 503 Neat’s foot oil ...... 504 II. Solid Fats ........ 506 1. Vegetable Fats ...... 506 Cotton seed stearine ...... 506 Chaulmoogra oil . . . . . .508 Carapa oil (Crab wood oil) ..... 509 Laurel oil. . . . . . . . 509 Mowrah seed oil (Mahwah butter) . . . .511 Shea butter (Galam butter) ..... 513 Vegetable tallow (of China) . ., . . .515 Palm oil . . . . . . . . 517 Macassar oil ...... 520 Sawarri fat ...... 521 Mafura tallow ....... 521 Nutmeg butter (Mace butter) ..... 523 Rambutan tallow ...... 526 Mkanyi fat ...... 526 Cacao butter ....... 527 Kokum butter, Goa butter, Mangosteen oil . . 531 Borneo tallow ....... 533 Dika oil (Oba oil) ...... 533 Mocaya oil ...... 534 Palm nut oil ...... 535 Cocoa nut oil ...... 537 Myrtle wax . ...... 542 Ucuhuba fat ...... 544 Japan wax ....... 546 Malabar tallow (Piney tallow) ..... 549 Wild olive fat ...... 550 XX OILS, FATS, AND WAXES PAGE 2. Animal Fats ....... 550 Blackcock, wild duck, domestic duck, starling, pigeon, turkey, fox, badger, pine marten, chicken, polecat, dog, wild cat, domestic cat, elk, roebuck, fallow buck, chamois . . 551 Horse fat . . . . . . . . 552 Horse marrow fat ...... 555 Hare fat . . . . . . . . 555 Rabbit fat ...... 557 Goose fat . . . . . . 559 Human fat ...... 562 Lard ........ 563 Lard oil . . . . . . 534 Beef marrow fat . . . . . . 586 Bone fat . . . . . . . 587 Tallow ........ 591 Tallow oil ....... 591 Beef tallow ....... 592 Mutton tallow . . . .598 Butter fat ....... 601 Stag fat . . . . . . . 641 B. WAXES.643 I. Liquid Waxes ....... 643 Sperm oil ....... 643 Arctic sperm oil (Bottlenose oil) ..... 647 II. Solid Waxes ........ 649 1 . Vegetable Waxes ....... 649 Carnauba wax ....... 649 2. Animal Waxes ....... 651 Wool wax (Wool grease) ...... 651 Beeswax ....... 655 Spermaceti (Cetin) ...... 669 Insect wax (Chinese wax) ..... 672 CHAPTER XII TECHNICAL AND COMMERCIAL ANALYSIS OF THE RAW MATERIAL AND PRODUCTS OF THE FAT AND OIL INDUSTRIES A. Oleaginous Seeds and Oil Cakes ..... 673 B. Fats and Oils ........ 676 1. Synthetical fats. Acetine ...... 676 2. Edible fats and oils ....... 678 (a) Edible fats ....... 678 Butter substitutes . . . . 678 Lard substitutes . . . . . .682 ( b ) Edible oils. Salad oils (Sweet oils) ... 684 3. Burning oils ........ 685 4. Paint oils ........ 685 CONTEXTS xxi PAGE C. Waste Fats ........ 686 ]. Wool fat, Wool grease (Recovered grease, Brown grease) . . 686 (a) Pure (Anhydrous) wool fat. Adeps Lanse . . . 689 ( b ) Lanoline ....... . 689 (c) Distilled grease ....... 690 2 . Cotton seed foots ....... 692 3. Fuller’s grease—“ Seek oil ” ...... 693 4. Black oil ...... 693 5. Sod oil—Degras ....... 693 D. Wool Oils—Cloth Oils ...... 704 E. Lubricating Oils ........ 712 1. Fatty oils and liquid waxes . . . . . 718 2'. Mineral oils ........ 719 3. Mixtures of fatty and mineral oils ..... 722 4. Solid lubricants—Greases . . . . . .726 F. Turkey-red Oils ........ 726 G. Oxidised Oils ........ 733 1. Blown oils, Base oils, Thickened oils, Soluble castor oil . . 733 2 . Boiled oil ...... . 735 3. Lithographic varnish . . . . . . .739 Linoleum ........ 741 H. Vulcanised Oils. Rubber Substitutes .... 742 I. Candles ......... 745 1. Tallow candles . . . . . . .745 2 . Stearine candles . . . . . . .745 3. Wax candles . . . . - . . .755 4. Sperm candles . . . • . . . .756 5. Paraffin wax candles . . . . . . .757 6 . Cerasin candles . - . ■ . . .763 K. Commercial Oleic Acid. Oleine, Elaine . . . .765 L. Soaps ......... 769 I. Soaps of the alkali metals . . . . . .769 II. Insoluble soaps (Metallic soaps) ..... 785 M. Glycerin . . . . . . . . . 786 1. Chemically pure glycerin . . . . . .786 2 . Dynamite glycerin ...... . 802 3. Crude glycerin ........ 805 CHAPTER XIII EXAMPLES 1 . Tournant oil ........ 811 2. Commercial acetine . . . . . . . .812 3. Composition of butter fat . . . . . . 812 4. Product obtained by the action of zinc chloride on oleic acid . . 812 5. ‘ ‘ Recovered grease ” ....... 816 6 . Distilled grease ........ 820 CHAPTER I PHYSICAL AND CHEMICAL PROPERTIES OF FATS AND WAXES Under the term natural fats and waxes (liquid and solid) we com¬ prise all those substances that are formed in animals and plants, and consist mostly of glycyl,—or other ethers of the higher members of the several series of fatty acids, sometimes in conjunction with the free fatty acids themselves. A systematic classification of the fats and waxes is not yet possible, all attempts at establishing different classes or groups based on physical differences having hitherto failed. Thus the consistency has been made the basis of a classification into oils, lards, and solid fats; and some authors have tried to differentiate the fats into several groups by making use of some chemical properties of the fats, as the drying properties, etc.; but the old adage “ natura non facit saltum ” has proved too strong for these artificial classifications, inasmuch as there exist a number of intermediate fats which might be classified under two or more heads. A distinct difference, however, can be established between fats and waxes on chemical grounds. Considered chemically the fats are the neutral glycerides of fatty acids, whilst the waxes are ethers formed by the union of fatty acids and alcohols of the ethane (and perhaps also of the allylic) series. This chemical difference, however, does not always find a ready expression in common parlance. Thus, e.g. Japan wax con¬ sists chiefly of glycerides, whilst on the other hand sperm oil, according to its chemical constitution, must be classed amongst the waxes. For the sake of convenience we subdivide in this work the fats and waxes into liquid and solid ones. The liquid fats are also termed fatty oils or, in short, oils. 1. Fats (Liquid and Solid) Chemical Constitution of Fats. Preparation and Properties of Pure Glycerides The fats are the product of the combination of glycerol and fatty acids. Glycerol being a trihydric alcohol, and consequently deporting B 2 PHYSICAL AND CHEMICAL PROPERTIES OF FATS AND WAXES ch. itself like a trihydric base, is able to combine with three radicles of fatty acids, as expressed by the following equation, in which R represents the acid radicle of any fatty acid :— O.H 0. R C 3 H 5 0. H + 3R . OH = C 3 H 5 0. R + 3H 2 0. O.H O.R The resulting compounds are called “ triglycerides ” or “ neutral glycyl ethers,” and they may be compared to neutral salts ; there¬ fore the triglycerides are also called neutral fats, and their nomen¬ clature is similar to that of salts. Thus we speak of glyceryl stearate or stearic glyceride, etc. This constitution of the fats has been established by the classic researches of Chevreul ( Les Corps Gras d’origine animate. Paris, 1815-1823. Reprinted 1889), Berthelot, and Wurtz. Adopting this constitution of the neutral fats, theory pre¬ dicts the possible existence of diglycerides and monoglycerides corresponding to the formulae O.R 0:R C 3 H 5 0 . R and C 3 H 5 0 . H O.H O.H. In nature only the triglycerides occur, the monoglycerides and digly¬ cerides are apparently not met with in freshly rendered fats. Allen’s conjecture that Japan wax contains the diglyceride of palmitic acid, O.R C 3 H 5 0 . R 0. H (R = C 16 H 31 0), has not been confirmed. Will and Reimer, however, have found in old rape oil the diglyceride of erucic acid, C 3 H 5 (0. C 22 H 41 0) 2 0H, but this exception to the general rule is only an apparent one, as it is most likely that the rape oil in question had become rancid with formation of free erucic acid, whilst dierucin separated as a solid mass. The mono- and diglycerides can be prepared synthetically by heating fatty acids with glycerol ( Berthelot). Thus, on heating equal parts (by weight) of stearic acid and glycerol in a sealed tube for twenty-six hours at 200° C., part of the contents is converted into monostearin 1 according to the following equation— C 3 H s (0H) 3 + C 18 H 35 0. OPI = C 3 H 5 (0 . C 18 H 35 0)(0H) 2 + H 2 O. The monostearin is isolated by separating off the fatty substance floating on the unchanged part of the glycerol, dissolving it in ether, adding slaked lime to convert the unchanged stearic acid into its calcium salt, warming a little and finally extracting with boiling ether. Monostearin crystallises in microscopic needles, melting point 61 C. It distils unchanged in vacuo. It dissolves with some difficulty in cold ether, but readily in hot ether and hot alcohol. Distearin is prepared by heating equivalent quantities of mono- 1 The spelling “acetin,” “stearin,” etc., denotes in this work the pure triglycerides, whilst under “acetine,” “stearine,” etc., the commercial products are understood. X TRIACETIN—TRIBUTYRIN 3 stearin and stearic acid in a retort up to 150°-180° C., and at last from 180° to 200° C., until one molecule of water has passed over. It crystallises from alcohol in needles, melting point 76'5° C. It is very slightly soluble in cold alcohol, readily so in 150 parts of boiling alcohol; it is easily soluble in warm ether, petroleum ether, chloro¬ form, and benzene. 1 A great many fats may be considered as mixtures of the trigly¬ cerides of the several fatty acids, say of tripalmitin, tristearin, and triolein. It may be noted in favour of this assumption, that from the liquid oils tripalmitin and tristearin separate out on cooling either in their pure state or as a mixture. It is, however, not unlikely that there exist fats which consist of mixed ethers of glycerol, i.e. ethers containing in one molecule the acid radicles of several different fatty acids combined with glycerol. Thus, experiments by Bell have rendered probable the existence of an oleo-palmito-butyrate, of the formula C 3 H 5 (0 . C 18 H3 3 0)(0. C 16 H 31 0)(0 . C 4 H 7 0), in cow butter (cp. Butter Fat, chap. xi. p. 605). Recently Heise stated that oleodistearin occurs in Mkanyi fat and in Kokum butter 2 ) (cp. p. 526). The most important of the triglycerides, because most largely occurring in nature, are tripalmitin, tristearin, and triolein. The following triglycerides have been prepared in a state of purity :— Triacetin, Acetin, C 3 H 5 (0. C 2 H 3 0) 3 , is prepared by heating 20 c.c. of glycerol with 10 c.c. of acetic anhydride and 50 grms. of finely powdered hydrogen potassium sulphate. As soon as a violent reaction sets in 20 c.c. more of acetic anhydride are added and the mixture boiled for some time. The cooled mass is exhausted by means of ether, and thus a mixture of triacetin and diacetin is obtained, which can be separated into its components by fractional distillation. Triacetin boils at 258°-259° C. under ordinary pressure ; at 171° C. under 40 mm. pressure. Its specific gravity is IT603 at 15° C. (water 15° C. = l). 3 It is miscible with alcohol, ether, chloroform, benzene ; it is, however, insoluble in carbon bisulphide and petroleum ether. 3 Tributyrin, Butyrin, C 3 H 5 (0. C 4 H 7 0) 3 , is obtained on boiling one molecule of glycerol with three molecules of butyric acid for sixty hours. It is a butter-like mass, distilling unchanged at 285° C. Its specific gravity is 1‘056 at 8° C., 1’052 at 22° C. Butyrin when boiled with strong alcohol and a quantity of caustic potash insufficient for complete saponification yields ethyl butyrate. 1 Monocerotin, dicerotin, monomelissin, and dimelissin have been prepared syn¬ thetically by Marie {Jour. Chem. Soc. 1896, Abstr. i. 347). 2 Arbeiten aus dem Kaiserlichen Gesundheitsamte, 1896, xii. 540 ; xiii. 302, Oleodi¬ stearin, C 3 H 5 (0. C 18 H 33 0)(0. C 18 H 35 0) 2 , obtained by precipitating with alcohol the ethereal solution of these fats, is stated to melt at 44°-44‘5° C., and to solidify at 40'8°. If the melted glyceride is cooled rapidly, the melting point is 27°-28° C., and rises gradually, on keeping at the ordinary temperature, to 37°-38° C. Its specific gravity at 70° C. is 0-8928, and at 98° C. 0'8547. Although Heise has no doubt as to the individuality of the oleodistearin, it appears (to me) strange that the mixed fatty acids, consisting roughly of 33 per cent oleic acid and 66 per cent stearic acid, should have as high a melting point as 60°-62° C. (cp. Dalican’s table, chap. xii. p. 750). 3 100 c.c. of water at 15° C. dissolve 7 ‘17 grms. Geitel, Jour, joraktische Chemie, 1897 [55], 420. 4 PHYSICAL AND CHEMICAL PROPERTIES OF FATS AND WAXES ch. Triisovalerin, Valerin, C 3 H 5 (0. C 5 H 9 0) 3 , is formed by heating synthetical divalerin with 8-10 parts of isovaleric acid to 220° C. It is soluble in alcohol and ether. Trilaurin, Laurostearin, Laurin, C 3 H 5 (0. C 12 H 23 0) 3 , has been isolated by boiling pichurim beans or laurel oil with alcohol. It is stated to occur in the liver fat of a crustacean. 1 It crystallises in needles, melting point 45° C. Sparingly soluble in cold absolute alcohol, it dissolves readily in ether. Trimyristin, Myristin, C 3 H s (0 . C u H 27 0) 3 , has been found in nutmeg butter, and in the wax from cochineal. It crystallises from its ethereal solution in laminae, melting point 55° C. When melted tri¬ myristin is heated to 57°-58° C. it solidifies into a porcelain-like mass, melting at 49° C. Heated again for a very short time to 50° C. it solidifies and regains the original melting point, viz. 55° C. Trimyris¬ tin is easily soluble in ether, benzene, and chloroform. Tripalmitin, Palmitin, C 3 H 5 (0. C 16 H 31 0) 3 , has been obtained syn¬ thetically by heating either dipalmitin with palmitic acid, or a mixture of glycerol and palmitic acid, when mono- and dipalmitin are formed simultaneously. The tripalmitin is isolated by dissolving the mixture in alcohol and allowing it to crystallise, when small nacreous crystals of the triglyceride are obtained. They dissolve with very great diffi¬ culty in cold alcohol, more easily in hot alcohol, separating from this solution in flocks. Ether dissolves tripalmitin in every proportion. The crystals melt at 62° C., also 63°-64° C., solidifying at 45'5° C., also 45°-47° C.; this change in the melting and solidifying points seems to depend on slight differences of manipulation, such as the rapidity of heating the crystals, and on the temperature they have been cooled down to. Tristearin, Stearin, C 3 H 5 (0 . C 18 H 35 0) 3 , is obtained by heating mono¬ stearin with 15-20 parts of stearic acid for three hours at 275° C. It is a crystalline substance, still less soluble in cold alcohol than palmitin ; solutions of tristearin in boiling alcohol deposit the dissolved substance nearly completely on cooling. Judging from the melting points, there exist two modifications of stearin, one melting at 71'6° C., the other at 55° C. The stearin obtained by crystallisation from ether melts at 7T6° C., and solidifies at 70° C. to an indistinctly crystalline mass; this, when heated above its melting point—by at least four degrees—solidifies at about 52° C. to a wax-like mass, melting at 55° C.; and on heating this modification a few degrees above its melting point, the former substance, having the melting point 7T6°C., is again obtained. The specific gravity of a (not quite pure) specimen of stearin in the melted state was found to be 0‘9235 at 65‘5° C. Stearin distils un¬ changed in vacuo. Tristearin is partially converted into ethyl stearate by boiling with a solution of sodium in absolute alcohol {Duffy), or by heating with small quantities of alcoholic potash {Bonis). On substituting amyl alcohol for ethyl alcohol, amyl stearate is obtained. 1 Cthem. Zeit. 1895, 651. I TRIARACHIN—TRIRICINOLEIN 5 Triarachin, Arachin, C 3 H 5 (0. C 20 H 39 O) 3 , prepared by Berthelot from diarachin and arachidic acid, is very slightly soluble in ether. Tricerotin, Cerotin, C 3 H 5 (0. C 25 H 49 0) 3 , has been prepared by Marie 1 from dicerotin. It crystallises in slender needles, melting at 76-5°-77° C. Trimelissin, Melissin, C 3 H 5 (0. C 30 H 59 O) 3 , was obtained from di- melissin by Marie} It resembles cerotin; its melting point is 89° C. Cerotin and melissin apparently do not occur in nature. Triolein, Olein, C 3 H 5 (0 . C 18 H 33 0) 3 . This glyceride 2 has been ob¬ tained by heating glycerol with an excess of oleic acid at 240° C. Olein is a liquid substance which has not been obtained hitherto in the solid state ; it distils in vacuo without decomposition. Its specific gravity at 15° C. is O’QOO. Olein dissolves easily in ether; in absolute alcohol it is more readily soluble than either palmitin or stearin; it is insoluble in dilute alcohol. Olein combines with concentrated sulphuric acid to form a saturated compound having the formula (C 3 H 5 ) 2 (0 . C 18 H 34 0. S0 4 . C 18 H 34 0.0) 3 ; 3 this substance is very unstable, and is partly dissociated on treatment with water or alcohol into H 2 S0 4 and a-hydroxystearic acid. Just as oleic acid is converted by nitrous acid into elaidic acid (p. 57), so olein is converted under the same conditions into elaidin. Trielaidin, Elaidin, C 3 H 5 (0. C 18 H 33 0) 3 , crystallises in warts, melt¬ ing point 32° C. (Mayer), 38° C. (Duffy). It dissolves readily in ether, but is nearly insoluble in alcohol. Trierucin, Erucin, C 3 H 5 (0. C 22 H 41 0) 3 , is prepared like olein. It is a crystalline mass, of the melting point 31° C. Nearly insoluble in alcohol, it dissolves very readily in ether, benzene, and petroleum ether. Nitrous acid converts trierucin into tribrassidin. Tribrassidin, Brassidin, C 3 H 5 (0 . C 22 H 41 0) 3 , is a crystalline powder, melting point 47° C. When heated above its melting point it solidi¬ fies, on cooling, into another modification (?), melting at 36° C. Triridnolein, Bicinolein, C 3 H 5 (0 . C 18 H 33 0) 3 , has been synthetised by heating ricinoleic acid with glycerol at 120°-130°, unchanged glycerol and ricinoleic acid being removed by water and petroleum ether re¬ spectively. 4 If Berthelot’s method be employed, i.e. pressure and high temperature, condensation products of mono- and di-ricinolein are formed, the simplest of which is isomeric with triricinolein, and has the formula OH . C 17 H 32 . COO. C 17 H 32 . COO . C 3 H 5 (C 17 H 32 . COOH) 2 . When triricinolein is boiled with toluene, either alone or in presence of zinc chloride, it is condensed to various ethers, such as that repre¬ sented by the formula [(OH. C 17 H 32 . COO) 2 C 3 H 5 . C 17 H 32 . C0] 2 0, which differ from triricinolein by their sparing solubility in alcohol and petroleum ether. H. Meyer 5 describes triricinolein (prepared by heating ricinoleic 1 Jour. Chem. Soc. 1896, Abstr. i. 347. 2 Coula oil is stated to consist of almost pare olein {Jour. Soc. Chem. Ind. 1895, 493). 3 Cp. also Juillard, Jour. Soc. Chem. Ind. 1894, 820. 4 Juillard, Jour. Chem. Soc. 1895, Abstr. i. 500. 5 Jour. Soc. Chem. Ind. 1897, 633, 684. 6 PHYSICAL AND CHEMICAL PROPERTIES OF FATS AND WAXES oh. acid and glycerin to 280°-300 C.) as a colourless oil, soluble in 96 per cent alcohol, and in methyl alcohol, having the specific gravity 0-959-0-984, and [a] D = + 5-16°. Unlike castor oil it does not form ricinelaidin on treating with nitrous acid. On keeping, the molecule becomes doubled or trebled, the specific gravity being increased to 0-988-1-009 and the iodine number decreasing from 71-84 to 44-57. Foreign Substances in Fats In consequence of the mode of preparation adopted, the fats are generally found to contain impurities of one kind or another, such as remnants of animal or vegetable tissue, or other foreign substances. These, for the most part, can be got rid of by washing with water (the solid fats must be washed in a melted state), with subsequent drying and filtering. The fats purified as described above still contain small quantities of foreign substances, such as minute traces of colouring matters (causing the colour reactions which are characteristic of some fats), albuminoid substances 1 occurring in fats of animal origin, or cellulose, found in fats and oils prepared from seeds. These substances are dissolved in the fats, and appear after saponification, on decomposing the soaps with acid, as flocculent matter between the aqueous and the fatty acid layers. According to Allen and Thomson’s 2 researches, all the fats contain traces of unsaponifiable substances, either hydrocarbons (?) or higher alcohols. The occurrence of the latter may be explained by assuming the presence of minute quantities of wax-like substances in the fats. Allen and Thomson have examined the following fats quanti¬ tatively :— Pat. Unsaponifiable. Per cent. Olive oil. 0-75 Rape oil (German) .... 1-00 Cotton seed oil. 1-64 Lard ....... 0-23 Cod liver oil .... 0-46-1-32 Japan wax...... 1-14 In the case of some of the fats the unsaponifiable substance consists of cholesterol, isocholesterol, or phytosterol. Fahrion 3 found in the course of an examination of thirty samples of various liver and blubber oils percentages of unsaponifiable matter (cholesterol) varying between 0-49 and 5'27. A specimen of egg oil contained 1-5 per cent of cholesterol. 1 Yssel de Scliepper and Geitel, Dingl. Polyt. Jour. 245, 295. 2 Chemical News, 43. (1881), 267. 3 Jour. Soc. Chem. Ind. 1893, 607. I LECITHIN—FREE FATTY ACIDS 7 The fats from seeds of Leguminosse and Graminaceee, and also some fats of animal origin, as egg oil, contain not inconsiderable quantities of lecithin, C 44 H 90 O 9 PN. This substance is split up, on saponification, into fatty acids, glycerolphosphoric acid and choline. ( Hoppe-Seyler gives the following formula for lecithin : c 3 h 5X / - (C 18 H 35 0 2 ) 2 OHN(CH 3 ) 3 - 0. PO< '0 - C. 2 H 4 - OH' The following table contains the proportion of lecithin found in a few fats :— Pat from Phosphorus. Per cent. Corresponding to Lecithin. Per cent. Observer. Peas 1-17 30-5 1 Topler Wheat 0-25 6-5 1 3 / Egg Yolk — 0-2 Kitt Schulze and Likiernik , 2 have also shown that lecithin is widely distributed in seeds (though absent from the husks), and that it passes to a considerable extent into their ethereal extracts. Free Fatty Aeids in Fats Animal fats, when freshly prepared, contain but infinitesimal quantities of free fatty acids, and may therefore, for practical purposes, be considered as consisting of absolutely neutral glycerides. Fats of vegetable origin, however, mostly contain notable amounts of free fatty acids. Experiments made by Rechenberg 3 have shown that unripe seeds contain considerably larger quantities of free acids than ripe ones. In the seeds, which have been gathered in the unripe state, chemical changes take place, resulting in a diminution of free fatty acids with formation of neutral fats. Archbutt 4 has found in 151 samples of olive oil from 0‘5 to 25‘2 per cent of free fatty acids calculated to oleic acid. Nordlinger 5 has determined the amount of free fatty acids in the oils mentioned in the subjoined table; the percentages have also been calculated for oleic acid. 1 These numbers appear to the writer extraordinarily high. As it seems probable that the potassium hydrate used in converting the phosphorus into phosphoric acid contained considerable quantities of alumina, these figures should be accepted with reserve. 2 Berichte 1891 71 3 Ibid. 1881, 2217. 4 Jour. Soc. Chem. Ind. 1889, 685. 5 Ibid. 1889, 806. 8 PHYSICAL AND CHEMICAL PROPERTIES OF FATS AND WAXES ch. Oils and Fats. Percentage of Free Fatty Acids. Minimum. Maximum. Mean. A. Oils. Rape—Salad oil . 0-53 1-82 1-19 Commercial oil 0-52 6-26 2-88 Extracted oil . 077 1-10 0-93 Olive—Salad oil .... 1-66 Commercial oil 3-87 27T6 12-97 Poppy seed—Salad oil 0-70 2-86 1-92 Commercial oil 12-87 17-73 15-37 Extracted oil . 2-15 9-43 4-72 Arachis—Salad oil 0-85 3-91 1-94 Commercial oil 3-58 10-61 6-52 Extracted oil 0-95 8-85 4-02 Sesame—Salad oil 0-47 5-75 1-97 Commercial oil 7-17 33-13 17-94 Extracted oil 2-62 9-71 4-89 Cotton seed—Salad oil 1 0T5 Commercial oil 0-42 0-50 0-46 Mustard—Expressed oil 0-68 1-02 0-85 Castor—Expressed oil ... 0-62 18-61 9-28 Extracted oil ... 1-18 5-52 2-78 Linseed — Commercial 0-41 4-19 1-57 Candle nut—Commercial . ... 56-45 B. Solid Fats. Palm nut—Commercial, expressed 3-30 17-65 6-91 Extracted 4-17 11-42 8-49 Palm (old sample) 50-82 Cocoa nut—Commercial, expressed 3-03 14-35 7-92 Extracted 1-00 6-31 4-26 Mowrah seed—Commercial. 28-54 Illipd—Extracted 14-40 34-72 24-56 Ucuhuba—Expressed .... 18-55 Japan wax ...... 9-25 The amount of free fatty acids in vegetable fats increases on keeping. This is specially noticeable in the case of palm oil, which gradually de¬ composes, on standing for some time, into free fatty acids and glycerol. Properties of Fats and Fatty Oils The glycerides that occur naturally and that are free from fatty acids, or have been freed therefrom by chemical operations, are either liquid at ordinary temperature, or at least may be melted below 100° C. without decomposition. In the cold the solid fats become harder, whilst most of the liquid fats solidify. Liquid fats easily penetrate into the pores of dry substances. If dropped on paper they leave a transparent spot—grease-spot—which cannot be removed by washing with water and subsequent drying. (Difference from glycerol spots.) 1 Fresh cotton seed oil is entirely free from fatty acids, owing to its being refined by means of caustic alkalis. I PROPERTIES OF FATS AND FATTY OILS 9 A curious effect caused by fats, which may be used for the detection of the minutest quantities, has been described by Lightfoot. Camphor, crushed between layers of paper without having been touched with the fingers, rotates when thrown on water, but a trace of fat on the surface of the water causes the rotation to cease im¬ mediately ; it is sufficient to touch the water with a needle which has been passed previously through the hair. For analytical purposes the fats may be considered as completely insoluble in water, although traces are dissolved when the liquid fats are shaken with large quantities of water. On allowing the emulsions, thus obtained, to become clear by standing, separating the fat, filtering the aqueous layer, and shaking the latter with ether, a minute quantity of fat passes into that solvent, and may be recovered by evaporating the ether. On the other hand fats dissolve a little water ; on heating, however, the last trace of moisture is expelled. With the exception of castor oil, croton oil, and olive kernel oil, all fats dissolve but very sparingly in cold alcohol. Thus, according to Jiingst, 100 parts of alcohol, specific gravity 0'83, dissolve at 15° C. : 0'534 parts of rape oil, 0‘642 parts of linseed oil, and CF561 parts of grape seed oil. Boiling alcohol, however, dissolves somewhat larger quantities of fats, especially of the liquid ones; but, on cooling, nearly all the dissolved fat separates completely. The solubility is con¬ siderably increased by the presence of a large amount of free fatty acids (cp. chap. ix. p. 272). The fats dissolve very readily in ether, carbon bisulphide, chloroform, carbon tetrachloride, benzene, petroleum, and petroleum ether. Castor oil, however, is insoluble in the two last-mentioned solvents. Pure stearin alone is but sparingly soluble in ether, one part of the triglyceride requiring 200 parts of ether; in the presence of other glycerides, how¬ ever, the solubility of stearin in ether is much increased. The solutions of the neutral fats are without action on indicators, provided, of course, that the solvents used have been completely freed from traces of acids. In their pure state the fats and oils are odourless, colourless, and tasteless; and what is usually regarded as characteristic in these respects of the different oils and fats is really due to the presence of small quantities of foreign substances. On exposure to sunlight (and to air) even strongly coloured oils are gradually bleached, some oils becoming almost colourless. The specific gravity of the fats and oils is less than that of water ; it varies between the limits of 0‘910 to CL970. Fats and oils dissolve sulphur and phosphorus at the ordinary temperature 1 to a slight extent. 2 Soaps are also somewhat soluble in fats. Notable quantities of soaps, however, are dissolved by solutions of fats in ether or petroleum ether. 1 At temperatures above 100° C. sulphur interacts with fats (cp. p. 14). 2 On the solubility of indigo in fats and oils cp. Jour. Soc. Chem. Ind. 1895, 1027. Iodine is stated to be soluble in liver oils to the extent of 20 per cent, and in neat’s foot oil up to 33 per cent (Focke, Phami. Zeit. 1896, 616). 10 PHYSICAL AND CHEMICAL PROPERTIES OF FATS AND WAXES ch. The fats can be heated up to about 250° C. without undergoing any change. When further heated, decomposition sets in owing to the destruction of the glycerol, with formation of volatile products, the most characteristic of which is acrolein. The intense odour of acrolein, which all fats emit on heating above 250° C., is one of the most characteristic criterions to distinguish fats and fatty oils from mineral or ethereal oils. Amongst the volatile products obtained on heating the fats and fatty oils to high temperatures are found hydrocarbons, the quantity of which is considerably increased when the heating and the destructive distillation takes place under pressure. This fact lends strong support to the theory that the hydrocarbons of petroleum owe their origin to the destruction of animal fats. On exposure to the atmosphere the fats and oils gradually undergo certain changes. The change is most marked in the case of the so- called dnjing oils (linseed oil, walnut oil, hemp seed oil, poppy seed oil, etc.) They thicken and dry with absorption of oxygen, and if exposed in sufficiently thin layers, e.g. spread on wood or glass, they are converted finally into a transparent, yellowish, flexible substance, insoluble in water and alcohol. This substance is called varnish. The change is attended by an increase in weight (Livache’s test, see chap, ix. p. 285), and it takes place all the more readily if the oils have been mixed previously with certain metals or metallic compounds (“driers”), as lead, copper, or litharge, manganese borate, etc. The “drying” oils differ from the “non-drying” oils chemically in that they contain large amounts of the glycerides of linolic and linolenic acids, or other acids belonging to the same series. The non-drying oils remain unchanged at the ordinary temperature (cp. p. 279) when absolutely pure and protected from light and air. The commercial oils, however, acquire, on exposure to air, a disagree¬ able smell and an acrid taste, at the same time becoming slightly thicker and acid to litmus ; they turn “ rancid,” as the term runs. In the course of this alteration small quantities of volatile acids (butyric, isobutylacetic, and other acids) are formed, and the glycerol is also partially decomposed. At the same time the amount of free, non-volatile fatty acids increases considerably; in some cases, as in palm oil, the fats are split up into their components, fatty acids and glycerol. Rancidity is, however, not due, as is generally believed, to the liberation of free acid; for, as Ballantyne 1 has shown, in many instances (olive oil, castor oil, etc.) rancidity sets in and continues for some time without the liberation of any free acid whatever, whilst in other instances free acid is liberated long before the fat has turned rancid (cotton seed oil, linseed oil). Heyerdahl 2 (before him) had proved for cod liver oil, that addition of its free fatty acids (from 2 per cent downwards) to samples of oil free from rancidity did not impart to the oil a rancid character, although it certainly produced a 1 Jour. Soc. Chem. Ind. 1891, 29. 2 Ibid. 1889, 54. Cp. also Besana, Chem. Zeit. 1891, 410, and v. Klecki, Zeit. f. analyt. Chemie, 1895, 633. I RANCIDITY OF FATS 11 sharp taste; thus no connection could be traced between rancidity and the proportion of free fatty acid. 1 Therefore fats cannot be called “ rancid ” because of the presence of free fatty acids alone; this term must be reserved rather for those fats containing an excess of free fatty acids due to the action of air (Nordlinger ), and, it should be added, exhibiting the peculiar taste of rancid fats. The changes accompanying rancidity have been described by some authors as due to the action of certain foreign substances which are supposed to act as ferments. Others, again, point to a possible action of micro-organisms, a theory which seemed to have been supported by the discovery of living micro-organisms in poppy seed oil ( Kirchner 2 ). But Duclaux 3 has shown in an investigation of butter fat that micro¬ organisms play no such part, 2 the fat, being insoluble in water, not affording any nutriment to the protoplasma of the cells; rancidity is rather due to slight hydrolysis and the subsequent action of the oxygen in the air assisted by light, the influence of which is enhanced the larger the surface of the exposed fat is. Eitsert , 4 who has recently instituted • an exhaustive examination into the causes of rancidity, has summed up his results in the following propositions: Pure lard is not turned rancid by bacteria, either aerobic or anaerobic, the bacteria introduced into the fat dying quickly. The action of ferments must also be excluded, sterilised fat, heated to a temperature of 140° C. (whereby ferments are destroyed), having become rancid on subsequent exposure to light and air. Nor can a certain amount of moisture be considered a necessary factor, experiments having shown that dried fats are more liable to turn rancid than such as contain a small quantity of moisture. Kancidity must, therefore, be considered due to direct oxidation by the oxygen of the air, this action being intensified by exposure to light. 5 Both oxygen and light must act simultaneously on fats and oils in order to produce rancidity, either of these agents alone being unable to cause any alteration in that respect. Nitrogen and hydrogen do not act on fats ; nor does carbonic acid cause them to turn rancid. [The last-mentioned gas, however, seems to have some action on lard, imparting to it a tallow-like taste.] Solid fats, especially those of animal origin, are less liable to turn rancid than liquid fats; the former resist better the action of light and air; indeed, it may be taken as a rule that the higher the pro¬ portion of stearin and palmitin, and the smaller the percentage of olein in a fat, the less will be its liability to become rancid. 1 Scala (Le Stazione sperimentaZe agric. ital. 28, 733) proposes to measure the rancidity of fats other than butter by their proportion of free volatile acids. 2 Berichte der deutsch. botan. Gesellschaft, 1888, 101 ; cp., however, p. 617. Zopf, Schmidt, Ritthausen, and Baumann have collected several kinds of fungi which consume fats, but it is very likely that in these cases an enzyme or similar body is the cause of the disappearance of the fats. 3 Annates de Vlnstitut Pasteur, 1887 ; Compt. rend. 102, 1077. 4 Untersuchungen uber d. Ranzigwerden der Fette. Inaug. Biss. Berlin, 1890. 5 Mjoen ( Forschungsberichte uber Lebensmittel, etc., 1897, 201), states that light is not necessary, and that the chemical change taking place in presence of air and under action of light differs from that occurring in absence of light. 12 PHYSICAL AND CHEMICAL PROPERTIES OF FATS AND WAXES ch. The properties of rancid fats differ in some respects from those of neutral fats (see further below). It has generally been assumed that it is principally oleic acid that is set free on fats becoming rancid. Experiments, however, made by Thwn, 1 with palm oil and olive kernel oil in order to ascertain if palmitic, stearic, and oleic acids are liberated in the same or in a different proportion to that in which they exist in those two fats, have proved that the ratio between oleic and the solid fatty acids is the same in the free as in the combined state. This fact was confirmed by Spaeth in the case of rancid lards. Afew data regarding therancidity of some fats may be recorded here. Lenz has found that a specimen of horse fat, exposed to the atmosphere for two years, increased by 3‘5 per cent in weight. Afterwards the weight remained constant. The ultimate analysis showed that the percentages of carbon and hydrogen had decreased (from 76-72 per cent C to 71-05, and from 12-17 per cent H to 10 - 95 per cent) whilst the oxygen had increased. The insoluble fatty acids decreased by 5 per cent, the amount of soluble fatty acids having at the same time been increased. Whilst it has been found by general experience (and confirmed by Allen’s and Ritsert’s researches) that fats kept in closed vessels remain unchanged for an indefinitely long time, Langbein 2 states that several animal fats which had been kept in corked bottles for ten years had acquired a rancid smell with formation of free fatty acids. He concludes from an “acetyl value” (cp. chap. vi. p. 162) he has found that hydroxy acids had been formed. The same conclusion has been arrived at by Wctchtel 3 when examining very old samples of fat; and also by Heyerdahl , 4 who states that cod liver oil prepared with exclusion of air was free from hydroxy acids, whereas the oil heated in contact with air gave distinct “ acetyl values.” These experiments, however, cannot be looked upon as conclusive, the method of examination employed leaving room for doubt (compare Acetyl Value, chap. vi. p. 164), and the statement frequently met with in papers published by German analysts that hydroxy acids are formed when fats become rancid must be accepted with due reserve. In contrast with these statements, and supported by ample evidence gained from experiments extending over four years, Groger 5 has found for six kinds of fat that they suffer but little change if air be excluded, with one exception, viz. palm oil. An examination of the fatty acids isolated from the fats thus exposed showed, without an exception, that a splitting up of the fatty acids into acids of a lower molecular weight had taken place, instead of their undergoing change by mere additive absorption of oxygen. (This excludes the formation of hydi-oxy acids.) Further evidence in that direction was afforded by the isolation of azelaic and suberic acids in that portion of the rancid fat that was soluble in water. As to the glycerol, 1 Jour. Soc. Chem. Ind. 1891, 70. 2 Muspratt’s Chemie von Stohmann und Kerl III. (1891), 505. 3 Jour. Soc. Chem. Ind. 1890, 979. 4 Cod Liver Oil and Chemistry, by P. Moller, p. 93. 909 I BEHAVIOUR OF FATS WITH REAGENTS 13 Groger concludes that it must suffer oxidation as well as the fatty acids, since free glycerol could not be found. On blowing air —or, better still, oxygen —through fatty oils heated to the temperature of boiling water, oxidation takes place with evolution of heat sufficient to allow the oxidation process to continue without further heating. The most notable change is a large increase in the density, and the oils thus obtained, especially those from cotton seed oil, resemble very much castor oil in their density and viscosity, but differ from it in that they are soluble in petroleum ether. These oils are known in commerce under the name of blown oils, oxidised oils, base oils, or soluble castor oil, and are used for lubricating purposes (cp. chap. xii. p. 733). The drying oils subjected to this oxidising process yield jelly-like masses. The blown oils are characterised by a large amount of soluble non-volatile acids and triglycerides of hydroxy acids. On mixing a fatty oil with concentrated sulphuric acid a considerable rise in temperature takes place with evolution of sulphurous acid (see chap. ix. p. 291, Maument test). If the oil be mixed very gradually with the acid, and at a low temperature, glycerides of a complex constitution are formed. Thus on treating olive oil with concentrated sulphuric acid a compound has been obtained which may be regarded as a triglyceride of oleic acid, stearic sulphuric acid, and hydroxy- stearic acid, 1 possessing the formula C 3 H 5 [0 . C 18 H 33 0] . [0.0 i8 H 34 (S0 4 H) . 0] . [0 . C 18 H m (0H)0]. Concentrated nitric acid attacks the fats, acting on them violently and with copious evolution of red fumes. Hot dilute nitric acid oxidises the fats gradually. Fahrion 2 concludes from some experiments that all glycerides of unsaturated acids when acted on with nitric acid give rise to the formation of hydroxy acids, which on further treatment with nitric acid are said to be converted into nitro-derivatives of hydroxy acids. This statement, however, being of a preliminary nature, stands in need of confirmation. On treatment with nitrous acid the non-drying oils become solid, or acquire the consistency of butter according to the proportion of triolein (trierucin, etc.) they contain; the triolein (trierucin, etc.) being converted into the solid isomeride triela'idin (trierucin, etc.) (cp. chap. ix. p. 281). Drying oils, on the other hand, remain liquid when similarly treated, although at the same time their chemical and physical properties are considerably modified. Lidoff z states that their specific gravity increases as also their viscosity and saponification value, whereas the iodine and the Hehner values decrease. All oils, after treatment with nitrous acid, contain, according to the same author, nitrogen varying in amount from 1 to 2‘5 per cent. These substances may be reduced, yielding new compounds, which probably contain the NH 2 group. The free unsaturated acids yield no such compounds. On passing chlorine through fats hydrochloric acid is evolved, and 1 Geitel, Jour. Soc. Chem. Ind. 1888, 219. 2 Zeitsch. f. angew. Chemie, 1891, 74. 3 Jour. Chem. Soc. 1893, Abstr. ii. 559. 14 PHYSICAL AND CHEMICAL PROPERTIES OF FATS AND WAXES ch. similarly on treating with bromine hydrobromic acid, with formation of glycerides of chloro- or bromo-substitution products of the fatty acids. If triglycerides of the unsaturated acids are treated in this manner, the fatty acids may also absorb chlorine or bromine with formation of additive products. Iodine does not yield substitution products, and is but slowly absorbed when mixed with a solution of a fat. The absorption, how¬ ever, takes place readily if, following Hilbl’s process (chap. vi. p. 170), an alcoholic solution of iodine and mercury bichloride is allowed to act on a chloroformic solution of the fats. The glycerides of the unsaturated acids most likely absorb in that case one atom of iodine and one atom of chlorine for each pair of doubly-linked carbon atoms. Thus oleic acid is converted into chloro-iodo-stearic acid (oleic chloro- iodide), C 1S H 34 C1I0 2 , a colourless compound of lard-like consistency, becoming brown with separation of iodine. The products obtained by the interaction of the alcoholic iodine and mercury bichloride solu¬ tion and fats are viscous or varnish-like substances. Sulphur does not act in the cold on fats and oils. At higher temperatures, however, from 120° to 160° C., all oils assimilate sulphur, and it would appear that the sulphur is absorbed much in the same manner as iodine is absorbed by oils. Experiments made by Altschul 1 have demonstrated that stearic acid is hardly acted upon by sulphur at a temperature of about 130° C., whereas oleic acid treated with 10 per cent of sulphur at 130°-150° C. absorbs the sulphur without any evolution of sulphuretted hydrogen. In a similar manner fatty oils (as containing glycerides of the unsaturated fatty acids), notably linseed oil, castor oil, rape oil, cotton seed oil, and marine animal oils, absorb sulphur at 120°-160° C. On cooling, the sulphur does not separate out, and on saponifying the sulphurised oils in the cold, 2 sulphurised fatty acids are obtained, whilst very little sulphuretted hydrogen is evolved. 3 The action of sulphur chloride on fats and oils will be described further on (chap. ix. p. 282). 2 . Waxes (Liquid and Solid). The waxes occur in both the vegetable and animal kingdoms, carnaiiba wax and common beeswax being the best-known representa¬ tives of both types. Chemical Constitution of Waxes. Preparation and Properties of Pure Waxes The most essential point of difference between fats and waxes has been already explained. The fats are the glycyl ethers of the 1 Jour. Soc. Ohem. Ind. 1896, 282. 2 On heating the sulphurised fatty acids to 130°-200° C., however, sulphuretted hydrogen escapes in large quantities, substitution of hydrogen in the molecule of the fatty substance taking place. 3 Henriques, Jour. Soc. Chem. Ind. 1896, 282. I CONSTITUTION OF WAXES—CETIN—COCCERIN 15 higher fatty acids, whilst the waxes proper must be considered as ethers formed by the combination of mono- or dihydric alcohols with higher fatty acids. Thus cetin, or cetyl palmitate, is obtained from cetyl alcohol and palmitic acid by abstraction of water, accord¬ ing to the following equation— C 16 H 33 . OH + C 15 H 31 . CO. OH = C 16 H 33 .0. CO . C 15 H 31 + H 2 0. Therefore, whilst the fats and fatty oils have one common con¬ stituent in their basis—viz. the trihydric alcohol: glycerol—the waxes are characterised by their basic constituents being monohydric and dihydric alcohols. The alcohols hitherto identified in waxes belong to both the aliphatic and aromatic series ; the former being represented by alcohols of the ethane, allylic, and glycolic series, the latter by the cholesterols. The fatty acids of the waxes are either liquid or solid; no acid of a lower number of carbon atoms than myristic acid has been found hitherto. The fatty acids of wool wax are remarkable for the ease with which they are converted into lactones. 1 The following pure “ waxes ” have been isolated :— Cetyl Palmitate, Cetin, C 16 H 33 .0 . CO. C 15 H 31 , occurs largely in sper¬ maceti, being its chief constituent. It is prepared by repeatedly re-crystallising spermaceti from ether. Cetin forms white crystals, melting at 55° C., easily soluble in boiling alcohol, but nearly insoluble in cold alcohol. In a vacuum cetin can be distilled unchanged. When distilled under ordinary pressure, or even under a pressure of 300 to 400 mm., it is split up into palmitic acid and the hydrocarbon hexadecylene (cetene), according to the following equation— C 16 H :53 .0. CO. C 15 H 31 =:C 16 H 32 0 2 + C 16 H 32 . Octodecyl Palmitate, C 1S H 3Y .0 . CO . C 15 H 31 . This wax forms crystals, melting at 59° C. Ceryl Palmitate, C 2Y H 55 .O.CO. C 15 H 31 , is the chief constituent of opium wax. It crystallises from boiling alcohol in small prisms, having the melting point 79° C. The melted substance solidifies at 76° C. Myricyl Palmitate, Myricin, C 30 H 61 .O.CO. C 15 H 31 , is the chief con¬ stituent of that part of beeswax which is insoluble in alcohol. It forms feather-like crystals, melting at 72° C. Cetyl Stearate, C 16 H 33 .0 . CO . C lY H 35 , forms large scales resembling those of spermaceti. Its melting point is 55°-60° C. Ceryl Cerotate, C 2Y H 55 ; . O.CO.C 26 H 53 , occurs in Chinese wax, which consists almost exclusively of this ether. It has also been found in opium wax, and very likely occurs in wool fat. Ceryl cerotate forms snow-white, lustrous scales (from chloroform), melting at 82 - 5° C. Cocceryl Coccerate, Coccerin, C 30 H 60 (O. C 31 H 61 0 2 ) 2 , has been found in the wax from cochineal. It is obtained as nacreous, thin laminae (from benzene), melting point 106° C. Coccerin is nearly insoluble 1 Lewkowitsch, Jour. Soc. Ohem. Ind. 1892, 132 ; 1896, 14. 16 PHYSICAL AND CHEMICAL PROPERTIES OF FATS AND WAXES ch. in cold alcohol or ether, and dissolves with great difficulty in cold benzene and glacial acetic acid. Cholesteryl Palmitate, C 26 H 43 .0 . CO . C 15 H 31 , occurs in blood-serum it forms snow-white plates, melting at 77°-78° C. Cholesteryl Oleate, C 26 H 43 .0 . CO . C l7 H 33 , has been found conjointly with the palmitate in blood-serum. 2 It crystallises in long, thin needles, melting at about 41° C., soluble in ether, chloroform, and benzene, but only sparingly so in alcohol; the rotatory power is [a] D =18° 48'. Cholesteryl Stearate, C 26 H 43 .0 . CO . C l7 H 35 , has been prepared syn¬ thetically by heating one part of cholesterol with 8-10 parts of stearic acid to a temperature of 200° C. ( Berthelot ). It has been stated to occur in wool wax conjointly with the wax described next (compare wool wax, chap. xi. p. 652). It crystallises in small needles, melting at 65° C. This wax is nearly insoluble in alcohol, and but slightly soluble in ether. Isocholesteryl Stearate, C 26 H 43 . O.CO.C l7 H 35 , has also been obtained by synthetical methods. It crystallises in fine needles, melting point 72° C., and is but very slightly soluble in boiling alcohol. Liquid waxes occur in sperm oil. They most probably represent a combination of unsaturated alcohols, C W H 2W 0, with unsaturated fatty acids. 2 Foreign Substances in Waxes With the exception of carnauba wax and beeswax, the waxes have not been examined yet so thoroughly that general statements can be made under this head. In the case of these two waxes, however, the occurrence of hydro¬ carbons has been placed beyond doubt. The hydrocarbons of beeswax belong to the ethane series, and their melting points are high. The hydrocarbon found in carnauba wax is very likely a member of the same series. Free Fatty Acids and Free Alcohols in Waxes Whereas in the case of animal fats at least it is proved that the occurrence of free fatty acids must be considered as an indication of decomposition having taken place, the same cannot be said with certainty of the waxes—at any rate, in our present state of know¬ ledge. A certain proportion of free fatty acids is characteristic of carnauba wax, beeswax, and (natural) wool fat, whilst the liquid waxes and spermaceti are neutral in their fresh state. Perhaps the conjecture is permissible that the occurrence of free fatty acids is due to a secondary action if we bear in mind that in the 1 Hurthle, Jour. Chem. Soc. 1896, Abstr. ii. 485. 2 Lewkowitsch, Jour. Soc. Chem. Ind. 1892, 135. I PROPERTIES OF WAXES 17 waxes containing free fatty acids simultaneously free alcohol's are present. [Glycerol being so easily soluble in water, it is evident that in the case of fats the “ alcohol ” escapes detection.] Therefore these waxes contain notable amounts of unsaponifiable matter (partly due to presence of hydrocarbons). Properties of Waxes In their physical properties the liquid and solid waxes resemble very much the fatty oils and fats. When melted together they mix in all proportions. Their behaviour to solvents is similar; and, like fats, the waxes in a liquid condition or in solution leave a grease-spot on paper. It will, therefore, suffice to emphasise the points of difference. The liquid waxes are readily distinguished from fatty oils by their lower specific gravity,—from CP875 to (P881. On heating, the waxes do not emit the odour of acrolein, glycerol being absent; nor do they turn rancid on keeping for a long time, owing to the stability of their ethers (and the stability of their fatty acids). Although insoluble in water, the solid waxes have the property of forming emulsions with water, so much so that large quantities of water can be incorporated with them (cp. p. 690), yielding salve-like substances. c CHAPTER II SAPONIFICATION OF FATS AND WAXES The chemical change taking place on boiling fats with strong bases and resulting in the formation of glycerol and of the alkali salts of the higher fatty acids has been termed “ saponification.” In a wider sense, however, every chemical process by which fats or waxes are split up into their constituents—glycerol and fatty acids in the case of the fats, and higher alcohols and fatty acids in the case of waxes— is called saponification, even if no bases be used to effect the reaction. The term “ saponification ” is almost exclusively used in practice, its scientific synonym “hydrolysis” being confined to papers of a scientific character. The fats are decomposed on a very large scale by various chemical operations; they are “ saponified ” either by strong bases (caustic soda, caustic potash, lime), or by strong sulphuric acid, or by water alone, under a pressure of fifteen atmospheres (corresponding to 200° C.), or when distilled in a current of superheated steam. These methods will be detailed below (chap. xii. p. 745). In all these processes the fats undergo a perfectly definite chemical change, being split up into their constituents with the absorption of the elements of water. Thus, taking tristearin as an example, the following equation expresses the chemical change : x — C 3 H b (0 . C 18 H 35 0) 3 + 3H 2 0 = 3C 18 H 3B 0 2 + C 3 H 5 (OH) 3 . For analytical purposes the saponification is effected by means of strong bases only. The recently—somewhat needlessly—proposed process of saponifying butter by means of sulphuric acid will be dis¬ cussed further on under “Butter Fat” (chap. xi. p. 635). For many purposes, especially for the subsequent estimation of glycerol, it would be most convenient to use such bases as form insoluble salts with the fatty acids, e.g. lead oxide, lime, and baryta. Careful examination, however, has proved 2 that with these bases saponification of many fats (tallow, cacao butter) is not complete, part of the neutral fat escaping decomposition. Therefore, in the analysis of fats the saponification 1 Geitel has since shown (Jour, jorakt. Chemie, 1897 [55], 418) that the saponification takes place in three stages, diglycerides being formed first, then monoglycerides, which are ultimately broken up into glycerol and fatty acids. 2 v. d. Becke, Zeitsch.f. analyt. Chemie, 19. 291. CHAP. II SAPONIFICATION OF FATS 19 must be effected by means of caustic potash or caustic soda, if reliable results are to be obtained. All triglycerides are not saponified with the same facility. Thus, olein is acted upon with greater difficulty than palmitin and stearin, a fact which has led to the statement (and patent) that on mixing olive oil, which consists essentially of the glycerides, olein (stearin ?), and palmitin, with cold caustic soda, and shaking the mixture occasionally during twenty-four hours, olein only remains unchanged. It has, how¬ ever, been shown by Thum 1 that there is no marked difference between oleic and commercial stearic acids in their behaviour with caustic alkalis. On adding to a mixture of oleic and crude stearic acids an amount of caustic potash, insufficient to completely neutralise the acids, it was found that the composition of the acids that had been converted into soaps was almost the same as that of the acids that had remained free. Hence it is impossible to effect a separation of solid fatty acids from liquid ones by partial saturation with alkalis. The carbonates of the alkalis do not act like the caustic alkalis. Alcoholic solutions of the caustic alkalis saponify more readily than aqueous. Therefore, in the laboratory alcoholic soda and alcoholic potash are chiefly used for effecting saponification. If aqueous alkalis are employed for some special reason, saponification is completed only by prolonged boiling or by heating under pressure. As commercial alcohol is seldom free from traces of acid, it should be tested, and, if necessary, it must be neutralised with decinormal caustic alkali, using phenolphthalein as indicator, or it may be dis¬ tilled over lime or baryta. For the purpose of fat analysis rectified spirits of wine will, as a rule, be pure enough. It should be tested by boiling a few c.c. with several drops of concentrated caustic potash ; pure alcohol will not become brown, a slight yellow colour may, however, be allowed to pass. The appearance of a brown colour would point to the presence of aldehyde or acetone. If the cost of spirits of wine preclude its use, recourse may be had to methylated spirit. This alcohol may be purified for analytical purposes by the following method, proposed by Waller : 2 The alcohol is shaken with powdered potassium permanganate until it assumes a distinct colouration. It is allowed to stand for some hours until the permanganate has been decomposed and hydrated manganese peroxide is deposited. A pinch of calcium carbonate is then added, and the alcohol distilled from a flask provided with a Wurtz tube or a Le Bel- Henninger fractionating column at a rate of about 50 c.c. in 20 minutes. The distillate is tested frequently until 10 c.c. of it, when boiled with 1 c.c. of a strong (syrupy) solution of caustic potash, gives no yellow colouration on standing for 20 or 30 minutes. What distils after that is preserved for use ; care, however, has to be taken not to distil to dryness. The alcohol thus prepared is completely neutral, and is 1 Jour. Soc. Chem. Incl. 1891, 70. 2 Jour. Amer. Chem. ,Suc. 1889, 124 ; Analyst , 1890, 50. 20 SAPONIFICATION OF FATS AND WAXES CHAP. especially suitable for the preparation of alcoholic potash solution ; even on standing for a long time alcoholic potash made from such alcohol does not become discoloured. 1 It should be noted that alcohol is methylated at present (General Order as to Methylated Spirit, July 20th, 1891) by mixing with it mineral naphtha of a specific gravity of not less than 0'800. The admixed hydrocarbons are not got rid off by the foregoing processes of purification, but will pass over into the distillate with the alcohol. In estimations of “ unsaponifiable ” matter in fats this source of error must be specially guarded against. The following are convenient proportions for saponifying fats : To 10 parts (by weight) of the fat in a flask are added 30 to 40 parts of alcohol by volume, and 4 to 6 parts of solid caustic potash previously dissolved in 20 parts of water. The flask is then con¬ nected with an inverted condenser, and the contents are kept gently boiling for half an hour or an hour. These proportions may be varied within very wide limits. Thus Yssel de Scliepper and Geitel recommend 20 grms. of fat, 40 c.c. of caustic potash of specific gravity T4, and 40 c.c. of alcohol, whilst Dalican proposes to pour into 50 grms. of tallow, heated to 200° C., a mixture of 40 c.c. caustic soda, specific gravity T33, and 33 c.c. of 95 per cent alcohol with constant shaking. Yssel de Schepper and Geitel , 2 in order to accelerate the process of saponification, add some ether, thus ensuring a readier contact of the particles of fat and alkali. The same proposal has also been made by Hehner 3 and others ; but it is not recommended, as the presence of ether necessarily demands a lower temperature than would be required in many cases. Another method to saponify in the cold was recently proposed by Henriquesd His process consists in dissolving the fat in petroleum 1 Another method has been recommended by J. Carter Bell {Jour. Soc. Chem. Ind. 1893, 236), and is carried out as follows : 500 c.c. of methylated alcohol, about 85 or 90 per cent, are placed in a flask of about 1000 c.c. capacity, containing 25 grms. of stick potash. When the latter has been dissolved, 250 grms. of melted lard, or of some other saponifiable fat, are added. The flask is then connected with an inverted condenser and heated on the water-bath, when the fat is readily saponified, especially if the flask be shaken repeatedly. After the condenser has been inverted, about 450 c.c. of alcohol are distilled off. According to Carter Bell, the alcohol thus obtained will not turn brown on the addition of potash after several days, and when the solution is kept in a strong light only a slight yellow colour may be developed. This property of soap, to retain the im¬ purities of methylated spirit, is well known to manufacturers of transparent soap from stock soaps by dissolving them in boiling methylated spirit. The commercial methylated spirit when first used for this process yields a distillate which has a much less unpleasant smell than the crude spirit. At each subsequent time of using the methylated spirit a further improvement of the quality of the alcohol takes place ; ultimately a spirit is obtained which is quite free from the rank odour of the commercial article.— Kadel (Charm. Jour, and Transactions, 1894, 356) distils impure alcohol first over caustic soda—30 grms. for 5 litres—after allowing to stand for a few days. The distillate is next treated with permanganate and distilled off again. If necessary the latter operation is repeated and followed by filtration over charcoal. 2 Dingl. Polyt. Journal, 245, 295. 3 The Analyst, 1893. 4 Jour. Soc. Chem. Ind. 1896, 299, 476. The objections raised by Henriques to the usual method of saponification are groundless (cp. Holde, Jour. Soc. Chem. Ind. 1896, 476). II SAPONIFICATION OF FATS 21 ether and mixing with alcoholic soda ; on standing for 12 hours com¬ plete saponification takes place. Besides having the disadvantage, that an operation which can be easily finished in half an hour is unduly protracted, this method has the further drawback that the solution of alkali must be prej^ared with strongest alcohol, as it is essential to obtain a homogeneous liquid on mixing the alcoholic soda with petroleum ether. For these reasons, but chiefly because, on the author’s own showing, 1 wool wax is not saponified completely, this method cannot be recommended as one to replace the usual method. In the case of sulphurised (vulcanised) fats and oils, however, the cold saponification process may be used with advantage, as otherwise sulphur is eliminated from the fatty substance by boiling alcoholic potash to a far greater extent than in the cold. Those fats which are not saponified readily are best heated with the alcoholic potash under pressure. Becker heats the fat with twelve times its quantity of half-normal or normal alcoholic potash in a flask on the water-bath for half an hour, the flask being closed by a cork, fitted with a safety tube containing mercury. The flask is heated until the pressure equals 5 cm. mercury. The writer 2 uses for these purposes a copper bottle with a screwed stopper; the bottle may be immersed in water, and is not liable to breakage as seltzer-water bottles are. Kossel and Obermiiller 3 recommend sodium ethoxide (prepared by dissolving 5 grammes of metallic sodium in 100 c.c. of absolute alcohol) as the most readily acting reagent for saponification of fats. It is, however, difficult to see what advantages this method offers. The high price of metallic sodium and absolute alcohol, and the incon¬ venience of having to prepare the reagent afresh for each series of experiments, are not compensated for by the somewhat shorter time required for saponification. Furthermore, as the reaction proceeds according to the following equation— C 3 H 5 (0.0 18 H 35 0) 3 +3C 2 H 5 .0Na = C 3 H 5 (0Na) 3 + 3C 18 H 35 0.0. C 2 H 5 , with formation of sodium glyceroxide and the ethyl ethers of the fatty acids, the reacting masses must be heated, as in other processes, in order to allow the alcohol to absorb sufficient moisture from the air for the decomposition of the sodium glyceroxide into glycerol and sodium hydrate, which latter saponifies ultimately the ethylic ethers of the fatty acids. It will, therefore, be found preferable to use alcoholic potash for the saponification of oils and fats. An easy calculation will show that, theoretically, for the saponi¬ fication of 1 grm. of fat from 0 - 2-0'3 grm. of caustic potash are required at most ; but in order to obtain complete saponification an excess of the alkali must be used. On using a small quantity of caustic potash and strong alcohol all the glycerol may be split off; but 1 In a later paper Henriques maintains that wool wax is completely saponified, but his contention does not appear to be sufficiently substantiated. 2 Jour. Soc. Qhem. Ind. 1892, 137. 3 Zeitsch. f physiolog. Chemie, 15. 321-330. 22 SAPONIFICATION OF FATS AND WAXES CHAP. still part of the fatty acids are obtained as ethyl ethers. Thus J. Bell has found that on boiling cow butter with half the quantity of alcoholic potash required for complete saponification a light oil is obtained, solidi¬ fying at 43° C. This oil was looked upon by him as a diglyceride of the following composition—C 3 H 5 ( 0 H)( 0 C 16 H s1 0 )( 0 Cj 8 H 33 0 ) ; but it is actually a mixture of ethyl ethers of fatty acids. Allen 1 found similarly that, on heating acetin with the fiftieth part of alcoholic potash required for complete saponification, 39 per cent out of the theoretically possible quantity of ethyl acetate had been formed, whilst three-fiftieth parts of potash converted 85 per cent into acetic ether. A larger proportion of alkali diminished the yield of acetic ether; thus with sufficient caustic soda to saponify 39*8 per cent of the acetin used, the amount converted into acetic ether was 52*4 per cent. Kossel and Kruger 2 state that in their experiments with the sodium ethoxide method saponification was complete if the theoretical quantity of sodium was employed. If, however, the proportion of alcohol used for dilution was large, considerable quantities of ethyl stearate and palmitate were formed, and saponification could only be completed by boiling on the water-bath. Judging from their experi¬ ments, supported and amplified by Obermuller , 3 the sodium ethoxide appears to form sodium glyceroxide and ethylic salts of the fatty acids, as explained by the equation given above. The traces of water that adhere to the absolute alcohol decompose the sodium glyceroxide, and the caustic soda thus formed is enabled to saponify the more readily saponifiable ethylic salts. Considering that 1 grm. of fat requires no more than 0*06 grm. of water, the small quantities of water found in absolute alcohol, conjointly with the amount ab¬ sorbed from the atmosphere during the operation, may suffice to decompose the sodium glyceroxide. As the operation is usually completed on the water-bath there is ample occasion for the absorp¬ tion of water to take place. Moreover, experiments with carefully dried alcohol, whilst moisture from the atmosphere was rigidly ex¬ cluded, proved that, even after boiling continued for half an hour, about 30 per cent of the fat remained unsaponified. The waxes are decomposed by saponification into fatty acids and higher alcohols. Thus, myricin is split up into its constituents, palmitic acid (resp. its potassium salt) and myricyl alcohol, according to the following equation— C 15 H 31 CO . 0. C 30 H 61 + KOH = C 16 H 31 CO. OK + C 30 H 61 . OH. On diluting the alcoholic solution of a saponified wax with water, the higher alcohols, being insoluble in water, separate out and rise to the surface of the liquid, or remain suspended in it as a turbid mass. They are separated from the soap by shaking with ether, 1 Cheni. News, 1891, 64. 179. 2 Zeitsch.f. phys. Chemie, 1891, 15. 322. 3 Ibid. 1891, 16. 154. IE SAPONIFICATION OF WAXES 23 or by evaporating the solution and precipitate to dryness and exhaust¬ ing with petroleum ether (cp. chap, vii., “ Unsaponifiable Matter ”). In practice these substances, being insoluble in water and alkalis, ai’e termed “unsaponifiable.” The saponification of some of the waxes, as Chinese wax and especially wool wax, is effected with great difficulty under the conditions stated above for fats and oils. Wool wax must be boiled with an excess of alcoholic potash for at least twenty hours. It is, however, easily saponified by sodium ethoxide, according to Kossel and Obermiiller’s method. Lewkowitsch 1 has shown that equally satis¬ factory results are obtained by saponifying with double normal alcoholic potash under pressure. Henriques is of opinion that in the last-mentioned method action of alkali on the (unsaponifiable) alcohols takes place, whereas by his method of “ cold saponification ” such further action of the alkali is excluded. The proof, however, for this statement is still wanting (cp. footnote 1, p.'21). The difficulty met with in the saponification of waxes is no doubt due to the fact that the soaps formed are less readily soluble than those usually obtained on saponifying fats. [In the case of wool wax Lewkowitsch has proved the formation of soaps that are very sparingly soluble in water.] Such soaps would naturally envelop unsaponified wax, thus protecting it from contact with alkali. Although the theoretical aspect of the saponification process lies beyond the scope of this work, it may be pointed out that V. Meyer’s 2 rule :—Ethers that are formed readily are readily saponifiable, and vice versa —is fully borne out by the facts given in the preceding pages. Thus ethyl stearate is more easily prepared, and also saponified, than glyceryl stearate. 1 Jour. Soc. Chem. Ind. 1892, 137. 2 Berichte, 1895, 1263. CHAPTEE III CONSTITUENTS OF FATS AND WAXES The fats and waxes are resolved into their constituents, viz. into fatty acids and glycerol on the one hand, and into fatty acids and alcohols on the other, by being heated with bases or acids, or by being treated with superheated steam; they are thus hydrolysed or “ saponified.” By means of these saponification processes the follow¬ ing acids and alcohols have been prepared from fats and waxes :— A. Aeids I. Acids of the series C n H 2?i 0 2 . C 2 H 4 0 2 Acetic acicl C 4 H g 0 2 Butyric acid C 5 H 10 O 2 Isovaleric acid C 6 H 12 0 2 Isobutyl acetic acid (Caproic acid) C g H 16 0 2 Caprylic acid CioH 2 o 0 2 Capric acid CnH 22 0 2 Umbellulic acid Ci 2 H 24 0 2 Laurie acid Ci 4 H 28 0 2 Myristic acid C 15 H 30 O 2 Isocetic acid II. Acids of the series C n H 2n _ Oleic C 5 Hg0 2 Tiglic acid Ci 2 H 22 0 2 not named C 14 H 26 0 2 not named C i 6 H 30°2 Hypogaeic acid C 16 H 30 O 2 Physetoleic acid C 1G H 30 O 2 Lycopodic acid 1 *C l7 H 32 0 2 Asellic acid C lg H 34 0 2 Oleic acid Acids of the Acetic Series. C 16 H 32 0 2 Palmitic acid C\ 7 H 34 0, Daturic acid C 18 H 36 0 2 Stearic acid C 20 H 40 O 2 Aracliidic acid C 22 H 44 0 2 Behenic acid C^HrgOg Lignoceric acid C 24 H 48 0 2 Carnaiibic acid C 25 H 50 O 2 Hyaenic acid C 26 H 52 0 2 Cerotic acid C 30 H C0 O 2 Melissic acid 2 0 2 . Acids of the Arcylic or leries. Ci 8 H 34 0 2 Elaidic acid C lg H 34 0 2 Isooleic acid C 18 H 34 0 2 Baltic acid C 19 H 36 0 2 Doeglic acid *C 19 H 36 0 2 Jecoleic acid C 22 H 42 0 2 Erucic acid C 22 H 42 0 2 Brassidic Acid C 22 H 42 0 2 Isoerucic acid 1 Aldepalmitic acid C 16 H 3 0 O 2 (Wanklyn, Jour. Soc. Ghem. Ind. 1891, 212) has not been admitted to the above list on account of its doubtful existence. The existence of the acids marked with an * has been inferred from derivatives of such hypothetical acids. CHAP. Ill ACIDS—ALCOHOLS 25 III. Acids of the series C n H 2W _ 4 0 2 . Acids of the Linolic Series. C i 7 H 30°2 Elaeomargaric acid C 18 H 3 -A Tariric acid Ci 8 H 32 0 2 Linolic acid ■LO Ojj Li C 1 SH 32 O 2 Millet oil acid IV. Acids of the series C^H^i-eCX- Acids of the Linolenic Series. Ci 8 H 3 o0 2 Linolenic acid C lg H 30 O 2 Isolinolenic acid *C ls H 30 O 2 Jecoric acid V. Acids of the series C n H 2n _ 8 0 2 . C 14 H 20 O 2 Isanic acid | *C 17 H 2 ( 3 0 2 Therapic acid VI. Acids of the series C n H 2n 0 3 . Hydroxylated Acids. Ci 6 H 32 0 3 Lanopalmic acid C 21 H 4 20 3 not named C 31 H (j 2 0 3 Cocceric acid VII. Acids of the series C n H 2 ji-20 3 Acids of the Ricinoleic Series. Ci 8 H 34 0 3 Ricinoleic acid Ci S H 34 0 3 Ricinisoleic acid VIII. Acids of the series C n H 2)l 0 4 . Dihydroxylated Acids. C 18 H 36 0 4 Diliydroxystearic acid | C 30 H 60 O 4 Lanoceric acid B. Alcohols I. Alcohols of the series C n H„ ?l+ „0. Ci 6 H 34 0 Cetyl alcohol (Ethal) CjgHggO Octodecyl alcohol C 24 H 50 O Carnaiibyl alcohol C 24 H 50 O or C 25 H 52 0 not named Alcohols of the Ethane Series. C 26 H 54 0 Ceryl alcohol C 27 H 56 0 Isoceryl alcohol C 3 oH G 2 0 Myricyl (Melissyl) alcohol II. Alcohols of the series C n H 2M 0. Alcohols of the Allylic Series. Ci 2 H 24 0 Lanolin alcohol Ci 5 H 30 O not named C 33 H );(i O Psyllostearyl alcohol III. Alcohols of the series C n H 2W+2 0 2 . Alcohols of the Glycolic Series. ^ 25 ^ 52^2 110 ^ named | C 30 H 62 O 2 Cocceryl alcohol 26 CONSTITUENTS OF FATS AND WAXES CHAP. IV. Alcohols of the series C n H 2n+2 0 3 . C.,H s O ;s Glycerol V. Alcohols of the Aromatic Series. C 20 H 44 O Cholesterol C 26 H 44 0 Isocholesterol A. ACIDS Occurrence of Fatty Acids The fatty acids enumerated above by no means occur in the fats in anything approaching equal quantities. Those fatty acids which contain an uneven number of carbon atoms (isovaleric, umbellulic, isocetic, daturic, hysenic, tiglic acid, etc.) are of comparatively rare occurrence and mostly confined to some one individual fat. Indeed, some of those enumerated will not, perhaps, bear the light of modern investigation with its improved methods of research, and may have to share the fate of medullic, 1 moringic, theobromic, 2 crotonoleic 3 acids, which must be considered as definitely removed from the list of fatty acids. The fatty acids of by far the greater number of fats contain exclusively an even number of carbon atoms. Amongst the latter palmitic, stearic, and oleic acids predominate (in some fats linolic and ricinoleic acids) to such an extent that the chief part of most fats consists of a mixture of the glycerides of these three acids. Glycerides of the lower fatty acids may occur conjointly with them, but in that case they are present in smaller quantities. Therefore a large percentage of a fatty acid other than palmitic, stearic, or oleic acid in a fat may always be looked upon as being character¬ istic of that fat, as will readily be seen from the following short summary :— Acetic acid is found as a glyceride (triacetin) in small quantities in the seeds of the spindle-tree 4 ( Evonymus europteus, L.) Butyric acid occurs as a glyceride (butyrin) in cow butter to the extent of about 6 per cent. Isovaleric acid occurs as a glyceride in porpoise and dolphin oils. Isobutylacetic (Caproic) acid has been proved to form part of butter fat and cocoa nut oil, as the glyceride caproin, in conjunction with the glycerides of caprylic and capric acids (caprylin and caprin). If butyrin, caproin, caprylin, and caprin conjointly exist to the extent of at least 1 to 2 per cent in a fat, that fat will be characterised by these glycerides. Thus, butter fat and cocoa nut oil are specially 1 Berichte, 23. Ref. 493. 2 Ibid. 16. 1103. 3 Jour. Soc. Chem. Ind. 1895, 985. 4 Jahresberichte, 1851, 444. Ill OCCURRENCE OF FATTY ACIDS 27 remarkable for containing 8, and 4 to 5 per cent of those glycerides respectively. Umbellulic acid has been shown to occur as a glyceride in the seeds of the Californian bay-tree ( Umbellularia californica). The glyceride of lauric acid, laurin or laurostearin, is the chief constituent of the tangkallah fat from the Javanese tree Cylicodaphne sebifera, Bl.; it occurs also in large quantities in laurel oil. Myristic acid is found as a glyceride in nutmeg butter, liver fat, and, as a wax, in wool wax, isocetic acid in the seeds of the purging nut (Jatropha curcas, L.); daturic acid in the oil of Datura Stramonium, and perhaps among the solid fatty acids of palm oil; aracliidic acid in arachis (earth nut) oil ; behenic acid in ben (behen) oil; and lignoceric acid in arachis oil. Carnaubic acid occurs in carnauba wax, and in wool wax; cerotic and melissic acids are found in the free state in beeswax, and the former, as ceryl cerotate, also in Chinese wax and most likely also in wool wax. Hyxnic acid has been detected in the glandular pouches of the striped hysena, occurring there as a glyceride. Of the rarer acids belonging to the oleic series the following occur as glycerides; tiglic (or angelic) acid in croton oil, and, passing over the two unnamed acids C 12 H 22 0 2 and C 14 H 26 0 2 which have been found in the fat of cochineal, physetoleic acid in sperm oil, doeglic acid in Arctic sperm (bottlenose) oil, and erucic and rapic acids in rape oil. Whilst elxomargaric acid has been found hitherto as a glyceride in the seeds of Elseococca vernicia only, large quantities of the glyceride of linolic acid are characteristic of the so-called drying oils, and it is generally associated with the glycerides of linolenic and isolinolenic acids. Tariric acid has been recently found as a glyceride in the seeds of a Guatemalan shrub, Picramnia. Of the acids of the series C w H m _ 8 0 2 — isanic acid—too little is known as yet. The hydroxylated acids lanopcdmic acid, the acid C 21 H 42 0 3 , and cocceric acid, are constituents of wool wax, carnauba wax, and of the wax of cochineal respectively. Finally, the glycerides of ricinoleic and ricinisoleic acids constitute the principal part of castor oil. The first natural dihydroxylated acid, dihydroxy stearic acid, has been detected in castor oil; another dihydroxylated acid, lanoceric acid, occurs in wool wax. Properties of Fatty Acids Melting Points of Fatty Acids. —The lower members of the acetic acid series, including caprylic acid, and further oleic, rapic, doeglic, linolic, and ricinoleic acids, are liquid at the ordinary temperature, all the others are solid. The following table contains the melting points of the more important acids :— 28 CONSTITUENTS OF FATS AND WAXES CHAP. Acid. Capric Laurie Myristic Palmitic Stearic Arachidic Belienic Lignoceric Carnaubic Cerotic Melissic Tiglic Hypogseic Physetoleic Isooleic Elaidic Erucic Isoerucic Brassidic Elseomargaric Lanopalmic Lanoceric Melting Point. °C. . 31-3 . 43-6 . 53-8 . 62-0 . 71-71-5 . 77-0 . 83-84 . 81-0 . 72-5 . 78-0 . 90-0 . 64-5 ; . 33-0 . 30-0 . 44-45 . 51-52 . 33-34 . 54-56 . 65-0 . 48-5 . 87-88 104-105 The melting point of a mixture of two fatty acids cannot be cal¬ culated from the melting points of the constituents. As a rule, the melting point lies considerably below the calculated one, sometimes even below the melting point of the lowest melting acid. The fol¬ lowing tables will clearly illustrate this fact:— Melting Points of Mixtures of Laurie Acid with Myristic, Palmitic, and Stearic Acid (Ileintz) Laurie Acid. Per cent. Myristic Acid. Palmitic Acid. Stearic Acid. Per cent. Melting Point. Per cent. Melting Point. Per cent. Melting Point. °C. °C. °C. 100 0 43-6 0 43-6 0 43-6 90 10 41-3 10 41-5 10 41-5 80 20 38-5 20 37-1 20 38-5 70 30 35-1 30 38-3 30 43-4 60 40 367 40 40-1 40 50-8 50 50 37-4 50 47-0 50 55-8 40 60 43-0 60 51-2 60 59-0 30 70 46-7 70 54-5 70 62-0 20 80 49-6 80 57-4 80 64-7 10 90 51-8 90 59-8 90 67-0 0 100 53-8 100 62-0 100 69-2 Ill MELTING POINTS OF MIXTURES OF FATTY ACIDS 29 Melting Points of Mixtures of Myristic Acid with Palmitic and Stearic Acid ( Heintz) Myristic Acid. Palmitic Acid. Stearic Acid. Per cent. Per cent. Melting Point. Per cent. Melting Point. 100 0 °C. 53-8 0 °C. 53-8 90 10 51-8 10 51-7 80 20 49-5 20 47-8 70 30 46-2 30 48-2 60 40 47-0 40 50-4 50 50 47'8 50 54-5 40 60 51-5 60 59-8 30 70 54-9 70 62-8 20 80 58-0 80 65-0 10 90 601 90 671 0 100 62-0 100 69’2 Melting Points of Mixtures of Palmitic Acid with Stearic Acid Palmitic Acid. Stearic Acid. Melting Point. Per cent. Per cent. Heintz. Hehner and Mitchell. 100 0 °C. 62-0 °C. 61-8 90 10 601 59-0 80 20 57-5 56-5 70 30 551 54-2 67-5 32-5 55-2 54-5 60 40 56-3 55-5 50 50 56-6 55-6 40 60 60-3 59-4 30 70 62-9 61-5 20 80 65-3 64-2 10 90 67'2 66-5 0 100 69'2 68 -5 1 Melting Points of Mixtures of Palmitic and Cerotic Acids ( Lewkowitsch) Palmitic Acid. Per cent. Cerotic Acid. Per cent. Melting Point. °C. 100 0 60-0 90 10 56'0 85 15 56-5 75 25 60'5 60 40 65-5 50 50 68-6 40 60 70-0 0 100 78-5 1 The different melting point of the stearic acid used by these observers will satis¬ factorily explain the discrepancies ; pure stearic acid melts, however, at 71° to 71 "5° C. 30 CONSTITUENTS OF FATS AND WAXES CHAP. Boiling Points of Fatty Acids. —Of the more frequently occurring fatty acids only the following can be distilled under ordinary pressure without undergoing decomposition :— Acid. Butyric Isobutylacetic Caprylic Capric Boiling Point. °C. . 162-3 about 200 . 236 . 268-270 All the others, when distilled at ordinary pressure, undergo partial decomposition, and amongst the products of the destructive distillation hydrocarbons of the ethane series are found, a fact which forms the main chemical argument in favour of Hofer-Angler’s theory of the formation of petroleum from the fats of marine animals. Under diminished pressure, however, and also by the use of super¬ heated steam, many fatty acids may be distilled without suffering decomposition. In practice, the latter method is largely used for the preparation of the distilled fatty acids. More recently the two methods have been combined. At a pressure of 100 mm., 15 mm., and in vacuo, the following boiling points have been found :— Acid. Boiling Point at 100 mm. Pressure. °C. Boiling Point at 15 mm. 1 Pressure. °C. Boiling Point in vacuo A °0. Lauric . 225 176 102 Myristic . . 250-5 196-5 121-122 Palmitic . 271-5 215 138-139 Stearic . 291 232-5 154-5-155-5 Hypogaeic 2 236 Oleic . . . 285-5 232-5 153 Elai'dic . 287-8-288 234 154 Erucic . . 264 179 Brassidic . . 265 180 The fatty acids boiling at ordinary pressure without undergoing destructive distillation are called volatile fatty acids, in contradistinction to the non-volatile acids. Solubility of Fatty Acids. —The lowest members of the acetic series are miscible with water in every proportion ; isobutylacetic acid is soluble in water, but no longer miscible with it. The solubility in water decreases rapidly with the increase of the number of carbon atoms in the molecule. Caprylic acid requires for its solution 400 parts of boiling water; on cooling, the acid separates out nearly completely. Capric and lauric acids are very slightly soluble in boiling water; the higher acids are altogether insoluble in water. Taking the solubility as a basis for classification, we may subdivide 1 Krafft and Weilandt, Berichte, 1896 (29), 1324. 2 Bodenstein, ibid. 1894, 3399. Ill BEHAVIOUR OF FATTY ACIDS WITH INDICATORS 31 the fatty acids for analytical purposes into soluble and insoluble fatty acids. The acids up to capric acid are called soluble fatty acids; the higher fatty acids from myristic acid upwards are the insoluble fatty acids. Laurie acid has an intermediate position between the soluble and the insoluble acids. On distilling aqueous solutions of the volatile fatty acids, especially if care be taken to replace the water as it boils away, the whole amount of acid present can be obtained in the distillate; the higher the boiling point of a fatty acid the easier is this process carried out. ' Therefore, from a mixture of butyric and isobutylacetic acids dis¬ solved in water the latter acid will pass over first (cp. chap. vi. p. 139). All the fatty acids without exception are soluble in hot alcohol. Action of Solutions of Fatty Acids on Indicators. —In the commercial analysis of fats the fatty acids are frequently estimated by titration with alkalis, and it is therefore important to know their behaviour towards the indicators used in volumetric analysis. From the large number of indicators which have been proposed from time to time, we select for the analysis of fats and its com¬ ponents methylorange and phenolphthalein, which, in conjunction with tincture of litmus (the place of which has lately been taken by laemoid), will be found quite sufficient for all analyses. Methylorange 1 is prepared from diazobenzene sulphonic acid C 6 H 4 ~ gQ - and dimethylaniline. It is the ammonium salt of dimethylaniline-azobenzenesulphonic acid, the constitution of which is expressed by the formula— f, H — so 3 nh 4 C 6 m 4_ n = n _c 6 H 4 N(CH 3 ) 2 . Methylorange dissolves in water to a yellow liquor, which on the addition of a strong acid turns crimson, appearing yellowish-red in deep layers, a salt being formed with the acid. If hydrochloric acid has been used the following salt is obtained— H -S0 3 H _ H = N - C 6 H 4 N(CH 3 ) 2 . HC1. The change from the yellowish colour of the neutral solution to the red is especially sharp in very dilute solutions. Weak acids, as carbonic acid, do not change the colour; therefore, it is possible to titrate carbonates, using methylorange as an indicator, without requiring to drive off the liberated carbonic anhydride by boiling. The acid carbonates of the alkalis are alkaline to methylorange (difference from phenolphthalein). This indicator is specially suitable for the estimation of mineral acids. 1 According to Lunge, tropaeolin 00 or 000 is often sold as methylorange. I have occasionally met with methylorange having such strong alkaline reaction, that four drops of a Y j- per cent solution required 0T c.c. of normal acid for neutralisation. Methylorange should, therefore, always he examined before use. 32 CONSTITUENTS OF FATS AND WAXES CHAP. An excess of the soluble fatty acids also reddens a solution of methylorange, but on titrating with normal alkali the end-reaction is not sharp, and the red colour has disappeared when considerable quantities of free fatty acids are still in the solution; therefore methylorange cannot be used in this case. The insoluble fatty acids, however, as stearic or oleic, do not affect this indicator at all in their alcoholic solution, nor do they act on it when shaken in the liquid state with an aqueous solution of methylorange. It is, therefore, possible to titrate mineral acids in presence of higher fatty acids by using this indicator, and it offers the further advantage, that it can be employed along with another indicator. Thus the mineral acid may be estimated first, using methylorange as the indicator, and subsequently phenolphthalein having been added, the higher fatty acids may be titrated. The solution of the indicator is prepared by dissolving 1 grm. in 1000 c.c. of water. Four drops of this solution are sufficient for every 100 c.c. of the liquid to be titrated. Phenolphthalein .—This is prepared by heating to 115°-120° C., for ten to twelve hours, a solution of 250 grms. of phthalic anhydride — CO\ C 6 H 4 _ in 200 grms. of concentrated sulphuric acid, with 500 grms. of phenol C 6 H 5 . OH. The hot melt is poured into boiling water, and washed with boiling water until the odour of phenol has disappeared. The residue is of sufficient purity to be at once used as an indicator. The chemical constitution of phenolphthalein is expressed by the formula— /C 6 H 4 . OH Cf-C 6 H 4 . OH \C 6 H 4 . CO To prepare the solution required for volumetric analysis 1 grm. is dissolved in 100 c.c. of 95 per cent alcohol. Two drops of this indicator will be found sufficient for every 100 c.c. of solution. The alcoholic solution of phenolphthalein is yellowish, and turns pink on the addition of the slightest quantity of a fixed alkali owing to the formation of a salt. These salts are decomposed completely even by weak acids, therefore the insoluble fatty acids may be titrated in their alcoholic solutions by means of this indicator. Ammonia does not affect phenolphthalein in alcoholic solution, and for this reason is unsuitable for the titration of fatty acids. Phenolphthalein may also be used for the titration of the soluble fatty acids in the same way as litmus, which is, however, preferred by some chemists. Due regard should be paid to the sensitiveness of phenolphthalein to carbon dioxide, and to the fact that the acid carbonates of the alkalis do not affect phenolphthalein; it is therefore absolutely necessary to remove the carbonic dioxide by boiling. When standard- Ill VISCOSITY OF FATTY ACIDS—SOAPS 33 ising acids and alkalis with the aid of phenolphthalein- this possible source of error should especially be guarded against. Litmus. —Tincture of litmus may be used in the analysis of fats for titrating the volatile fatty acids, mineral acids, caustic alkalis, carbonates, etc. The statement made by Rechenberg, 1 that the salts formed by the union of volatile fatty acids with alkalis and alkaline earths — especially those of butyric acid—show in their aqueous solution strongly alkaline reaction, has not been confirmed by the author’s experience. It is quite possible to titrate butyric acid, using litmus as an indicator. The change is rather gradual, but perfectly distinct. Lacmoid.' 2 —This colouring matter is prepared by heating 100 parts of resorcinol, 5 parts of sodium nitrate, and 5 parts of distilled water in an oil bath to 110° C. The melt is dissolved in water and precipitated by salting out. Its chemical constitution is unknown. Thomson 3 found that it can be used for the titration of fixed alkalis, ammonia, alkaline earths, and mineral acids. It is, however, useless for the titration of fatty acids, as their neutral salts themselves produce the blue colour. Viscosity of Fatty Acids. —Since viscosimetric methods have been proposed for the examination of fats and oils, it may be found useful to record here the following viscosimetric constants. From the values given in the table it is evident that the viscosity increases with the molecular weight. Viscosimetric Constants of Fatty Acids (Pribram and Handl). Fatty Acid. Molecular Weight. Specific Viscosity at 10“ C. 30° C. 50° C. Propionic 74 70-3 51-5 49-9 Butyric . 88 110-2 77-4 57-6 Valerianic . 102 152-4 103-3 71-5 Capronic 116 222-2 139-7 97-8 With regard to other physical constants Guillot’s 4 pamphlet should be consulted. Salts of Fatty Acids. —The metallic salts of the non-volatile acids are called SOAPS. In common parlance, however, we understand under the term “ soap ” the alkali salts of the non-volatile acids. Salts of the Alkali-Metals The normal salts of the saturated acids have the general formula C n H 2W+1 CO . OM, where M stands for Na or K. In alcoholic solution 1 Jnur.prakt. Cthemie, 1884, 519. 2 Jour. Soc. Cheni. Ind. 1884, 296. 3 Chen. News, 52. 18, 29. 4 A. Guillot, Proprietes Physiques des Acides de la Serie Grasse. Paris, Bailliere et fils, 1895. D 34 CONSTITUENTS OF FATS AND WAXES CHAP. these salts are neutral to phenolphthalein. There are also in exist¬ ence acid salts of the formula C n H 2J1+1 CO.OM, C n H 3n 0 2 ; dissolved in hot alcohol they show acid reaction to phenolphthalein. The alkali-salts of the fatty acids are remarkable in their behaviour to water. The salts of the lowest members of the series are easily soluble in water. Thus the alkali salts of butyric acid are deliquescent, and those of capric acid are still very easily soluble in water at the ordinary temperature. But the solubility in water decreases as the molecular weight of the fatty acids increases; thus the alkali salts of palmitic or stearic acid are no longer soluble in cold water. They dissolve, however, when boiled with not too large a quantity of water, to a clear solution, which solidifies, on cooling, to a mucilaginous mass, representing the normal salts of the fatty acids, or at any rate approximately so. On diluting the clear hot solutions with water they become turbid, and, on shaking, a lather is produced which persists for some time. The turbidity is due to the dissociation of the normal salt into caustic alkali and free fatty acid. This dissociation, termed hydrolysis of soap, is a very gradual one, depending on the amount of water present and also on the temperature. The free alkali remains in solution, and the free fatty acid com¬ bining with non-hydrolysed salt separates, forming an acid salt, he. a salt containing more than one equivalent of acid for one equivalent of alkali, presumably in association with some undissociated salt. Chevreul, who first studied this question, found that a solution of one part of neutral potassium stearate, C 18 H 35 0 . K, in 20 parts of boiling water, treated with additional 1000 parts of boiling water yields, on cooling, an acid salt of the composition C 18 H 35 0 2 K. C 18 H 36 0 2 , potassium bistearate, whilst free alkali and an infinitesimal quantity of stearic acid remain in solution. Similarly, neutral sodium stearate dissolved in 2000 to 3000 parts of boiling water yields, on cooling, an acid salt of the composition C 18 H 35 0 2 Na. C 18 H 36 0 2 , sodium bipalmi- tate. Neutral oleate, however, requires a very large quantity of water and a low temperature to become dissociated • the difference between oleic acid on the one hand, and palmitic and stearic on the other hand, is so marked that an approximate method of separation may be based on this property. The potassium bistearate can be further dissociated by treatment with water into a more acid salt, presumably of the composition of a quadro-stearate. The amount of alkali thus set free under given conditions can be de¬ termined quantitatively by salting out the “curd,” filtering off and wash¬ ing with brine, dissolving the curd in absolute alcohol, and determining the acidity by titration with alkali, using phenolphthalein as indicator. Alder Wright and Thompson 1 derived from a series of observations the results contained in the following table. I have arranged the fatty acids in the order of their molecular weights :— 1 Jour. Soc. Ohem. Ind. 1885, 630. Ill HYDROLYSIS OF SOAP 35 Fatty Acids. Mean Molecular Weight. Hydrolysis brought about by x Molecules of Water. O lO 7\ *=250 £ = 500 * = 1000 *=2000 Crude lauric 195 3-75 4-5 5’4 6-45 7-1 (Cotton seed oil acids . 250 1 2-25 3-0 5-0 7-5 9-5) Nearly pure palmitic . 256 1-45 1-9 2-6 3-15 3-75 (Palm-oil-tallow soap . 271 1-1 1-55 2-6 4-1 5'3) Pure oleic . 282 1-85 2-6 2 3-8 5-2 6-65 Pure stearic 284 07 1-0 1-7 2-6 3-55 | The numbers represent the quantities of Na 2 0 set free by hydro¬ lysis, calculated for 100 parts of Na 2 0 contained in the soap in com¬ bination with fatty acid, x molecules of water being used for one of anhydrous soap. If we look at the numbers given for lauric, palmitic, and stearic acids only, it would appear that the sodium salts of the fatty acids are decomposed with greater ease, the lower their molecular weight. But on the one hand the behaviour of oleic acid does not conform with this rule, and on the other hand Thomsen 2 has shown that sodium acetate is not measurably dissociated by water. (Cp., however, p. 38.) Rotondi 3 explained the action of water on soap in the following- manner : The neutral (commercial) soaps, on being dissolved, are decomposed into basic and acid salts ; the latter are insoluble in cold and only slightly soluble in hot water. The acid salts are not dialysable, and can, therefore, be separated from the former which are readily so. The basic soaps are completely soluble in cold and hot water, and are entirely precipitated by sodium chloride without loss of alkali; their solutions dissolve acid soaps on heating, but become turbid on cooling. These views have been shown by Krafft and Stern 4 to be erroneous. They repeated Chevreul’s experiment with pure sodium palmitate (2 grms.), and obtained the following result:— 1 Part of Sodium Palmitate containing 8-27 per cent Na Boiled with parts Water yielded, on cooling, salt containing Na. Per cent. 200 7-01 300 6-84 400 6-60 450 6-32 500 6-04 900 4-20 1 This appears to be somewhat low. 3 Jour. Soc. Chem. Ind. 1885, 601. 2 Thermochemische Untersuchungen, i. 372. 4 Berichte, 1894, 1747. 36 CONSTITUENTS OF FATS AND WAXES chap. To get an insight into the approximate composition of the separ¬ ated salts the following table may be consulted:— Salts of the Containing Na. formula -Per cent. C 1G H 31 0,Na.8-27 3C 16 H 31 0 2 Na+ C 16 H 3 oO, 2 . . . . 6‘33 C 1G H 31 0 2 Na+ C 16 H 32 0 2 . . . . 4'31 C 1G H 31 0 2 Na + 3C 16 H 32 0 2 .... 2'20 Similar experiments with pure sodium stearate gave the following result:— 1 Part of Sodium Stearate containing 7 '52 per cent Na Boiled with parts Water yielded, on cooling, salt containing Na. Per cent. I. II. 200 6-34 6-27 300 5-81 5-71 Sodium bistearate C 18 H 35 0 2 Na + C 18 H 36 0 2 contains 3'89 per cent Na. From these experiments the conclusion must be drawn that hydrolysis increases with the molecular weight of the fatty acids ; this is in direct opposition to the' conclusions derived from Alder Wright and Thompson's more complete series of observations detailed above (p. 35). As shown above, oleic acid occupies an exceptional position as regards hydrolysis of its salts. This has been confirmed by Krafft and Stern, according to whose observation pure neutral sodium oleate dissolves to a clear solution in about 10 parts of cold water, which does not yield a sensibly turbid solution even on dilution with 900 parts of water, whereas the sodium bioleate, C 18 H 33 0 2 Na + C 18 H 34 0 2 , is immediately dissociated by cold water. In order to hydrolyse oleates by far larger quantities of water are required, at the same time the temperature must be lowered considerably. The solid elaidic acid, however, simulates stearic acid in its behaviour, as the following observations prove :— 1 Part of Sodium Elardate containing 7'56per cent Na Boiled with parts water yielded, on cooling, salt containing Na. Per cent. 300 5-80 1500 3-24 In the light of these experiments, the commercial soaps, consisting of palmitates, stearates, and oleates, would yield, on treatment with large quantities of water, acid palmitates and stearates as precipitates, Ill HYDROLYSIS OF SOAP 37 I whereas free alkali and oleates would remain in solution. The | solution would thus contain soap plus free alkali, a fact which has 1 been taken by Rotondi as a proof for the existence of basic soaps in I solution. Besides, direct experiments made with a view to preparing synthetically basic salts from oleic acid failed completely, and on hydrolysing pure sodium palmitate with 900 parts of water not a trace of palmitic acid could be detected in the cold supernatant solution. The direct proof that free fatty acid and free alkali co-exist in a dilute solution in the hot was given by extracting a solution of not convpletely hydrolysed normal sodium palmitate with toluene, when free palmitic acid was obtained. The hydrolysis of soaps becomes complete according to Krafft and j JViglow, 1 if the one of the two components of the normal salt—say, j fatty acid—is removed, as by shaking out repeatedly with toluene. 2 I It is apparent from the foregoing notes that oleates behave differ¬ ently from the solid fatty acids and even from elaidic acid, with which it is isomeric. This difference, however, disappears if not only the one factor, which has been considered hitherto exclusively, viz. the proportion of water, is taken into account, but if proper regard is had to the temperature. For Krafft and JViglow 1 observed that the temperature at which the separation of acid salts com¬ mences always lies below the melting point of the corresponding fatty acid. The following table reproduces their experiments, in which a one per cent solution of the sodium salt was examined :— Sodium Salt of Temperature of Separation. Melting Point of Acid. Difference. °C. °C. Stearic Acid 60 69-2 9’2 Palmitic ,, 45 62'0 17-0 Myristic ,, 31-5 54 -5 23-0 Laurie ,, 11 43-6 32-6 Elaidic 35 51-0 16-0 Oleic 0 14-0 14-0 From these numbers the following rule has been derived : The temperature of crystallisation of the soaps always lies below the melting point of the free fatty acid, and the difference between both temperatures increases on descending the homologous series. It will thus be seen that oleic acid falls in line with the other acids, and that, e.g., a hot solution of sodium palmitate behaves like a cold solution of sodium oleate. From a series of observations undertaken by Krafft and JViglow 3 with a view to determining the molecular weight of soaps by the 1 Jour. Soc. Chem. lnd. 1896, 206. 2 This observation, however, is not consistent with the fact that free alkali (p. 38) causes a diminution of the amount of hydrolysis, and one would accordingly expect that an equilibrium would be established, so that for the same amount of water no more than a certain quantity, but not the whole quantity, of fatty acid could be extracted. (J. L.) 3 Berichte, 1896, 1329. 38 CONSTITUENTS OF FATS AND WAXES CHAP. ebullioscopic method, it appears that the sodium salts of the lower fatty acids raise the boiling point of water by twice the normal value ; this is explained by assuming that each molecule is hydrolysed into free fatty acid and sodium hydroxide, as indicated by the fol¬ lowing equation :— C 2 H 3 0 2 Na + HoO = C 2 H 4 0 2 + NaOH. Sodium Acetate. The sodium salts of the higher fatty acids, however, do not raise the boiling point of water at all; the solutions solidify on cooling to gelatin¬ ous masses, and thus show the characteristic behaviour of colloids. The observations referred to are reproduced in the following table:— Sodium Salts Parts of Salt Molecular Weight. Formula. in 100 parts of Water. Apparent Mol. W. Normal Mol.W. Acid. Apparent. Normal. Acetic C 2 H 3 0 2 Na f 0-9 1 \ 25-2 f 50-5 40-3 | 82 f \ 0-6 0-5 Propionic C 3 H 5 0 2 Na f 3 -8 \ l 19-8 j 517 46-2 | 96 f l { 0-6 0 - 5 Caproic C 6 H u 0 2 Na f 3*5 ^ V 20-6 / 72-8 77-9 | 138 0-52 0-56 Nonylic C 9 H 17 0.,Na / 3-4 1 l 20-4 j 144T 285-5 } 180 / l 0-8 1-58 Laurie C^HggOgNa f 3-3 \ l 16-1 / 474 507 | 222 { 2-13 2-28 Palmitic C 16 H 31 0 2 Na / 16-4 1 1 25-0 / about 1060 approaching oo | 278 / l about 4 approaching oo Stearic CinHfjgOjNa f abt.16'0 l 27 about 1500 approaching oo | 306 / l about 5 approaching co Oleic C 18 H 33 0 2 Na 26-5 approaching oo 304 approaching cc The numbers given in the last column are a measure of the dis¬ sociation brought about, and they show in a general way that the salts of the lowest fatty acids are hydrolysed in the hot, those of the higher acids already in the cold, whereas laurates occupy an inter¬ mediate position. The hydrolytic action of water is retarded by the addition of free alkali. The following table due to Alder Wright and Thompson, which should be compared with the one given above, p. 35, clearly points out this fact. Hydrolysis brought about by Extra NaoO added to x Molecules of Water. Fatty Acids. solution per 100 as combined soap. *=150 *=250 *=2000 Crude Laurie .... 11-0 1-1 1-6 2-0 Cotton seed oil acids 15-0 nil nil 6-5 Stearic and Oleic (from tallow) 20-0 nil nil nil Ill HYDROLYSIS OF SOAP 39 An equally retarding influence is exercised by alcohol. Absolute alcohol, as also alcohol of 95 to 90 per cent, dissolve neutral soaps without dissociation. If, however, water be added to an alcoholic soap solution, hydrolysis is brought about more or less, according to the quantity of water added. (This is easily demonstrated by adding a drop of phenolphthalein solution.) From concentrated alcoholic solutions the soaps mostly separate on cooling in a jelly-like mass, which, however, becomes crystalline on standing for some time. Also glyeerol causes a diminution of the amount of hydrolysis brought about by water. Presence of salts diminishes the solubility of soaps in water; in sufficiently concentrated solutions of common salt, sodium sulphate, also caustic alkalis, soaps are insoluble, they are therefore thrown out of their aqueous solutions by adding salt, etc. ( soap-making ). The laurates and ricinoleates are remarkable for the large quantity of salt required to throw them out of their solutions, or, as the term goes, for “ salting out.” The commercial soaps, containing potash as alkali, constitute the “soft soaps,” those containing soda the “hard.” The affinities of fatty acids, such as occur ordinarily in most glycerides, to caustic soda and potash are sensibly the same ; so that if a mixture of caustic soda and potash be brought into contact with fatty acids, insufficient in quantity to neutralise the total alkali present, a mixture of soda and potash soaps results with excess of the caustic alkalis, the ratio between free caustic soda and potash being approximately the same as that of the combined alkalis. The following table, due to Alder Wright and Thompson, 1 expresses this clearly ; in each experiment for a given amount of fatty acid two equivalents of alkali, one of caustic soda and one of caustic potash, were present: Fatty Acid. Percentage of Total Fatty Acid converted into Soda Soap. Potash Soap. Pure Stearic ..... 51-2 48'8 Pure Oleic ....•• 50'8 49‘2 Crude Stearic and Oleic (tallow) Crude Stearic Palmitic and Oleic 51-5 48'5 (palm oil and tallow) 48-2 51*8 Crude Laurie (cocoa nut oil) 49'7 50 3 Mean 50-3 497 Practically, in every case half the caustic alkali was present as soap and the other half as uncombined hydroxide (cp. also chap. n. p. 19). The logical postulate, that a soda soap on treatment with as 1 Jour. Soc. Cliem. Ind. 1885, 626. 40 CONSTITUENTS OF FATS AND WAXES CHAP. much caustic potash as is equivalent to the soda present, and con¬ versely, a potash soap with the equivalent of caustic soda, should yield a soap containing half the fatty acid in combination with potash and the other half combined with soda, is thus borne out by experi¬ ments. The carbonates of soda and potash behave in a very different manner. Experiments carried out in a similar fashion to those described in the case of the caustic alkali proved that the prevailing tendency is towards the formation of potash soap and sodium carbonate, whether potassium carbonate was intermixed with soda soap in equivalent proportions of the basis, or sodium carbonate was intermixed with potash soap; in the latter case, even if the quantity of sodium carbonate was largely in excess of the amount equivalent to the potash present, only a comparatively small pro¬ portion of soda soap was formed. The following table, due to the same authors, gives the actual figures obtained :— Fatty Acid. Soda Soap fused with C0 3 K 2 . Percentage of total Fatty Acids present. Potash Soaps fused with C0 3 Na 2 . Percentage of total Fatty Acids present. Equivalent to the C0 3 K 3 added. Actually con¬ verted into Potash Soap. Equivalent to the CCqNao added. Actually converted into Soda Soap. Stearic and Oleic (tallow) . 10-4 8-0 3 3 3 3 45-7 34-4 3 3 3 3 ioo-o 97-95 ioo-o 4-3 104-2 99-00 1000 15-0 Stearic, Palmitic, and Oleic (palm oil and tallow) 57-2 52-1 Stearic, Palmitic, and Oleic (palm oil and tallow) 108-0 90-8 177-0 9-5 Crude Laurie (Cocoa nut oil) 52-8 46-4 Crude Ricinoleic acid (Castor oil) 114-8 87-9 197-0 6-2 50-0 48-4 ” ioo-o 93-8 205-0 8-2 The chlorides of the alkalis behave in the opposite manner to the carbonates • the prevailing tendency being towards the formation of soda soap and potassium chloride; at any rate, these salts are formed in preference to potash soap and sodium chloride when the relative masses of the two alkalis are nearly equal. (Old method of making hard soap from wood ashes.) On repeating the same operation, the exchange of the metals may become a complete one. The results obtained by Alder Wright and Thompson in experiments when using 10 molecules of KC1 and 10 molecules of NaCl for 1 molecule of soap consisting of one-half molecule of potash soap and one-half molecule of soda soap are reproduced in the following table :— Ill METALLIC SOAPS 41 Fatty Acid. Percentage of Fatty Acid contained Molecular Ratio of Soda Soap to Potash Soap. As Potash Soap. As Soda Soap. Pure Oleic .... Crude Ricinoleic (from castor 38'0 62-0 1-63 :1 oil) ..... Stearic, Oleic, and Resin (from 17-8 82-2 4-6:1 tallow-resin soap) Crude Laurie Acid (from 17-2 82-8 4-8 :1 cocoa nut oil soap) . 15-1 85-9 5 7:1 By modifying, however, the relative masses, potash soap and sodium chloride can be produced. The experimental proof is given by the figures in the following table, where in the case of columns (. water, but dissolves in it in the presence of very little alcohol on boiling, and separates on cooling as a white crystalline magma. The usual organic solvents dissolve it readily. Treated with aqueous alkalis it does not pass into solution, but on adding a little alcohol and heating, the alkali salts are readily formed. The alkali salts exist in aqueous solution only in the hot, but on cooling they are dissociated into acid salts, which separate, and free alkali. The magnesium salt is insoluble in hot alcohol; the calcium salt dissolves easily in boiling absolute alcohol, but sparingly in 95 per¬ cent alcohol. An acid of the formula C 21 H 42 0 3 occurs, combined with alcohols, in carnauba wax. 1 The free acid does not appear to exist, the inner anhydride, or lactone, of the acid being precipitated, whenever the latter itself might be expected. Cocceric Acid, C 31 H 62 0 3 Cocceric acid occurs in the wax of cochineal 2 combined with cocceryl alcohol. The acid forms a crystalline potvder (from alcohol), melting point 92°-93° C., and dissolves sparingly in cold alcohol, ether, benzene, petroleum ether, and glacial acetic acid. VII.—Acids of the Ricinoleic Series. Hydroxylated Acids, C n H 2M _ 2 0 3 Ricinoleic Acid, C 18 H 34 0 3 = CH 3 - (OH,), - CH. OH - CH 2 - CH = ' CH - (CH 2 ) 7 - C0 2 H 3 (Ricinisoleic Acid, C 18 H 34 0 3 ; Ricinelaidic Acid, C 18 H 34 0 3 ; Ricinic Acid, C 18 H 34 0 3 ) Ricinoleic acid occurs combined with glycerol in large quantities in castor oil. The crude ricinoleic acid obtained by saponifying castor oil and decomposing the soap by means of a mineral acid is at the ordinary temperature a thick oil of specific gravity 0-9509 at 15-5° C. On cooling to - 6° to - 10° C. the acid solidifies completely, and is miscible with alcohol and ether in every proportion. Krafft 4 has obtained from the crude acid, by cooling to 0° and gradually pressing at temperatures not exceeding 12° C., a white, odourless, hard, crystalline mass melting at 16°-17° C., which he considers to be the pure acid. The melted acid solidifies easily when cooled considerably below the melting point. The acid cannot be distilled without under¬ going decomposition, 5 even under a pressure of only 15 mm. The 1 Jour. Soc. Chem. Ind. 1884, 448. 2 Ibid. 1885, 585. 3 Goldsobel, Bericlite, 1894, 3121. 4 Jour. Soc. Chem. Ind. 1888, 755. 5 An acid of the formula C 18 H 32 0 2 being formed (Mangold, Bericlite , 1894, Ref. 629). Ill RICINOLEIC ACID 65 pure triglyceride of ricinoleic acid is solid, whilst castor oil is fluid at the ordinary temperature (cp. Castor Oil, chap. xi. p. 421). Accord¬ ing to Juillard , 1 however, the acid so prepared is not pure, as it still contains stearic and (natural) dihydroxystearic acids. The pure acid is best obtained from its barium salt after repeated crystallisation of the latter from alcohol. The pure acid melts at 4 °- 5 ° C. Ricinoleic acid assimilates two atoms of bromine or iodine, but does not absorb hydrogen. Nitrous acid transforms it into its stereometrical isomeride, ricinelaidic acid. On exposure to the atmosphere ricinoleic acid does not absorb oxygen. By reducing agents it is converted into stearic acid. According to H. Meyer 2 ricinoleic acid becomes polymerised on standing, forming polyricinoleic acids, easily convertible into ricinoleic acid on boiling with alcoholic potash. Most of the metallic salts are obtained in the crystalline state; they behave with solvents very much like the corre¬ sponding salts of oleic acid. The calcium and barium ricinoleates are soluble in alcohol; the lead ricinoleate is easily soluble in ether, and melts at 100 ° C. By the action of concentrated sulphuric acid on ricinoleic acid the following products are obtained : 3 — ricinoleo - sulphuric acid, OH. S0 2 .0 . C 17 H 32 . COOH, OH <40 O dihydroxy stearo-sulpliuric acid, ' v,„>C 1 .H,„. COOH Uxi 17 dibasic diricinoleic acid, 0<^ 17 -H -32 * OOOll monobasic diricinoleic acid, OH . C l 7 H 32 COO . C 17 H 32 . COOH, dihydroxy¬ stearic acid, C 1 S H 36 0 4 , a solid acid, C 36 H 70 O 7 , and isoricinoleic acid, C 18 H 34 0 3 (cp. Turkey-red Oils, p. 727). On oxidising ricinoleic acid with potassium permanganate two atoms of oxygen are assimilated. Hazura and Griissner 4 found that two isomeric trihydroxystearic acids were formed by this process, and concluded, therefore, that the liquid fatty acid of castor oil is a mixture of two isomerides, ricinoleic and ricinisoleic acids. Mangold , 5 however, points out that this conclusion need not be necessarily adopted, as two stereochemical isomerides may be obtained from one and the same ricinoleic acid . 3 Rieinela'idie acid is produced from ricinoleic acid by the action of nitrous acid. It crystallises in needles, melting point 52°-53° C. The acid absorbs two atoms of bromine. Oxidised by potassium permanganate ricinelaidic acid yields two isomeric (most likely stereometric) trihydroxylated acids (Mangold). 1 Joiir. Ohevi. Soc. 1895, Abstr. i. 500. 2 Jour. Soc. Chevi. Ind. 1897, 684. 3 Ihid - 1894, 820. An isoricinoleic acid has been described by Juillard ; this acid appears to be a ketonic acid, and is a by-product formed by the action of sulphuric acid on ricinoleic acid ; it is distinguished from ricinoleic acid by its solubility in petroleum ether. 4 Jour. Soc. Cthem. Ind. 1888, 681. 5 Jour. Chem. Soc. 1893, Abstracts, 1304. F 66 CONSTITUENTS OF FATS AND WAXES CHAP. Rieinie acid has been obtained by Krafft on heating barium ricin- oleate in a vacuum, when the barium salt of ricinic acid remains in the retort. The acid forms glistening laminae (from alcohol), melting point 81° C. It boils under 15 mm. pressure with very slight decomposition. The existence of this acid points again to the possible existence of two ricinoleic acids, which, however, need not be chemical isomerides, but may represent stereometric isomerides, ricinoleic acid possessing one so-called asymmetric carbon atom, and therefore possibly forming dextro- and laevo-rotatory acids. In fact, Walden 1 has shown since that both ricinoleic and ricinelaidic acids are optically active, whereas ricinic acid is inactive. The two active acids are dextro-rotatory, their laevo-rotatory isomerides being unknown yet. VIII.— Acids of the Series C n H 2n 0 4 , Dihydroxylated Acids Dihydroxystearic Acid, C 1s H 36 0 4 This natural dihydroxylated acid occurs, according to Juillard, 2 in castor oil to the extent of about 1 per cent, and is prepared from crude ricinoleic acid by keeping the latter at a temperature below 12 ° C. The crystalline magma is drained, pressed, and recrystallised from alcohol, and thus yields a mixture of dihydroxystearic and stearic acids. The latter is removed by washing with hot toluene, and the remaining crude dihydroxystearic acid is recrystallised from boiling alcohol. The pure acid melts at 140°-143° C. It is insoluble in ether, petroleum ether, and benzene, slightly soluble in cold toluene, more so in the hot solvents ; it dissolves in boiling alcohol and boiling- acetic acid. By reducing agents the acid is easily converted into stearic acid ; by hydrochloric acid at 180° C., and subsequent treatment with caustic potash, this dihydroxystearic acid is changed into the dibasic acid COOH . (HO)C 17 H 33 .0 . O l7 H 33 (OH)COOH. It is possible that this acid—being a natural product—is optically active. Lanoceric Acid, C 30 H 60 O 4 Lanoceric acid has been isolated from the mixture of soaps obtained by saponifying wool wax with alcoholic potash. 3 The acid crystallises from alcohol in microscopic laminae ; it softens at 102° C. and melts at 104°-105° C.; it then solidifies at 103°- 101°, and melts again at the same temperature as before. It has, however, lost one molecule of water, probably from the two hydroxyl 1 Berichte, 1894, 3472. 2 Jour. Soc. Chem. Ind. 1895, 811. 3 Darmstaedter and Lifschiitz, Berichte., 1896, 1474, 2893 ; Jour. Soc. Chem. Ind. 1896, 548. (The acid is described there as lanocerinic acid.) Ill HYDROXYLATED ACIDS 67 groups, for it still has acid properties. The acid very readily forms a lactone, e.g. when boiled with dilute hydrochloric acid; the lactone melts at 86° C. Lanoceric acid is almost insoluble in cold water and alcohol, but readily soluble in hot alcohol. It does not combine readily with aqueous potash ; a little alcohol, however, easily induces combination ; the salt is therefore best prepared in alcoholic solution. The potas¬ sium salt behaves exactly like that of lanopalmic acid (p. 63), viz. it dissociates on cooling into the acid salt, which separates, and into free alkali. APPENDIX TO THE FATTY ACIDS The acids already mentioned occur in natural fats and waxes. Besides these, however, several saturated hyclroxylated acids or their inner anhydrides are found in various products of the fat industry. These we describe below, along with some other hydroxylated fatty acids, which are of great importance for the identification of glycerides of unsaturated acids. As the outcome of their own and Saytzeff’s researches, the follow¬ ing general law has been stated by Hazura and Griissner. 1 All unsaturated fatty acids, when oxidised with potassium permanganate in alkaline solution, have as many hydroxyl groups added as the fatty acids contain unsaturated valencies, yielding thereby saturated hydroxylated acids which contain the same number of carbon atoms in the molecule. The following table shows the hydroxylated acids obtained hitherto by this reaction :— Fatty Acid. Hydroxylated Acid. Tiglic acid..... (Dihydroxytiglic) Tigliceric acid (Unknown) .... Diliydroxyasellic acid Oleic acid ..... Dihydroxystearic acid Elai'dic acid .... Dihydroxystearidic acid Isooleic acid .... Para-dihydroxystearic acid (Unknown) .... Dihydroxyjecoleic acid Ricinoleic acid .... /Trihydroxystearic acid l a-Isotrihydroxystearic acid Ricinelaidic acid f /3-Isotrihydroxystearic acid l y-Isotriliydroxystearic acid Linolic acid ..... Tetrahydroxystearic (sativic) acid Linolenic acid .... Hexahydroxystearic (linusic) acid Isolinolenic acid (?) . Isolinusic acid Erucic acid .... Diliydroxybelienic acid Brassidic acid .... Isodihydroxybehenic acid Isoerucic acid .... Para-dihydroxybehenic acid 1 Jour. Soc. Chem. Ind. 1888, 506. 68 CONSTITUENTS OF FATS AND WAXES CHAP. A dihydroxy palmitic acid has also been prepared starting from the dibromo-addition product of hypogseic acid. But it cannot be doubted that the dihydroxypalmitic acid could be prepared by oxidis¬ ing hypogseic acid itself with potassium permanganate. The oxidation of the unsaturated acids is carried out as follows :— 30 grms. of the acids are neutralised by 36 c.c. of caustic potash, specific gravity 1-27, and the resulting soap is dissolved in 2000 c.c. of water. Into this solution are run gradually, with shaking or stirring, 2000 c.c. of a 1'5 per cent solution of potassium permanganate. After a short time as much sulphurous acid is added as will reduce the excess of permanganate and dissolve the separated hydrated manganese peroxide. The hydroxylated fatty acids separate out almost entirely, being mostly insoluble in water (see p. 69). During the reaction, perhaps owing to the further oxidation of the hydroxylated acids, dibasic acids are also formed; for this reason we shall briefly describe those dibasic acids that have been found amongst the products of oxidation, and are likely to be met with in similar researches. In the case of cod liver oil fatty acids, Heyerdahl found that under the conditions just laid dotvn oxidation proceeds too far, 2 grms. only of hydroxylated acids having been obtained from 50 grms. of crude acids. Good results, however, were obtained when the oxidation was carried out with half-saturated solution at the temperature of the freezing point. For the oxidation of higher unsaturated fatty acids, such as erucic and brassidic acids, a large excess of caustic potash must be used. I.—Hydroxylated Acids 1. Monohydroxylated Acids p- Hydroxystearic Acid, C 1 s H 36 0 3 = C 18 H 35 0 2 (0H) This acid is formed on dissolving ordinary oleic acid in concen¬ trated sulphuric acid, along with sulphostearic acid and stearolactone (see 1 urkey-red Oils). The glyceride of the same acid is obtained on subjecting triolein, the glyceride of oleic acid, to the same operation. /3-hydroxystearic acid crystallises in hexagonal plates (from alcohol), melting at 81°-8D5 0 ( Geitel ), 83°-85° C. ( Saytzeff ). 100 parts of absolute alcohol dissolve 8‘78 parts of the acid at 20° C.; at the same temperature 100 parts of ether dissolve 2-3 parts of the acid. On heating the acid to 200° C. with or without zinc chloride, a viscous mass is obtained containing the anhydride C 18 H 34 0 0 and also oleic acid. 1 The hydroxystearic acid is regenerated by boiling the anhydride with caustic potash. 1 It may be pointed out here that the anhydride CjgH^Oo, being a saturated com¬ pound, does not absorb iodine ; therefore the oleic acid can be determined quantitatively in the mixture (cp. chap. vi. p. 197). Ill HYDROXYSTEARIC ACIDS 69 On distilling /3-hydroxystearic acid in a vacuum, a portion of the acid passes over unchanged along with oleic and isooleic acids. The sodium, zinc, and copper salts are soluble in alcohol; the barium salt is insoluble both in alcohol and ether. a-HYDROXYSTEARIC ACID, C 18 H 36 0 3 = C 18 H 35 0 2 (0H) On treating isooleic acid with sulphuric acid in the manner already described for ordinary oleic acid, this isomeride of /3-hydroxystearic acid is obtained, together with /3-hydroxystearic acid in varying pro¬ portions, depending on the temperature during the interaction. The lower the temperature the larger is the yield of a-hydroxystearic acid, a-hydroxystearic acid is also formed on digesting with silver hydroxide the iodo-stearic acid obtained from isooleic acid and hydriodic acid. This hydroxystearic acid distils undecomposed under a pressure of 100 mm. (difference from /3-hydroxystearic acid), and crystallises (from alcohol) in plates, melting point 77°-79° C. It is more easily soluble in ether than the /3 isomeride, whilst less readily soluble in absolute alcohol; 100 parts of the latter dissolve at 20° C. only 0'58 parts of the acid. (y-HYDROXYSTEARIC ACID, C 1S H 36 0 3 = C 18 H 35 0. 2 (0H)) Stearolactone, C 18 H 34 0 2 The free acid has not been prepared yet, its inner anhydride, or lactone, being formed whenever the free acid might be expected. This lactone is obtained when concentrated sulphuric acid acts on ordinary oleic acid 1 (see /3-hydroxystearic acid). Larger quantities are obtained by heating oleic acid with 10 per cent of zinc chloride to 185° C. (, Schmidt’s process, cp. chap. xii. p. 747). Stearolactone forms fine white crystalline laminae, having the melting point 47°-48° C.; it can be distilled almost unchanged. Insoluble in water, it dissolves easily in alcohol, ether, and petroleum ether. Boiling alkalis dissolve the stearolactone with formation of metallic salts of the y-hydroxystearic acid. On adding a mineral acid to the solution of any of the salts, not the acid, as might be expected, but stearolactone is precipitated. 2. Dihydroxylated Acids (Dihydroxytiglic) Tigliceric Acid, 2 C 5 H 10 O 4 = C 5 H s O 2 (OH) 2 Tigliceric acid is obtained by oxidising tiglic acid with potassium permanganate. It crystallises in small plates (from ether), melting point 88° C. The acid is very readily soluble in water; also soluble in alcohol and acetone, but insoluble in petroleum ether, chloroform, and benzene. 1 Cp. Lewkowitsch, Jour. Soc. Chem. Ind. 1897, 392. 2 Fittig, Liebig's Annalen, 283. 111. 70 CONSTITUENTS OF FATS AND WAXES C1IAP. Dihydroxypalmitic Acid, C 16 H 32 0 4 = C 16 H 30 O 2 (OH) 2 This acid has been obtained from dibromopalmitic acid (dibromo- addition product of hypogaeic acid) by boiling with silver oxide (com¬ pare above). It forms small laminae (from alcohol), melting point 115° C.; they dissolve readily in alcohol and ether. Dihydroxyasellic Acid (Dihydroxyheptadecylic Acid), Ci 7 H 34 0 4 = C 17 H 32 0 2 (OH) 2 Amongst the unsaturated acids of sardine oil Fahrion 1 assumes the presence of an acid C 17 H 32 0 2 , inasmuch as he isolated from the oxidised oil a dihydroxylated acid of the formula C 1T H 34 0 4 . This acid forms white nacreous laminae, of the melting point 114°-116° C. It is insoluble in cold, sparingly soluble in hot water, insoluble in petroleum ether, easily soluble in warm alcohol, and dis¬ solves with difficulty in ether. The barium salt dissolves in about 2000 parts of boiling water. Dihydroxystearic Acid, 2 C 18 H 36 0 4 = C 18 H 34 0 2 (0H) 2 Dihydroxystearic acid is best prepared by oxidising ordinary oleic acid with potash permanganate in alkaline solution. It forms crystalline laminae, melting at 136'5° C., and solidifying between 119° and 122° C. The acid is absolutely insoluble in water, easily soluble in hot, less so in cold alcohol, and sparingly in ether. This dihydroxystearic acid has been split into two optically active isomerides by means of its strychnine salt. 3 Dihydroxystearidic Acid, C 18 H 3G 0 4 = C 18 H 34 0 2 (0H) 2 Elaidic acid yields this acid on oxidation. Melting-point 99°- 100° C. p-DlHYDROXYSTEARIC ACID, C 18 H 3(i 0 4 = C lg H 34 0 2 (0H) 2 This second isomeride of the dihydroxylated stearic acid has been prepared from isooleic acid. It forms a crystalline powder, melting at 79° C., easily soluble in alcohol and ether. Dihydroxyjecoleic Acid, C 19 H 3s 0 4 = C 19 H 36 0 2 (0H) 2 On oxidising the liquid cod liver oil fatty acids with half-saturated solution of potassium permanganate at 0° C. this acid is obtained. Melting point 114°-116° C. 1 Jour. Soc. Chem. Ind. 1893, 936. 2 Natural dihydroxystearic acid, cp. p. 66. 3 Freundler, Jour. Chem. Soc. 1896, Abstr. I. 596. Ill TRIHYDROXYSTEARIC ACIDS 71 Dihydroxybehenic Acid, C 22 H 44 0 4 = C 22 H 42 0 2 (0H) 2 This acid is obtained by oxidising erucic acid with potassium permanganate; it forms granular crystals, melting at 132°-133° C., dissolving readily in warm alcohol, but insoluble in cold ether. ISODIHYDROXYBEHENIC ACID, 1 C 22 H 44 0 4 = 0 22 H 42 0 2 (0H) 2 Isodihydroxybehenic acid is prepared by oxidising brassidic acid with potassium permanganate. The acid melts at 99°-100 o, C., and solidifies at 88°-87° C. Para-dihydroxybehenic Acid, 2 C 22 H 44 0 4 = C 22 H 42 0 2 (0H) 2 This third acid of the composition C 22 H 44 0 4 is prepared from iso- erucic acid; it melts at 86°-88° C., and solidifies at 82°-80° C. 3. Trihydroxystearie Acids, C 18 H 33 0 2 (0H) 3 All the acids having this composition have been prepared by oxidising ricinoleic and ricinelaidic acids. Three acids have been described hitherto by Hazura and Griissner , 3 two having been derived from ricinoleic, and the third from ricinelaidic acid. Mangold has shown that also ricinelaidic yields two trihydroxylated acids, one of which is certainly identical with that prepared by Hazura and Griissner. The properties of these acids are briefly described below. Trihydroxystearic Acid, C 1s H 33 0 2 (0H) 3 This acid has been obtained from ricinoleic acid together with the following acid. It crystallises from hot water in microscopic needles, melting at 140°-142° C. It is insoluble in cold, and dissolves with difficulty in hot water, and likewise in alcohol and ether in the cold. Warm alcohol and glacial acetic acid dissolve it readily. Trihydroxy¬ stearic acid is insoluble in carbon bisulphide, chloroform, benzene, and petroleum ether. It is very likely that this acid is optically active. 4 a-ISOTRIHYDROXYSTEARIC ACID, C 18 H 33 0 2 (0H) 3 It differs from the preceding acid by its melting point 110° to 111' C., and by its ready solubility in ether and benzene; it is optically active. 4 /3-Isotrihydroxystearic Acid, C 1s H 33 0 2 (0H) 3 On oxidising ricinelaidic acid two isomerides are obtained according to Mangold. One acid derived from ricinelaidic acid has been described 1 Saytzeff, Jour, prakt. Chevi. 1894 (50), 82. 2 Alexandroff and Saytzeff, Jour, prakt. Cliem. 1894 (49), 63. 3 Cp. also Dieff, ibid. 1889 (39), 339. 4 Walden, Berichte, 1894, 3475. 72 CONSTITUENTS OF FATS AND WAXES CHAP. by Hazura and Griissner as having the melting point 114° to 115° C., and being sparingly soluble in hot water, ether, chloroform, and petroleum ether, and dissolving readily in alcohol. Probably Mangold’s acid, having the melting point 113° to 116° C., is identical with /Lisotrihydroxystearic acid. The second trihydroxystearic acid from ricinelaidic acid melts between 117° and 120° C. It appears very likely indeed that these two acids will rotate the plane of polarised light. 4. Tetrahydroxystearie Aeid, C ls H 82 0 2 (0H) 4 Tetrahydroxystearic or Sativie acid is the oxidation product of linolic acid. It crystallises from water in long needles or pyramidal prisms, possessing silky lustre, melting point 173° C. 2000 parts of boiling water dissolve one part of the acid. Sativie acid is insoluble in cold water, ether, chloroform, carbon, bisulphide, and benzene. Hot alcohol and glacial acetic acid dissolve it readily. Potassium permanganate oxidises it to azelaic acid. 5. Hexahydroxystearie Acids, C ls H 30 O.,(OH) 6 Linusic Acid, 1 C^HgoO^OH),. The linolenic acid contained in linseed oil yields on oxidation the hexahydroxylated acid : linusic acid. It crystallises from water in rhombic plates, occasionally also in needles, melting between 203° and 205° C. Water dissolves it more readily than sativie acid. Linusic acid is insoluble in ether, and sparingly soluble in alcohol. Isolinusic Acid, 1 C 1s H 30 O 2 (OH) 6 This acid is also formed on oxidising the linseed oil fatty acids, and from its occurrence the existence of isolinolenic acid is inferred. Isolinusic acid crystallises in prismatic needles, melting between 173° and 175° C. It is sparingly soluble in cold water, but dissolves easily in hot water and hot alcohol; it is insoluble in ether, benzene, carbon bisulphide, and chloroform. II.— Dibasic Acids Acids belonging to this class may be met with in the course of the examination of fatty acids obtained by the oxidation process (p. 68). They will be found in the aqueous solution, their presence 1 Reformatzky does not consider the existence of these acids as proved. illlliiu Ill DIBASIC ACIDS —ALCOHOLS 73 being due to secondary reactions. We shall only describe the two that are most likely to occur. Their solubility in water and their melting points afford the surest indications of the direction in which further investigations as to their identity necessarily lie. Suberic Acid, C s H 14 0 4 = C 6 H 12 (C00H) 2 Suberic acid crystallises from water in long needles or irregular plates, melting at 140° C.; it boils in vacuo at 152 , 5° 0., and under a pressure of 15 mm. at 230° C. Azelaic Acid, C 9 H 16 0 4 = C 7 H 14 (C00H) 2 This acid crystallises from water in large laminae or long flat needles, melting at 106° C.; it boils in vacuo at 158° C., and under a pressure of 15 mm. at 237° C. B. ALCOHOLS. I. —Alcohols of the Ethane Series, C n H 2n+2 0 The alcohols belonging to this series occur in waxes, or in the wax-like constituents of some fats, and are solid, white, crystallisable substances, melting without decomposition. They are not acted on by dilute alkalis or acids. On boiling with alcoholic potash and diluting the solution with water, they are precipitated unchanged ; in other words, they are “ unsaponifiable.” On heating the alcohols with organic acids, or their chlorides, or anhydrides, combination takes place with separation of water, ethers being formed ; thus on heating cetyl alcohol with acetic acid in presence of sulphuric acid, cetyl acetate is formed, as explained by the following equation :— C 16 H 33 . OH + CH 3 . CO . OH = H 2 0 + C 16 H 33 .0 . CO . CH 3 . The alcohols dissolve in concentrated sulphuric acid in the cold, forming alkyl sulphuric acids, which are split into their components on boiling with dilute acids. A characteristic property of the alcohols, which can be made use of for their identification, is their behaviour with soda-lime, heated with which they are converted into the corresponding fatty acids, with evolution of hydrogen. Thus cetyl alcohol yields palmitic acid, according to the equation— C 15 H 31 . CH 2 . OH + NaOH = C 15 H 31 . COONa + 2H 2 . The last - mentioned reactions have been employed for the quantitative determination of these alcohols, as will be detailed further on (chap. vi. p. 213). M 74 CONSTITUENTS OF FATS AND WAXES chap. Cetyl Alcohol, C 16 H 34 0 Cetyl alcohol, or ethal, occurs, combined with palmitic acid, in spermaceti, from which it is obtained on saponification. The alcohol has also been found in the sebaceous glands of geese and ducks. Cetyl alcohol is a white, tasteless, and odourless crystalline mass, melting at 50° C., and boiling at 344° C., without decomposition, at the ordinary pressure ; under a pressure of 15 mm. it boils at 189‘5° C., in vacuo at 119° C. The specific gravity at 49-5° C. is 0-8176 com¬ pared with water at 4° C.; at 60° C. 0-8105, and at 98'7° C. 0'7837. Cetyl alcohol is insoluble in water, but dissolves in alcohol, and is very easily soluble in ether and benzene. It is stated in text-books that cetyl alcohol, when heated with potassium bichromate and dilute sulphuric acid, is converted into cetyl aldehyde crystallising from alcohol and ether in lustrous laminae. This is incorrect, cetyl alcohol remaining for the most part unchanged when oxidised in aqueous solution; in acetic acid solution the oxidising mixture yields palmitic acid. Cetyl alcohol dissolves in cold concentrated sulphuric acid to form cetyl sulphuric acid, C 16 H 33 0. S0 3 H ; on boiling this product with aqueous hydrochloric acid the alcohol is regenerated. 1 Cetyl acetate crystallises in needles, melting from 22°-23° C., and boiling at 199 , 5°-200 , 5° C. under a pressure of 15 mm. It dissolves sparingly in alcohol. Cetyl benzoate crystallises in scales, melting at 30° C. ; it is readily soluble in ether, but dissolves with difficulty in alcohol. Octodecyl Alcohol, C 18 H 38 0 This alcohol also occurs, combined with acids, in spermaceti. It crystallises in large silvery laminae (from alcohol), melting at 59° C., and boiling at 40'5° C. under 15 mm. pressure. Distilled under a pressure of 100 mm. it undergoes decomposition. The specific gravity is 0-8124 at 59° C.; 0-8048 at 70° C., and 0‘7849 at 99T° C. Octodecyl acetate melts at 31° C., and boils at 222°-223° C. under a pressure of 15 mm. Carnaubyl Alcohol, C 26 H 54 0 (C 24 H 50 O) Carnaiibyl alcohol occurs in wool wax ; 2 from its alcoholic solution (in 75 to 80 per cent alcohol) crystals are obtained melting at 68 -69° C., solidifying at 67°-65° C. The alcohol very tenaciously retains water, forming a tallow-like mass, consisting of 26'7 per cent of this alcohol and 73 "3 per cent of water, which does not lose in weight on exposure to the air. On oxidising this alcohol with chromic acid, carnaubic acid is obtained. 1 Cochenhausen, Dingl. Polyt. Jour. 1897 (303), 284. 2 Darmstadter and Lifschiitz, Berichte, 1896 (29), 2890 ; Jour. Soc. Chem. Ind. 1897, 150. i > ; 11! 11i ii Ill CERYL ALCOHOL—MYRICYL ALCOHOL 75 An alcohol, C 24 H 50 O or C 25 H 52 0, has been found in small quantities in beeswax. Ceryl Alcohol, C 2g H 54 0 (C 27 H 56 0) Ceryl alcohol occurs as ceryl cerotate in Chinese wax, 1 and as ceryl palmitate in opium wax. The alcohol occurs in wool fat in the free state, 2 and perhaps also as ceryl cerotate. 3 Ceryl alcohol has also been recognised as a constituent of the wax of flax 4 and of carnaiiba wax. It is obtained in crystals from its alcoholic solution ; the crystals melt at 79° C., but cannot be distilled unchanged. On heating ceryl alcohol with soda-lime, cerotic acid is obtained. Ceryl alcohol behaves with concentrated sulphuric acid like cetyl alcohol. Ceryl acetate melts at 65° C. Isoceryl Alcohol, C 27 H 56 0 This alcohol has been found in the wax of Ficus gummiflua. The alcohol melts at 62° C.; its acetate at 57° C. Myricyl Alcohol (Melissyl Alcohol), C 30 H 62 O (C 31 H 64 0) Myricyl alcohol occurs as palmitate in beeswax, this ether form¬ ing that part of beeswax which is insoluble in alcohol ( Brodie ). In the free state and in combination with acids it has been found in carnaliba wax. It crystallises in small needles possessing silky lustre, and melting at 85° C. or 88° C. ( Gascard). It may be partly distilled unchanged. Nearly insoluble in cold, is dissolves readily in hot alcohol. Heated with soda-lime, it is converted into melissic acid. According to Schwalb , 5 the myricyl alcohol from beeswax possesses the formula C 31 H C4 0. Gascard 6 states that the myricyl alcohols from beeswax and carnaliba wax are identical, and have the composition c 31 h 64 o. II.— Alcohols of the Allylic Series, 7 C n H 2M 0 The alcohols belonging to this group have not yet been studied thoroughly ; it is noteworthy that they, like the alcohols of the preceding and following groups, occur in waxes. 1 Ceryl alcohol from Chinese wax has, according to Henriques, the formula C26^54^' 2 Lewkowitsch, Jour. Soc. Chem. Ind. 1892, 138. 8 Buisine, Bull. Soc. Chim. 1887 (72), 201. 4 Cross and Be van, Jour. Chem. Soc. 1890, 196. 5 Liebig’s Annalen, 235. 126. 6 Jour. Soc. Chem. Ind. 1893, 955. 7 Most likely the unsaturated alcohols occurring in sperm oil (Lewkowitsch, Jour. Soc. Chem. Ind. 1892, 134) belong to this series. 76 CONSTITUENTS OF FATS AND WAXES CHAP. Lanolin Alcohol, C 12 H 22 0 3 This alcohol has been stated by Marchetti 1 to occur in wool wax; shortly afterwards Darmstaedter and Lifschiltz 2 described two more alcohols of the formula C 10 H 20 O and C n H 22 0, also isolated from wool wax. The latter chemists, believing to have discovered the next homologues, proposed the name “ Lanestols ” for these alcohols, but more accurate examination undertaken by them in consequence of LewTcowitsch’s researches 3 proved that the two alcohols C 10 H, 0 O and C 11 H 22 0 do not exist in wool wax. Therefore also the existence of Marchetti’s alcohol becomes doubtful. An alcohol, having the composition C 15 H 30 O, has been found in the ether-soluble part of the wax of Ficus gummiflua. Another alcohol of the formula C 36 H 72 0 is said to occur, combined with acids, in the fat of cochineal. PSYLLOSTEARYL ALCOHOL, C 33 H 66 0 This alcohol has been discovered recently in the wax secreted by the aphide Psylla Alni . 4 It crystallises in the shape of fine flexible microscopical needles, melting point 95°-96° 0. The alcohol is easily soluble in hot chloroform and acetic anhydride, with difficulty in hot absolute alcohol, and is insoluble in cold spirits of wine and hot ether. III.— Alcohols of the Glycolic Series, C w H 2W+2 0 ; An alcohol having the composition C^H-.jO., C H ^23 il 46\CH 9 OH OH occurs, according to Sturcke 5 in carnaiiba wax, combined with acids. This alcohol forms a crystalline powder, melting point lOS^-lOS’S 0 C.; it dissolves sparingly in boiling petroleum ether, and somewhat more readily in ether and in benzene. On heating with soda-lime, a dibasic acid, C 23 H 46 (^qqq^, * s °^ ta ^ nec ^- Cocceryl Alcohol, C 30 H 62 O 2 The wax of cochineal contains the coccerate of this alcohol. The alcohol is a crystalline powder (from alcohol), melting between 101° and 104° C. On oxidising it with chromic acid in acetic acid solution, pentadecylic acid, C 15 H 30 O 2 is obtained. 1 Oazz. Chimica , 1895, 22. 2 Jour. Soc. Chem. Ind. 1896, 206. 3 Ibid. 1896, 15. 4 Jour. Chem. Soc. 1893, Abstr. i. 125. 5 Liebig's Annalen , 223. 283. Ill GLYCEROL 77 IV.— Alcohols of the Series C w H 2n+2 0 3 Glycerol, C 3 H 8 0 3 = CH 2 (OH). CH(OH). CH 2 (OH) Glycerol occurs in combination with fatty acids in all fats and fatty oils. Pure glycerol is a colourless, odourless, viscid liquid, having a purely sweet taste and possessing neutral reaction. Exposed for a long time to an intense cold it crystallises in rhombic crystals, melting at 20° C. With the help of a few crystals of glycerol previously solidified it can easily be transformed into crystals at the freezing point of water. Glycerol is oily to the touch, and produces on the skin, and especially on the mucous membrane, the sensation of heat, due to its absorbing moisture from the tissues. At ordinary temperature glycerol does not volatilise; at the boiling point of water, however, perceptible quantities are volatilised, its vapour tension at 100° C. and 760 mm. pressure being 64 mm. According to Clausnitzer 1 glycerol can be completely freed from water by allowing it to stand in vacuo over sulphuric acid. A dilute solution of glycerol may be boiled without any loss of glycerol until the solution contains 70 per cent. 2 If the boiling be continued glycerol volatilises with the water vapours. Pure glycerol boils under 760 mm. pressure at 290° C., undergoing slight decom¬ position. Under a pressure of 50 mm. it boils at 210° C., and under 12*5 mm. at 179*5° C. In a vacuum it distils unchanged. Heated slowly in a dish to 150°-160° C. pure glycerol evaporates without leaving any residue. At 150° C. it burns with a blue flame without emitting any odour. When it is heated rapidly, especially in a platinum dish, it burns with production of acrolein, yielding at the same time a residue of polyglycerols. The specific gravity of pure glycerol has been determined by several observers, whose statements do not agree, owing no doubt to the difficulty of freeing it from the last traces of water. In the following table some of the values are recorded together with the names of the observers (cp. chap. xii. p. 795) :— Specific Gravity. Observer. d^C. 1*26358 . MendelejefF. . 15° . d^C. 1*26468 Do. . 15° d l6*°- . 17*5° 1*2653 . Gerlach. dry^G. . 1*2620 Strohmer. _ 12° d 12 ° '-'*" 1*2691 Lenz. . 20° d 20O C. 1 *26348 . Nicol. 1 Zeitsch.f. cmalyt. Chemie, 20. 65. Hehner, The Analyst , 1887, 65. CONSTITUENTS OF FATS AND WAXES CHAP. 78 Glycerol, on exposure to the atmosphere, absorbs as much as 50 per cent of its own weight of water. It is miscible with water in all proportions, a contraction of volume and an increase of the tempera¬ ture talcing place at the same time. The greatest increase of temperature occurs on mixing 58 parts of glycerol (by weight) with 42 parts of water, and amounts to 5° C.; the greatest contraction equals IT per cent ( Gerlach ). Glycerol is also miscible in all proportions with alcohol; it dis¬ solves easily in a mixture of alcohol and ether, but is sparingly soluble in the latter solvent, one part of glycerol, spec, gravity T23, requiring about 500 parts of ether. It is therefore impossible to extract glycerol from its aqueous solution by means of ether. Glycerol is insoluble in chloroform, petroleum ether, carbon bisulphide, and benzene; it is also insoluble in fats and oils. In concentrated sulphuric acid glycerol dissolves to form glycero- sulphuric acid, C 3 H 7 0 3 S0 3 H, which is dissociated into glycerol and sulphuric acid on boiling with dilute acids. Glycerol possesses powerful solvent properties, combining in this respect the properties of water and alcohol; many substances dis¬ solve even more easily in it than either of the two liquids. The following table of solubilities will serve to illustrate this :— [■ 98 parts of crystal soda. 60 ,, ,, borax. 50 ,, ,, zinc chloride. 40 ,, ,, alum. 40 ,, ,, potassium iodide. 30 ,, ,, copper sulphate. 25 ,, ,, ferrous sulphate. '20 ,, ,, lead acetate. 20 ,, ,, ammonium carbonate. 20 ,, ,, ammonium chloride. 10 ,, ,, barium chloride. 8 ,, ,, sodium carbonate. 7'5 ,, ,, mercury bichloride. 100 parts of glycerol dissolve - 7-5 , An aqueous glycerol solution, spec, gravity 1T14, dissolves 0957 per cent of calcium sulphate. Soaps that are insoluble in water are partly dissolved by glycerol; thus— calcium oleate. Metallic Glyceroxides Glycerol dissolves caustic alkalis, alkaline earths, and lead oxide to form compounds with them. Lime, strontia, and baryta are pre¬ cipitated nearly completely from such solutions by carbonic dioxide, a small quantity only of the earths escaping precipitation. Ferric Ill GLYCEROL 79 oxide, cupric oxide, and bismuth oxide are dissolved by glycerol in presence of caustic potash. Monosodium glyceroxide, NaC 3 tL0 3 , is obtained on mixing a solu¬ tion of metallic sodium in absolute alcohol, i.e. sodium ethoxide, with glycerol. A precipitate is formed consisting of very deliquescent, rhombic crystals possessing the formula NaC 3 H r 0 3 + C 2 H ( .0. On heating to 100° C., the molecule of alcohol escapes, leaving the mono¬ sodium glyceroxide behind as a white, highly hygroscopic powder, which is split up by water into glycerol and caustic soda. If, in the preparation of monosodium glyceroxide, sodium methoxide be used, the crystalline compound has the following composition :— NaC 3 H 7 0 3 + CH 4 0. Disodium glyceroxide , Na 2 C 3 H 6 0 3 .—This compound is prepared by triturating the crystals of monosodium glyceroxide with one mole¬ cule of sodium ethoxide under absolute alcohol, and boiling the mixture for several hours. The potassium derivatives correspond completely to those of sodium just described. Calcium glyceroxide , CaC 3 H 0 O 3 , is a crystalline powder obtained by heating 14 parts of calcium oxide with 23 parts of anhydrous glycerol to 100° C., and cooling the mixture as soon as a violent reaction sets in. Water decomposes it into calcium oxide and glycerol. Barium glyceroxide , BaC 3 H 6 0 3 , is a deliquescent powder. It is prepared by warming 67'1 parts of anhydrous glycerol with 100 parts of baryta to 70° C. Hot water decomposes it at once into glycerol and baryta; cold water acts but slowly on it. Monoplumbo-glyceroxide, PbC 3 H 6 0 3 , is prepared by adding 500 grms. of lead hydroxide (obtained by pouring a warm solution of lead nitrate into a large excess of warm ammonia and drying the precipi¬ tate on the water bath) to 1000 grms. of boiling glycerol (85 per cent) with constant stirring. The mass is cooled down to 0° C., and finally 2500 c.c. of alcohol added at 0° C. 1 The monoplumbo-glycer- oxide thus prepared contains a little nitric acid, and very likely has the composition 2Pb . C 3 H 5 0 3 , Pb(NO) 3 + (OH)Pb(N0 3 ). A product free from nitric acid is obtained by Morawski’s method of preparation :— Dissolve 22 grms. of lead acetate in 250 c.c. of water, add 20 grms. of glycerol, heat and pour into the boiling solution a concentrated solu¬ tion of 15 grms. of potassium hydrate. A slight precipitate is filtered off, and the filtrate allowed to crystallise ; in the course of a couple of days a large quantity of fine white needles, the monoplumbo-glycer- oxide, separate. If basic lead acetate is used instead of sugar of lead, basic plumbo- glyceroxides are obtained of the composition Pb 3 (C..H-0 3 ) 9 and 4PbC 3 H ( .0 3 . PbO. Disodkm-mangano-glyceroxide, Na 2 (C 3 H 5 0 3 ) 2 Mn.—This compound is prepared by boiling anhydrous glycerol with PI parts of caustic soda (spec, gravity l - 38) to which 4 parts of freshly precipitated hydrated manganese peroxide have been added. 1 Fischer and Tafel, Berichte, 1888, 2635. 80 CONSTITUENTS OF FATS AND WAXES CHAP. Ethers of Glycerol Glycerol, possessing the properties of a weak base, combines also with acid radicles to form ethers. The most important ethers are those resulting from the combination of glycerol with fatty acids, viz. the glycerides, or the natural fats and oils. Of the ethers formed by the combination of inorganic acid radicles and glycerol but two need be mentioned here, glycyl trinitrate and glycyl arsenite, both being used in the arts, especially the former, which is manu¬ factured on an extensive scale, and forms the main outlet for the large quantities of glycerol that are produced commercially. Glycyl trinitrate, Nitroglycerin , C 3 H 5 (0. N0 2 ) 3 , is prepared by allow¬ ing glycerol to run into a mixture of one part of strongest nitric acid and two parts (by weight) of concentrated sulphuric acid. It is a heavy oily liquid of spec, gravity 1‘600. Its most remarkable property is that of exploding violently under certain conditions. Nitroglycerin forms the chief ingredient of almost all modern “ high explosives ” and “ smokeless powders.” Thus dynamite is produced by mixing nitroglycerin with kieselguhr, whilst “ blasting gelatin ” is prepared by dissolving nitrocellulose in nitroglycerin. Glycyl arsenite, C 3 H 5 As0 3 , is formed by dissolving arsenious oxide in glycerol. It is a fat-like substance, melting at 50° C. to a thick liquid. It decomposes above 250° C., but is volatile with the vapours of glycerol. This property explains why distilled and so-called chemically pure glycerins contain arsenic. 1 Glycyl arsenite is used in calico-printing works. Reactions of Glycerol One of the most characteristic reactions of glycerol is the pene¬ trating smell of acrolein which is emitted when it is rapidly heated. The same smell is noted when glycerides are burnt, as, e.g., when an oil-lamp or a tallow candle has been blown out. More distinctly still than by the heating of glycerol alone, the formation of acrolein is observed when the glycerol has been previously mixed with de¬ hydrating substances, such as (twice its weight of) hydrogen potassium sulphate. The acrolein is formed according to the following equation C 3 H 8 0 3 =C 3 H 4 0 + 2H 2 0. Acrolein is a liquid, possessing a most penetrating odour ; its vapours affect the eyes intensely, causing a copious flow of tears. It is readily soluble in water, boils at 42'4° C., and is easily converted into a resinous mass on exposure to the air. The most delicate reagents for detecting acrolein in aqueous solutions are — an ammoniacal solution of silver nitrate (reduction to metallic silver with production of a mirror) and Schiff’s reagent, a solution of 1 Lewkowitsch, Year Book of Pharmacy, 1890, 380. Ill GLYCEROL 81 rosaniline which has been decolourised by sulphur dioxide (restoration of the pink colour of decolourised rosaniline). The latter reaction, however, is less delicate than the silver test. A borax bead moistened with glycerol or a dilute glycerol solu¬ tion gives a green colouration by the flame test. This reaction, however, cannot be considered a very characteristic one, as it is a general reaction of alcohols. Glycerol displaces boric acid in solutions of borax. On this reaction the following method for the detection of glycerol may be based. Both the liquid to be tested and a solution of borax are tinged blue by addition of a few drops of tincture of litmus, and subsequently mixed. If glycerol be present the solution turns red in consequence of borac acid having been set free. On warming, the liquid becomes blue, and on cooling the red colouration reappears. On adding potassium permanganate to a solution of glycerol acidulated with sulphuric acid, decolouration takes place but very slowly. Also on boiling, the glycerol only undergoes complete oxidation with difficulty. Experiments made by Lenz 1 have shown that on boiling an acidulated solution of glycerol with an excess of a 1 per cent solution of potassium permanganate no more than 34 per cent of the quantity required for complete oxidation is reduced. It is only by a large excess of concentrated permanganate solution that glycerol is burnt to carbonic acid. According to Campani and Bizarri , on oxidising glycerol with potassium permanganate in alkaline solution, the following products are obtained: carbonic anhydride, formic, acetic, propionic, and oxalic acids, and also small quantities of tartronic acid. If, however, the oxidation in alkaline solution is carried out according to the directions given by Benedikt and Zsigmondy (see Quantitative Estima¬ tion of Glycerol, chap. vi. p. 208), the glycerol is completely split up into oxalic and carbonic acids according to the following equation :— C 3 H 8 0 3 + 2K 2 Mn,0 8 =K 2 C 2 0 4 + K,CO :i + 4Mn0 2 + 4H 2 0. Glycerol is completely burnt to carbonic anhydride and water by treatment with potassium bichromate and sulphuric acid— 3C 3 H a 0 3 + 7 Cr 2 0 7 K 2 + 28S0 4 H 2 =7[Cr 2 (S0 4 ) 3 + S0 4 K 2 ] + 9C0 2 + 40H 2 O or in a simpler form— 2C 3 H 8 0 3 + 70 2 =6C0 2 + 8H 2 0. Copper oxide is not dissolved by glycerol; if, however, a solution of a copper salt is mixed with a sufficient quantity of glycerol, potassium hydrate causes a blue colouration, but does not give a precipitate. Fehling’s solution is slightly reduced by glycerol if it is diluted with but little water. On boiling such a solution of glycerol with 1 Jour. Soc. Chem. Ind. 1885, 368. G 82 CONSTITUENTS OF FATS AND WAXES CHAP. Fehling’s solution for ten minutes, and allowing to stand for 24 to 48 hours, a red or a yellow precipitate is obtained. If, however, the glycerol be diluted with ten times its bulk of water no reduction occurs. At the temperature of boiling water a mixture of glycerol and silver nitrate solution gives on addition of a few drops of ammonia a precipitate of metallic silver. If an excess of ammonia be mixed with the glycerol in the cold, and then heat applied, according to the directions of the German Pharmacopoeia (cp. chap. xii. p. 788), as a rule no reduction takes place on addition of silver nitrate, simply because the glycerol has not been heated sufficiently ; the addition of caustic soda or potash, however, causes metallic silver to separate slowly. According to Bullnheimer 1 1 part of metallic silver corre¬ sponds to 11'3 parts of glycerol. On heating solutions of platinum, gold, mercury (rhodium and palladium) containing an excess of caustic soda with glycerol the metals separate just as in the case of silver. The oxides of other metals are not all reduced, or only to a lower stage of oxidation. The following two colour tests for glycerol have been recom¬ mended by Beichl : 1 2 — 1. Put two drops of glycerol in a dry test-tube, add two drops of previously liquefied phenol, and the same quantity of sulphuric acid, and heat very cautiously to a little above 120° C. When cold, a little water is added and a few drops of ammonia, when the brownish - yellow melt dissolves with a splendid carmine-red. This reaction is not observed if substances are present that yield car¬ bonaceous products with sulphuric acid, the brown colour of these masking the pink in the solution. 2. Add to the dilute glycerol solution a small quantity of pyro- gallol and a few drops of sulphuric acid, diluted with its own volume of water, and boil. A red colouration is produced, turning violet on the addition of tin tetrachloride. As carbohydrates and some alcohols give a similar reaction, care must be taken that these substances are excluded. On heating glycerol with hydriodic acid, allyliodide and propylen (in presence of an excess of hydriodic acid, also isopropylioide) are formed. Experiments undertaken with a view to exclude the forma¬ tion of propylen (in which case it would have been possible to deter¬ mine the glycerol quantitatively by means of Beneclikt and Griissner’s methoxyl method 3 ) have proved unsuccessful. With the same object in view, viz. to obtain one derivative of glycerol that would facilitate its quantitative determination, Niemilowicz 4 has studied the action of hydrobromic acid on a solution of glycerol in concentrated sulphuric acid. There are, however, two products formed : tribromopropalde- hyde and tribromopropionic acid. 1 Forscliungsb. Lebensmittel, Hyg., forens. Chemie, 1897 (4), 12 ; Cham. Ztg. 1897, Repert. 76. 2 Jour. Soc. Chem. Ind. 1882, 202 ; 1883, 356. 3 Ibid. 1889, 925. 4 Jour. Cliem. Soc. 1890, Abstr. 861. Ill CHOLESTEROL 83 Isoglycerol (?).—IFanklyn and Fox 1 are of the opinion that the natural fats consist of glycerides and “ isoglycerides.” The latter are assumed to contain the hypothetical “isoglycerol,” having a formula corresponding to that of orthopropionic acid, C 2 H.. C(OH) 3 . Ihis acid is supposed to instantly split up into propionic acid and water, the orthopropionic acid not being able to exist in the free state. Such assumptions scarcely deserve serious refutation. V.— Alcohols of the Aromatic Series Cholesterol, C. 2(i H 44 0 Cholesterol occurs in considerable quantities in sheep’s wool, from which it is recovered on a large scale, and brought into commerce under the name wool fat, a product consisting chiefly of choles- teryl and isocholesteryl ethers. It is found in human bile, the biliary calculi being almost wholly composed of cholesterol. In somewhat larger quantities it also occurs in liver oils. Cholesterol appears to be frequently met with in the animal organism, its presence having been proved in blood, in the brain, in hair, in the epidermis, in the yolk of eggs, in the testicles, and in various morbid products of the animal body— e.g. the hydropic liquid of the stomach, ovarian tumours, etc. The chemical formula of cholesterol has not yet been established satisfactorily. Beinitzer 2 .is of the opinion that three homologues of cholesterol exist, and that the formula may, therefore, vary according to the source of cholesterol. The three homologues have, in his opinion, the formulae C 25 H 42 0, C 26 H 44 0, and C 27 H 4(i O. Cholesterol pre¬ pared from biliary calculi has the composition C 27 H 46 0. Mauthner and Suicla favour the formula C 27 H 44 0; Walitzki, again, the formula C 27 H 46 0. Cholesterol crystallises from chloroform in anhydrous needles (cp. p. 86,under Phytosterol), having the specific gravity P067, and melting point 147 C. Carefully heated it volatilises undecomposed, but it is best distilled in a vacuum. From its hot alcoholic solution it crystallises in lamime, containing one molecule of water which evaporates on standing over sulphuric acid, but more quickly on dry¬ ing the crystals at a temperature of 100° C. Cholesterol is insoluble in water, and very sparingly soluble in cold dilute alcohol. It dis¬ solves in 9 parts of boiling alcohol, specific gravity 0'87, and in 5'55 parts of boiling alcohol, specific gravity 0 - 83. Ether, carbon bisulphide, chloroform, and petroleum ether dissolve it easily. Solutions of cholesterol are lsevo-rotatory. Hesse found for the specific rotation in ethereal and chloroformic solutions, [«] D = - 31-12 and [. On adding a solution of bromine in carbon bisulphide to choles¬ terol dissolved in the same menstruum, a bromo-addition product, cholesterol dibromide, C 26 H 44 0. Br 2 , is obtained. An iodo-chloro- addition product is most likely obtained 1 by using Hull’s iodine absorption method; cholesterol may thus be estimated quantitatively (chap. vii. p. 232). Cholesterol dissolves in concentrated sulphuric acid but does not form, like the aliphatic alcohols, compounds with sulphuric acid which are split up into their components on boiling with dilute acid. It appears that the cholesterol is converted into cholesterones. 2 On heating with soda-lime 3 no fatty acids are formed, or, at any rate, very small quantities (important difference from aliphatic alcohols). Cholesteryl acetate , C 2(i H 43 0. C 2 H 3 0, is prepared by boiling choles¬ terol with one and a half times its quantity of acetic anhydride in a flask connected with an inverted condenser. This reaction also may be used for the quantitative determination of cholesterol. 4 Cholesteryl acetate crystallises in small needles, melting point 114° C., nearly in¬ soluble in cold and sparingly soluble in boiling alcohol. Cholesteryl benzoate, C 26 H 4:j O . CO . C e H 5 , is formed by heating choles¬ terol with benzoic anhydride in a sealed tube to a temperature of 200° C. It is nearly insoluble in boiling alcohol, and crystallises from ether in rectangular plates, melting at 150°-151° C. Colour Reactions of Cholesterol (cp. Lewkowitsch, Jour. Soc. Chem. Ind. 1892, 144). The following two reactions have been recommended by Schulze 1. If a minute quantity of cholesterol be carefully heated with a drop of concentrated nitric acid to dryness on a crucible cover, a yellow stain is obtained; on pouring a little ammonia on it a yellowish-red tint is produced. 2. If a little cholesterol be triturated on a crucible cover, with one drop of a mixture consisting of three measures of concentrated hydrochloric acid and one measure of a 10 per cent solution of ferric chloride, on evaporating to dryness a violet-red colouration is pro¬ duced, changing to blue. It must, however, be remembered that oil of turpentine, camphor, and other substances behave in the same way. A very delicate and characteristic reaction has been described by Hager, and slightly modified by Salkowski. A few centigrammes of cholesterol are dissolved in 2 c.c. of chloro¬ form, an equal volume of concentrated sulphuric acid is added, and the mixture shaken. The chloroformic solution immediately becomes coloured blood-red, afterwards cherry-red and purple; this last tint remains for several days. The sulphuric acid layer under the chloro¬ form shows a strong green fluorescence. 5 On pouring a few drops of the purple chloroform layer into a porcelain basin, the red colour changes rapidly to blue, green, and finally to yellow. On diluting 1 Lewkowitsch, Jour. Soc. Chem. Ind. 1892, 43. 2 Cochenhausen, Dingl. Polyt. Jour. 1897 (303), 284. 3 Lewkowitsch, Jour. Soc. Chem. Ind. 1896, 14. 4 Ibid. 1892, 43. 5 This green fluorescence is, in my opinion, due to presence of isocholesterol. Ill ISOCHOLESTEROL 85 the purple chloroformic solution with more chloroform it becomes nearly colourless, or acquires an intense blue colour; if it now be shaken again with the sulphuric acid layer the former colouration reappears. These changes of colour are clue to traces of water in the chloroform. 1 If on shaking a chloroformic solution of cholesterol, prepared from fats, with concentrated sulphuric acid, the blue colouration is noticed at once, the presence of so-called “ lipochromes ” is indicated, which have been shown to occur in cod liver oil, the fat of the yolk of eggs, palm oil, and in small quantities in cow butter. But even in these cases the red colouration soon appears. Liebermann’s “ cholestol ” reaction is very characteristic, and is shown by the minutest quantities of cholesterol. A solution of cholesterol in acetic anhydride gives a violet-pink colouration 2 on adding concentrated sulphuric acid, drop by drop. Sharper still is the modified form of this test as proposed by Burchard :—Dissolve a little cholesterol in 2 c.c. of chloroform, add 20 drops of acetic anhydride, and one drop of concentrated sulphuric acid. Un¬ fortunately resin acids (colophony) and other substances give the same or very similar reactions. Nagelvoort 3 has obtained from a specimen of cod liver oil pointed acicular crystals, intermixed with rather long, narrow, and obtruncated ones. They had the appearance of phytosterol, but gave the colour reaction of cholesterol, becoming reddish-brown when mixed with sulphuric acid, and dirty green on subsequent addition of water. Isocholesterol, C 26 H 44 0 Isocholesterol is isomeric with cholesterol, and resembles it in many respects. It occurs together with cholesterol in wool fat. Isocholesterol crystallises from ether in fine needles, melting at 137°-138° C. It dissolves sparingly in cold, but rapidly in boiling alcohol, from which, on cooling, it separates in a jelly-like mass. It is readily soluble in ether and in petroleum ether. Solutions of isocholesterol are also optically active; in contradis¬ tinction to those of cholesterol they are dextro-rotatory. [a] D = +60° in ethereal solution. Isocholesteryl acetate, C 26 H 43 0. C 2 H 3 0, has been obtained as an uncrystallisable mass. Isocholesteryl benzoate, C 06 H 43 0. C 7 H r O, is a crystalline powder, consisting of very fine needles melting at 190°-191° C. It dissolves sparingly in alcohol, more easily in hot acetone, and very easily in ether. Colour Reactions of Isocholesterol. —Isocholesterol gives the same 1 According to Herbig (Dingl. Polyt. Journ. 1897 (303), 191) cliolesteryl palmitate and cliolesteryl cerotate give the same colour reaction. 2 It appears that wool fat cholesterol does not show the violet-pink given by gallstone cholesterol, hut becomes red at once. This question is under examination. 3 Analyst, 1889, 217. 86 CONSTITUENTS OF FATS AND WAXES CHAP. Ill reaction as cholesterol with nitric acid and ammonia. Its solution in acetic anhydride, on addition of one drop of concentrated sulphuric acid, gives a yellow and afterwards a reddish-yellow colouration, show¬ ing at the same time a green fluorescence. The same reaction becomes more distinct on using Liebermann’s “ cholestol ” test in Bur chard's form (see above). In a mixture of cholesterol and isocholesterol the colour reaction of the latter seems to prevail and to mask the violet-pink colouration due to cholesterol. Phytosterol, C 26 H 44 0 Phytosterol, the “cholesterol of plants,” occurs in the seeds of peas, beans, and almonds ; it has been found further in the gluten of wheat, in maize, and in Calabar beans, and in minute quantities in most vegetable oils (chap. ix. p. 317). Phytosterol very much resembles cholesterol; they differ, however, in their crystalline form and their melting points. The crystals of cholesterol deposited from its hot alcoholic solution appear as a magma of laminae, which are discerned, under a microscope, as extremely thin rhombic plates, showing often re-entering angles. Phytosterol, however, crystallises in solid needles, grouped in tufts; under the microscope there are discerned long, solid needles arranged in star- or bunch-like groups. The crystals have the composition expressed by the formula C 26 H 44 0 + H 2 0; they melt at 132°-134° C., whilst the melting point of cholesterol is 147 C. Solutions of phytosterol are laevo-rotatory [a] D = - 34'2. A chloroformic solution of phytosterol gives the same reaction with sulphuric acid as the corresponding solution of cholesterol, but there is this slight difference that the colouration obtained with phytosterol passes after a few days into a bluish-red, whereas the cholesterol solution becomes more of a cherrv-red. CHAPTER IV DETERMINATION OF FOREIGN MATTERS OF A NON-FATTY NATURE, AND PREPARATION OF THE FATTY SUBSTANCE FOR EXAMINATION 1. Sampling’ In sampling fat one must be careful to obtain a sample really repre¬ senting the bulk. This can easily be done with liquid fats. In the case, however, of solid fats it is more difficult, and great care has to be exercised, or grave errors may be committed. A. Norman Tate, G. cVEndeville, and Gnthleert have agreed upon the following reliable method of sampling tallow and other solid fats, which is practically the method used at seaports and in large works. By means of an auger a cylindrical sample of fat, at least eight inches long and one inch thick, is taken from each cask, or a convenient number of casks, and each sample is labelled with the number and marks of the cask, the gross weight and tare of each cask being also noted. The several samples are mixed by the chemist in quantities correspond¬ ing to the net weight of their respective casks, and the sample thus obtained is roughly divided into three equal parts, two of which are melted in a dish at a temperature not exceeding 60° C. with constant stirring. As soon as the fat is melted to a clear liquid, the dish is removed from the source of heat, and the third part is added. As a rule the liquefied fat retains enough heat to melt the added quantity ; the whole mass is thereby cooled, and solidifies more rapidly. As soon as the fat commences to become pasty, it is necessary to stir vigorously in order to prevent water and impurities from settling down to the bottom of the dish. The first operation in the examination of fats is the estimation of water and of those substances of a non-fatty nature which necessarily adhere to them owing to the process of manufacture, or which have been added fraudulently. It must not, however, be forgotten that a number of fat-like substances, as resin, paraffin wax, paraffin oils, tar oils, and resin oils, may be retained by the fat in intimate intermixture with it. These niMUii 88 DETERMINATION OF FOREIGN MATTERS chap. bodies are determined severally when the examination of the dry and preliminary purified fat is reached (chap, vii.) 2. Estimation of Water About 5 grms. of the fat are accurately weighed in a small beaker or flask containing a thin glass rod, and dried at 100° C. until the weight remains constant. Whilst drying, the fat is conveniently stirred up from time to time, as the water will collect below the fat and only slowly evaporates through it. For this reason Sonnenschein 1 proposes to dry the fat in a flask closed by a cork perforated with two holes, through one of which passes a straight tube to the bottom of the flask, whilst the other is fitted with a bent tube ending with the cork. The flask is tared with all the fittings, the fat poured into it, and its weight determined. A calcium chloride tube is then attached to the straight tube, and the bent tube being connected with the filter pump, a current of dried air is drawn through the fat at 100° C. As, however, liquid fats and fatty acids are easily oxidised under these conditions, more accurate results will be obtained by aspirating an indifferent gas ( e.g . dried carbonic anhydride or coal gas) through the fat. (Cp. also chap. xii. Oleaginous Seeds.) Henzolcl recommends, especially for the determination of water in cow butter, the following method: weigh off 20 grms. of freshly heated pumice stone, cooled under a desiccator, in a shallow dish, add 10 to 12 grms. of the fat, and heat to 100° C. for two hours, but not longer, stirring occasionally with a glass rod which has been tared with the dish. Sometimes solid fats, such as tallow, contain small quantities of caustic potash or of potash soap which have been fraudulently added in order to facilitate the incorporation of water with the fat. In that case the fat cannot be freed from the last traces of water by drying at 100° C., and the safest plan will be to determine the amount of fatty bodies, impurities, and of potash separately, and to find the percentage of water by difference. 3. Determination of Foreign Matters of a Non-fatty Nature in Fats To determine solid substances, such as remnants of animal or vege¬ table tissue, dirt, or fraudulent admixtures, 10-20 grms. of the fat are extracted in a flask by shaking with one of the following solvents : petroleum ether, chloroform, carbon tetrachloride, ether, or benzene. The solution is then poured through a tared filter, and the residue washed on the filter with the same solvent, until a few drops of the filtrate, evaporated on paper, no longer leave a grease-spot. The filter with its contents is then dried at 100° C. and weighed. The dried residue may be incinerated and weighed again, when the difference 1 Jour. Soc. Chem. Ind. 1886, 508 (Illustration). IV STARCH—SUBSTANCES SOLUBLE IN WATER 89 ■ will give the amount of organic matter. If the amount of ash is large I (salt, chalk, clay, or lime from fraudulently added lime soap), a further ■ examination is sometimes of importance. ■ Of the foregoing solvents, petroleum ether will be found the most ■ convenient, inasmuch as it dissolves smaller quantities of resinous I bodies than any of the other solvents mentioned. Therefore, if there I be no reason against the use of petroleum ether— e.g. in the case of i castor oil—this solvent should be employed ; all the more so, as it I can easily be obtained in a state of purity and free from acid, and, I furthermore, it need not be dried beforehand. It should, however, I be rectified carefully by means of a fractionating column, and all I portions boiling above 80° C. should be discarded. If necessary, it I should be purified by shaking with a little concentrated sulphuric I acid; after separation from the dark acid layer the petroleum ether I must be washed with water until entirely free from acid. I Nordlinger has obtained colourless extracts when using petroleum I ether for palm nuts, coprah, etc., whereas ether gave coloured solutions. I If a considerable quantity of organic matter has remained on the I filter, it should be tested for metallic soaps (lime soaps, aluminium I soaps, etc.) and for starch. On treating with mineral acids the former I will be decomposed with liberation of fatty acids, whilst the metals I will pass into the aqueous solution. I Starch can be detected in the organic residue by means of the I blue colouration it gives with iodine solution, and its presence may be I confirmed by the microscope. Chateau has recommended the following I method :—Heat one part of the suspected fat with two parts of I acidulated water in a test-tube, or in a small beaker, and boil for a I few minutes. Place the test-tube or beaker in water of 40° C., so as to allow the fat to solidify gradually and the impurities to settle out. On adding a solution of iodine the blue colour will be noticed distinctly if starch be present. It is important to note that on dissolving a fat in petroleum ether, etc., starchy matter is liable to retain some fat. Hence the amount of starch does not correspond exactly to the weight of the dried residue. K'unig recommends, therefore, especially in butter analysis, to wash the residue, after exhaustion with ether, with cold water, in order to remove any substances soluble in water. The residue is made soluble by boiling with water, and finally converted into glucose by heating with hydrochloric acid. The glucose may be estimated by means of Fehling’s solution. Substances soluble in water (some of them, e.g. common salt, may be found on the filter) are removed from the fat by shaking a large quantity, say 50-100 gi'ms., with warm water, whereby solid fats are easily liquefied. The mixture is allowed to stand in a warm place until it has separated completely into two layers. Should the separation not be complete, after a short time, or if part of the fat be retained as an emulsion by the aqueous layer, addition of a little ether will be found effective in causing separation. The aqueous liquid is then removed by means of a separating funnel and examined. 90 PREPARATION OF FATTY SUBSTANCE FOR EXAMINATION chap. Any traces of sulphuric acid left in the oil from refining operations will be found in this aqueous layer, and may be estimated by titra¬ tion with standard alkali, using methylorange as indicator. Other substances present may be determined in the residue left on evaporation. Ethereal oils contained in the fats, as in nutmeg butter, are best determined by distillation in a current of steam. On weighing the remaining dried fat the quantity of essential oils will be found by difference. The distillate may be shaken out with ether, and the ether residue further examined. 4. Determination of Fat The determination of fat in a sample may be conveniently com¬ bined with that already described for the estimation of foreign substances, by collecting the filtrate in a tared flask, evaporating the I solvent, and weighing the dried residue. I If mucilaginous or starchy substances are present in the fat the I following process will be found more convenient and, at the same I time, more reliable. 5-6 grms. of the sample are intimately mixed N with 4-6 times its weight of pure, finely-powdered gypsum, and the I mixture dried at 100 C. It is then transferred to an automatic I exhausting extractor. I Gebek, 1 however, states that on using gypsum (or charcoal) for the determination of fat in fodders discordant results are obtained, and proposes, therefore, the employment of Spanish earth used for clarifying wine. Gantter recommends, instead of gypsum, the use of cellulose as obtained by the sulphite process; of course, the cellulose has to be previously extracted with the petroleum ether. 3 grms. of the sulphite cellulose are placed in a weighing bottle, D dried and weighed. 5 grms. of the fat are then added and, after drying for one and a half hours, re-weighed, when the difference found will give the proportion of water. The dried substance is finally transferred to • an extractor to be exhausted. The most convenient apparatus for ex¬ traction of fat is the one devised by Soxhlet (Szombathy) (Fig. 1). A modification of this apparatus, which is preferred by many as being less liable to break, is shown in Fig. 2. Pig. i. The substance to be extracted is put in a cartridge of filter paper, easily prepared by rolling it round a cylindrical piece of wood of suitable size, and folding it up at one end. The cartridge is filled with the substance and transferred to the extractor 1 Jour. Soc. Cliem. Ind. 1893, 713. Fig. 2. IV DETERMINATION OF FAT 91 A. Care must be taken that the syphon tube does not become stopped by the paper case ; nor should the cartridge be filled up to the top, lest some particles of the substance be washed over by the solvent and carried away. To be quite safe, it will be found convenient to place a plug of (extracted) cotton-wool on the top of the substance, or to close the top by folding the paper. The tube B is then fitted by means of a cork to a flask holding 100-150 c.c., and containing about 50 c.c. of the solvent (petroleum ether, ether, chloroform, etc.) Another portion of the solvent is carefully poured on the substance in B until it commences to run off” through the syphon D. Finally an inverted condenser is adapted to A, and the whole apparatus placed on a water bath. As the solvent boils, the vapours pass through B and C into the condenser and fall condensed on the substance in the paper case. When the liquid has reached the level h, the solution syphons off automatically through D, and A. is emptied completely. The solvent is again evaporated and recon- clensed, and serves again for extracting, and so on. The filling and emptying of A may easily be re¬ peated twenty to thirty times within an hour. In using the form of Soxhlet’s extractor described above, there is always some doubt as to the exact time when the exhaustion is com¬ pleted, and, as a rule, the operation A lasts a far longer time than necessary, involving both loss of time and of the solvent. To avoid this Lewlco- witscli 1 has a tap fitted on to the syphon tube, allowing some of the solvent to be withdrawn at any time, with a view to ascertain when extraction is complete (Fig. 3). If the substance to be exhausted had been collected on a filter, the simplest plan is to fold the filter up and place it at once in the extractor. Fruhling 2 has proposed a modified form of the Soxhlet extractor which admits of convenient handling on weighing before and after the extraction. The essential part of the apparatus, serving for the reception of the sample, is shown in Fig. 4. It has the shape of an ordinary filter-weighing bottle, but differs from it in that the bottom has a funnel-like shape. It is provided with a syphon, the longer limb of which passes through the bottom, where it is cut off aslant. The sides of A are continued beyond the protruding limb of the syphon, so as to allow of its standing in an upright position on the pan of a balance, and at the same time serving to protect the tube from breakage. The shorter limb of the syphon reaches to the bottom of the bottle, and is provided with a bulb in its upper part, 1 Jour. Chem. Soc. 1889, 360. 2 Jour. Soc. Chem. Ind. 1889, 568. Fig. 4. 92 PREPARATION OF FATTY SUBSTANCE FOR EXAMINATION chap. which serves to sever the column of the solvent when the bottle is taken out of the tube B (Fig. 5). This tube is the ordinary form of the Soxhlet extractor without its syphon tube, and serves for the reception of A. The upper part of B may be fitted with a carefully-ground stopper, hav¬ ing tube C attached to it. The whole arrangement and application of the apparatus will be readily understood from a glance at the annexed figures. For the extraction of substances at the boiling point of the solvent, F. K. Stock has recommended a modified extractor. 1 The number of modifications and improvements of Soxhlet’s ingenious apparatus is almost legion. As the above-described forms will be found suitable for most purposes, the reader must be referred to the pages of the Journal of the Society of Chemical Industry , where a complete record of all proposed forms will be found. When the extraction is completed the flask con¬ taining the solution is detached from the extractor, the solvent distilled off' on the water-bath, and the fat dried in an air-bath at a temperature not exceed¬ ing 100°-110 C. until the weight remains fairly constant. Care must be taken not to dry too long, nor at too high a temperature, inasmuch as on the one hand volatile fatty acids may escape, causing loss of substance, whilst on the other hand an increase of weight may take place owing to oxidation (cp. Oleaginous Seeds and Oil-cakes, chap. xii. p. 673). The apparatuses described will also be found Fig. 5 . useful for the estimation of fat contained in oleagin¬ ous seeds, oil-cakes, and other bodies. Previous to the extraction, these substances should be pounded or disinte- giated, and, if required, dried at a suitable temperature (cp chap xii p. 674). v 1 1 ‘ ' 5. Preparation of the Fat for Examination The most important operation in the analysis of fats is the ex¬ amination of the fatty substance after it has been freed from water and foieign matters. In most cases it will suffice to dry and filter the melted fat in order to obtain it sufficiently pure; washing with warm water or distillation in a current of steam will but rarely be required. The drying and filtering of the fat is best carried out in a sjiacious drying oven provided with a thermostat (thermo-regulator). 1 Jour. Soc. Chem. Ind. 1897, 107. IV REICHERT'S THERMOSTAT 93 The drying oven may be one of the customary type of about the following dimensions: 10 inches high, 10 inches broad, and 6 inches deep. I use an apparatus made with slight alterations after Sidersky’s 1 design. This is a jacketed cylindrical oven provided with a door having a thick glass plate and closing hermetically. Suitable taps allow the drying to proceed in vacuo or in a current of dried air (or carbonic anhydride), which can be aspirated slowly through the drying chamber. The space between the two cylinders can be filled with water or any other suitable liquid, and thus any required tem¬ perature may be kept constant without attention for any length of time. A very efficient thermostat has been described by Reichert. Its improved form is represented by Fig. 6. It consists of a capillary tube enlarged at the bottom to a bulb c,— in short, of a thermometer, the top part of which is widened out as shown. The capillary branch tube is supplied with a screw S, by means of which the level of the mercury may be adjusted at will. The gas- supply tube A is carefully ground into the upper part of the thermometer tube, and extends down to the joint of the stem. Besides having the opening at the bottom, A is perforated with a very small hole at a. The gas entering A leaves the regulator at B. The thermostat is fixed along with an ordinary thermometer by means of a cork perforated with two holes into the nozzle of the drying oven; A is then connected with .the gas supply, and B with the gas burner. The tube A must be adjusted in such a way that communication with B is established through a , whilst S has been screwed out of the tube suffi¬ ciently to allow the mercury to fall below the tapered part. The oven is then heated, and at the moment the desired temperature has been reached S is screwed into the tube until the column of mercury just reaches the tube A. The exact moment is easily observed by the flame of the burner becoming smaller. Gas is then supplied to the burner through a only, until in consequence of the falling of the temperature in the oven the mercury falls, thus allowing an additional supply of gas to flow through A, the lower end of which had been closed before by the mercury. With a rise of temperature the mercury expands, and again closes the lower opening of A, thus causing the temperature to fall, and so on. It is thus possible to keep the temperature constant, or nearly so, within very small limits indeed. In the case of the flame of the burner being too high for the desired temperature, even when gas passes through a only, the gas supply must be diminished by turning the tube A a little, thus partially closing the opening a. 1 Jour. Soc. Ohem. Ind. 1890, 967. 94 PREPARATION OP FATTY SUBSTANCE FOR EXAMINATION CHA1’* The screw S is usually cemented by the maker of the instrument with sealing-wax, which, however, easily melts, allowing mercury to ooze through the cork ; care should therefore be taken to protect the wax from becoming overheated. 1 As another objection to Reichert's thermostat, it has been pointed out recently by J. JV. James , 2 that after short use,—a few days or weeks, depending on the purity of the gas,—the upper surface of the mercury becomes coated with a black powder (mercuric sulphide) which before long impairs the delicacy of the regulator. It becomes then necessary to take the apparatus to pieces for cleaning. James has therefore designed a thermostat, making use of Reichert's principle, but avoiding the objectionable passing of the gas over the surface of the mercury. For the drawing and instructions for use the original paper should be consulted. Another new thermostat, made entirely of metal and not containing mercury, has been described by Forges , 3 The temperature at which the fat is melted should not exceed its melting point by more than 20° C. Solid fats, containing large quantities of water, such as butter fat, are best allowed to stand in the melted state until the water has settled out. The best plan is to pour off the fat into another vessel, and then to filter through dry paper. Before filtering, the fat should have been allowed to become perfectly dry. Dieterich dries beeswax by melting it over anhydrous sodium sulphate with subsequent filtering. If a fat contains such a large quantity of solid substances as to make direct filtration impossible, or if it has to be prepared from oleaginous seeds or oil¬ cakes, a previous extraction by means of petroleum ether becomes imperative. Ether, carbon bisulphide, benzene, or chloroform, do not give such satisfactory results as pure petroleum ether. Any of the exhausters described above may be employed. For large quantities, however, the apparatus represented in Fig. 7 will be 1 The principle underlying Reichert’s thermo-regulator, hut avoiding the last men¬ tioned drawback, has been employed by Berlemont, cp. Jour. Soc. Ghem. Ind. 1895, 821. 2 Jour. Soc. Ghem. Ind. 1893, 225. 3 Ztitsch.f. ancdyt. Ghemie, 1893, 212. IV SULPHUR 95 found most convenient. Its construction will be readily understood by a glance at the illustration ; a may be a lead pipe covered with a non-conducting mass (asbestos, or simply string); b is adapted to a condenser. It should be remembered that the fats prepared as described still contain small quantities of foreign organic substances (cp. chap, i.) 6. Determination of Inorganic Substances in the Fatty Matter The fatty matter prepared as described in some cases contains sulphur or phosphorus, or chlorine or metals. Therefore the fatty substance before being examined should be tested for these im¬ purities. Qualitative Test for Sulphur Until recently the presence of sulphur in a liquid fat was con¬ sidered as sufficient proof of the presence of rape, or some other oil extracted from the seeds of Cruciferse ; but it has been shown that the cold-pressed oils are free from sulphur. On the other hand, oils which have been extracted by carbon bisulphide may retain small quantities of sulphur. Sulphur is detected by saponifying the oil under examination with caustic soda or caustic potash, when sodium or potassium sulphide is formed. On adding an alkaline lead solution a black or brown precipitate will be obtained. Valenta recommends boiling a somewhat large quantity of the oil with a small quantity of caustic potash with constant stirring, and then to add a little water. The soap solution is then separated from the unsaponified oil and tested with the lead solution. A rapid method is to immerse a bright silver coin into the boil¬ ing oil. In presence of sulphur the coin will become brown or black. Sulphuric acid or sulphonated fatty acids cannot be detected by the preceding methods. On washing the oil with water any sulphuric acid present will pass into the aqueous layer, and can be detected by barium chloride. Sulphonated fatty acids, produced by prolonged treatment of the oil with sulphuric acid (see Turkey-red Oil), must be decomposed first, either by boiling with hydrochloric acid or by fusing with caustic potash and potassium nitrate. Quantitative Determination of Sulphur (a) Liebig's Method .—Weigh off carefully a somewhat large quantity of the sample, and saponify it in a silver dish with aqueous or alcoholic potash; boil down until the mass becomes syrupy, allow to cool, add a few sticks of pure caustic potash and also potassium 96 PREPARATION OF FATTY SUBSTANCE FOR EXAMINATION chap. nitrate, about one-eighth of the weight of the potash used, and finally a few drops of water. Heat the mass carefully with con¬ stant stirring—using a silver stirrer—and raise the heat gradually until the mass is fused and has become perfectly white. Then allow to cool, dissolve in water, and transfer to a large beaker, in which the sulphuric acid formed is precipitated in the usual way with barium chloride. In very accurate work it is preferable to boil out the heated barium sulphate with dilute hydrochloric acid and to weigh again. Morpurgo 1 saponifies 25 grms. of the sample with caustic soda and adds 10 c.c. of a 10 per cent lead acetate solution and a few drops of acetic acid, when a precipitate consisting of free fatty acid, lead sulphide, and lead soap is obtained. The aqueous portion is allowed to drain off and the precipitate mixed with 50 c.c. of 90 per cent alcohol, and then with an excess of acetic acid. The mixture is warmed on a water bath, so that lead sulphide may settle out. The free fatty acids are then removed, and the lead sulphide repeatedly washed with dilute acetic acid, and finally with dilute ammonia, and collected on a filter and weighed. (b) Allen’s Method.—Allen 2 proposes for the determination of the sulphur in oils, e.g. rape oil, an apparatus similar to that used for the estimation of sulphur in coal gas (Fig. 8). 5 grms. of the oil are mixed with 45 grms. of purified methy¬ lated spirit, and burnt in the lamp A fitted by a bung into the wider end of a curved adapter. e contains solid ammonium car¬ bonate. The gases pass through C into the condenser D filled with wetted glass balls. The lower end of D is furnished with a glass stop - cock h for drawing off the condensed liquid. A second condenser G is attached to D to condense the vapours escaping from D. The upper tubulure of G is connected with an aspirator to produce a slight draught. The flame should be a small one, and should be surrounded by wire gauze to prevent over¬ heating. The liquid drawn from the condensers contains the sulphur as sulphite and sulphate, which may be estimated by well-known methods. 1 Jour. Soc. Chem. hid. 1897, 167. Fig. 8. 2 Analyst , 1888, 43. IV PHOSPHORUS—CHLORINE—METALS 97 Similar contrivances have been described by Mabery, 1 Heusler , 2 Engler , 3 and Kissling . 4 Estimation of Phosphorus In order to determine phosphorus, as in fats containing lecithin, the sample is saponified with alcoholic potash ; the alcohol is eva¬ porated off, and the concentrated soap solution shaken out with ether in order to remove any cholesterol present. The soap solution is then decomposed by a mineral acid and the fatty acids separated from the acid liquid. The latter contains all the phosphorus as glycerol- phosphoric acid, C 3 H 5 (0H) 2 P0 4 H 2 . It is boiled down to dryness and the residue fused with potassium hydrate and potassium nitrate. The melt is then dissolved in water, and the phosphoric acid precipitated by magnesia mixture and weighed as pyrophosphate. On multiplying the P 2 0 5 found by 11‘366, the amount of lecithin, C 44 H 00 NPO 9 , will be obtained. Although the estimation of phosphorus will but rarely be made, it may serve in some cases for the identification of some fats, especially those obtained from leguminous seeds (see p. 7). Estimation of Chlorine Fats that have been bleached by means of chlorine may retain small quantities of this bleaching agent. Benedikt and Zikes 5 determine very small quantities of chlorine by allowing 25 grms. of the sample under examination to drop slowly from a separating funnel into a combustion tube filled with lime. The estimation is then carried out in the well-known manner of determining chlorine in organic substances. Detection and Determination of Metals Since fats possess the property of dissolving small quantities of metallic soaps, traces of metals are likely to be found in them. Especially the following bases may have to be tested for: Sodium and potassium hydrates, lime, alumina, lead oxide, copper oxide, ferric oxide, and zinc oxide. The alkali metals are tested for by the methods used in the analysis of soaps (see p. 776). Lime is sometimes fraudulently added to a fat in order to facilitate the incorporation of large quantities of water. On treating such a fat with petroleum ether the lime soap will remain undissolved, and is isolated by filtration. The residue on the filter is then incinerated, and the ash treated with dilute hydrochloric acid. After filtering, the filtrate is tested for lime by ammonium oxalate and ammonia. A white precipitate will prove the presence of lime. 1 Jour. Soc. Chem. Ind. 1895, 197. 3 Ibid. 1896, 383. 4 Ibid. 1896, 384. H 2 Ibid. 1895, 828. 5 Ibid. 1894, 984. 98 PREPARATION OF FATTY SUBSTANCE FOR EXAMINATION chap. For the quantitative estimation of lime proceed as above, but allow the precipitated calcium oxalate to stand in a moderately warm place for twelve hours, filter and dry the residue, and heat over the blowpipe until the weight of the calcium oxide remains constant. The determination of metals in a fat is best effected by warming the fat on the water bath with very dilute nitric acid in a porcelain dish ; they then pass into the acid liquid; or a somewhat large quantity of the fat may be incinerated in a platinum dish, the result¬ ing ash dissolved in a few drops of nitric acid, and the solution diluted with water. A less convenient process is to dissolve the fat under examination in ether, and to shake out with acidulated water. Part of the acid solution obtained by any of the preceding methods is tested with sulphuretted hydrogen, when the presence of a heavy metal will be indicated by the appearance of a black or brown precipitate or colouration. Other portions of the solution are tested (1) with potassium ferro- cyanide (brown precipitate), and with ammonia (blue colouration) for copper; (2) with sulphuric acid (white precipitate), and with potas¬ sium chromate (yellow precipitate, soluble in potash) for lead. For the detection and estimation of iron see below. Zinc and alumina are tested for by the well-known methods of qualitative analysis. Copper oxide is sometimes mixed with oils in order to impart to them a green colour. Rancid fats (as lard), when kept in copper or in lead-glazed vessels, may easily dissolve some copper or lead. The detection of these two metals in sweet oils and in culinary fats deserves, therefore, special attention. Quantitative Determination of Copper Weigh off accurately 10 to 20 grms. of the fat under examination in a platinum dish and incinerate. Dissolve the ash in a few drops of nitric acid, dilute with water, and filter into a beaker. Heat the solution nearly to the boiling point, add pure caustic soda or potash, and heat again for a few minutes. Filter off the black precipitate of copper oxide, dry, ignite, and weigh. Another process is to thoroughly stir the warmed fat with hydro¬ chloric acid, and pour the acid liquid through a filter; the fat is then washed several times with water; and the washings added to the main portion. Next the solution is heated whilst a current of sulphuretted hydrogen is passed through. The precipitated cupric sulphide is filtered off, washed with water containing sulphuretted hydrogen, dried, mixed with sulphur, and heated in a porcelain crucible in a current of hydrogen. The copper is thus transformed into cuprous sulphide, Cu 2 S. Quantitative Determination of Lead (1) The lead is brought into solution as lead nitrate by one of the methods detailed above. Dilute sulphuric acid is then added, IV DETECTION OF IRON 99 and the solution warmed on the water-bath until all the nitric acid has evaporated off. The remaining liquid is mixed with a little water and twice the volume of alcohol. After allowing to stand for a few hours the precipitate is filtered off, washed with dilute alcohol, dried, and ignited. The filter, of course, must be incinerated separately. The resulting lead sulphate is calculated to lead oxide or lead. (2) A more rapid, though less accurate method, is the follow¬ ing :—Burn off several grms. of the fat in a tared porcelain crucible. The residue, consisting of a mixture of metallic lead and lead oxide, is weighed first, and then treated with warm acetic acid to dissolve the lead oxide. The metallic lead is washed by decantation, and the crucible dried and weighed again, when the amount of metallic lead is found. The difference between the two last weights corresponds to the amount of lead oxide; it is calculated to lead, and the quantity added to that found for the metallic lead. (3) Shake the ethereal solution of the fat or oil with dilute sulphuric acid, filter, ignite the precipitate, and weigh as lead sul¬ phate. 1 Detection and Estimation of Iron Oils used for dyeing purposes and for currying leather should be free from iron. Alizarin oil, which contains about 15 to 20 per cent of free fatty acids, if kept in iron vessels, is especially liable to be contaminated, and the examination of Turkey-red oils for iron is therefore important. According to Emde 2 the following method will be found very convenient. A quantity of the oil is shaken up in a graduated cylinder with water acidulated with sulphuric acid. A few drops of potassium ferrocyanide are added, and the whole shaken up with a little ether. The oil dissolves in the ether, and forms a sharply- defined layer on the water. In the presence of iron, a more or less dense layer of Prussian blue, containing all the iron, will appear on the border line between the two liquids. If in comparative tests the same quantities of oil, water, acid, and potassium ferrocyanide be used, the thickness of the layer of Prussian blue may admit of a rough estimation of the quantity of iron. For accurate estimation it is of course necessary to precipitate the iron as hydrated ferric oxide and weigh it. 1 7. Preparation of the Insoluble Fatty Acids of a Fat for Examination The insoluble fatty acids being often required for analytical ex¬ amination, the method of preparing them may be described here once for all. 1 Fresenius and Schattenfroh, Jour. Soc. Chem. Ind. 1895, 895. 2 Jour. Soc. Chem. Ind. 1888, 591. 100 PREPARATION OF FATTY SUBSTANCE FOR EXAMINATION chap. A sufficient quantity of fat is saponified according to one of the methods already described, say by boiling 50 grms. with 40 c.c. of caustic potash solution, specific gravity 1 *4, and 40 c.c. of alcohol in a porcelain dish on the water bath with constant stirring until the soap becomes pasty. This is then dissolved in 1000 c.c. of water, and the solution boiled for at least three-quarters of an hour, when all the alcohol will be driven off. Sufficient water is added, if neces¬ sary, and the soap decomposed by means of sulphuric acid. When by continued boiling the fatty acids have been finally obtained as a clear oily layer, free from solid particles floating on the aqueous liquid, the mass is allowed to cool. In case the fatty acids solidify the cake is perforated by means of a glass rod, the acid liquid poured off, and the cake boiled several times with fresh quantities of distilled water, and finally dried. If the fatty acids remain liquid at the ordinary temperature, their separation from the water is effected by means of a syphon or of a separating funnel. On using a syphon it will be found most convenient, in order not to lose any fatty acid, to syphon off the aqueous layer by means of a filter-pump, interposing between the syphon and pump a strong bottle of about 2000 c.c. capacity, and fitted with a cork perforated with two holes. Both holes are provided with bent tubes, one of which Fig. 9. leads to the pump, whilst the other is connected by means of india- rubber tubing and a T piece with the syphon. To the other end of the T pipe is attached an india-rubber tubing, which is closed with the fingers while syphoning off. As soon as fat commences to enter the syphon the india-rubber tube is opened (Fig. 9). Provided the fat under examination is free from unsaponifiable matter, the fatty acids may be tested for any undecomposed fat by the following method proposed by Geitel. This test is necessary if the solidifying point of the fatty acids has to be determined. 2 grms. of the fatty acids are dissolved in 15 c.c. of hot alcohol, and 15 c.c. of aqueous ammonia are added. The mixture will become turbid if IV WEIGHING OF FAT 101 an appreciable quantity of neutral fat is present. If the solution has remained clear, cold methyl alcohol is allowed to run on to the top of the ammoniacal solution, forming a. separate layer. Traces of neutral fat are then indicated by a turbid zone appearing between the two layers. In the case of palm oil or deeply-coloured fats the last- mentioned test is of no avail, the turbid ring not being visible. 8. Weighing the Fat for Analysis Liquid fat is either weighed directly in the flask or vessel in which it is to be examined, or is poured out from a tared beaker or bottle, which should not be put on the pan of the balance without using a watch-glass. The quantity required is poured out (along a glass rod which may be tared with the beaker), and its weight determined by re-weighing. Solid or butter-like fats or waxes are weighed off in the same way. As they have, however, to be filled in the melted state into the beaker, this must be allowed to cool under a desiccator before weighing. The fat is melted again, the required quantity poured off, and the beaker, after complete cooling, re-weighed. If a small quantity of a solid fat is required, as for the determination of the iodine absorption value, it may be introduced by means of a glass rod into a thin-walled weighed glass tube about 4 cm. long and 1 cm. wide, open at both ends. I use for that purpose a somewhat larger filter - weighing bottle with hollow stopper, and place inside the bottle a wide glass tube drawn out into a capillary. This affords the further advantage of allowing approximately equal quantities to be employed for a number of tests by counting the number of drops. A similar contrivance has been recently described by Gantter. 1 Mangold uses a small pipette fitted with an india- rubber ball. The neck of the pipette is fastened, Fi g . io. by means of a piece of india-rubber tubing, to a perforated watch-glass, holding it thereby so tightly that it can be lifted up with it. This is placed in a beaker and weighed with it. By compressing the india-rubber ball and allowing it to expand, a small quantity of the oil can be made to rise in the pipette, and emptied by compressing it again. The apparatus is shown in Fig. 10. Essentially the same apparatus has been described by Hefelmann, 2 1 Cp. also Jour. Soc. Chem. Ind. 1894, 838. 2 Ibid. 1891. 862. CHAPTER V PHYSICAL METHODS OF EXAMINING FATS AND WAXES The examination of the physical properties of fats and waxes is in most instances a valuable aid towards identification. These properties and the determination of the constants involved will be described under the following heads :— 1. Consistency and Viscosity. 2. Colour. 3. Optical Refraction. 4. Rotatory Power. 5. Microscopical Appearance. 6. Electrical Conductivity. 7. Critical Temperature of Dissolution. 8. Specific Gravity. 9. Melting and Solidifying Points. 1. Consistency and Viscosity A comparative study of the consistency of fats and waxes is still wanting. Some authors classify the fats according to their consistency at ordinary temperature into— (a) Liquid (fluid) fats or oils; (b) Semi-solid fats, as lards and butters ; (c) Solid fats. The waxes are mostly solid and brittle at ordinary temperature. The first attempts to employ the determination of consistency for analytical purposes were made by Serra Carpi and by Legler; both authors proposed their method in the first instance for the examination of olive oil. Serra Carpi 1 cools the olive oil down to - 20° C. for three hours, and places on the solidified fat, by means of a suitable arrangement, a 1 Zeitscli.f. analyt. Ghem. 23. 566. CHAP. V CONSISTENCY — VISCOSITY 103 cylindrical iron rod 2 mm. in diameter and 1 cm. long, and conical at the bottom. Weights are then put on the rod until it sinks completely into the fat. Thus, for pure olive oil 1700 grms. were required ; a sophisticated oil required 1000 grms. only, whereas for cotton-seed oil 25 grms. were found to be sufficient. Whilst Serra Carpi examines the oil itself, Legler treats it previously with nitrous acid so as to produce the harder elaidin (see Elaidin Test, chap. ix. p. 280). He recommends the appa¬ ratus shown in Fig. 11. This consists of a strong , ... ^ glass tube A, in which a strong glass rod is allowed to slide. The rod is widened at a into a disc holding down the spring, which easily responds to a weight of 20-50 grms. placed on the top B. The point to which the glass rod slides down by its own weight is marked by 0 on the rod; from there upwards, marks indicating milli¬ meters are scratched into the rod. Substantially the same principle and the same apparatus have been recommended recently by BrullS 1 for the examination of butter, and by Sohn 2 The latter proposes three forms of apparatus, and lays down the following rules, which must be strictly adhered to if erroneous calculations are to be avoided :— ( 1 ) Pffl The rod must descend in an absolutely per¬ pendicular direction. (2) It must slide in its bearing with the least possible friction. (3) Conditions of temperature must be constant. (4) Vessels of one diameter must be used for the material under examination. (5) The rod must enter the centre of the vessel, or at a fixed distance from the circumference. (6) The same depth of material must always be used. (7) The material must be allowed to rest a certain fixed time before testing. Much greater importance attaches to the deter¬ mination of the viscosity of oils. This may be defined as the resistance the smallest particles offer to their separation from one another. The viscosity is therefore proportional to the internal friction of the oils, which by no means bears any relation to the density of the liquids. The determination of viscosity is based on Poiseuille’s law, which is expressed by the following formula:— Fig. 11. Mi = ir pr- 8 vl 1 Jour. Soc. Chern. Ind. 1893, 717. 2 Analyst, 1893, 218. 104 PHYSICAL METHODS OF EXAMINING FATS AND WAXES chai\ where is the coefficient of the inner friction or viscosity; the pressure on the unit surface of the orifice of the de¬ livery tube; the radius of the delivery tube; the length of the efflux tube; the volume of liquid that has passed through the apparatus in t seconds. law holds good only if the orifice is a capillary and as long The viscosity is usually determined by ascertaining the times two equal volumes of the liquids under comparison take to flow through a narrow aperture under exactly the same conditions. For a rough comparison, it may suffice to use a wide glass tube drawn out to a narrow aperture of about 2 mm., at the lower end, and having an upper and lower mark for the exact measurement of the volume of liquid. The earliest experiments are those carried out by Schubler, by means of a glass tube of 2 cm. diameter and 10 cm. height, having attached to it a narrow tube of 1‘6 mm. diameter. They are given in the following table :— as —. This 2 r Name of Oil. Number of Seconds required at Viscosity at +15° R. +7-5° R. +15° R. +7-5° R. Castor oil . 1830 3390 203-3 377-0 Olive oil . 195 284 21-6 31-5 Colza oil . 162 222 18-0 22-4 Winter rape oil . 159 204 17-6 22-6 Beechnut oil 158 237 17-5 26-3 White mustard oil 157 216 17-4 24-0 Almond oil 150 209 16-6 23-3 Summer rape oil 148 205 16-4 22-7 Pape oil 142 200 15-8 22-2 Mustard seed oil 141 175 15-6 19-4 Summer rubsen oil 136 198 15-1 22-0 Poppy seed oil . 123 165 13-6 18-3 Camelina oil 119 160 13-2 177 Sunflower oil 114 148 12-6 16-4 Peach kernel oil 93 132 10-3 14-7 Walnut oil' 88 106 9-7 11-8 Linseed oil 88 104 9-7 11-5 Hemp seed oil . 87 107 9-6 11-9 Distilled water . 9 9 1-0 1-0 On dividing the number of seconds required for an oil— e.g. 1830 —by that required for water at the same temperature— e.g. 9—a number is obtained termed specific viscosity, or in short, viscosity. Y VISCOSITY 105 Thus the viscosity of castor oil, according to Schubler, would be 18 ^ = 203-3 at 15° C. In practice the viscosity of oils is usually compared with that of rape oil. Redwood 1 has found from a number of tests carried out with refined rape oil by means of his apparatus, that 535 seconds may be considered as the average number occupied by the outflow of 50 c.c. of refined rape oil at 60° F. (15‘5° C.), the viscosity of water being under similar circumstances 25'5. Taking rape oil as a standard, and putting its viscosity = 100, the viscosity of any other oil under examination will be found by multiplying the number of seconds occupied by the outflow of 50 c.c. by 100, and dividing by 535. In case of the oil having a different specific gravity from that of rape oil—0 - 915 at 60" C.—a correction should be made according to Redwood by multiplying the result by the specific gravity of the sample, and dividing by 915. The formula is, therefore, if n be the number of seconds for an oil under examina¬ tion, and s its specific gravity— n x 100 x s u x 100 x s Viscosity = 535 x 915 - =--48952T Since, however, there is no correlation between specific gravity and viscosity (see above), I consider it more useful to adopt the numbers as obtained by direct determination of the viscosity. Engler uses water as a standard liquid, 200 c.c. taking 53 seconds at 20° C. to flow through his apparatus. If n be the number of seconds required by an oil under the same conditions, the 71 quotient —- will represent the specific viscosity of the oil. O o In order to obtain comparable results it is essential that com¬ plete uniformity of construction in apparatus be attended to. Pass¬ ing over a number of forms of apparatus that have been proposed from time to time, 1 2 we shall describe only three—those of Redwood Saybolt , and Engler. The first apparatus has been adopted by the War Department, the principal Railway Companies, and the Scottish Mineral Oil Association; the second is largely used in the United States ; and the third occupies, in Germany, a similar position to that of Redwood’s in this country. Redwood’s viscosimeter 3 (Fig. 12) consists of a silvered copper oil-cylinder C, about If in. in diameter, by about 3f in. in depth. The bottom of this cylinder is provided with an agate jet D, the cup- 1 Jour. Soc. Ohem. Ind. 1886, 127. 2 Dollfus, Dingl. Polyt. Jour. 153. 231 ; Vogel, ibid. 168. 267 ; Fisclier, ibid. 236. 487 ; Lamansky, ibid. 248. 29. Lamansky’s viscosimeter has been improved in the Nobel refineries at Baku, cp. Chem. Rev. fiber Fett u. Harz Industrie, 1897, 90. Lepenau, Zeitsch. f. ancdyt. Chemie, 24. 465. See also Redwood, Jour. Soc. Chem. Ind. 1886, 121 ; Mills, ibid. 1886, 148 ; Hurst, ibid. 1892, 418 ; Neumann Wender, ibid. 1895, 596 ; Killing, ibid. ; Redwood, Petroleum, 1896, vol. ii. pp. 602-620. 3 Jour. Soc. Chem. Ind. 1886, 126. 106 PHYSICAL METHODS OF EXAMINING FATS AND WAXES chap. shaped cavity of which can be stopped up by means of the plug E, consisting of a small silvered brass sphere attached to a wire. Inside the oil cup and at a short distance from the top there is fixed a small bracket F, terminating in a point. This serves as a gauge of the height to which the oil must be filled. A thermometer T is usually immersed in the oil and supported by means of a clip holding the V REDWOOD’S VISCOSIMETER 107 plug E. The cylinder C is surrounded with a copper jacket J, having a closed side tube K, by means of which the liquid in the jacket can be brought to any desired temperature. The heated liquid rising from K is uniformly distributed through the bath by means of a revolving agitator woi’ked by the handle EL The temperature of the liquid is controlled by the thermometer T. The whole instrument is supported on a tripod stand provided with level¬ ling screws. It is of the greatest importance that the orifice in the agate jet should be of a standard size, as slight variations in the size of the hole in various instruments are apt to give discordant results. The viscosimeter is employed in the following manner: The copper jacket is filled with water for temperatures up to about 95 C., and for higher temperatures with a suitable mineral oil, up to a height corresponding roughly with the pointer F in the cylinder C. The liquid in the bath having been heated to the required tempera¬ ture, the oil to be tested, previously purified and dried, and brought to the same temperature, is poured into C until its level just coincides with the point of the gauge. Great care must be taken that this level be reached exactly, and that the temperature remains constant during the observation. A narrow-necked flask, holding 50 c.c. to a point marked on the neck, is then placed beneath the jet in a vessel containing a liquid of the same tempera¬ ture as the oil. The plug is then raised, and the number of seconds required for 50 c.c. of the oil to flow out is care¬ fully observed by means of a chrono¬ meter. At least two tests of the same oil should be made at the same tempera¬ ture, and the two results should be very closely concordant if due care has been exercised. Allen 1 has modified Redwood’s viscosi¬ meter with a view to maintaining a given head of oil throughout the experiment. For this purpose the top of the oil-cylinder (Fig. 13) is fitted with an air-tight cap perforated by two holes, one of which is furnished with a tap B, while into the other a tube is screwed air-tight. This tube C is prolonged on two sides till it is in contact with the agate orifice, while the angles of the inverted Y-shaped slits, cut on each side, terminate at a definite height D above the orifice. The cylinder is completely filled with oil before commencing an experiment, the tap B closed, and the orifice opened till the oil sinks in the inner tube to the level D. Air then bubbles in regularly at D, and rises into the closed space above the oil, and when this is 1 Jour. Soc. Chem. Ind. 1886, 131. 108 PHYSICAL METHODS OF EXAMINING FATS AND WAXES chap. observed to happen, the oil is collected in a graduated cylinder. AVhen using this apparatus there is no necessity to collect exactly 50 c.c., because the oil runs through at a constant rate. Fig. 14. The same principle has been adopted by E. Schmid 1 for the im¬ proved Beischauer viscosimeter (see Fig. 14). Saybolt’s viscosimeter. 2 The oil vessel of this viscosimeter is placed 1 Chem. Ztg. 1885, 1514. 2 The description of this viscosimeter is taken from Redwood, Petroleum , vol. ii. p. 608. V SAYBOLT’S — ENGLER’S VISCOSIMETERS 109 in a water-bath of considerable capacity. The jet of the viscosimeter is of metal, and is enclosed in a tube extending below the orifice. The oil vessel is contracted, as shown (Fig. 15), above the jet, and is cut away longitudinally on each side, to expose a glass tube which lines it. Glass windows are provided in the water-bath. The upper edge of the oil vessel is fitted with an oil-tight gallery having a raised edge, and communicating with the oil vessel, which extends to the same level as the top of the gallery, by a number of small holes. In using the apparatus the water-bath is filled with water at the required temperature, and a cork having been inserted in the mouth of the tube enclosing the jet, the oil vessel is filled with the sample to be tested, until overflow occurs through the holes into the gallery. The oil is then stirred with a thermometer, and the temperature ad¬ justed if necessary. On withdrawing the thermometer, the oil which it had displaced flows back from the gallery, which is then emptied by means of a pipette. The length of the oil column is of course determined by the position of the holes connecting the oil vessel with the gallery The flow of oil from the jet is started by withdrawing the cork, and a stop-watch is set in motion. The watch is stopped when the operator sees the surface of the oil through the glass tube above mentioned. ... Enqler’s viscosimeter 1 in its latest form, as designed by him in conjunction with the officials of the Charlottenburg Mechamsch- Technische Versuchsanstalt, is shown in Fig. 16. The oil vessel A 1 Jour. Soc. Ohem. Iud. 1893, 292. - ■' I • 110 PHYSICAL METHODS OF EXAMINING FATS AND WAXES chap. is made of sheet brass, the inside of which should be gold-plated for very accurate determinations. This vessel is closed by a cover, A', perforated by two holes, into one of which the thermometer t is fitted, whilst the other serves to receive the plug b. The delivery tube a projecting from the convex bottom of the vessel A must be exactly 20 mm. long, and 2'9 mm. in diameter at the top and 2'8 mm. at the bottom. The delivery tube should preferably be made of platinum, as in course of time even brass is attacked by neutral oils. The plug b should be made of hard wood. The three pointers c serve the double purpose of indicating the correct level of the apparatus and of marking the exact volume of 240 c.c. The vessel A is jacketed, vessel B serving as a receiver for mineral oil, which may be heated up to 150° C. by means of gas supplied through tube d. As shown in the figure, this jacket also surrounds the delivery tube a, thus pre¬ venting loss of heat during the flowing of the oil. The instrument is fastened on to the tripod D. Beneath the apparatus is placed a flask C bearing two marks on the neck for 200 c.c. and 240 c.c. respectively. Engler lays the greatest possible stress on the necessity of strictly adhering to the measures given in Fig. 16, if correct results are to be expected. 1 In order to test the instrument, the time taken by the outflow of 200 c.c. of water at the temperature of 20° C. must be determined first. For this purpose clean vessel A with ether or petroleum ether, and rinse out with alcohol and water. Wipe out tube a by means of a feather or filtering paper, and close it with the plug b. Measure off, by means of the flask, C, 240 c.c. of water, and pour it into vessel A. This should then be filled exactly up to the level of the pointers c. Heat the mineral oil in B, if necessary, to 20° C., and wait until the water in A has attained the same temperature. In the meantime dry flask C and place it under the delivery tube a. Draw the plug and carefully note the time (by means of a chronometer) occupied in filling the flask C up to the 200 c.c. mark. It is most important that the water in A should be completely at rest before the plug is drawn. The time required should be from 51 to 53 seconds for a correct instrument, and repeated observation should not differ by more than 05 of a second. Before an oil is examined every trace of dirt and moisture must be removed from A by wiping it out carefully and rinsing it suc¬ cessively with alcohol and ether (or petroleum ether); finally it should be rinsed out with the filtered and dried oil. The oil is then poured into A up to the pointers c, and heated to the desired temperature, at which it must be kept for at least two or three minutes before allowing it to run out. 1 “The normal apparatus” is manufactured under the joint control of the Char- lottenburg Technische Anstalt and the Karlsruhe Chemisch - Teclmische Versuchs- anstalt, and may be also had from C. Desaga of Heidelberg. Apparatuses from other sources are, according to Engler , not made with the requisite care, and give discordant results. V ENGLER’S VISCOSIMETER 111 The following table gives a comparison of results based on a number of experiments with the three viscosimeters : 1 — Viscosimeter. Seconds for outflow of 50 c.c. at 70° F. 200 c.c. at 20° C. Redwood’s . 100 — Saybolt’s Engler’s 56 170 As will be seen, Engler’s viscosimeter requires much more time than either of the other two viscosimeters, and it has been proposed to shorten the observation by taking the number of seconds after 50 c.c. or 100 c.c. have run out, and multiplying the number of seconds by empirically found constants. 2 Surely, it would be simpler to use an apparatus based on the outflow of 50 c.c., like Redwood’s. As a rule, the viscosity of an oil destined to serve as a lubricant is determined at a temperature approximating to that at which the oil is actually used. The last-described viscosimeter not having been found suitable for observations at higher temperatures, Engler and Kiinkler 3 have designed a “viscosimeter for examination of oils under constant temperature.” This instrument is represented by Fig. 17. 1 Redwood, Petroleum , vol. ii. p. 610. 2 Singer, Chem. Rev. iiber die Fett u. Harz Industrie, 1897, 93, shows that the constants 5 for 50 c.c., and 2'34 for 100 c.c., give results agreeing with those found by allowing 200 c.c. to run out. J Jour. Soc. Chem. Ind. 1890, 654. 112 PHYSICAL METHODS OF EXAMINING FATS AND WAXES chap. It is an octagonal jacketed air-bath made of sheet brass, 35 cm. high and 20 cm. wide. The feet a stand in the ring of a tripod in such a way that the level of the air-bath can be adjusted so as to control the level of the liquid in the viscosimeter itself which is contained in the upper portion of the bath. In order to lose as little as possible of the heat supplied by a Bunsen burner, the flame is made to impinge on the arched copper plate b, isolated by a sheet of asbestos. Above this is placed the tripod c and the measuring vessel e, supported by d, and protected from direct radiation from b by the asbestos plate /. Above this is the dividing plate g, supporting the four oval tubes i and the viscosimeter k. Plate g is perforated by the large hole h, through which the oil flows into the measuring vessel. Circulation of hot air into the upper chamber takes place through h, and also through the four oval tubes i. Through the cover of the instrument pass the thermometers u, s, the axis of the stirring apparatus Avith the plug t for the delivery tube, and the jacketed funnel v for introducing the oil, previously heated to the required temperature in the can H, which is also provided with a stirring apparatus and a thermometer fixed in its hollow axis. In the cover and also in the sides windows l and m are let in, the latter permitting observations to be made of the level of the oil in the viscosimeter and of the flow of the oil into the measuring vessel e. The method of using the instrument and the manipulations required for making an observation need no detailed description. That the apparatus satisfies the required condition of constant tem¬ perature is proved by the following observation of its designers. If the viscosimeter—without any charge of oil in k —be heated to 100° C., the temperature in all parts of the bath is equal and constant, with the exception of the lowest stratum of air in k itself, owing, no doubt, to the absence of any circulation. This drawback, however, disappears with the introduction of oil. At temperatures exceeding 100° C., the air above the oil vessel has a somewhat lower tem¬ perature, but the difference does not amount to more than 4° C. at 150° C. 1 A description of Kionkler’s viscosimeter for the examination of small quantities of lubricating oils will be given in chap. xii. p. 723. Traube 2 condemns the viscosimeters described here on the grounds that, according to theory, it is not permissible to compare directly the respective times of delivery of heavy and light oils, and still less the times of delivery of oils and water observed in one and the same apparatus. For a description of the apparatus by which Traube proposes to replace the viscosimeters in use the reader must consult the original paper. 1 A similar principle is made use of in Marten's viscosimeter, Mitth. Konigl. Tech- nisch. Versuchsanst. Berlin, 1889, Erganzungslieft, Y. 6 . 2 Jour. Soc. Ghem. Ind. 1887, 414. V SPEOTROSCOPICAL EXAMINATION 113 2. Speetroseopieal Examination With the exception of palm oil, the more important fats and oils are whitish or yellowish; it is therefore impossible to detect any characteristic differences with the naked eye. On examining the fats, however, spectroscopically, characteristic absorption spectra are obtained. Although they are not due to the fatty substance itself, but to the presence of minute quantities of colouring matters, they serve in some instances to distinguish different oils. Thus an admixture of vegetable oils with those of animal origin may be detected by the characteristic absorption bands which chlorophyll produces. Olive oil and linseed oil give three absorption bands,—a very dark one in red, a faint one in orange, and a distinct one in green. Sesame oil pro¬ duces a weak band in red, whilst castor oil gives no bands at all. 1 Chautard has subdivided the oils into two classes, active and in¬ active, according as they absorb certain prismatic colours, or allow them to pass through unabsorbed. Doumer groups the oils, according to their speetroseopieal be¬ haviour, into four classes :— 1. Oils showing the spectrum of chlorophyll: olive oil, hemp seed oil, and nut oil. 2. Oils without any light-absorbing power : castor oil and almond oils. 3. Oils absorbing the “ chemical rays ” of the spectrum; the red, orange, yellow, and part of the green remaining unabsorbed. On examining such oils the spectrum from red to green appears, therefore, quite normal, whilst the other parts are invisible. To this class belong rape oil, linseed oil, and mustard seed oil. 4. Oils showing absorption bands in the different parts of the spectrum : sesam6 oil, arachis oil, poppy seed oil, and cotton seed oil. 2 Zune , who has resumed the study of the spectroscopic behaviour of oils, adopts Chautard’s classification. 3 3. Determination of the Refractive Power The results obtained by the refractometric examination of fats and oils cannot be considered as affording an absolutely reliable means of detecting adulterations. This becomes evident when we consider that a fat or oil is not a definite chemical compound, but a mixture of several chemical compounds, and that different specimens of the same oil may vary according to the treatment to which it may have been subjected in the process of refining, the age of the oil, the amount of free fatty acids, the amount of oxidation it has undergone, etc. 1 Vogel, Practische Spedralanalyse, 1877, 279. 2 Cp. Kenrick, Analyst , 1895, 136. 3 Analyse des Bmrres, II. 48. 1 114 PHYSICAL METHODS OF EXAMINING FATS AND WAXES ciiap. Fig. 18. Strohmer 1 thinks that the magnitude of the refractometric indices is so far influenced by the last-mentioned factors as to render them useless. This is, however, too sweeping an assertion. Eecent researches carried on by Muller , Skalweit, Amagat and Jean , JVollny, and others (cp. chap. ix. p. 262) have shown that valuable indications as to the purity of fats, especially of butter fat, may be gained from the determination of their refractive indices. Muller and Skalweit have used Abbe’s refractometer. In this instrument the index of refraction is found by observing the total reflection which a very thin stratum of a liquid placed between prisms of a more highly refracting substance produces in trans¬ mitted light. 2 A single drop of any fluid is therefore sufficient for the examination, however opaque that fluid may be in a thick layer. The'instrument 3 is shown in Fig. 18 and Fig. 19. The former illustrates the position in which the drop of the fat under examina¬ tion is applied ; the latter shows that position of the instrument in which the readings are taken. The instrument consists of a double prism of a highly refracting flint glass (Fig. 18) fixed to an alhidade in such a way that both admit of being turned round the centre of a divided arc. This arc has fastened to it a telescope turning with it on a horizontal pin. The elongated part of the telescope fits in 1 Zeitsch. f. Zucker Industrie, 1889, 189. 2 E. Abbe, Neue Apparate zur Bestimmung des Brechungs- und Zerstreuungsver- mogens fester und flussiger Kcirper. Jena, 1874. 3 Made by Carl Zeiss, Optische Werkstatte, Jena. V ABBE’S REFRACTOMETER 115 a support carrying a system of two revolving Amici prisms. This system acts as a compensator for achromatising the critical line of total reflection, the amount of rotation being indicated by a divided drum. The drop of liquid to be examined is brought between the two prisms, one of which can be removed easily as shown. In order to make this prism easily accessible, the telescope with the arc may be turned down. The examination may be made with diffused daylight or lamp¬ light, and consists in a single adjustment of the alhidade. The refrac¬ tive index is read directly off the divided arc to the third decimal, no calculation being necessary. The fourth decimal may be estimated accurately within two units. 116 PHYSICAL METHODS OF EXAMINING FATS AND WAXES chap. For the examination of butters Reiss’s butyro-refractometer (Fig. 20) has been recommended by Wollny. This instrument differs from those previously described, in that the critical line of total reflection for a certain substance—in this case butter—is achromatised, not by a special compensating arrangement, but by the refractometer prisms themselves, the dispersion co-existent with the total reflection between glass and substance being exactly compensated by the dispersion due to the surface when the light emerges from the double prism in the direction of the telescope. Accordingly, the critical line appears colourless Fig. 20. (achromatised) for the standard substance for which the prisms have been calculated, whilst all substances differing from the standard in refractive and dispersive power cause the critical line to appear more or less blue or red. This latter line, however, is in all cases sufficiently distinct to admit of its exact position being ascertained. Thus two different substances are not only distinguished by the different positions of the critical line, but also by the difference in its appearance. The prisms of the butyro-refractometer being specially calculated for pure butter, sophistications of that article of food may be easily detected by a simple examination under this instrument. V PULFRICH’S REFRACTOMETER 117 The same instrument could, of course, be adapted just as well to the refractometric examinations of other fats and oils, and also for ascertaining the proportion of water in solutions of glycerol. The butyro-refractometer will be more fully described under “Butter Fat” (chap. xi. p. 625). Thorner 1 recommends the use of the refractometer designed by Pulfrich , 2 provided with a special arrangement (which is also supplied with the refractometers just described) for determinations at higher temperatures. Pulfrich ’s refractometer 3 is shown in Fig. 21. The observations are made with sodium light, placed opposite the reflecting prism N, or with hydrogen light, emanating from the Geissler tube Q. The 1 Jour. Soc. Cliem. Ind. 1889, 308. 2 C. Pulfrich, Das Totalreftedometer und das Refractometer fur Chemiker, etc. Leipzig, 1890. 3 Made by Carl Zeiss, Optisclie Werkstiitte, Jena. Fig. 21. 118 PHYSICAL METHODS OF EXAMINING FATS AND WAXES chap. sodium light is thrown by means of the reflecting prism N, the hydrogen light by means of the condenser P, on to the substance under examination. (The illumination can be changed rapidly from one source of light to the other by displacing N.) The substance is placed direct on to the surface of the refractometer prism in the Fig. 23. manner illustrated by Fig. 22, and the prism, together with the sub¬ stance, can be brought to any desired temperature in a special heating apparatus S (Fig. 23) by allowing the heating liquid to flow in the direction indicated by the arrows. The piece of wood W (Fig. 21) serves to prevent loss of heat. The light falling into the substance to be examined under grazing incidence passes through the vertical face of the 90° prism, and the angle i at which the limiting ray emerges from the vertical face is read off by means of a telescope and graduated circle. The refractive index n of the substance is calculated by means of the formula n= JW - sin 2 i where N is the (known) refractive index of the prism. Whilst Abbe’s and Pulfrich’s refractometers allow of the scientific determination of the refractive index of a substance, the apparatus recommended recently by Amagat and Jean for the examination of V OLEO-REFRACTOMETER 119 fats and oils, and especially for testing butter, is an instrument based on an entirely arbitrary scale. This instrument, called by its designers oleo-refractometer (Fig. 24), consists essentially of a collimator, a telescope, and a metallic vessel. The latter is fitted with parallel plate-glass sides, and its position to the collimator and telescope is fixed in such a way that a ray of light entering through the collimator must pass through the plate-glass sides and the telescope. In the centre of the metallic vessel a small hollow silver cylinder A with two plate-glass ends is inserted, arranged so as to form an angle of 107°. The telescope is furnished with an arbitrary glass scale, placed in the focus of the eye-piece, on which is thrown the image produced by a semicircular stop inserted in the collimator, thus dividing the field into a dark and light portion. Supposing the silver cylinder and the outer circular vessel be filled with the same oil, there will be no refraction, and consequently no alteration in the position of the image. If, however, the interior silver cylinder be filled with a different oil, there will be refraction depending on the nature of the oil, and consequently the line dividing the field will be displaced to the right or left. The amount of displacement is read off the scale of the telescope, and is expressed by the number of scale divisions or “ degrees.” For practical use the outer vessel is filled with a standard oil (huile type) [the composition of which is, curiously enough, kept secret by the inventors 1 ; it must be bought with the instrument], and the semicircular stop so adjusted that the line dividing the field into a dark and light portion falls on the zero point of the scale. The interior cylinder is then filled with the oil under examination, and the displacement of the dividing line, i.e. the amount of refrac¬ tion, read off. Instead of using the “ standard oil ” it is, of course, possible to compare a sample of oil with a sample of the same kind known to be pure. For the sake of greater convenience in practical use both the cylindrical vessel and the silver cylinder can be emptied (and washed out) by means of taps, one of which only, R, is shown in Fig. 20. Besides, a water-jacket surrounding the centre part of the instrument 1 The “huile type” is sheep’s-foot oil. 120 PHYSICAL METHODS OF EXAMINING FATS AND AY AXES chap. (not shown) allows the temperature of the oil under examination to be regulated. The water in the jacket can be heated by means of a lamp to any desired temperature, which is indicated by a thermo¬ meter. Amagat’s and Jean’s oleo-refractometer has that advantage over Abbe’s refractometer that, being a differential apparatus, it allows of a rapid determination of the difference of two oils, which are being compared, under exactly the same conditions. 1 The application of, and the results obtained by the refractometric method will be fully discussed under “Liquid Fats” (chap, ix.), “Lard,” “Butter Fat” (chap, xi.), “Commercial Oleic Acid,” and “Glycerol” (chap, xii.) 4. Rotatory Power of the Plane of Polarisation Vegetable fatty oils, with the exception of castor oil, were generally supposed to be optically inactive, until Bishop 2 showed that several rotate the plane of polarised light slightly. The instrument used by him was a Laurent’s saccharimeter having a 20 cm. tube. The following table gives that author’s results :— f n ,, Rotation in Saccharimeter. jvinci oi uu. Degrees. Sweet almond oil . . . . — 0'7 Aracliis oil . . . . . -0‘4 Colza (French) oil . . . . . -2’1 ,, (Japanese) . . . . —1'6 Linseed oil . . . . . -0‘3 Walnut oil ...... -0.3 Poppy seed oil ..... -0 - 0 Olive oil . . . . . . +0 - 6 Sesame oil, cold expressed . . . . + 3’1 ,, ,, warm expressed . . . + 7'2 ,, ,, 1878 ..... +4-6 ,, „ 1882 ..... +3-9 ,, ,, 1882 ..... +9'0 ,, ,, Indian . . . . +7‘7 Peter , 3 who has also examined a number of oils by means of Laurent’s saccharimeter, finds that almond, rape, hemp seed, linseed, and poppy seed oils are lsevo-rotatory, whilst some samples of arachis oil were dextro-rotatory, others again Isevo-rotatory. But with re¬ gard to almond, rape, linseed, arachis, and poppy seed oils Thoernerf who examined these oils in a 20 cm. tube in JFild’s Polaristrobometer, leaves it open to doubt whether definite rotation occurs. The same chemist gives for castor oil and sesam6 oils the numbers + 6 - 4° and + 1'0° respectively. 1 Allen (Analyst, 1895, 135) points out that the angle of the prism is not strictly the same in all instruments, he having found for a sample of lard in 3 instruments 4v,°, 6°, and 11° respectively. 2 Jour. Soc. Chem. Ind. 1887, 750. 3 Bull. Soc. Ghim, 1887, 483. 4 Jour. Soc. Chem. Ind. 1895, 43. V MICROSCOPICAL EXAMINATION 121 Olive oil, more than a hundred samples of which have been examined, rotated the polarised light to the right. This is not con¬ firmed by Thoerner’s observations. The high angles observed for the dextro-rotatory croton and castor oils are remarkable. Walnut oil was found to be inactive, and hazelnut oil lsevo-rotatory. Fatty acids, according to Peter , have the same optical activity as the oils from which they have been derived. This has been con¬ firmed by Thoerner for castor oil and sesam6 oil fatty acids, and by Walden for the former oil. It is very likely that, with the exception of castor oil, whose rotatory power is due to the asymmetric carbou-atom of the ricinoleic acid, the rotatory power is not due to the glycerides themselves, but to small proportions of optically active substances, such as cholesterol. In the case of sesam6 oil, at all events, the optical activity must be due to cholesterol and sesamin (chap. xi. p. 389). As such sub¬ stances are isolated together with the fatty acids, the optical activity of the fatty acids is readily explained. 5. Microscopical Appearance The use of the microscope for the examination of fats and the recognition of adulterations has been repeatedly recommended by a number of authors, of whom we may mention Taylor , Brown , Hehner and Angell , Mylius, Skalweit, and Wiley. For this purpose the fat should be dissolved in ether, or chloroform, or carbon bisulphide, or petroleum ether, and a few drops of the solution allowed to evaporate on the object glass. Butter fat, beef tallow, mutton fat, and lard show characteristic crystals. According to Long the best results are obtained with chloroform as a solvent. Diagrams showing the microscopical appearance of a number of fats will be found in Zune’s Analyse des Beurres. The appearance of the crystals in polarised light is specially characteristic. This method of examination is, at present, coming more to the fore (cp. Beef Fat in Lard, p. 582). The application of the polarisation microscope to the examination of oils and fats is, up till now, more restricted still. 6. Electrical Conductivity The determination of the electrical conductivity has been proposed by Palmieri 1 as a means of detecting the sophistication of olive oil. For this purpose he has constructed a special apparatus called a diagometer. Recently A. Bartoli 2 has made an extensive examination of the electrical conductivity of oils and fats, of which the following are the main results. The conductivity of an oil increases with the rise of temperature, its amount, however, varying with the nature of the oil. 1 Rend, della Ace. di Napoli, 1881. 2 11 nuovo Cimento, 1890, tomo 28. 25. 122 PHYSICAL METHODS OF EXAMINING FATS AND WAXES chap. The drying oils, when exposed to the air, acquire a greater con¬ ductivity than the non-drying oils. An increase, though to a smaller extent, is also observed in the case of the latter, when they become rancid. A table, arranged according to the magnitude of the electrical conductivity, begins with purest olive oil, and ends with linseed oil. The solid fats exhibit the same phenomenon, viz. increase of conductivity at elevated temperatures, with the exception of lard, at temperatures from 170° to 220° C. Nutmeg butter is characterised by a sudden increase at the temperature of its melting point. A similar table of conductivities for the solid fats opens with chicken fat, and closes with nutmeg butter. The measurement of the electrical conductivity of the potash soaps obtained by saponifying the fat or oil under examination is proposed by L. Herlant} It is, of course, essential to employ in each case the same amount of fat and alkali, and to dilute the solutions to exactly the same strength, and also to make all observations at one and the same temperature. For the examination 10 grms. of a fat or oil are mixed in a flask with 45 c.c. of pure normal alcoholic potash and saponified by heating for thirty minutes on the water bath, the flask being attached to a reflux condenser. The alcoholic soap solution is then made up with distilled water to 250 c.c. and electrolysed. The resistance which a cube with a side of 1 cm. filled with the solu¬ tion offers is the specific resistance r of this solution, and its inverse ratio — expresses its specific conductivity. For practical purposes compari¬ son is made with the specific conductivity of a norm, solution of potassium chloride, for which = 0 - 002244 at 18° C. If K be a coefficient depending on the trough, then we have for the potassium chloride solution — K = 0‘002244, and for the specific conductivity of any other solution in this trough l = ~ x K. 7. Critical Temperature of Dissolution The determination of the critical temperature of dissolution as a physical constant is proposed by Crismer. 2 This physical constant is analogous to the critical temperature of gases, and denotes the temperature above which a fat and alcohol (of a certain strength) form a homogeneous mixture. 1 Jour. Soc. Chem. Ind. 1896, 562. 2 Bulletin de VAssoc. Beige des Chimistes, 1895, ix. 71, 143 ; 1896, ix. 359 ; x. 312. V CRITICAL TEMPERATURE OF DISSOLUTION 123 Crismer places a few drops of the oil or melted fat in a glass tube 9 cm. long and 5-6 mm. wide, and adds about twice the volume of 90 per cent alcohol. The tube is then sealed and fixed by means of a platinum thread to the bulb of a thermometer, and heated in a bath of sulphuric acid or glycerin, until the meniscus separating the two layers has become flattened into a plane. After heating a little longer, so as to allow the temperature to rise, say, another 10° C., the thermometer is withdrawn from the bath and sharply turned several times. It is then replaced in the bath and the tube observed carefully, whilst the thermometer is being gently shaken. The temperature at which a marked turbidity appears is recorded as the critical temperature of dissolution. If the critical temperature does not exceed the boiling point of alcohol, 78° C., an open tube may be used in place of a sealed one. Thus in the case of butter fat 0 - 5 c.c. of the filtered fat is placed in a tube 7 to 8 cm. long and about 1 cm. in diameter, with twice its volume of absolute alcohol. The tube is provided with a cork, fitted with a thermometer, the bulb of which is immersed wholly in the liquid on inserting the cork into the tube. The tube is gently heated in a larger tube, serving as an air or water bath, whilst by agitating the contents vertically a homogeneous liquid is obtained. The mixture is then allowed to cool, and the critical temperature is determined as described above. This method has been used hitherto chiefly in the examination of butter (chap. xi. p. 628). The critical temperatures of dissolution of mixture is, according to the same author, approximately the arithmetical mean of those of its constituents; it may be calculated from the following formula :— T _?iT„ + (100 - n) Tj m 100 where T m = the critical temperature of the mixture. T a = the critical temperature of the constituent a. T & = the critical temperature of the constituent b. « = the volume of constituent a in 100 volumes. 100 - ?t = the volume of constituent b in 100 volumes. As a further deduction from the experiments made hitherto, the rule has been derived that substances of the same nature have practic¬ ally the same critical temperature of dissolution. 8. Determination of the Specific Gravity 1 The specific gravity of the liquid fats and waxes may be ascer¬ tained at the ordinary temperature by the well - known methods adopted for any other liquid, viz. by means of a hydrometer, picno- meter, or the hydrostatic balance. 1 Instead of weighing a definite volume, Zaloziecki measures the volume of fatty acids yielded by a known weight of fat (cp. p. 623). 124 PHYSICAL METHODS OF EXAMINING FATS AND WAXES chap. It is hardly necessary to emphasise the importance of making sure of the accuracy and delicacy of the hydrometer to be used. The readiest indications will be obtained by means of hydrometers refer¬ ring to the density of water, whilst the use of Twaddell’s hydrometer involves a calculation, simple though it be. On the Continent and in America various hydrometers, based on an arbitrary scale, are used in commerce and still employed by the custom-house officials. These hydrometers, gauged for a certain temperature, express the densities in “degrees”; the real specific gravities s can be calculated by means of the subjoined table, n being the number of “degrees.” Hydrometer. Temperature. For Liquids heavier than Water. For Liquids lighter than Water. Balling 17-5° C. 200 200 200 - n S 200 + n Baume I 12-5° C. 144 T _ 144 144 -n 144 + 71 Baume II . 15° C. 144-3 144-3 ’ 144-3 - n 144‘3+ti Baume III . 17-5° C. 146-78 146-78 146 "78 -n 5 146-78 + Beck . 12-5° C. HO 170 170 — w 170 + ti Brix . f 12-5° B. 400 400 1 15-625° C. 400 - n 400 + 7i Cartier 12-5° C. 136'8 136-8 S 126 "1 -n S 126-1+ti Fischer /12-5° R. 400 400 \ 15-6-25° C. 400 - n 400 + 7t Gay-Lussac . 4° C. 100 s— — n _100 n E. G. Greiner /12-5° R. 400 400 f 15-625° C. 400 - n S 400 + 71 Stoppard f 12-5° R. 166 166 \ 15-625° C. 166-71 166 + 71 n „ 77+100 Twaddell . z b ~ 100 Hydrometers should only be employed where rapidity is of greater importance than accuracy. Specific gravity is usually determined by means of a picnometer of one kind or other. Of these the ordinary specific gravity bottle, consisting of a plain flask with a stopper having a capillary perfora¬ tion, will be found useful for commercial work, and with care even the fourth decimal may be determined accurately. Such a picno¬ meter is preferable to an ordinary 100 c.c. flask, as proposed by Stohmann, inasmuch as a smaller quantity of oil is required, and much greater accuracy in adjusting the volume is obtainable than in V SPRENGEL’S PICNOMETER 125 the somewhat wide-mouthed 100 c.c. flask, although in the latter case it is only necessary to weigh the flask accurately to the first decimal. The greatest degree of accuracy is obtained by means of Sprengel’s picnometer (Fig. 25). This is a U-tube made of thin glass, ending in two capillary tubes a and b bent at right angles and ground at their ends, so as to fit into two glass caps (the latter are not shown in the figure). The inner diameter of tube b, bearing the mark m, is about 0‘5 mm., whilst that of tube a is less, and should not exceed 0-25 mm. 1 The tube is filled by connecting a with a glass bulb, and sucking the air out of it by means of india-rubber tubing whilst b is im¬ mersed in the oil under examination. If the glass bulb be chosen sufficiently large, the Sprengel tube will be filled automatically on closing the india - rubber tubing with the fingers. As soon as the oil enters the bulb the Sprengel tube is detached from it, and the picnometer allowed to assume the desired temperature (see below). It will be found that the liquid expands or contracts in the tube b only , i.e. in the direction of the least resistance, whilst the capillary tube a will always remain full. If the meniscus of the liquid is found to be beyond the mark m, a little of the oil can Fig. 26. be abstracted by means of a roll of filter-paper applied to the end of a; if, however, the tube contains too little, a may be touched by 1 This point should be noted, as this essential feature of the Sprengel tube is lost sight of by some makers. 126 PHYSICAL METHODS OF EXAMINING FATS AND WAXES CHAP. a glass rod which has been dipped into the oil, thus allowing some to be sucked in by the capillary tube, the liquid moving forward in tube b. Thus the exact volume can be adjusted easily. Finally, the two glass caps are put on the tubes a and b, and the picnometer is then ready for weighing. Mohr's or the hydrostatic balance is not so accurate, but still quite satisfactory for ordinary purposes, and is largely used on account of the convenience and rapidity of the operation. One form of this instrument is shown in Fig. 26, and requires no further explanation. 1 The plummet, it may be added, displaces exactly 10 c.c., and therefore the weights put on the lever to restore equilibrium Fig. 27. are exactly the weight of 10 c.c. of the substance. Thus all calculation is avoided, the specific gravity being read direct from the weights used. For the determination in the case of viscous oils (as boiled oil) at ordinary temperature the picnometer described by Bruhl (Fig. 27) is useful. A pipette containing the viscous substance is inserted air¬ tight in the flask by means of an india-rubber tube, and the air exhausted by connecting the side tube with a filter pump. In specific gravity determinations great care must be taken to ensure the oil having the same temperature throughout its entire mass. For this purpose it will be found best, after having brought the oil to the standard temperature, to keep it for some time in a sufficiently large water-bath. The temperature should be observed by means of an accurate thermometer. The standard temperature in this country is 60° F. = 15‘5° C. The weight of the volume of oil should be compared with that of an equal volume of water taken at the same temperature. It is customary to consider the weight of that volume of water at 15‘5° C. as unity. Thus the specific gravity of rape oil is usually stated as 0‘915 at 15‘5° C., water at the same temperature = 1. In exact work the weight should be reduced to that in vacuo and referred to water at 4° C. (cp. chap. xii. p. 794). Obviously the determination of the specific gravity of those fats and waxes that are solid or semi-solid at' the standard temperature leads to complications and difficulties (see below). They are avoided by adopting as the standard a convenient temperature at which the substances are in the fluid state. Bell and Muter proposed the temperature of 100° F. = 37'75° C., whilst Estcourt , Archbutt , Konigs, Skalweit, and others recommend the temperature of boiling- water. Leune and Haburet, Konigs , and Adolf Mayer determine the specific gravity at 100° C. by means of the hydrometer. Konigs has modified the method originally proposed by Estcourt , 1 Cp. Thorner, Jour. Soc. Chem. Ind. 1895, 44 (Illustration). V SPECIFIC GRAVITY 127 and recommends the apparatus shown in Fig. 28. This is a water- bath provided with an arrangement to keep the water at a constant level, and is closed at the top by a cover perforated with five holes. The centre hole forms an outlet for the steam ; in the other four holes there are fitted, by means of india-rubber rings, so that they protrude about half an inch above the cover, four test-tubes 8 to 9 inches long, \\ inches wide. The specific gravity is taken by means of a hydrometer about 5^- inches long. This apparatus was designed, and is used in Germany, especially for the examination of butter; in order to eliminate errors due to slight variations of temperature, etc., and to ensure completely com¬ parable conditions, one tube is filled with the sample of butter under examination, whilst the other three are charged severally with tallow, oleomargarine, and genuine butter fat. If the temperature of exactly 100° C. be required, the steam outlet tube must be partly closed. The accuracy of determinations under such conditions will largely depend on the accuracy of the hydrometers used. For this reason alone this method cannot be recommended. Skalweit’s method is more accurate. He uses a specific gravity bottle; but as there are many inherent errors in this method, for determination at the boiling point of water it will be found best to use a Sprengel tube. The Sprengel tube is immersed in boiling water in such a way that only the ends of the capillary tubes protrude. After about twenty minutes’ boiling the glass caps are placed on the ends, the Sprengel tube is removed from the water-bath, wiped dry, and weighed after cooling. The weight of the oil may be referred to the weight of water at the boiling point, or, as has been done by most observers, to the weight of water at 15'5° C. The unity chosen must, of course, be distinctly stated. The correct method would be, of course, to take water at 4° C. as unity. Whilst the hydrostatic balance may be found very convenient at the ordinary temperature, its employment at higher temperatures, as proposed by J. Bell and by Wolkenliaar, necessitates the use of a somewhat complicated arrangement. That recommended by Bell is shown (partly in section) in Fig. 26. It is designed for the tempera¬ ture of 100° C. D is a glass tube containing the sample of fat; C is filled with paraffin wax, and is surrounded by the water-jacket H. 128 PHYSICAL METHODS OF EXAMINING FATS AND WAXES chap. In cases where, for some particular reason, neither of the two temperatures 15-5° C. nor 100° C. can be employed, a correction must be made, depending on the coefficient of expansion of that particular oil. Allen 1 has determined the rate of expansion of a number of fats by taking their densities at 98° C. and 15‘5° C., and dividing the difference of the densities by the difference of the temperatures. Thus he obtains the correction to be made for a variation of 1° C. Although this method is not scientifically correct, inasmuch as it rests on the assumption that the rate of expansion does not vary between 15'5° C. and 98° C. [the mean coefficient of expansion differs from the true one as the quotient of differences from the differential quotient], the values obtained by Allen will satisfy practical requirements. Excepting whale oil, which possesses an abnormal rate of expansion, the correction for 1° C. has been found to vary for seventeen kinds of fats between the limits 0-000615 and 0-000665. Therefore Allen proposes to take as the mean correction for one degree Celsius 0-00064 (or for one degree Fahrenheit 0-00035). Thus, if the density of an oil is 0'9207 at 22° C., its density at 15’5° C. will be found by the following calcula¬ tion. The difference of the temperatures is 22-15-5 = 6'5; the correction is therefore 6"5 x 0"00064 = 0"00416. This figure added to 0‘9207 gives 0‘92486 as the specific gravity at 15-5° C. The coefficient of expansion of an oil may also be found by this “picnometric method” by dividing the correction for one degree of temperature by the specific gravity of the oil at the lower temperature. But it should be borne in mind that the volume of the picnometer varies with the temperature, and that it is therefore necessary to make a correction for the expansion of the glass. Several methods have been proposed for the determination of the specific gravity of solid fats and waxes at ordinary tempera¬ tures. Although it is far more convenient, as explained above, to use a higher temperature, a few of these methods may be described here. Gintl 2 uses the picnometer shown in Fig. 29. It consists of a small cylindrical, flat-bottomed vessel, I, made of very thin glass and provided with a ground-glass cover. The vessel fits into the frame a (Fig. 30), the screw b serving to press the glass cover tightly on the cylinder. The vessel is weighed empty and afterwards when filled with water at the standard temperature. After emptying the water and drying carefully, I is filled with the melted fat until quite full, and allowed to cool to the standard temperature. The glass cover is then carefully placed on /, so that the surplus fat is squeezed out, and secured in its position by means of the screw. The fat outside is washed off by means of ether and the vessel weighed again. Wynter Blyth z proposes to weigh the fat in a glass tube, containing besides the substance some mercury or shot, first in air and afterwards 1 Commercial Organic Analysis, ii. 19. 2 Dingl. Polyt. Jour. 194. 42. 3 Analyst, 5. 76. V SPECIFIC GRAVITY 129 under water at lS'S 0 C. From these data the specific gravity may be calculated. R. JVagner, Hager , and other authors, favour the method proposed originally by Fresenius and Schulze , which we describe in the form given it by Hager. This chemist melts the solid fat or wax at a temperature below 100° C. in a capsule, and allows several drops to fall from a height of 2-3 cm. into cold 60-90 per cent alcohol, forming a layer of 1 '5-2 cm. depth in a flat-bottomed dish. Each drop should fall on a different place, so that a number of globules may be obtained. They are fished out with a spoon and placed in a beaker or a bottle 4 cm. wide and Fig. 29. Fig. 30. 6-7 cm. high, containing dilute alcohol. To the latter either alcohol or very dilute alcohol (but not water alone, so as to avoid air-bubbles), as the case may be, is added until the fat globules will just float in the liquid. The specific gravity of the fat is then exactly the same as that of the liquid, the density of which may be determined (after filtration through glass-wool) by one of the foregoing methods. Chattaway and Allen 1 take exception to the accuracy of Hager's method on the ground that a solid fat, and especially wax and spermaceti, suffer an abnormal contraction owing to the sudden cooling when dropped into the dilute alcohol. They found, however, that this source of error is eliminated if the wax is melted on a watch-glass placed on boiling water, and small pieces are cut from the spontaneously cooled mass. They are next brushed over with a wet brush in order to remove adherent air-bubbles, and carefully placed in dilute alcohol by means of a pair of forceps. Dieterich, however, has shown that Hager’s method yields reliable results if the following procedure be adopted. A somewhat large piece of wax is allowed to 1 Commercial Organic Analysis, ii. 184. K 130 PHYSICAL METHODS OF EXAMINING FATS AND WAXES chap. melt at its edge by holding it near a spirit lamp, and as close as possible to the surface of some alcohol contained in a flat-bottomed capsule, so as to avoid air being enveloped by the falling drops. The wax globules are placed on blotting paper and allowed to remain there from eighteen to twenty-four hours. Ten or twelve of the globules are then brought successively into eight standard mixtures of alcohol and water, having the specific gravities—at 15‘5 C.—of 0’960, 0*961, 0*962, and so on up to 0*967, until that liquid has been found in which the wax globules will just float. Should any of the globules hold some air enclosed they will behave differently from the rest, and should be removed. It is hardly necessary to add that moist wax should be dried previously, say, by melting over Glauber’s salt and subsequent filtration. A somewhat complicated apparatus for the determination of the densities of soft fats has been proposed by Zawalkiewicz. 1 9. Melting and Solidifying Points Various methods have been proposed for the determination of the melting points of fats. Unfortunately they lead to discordant results. Nor is this to be wondered at if we remember (see p. 4) that even the pure glycerides, tripalmitin and tristearin, present in their melting points irregularities such as are not shown, as a rule, by definite chemical substances. It is therefore unlikely that fats, being mixtures of several glycerides, will give definite melting points. 2 There is also a good deal of uncertainty as to which of the two temperatures should be taken as the melting point, whether that at which a fat commences to liquefy, or that at which it has become perfectly transparent. Some experimenters identify the melting point with the temperature at which the fat undergoes a certain degree of softening, either sufficient to suffer a plug of fat, contained in a glass tube open at either end, to be forced up by the hydrostatic pressure of water, or to allow the fat to form a globule. The want of a uniform method for the determination of the melting point is therefore much felt, and one that would command general acceptance is still a desideratum. It should be borne in mind that fats do not possess their normal melting point shortly after being melted. It is only recovered after the lapse of a day or two ; therefore if a sample has been melted it should be allowed to stand some time before the melting point is determined. On the Continent Pohl’s method is largely employed. This chemist ascertains the temperature at which a fat is just becoming liquid, although it may still retain solid particles. The bulb of a mercury thermometer is immersed in the melted fat and quickly removed, so that a thin coating only of fat adheres to it. After a day or two the thermometer is fixed into a long and wide test-tube by means of a cork, so that the bulb is still at a distance of about half an inch from 1 Jour. Soc. Chem. Ind. 1894, 839. 2 Cp. also Bevan, Jour. Soc. Chem. Ind. 1894, 70 ; and chap. i. p. 3, footnote 2. V MELTING POINT 131 the bottom. The test-tube is then fastened in a clamp and gently- warmed by the heat radiating from a heated sheet of iron or asbestos placed below it at a distance of about one inch. The temperature is allowed to rise only very gradually. The moment a drop of liquid fat is observed to form at the bottom of the bulb the temperature is read off and recorded as the melting point. A somewhat modified form of the same method has been intro¬ duced by Redwood. A very minute quantity of the melted fat, nearly cooled to its solidifying point, is placed by means of a thin glass rod on clean mercury contained in a small dish and allowed to solidify. The dish may be placed in a beaker containing water, which is heated very gradually. A thermometer is dipped in the mercury, and that temperature recorded as the melting point at which the fat spreads over the mercury. Frequently the melting point is ascertained in a very thin capillary tube, as usually employed for organic substances. The “ Society of Bavarian Analytical Chemists ” have agreed upon the following modus operandi: —Draw up the melted fat into a thin-walled capillary tube 1 or 2 cm. high, corresponding to the length of the bulb of the thermo¬ meter to be used; seal one end of the tube, and attach the latter to the stem of the thermometer in such a way that the substance and the mercury bulb are at the same level. After an interval of about twenty- four hours immerse the thermo¬ meter in glycerin contained in a test-tube about an inch and a half wide, and heat the liquid very gently. The temperature at which the thin cylinder of fat has become perfectly clear and transparent should be con¬ sidered as the melting point. Olberg has designed an apparatus (Fig. 31) adapted for this method. The vessel is filled with oil, and on this being heated at A a natural circulation takes place without requiring any stirring. Bensemann 1 determines two points, viz. the point of incipient fusion and the point of complete fusion. A drop of the melted fat is placed in a tube as shown in Fig. 32, a, and allowed to solidify in such a position that it forms a globule at A. The tube is then attached to a thermometer and immersed in water contained in a beaker. By gently warming the water over a very small flame a point is reached when the fat is just beginning to flow down the side 1 Jour. Soc. Chem. Ind. 1885. 535. 132 PHYSICAL METHODS OF EXAMINING FATS AND WAXES chap. of the tube. The temperature at which this takes place is recorded as the “ point of incipient fusion.” The drop of fat will then have taken the position shown in b. By further applica¬ tion of heat the drop becomes at last completely transparent; the corresponding temperature is the “ point of complete fusion.” The difference between I these two points is about 3° to 4° C. Several chemists have proposed an acoustical method for ascertaining the melting point of fats. The principle on which an apparatus of this kind is \ based is the following :—Two platinum wires con- W nected to a battery and an electrical bell are im¬ mersed in the solid fat. On the latter becoming melted the circuit is closed, and this moment is indicated by the ringing of the bell. The first apparatus of this kind was designed by Loewe, and has been modified in some minor points by Jean. The essential part of Jean's apparatus consists in a U tube, 6 into which a quantity of the melted fat, sufficient to fill the bend of the tube, is poured. Two platinum wires are then introduced into the solidified fat down each limb of the tube, and connected with a battery and an electi'ic bell. Next a little mercury is poured into one of the limbs of the tube, and the latter placed in a water bath. On the fat becoming melted the mercury will fall through it, thus closing the circuit. Another apparatus of the same type has been designed by Christo- manos. 1 It is shown in Fig. 33. As will be seen from the preceding remarks, the exact determina¬ tion of the melting point of a fat is attended with difficulties and uncertainty, besides requiring some time before a sample can be tested. Furthermore, small amounts of free fatty acids in the fat influence the melting point to a considerable extent. Therefore, in examining a sample of fat for commercial purposes the melting 1 point of the free fatty acids derived from it is usually taken (see below). When melted substances solidify, the “ latent heat of fusion ” is disengaged and a rise of temperature takes place. Fatty acids show this rise most distinctly, whilst in the case of fats it is not so well marked, and is more characterised by the temperature remaining con¬ stant for some time before further falling. Rudorff has studied the solidifying 1 points of fats with a view to employing them as constants. His method was to melt a fat and to agitate it continually with a thermometer, noting the temperature from time to time. He found that in the case of some fats the temperature fell to a certain point, remaining constant thereat for a time, then falling again. During the period of constant temperature the fat solidified; this tempera¬ ture was called the solidifying point. 1 Jour. Soc. Chem. Ind. 1890, 894. a V SOLIDIFYING POINT OF FATTY ACIDS 133 In the case of other fats again, on solidification setting in, a fall of temperature takes place with a subsequent rise until a maximum is reached, and then the temperature remains constant until the mass has become solid throughout. A number of other fats, finally, as beef and mutton tallow, have no solidifying point proper, the temperature rising a few degrees, but not remaining constant. These fats behave like mixtures, part of which has become solid whilst the remainder is still liquid. It is therefore prefer¬ able to examine the fatty acids instead of the fats themselves. Dalican has proposed a method for the deter¬ mination of the solidify¬ ing point of fatty acids, which has been adopted both in this country and in France for the com¬ mercial examination and valuation of fats. It is known under the name of “Titer Test,” and gives, as the writer can testify from his own experience, fairly constant and reliable results, if the test is made under exactly the same condi¬ tions. 100 grms. of the fat under examination Fig. 33 . are saponified, and the separated fatty acids freed from water and filtered into a porcelain dish. They are allowed to solidify and to stand over night under a desiccator. The fatty substance is then carefully melted in an air- bath, and as much of it poured into a test-tube, 16 cm. long and 3 - 5 cm. wide, as will fill the tube more than half full. The tube is then placed in the neck of a suitable flask—say a 2-litre flask—and a delicate thermometer, indicating one-fifth of a degree, inserted, so that the bulb reaches the centre of the mass. When a few crystals appear at the bottom of the tube, the mass is stirred by giving the thermometer a rotary movement, first three times from right to left, and then three times from left to right. Next stir continually, by giving to the thermometer a quick circular movement, without allow¬ ing it to touch the sides of the vessel, but taking care that all 134 PHYSICAL METHODS OF EXAMINING FATS AND WAXES chap. solidifying portions, as they form, are well stirred into the mass. The mass will gradually become cloudy throughout. The ther¬ mometer must now be observed carefully. A good plan is to write down the temperature at short intervals. At first the temperature will continue to fall, but then it will rise suddenly a few tenths of a degree and reach a maximum, remaining thereat stationary for some little time before it falls again. This point is called the “titer” or solidifying point. Finkener 1 does not consider this a satisfactory method, whereas in the opinion of the writer it forms a reliable basis for the com¬ mercial valuation of solid fats. Finkener uses larger quantities in small globular flasks of about 50 mm. diameter, and in order to prevent a rapid cooling he places the vessels filled with the melted acids in a wooden box 2 (Fig. 34). The same apparatus is also recommended by him for the determination of the solidifying points of different kinds of tallow. The solidifying points found by Finkener are higher than those obtained by Dalican's method. Finkener's apparatus has been adopted by the German Custom House officials. Higher solidifying points—by 0 - 5 C.—are also obtained when the fatty acids are previously heated for two hours at 100° C. as proposed by Wolfbauer 3 The latter’s method, worked out with the approval of the late Benedikt , is adopted in Austria, and I therefore describe it in full. 120 grms. of the fat are melted in a beaker at a temperature but slightly above its melting point, mixed with 45 c.c. of caustic potash solution (1250 grms. of caustic potash in one litre of water), and stirred until the fat is completely emulsified. It is then covered and kept at 100° C. for two hours, being occasionally stirred. A small portion is then tested by warming with alcohol (50 per cent) to ascertain whether saponification is complete, which is indicated by a clear solution; otherwise, it must be replaced in the bath and there allowed to remain until this is accomplished. The soap is now decomposed by boiling with 165 c.c. of dilute sulphuric acid, sp. gr. 1T42, preferably in a silver dish, until the free fatty acid rises to the top as a perfectly clear oily!layer. The silver dish is covered with an evaporating dish filled with cold water, to check the evaporation. The aqueous solution is then completely drawn off, and the fatty acid washed by boiling one-quarter of an hour with dilute sulphuric acid (5 c.c. of concentrated sulphuric acid and 100 c.c. of water). After settling and removing the dilute acid, it is boiled with 100 c.c. of pure water, this last operation being repeated until the washings are no longer acid. It is then dried in an open dish at 100° C. for two hours. 1 Jour.Soc. Chem. Ind. 1889, 424. 2 Ibid. 1890, 107. 6 Fig. 34. 3 Ibid. 1894,181. 908. V SOLIDIFYING POINT OF OILS 135 Only fatty acids obtained as above can be considered sufficiently pure and dry to be used for the determination of the solidifying point. In the determination proper the following apparatus is employed : a thin-walled test-tube, 3’S 1 cm. by 15 cm. is fixed by means of a cork in a suitable bottle. A centigrade thermometer, extending from 1° to 60° C., and graduated in fifths of a degree, is fixed in the test- tube by a second cork, which must be sufficiently loose to permit of an easy stirring of the contents of the tube with the thermometer. As the thermometer should be as short as possible, its scale is shortened by an enlargement blown in the bore in the interval be¬ tween 2° and 28° C. The amount of mercury above the surface of the fatty acid is thus diminished, and a very appreciable error (a lowering of the freezing point) is consequently avoided. The test- tube is then filled to within 1 cm., or 1| cm., of the top with the melted fatty acid, the thermometer immersed in the liquor to about the 35° mark (when the instrument should clear the bottom of the tube by about 4 cm. or 5 cm.), and the liquid stirred until it becomes quite opaque, and partial solidification sets in. Care should be taken at this point that the thermometer be not more deeply immersed, and after stirring rapidly in a circle ten more times, the thermometer is allowed to stand. The mercury now begins to rise in consequence of the latent heat liberated from the solidifying fatty acid ; the highest temperature noted may be taken as the freezing point. The reading of the thermometer should be corrected for its in¬ herent errors, previously determined. Its zero point should also be redetermined from time to time. Each determination should be repeated, and the difference between the two should not exceed 0T C.; as a rule, it will not exceed 0'05.“ The solidifying- or freezing (congealing) point of oils that are liquid at ordinary temperature is determined by means of freezing mixtures with which the tube containing the oil is surrounded. The thermometer is inserted in the tube by means of a cork ; conveniently a thermometer is used the scale of which commences above, the cork. The following table 3 gives the proportions of water and certain salts for the preparation of some freezing mixtures. Substances used. Parts per 100 of Water. Freezing Point. °C. Distilled water .... 0 Potassium nitrate 13 -2-85 Potassium nitrate 13 ) 5 0 Sodium chloride 3-3 \ Barium chloride 35-8 -87 Ammonium chloi’ide . 25-0 -15-4 1 In a narrower tube, say 2'5 cm. diameter, the solidifying point was found to be lower by 0-20° C. 2 For Garrigues’ “method” cp. Jour. Soc. Chem. Ind. 1895, 280. 3 Jour. Soc. Chem. Ind. 1889, 423. 136 PHYSICAL METHODS OF EXAMINING FATS AND WAXES CH. v If snow is available, lower temperatures are obtainable, as will be seen from the following table :— Substances used per 100 parts of Snow. Freezing Mixture. °C. 13 -5 parts potassium nitrate and 26 parts ammonium chloride . - 17’8 52 parts ammonium nitrate and 55 parts sodium nitrate . . -25'8 9 parts potassium nitrate and 67 parts ammonium rhodanate . -28'2 13 parts ammonium chloride and 37 "5 parts sodium nitrate . .' -307 32 parts potassium nitrate and 59 parts ammonium rhodanate . -30'6 2 parts potassium nitrate and 112 parts potassium rhodanate . - 34'1 39 '5 parts ammonium rhodanate and 54'5 parts sodium rhodanate - 37'4 The determination of the freezing point of fatty oils is not fre¬ quently made, this constant not being characteristic enough. Methods for the examination of lubricating oils in this respect (especially mineral oils) have been worked out by the officials of the Konigliche Technische Yersuchsanstalten, Berlin. Reference to their methods 7 - 7 Fig. 35. will be found in the Journal of the Society of Chemical Industry, 1889, 423; 1890, 772. Fig. 35 illustrates the apparatus in which the operation is carried out. (Cp. also Cold-Test, chap. xii. p. 713.) CHAPTER VI CHEMICAL METHODS OF EXAMINING FATS AND WAXES 1. Ultimate Analysis of Fats and Waxes The ultimate analysis of fats will be found of very little use for technical purposes,—the proportions of carbon, hydrogen, and oxygen of the different fats varying very little indeed. A glance at the follow¬ ing table, giving the percentages of the three elements contained in palmitin, stearin, olein, linolin, which may be considered as the chief ■constituents of most fats, will show this plainly :— Triglyceride. Formula. Carbon. Per cent. Hydrogen. Per cent. Oxygen. Per cent. Palmitin. C 5 iH 98 0 6 75-93 12-16 11-91 Stearin . ^WHuoOg 76-85 12-86 10-79 Olein C57H104O6 77-38 11-76 10-86 Linolin . 77-90 11-16 10-94 Ricinolein only differs considerably from these glycerides in its composition :— Formula. Carbon. Per cent. Hydrogen. Per cent. Oxygen. Per cent. C 57 H 104 O 9 73-46 15-37 11-17 The following table gives analyses of some of the more impoi’tant animal and vegetable fats :— 138 CHEMICAL METHODS OF EXAMINING FATS AND WAXES CHAP. Kind of Fat. Carbon. Per cent. Hydrogen. Per cent. Oxygen. Per cent. Mutton tallow 1 76-61 12-03 11-36 Beef tallow 1 76-50 11-91 11-59 Lard 1 .... 76-54 11-94 11-52 Horse fat 1 77-07 11-69 11-24 Butter fat 1 75-63 11-87 12-50 Seal oil 2 . 77-10 13-50 9-40 Finback oil 2 .... 77-05 12-05 10-90 Train oil 2 76-85 11-80 11-35 Cod liver oil 2 . 75-91 12-22 11-87 Linseed oil 1 76-80 11-20 12-00 > J > 9 77-80 11-20 11-80 Rape oil 1 . 78-00 11-00 11-00 77-99 12-03 9-98 . 78-20 12-08 9-72 ” .. 77-91 12-02 10-07 The ultimate analysis of waxes would be of less use still for identification. Ultimate analysis may, however, prove useful for the identifica¬ tion of the fatty acids, or some other constituent of fats and waxes. Of course, these substances must have been brought previously by crystallisation, etc., to a sufficient state of purity. 2. Qualitative Examination of Fats of known Origin by strictly Scientific Methods It has been pointed out repeatedly that the natural fats are more oi less complicated mixtures of several triglycerides, containing varying quantities of free fatty acids, of wax-like substances, and occasionally small quantities of hydrocarbons. The object of an exhaustive scientific examination of a pure fat or a wax is to resolve it into its constituents, and to identify them, i.e. to find out of which fatty acids and alcohols it is composed. It does not fall within the province of a general technical analysis of fats and waxes to institute such an exhaustive inquiry into their components. The methods used for such researches, viz. fractional distillation, fractional precipitation, and crystallisation, etc., being difficult to carry out, and absorbing a large amount of time, must naturally be reserved for an investigation of a strictly scientific character. We shall, therefore, only glance at the processes adopted in such research work. 1 Schulze and Reinecke ; Liebig’s Annalen, 142. 198 ; Kdnig, Chemische Zusam - mensetzung der Nalirungsmittel, etc. i. 199 ; 200 ; 429. 2 Schaedler, Technologie der Fette und Oele, 750. VI VOLATILE FATTY ACIDS 139 A. Examination of the Acid Constituents EXAMINATION OF THE VOLATILE FATTY ACIDS—FRACTIONAL SATURATION WITH ALKALI The aqueous solution of the volatile fatty acids prepared by saponifying the fat, separating the fatty acids, and distilling the latter in a current of steam, is divided, according to Liebig, into two equal parts. One part is neutralised exactly by caustic potash ; the second part is then added, and the whole subjected to distillation. The acids having lower boiling points pass into the distillate, whilst the higher boiling acids remain as potassium salts in the distilling flask. Acetic acid, however, also remains behind as potassium salt. By repeatedly treating both the distilled and the remaining acids in the same way, finally pure fractions of the several acids are obtained. Liebig employed this method for separating butyric acid from a mixture of butyric and isovaleric acids, and further for isolating acetic acid when mixed with either of these two acids. Veiel, however, has arrived at the opposite result, having found that isovaleric acid distilled over, whereas butyric acid remained behind. Lieben partially confirmed Veiel’s results, by stating that Liebig’s method is not accurate, but that an approximately satisfactory separation is obtained by suit¬ ably modifying it, viz. by partially neutralising the mixture of acids, when the higher acids will distil off and the lower remain behind as salts. Wechsler 1 has tested Lieben’s method by applying it to equivalent amounts of two acids ; he examined the following mixtures : Formic and acetic, acetic and propionic, acetic and butyric, acetic and isobutyric, propionic and butyric, butyric and caproic acids. The mixed acids were neutralised with four-fifths of the theoretical amount of alkali, and distilled so long as the distillate was found to be acid. The remaining salts were then treated with a quantity of sulphuric acid sufficient to exactly liberate three-fifths of the fatty acids, and again distilled. The last fifth was finally obtained by acidulating the residue and distilling it. The first fraction was found to contain the higher acid, and the last fraction the lower acid, in an almost pure state. The mixture of butyric and isovaleric acids, however, could not be separated by this method, a result at variance with the state¬ ments of both Liebig and Veiel. Crossley , 2 3 however, could not obtain such good results as one is led to expect from IVechsler’s statements, and in his opinion the latter’s method cannot in any way be looked upon as satisfactory for separating mixtures of fatty acids. Erlenmeyer and Hell 3 propose to separate the several volatile acids by fractional saturation with silver carbonate. The acids having a higher boiling point are precipitated first. Fitz i has shown that by mere fractional distillation of the free 1 Jour. Soc. Chem. Ind. 1894, 181 ; cp. also Sorel, ibid. 1896, 143. 2 Proc. Chem. Soc. 1897, 21. 3 Liebig's Annalen, 160. 296, footnote. 4 Berichte, 11. 46. 140 CHEMICAL METHODS OF EXAMINING FATS AND WAXES CHAP. acids, if care is taken to replace the water distilled off, a separation can be effected, the acid of higher molecular weight passing over first. This result has been corroborated by Hecht. 1 EXAMINATION OF THE NON-VOLATILE FATTY ACIDS The non-volatile acids can be separated into solid (saturated) and liquid (unsaturated) acids by exhausting their lead salts with ether (see below). The solid saturated acids may be further separated by fractional precipitation of their alcoholic solutions (saturated in the cold) with alcoholic solutions of barium or magnesium acetate. 2 Pebal 3 uses as a precipitant an alcoholic solution of lead acetate. Every fraction is decomposed by hydrochloric acid, and the fatty acids of the same melting point are united. The several fractions are repeatedly sub¬ jected to the same process until pure substances are obtained. A fraction may only then be looked upon as a chemical individual if its melting point is not altered by further recrystallisation, and if by partial precipitation fractions having identical melting points are obtained. It is thus evident that pure acids can only be obtained by a very frequent repetition of the fractional precipitation. It is further evident that quantitative separation of the individual acids is altogether out of the question. Experiments made by Hehner and Mitchell 4 on mixtures of palmitic and stearic acids with a view to determine the usefulness of such methods for analytical purposes, give an approximate idea as to how far separation may be effected. Pure stearic and palmitic acids were mixed in the proportions given in the following table, and precipi¬ tated with measured quantities of aqueous barium acetate solutions, sufficient to precipitate the stated amounts of stearic acid. Separation effected by Precipitation of mixed Stearic and Palmitic Acids with Aqueous Barium Acetate Stearic Acid. Grms. Palmitic Acid. Grins. Barium Acetate added sufficient to precipitate Stearic Acid. Grms. Stearic Acid in Precipitate. Per cent. 1 1 1 717 1 2 1 62-8 1 3 1 27-9 1 3 1 30-9 0-5 0-5 0-5 627 1 1 0-5 46-6 1 Liebig’s Annalen, 209. 319. 3 Annalen, 91. 138. 2 Heintz, Jour, prakt. Chemie, 66. 1. 4 Analyst, 1896, 318. VI EXAMINATION OF LIQUID FATTY ACIDS 141 On precipitating the filtrates in a similar fashion, it not infrequently happened that the second fraction contained a larger proportion of stearic acid than the first proportion. Similar experiments with aqueous solution of magnesium acetate and alcoholic solutions of lead acetate gave no better results. The liquid fatty acids are further examined by Hazura’s 1 method of oxidising with a dilute solution of potassium permanganate. As a rule, the oxidation products of oleic, linolic, and the linolenic acids, viz. dihydroxystearic, sativic, and linusic and isolinusic acids, will have to be looked for. An examination of this kind was carried out in the following manner : 30 grms. of the liquid fatty acids were neutralised with 36 c.c. of caustic potash of T27 specific gravity. The resulting soap was then dissolved in 2000 c.c. of water, and an equal volume of a 1| per cent solution of potassium permanganate allowed to run in in a thin stream with constant stirring. The solution was allowed to stand for ten minutes, and a quantity of sulphurous acid solution added, with continuous agitation, sufficient to dissolve all the precipitated hydrated manganese peroxide, and to impart an acid reaction to the solution. Dihydroxystearic and sativic acids were precipitated (A), whereas linusic and isolinusic acids remained dissolved (B). The precipitated acids (A) were washed first with a little ether in order to remove some of the original liquid acids that had escaped oxidation, and then exhausted with large quantities of ether at the ordinary temperature, 2000 c.c. of ether being used for every 20 grms. of the precipitate. The ethereal solution, containing dihydroxystearic acid, was evaporated down to 150 c.c., when, on cooling, crystals were obtained which after recrystallisation from alcohol were identified by their habitus, their melting point, and some “ quantitative reactions ” (see following chapter) as dihydroxystearic acid. That portion which was found to be insoluble in the cold ether was boiled out repeatedly with large quantities of water. Each quantity was filtered off whilst boiling hot and allowed to deposit crystals on cooling, which were examined separately by ascertaining their melting points and crystalline forms, and identified as sativic acid. A small quantity of insoluble acid was recognised as dihydroxystearic acid that had not been dis¬ solved by ether. The acid filtrate (B) was neutralised with caustic potash, boiled down to one-twelfth or one-fourteenth of the original volume and acidulated with sulphuric acid. The precipitate, consisting of a brown flocculent mass, was dried in the air and treated with ether, which dissolves azelaic acid and other acid secondary products of oxidation. The insoluble portion was recrystallised first from alcohol and then from water. By means of the melting points and the detection of characteristic needles on the one hand, and obtruncated 1 Monatshefte f. Chemie, 1887, 147; 156 ; 260. 1888, 180 ; 190 ; 469; 478; 944 ; 947. 1889, 190. 142 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. rhombic plates on the other, isolinusic and linusic acids were identified. To effect a separation of the two acids the substance was recrystallised from a moderate quantity of water, so as to separate the more soluble isolinusic acid from the less soluble linusic acid. By weighing the several acids thus obtained the quantitative composition of the liquid acids was estimated approximately. A synopsis of the preceding operations is given in the following table :— Hydroxy Acids A. Precipitate. B. Filtrate. a. Soluble in Ether. b. Insoluble in Ether. a. Easily Soluble in Water. b. Sparingly soluble in Water. Dihydroxystearic acid Sativic acid Isolinusic acid. Linusic acid The following table, summarising some of the properties of the four acids, will assist in mapping out another method of separation by means of the barium salts :— [Table 144 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. Similar methods will have to be adopted to identify other liquid acids by means of their oxidation products, as the acids in, say, castor oil (cp. table, p. 67). Fahrion 1 proposes to shorten Hazura's method by avoiding the preliminary preparation of the fatty acids, and the separation of the saturated solid fatty acids from the liquid unsaturated acids. He finds that the saturated fatty acids are not acted upon by potassium permanganate as long as unsaturated ones are present, oxalic acid, the oxidation product of glycerol, passing into the aqueous solution. The separation of the hydroxy acids from the saturated acids, and from the unoxidised unsaturated acids, is effected by means of petroleum ether, which does not dissolve the former acids. The operation is carried out as follows :—Saponify 10 grms. of the fat in a porcelain dish of 1500 c.c. capacity, with 10 grms. of caustic soda, adding alcohol and a little water. Evaporate to dryness on the water- bath, dissolve the soap in 1000 c.c. of water, heat to boiling, and add gradually, as a 5 per cent solution, 10-25 grms. of potassium perman¬ ganate (according to the iodine absorption value of the fat) with constant stirring. Heat finally for a short time, filter through a plaited filter, and acidulate the filtrate with hydrochloric acid. The separated acids, when quite cold, are filtered through linen, expressed as completely as possible by hand, and finally exhausted with petroleum ether. The saturated fatty acids, and that part of the unsaturated which escaped oxidation, are dissolved by the petroleum ether whilst the hydroxy acids remain behind. 2 If isolinusic acid be present, part of it may be found in the aqueous solution. The yield, however, is a very poor one. Thus 10 grms. of tallow gave only about 1 grm. of solid acids, viz. dihydroxy stearic acid containing some azelaic acid. The former, after recrystallisation from alcohol, melted at 126° C. (137° C., Hazura). To detect linolie aeid in non-drying oils, the precipitated fatty acids need not be exhausted, according to Fahrion , with petroleum ether, but may be boiled with 1000 c.c. of water. The boiling solution is filtered, the filtrate boiled down to 100 to 150 c.c., and transferred, whilst still warm, to a separating funnel. The solution, when quite cold, is acidulated with hydrochloric acid and shaken out with ordinary ether. The presence of sativic acid, the oxidation product of linolie acid, will be indicated by white flocks floating about in the lower part of the ethereal solution. 10 grms. of cotton¬ seed oil examined by this method yielded 0'6 grm. of flocks, melting, after recrystallisation, at 152° C. (173° C., Hazura). F. Krafft 3 has resorted to the method of fractional distillation in vacuo in order to purify and isolate some of the acids belonging to the oleic series. He has found as a very suitable pressure for practical use that of 100 mm. of mercury, slight variations of pressure exercising 1 Jour. Soc. Ohem. Ind. 1893, 951. 2 Cp., however, p. 204. 3 Jour. Chem. Soc. 1889, Abstr. 690. VI FRACTIONAL DISTILLATION 145 in that case a smaller influence on the boiling point than if a lower pressure be chosen, and the troublesome frothing of the liquid being- all but prevented. Kraft’s apparatus is shown in Fig. 36. Between the receiving vessel of the distilling apparatus and the filter pump p a thick-walled Fig. 36. bottle A is inserted as a vacuum vessel. By means of tap h this vessel is connected with a cylinder B, fitted with two tubes n and s. s ends in a finely-drawn tube, and is provided with the regulating tap i. Fig. 37. A is also connected with a mercury gauge m. In order to regulate the pressure the whole apparatus is first exhausted a few millimeters below the required pressure; next tap li is opened completely, and tap i so far, that the air rushing in keeps the gauge at the desired height. More recently Kraft 1 uses for determining boiling points the 1 Berichte, 1896, 1316. L 146 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chai>. vacuum of the cathode light ■ so high a vacuum, for the measurement of which the reading of a mercury gauge is useless, can be obtained without difficulty by employment of a Bobo vacuum pump. The boiling points of fatty acids, recorded p. 30, have been determined by means of this apparatus. This somewhat complicated apparatus may be advantageously replaced by a combination of the two apparatuses (Fig. 37 and Fig. 38), designed by the writer 1 for fractional distillation in vacuo, and found very convenient in daily use. It may be recommended for laboratories having a vacuum pipe with several taps. The distilling flask is provided with ■ a finely - drawn tube fitted outside with an india-rubber tube and a screw-clamp, by means of which the pressure can be regulated accurately, and at the same time frothing of the liquid can be pre¬ vented. Nozzle a of the adapter (Fig. 38) is connected with a Liebig condenser, and b and c by means of strong india-rubber tubing with two taps of a vacuum pipe. On starting the distillation, the distilling flask, the adapter', and the conical receiv¬ ing flask are exhausted through b and c, the stopcock d being open. When the first fraction has distilled over, close the tap d and then the vacuum tap connected with c. The receiving flask is thus shut off from the vacuum pipe, and is filled with air by disconnecting the india- rubber tubing from c. The flask can be taken off easily and emptied, or replaced by another, whilst the distillation proceeds without any interruption. When the receiving flask is fitted on again it is exhausted through c, as before, and con¬ nected with the system by opening tap d. Pig. 3S. B. Examination of the Basic Constituents All fats yield on saponification Glycerol, and it is therefore only necessary to determine its proportion. This is done by the methods detailed, p. 208. The waxes yield as basic constituents alcohols of the aliphatic series, or cholesterols. Any hydrocarbons contained in the waxes are isolated together with the former as “ unsaponifiable matter ” If a mixture of alcohols has been obtained, the isolation of the individual alcohols may be effected by fractional crystallisation. It will be found useful to convert the alcohols into their benzoic or acetic 1 Jour. Chem. Soc. 1889, Trans. 360. VI QUANTITATIVE REACTIONS 147 ethers; the latter are easier to distil than the original substances, and can therefore be more effectively resolved into fractions(cp. also p. 229). 3. General Methods of Quantitative Analysis of Fats, or Mixed Fats and Waxes In the quantitative analysis of a fat, or a mixture of different fats, or of fats and waxes, we have, in the first place, to determine its proximate components, viz. alcohols (as glycerol, cetyl alcohol, etc.) and fatty acids (as oleic acid, palmitic acid, etc .); secondly, we have to examine it for the presence of foreign bodies in admixture, such as mineral oils, resin, etc., and ascertain their proportion and character. The determination of these latter substances will be discussed in the following two chapters. Here we consider the examination of the dried fat or wax as obtained in the manner described (p. 92), with a view to determine its proximate constituents. Though we cannot make our examination with strictly scientific accuracy, there are a number of methods answering very satisfactorily the requirements of technical analysis, and these may conveniently be arranged under two heads as follows :— A. Quantitative Reactions, and B. Quantitative Determination of some Constituents of Fats and Waxes. Besides the “ quantitative reactions ” we have a number of chemical reactions, which are usefully applied to the examination of fatty substances, such as the elaidin test, oxygen absorption test, thermal tests, etc. But hitherto they have not been worked out so fully as to admit of their being classed amongst the quantitative reactions, although in all probability at least some of them are likely to attain to that rank. Meanwhile we must look upon them as preliminary tests, that can be usefully employed as sorting tests, especially for pur¬ poses of classifying the liquid fats and waxes. For these reasons the “ preliminary tests ” will be described later on, where the application of the physical and chemical methods to the systematic examination of fatty substances is dealt with. A. QUANTITATIVE REACTIONS The methods described under this head, although generally not admitting of an absolute estimation of the constituents of a fat or wax, are of the greatest help in technical analysis, inasmuch as they afford a means for a comparative determination of the most important constituents. Thus we are enabled to ascertain— 148 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. i. The acid value —the measure of the proportion of free fatty acids in a fat or wax. ii. The saponification value (Kottstorfer value) — the measure of the amount of alkali requisite for neutralising the total fatty acids. iii. The ether value —the measure of the proportion of trigly¬ cerides or other compound ethers of fatty acids present in a fat or wax. iv. The Reichert (or Reichert-Meissl) value —the measure of the proportion of volatile fatty acids. v. The Hehner value —the percentage of insoluble fatty acids. vi. The acetyl value —the measure of the proportion of hydroxy acids or free alcohols. vii. The (bromine or) iodine value —the measure of the pro¬ portion of unsaturated fatty acids. i. The Acid Value The acid value indicates the number of milligrammes of potassium hydrate required to saturate the free fatty acids in one gramme of a fat or wax; or, in other words, it gives the amount of potassium hydrate, ex¬ pressed in tenths per cent, necessary to neutralise the free fatty acids in one gramme of a fat or wax. This value is therefore a measure of the free fatty acids in a fat or wax. For the determination of the acid value of a fat or wax the sample is dissolved in alcohol (purified methylated spirit), or in methyl alcohol, or a mixture of alcohol and ether, and titrated with aqueous or alcoholic standard alkali, phenolphthalein being used as indicator. The standard alkali may be, according to the quantity of fat available for the analysis, half-, or fifth-, or tenth-normal. Some analysts prefer an alcoholic standard solution to an aqueous, al¬ though the accuracy of the analysis is hardly increased thereby. On the contrary, an alcoholic standard solution has the drawback of altering its titer more quickly, and therefore requiring occasional re-standardising. The alcoholic alkali is prepared by dissolving the requisite quantity of caustic potash or caustic soda in the smallest possible quantity of water, and making the solution up to the re¬ quired standard with alcohol, purified as described above (p. 19). The end-point of titration is distinctly recognisable, saponification of the neutral fat not taking place immediately by the small excess of alkali necessary to produce the pink colouration. On standing, however, for some time, even if access of air and consequent de¬ colouration by absorption of carbonic acid be excluded, the pink colour will disappear in some cases, owing to saponification of neutral ethers 1 taking place. This will be especially the case if the specimen under examination were dissolved in ether-alcohol. It would, obviously, be erroneous to add more alkali from time to time as the pink colouration disappears. 1 Lewkowitsch, Jour . Soc . Chem . Ind . 1890, 846. VI ACID VALUE 149 Mineral acid in the oil should, of course, be first removed by- washing with water, and the solvents employed should be tested for acidity. Before using the solvent it will be found a good plan to neutralise it exactly with decinormal alkali, phenolphthalein being the indicator. Liquid fats are weighed off or measured off accurately in a flask, neutralised alcohol and a few drops of phenolphthalein solution are then added, and the liquid is titrated with constant shaking. Con¬ venient quantities are 10 grms. (or 10 c.c.) of oil and 50 c.c. of alcohol, to be titrated with \ normal alkali. Solid fats must be heated with the alcohol on the water-bath until the alcohol boils; they are then titrated in the same manner. Should the fat solidify during the operation, the flask must be heated again before the titration can be brought to an end. Of course, to guard against partial saponification of the neutral fat, excess of alkali must be avoided. If it should be deemed preferable to work with clear solutions, the fat may be dissolved in a mixture consisting of two parts of ether and one part of alcohol, and then titrated with alcoholic standard solution. Archbutt proposes to use as solvent methyl alcohol purified by distilling it twice. One or two examples will illustrate clearly the method of cal¬ culating the acid value. 1. Weighed off 3'254 grms. of tallow. Required for neutralising the free fatty acids 3'5 c.c. decinormal caustic potash (or soda) or 3"5 x 5"61 milligrms. KOH. The amount of KOH required for one grm. of tallow, or its acid value, is therefore 3-5x5-61 3-254 = 6-03. 2. Measured off 25 c.c. of olive oil, spec. grav. 0-917. Required for neutralising the free fatty acids 9-4 c.c. of a solution of caustic potash, 1 c.c. of which contains 0*0257 grm., or 25*7 milligrms. KOH. The weight of the oil is 25 x 0 - 917 = 22'925 grms., therefore 9-4x25-7 A ~ 22-925 10-5. The proportion of free fatty acids in a fat is frequently expressed in a different manner. In this country, especially in the case of oils, it is usual to cal¬ culate the free acid as oleic acid, molecular weight 282, and to express the amount of free fatty acids in per cents of the fat. Thus in the first example the percentage of free fatty acids would be given as 3-5x0-0282 3-254 x 100 = 3-03 %, and in the second, example 9-4x0-0257 x0-282 x 100 = 5-28 %. 0-0561 x 22-925 150 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. Since the molecular weight of oleic acid, 282, is approximately five times 561, the molecular weight of KOH, and the acid value expresses the amount of KOH in tenths per cent, a rapid and in most cases sufficiently accurate method of converting the acid value into per cents of oleic acid is to multiply the former by 0*5. In other cases, as for lubricating oils, the free fatty acids are some¬ times expressed in terms of sulphuric anhydride, S0 3 , and the result is given in per cents of the fat employed. Thus in the first example we should find and in the second 3-5 x 0-004 3-254 x 100 = 0-43 %, 9-4 x0-0257x0-04 0-0561 x 22-925 x 100 = 0-75 %, Kottstorfer expresses the acidity by the number of c.c. of normal potash required by 100 grms. of the fat. In this connection the number of c.c. is termed “ degrees of acidity.” In the subjoined table a comparison is made of the different methods of expressing the acidity; an easy calculation allows of transforming one term into any other. Acid Value, being T > 0 per cent of KOH. Oleic Acid. Per cent. Sulphuric Anhydride. Per cent. Degrees Kottstorfer, being c.c. normal KOH per 100 grms. Fat. 1 0-5027 0-0713 1-782 1-9893 1 0-1418 3-546 14-0250 7-0500 1 25-000 0-5610 0-2820 0-0400 1 In case the nature of the free acid, and consequently its molecular weight, be known, the absolute quantity of free fatty acids may be calculated as shown above for oleic acid. In such cases the following table may be found useful:— Acid Values of Some Fatty Acids Acid. Formula. Molecular Weight. Acid Value. Butyric c 4 h 8 o 2 88 636-3 Caproic c 6 h 12 0 2 116 482-8 Capric ^10^20^2 172 325-0 Laurie c 12 h 2j o. 200 280-0 Myristic c 14 h 28 0 2 228 245-5 Palmitic 256 218-7 Stearic 284 197-1 Oleic 282 198-6 Linolic 280 200-0 Ricinoleic 298 188-0 Erucic ^22^42^2 338 166 0 Cerotic ^26^52^2 396 141-7 VI SAPONIFICATION VALUE 151 ii. The Saponification Value (Kottstorfer Value) The saponification value (or Kottstorfer value) indicates the number of milligrammes of potassium hydrate required for the complete saponification of one gramme of a fat or wax; or, in other words, it represents the amount of potassium hydrate , expressed in tenths per cent , requisite to neutralise the total fatty acids in one gramme of a fat or wax. For the determination of the saponification value are required— (1) An accurately standardised hydrochloric acid solution, the titer of which is expressed in terms of KOH; it is most convenient to use half-normal acid; (2) an alcoholic potash solution prepared by dis¬ solving about 30 grms. of caustic potash, pure from alcohol, in a little water, and making it up with strong alcohol to 1000 c.c. The alco¬ holic solution is allowed to stand for one day, and is then filtered through a large plaited filter into a bottle, conveniently closed by an india-rubber stopper fitted with a 25 c.c. pipette, the upper end of the pipette being closed in its turn by a short piece of india-rubber tubing and a clamp, or a glass rod. The bottle should be kept in an equably warm place protected from light. The alcohol used for preparing the potash solution should be as pure as possible. Commercial spirits of wine tested with a strong caustic potash solution should remain white; if it becomes yellow immediately, it must be rejected. Methylated spirit may be used, but it must be purified as described, p. 19. If the alcohol has been pure, the alcoholic potash will not become brown even after several months’stand¬ ing ; it assumes, however, in course of time a light yellow colouration, but this does not interfere with the accuracy of the titration. The determination of the saponification value is carried out as follows : Weigh off accurately, in a flask holding 150 to 200 c.c., 1'5 to 2 grms. of the purified and filtered fat. Next run into the flask 25 c.c. of the alcoholic potash, measuring it off by means of the pipette fitted in the stopper of the bottle. It is not necessary to add exactly 25 c.c., but care must be taken that for each determination precisely the same quantity is used. A good plan is to allow the contents of the pipette to run out entirely, and to drain it until, say, three more drops have dropped off. Then attach a long cooling tube or an inverted condenser to the flask, and heat it on the boiling water-bath for half an hour so that the alcohol is simmering, frequently impart¬ ing to the contents of the flask a rotatory motion. Next add 1 c.c. of a one per cent phenolphthalein solution, and titrate back the excess of potash with the half-normal hydrochloric acid. It is always best to make a blank test, treating the same amount of alcoholic potash in exactly the same manner 1 as the solution of fat. Every source of error, as carbonic acid, etc., has therefore, as nearly as possible, in both tests the same influence on the final result, and is thus eliminated. The difference of the numbers of c.c. of acid 1 This should extend as well to the material of the flask. Cheap German flasks are attacked by the alkali to a considerable extent. It is best to use flasks made of Bohemian or Jena sdass. 152 CHEMICAL METHODS OF EXAMINING FATS AND WAXES CHAP. used for the blank test and the real test corresponds to the quantity of potash required ; this is calculated to milligrms. of potash for one grm. of fat. Sulphuric acid should not be substituted for the hydrochloric acid, potassium sulphate being precipitated, whereby the delicacy of the end reaction is impaired. For Henriques’ method cp. chap. ii. p. 20. In the case of dark-coloured solutions M c Ilhiney 1 proposes to measure the amount of alkali used, by the amount of ammonia it will liberate from an ammonium salt. He proceeds as follows : The sub¬ stance (2 grms.) is saponified with excess of alcoholic caustic soda as usual, and the alcohol evaporated off. 250 c.c. of 93 per cent alcohol are added next, the soap dissolved by warming, and carbon dioxide passed through the solution for about one hour, in order to precipitate the excess of alkali as carbonate and bicarbonate. The precipitate is then filtered off, the alcohol evaporated from the filtrate, and 100 c.c. of a 10 per cent solution of ammonium chloride added, and heated, whereby the ammonia is distilled off. It is received in hydrochloric acid and titrated. A correction must, of course, be made for the sodium bicarbonate dissolved by the 93 per cent alcohol. This process is cumbersome and certainly introduces errors ; it is by far simpler to dilute the soap solution with sufficient alcohol, so as to obtain a distinct end reaction [or to employ as indicator alkali-blue (De Negri and Fabris)]. Example .—Weighed off T532 grms. of olive oil, and saponified with 25 c.c. of alcoholic potash solution. Required for titrating back 12-0 c.c. half-normal acid; further, required for the blank test 22'5 c.c. of the same acid. Therefore employed for saponification a quantity of caustic potash corresponding to Hence (22-5-12-0) 0-0561 2 grms. = 294 '5 milligrms. KOH. Used for one grm. of fat 294-5 1-532 milligrms. KOH = 192-2 milligrms. KOH. The saponification value of the olive oil is therefore 192‘2. Allen 2 has proposed to use instead of the saponification value as defined here the saponification equivalent, this being the number of grammes of fat saponified by one equivalent of potassium hydrate in grammes, i.e. by 56T grms. KOH; or, what amounts to the same, by one litre of a normal solution of caustic potash or caustic soda. The saponification equivalent is found by dividing the percentage of potassium hydrate required for saponification into 5610. There is no advantage gained by expressing this important value in the manner proposed by Allen, and we shall therefore adhere to the use of the saponification value as adopted above. The relation between 1 Jour. Soc. Chem. Ind. 1895, 197. 2 Commercial Organic Analysis, ii. 40. VI SAPONIFICATION VALUE 153 the saponification value and Allen's saponification equivalent is shown by the following formulae :— Sap. Val. = c.c. of normal potash x 56T _c.c. of normal potash x 56100 grrns. of fat employed milligrms. of fat employed Sap. Equiv. = 5610 5610 per cent KOH c.c. of normal potash x 0'0561 grms. of fat employed x 100 grms. of fat employed x 5610 c.c. of normal potash x 5'61 grms. of fat employed x 1000 c.c. of normal potash milligrms. of fat employed c.c. of normal potash or, if a be the number of c.c. of normal potash, and b the number of milligrms. of fat employed : Sap. Val. =~ x 56100 ; Sap. Equiv. = -^-. Hence it is clear that Allen's saponification equivalent can be found by dividing 56100 by the saponification value ; conversely, the saponi¬ fication value is obtained by dividing 56100 by the saponification equivalent: Sap. Val. =- 56100 Sap. Equiv. ; Sap. Equiv. = 56100 Sap. Val. The saponification value of neutral glycerides and other ethers of fatty acids varies, of course, with the nature of the fatty acids; the lower the molecular weight of the fatty acids (or, what amounts to the same, of the ethers) the more potash will be required to neutralise the fatty acids of one grm. of fat or wax, or, in other words, the higher will the saponification value be. To illustrate this more clearly, we give in the following tables the saponification values of some pure trigly¬ cerides and some pure ethers of mono-atomic alcohols :— Saponification Values of Triglycerides Triglyceride. Formula. Molecular Weight. Saponific. Value. Butyrin C 3 H 5 (0. c 4 h 7 0) 3 302 557'3 Valerin c 3 h 6 (0.c 6 h 9 0) 3 344 489'2 Caproin C 3 H 5 (O.C 6 H u O) 3 384 438-3 Caprim C 3 H 5 (O.O 10 H 19 O) 3 552 305-0 Laurin C 3 H 5 (O.CAO) s 638 263-8 Myristin C 3 H 6 (0. c 14 h 27 0) 3 722 233-1 Palmitin c 3 h 5 (0.c 16 h 31 0) 3 806 208-8 Stearin P 3 H b (O.C 18 H sb O) 3 890 189-1 Olein C 8 H5(O.C u H 88 0) 8 884 190-4 Linolin c 3 h 5 (0 . c 18 h 31 0) 3 878 1917 Ricinolein c,h 8 (0.c 18 h 88 0 9 ) 3 932 180-6 Erucin C 3 H 5 (0. C 22 H 41 0) 3 1052 160-0 154 CHEMICAL METHODS OF EXAMINING FATS AND WAXES CHAP. Saponification Values of Ethers of Mono-atomic Alcohols Ether. Formula. Molecular Weight. Saponific. Value. Cetyl palmitate Ci 6 H,iO . OC nfi H, s 480 116-9 Myricyl palmitate Ci6H 31 0. OC 30 H fi , 676 83-0 Ceryl cerotate C 26 H 51 O.OCo fi H 53 760 73-1 Frequently the term “saponification number of fatty acids” is met with; the saponification value of a fatty acid is, of course, identical with its acid value (cp. table, p. 150). In the tables given in chap. xi. I shall use the term saponi¬ fication value of the fatty acids in order to avoid confusion between “acid value of the fat” and “acid value of the fatty acids.” The latter value is a “constant,” whereas the acid value of a fat varies. iii. The Ether Value The ether value indicates the number of milligrammes of potassium hydrate required for the saponification of the neutral ethers in one gramme of a fat or wax. It is evident that the ether value will be identical with the saponification value if the fat or wax contains no free fatty acids, or, in other words, is quite neutral. As a rule, however, fats and waxes contain small quantities of free fatty acids, and in that case the saponification value will be the sum of the acid and ether values. The ether value is therefore represented by the difference of the saponification and acid values. The ether value can be found direct by first neutralising a weighed sample with alcoholic potash, as in the determination of the acid value (see above), and then saponifying with alcoholic potash as detailed in the preceding paragraph. Fatty acids have, of course, no ether values, their acid and saponi¬ fication values being identical (cp., however, p. 206). iv. The Reichert (or Reiehert-Meissl) Value The Reichert (or Reiehert-Meissl) value indicates the number of cubic centimetres of decinormal potash requisite for the neutralisation of that portion of the volatile fatty acids which is obtained from 2'5 (or 5) grammes of a fat or wax by the Reichert distillation process. There is no convenient method in use to determine quantitatively the amount of volatile fatty acids in a fat. Reichert 1 was the first to> suggest a process (in the examination of butter) for estimating a 1 Zeitsch. f. analyt. Ghemie, 18. 68. VI REICHERT VALUE 155 definite proportion thereof; although not yielding absolute values, still it constitutes a valuable method by furnishing numbers which are comparable. Reichert originally proposed to ascertain the number of c.c. of deci- normal alkali required for the saturation of the volatile fatty acids from 2-5 grms. of a fat, but at present it is customary to work accord¬ ing to Meissl’s modification, employing 5 grms. of substance. In order to avoid errors, therefore, the quantity of fat to wdiich the value found relates should always be stated. In the following pages the Reichert value always refers to 2'5 grms. of fat, and the Reichert-Meissl value to 5 grms. of fat. 1 The Reichert value being an arbitrary one, it is absolutely essential to adhere strictly to the conditions of operating as laid down by the different authors whose processes will be described. We subdivide these into two groups :— (a) Processes in which the Volatile Fatty Acids are distilled off. Reichert’s Process with Meissl’s Modification.—Weigh off accurately 5 grms. 2 of the melted and purified fat in a flask of about 200 c.c. capacity, and add to it about 2 grms. of stick potash (conveniently kept in stock in pieces of about the same length) and 50 c.c. of 70 per cent alcohol. Saponify by heating on the water-bath with constant shaking, until the alcohol has evaporated off completely. Dissolve the remain¬ ing soap paste in 100 c.c. of water, add 40 c.c. of dilute sulphuric acid (1 : 10) and a few small pieces of pumice. Fit to the flask a T piece provided with a bulb, and connect with a Liebig condenser. Distil the liquid carefully so that 110 c.c. pass over within about one hour’s time. They are received in a measuring flask, and 100 c.c. of it filtered into another measuring flask. Add to the filtered liquid tincture of litmus or phenolphthalein, and titrate with decinormal caustic potash until the acid is exactly neutralised. The number of c.c. used is multiplied by IT, and thus the Reichert-Meissl value obtained. (About half of this is the Reichert value.) Thus, if for 5 grms. of butter fat 28 c.c. of decinormal caustic alkali were required, the Reichert-Meissl value of that butter fat is 28. It is hardly necessary to emphasise the necessity of using alcohol free from acid and aldehyde. The safest plan will be to work a blank test side by side with the sample, and to take the difference found as the actual result. Even with the purest alcohol a slight acidity will be noticeable in the blank test. Schweissinger 3 has found for a sample of absolute alcohol a Reichert-Meissl value of 0'56, and for a sample of purest commercial alcohol 1'32. Impure alcohol gives rise to the formation of acetic acid and should therefore be rejected altogether. It should be distinctly understood that by this distillation process a portion only of the volatile fatty acids is recovered. Richard Meyer 1 It should be noted that the Reichert-Meissl value is not necessarily twice the Reichert value. 2 Dingl. Polyt. Jour. 233. 229. 3 Phcmnac. Centralhalle, 8. 320. 156 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. has shown that on distilling in a current of steam a value greater by 25 per cent is obtained. Hence the necessity of always working under strictly the same conditions. Along with the volatile acids traces of higher fatty acids will pass over; they will be found in the distillate as minute oily drops or solid particles; but they do not vitiate the result, as they are removed by the subsequent filtration. The excellent Reichert process has not escaped the fate of nearly all modern methods used in fat analysis, viz. to receive at the hands of numerous analysts a number of supposed improvements, most of which are altogether insignificant and hardly offer any advantage whatever. Thus Munier and others proposed to substitute phosphoric acid for sulphuric acid 1 ; but Cornwall 2 has shown that the values obtained are too low. Wollny 3 has raised a number of objections to the foregoing process, pointing out the following sources of error :—(1) absorption of carbonic dioxide during the saponification, introducing an error up to 10 per cent; (2) formation of ethers during the saponi¬ fication, causing a loss of 8 per cent; (3) formation of ethers during the distillation with a loss of 5 per cent; (4) coherence of the fatty acids during the distillation, which may, in some cases, involve a loss of as much as 30 per cent; (5) the form and size of the distillation apparatus and the time the distillation lasts, which may influence the result to the extent of ± 5 per cent. These objections have been refuted by v. Eaumer and Sendtner. However, as a number of determinations, carried out by various chemists according to Wollny 1 s somewhat too detailed modifications, have found a place in the literature of the subject, his process may be described fully. Wollny’s Modification. —5 grms. of the clarified fat are treated in a round-bottomed flask of 300 c.c. capacity (length of neck 7-8 cm., width of neck 2 cm.) with 2 c.c. of a 50 per cent caustic soda solution, free from carbonic dioxide, and 10 c.c. of 96 per cent (by volume) alcohol on the boiling water-bath for 15 minutes, the flask being connected with an inverted condenser. Next the alcohol is distilled off by immersing the flask for at least half an hour in boiling water, and then 100 c.c. of distilled water are added. The flask is kept for another quarter of an hour, protected from carbon dioxide in the air, in the boiling water-bath to ensure complete solution of the soap. The clear solution is then cooled down to 50°-66° C., but not lower, by allowing water to run over the flask and 40 c.c. of dilute sulphuric acid (25 c.c. of D. O. V. in 1000 c.c. of water; 30-35 c.c. of this acid should neutralise 2 c.c. of the caustic soda used), and two small pieces of pumice are quickly added. The flask is immediately con¬ nected with a condenser, a T piece of 7 mm. diameter with a bulb of 20-25 mm. diameter, and having the side-tube bent twice at an 1 Sulphuric acid might liberate from any potassium chloride present (contained in the commercial caustic potash) hydrochloric acid, which phosphoric acid does not. 2 Chemical Nexus, 53. 20. 3 Jour. Soc. Chern. Ind. 1887, 831. VI REICHERT VALUE 157 angle, being interposed between the two. The contents of the flask are warmed at first by a gentle heat until the insoluble acids are just melted to a clear transparent layer, when the temperature is raised, so that 110 c.c. may pass over in half an hour. The distillate is well mixed by shaking up, and 100 c.c. of it are filtered into a measuring flask. This quantity is poured out into a beaker, and titrated with decinormal baryta solution, phenolphthalein being used as indicator (0‘5 grms. of phenolphthalein dissolved in 1000 c.c. of 50 per cent alcohol). When the solution has become pink, it is poured back into the flask to rinse it out, and baryta added again, until a faint pink colouration remains. The number of c.c. thus found is multiplied by IT. A blank experiment is conducted under exactly the same conditions, and the number of c.c. found—which, however, should not exceed 0‘33 c.c.—subtracted from the result. Sendtner, who maintains that the Reichert-Meissl process yields quite as good results as Wollny’s, adopts the titration with decinormal baryta solu¬ tion, but saponifies in a flask of 300-350 c.c. capacity with 10 c.c. of an alcoholic potash, prepared by dissolving 20 grms. of potassium hydrate in 100 c.c. of alcohol of specific gravity 0 - 889. In order to remove the last traces of alcohol air is blown into the flask-before dis¬ solving the soap. Sendtner’s results differ from Wollny’s by 2T per cent at the most. Working after Wollny’s modification, as a rule, less baryta water is used than in Reichert-Meissl’s process. The well-known fact that in the Reichert distillation process only part of the volatile acids is distilled off 1 has induced some analysts to modify it in the attempt to obtain the total quantity. Thus it has been proposed to repeat the distillation several times with fresh quantities of water. But not only does this take up more time than can be conveniently allowed for a technical analysis, but a cause of error is thereby introduced, as v. Raumer has shown that with each distillation decomposition of the non-volatile acids takes place. Goldmann, again, suggests for the same purpose distillation in a current of steam, which is continued until 100 c.c. of the distillate require no more than 0'05 c.c. of decinormal baryta. His most elaborately detailed process, for a description of which the reader must be referred to the Journal of the Society of Chemical Industry (1888, 238 and 349), is far too complicated for practical use. Besides, if we con¬ sider that in an experiment carried out with 5 grms. of butter fat, the first 100 c.c. required 24'25 c.c., and the following 100 c.c. severally, 1-40, 0-55, 0-35, 0-25, 0*20, 0T5, 0T5, 0-20, 0T0, 0T0, 0T0, until at last the thirteenth 100 c.c. took only 0'05, it looks more like the distortion of a valuable process than a quantitative analysis. At best, Goldmann’s process may be used as a method for completely separating the volatile acids from the non-volatile.— Beal 2 distils in a current of steam, and is satisfied with distilling over 500 c.c. 1 Thus H. D. Richmond states ( Analyst , 1895, 218) that by the Reichert-Wollny process, in the case of butters, only about 87 per cent of the total volatile acids is found in the distillate. I found for 2 - 5 grms. butter by distilling 500 c.c. the number of c.c. decinormal potash required = 22. 2 Jour. Soc. Chevi. Ind. 1895, 197. 158 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. In order to obviate the formation of ethylic ethers of the volatile fatty acids ( Wollny’s second objection), Mansfeld 1 proposes saponifica¬ tion with strong aqueous alkali in a closed flask without addition of alcohol, whilst Schmidt 2 substitutes glycerin for alcohol, as has been done before him by Leffmann and Beam 3 (cp. chap. xi. p. 632). Instead of saponifying the fat with alkali, Kreiss recommends, especially for butter fat, saponification with concentrated sulphuric acid. The volatile acids are then distilled off and titrated, as described above for the Reichert method. The details of the method and a criticism thereof will be given later on under the heading “ Butter Fat” (chap. xi. p. 635). (b) Processes by which the Volatile Fatty Acids are not distilled off. The volatile fatty acids being likewise those soluble in water, several methods have been proposed having for their object the determination of the soluble acids. The values thus obtained nearly coincide with those obtained by the distillation process. 1. Bondzyhski and Ruffs 4 Method. —Four or five grms. of a dry and filtered fat are saponified with 50-60 c.c. of half-normal alcoholic potash, and the excess of potash neutralised with half-normal hydro¬ chloric acid (cp. determination of the Sajxmification Value). The alcohol is evaporated off, the soap decomposed with hydrochloric acid, and the liberated fatty acids washed on a filter with hot water (see p. 160). The insoluble acids are then dissolved in alcohol, and titrated with half-normal hydrochloric acid. By subtracting the number thus found from the quantity used for saponification, the number of c.c. required for the neutralisation of the soluble (volatile) fatty acids will be obtained. The amount calculated for 5 grms. is the Reichert-Meissl value. Thus, if for the saponification of 4‘573 grms. of butter fat 1040 milligrms. KOH, and for the neutralisation of the insoluble acids 910 milligrms. have been used, the difference of 130 milligrms. will correspond to the alkali required for the soluble acids. The soluble acids from 5 grms. of fat require, therefore, 142 milligrms. of KOH, which equals 25‘3 c.c. of decinormal caustic potash (1 c.c. of decinormal caustic potash containing 5’61 milligrms. KOH). The Reichert-Meissl value of the butter fat under examination is, there¬ fore, 25 - 3. 2. The same value can be also obtained directly ( Morse and Burton, 5 Bondzyhski and Ruff Planchon 6 ) by operating in the following manner : —Saponify 4-5 grms. of a fat with 50-60 c.c. of standardised alcoholic potash. Evaporate off the alcohol, dissolve the soap in water, and 1 Jour. Soc. Chem. Ind. 1888, 526. 2 Ibid. 1893, 467. 3 Analyst , 1891, 153 ; cp. also Karsch. Chem. Ztg. 1896, 207. 4 Bondzynski and Rufi, Jour. Soc. Chem. Ind. 1890, 44. 8 Jour. Soc. Chem. Ind. 1888,697. 6 Moniteur scient. 1888, 1096. VI BARYTA VALUE 159 add an amount of standardised sulphuric acid exactly corresponding to the caustic potash used. Filter off the liberated acids, wash with boiling water, and titrate the filtrate with decinormal alkali. The number of c.c. used, calculated for 5 grms. of substance, gives the Reichert-Meissl value. It is evident that by adopting this method the saponification value and Hehner value may be determined in one operation. The saponification value is determined first as described above, by neutralising the excess of caustic potash with standardised hydrochloric acid. The solution is then diluted with water, the alcohol driven off by boiling down, and as much decinormal hydro¬ chloric acid added as exactly liberates the fatty acids, the quantity re¬ quired for which can be easily calculated from the saponification value. Morse and Burton's method will be fully described under “ Butter Fat” (chap. xi. p. 631). 3. G. Firtsch 1 and, after him, J. Kdnig and F. Hart 2 have pro¬ posed to neutralise the soluble fatty acids by baryta, and to determine the latter quantitatively. Firtsch saponifies with an aqueous solution of barium hydroxide in a closed vessel, i.e. under pressure, whilst Kdnig and Hart boil an alcoholic solution of the fat with baryta water under ordinary pressure. It is doubtful whether by these processes complete saponification of the fat can be obtained. Kdnig and Hart operate as follows:—5 grms. of the fat are mixed in a graduated 300 c.c. flask with 60 c.c. of alcohol, the mixture is heated on the water-bath, and 40 c.c. of hot baryta water (17-5 of barium hydroxide in 100 c.c.) added. The flask is connected with an inverted condenser, and its contents are boiled for 3-3 J hours. When cold, water is added to the 300 c.c. mark, and after mixing thoroughly, 250 c.c. are filtered off, and treated with carbonic anhydride until the alkaline reaction has disappeared. The liquid is then evaporated nearly to dryness on the water-bath, allowed to cool, and water added gradually with constant stirring. After making up to 250 c.c., 200 c.c. are filtered off, and the baryta determined in the filtrate by precipitation with sulphuric acid. The barium sulphate obtained is calculated to barium oxide, and expressed in milligrms. The number found is multiplied by 1*5, and this amount of barium oxide, corresponding to 5 grms. of the fat, is termed baryta value. The baryta value indicates the number of milligrammes of BaO con¬ tained in the soluble barium salts from 5 grms. of a fat. Thus a butter fat, the Reichert-Meissl value of which was 27*5, had a baryta value of 236*0. The authors of this method are of opinion that it is simpler and more reliable than Reichert's process. 11. Kreiss and W. Baldinf and Lavesf however, have shown that the baryta method by no means yields any better results than the distillation process. It is unlikely that the “ baryta value ” will obtain much favour among analysts. 1 Dingl. Polyt. Jour. 278. (1890), 422. 2 Jour. Ghem. Soc. 1891 ; Abstracts, 1301. 3 Schweiz. Wochenschr. Ghem. Pharm. 1892, 189. 4 Arch. f. Pharmacie, 1893, 356. 160 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. v. The Hehner Value The Hehner value indicates the proportion of insoluble fatty acids in a fat or wax. This important number may be determined by one of the following methods : (a) Hehner’s Method. 1 —Weigh accurately the purified fat contained in a small beaker furnished with a glass rod, and pour about 3-4 grms. (the exact quantity being determined by re-weighing) into a porcelain dish of about 5 inches diameter. Add 50 c.c. of alcohol and 1-2 grms. of solid caustic potash, and heat on the water-bath with constant stirring until a clear solution is obtained. After about five minutes allow one drop of distilled water to fall into the solution. If the saponification is complete the solution will remain clear; if, however, a turbidity is noticed, the heating must be continued until this test indicates that all the fat has been saponified. Then boil down the clear solution of soap to pastiness, dissolve in 100 to 150 c.c. of water, and acidify with hydrochloric or dilute sulphuric acid. Next heat the liquid until the liberated fatty acids float on the top as a clear oily layer. Filter through a paper of about 4-5 inches diameter, previously dried at 100° C. and accurately weighed. The filter-paper should be of stout material, ordinary filtering paper readily allowing the liquid to run through turbid. A good plan is to have the filter half full of hot water before any fatty matter is transferred on to it, keeping it full till all the liquid is added. Finally wash the fatty acids on the filter with boiling water until a few c.c. of the wash-water does not redden sensitive tincture of litmus. ( Fleischmann and Vieth 2 l’ecommend to wash until the extremely weak acid reaction, produced by 5 c.c. of the filtrate and one drop of tincture of litmus, does not appear to lose its intensity in successive tests.) For 3 grms. of fat sometimes 2000 to 3000 c.c. of wash-water are required in order to completely remove the last traces of the acids occupying an inter¬ mediate place between soluble and insoluble acids (as lauric acid). The washing being completed, immerse the funnel with the filter in a vessel of cold water, so that the water outside and the acids inside are at the same level. As a rule, the fatty acids will solidify. Allow the water then to drain off, transfer the filter to a tared beaker, and dry at 100° C. for two hours. Weigh accurately, dry for another two hours and a half, and weigh again. The difference between the two weights will, as a rule, be below one milligrm. Completely con¬ cordant results cannot be expected, the two chief sources of error, however, tending to compensate each other,—one causing an increase, the other a decrease in weight. For on the one hand the unsaturated acids may become oxidised, whilst on the other hand loss is incurred through a very slight volatilisation of fatty acids (cp. below B. Quant. Determ., etc., p. 180). 1 Zeitsch. f. analyt. Chemie, 76. 145. 2 Ibid. 17. 287. VI HEHNER VALUE 161 (b) Dalicaris Modification. 1 —Helmed s process has been modified by Balkan in the following fashion :—Melt 10 grins, of fat in a flask of 250 to 300 c.c. capacity, and saponify with 80 c.c. of 85 per cent alcohol and a solution of 6 grms. of caustic soda in 6 to 8 c.c. of water on the water-bath. The saponification will, as a rule, be complete after thirty to forty minutes. Leave the flask on the water-bath until all the alcohol has evaporated off, dissolve the soap in 150 c.c. of water, and add gradually, in small quantities, 25 c.c. of hydrochloric acid (1 volume of concentrated acid diluted with 4 volumes of water), agitating the contents of the flask after each addition of acid. Heat the flask for another thirty minutes on the water-bath, until the fatty acids have separated on the top as a transparent oily layer, then remove the flask from the bath and cool thoroughly. After about two hours break the cake of fatty acids with a glass rod, and pour off the liquid through a plain filter. Then melt the fatty acids over 100 c.c. of boiling water and add 150 c.c. more boiling water. Allow to stand forty minutes, cool thoroughly, and proceed as before. Repeat this process of washing until litmus paper dipped in the wash- water does not turn red after twenty minutes’ standing. As a rule, eight to ten washings will be found sufficient for the complete removal of the soluble fatty acids. Next transfer the insoluble fatty acids to a porcelain dish, and wash the flask thoroughly with boiling water, passing all the wash-waters through the filter, which must be kept moist, so as to allow the small quantity of fatty acids adhering to it to be easily united with the bulk. Finally heat the dish from 100° to 110" C. for one hour at first, and then, after weighing, again for twenty minutes until the weight remains fairly constant. (c) Hager modifies Helmeds method by melting together with the fatty acids a weighed quantity of paraffin wax or bleached beeswax, as is usually done in soap analysis (chap. xii. p. 774), and washing four times with water containing 20 per cent of alcohol. This modi¬ fication does not give such exact results as the preceding methods. (d) Knight’s Process . 2 — J. West Knight rejects Hehneds process on account of the difficulty of avoiding losses during the various opera¬ tions, and proposes another method based on the insolubility of the barium salts of the higher fatty acids in water on the one hand, and on the ready solubility of the barium salts of the volatile acids on the other. The following is a description of Knight’s process :—1-3 grms. of the dried and filtered fat is saponified by heating on the water-bath with twice its volume of alcoholic potash for about half an hour. The solution is then brought up to 300 c.c. with cold distilled water, and an aqueous solution of barium chloride added until no further pre¬ cipitation takes place. The precipitate is collected on a filter, washed with warm water, and then transferred to a Muter tube. Next the barium salts are decomposed with hydrochloric acid, and the liberated fatty acids shaken up with ether, in which they dissolve easily. The ethereal solution is made up to 100 c.c., and an accurately measured 1 Moniteur scient. 12. 989. 2 Analyst. 1881. M 162 CHEMICAL METHODS OF EXAMINING FATS AND WAXES CHAP. quantity—say 50 c.c.—run off into a weighed flask. The ether is then distilled off and the dried residue weighed. A priori, it is open to doubt whether Hehner’s and Knight’s methods will yield concordant results, inasmuch as the solubility of the acids may not correspond to the solubility of their barium salts. However, as Knight’s results agree closely with those obtained by Hehner’s process, it must be considered a correct method, although the use of an ethereal solution and the measuring off of an aliquot part may possibly introduce errors. 1 vi. The Aeetyl Value The acetyl value furnishes a measure of the proportion of hydroxy acids or free alcohols, or of both together, in a fat or wax (provided mono- or diglycerides are absent). The method of determining the acetyl value, as proposed by Benedikt, is based on the principle that hydroxy acids and alcohols, on being heated with acetic anhydride, exchange the hydrogen atom of their alcoholic hydroxyl group or groups for the radicle of acetic acid according to the following equations :— 1. C 17 H 32 (OH). C00H + (C 2 H 3 0 2 )0 = C 17 H 32 (0 . C 2 H 3 0)C00H + C 2 H 4 0 2 . Ricinoleic acid. Acetic Acetyl-ricinoleic acid. Acetic anhydride. Acid. 2. C ]S H 3 ,. OH + (C 2 H 3 0) 2 0 = C 16 H 33 0 . C 2 H 3 0 + C 2 H 4 0 2 . Cetyl Acetic Cetyl acetate. Acetic alcohol. anhydride. acid. The acetyl value of fatty acids is determined, according to Benedikt and Ulzer , 2 in the following manner:—20 to 50 grms. of the insoluble fatty acids prepared in the usual manner (p. 99) are boiled with an equal volume of acetic anhydride for two hours in a round-bottomed flask attached to an inverted condenser. The mixture is then transferred to a beaker of 1 litre capacity, mixed with 500 to 600 c.c. of water and boiled for half an hour, a slow current of carbonic dioxide being at the same time passed into the liquid through a finely-drawn-out tube reaching nearly to the bottom of the beaker; this is done to prevent bumping. The mixture is then allowed to separate into two layers, the water is syphoned off, and the oily layer again boiled out in the same manner three successive times. The last trace of acetic acid is thus removed, as may be ascertained by testing with litmus paper. The acetylated acids are filtered through a dry filter-paper in a drying oven to remove water, and a portion of the product, say 3 to 5 grms., is weighed off accurately in a flask and dissolved in pure alcohol. Then proceed exactly as for the determination of the acid value (p. 148) and saponification value 1 Asboth states that also the lead salts of the volatile acids are soluble in water. But as his paper does not give any proof for this assertion, his statement must be accepted with reserve. 2 Monatshefte fur Chemie, 8. 40. ACETYL VALUE 163 vt (p. 151). Add a little phenolphthalein, and titrate with half-normal potash until pink, whereby the free acid is neutralised. The acid value thus obtained is termed “ acetyl acid value.” Then run into the flask an accurately measured quantity of alcoholic potash, standardised by half-normal hydrochloric acid, heat to boiling, and titrate back the excess of alkali. The amount of alkali now used gives the “ acetyl value” The sum of the acetyl acid value and of the acehjl value is termed “ acetyl saponification value.” The acetyl value is therefore equal to the difference of the saponification and acid values of the acetylated fatty acids. The acetyl value of the, fatty acids indicates the number of milli¬ grammes of KOH required for the neutralisation of the acetic acid obtained on saponifying one gramme of the acetylated insoluble fatty acids. Example. —3‘379 grms. of the acetylated fatty acids from castor oil were neutralised by 17'2 c.c. of half-normal potash, i.e. 17‘2 x 0'02805 grm. = 04825 grm. KOH; hence the acetyl acid value is 142'8. Then 32 - 8 c.c. more potash were added, and, after boiling, the excess titrated back with 14*3 c.c. half-normal hydrochloric acid. The acetic acid obtained on saponification therefore required for neutralisation 32*8-14‘3 c.c. = 18*5 c.c. half-normal potash, or 18*5 x 0’02805 = CL5189 grm. KOH. Hence the acetyl value 5189 l«.fi 3379= 163 6 Therefore, Acetyl acid value .... . 142-8 Acetyl value ..... . 153-6 Acetyl saponification value . 296-4 The neutralisation and the saponification of the acetylated acids were therefore supposed to take place in two stages according to the following equations :— 1. C 17 H 32 (0 . C 2 H 3 0). COOH + KOH = C 17 H 32 (0 . C 2 H 3 0)G00K + H 2 0. Acetyl-ricinoleic acid. Potassium salt. 2. C l7 H 32 (0 . C 2 H 3 0)C00K + KOH = C l7 H 32 (OH)COOK + C 2 H 3 0 2 K. Potassium acetyl-ricinoleate. Potassium ricinoleate. The hydroxyl in the carboxyl group of the fatty acids should therefore not have been affected by the acetic anhydride during the acetylating process. Hence fatty acids containing no alcoholic hydroxyl, such as stearic, oleic, etc., should not yield an acetyl value, the acid and saponification values in that case being identical. Lewkowitsch, 1 however, has shown that pure capric, lauric, palmitic, stearic, cerotic, and oleic acids gave very considerable acetyl values when treated according to Benedikt and Ulzer’s process. This result could only be explained by the fact that the fatty acids had been con- 1 Proceed. Chem. Soc. 1890, 72 ; 91 ; Jour. Soc. Chem. Lid. 1890, 660. 164 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. verted into their anhydrides, the acetic anhydride acting in the manner explained by the following equation :— C 2 H 3 0\ c 15 h 31 co\ 20 “ h »-Oooh + o sH » o/ o= CiiHj ,o 0/ o + 2°*o-oh. Palmitic acid. Acetic Palmitic Acetic acid, anhydride. anhydride. The anhydrides were thus actually obtained and their great stability in presence of even boiling water proved. When these anhydrides were dissolved in cold alcohol for the pur¬ pose of titrating, on adding the potash hydrolysis (saponification) of the anhydrides took place at once to a certain extent, and as the acid combined with a certain quantity of potash, an (apparent) acid value of the substance was obtained. When, however, the anhydrides were shaken up with water , the first drop of potash gave a pink colouration (in the presence of phenolphthalein), which disappeared but slowly. Thus in the alcoholic solution a partial hydrolysis of the anhydrides took place, hydrolysis ceasing when an equilibrium was established in the solution. Under these conditions apparent acetyl values were obtained for the fatty acids above mentioned, being, in truth, nothing but fictitious values. Hydroxylated fatty acids are certainly acetylated when boiled with acetic anhydride, but simultaneously the acetylated acids are converted into their anhydrides in consequence of the large excess of acetic anhydride used. During the subsequent boiling with water a portion of the anhydrides may or may not become hydrolysed, thus yielding possibly a mixture of free acetylated acids and acetylated anhydrides. When this is dissolved in alcohol and titrated with caustic potash, after neutralisation of the free acids, if any, partial hydrolysis will set in, as explained above in the case of capric acid, etc., and an acid value will thus be obtained ( Benedild’s “ acetyl acid value ”). But such acid value will be lower than the true acid value of the acetylated fatty acids, the anhydrides remaining unacted on to a certain extent. Consequently the saponification value of the acetylated product ( Benedikt’s “ acetyl saponification value ”) will be found too high, the not-hydrolysed anhydrides becoming then saponi¬ fied by the boiling alcoholic potash. The difference between saponi¬ fication and acid values, supposed to be the acetyl value of the acids, will therefore be devoid of any quantitative meaning. The same conclusion, of course, holds good in the case of a mixture of hydroxy and ordinary fatty acids. The true acetyl value of the fatty acids, however, is found, accord¬ ing to Lewkowitsch, 1 by actually titrating the amount of acetic acid assimilated by the hydroxy acids in the form of acetyl (C 2 H 3 0) and given up, on saponification, as acetic acid to the alkali. This is done by boiling the acetylated product with alcoholic potash and estimating 1 Jour. Soc. Chem. Ind. 1890, 846. VI ACETYL VALUE 165 the acetic acid formed in a similar fashion to that adopted in the determination of volatile fatty acids by Reichert's distillation process. There is, however, this important difference that the total amount of volatile acids, in the present case acetic acid, is driven off. The dis¬ tillation is therefore carried on until practically no acidity is shown by the distillates. This occurs as a rule when about 500 to 700 c.c. have been distilled over. The distilled liquors are then titrated with decinormal alkali, phenolphthalein being the indicator. The number of c.c. of decinormal potash used per gramme of the acetylated sub¬ stance multiplied by 5 - 61 represents the acetyl value of the fatty acids. Example. —3'364 grms. of the acetylated fatty acids from Sawarri fat yielded a distillate requiring 8'4 c.c. of decinormal potash for neutralisation. Hence for 1 grm. 2‘5 c.c. decinormal potash were used. Therefore the acetyl value is 2’5 x 5*61 = 14 - 03. It is therefore evident that the “ acetyl values ” found by various observers working according to Benedikt and Ulzer’s method cannot be accepted as correct. The determination of the acetyl value by Lewkowitsch’s method, though giving correct results, has the important drawback that this constant refers to the insoluble fatty acids rather than to the oils and fats themselves. This naturally tends to obliterate at the outset important differences existing between the various glycerides, for in the process of preparing the fatty acids volatile acids are washed away, and the characteristic differences of such fats as, e.g., butter and tallow, may entirely disappear. There is the further drawback that during the operations entailed by washing and drying the fatty acids they may become oxidised with formation of hydroxy acids. In order to bring this important constant into line with the other constants, Lewkowitsch 1 determines the aeetyl value of the glycerides Themselves. He proceeds as follows:—10 grms., or any other con¬ venient number of grammes, are boiled with an equal volume of acetic anhydride in the manner described above. The acetylated product when washed free from acetic acid is separated from water and filtered through filtered paper in a drying oven. This operation may be carried out quantitatively, and in that case the fatty matter is treated in a similar fashion to the modus operandi described for the determination of the Hehner value (p. 160). It may be useful to work quantitatively if it is desired to ascertain preliminarily whether a notable amount of hydroxy acids is present in an unknown fat (cp. chap. vi. p. 204, and chap. vii. p. 232). 2 to 4 grms. of the acetylated product are then saponified by boiling with alcoholic potash, as in the determination of the saponifi¬ cation value. If the “ distillation process ” be adopted, it is not necessary to work with an accurately measured quantity of stand¬ ardised alcoholic potash. In case the “ filtration process ” be used, the alcoholic potash must be measured exactly. (It is advisable to use in either case a known volume of standard alkali, as one is then 1 Jour. Soc. Chem. Ind. 1897, 503. 166 CHEMICAL METHODS OF EXAMINING FATS AND WAXES CHAP. enabled to determine the saponification value of the acetylated oil or fat). Next the alcohol is evaporated off and the soap dissolved in water. From this stage the determination is carried out either by (a) the distillation process, or ( b ) filtration process. (a) Distillation process. —Add dilute sulphuric acid (1:10), more than to saturate the potash used, and distil the liquid as is usual in Reichert's distillation process. Since several hundred c.c. of water must be distilled off, either a current of steam is blown through the sus¬ pended fatty acids, or water is run into the distilling flask from time to time through a stoppered funnel fixed in the cork, or any other convenient device may be adopted. It will be found that it is suffi¬ cient to distil off 500 to 700 c.c. of water, as the last 100 c.c. require no more than 0T c.c. of decinormal alkali. Then titrate the distillates with decinormal potash, phenolphthalein being the indicator, multiply the number of c.c. by 5'61, and divide by the weight of substance taken. This gives the acetyl value. (b) Filtration process. —Add to the soap solution a quantity of standardised sulphuric acid exactly corresponding to the amount of alcoholic potash employed and warm gently, whereupon the fatty acids will readily collect on the top as an oily layer. (If the saponi¬ fication value has been determined, it is of course necessary to take into account the volume of acid used for titrating back the excess of potash.) Filter off the liberated acids, wash with boiling water until the washings are no longer acid, and titrate the filtrate with decinormal alkali. The acetyl value is calculated in the manner shown above (a). Both methods give identical results ; the latter will be found shorter and therefore more convenient. We now arrive at the definition :— The acetyl value indicates the number of milligrammes of KOH required for the neutralisation of the acetic acid obtained on saponifying one gramme of the acetylated fat or wax. In the case of those oils and fats which have a high Reichert value (cp. Croton Oil, chap. ix. p. 313) the apparent acetyl value would be too high, owing to the presence of the volatile acids. Their influence will make itself felt to a greater extent in the distillation process than in the filtration process. To eliminate this error determine the volatile acids of the original oil or fat in precisely the same manner, and deduct the value thus obtained from the apparent acetyl value. It should be noted that in the case of a fat containing fpee alcohols 1 (phytosterol, cholesterol), or in the case of waxes, the acetyl value will be a measure of both the hydroxy acids and the free alcohols. If the free alcohol is isolated its acetyl value (see below) may be determined as well. The difference between the acetyl value of the fat or wax and the acetyl number proportionate to the amount of free alcohol present will be the true measure of the hydroxy acids. If a free alcohol is acetylated no complication through formation of anhydrides can arise, and in that case simply the saponification 1 If mono- or diglycerides (see p. 190) be present, acetic acid radicles are also absorbed by them. VI BROMINE VALUE 167 value of the acetylated product—the acetate of the alcohol—is deter¬ mined. This value is also the acetyl value of the alcohol (the saponification value of the original alcohol being, of course, nil). vii. The (Bromine or) Iodine Value The (bromine or) iodine value indicates the percentage of (bromine or) iodine absorbed by a fat or wax. This value is, therefore, a measure of the proportion of unsaturated fatty acids in a fat,—these acids, both in their free state and in com¬ bination with glycerol, having the property of assimilating the halo¬ gens with formation of additive compounds. Theoretically, the acids (or their glycerides) belonging to the oleic and ricinoleic series should absorb two atoms of chlorine, bromine, or iodine; similarly the acids of the linolic series should assimilate four atoms, the members of the linolenic series six atoms of the halogens, etc. Obviously the determination of absorbed chlorine is attended with more difficulty than that of bromine or iodine, and the latter reagents only have been found useful in technical analysis. (a) Bromine Value If dry bromine is allowed to act on an oil, the former is absorbed, a more or less violent reaction taking place and hydrobromic acid being evolved. The reaction must therefore be moderated by pre¬ viously dissolving both the bromine and the oil in a suitable solvent. The determination of bromine absorption values was proposed by Cailletet (1857), but the application of this method for the analysis of fats is due to Mills 1 and his collaborators Snodgrass and Akitt. Mills proceeds as follows:—OT grm. of a fat, dried thoroughly and filtered, is dissolved in 50 c.c. of carbon tetrachloride contained in a narrow-mouthed stoppered bottle of 100 c.c. capacity. To this solution is added standard bromine solution in carbon tetrachloride (about 0'006 - 0’008 grm. per c.c.) until there is at the end of fifteen minutes a permanent colouration. The excess of bromine can be measured either by comparing the colouration with that similarly produced in a blank experiment, or, more accurately, by titrating back with a standard solution of /3-naphthol in carbon tetrachloride, when monobromnaphthol is formed. The bromine absorbed is calcu¬ lated for 100 grms. of fat. The average probable error is stated to be 0'46 per cent. Mills laid the greatest stress on the necessity of rigidly excluding moisture, since he observed that the bromine absorption increased in presence of water; therefore aqueous solutions of bromine must not be used. Carbon tetrachloride was substituted for carbon bisulphide as a solvent for bromine, for the reason that the solution of bromine 1 Jour. Soc. Chem. Ind. 1883, 435 ; 1884, 366. 168 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. in the former possesses much greater stability at the ordinary temperature than in the latter. 1 Instead of /3-naphthol, potassium iodide may be added, and the liberated iodine titrated with sodium thiosulphate, calculating to bromine.—Other chemists determine the bromine absorption by methods deviating from Mills’ directions in essential points. Levallois 2 saponifies 5 grms. of fat with alcoholic potash, and makes the solution up to 50 c.c. To 5 c.c. of it he adds hydrochloric acid, and then standardised aqueous bromine solution, until a per¬ manent yellow colouration is noticed. The bromine solution used by Levallois is as concentrated as possible. No wonder, therefore, that the bromine absorptions obtained by this method differ very materially from those obtained by Mills, whose figures undoubtedly deserve more confidence (see p. 308). Halphen 3 operates in the following way :—1 grm. of the fatty acids, weighed off accurately, is placed in a bottle of 250 c.c. capacity, dissolved in 20 c.c. of carbon bisulphide, and an accurately measured quantity of a standardised aqueous solution of bromine allowed to run in. There should be an excess of at least 0'5 grm. of bromine. The solution is thoroughly mixed by shaking, and allowed to stand for fifteen hours, when the excess of bromine is titrated back by a standard caustic soda solution prepared by dissolving 2 grms. of eosin in 20 c.c. of caustic soda of 36° B6., and making up to 1000 c.c. The alkali solution is standardised by running it gradually from a burette into a bottle containing 20 c.c. of carbon bisulphide and exactly 10 c.c. of a bromine solution of known strength, shaking well after each addition of the caustic soda. At first the liquid acquires a brownish colouration, and becomes successively yellowish-brown, then nearly colourless, and at last rose-coloured. The titer of the caustic soda is expressed in terms of bromine. This standardation need only be carried out once for all; the bromine value of any fresh caustic soda solution in reference to any fresh bromine solution being ascer¬ tained by comparison with the once standardised caustic soda. Of course the titer of the bromine solution must be ascertained before each determination of the bromine absorption. Schlagdenhauffen and Braun 4 reject Levallois’ method as inaccurate, and substitute for it the following process :—Dissolve 2‘5 grms. of a fat in 50 c.c. of chloroform (or carbon bisulphide), and add to an aliquot part of the solution—say 10 c.c.—a measured volume of a solution of 1 grm. of bromine in 100 c.c. of chloroform, until the yellow colouration does not disappear on shaking. Then add 10 c.c. of a dilute solution of potassium iodide and a few drops of starch solution, and titrate with sodium thiosulphate. Mills’ process should be preferred to the others mentioned. Mills, however, overlooked the fact that the formation of hydrobromic acid is 1 The following reaction going on in a solution of bromine in carbon bisulphide should be noted as involving loss of bromine. After several days’ standing CS 2 Br 4 is formed ; this is decomposed by water (moisture) with separation of crystals of (CBr,)„S,. 2 Compt. rend. 104. 371. 3 2 3 3 Jour. Pharm. Chevi. 1889 (5), 20. 247. 4 Ibid. 1891 (5), 23. 97. VI BROMINE VALUE 169 not due to moisture but to the substitution of hydrogen in the molecule of the fatty substance. (The hydrobromic acid thus formed can be detected by shaking the product with water and testing the aqueous solution with silver nitrate.) Thus concurrently with the addition, i.e. the absorption of bromine due to two atoms of bromine being assimilated by one molecule of an oil to form a saturated compound, there takes place further absorp¬ tion of bromine with formation of substitution products and conse¬ quently of hydrobromic acid; therefore the total absorption of bromine as measured by the methods just described is due to both addition and substitution. The more concentrated the bromine solution employed the greater will be the amount of substitution products; it is therefore evident that bromine values obtained by allowing dry bromine to act on an oil must be too high. The quantity of hydrobromic acid formed furnishes, therefore, a measure of the amount of substitution that has taken place. Hence the true bromine value is expressed by the difference between the total bromine assimilated and the bromine absorbed in the substi¬ tution process. M c Ilhiney 1 determines the “ bromine addition ” and the “ bromine substitution ” value of an oil in the following manner 2 :— From 025 to l'OO grm. of the oil is dissolved in 10 c.c. of carbon tetrachloride in a 500 c.c. stoppered bottle, an excess of a solution of bromine in carbon tetrachloride is added, and the mixture kept in a dark place for 18 hours. The bottle is then placed in ice so as to obtain a partial Vacuum by the condensation of the vapours. A piece of india-rubber tubing is now slipped over the neck so as to form a well around the stopper. The well is filled with water, which is sucked into the bottle when the stopper is carefully lifted. 25 c.c. of water are thus introduced into the bottle, its contents are well shaken, to effect absorption of the hydrobromic acid, and 10-20 c.c. of a 20 per cent solution of potassium iodide, and about 75 c.c. more water added. The iodine liberated by the excess of bromine is measured by titration with standard thiosulphate solution and calculated to bromine. The total amount of bromine added having been ascer¬ tained similarly in a blank test, the difference between the two amounts corresponds to the total bromine absorption, and it is calculated to units per cent of the oil taken. The contents of the bottle are transferred to a separating funnel, and the aqueous solution is separated and filtered. If it be blue it is decolourised by a few drops of thiosulphate solution, and the free acid determined as hydrobromic acid by titration with decinormal alkali, methylorange being used as an indicator. The bromine calcu¬ lated from the hydrobromic acid and expressed in per cents of the oil gives the bromine substitution value. Twice this number sub¬ tracted from the total bromine absorption gives the bromine addition number. 1 Jovr. &be. Chem. Ind. 1894, 668. 2 Cp. Allen. Com. Org. Analys. ii. 384. 170 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. It is evident that the substitution number must be doubled, since for each bromine atom that has been converted into hydrobromic acid there have been removed from the original bromine solution 1 molecule, or 2 atoms of bromine, as explained by the following equation :— C n H m 0 2 + Br 2 = C„H m _ jOoBr + HBr. Fatty Acid. Bromosubstitution product. The following gravimetric process for the determination of the bromine value has been proposed recently by Hehner 1 :—Weigh off accurately 1 to 3 grms. of the oil in a wide-mouthed flask, and dissolve the oil in a few cubic centimetres of chloroform. Then add pure bromine, drop by drop, until there is an excess of bromine. Heat the flask on the water-bath until the bulk of the bromine is driven off, add a little more chloroform, and heat again so as to promote the evaporation of the bromine by the vapours of the chloroform. This operation may be repeated so as to ensure complete volatilisation of the bromine in excess. The contents of the flask are finally heated at 125° C. until the weight remains constant. This takes several hours, a little acrolein and hydrobromic acid escaping during the drying. The gain in weight expressed in per cents gives the bromine value. Essentially the same method has been described, independently, by Waller . 2 LewJcowitsch, 3 however, has shown that whilst in a number of cases (i e.g . olive oil) this method leads to results agreeing with those obtained by Hiibl’s standard method (see below), in other cases such enormous discrepancies are observed that this gravimetric method cannot find a place amongst the quantitative processes. (b) Iodine Value The determination of the bromine value has been wholly super¬ seded by HubVs method of ascertaining the iodine absorption value, which yields by far more constant and reliable results. 4 In fact, the reliability of the recently proposed bromine absorption processes is ascertained by their agreement with Hubl’s process, bromine values being calculated into iodine values by multiplication with = T5875. But it should be distinctly understood that the bromine values are not directly convertible into iodine values, as a varying amount of substitution takes place which is decidedly smaller in the case of the iodine, if any takes place at all, as one may conclude from the action of iodine on saturated fatty acids (p. 176). 1 Analyst, 1895, 50. 2 Ibid. 1895, 280. It should be noted that Waller examined olive oil only. 3 Jour. Soc. Chem. Ind. 1896, 859. 4 Hydroxybrassidic acid does not absorb bromine at ordinary temperature (Berichte, 26. 839). Cp. p. 308. VI IODINE VALUE 171 Hiibl 1 found that iodine is only slowly assimilated by fats at •ordinary temperature, whilst at higher temperatures 2 the action of iodine becomes very irregular, complicated reactions taking place. He has ascertained, however, that from an alcoholic solution of iodine, in presence of an alcoholic solution of mercury bichloride, the unsaturated fatty acids or their glycerides absorb iodine in a very regular, well-defined manner, so that a quantitative method may be based on this reaction. The following solutions are required . for Hiibl’s process :— 1. Solution of Iodine and Mercury Bichloride, called hereafter Iodine Solution for brevity’s sake.—This is prepared by dissolving on the one hand 25 grms. of iodine, and on the other hand 30 grms. of mercury bichloride, in 500 c.c. of pure 95 per cent alcohol, filtering the latter solution if necessary, and then mixing both solutions. The iodine solution undergoes considerable reduction in strength ( i.e. free iodine) during the first hours after mixing, and should, therefore, be allowed to stand for twelve to twenty-four hours before use. But even after that time the iodine solution gradually loses strength in consequence of formation of hydriodicacid, 3 and must, therefore, be always standardised immediately before use. The writer finds it very convenient to keep both the iodine and the bichloride solution in stock separately, and prepare only so much iodine solution as is required for a test. 2. Solution of Sodium Thiosulphate (hyposulphite).—This is pre¬ pared by dissolving about 24 grms. of the crystallised salt in 1000 ■c.c. of water, and is standardised by means of iodine in the following way :—Two short glass tubes, sealed at one end, and of such dimen¬ sions that one fits with slight friction into the other, are heated and allowed to cool in the desiccator. Now transfer to the inner tube about 0 - 2 grm. of pure resublimed iodine, lay the tube obliquely in a sand-bath, heat till the iodine melts, then remove the tube, and allow it to cool a little in an oblique position, until it can be held with the hand. Place the larger tube over it, allow to cool in the dessicator, and weigh accurately. Then take the wider tube off, and place both tubes in a stoppered bottle containing 1 grm. of potassium iodide dissolved in 10 c.c. of water. As soon as the iodine is dis¬ solved, add water, and allow the thiosulphate to run into it from a burette until the colour is nearly all gone. Now add a little starch solution, and then carefully, with constant agitation, drop by drop of the thiosulphate until the blue colour is just being discharged. 1 Jour. Soc. Chem. Ind . 1884, 641. 2 Cp. also footnote, p. 173. 3 Schweitzer and Lungwitz {Jour. Soc. Chem. Ind. 1895, 133) examined an iodine solution containing 0'6201 grm. total iodine in stated intervals, with the following result : — After hours Free Iodine. Iodine as Hydriodic Acid. 12 0-6181 0-0020 36 0-6136 0-00653 S4 0-5930 0-02713 132 0-5849 0-03517 172 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. Another very convenient method for standardising the thiosul¬ phate, due to Volhard , is the following:—Weigh off accurately 3'8747 grins, of pure potassium bichromate, 1 and dissolve in 1000 c.c. of water. Place in a stoppered bottle 10 c.c. of a 10 per cent potas¬ sium iodide solution, and 5 c.c. of hydrochloric acid, and run in exactly 20 c.c. of the bichromate solution from a burette. Since each c.c. of this solution liberates precisely 0'01 grm. of iodine, altogether 0 - 2 grm. of iodine will be set free. It is titrated by means of the thiosulphate solution as described above. The advantage of this method lies in its rapidity, saving the somewhat laborious and circumstantial preparation and weighing off of the pure iodine; besides, the bichromate solution, keeping for an indefinitely long time without alteration, is always ready for ascertaining the strength of the thiosulphate solution. 2 3. Chloroform. —The chloroform should be pure. It is tested by mixing 10 c.c. with 10 c.c. of the iodine solution, and titrating the free iodine after two to three hours’ standing. The amount found should be exactly the same as that contained in 10 c.c. of the iodine solution. (Ether cannot be used in place of chloroform, as it very frequently contains hydrogen peroxide, which acts on potassium iodide, liberating iodine.) 4. Solution of Potassium Iodide. —This is prepared by dissolving 100 grms. of potassium iodide in 1000 c.c. of water. 3 5. Starch Solution. — This should be prepared afresh for each analysis by stirring 0’5 grm. of pure starch in cold water, and heating to the boiling point with constant stirring. The determination of the iodine value is carried out as follows :— From 0T5 to 0T8 grm. of a drying, or a fish oil, 0 - 3 to 0’4 grm. of a non-drying oil, or 0'8 to 1‘0 grm. of a solid fat, are weighed oft' accurately, and placed in a bottle of 500 to 800 c.c. capacity provided with a well-ground stopper. The fat is dissolved in 10 c.c. of chloro¬ form, and 25 c.c. of the iodine solution run in by means of a pipette inserted in the reagent bottle. The pipette is always emptied in exactly the same manner; this is best done by allowing it to drain until say three drops have run out. For larger quantities of fats, say 0'30 to 0’36 grm., etc., 50 c.c. must be used. In order to prevent loss of iodine by volatilisation it will be found useful to moisten the stopper with potassium iodide solution. The chloroform and iodine solution should give a clear solution on shaking, otherwise more chloroform must be added. Should the deep brown colour of the solution become discharged after a short time, another 25 c.c. of the iodine solution must be run in, an excess of iodine being required for the reaction. The solution must, after two hours, still posses& 1 It is necessary to ascertain its purity and absence of sodium bichromate by deter¬ mining its oxidising value. 2 For a method of standardising by means of BaSofb, cp. Plumpton and Chorley, Proc. Chem. Soc. 1895, p. 38. 3 Commercial potassium iodide frequently contains iodate, which gives free iodine with hydrochloric acid. Such impure iodide may, however, be employed if accurately measured volumes be used and the liberated iodine be taken into account. VI IODINE VALUE 173 a deep brown colour. After that time the reaction should be com¬ plete, but in order* to be quite safe it is best to allow the solution to stand another two hours at ordinary temperature protected from light. From 15 to 20 c.c. of the potassium iodide solution are then run in, and the liquid shaken and diluted with from 300 to 500 c.c. of water. A red precipitate of mercury iodide would indicate that an insufficient quantity of potassium iodide had been employed, and therefore more must be added. The excess of free iodine, part of which will be in the aqueous solution, whereas the remainder is dissolved in the chloroform, is titrated with the thiosulphate solution, by running it into the bottle until after repeated agitation both the aqueous and the chloroformic layers are but faintly coloured. A few drops of the starch solution are next added and the titration brought to an end. Immediately before or after this tritration the amount of iodine con¬ tained in 25 c.c. of the original iodine solution is estimated. The difference between the two results corresponds to the iodine assimi¬ lated, and this is calculated to units per cent of the fat. The figure thus found is termed the iodine value. The values as obtained by Hull’s method are quite constant, provided an excess of iodine of not less than 30 per cent 1 be em¬ ployed, and the operations be carried out under exactly the same conditions. The result does not depend on the concentration, nor on an excess of the mercury bichloride solution, but it is necessary that for every two atoms of iodine at least one molecule of mercury bichloride should be present. Hull remarks that it is indifferent whether the titrations are made after two or after forty-eight hours’ standing—which is not quite borne out by the experience of other analysts, including the writer. To ensure concordant results it is preferable not to titrate before four to six hours’ standing, but it is not advisable to wait any longer. 2 When the titrated solution is allowed to stand for some time the solution becomes blue again; this is no doubt due to the splitting off of iodine, thus proving that the action of iodine on unsaturated compounds is to some extent a reversible reaction. However, this action does not in the least interfere with the accuracy of the titration. Hull’s process has been examined by many chemists, and proved itself to be one of the most valuable methods employed in the technical analysis of fats and waxes. The chemical literature of the last few years contains numerous papers by various authors purport¬ ing to give improvements or modifications of the original method. Most of them refer simply to minor or unimportant points. Some of them even reproduce methods which Hull , in his classic paper, has rejected. 1 Benedikt, Zeit.f. Cliem. Ind. 1887, 213. 2 With a view to shorten the time of treatment Schweitzer and Lungwitz {Jour. Soc. Cliem. Ind. 1894, 616) heat the liquid in the tightly-closed bottle for twenty-five minutes at 45° C., and titrate when the liquid has cooled down. This method cannot be recommended. 174 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. Thus, it has been proposed to employ mercury bibromide instead of the bichloride ( Saytzeff ); further, to use methyl 'alcohol instead of alcohol as a solvent ( Fahrion ), or a mixture of acetic acid and ethyl acetate or ether (see p. 172) ( Welmans ).—The exact excess of iodine to be employed is still a matter of controversy between some con¬ tinental chemists ( Holde , Fahrion , Dieterich ); the same obtains as to the length of time required for the iodine to act on the fat ( Thomson and Ballantyne, Dieterich). —Several chemists recommend a blank test, using the same amount of chloroform and iodine solution ; but there again they seem to leave it open to doubt as to which titer of the blank test should be used for calculation, whether that found before the actual test is started, or that at the end of the titration, or the mean of both.— Gantt er, 1 evidently having neglected HiibVs direction that for 2 atoms of iodine at least 1 molecule of HgCl 2 should be used, recently proposed what he calls a “ new method for estimating the iodine absorption.” He omits the mercury bichloride, and allows only the iodine, dissolved in carbon tetrachloride, to act on a solution of fat in the same menstruum. Hull himself had abandoned the employment of iodine alone as being too slow of action, and it has been shown since ( Schlagdenhauffen and Braun , Fahrion) that the mercury bichloride is indispensable for the attainment of constant results. Gantter employs for 1 part of fat 4-5 parts of iodine, and allows to stand for fifty hours. The iodine values thus obtained are considerably lower than HiibVs iodine absorptions, and are entirely devoid of that quantitative meaning which HiibVs values possess, the latter indicating approximately figures which are postulated by theory for additive compounds (see table below). Gantter's values, even if they should be constant, which has yet to be proved by a larger number of experiments, will at best only cause confusion, a great number of iodine absorption values by HiibVs process having been recorded in the literature as constants for certain fats. M c Ilhiney 2 has since shown that Gantter's method does not even yield constant results. Therefore the latter’s suggestion must be considered value¬ less. Waller , 3 with a view to render the iodine solution more stable, proposes to add some hydrochloric acid. He prepares the solution in the following manner :—25 grms. of iodine are dissolved in 250 c.c. of strong alcohol; 25 grms. of mercury chloride are then dis¬ solved in 200 c.c. of strong alcohol, 25 grms. of hydrochloric acid, spec. grav. IT9, are added, and both solutions mixed and made up to 500 c.c. with alcohol. It will be noticed that Waller’s solution does not conform to HiibVs direction that there should be at least one molecule of mercury bichloride (27'5 grms.) to one molecule of iodine (25T grms.), as also that this solution is twice as strong as the usual iodine solution. Nevertheless the values obtained with this solution are stated by Waller to practically agree with those by the Hiibl process, and this statement has been confirmed by Dieterich , 1 Jour. Soc. Chem. Ind. 1893, 717. 2 Ibid. 1895, 197. 3 Analyst, 1895, 280. VI IODINE VALUE 175 Pelgry , and Henriques. But this alleged slight advantage does not offer, in the writer’s opinion, sufficient inducement to deviate from a standard method.—The same would apply to Ephraim’s suggestion to replace the iodine solution by iodine chloride (see below). The chemical reaction taking place when HiibVs iodine solution is made to act on a fat is not known yet. Hubl assumes that chloro-iodo- additive compounds result, having obtained from oleic acid a greasy substance, to which he ascribes the formula C 18 H 34 C1I0 2 (see p. 14). Liebermann 1 thinks it possible that addition of chlorine only may take place. However this may be, from a practical point of view it is unimportant whether only iodine or chlorine enter into union with the fats, or if both, in what proportions, since the amount of halogen absorbed is estimated volumetrically and calculated in terms of iodine. In the subjoined table the theoretical iodine values for some unsaturated fatty acids are given, together with some experimental data obtained hitherto. Fatty Acid. Formula. Atoms of Iodine required to form 100 Grins, of Acid absorb Iodine. Observer. a saturated com¬ pound. Theory. Experiment. Hypogseic . C 16 H 30 O 2 2 Grms. ioo-o Grms. Oleic, isooleic. 2 90-07 89-8-90-5 Hub! Elaidic . C 18 H 34 O 2 2 90-07 90-54 Saytzeff 2 Erucic . . . C 22 H 42 O 0 2 75-15 Brassidic . U 22 B 42 O 2 2 75-15 75-34 Saytzeff ' 3 Isoerucic . . C 22 H 42 O 2 2 75-15 74-42 f Alexandroff’ -{ and Ricinoleic . 2 85-24 ( Saytzeff 4 Linolic . C'lsUs'i'-L 4 181-43 Linolenic . . O 18 -U 30 O 2 6 274-10 The specimen of oleic acid yielding the number 89'8-90'5 was prepared from almond oil (private communication). This oil con¬ taining, according to Hazura’s later researches, less saturated fatty acids than oleic acid, the excellent agreement of theory and experi¬ ment is a fortuitous one, the less saturated fatty acid having been compensated, as it were, by saturated acids not completely eliminated from the specimen (cp. p. 196). It must, however, be pointed out that a specimen of oleic acid, prepared by Geitel (Jour. f. prakt. Chemie, 1888 [37], 59) from tallow by repeated crystallisation, gave the iodine value 89. The more recent determinations carried out by Saytzeff, and by Alexandroff and Saytzeff.\ on pure specimens of elaidic, brassidic, and isocrucic acids would also appear to speak in favour of an agreement 1 Berichte, 24. 4117. 3 Ibid. 1894 [50], 79. 2 Jour. f. prakt. Chemie, 1894 [50], 75. 4 Ibid. 1894 [49], 61. 176 CHEMICAL METHODS OF EXAMINING FATS AND WAXES CHAP. between theory and experiment. It is very desirable that this very important fact should be corroborated by further experiments. With a view to examine the basis on which Hull’s principle rests, the writer 1 has experimented with the following unsaturated sub¬ stances :— Substance. Iodine Value. Theory. Experiment. Allyl alcohol ...... 436-2 349-376 Undecylenic acid ..... 137-5 121-125 Croton ic acid. 300 25-25-9 Fumaric acid ...... 219 nil Maleic acid ...... 219 nil Cinnamic acid. 170-9 15-3-16-4 Styracin ....... 191-7 81-9-82-9 Cholesterol ...... 68-3 67-3-68-09 With the exception of cholesterol, none of the substances examined absorbed the amount of iodine required by theory. The saturated fatty acids, as has been shown by Hull , are not affected by his reagent. Gantter, however, having stated that lauric and stearic acids gave the iodine values of 4'3 and 6‘8 respectively, the writer 1 has examined a number of pure saturated fatty acids with the following negative result:— Acid. Iodine Value (100 grms. absorb grms. Iodine). Propionic .... 0-66 Butyric .... 0-36 Isobutyric.... o-oo Valeric .... 1-32 2 Caproic .... 0-30 CEnanthic .... o-oo Caprylic .... 0-55 Pelargonic 1-83 2 Capric .... 0-31 Lauric .... 1 "12 2 Palmitic .... 0-13 Stearic .... 0-20 Cerotic .... 1-34 2 The capricious results obtained by different observers can be ex¬ plained by the assumption that simultaneously with the addition of iodine substitution of iodine takes place in varying quantity accord¬ ing to the special conditions each worker adopted. The fact that some experimenters found very high iodine numbers when working 1 Unpublished observations. 2 The somewhat high values may be due to impurities. VI IODINE VALUE 177 with a very large excess of iodine, and allowing it to act for some considerable time 1 on an oil, would go far to prove this assumption, although the numbers given in the last table and on p. 175 would show that in those cases substitution is almost nil. Thus, in a similar fashion as shown above for bromine absorption (p. 169), con¬ currently with addition of iodine, substitution of hydrogen by iodine may be assumed to take place, so that the total iodine absorption would be due to loth addition and substitution. Recently several attempts have been made to elucidate the chemistry of the Hiibl iodine process. 2 Schweitzer and Lungwitz, 3 following the lines adopted by M c Ilhiney in the determination of the bromine absorption, differentiate between iodine addition and iodine substitution. The determination of the hydriodic acid, however, cannot be done by alkalimetric methods, and must therefore be carried out in a somewhat roundabout fashion, viz. by ascertaining the amount of iodine set free from a solution of potassium iodate, according to a reaction illustrated by the follow¬ ing equation :— 5HI + I0 3 H = 6I + 3H 2 0. Schweitzer and Lungwitz ascertain the iodine absorption exactly as in HubVs process, by titration with sodium thiosulphate. The titra¬ tion finished, they add 5 c.c. of a 2 per cent potassium iodate solution, and the iodine liberated thereby is measured by again titrating with sodium thiosulphate. The Hiibl solution used for the blank test is then treated in precisely the same manner, and thus the total iodine absorbed and the amount of iodine present as hydriodic acid are found. By multiplying the latter number by two the iodine substitution number is obtained. On subtracting this number from the total iodine absorption number the iodine addition number is found. Schweitzer and Lungwitz term the last value the “ correct ” iodine number, and in a later publication the “ true ” iodine number. Their experiments are, in the writer’s opinion, open to some objections; at any rate they do not solve the problem in a satisfactory manner, and would only appear to increase the confusion already existing. For in a further series of experiments the same observers 4 found that, whereas in both methyl alcoholic and ethyl alcoholic solutions, in presence of mercury bichloride, the total iodine absorptions were practically identical for a number of oils, the substitution numbers varied in a very capricious manner, thus leading to a double set of true iodine numbers (addition numbers). The so-called true iodine numbers were considerably higher in the case of the ethyl alcoholic solutions, or in other words, the substitution was considerably less than in methyl alcoholic solutions. When in a corresponding series of experiments the mercury bichloride was left out, it was found that in methyl alcoholic solutions substitution only of iodine ( i.e. 1 Cp. e.g. Williams, Analyst, 1895, 276. 2 Cp. Lewkowitsch, Jahrbuch der Chemie, 1896, 392. 3 Jour. Soc. Chem. Ind. 1895, 131. 4 Ibid. 1895, 1030. N 178 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chav. no addition) took place, whereas in ethyl alcoholic solutions chiefly substitution occurred, but simultaneously also addition to a very small extent. In chloroformic solutions iodine absorption took place in two directions, viz. by addition and substitution. True addition of iodine without concomitant substitution was only ob¬ served in the case of iodine solutions prepared with either carbon bisulphide or carbon tetrachloride to the exclusion of mercury bi¬ chloride. But as these experiments are identical with those made by Gantter, and condemned for the reason stated above, the true iodine values thus obtained have no practical value. The object Schweitzer and Lungwitz had in view was to find a method by which there would be obtained solely iodine addition values (without con¬ comitant substitution) corresponding to those indicated by theory. This was actually reached by employing a carbon bisulphide solution of iodine, and allowing this solution to act at temperatures varying from 50° to 80° C. under pressure, mercury bichloride having been added in solid form. But unfortunately crucial experiments with “ chemically pure ” oleic acid furnished higher numbers than theory would indicate, although no substitution was noticeable. The nature of the reactions taking place is therefore not explained by the fore¬ going experiments. A more successful solution of the problem has been reached by Ephraim’s 1 experiments. He observed that the Hiibl solution required a much larger amount of sodium thiosulphate after addition of potassium iodide than without it, and concluded therefrom that on mixing the components of the Hiibl solution there is formed at once a substance capable of liberating iodine from potassium iodide. The chemical change is assumed to take place according to the following equation 2 :— HgCl 2 + I 2 =HgClI + ICI with formation of iodine monochloride. This equation would corre¬ spond to HiibFs directions, that for 2 atoms of iodine at least 1 molecule of mercury bichloride must be used. A solution of iodine monochloride of the same strength as the Hiibl solution must contain 16‘25 grms. in 1000 c.c. A number of experiments carried out with iodine monochloride solution of the strength named on oleic acid, linseed oil, olive oil, poppy seed oil, sesame oil, arachis oil, castor oil, and almond oil in the same fashion as in HiibFs iodine test, furnished results identical with those obtained by Hiibl’s method. Ephraim concludes, therefore, that alcoholic solutions of iodine mono¬ chloride may be substituted for the Hiibl solution. In practice it would appear preferable to adhere to HiibFs direc¬ tion, since commercial iodine monochloride is rarely pure, this fact rendering it imperative to examine each sample of iodine mono¬ chloride, in order to ascertain the amount of IC1 it contains, by 1 Analyst, 1895, 254. 2 Ephraim states distinctly that this equation must not necessarily he considered as quantitatively expressing the chemical change. VI IODINE VALUE 179 titration with sodium thiosulphate, both without and with addition of potassium iodide, so as to determine the amount of iodine which the impurities in the commercial article are capable of liberating. Additional proof for the assumption that iodine moreochloride is present in the Hiibl solution is afforded by the fact that similar experiments with iodine trichloride on oleic acid gave altogether dis¬ cordant results. 1 A study of Hlibl’s process with a view to following up quantita¬ tively its chemical changes has been carried out by Waller . 2 It was found that the whole of the oil was in the chloroform solution, that the chloroform contained both iodine and chlorine, both halogens having been absorbed by the oil in fairly constant proportions, and that the whole of the mercury was in the upper alcoholic layer. During the standing of the solution free hydrochloric acid was formed (an observation also recorded by Schweitzer and Lungwitz), such hydro¬ chloric acid increasing in proportion to the excess of mercury bichloride. The following explanation of the course of reactions is given :— Part of the iodine is absorbed in the first instance, and the mercury bichloride is converted into mercury iodide and free chlorine. The latter forms with the water, contained in the alcohol, hydrochloric acid and free oxygen. The oxygen then combines with that portion of the oil which has not yet absorbed halogen. According to Waller’s view, the Hiibl iodine number would thus be the amount of iodine, chlorine, and oxygen absorbed, expressed in terms of iodine, and the true iodine number of an oil would be found by subtracting from the Hiibl number the amount of hydrochloric acid formed and calculated to iodine. Unfortunately Waller’s true iodine number differs very consider¬ ably from Schweitzer and Lungwitz’s true iodine number; for a sample of oleic acid, of the Hiibl number 93, had, according to Waller , the “ true ” iodine number 84, whereas Schweitzer and Lungwitz’s “ chemi¬ cally pure” oleic acid led to as high a number as 93-105. It will appear from the foregoing that a comprehensive explanation of the Hiibl process is still wanting. But this much is clearly estab¬ lished, that by following closely the directions laid down above for carrying out the iodine test practically constant results are obtained. The writer has proved this abundantly by a very large number of experiments on various fats and oils. If it were permissible to draw con¬ clusions from the last column of the table given above, it would appear that the results so obtained are in excellent agreement with theory. It is therefore most desirable that analysts (especially those who use the iodine test for the first time) should strictly adhere to the directions given above, at any rate until such time when the chemical reactions underlying Hiibl’s process will be fully understood. 1 This is confirmed by Seeliger (Pharm. Gentralhalle, 1894. 89) and Waller, Chemiker Zeitung, 1895, 1787). 2 Chemiker Zeitung , 1895, 1787, 1831. 180 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chai*. In order to eliminate slight errors due to the presence of free acids in fats, MorawsJci and Demski 1 determine the iodine value of the free fatty acids liberated from the fats by the method described above (p. 100). It should, however, be borne in mind that in this case the influence due to the presence of any soluble fatty acids is obliterated, and differences, caused by the varying proportions of soluble fatty acids in two fats, may thus be overlooked. Besides, during the operations entailed in liberating and drying the free acids, especially in the case of drying oils, oxidation may set in, resulting in a diminu¬ tion of the iodine value. Therefore it is evident that the iodine values of the fats may not be proportional to those of their fatty acids. It is, however, customary to estimate the absorption of both the fat and its fatty acids. In the determination of the absorption values of the free fatty acids the iodine solution is allowed to act directly on the fatty acids, solution in chloroform being unnecessary. It is evident that from the iodine value of a fat alone the per¬ centage of glycerides of the unsaturated fatty acids cannot be calculated. In the case, however, of a fat containing the glyceride of one unsaturated fatty acid only, the absolute amount of that glyceride can be determined. B. QUANTITATIVE DETERMINATION OF SOME CON¬ STITUENTS OF FATS AND WAXES When estimating fatty substances by gravimetric methods, due consideration should be given to the fact that on drying fats and fatty acids constant weights must not be expected. This is due to either a slight loss caused by volatilisation of volatile acids [either contained originally in the substance or formed at the higher temperature], or to an increase of weight owing to absorption of oxygen. It is quite possible, of course, that both volatilisation and consequent decrease of weight on the one hand, and oxidation and consequent increase of weight on the other hand, may occur simultaneously, these two sources of error to some extent counterbalancing one another (cp. also p. 160). Hence the drying should be done at the lowest possible temperature, at any rate not above 110° C., and should not be pushed beyond a point when fairly approximate results have been obtained, which, as a rule, will be reached within a few hours. Drying oils or their fatty acids are best dried in a current of hydrogen, carbon dioxide, or coal gas. A convenient form of apparatus for such purposes has been described above (p. 88, cp. also p. 674). The following table, due to Tatlock , 2 will give some indications as to the amount of error caused by drying fatty acids at 90° C. :— 1 Jour. Soc. Chem. Ind. 1886, 179. 2 Ibid. 1890, 374. Table showing Loss (or Gain) in Weight of Dry Fatty Acids , during different Periods , at 90° C. 182 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. The quantitative analysis of fats or waxes or of mixtures of several fats, provided foreign matters (as resin, paraffin wax, mineral oils, etc.), are absent, generally embraces the determination of one or more of the following constituents :— i. Free fatty acids and neutral fat; mean combining weight of the fatty acids. ii. Diglycerides. iii. Soluble (volatile) and insoluble (non-volatile) fatty acids. iv. Saturated and non-saturated fatty acids. v. Mixed palmitic, stearic, and oleic acids, other non-volatile fatty acids being absent. vi. Approximate determination of liquid fatty acids—oleic and linolic. vii. Hydroxy acids. viii. Lactones (inner anhydrides). ix. Glycerol. x. Higher aliphatic alcohols. i. Free Fatty Acids and Neutral Fat; Mean Molecular Weight of the Fatty Acids (a) Gravimetric Determination of the Proportion of Free Fatty Acids Weigh off accurately in a flask several grms. of the sample, add hot alcohol and phenolphthalein, and neutralise carefully the free fatty acids by allowing dilute alkali to run in until the solution just acquires a permanent pink colour. If the strength of the alkali solu¬ tion be known, the acid value of the fat will be found simultaneously. Allow the liquid to cool, dilute with an equal volume of water, and shake out in a separating funnel with petroleum ether. Draw off the aqueous layer, and wash the ether layer repeatedly with water, separating the wash-water as completely as possible from the petroleum ether. 1 (Remove the little water remaining by running the petroleum ether first into a dry flask, and next into the tared flask, or by filtering the petroleum layer through paper into the tared flask.) Extract the aqueous layer a second time with petroleum ether in the same way, and transfer the ether to the tared flask. Next distil off the petroleum ether, dry the residue, and weigh it. This will give the neutral fat. The amount of free fatty acids may be found either by difference, or direct by transferring the aqueous layer and the wash-water to a separating funnel, acidifying with dilute sulphuric acid, and extract¬ ing with petroleum ether as directed above. The weight of substance found corresponds to the amount of fatty acids. Laugier 2 and Hager 3 propose the following process for the deter¬ mination of free fatty acids in oils :— 1 Morawski and Demski, Jour. Soc. Chem. Ind. 1886, 179. 2 Zeitsch. f. analyt. Chemie, 20. 133. 3 Ibid. 17. 392 ; 19. 116 : 20. 134. VI GRAVIMETRIC DETERMINATION OF FREE FATTY ACIDS 183 Triturate 10 grms. of the oil under examination in a mortar with 5 grms. of sodium carbonate, add 5 grms. of water, and warm on the water-bath for one hour, occasionally stirring the mass. Then admix with it a sufficient quantity of coarsely-powdered pumice-stone so as to obtain a crumbling mass, dry on the water-bath, powder, and extract with ether free from alcohol. Evaporate the ether, and weigh the remaining neutral fat. In the case of a crude oil the proportion of fatty acids cannot be found by difference, such oils containing, as a rule, several per cents of foreign substances (colouring matters, mucilaginous or resinous bodies) which are not extracted by ether. The mass left after exhaustion with ether must, therefore, be extracted with alcohol. The alcoholic solution is then evaporated to dryness, the remaining soap decomposed by sulphuric acid, and the liberated fatty acids mixed with a known quantity of paraffin wax, and weighed. Any difference from 100 will correspond to the proportion of non¬ fatty substances in the sample. Considering the slight solubility of soap in ether and the possibility of foreign substances passing into the alcoholic solution, it is evident that this method cannot claim great accuracy. Sear 1 recommends the following method :— Dissolve 5 grms. of the fat in 100-150 c.c. of carbon bisulphide in the cold in a flask provided with a well-fitting cork, add 2‘5 grms. of finely divided zinc oxide, and allow to stand for three or four hours with occasional agitation. At the expiration of this time the contents of the flask are thrown upon a filter, the filtrate being collected in a tared flask, thoroughly washed with carbon bisulphide, and the filtrate distilled as low as possible on the water-bath, dried, and weighed. The residue, which consists of neutral fat and zinc oleate, is saponified with alcoholic potash, the soap decomposed with a mineral acid, the aqueous portion separated from the fatty acids, and the zinc precipitated from a hot solution by means of potassium carbonate. The zinc carbonate is then collected on a filter, weighed as zinc oxide, and calculated to the corresponding quantity of zinc oleate. Subtracting this from the weight of the mixture of neutral fat and zinc oleate, the weight of the former is obtained. The amount of oleic acid is calculated from the zinc oleate. The quantity of free solid fatty acids is obtained by adding together the weights of the neutral fat and oleic acid, and subtracting from the weight of the oil taken. (b) Volumetric Determination of the Proportion of Free Fatty Acids 2 The percentage F of free fatty acids in a fat or wax can be calculated from its acid value A (determined as described above, p. 148) if the mean molecular weight of the free fatty acids, M, be known. M grms. require, of course, 56100 milligrms. KOH, whilst 1 Ohem. News, 44. 299. 2 Hausamann, Dingler’s Polyt. Jour. 240. 62 ; Grciger, ibid. 244. 303 ; Yssel de Schepper and Geitel, ibid. 245. 295. 184 CHEMICAL METHODS OF EXAMINING FATS AND AVAXES chap. F grms. corresponding to 100 grms. of fat are saturated by 100 x A milligrms. KOH. We have therefore M : 56100 —F : 100 A, hence 100AM AM 56100 561 . This method, however, is only applicable in the case of the fat containing no soluble fatty acids, or, at any rate, only an insignificant amount. In order to determine the mean molecular weight M, the fatty acids must be first separated from the neutral fat by the method given in the beginning of the preceding paragraph (p. 182), or Gruger’s process may be adopted. The latter is carried out as follows :— 4 to 8 grms. of the sample are placed in a flask of about 300 c.c. capacity, and dissolved in 50 c.c. of neutralised alcohol by raising it to the boiling point. A few drops of phenolphthalein having been added, the solution is titrated with standard alkali until, after thorough agitation, the pink colouration is permanent. The solution is then diluted with 150 c.c. of water, when the neutral fat will separate out nearly completely, whilst the potash soap remains dissolved. Next 60-100 c.c. of ether are added and the contents of the flask shaken thoroughly. After settling out, the greatest part of the clear soap solution is drawn off by means of a pipette, care being taken that none of the ethereal layer is withdrawn at the same time, then diluted strongly with water, and boiled until the dissolved ether and alcohol are driven off completely. By adding dilute sulphuric acid the fatty acids are liberated ; they are washed with boiling water, which is removed by means of a syphon, until the wash-water shows no longer acid reaction. The acids are then allowed to cool. If they solidify the cake is removed regardless of the small quantity adhering to the sides of the vessel; if, however, they remain fluid at the ordinary temperature a pipette must be used. The acids are then weighed accurately, dissolved in alcohol, and titrated with standard potash ; from the quantity of the alkali used their saponification value K is calculated, i.e. the number of milligrms. KOH required for 1 grm. of fatty acid. Since M grms. of fatty acids require 56100 milligrms. of KOFI, we have the proportion hence 1 :K = M : 56100, M = 56100 . By substituting this value for M in equation (1) we obtain A . 56100 _ A. 100 561. K ~ K ( 2 ). (3). It is evident that it is not necessary to calculate the acid value A of the fat and the saponification value K of the free fatty acids, the A ratio only being required. It will suffice, therefore, to substitute VI VOLUMETRIC DETERMINATION OF FREE FATTY ACIDS 185 for A and K the numbers of c.c. required for 1 grm. of fat and 1 grm. of fatty acids respectively. In that case the titer of the alkali need not even be known. Thus if a and b represent the numbers of c.c. used for the two determinations, we find— If the sample of fat may be considered as completely free from foreign substances, the proportion of neutral fat N may be found by difference ; we have thus N = 100 - F=100 - 100 x a b (5). Compared with the gravimetric process described above this volu¬ metric method hardly offers any advantage, requiring, as it does, the isolation of the free fatty acids. Although the latter need not be re¬ covered quantitatively in this case, still, the drying and weighing of part thereof is requisite. The determination of F, however, is much simplified by assuming that the free acids possess the same mean molecular weight as those combined with glycerol to form the neutral fat. Such an assumption may be permissible for most rancid fats; indeed, Thum 1 has proved by experiment that it holds good for palm and olive oils. This assumption granted, the percentage of free fatty acids and neutral fat in a fat may be found by one of the following three methods. At the same time the probable yield of fatty acids and glycerol from a fat may be readily calculated. 1. Determine the acid value A. Next separate the total fatty acids from 50 grms. of the sample (see p. 100), and titrate 2 to 5 grms. in alcoholic solution with standard alkali, thus finding the saponifica¬ tion value K of the total fatty acids. The mean molecular weight of the total fatty acids M, the per¬ centage of free fatty acids F, and the proportion of neutral fat N, are then calculated according to equations (2) (3) (4) and (5). Let r be the quantity of glycerol, and d> the quantity of fatty acids obtainable from 1 part of neutral fat, then is evidently one- hundredth part of H, the Hehner value of the neutral fat, or d> = The general equation expressing the saponification of fats is— C 3 H 5 0 3 . R 3 + 3H 2 0 = 3R. OH + C 3 H 8 0 3 , Neutral fat. Fatty acids. Glycerol. R standing for the radicle of any fatty acid. Writing for a moment the formula of the neutral fat, C 3 H 2 (R. OH) 3 , the last equation will read thus— C 3 H 2 . (R. 0H) 3 + 3H 2 0 = 3R. 0H + C 3 H 8 0 3 . 1 Jour. Soc. Chem. Ind. 1891, 70. 186 CHEMICAL METHODS OF EXAMINING FATS AND WAXES CHAP. If M be, as before, the molecular weight of the fatty acids, the molecular weight of the neutral fat will be 3M + 38; (C 3 H 2 =38). Therefore, (3M +38) parts of fat yield 3M parts of fatty acids and 92 parts of glycerol (C 3 H g 0 3 = 92); or 1 part of neutral fat yields H _ 3M 92 ~100~3M + 38’ A ~3M + 38 (6). N per cent of neutral fat yields therefore, on saponification, the following quantities of fatty acids F x and glycerol G in per cents— Fi = N = N. 3M . 1 3M + 38 • • (7). G = Nr = N . 92 . 3M + 38 • • ( 8 ). Equation 8 expresses at the same time the total yield of glycerol obtain¬ able from a fat. The total yield of fatty acids, however, is made up from two com¬ ponents, viz. F, the percentage of free fatty acids, and F x , the per¬ centage of fatty acids obtainable from the neutral fat. If the total yield of fatty acids be Q, we have Q = F + Fj.(9). It is evident that Q is identical with the Helmer value of the sample which can, of course, be found in a direct way. G will be more accurately determined by means of the ether value of the fat (see below, p. 154). The subjoined table, due to De Schepper and Geitel, contains the molecular weights of a few fatty acids and of their triglycerides, and the quantities of fatty acids and glycerol obtainable from 100 parts of these glycerides. The last column contains the number of one-tenth c.c. of a standard solution of KOH, 10 c.c. of which correspond to 1 grm. C l7 H 34 0 2 2 , required to saturate 1 grm. of fatty acid. Fatty Acid. Formula. Molecular Weight of Fatty [ Triglyce- Acid. ride. Trigl Fatty Acids. yceride ilds Glycerol. A c.c. of KOH (10 e.c. = l grm. C17H34O2). Stearic acid Oleic acid (Margaric acid 1 . Palmitic acid . Myristic acid . Laurie acid . Capric acid . Caproic acid . . Butyric acid c 18 h 36 0 2 018H 34 0 2 Ci 7 H 34 0 2 OigH 32 0 2 Q14H28O2 C 12 H 24 O 2 OioH 20 0 2 C 6 h 12 o 2 C 4 h 8 0 2 284 282 270 256 228 200 172 116 88 890 884 848 806 722 638 594 386 302 95-73 95-70 95-52 95-28 94-47 94-04 93-14 90-16 87-41 10-337 10-408 10- 850 11- 415 12- 742 14- 420 15- 480 23-830 30-464 95-07 95-74 100 - 00 ) 105-47 114-03 135-00 156-99 232-7 306-8 Chap. iii. p. 47. VI FREE FATTY ACIDS, NEUTRAL FAT, GLYCEROL 187 2. Determine A, the acid value, and K, the saponification value, of the fat. The percentage of free fatty acids, neutral fat, and the yield of glycerol G and total fatty acids Q, can be calculated in the following way :— The amount of glycerol is proportional to the quantity of KOH found in determining the ether value E, E being = K - A (see p. 154), n , 100 E E . .. \ , or Ur corresponds to ■ — grms. = — grms. According to the equation C 3 H 5 (OR) 3 + 3KOH = C 3 H 8 0 3 + 3R. OK, Neutral fat. Glycerol. Soap. 92 parts of glycerol correspond to 3 x 56T parts of KOH. Hence the proportion and 92 E ( 10 ). =0-05466 E 10x3x56-1 The yield of total fatty acids Q in per cent is therefore Q=ioo-|g ■(92 parts of glycerol being proportional to 38 parts of C 3 H 2 ); or sub¬ stituting the value for G found in (10)— • (ll). = 100-0-02258 E 38E 1000 milligrms. of fat contain, therefore, 1000 - -—=== milligrms. O X 0 o 1 of total fatty acids, requiring for their neutralisation K milligrms. of KOH. AVe have, therefore, for the calculation of their mean molecular weight the proportion— 1000 -8l^i !K = M!B8,1 ’ wherefrom 168300-38E 3K ( 12 ). M K According to equation (1) we have F = —; substituting for M the value found in (12), we obtain for the percentage of free fatty acids— A(168300 -38E) (168300 - 38E) A 561 x3K - 1683K 1683K (13). 188 CHEMICAL METHODS OF EXAMINING FATS AND WAXES CHAP. 3. If the composition of a neutral fat in a mixture of the neutral fat with its free fatty acids be known, the weighing off of the sub¬ stance may be dispensed with by adopting Groger’s method. Supposing it be required to know how far the resolution of tallow into fatty acids and glycerol has proceeded in a technical process for the saponification of fat. Let us assume that the yield of total fatty- acids from neutral tallow has been found to be 95‘6 per cent (by Hehner’s method, or by the method described under 1). A quantity of the sample about 6 to 10 grms., which need not be weighed off accurately, is titrated with alkali, the titer of which need not be known. If a and b be the numbers of c.c. required for the neutralisation of the free fatty acids on the one hand, and for the complete saponification on the other, it is evident that a- 100. ft :F=—- b-.a. 9o b According to a well-known rule we have Since , T ,, , „ 100 7 100 , M+F =9lFeW + »- N + F=100; and ^=1-046, 95*6 we have after substitution hence N: 100 = 1 '046 b : 1 '046 5 + a, ,, 104 -6 b — 1’046 b + a ' (14). (c) Mean Molecular Weight of the Fatty Adds, In the preceding paragraph two methods for the determination of the mean molecular weight have been described ; in order to put them more clearly before the reader they may be repeated here briefly. 1. Saponify 50 grms. of the fat, dry the fatty acids, as directed (p. 182), and determine the saponification value K x of the fatty acids. The mean molecular weight is then found by the following equation M = 56100 It should be understood that M represents the mean molecular weight of the insoluble, non-volatile fatty acids only, the soluble acids having been washed away in the course of preparation. 2. Determine the saponification value K and the ether value E of the fat. According to equation (12) we have then 168300-380 E 3K VI MEAN MOLECULAR WEIGHT OF FATTY ACIDS 189 Provided a fat contains no foreign substances, nor any glycerides of the soluble acids, the mean molecular weight of the fatty acids can be calculated from the Hehner value, if the fat does not contain a considerable amount of free fatty acids. That assumption, however, rarely obtains in practice. The mean molecular weight may then be calculated from equation < 6 ) : H _ 3M 100 — 3M + 38’ hence 38H 38H (15). 300-3H 3(100-H) ' Thus from H = 95'6 for neutral tallow we should find the mean molecular weight of the tallow acids M = 275, which is in close agreement with their molecular weight as determined by titration. If M be the mean molecular weight of the total fatty acids, and M 1 the mean molecular weight of the insoluble acids; further, if H, the percentage of insoluble fatty acids, and S, the percentage of the soluble fatty acids (see p. 191), be known, the mean molecular weight of the soluble fatty acids , M„ can be calculated from the following equa¬ tion, in which Q represents, as before, the percentage of the total fatty acids, as expressed by equation (11):— Q__S_ + H M M 2 MT hence SMMj 2 QMi-HM (16). Another method of finding the mean molecular weight of the volatile or soluble acids is given by the Beichert-Meissl value of a fat, as determined by Morse and Burton’s process (see p. 631). Let k be the number of milligrms. KOH required for neutralisation of the volatile acids from one grm. of fat, or of — ^ grms. of volatile acids (S being the percentage of soluble fatty acids), then we have hence (17). Thus, if for a butter fat the Beichert-Meissl value be 32 ( i.e . for 5 grms.), and S = 7‘44 per cent, k will equal 32 x 5-61 5 ; and therefore 561S x 5 S x 500 7'44x500 3720 - 32 - = 116 - 2 - 32 190 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. ii. Diglycerides The occurrence of diglycerides in a fat has hitherto been proved in the solitary case of “ rape oil stearine ” in which dierucin has been found (see p. 2). A fat may be tested for diglycerides by boiling an accurately weighed quantity with acetic anhydride, and washing the resulting product with boiling water until it is free from acid. If diglycerides be present an increase of weight will be found. 1 This is due to one acetyl group having been taken up by one molecule of the diglyceride with the formation of a triglyceride, as shown by the equation C * H °OR) s + O!H » O ' OH = 0 » H °6E)f 30 - If the quantitative estimation be carried out with due care, in the case of a pure diglyceride its molecular weight may be calculated from the increase in weight. Thus if a grms. of a pure diglyceride have been weighed off, and an increase of weight, i, has been found, it is evident that we have the proportion a :a + i =M : M + 42, where M is the molecular weight of the diglyceride, and consequently M + 42 the molecular weight of the triglyceride obtained on assimila¬ tion of the group C 2 H 2 0( = 42). The above proportion is expressed by the equation a(M + 42) = M(& + i), hence (18). As a rule, however, the diglyceride will only form a small proportion of the fat under examination. If the chemical composition of the diglyceride be known, the absolute quantity of the diglyceride a in the fat may be calculated with the help of the same equation (18) Mi Thus if a grms. of a fat, containing a diglyceride of the known molecu¬ lar weight M, have been weighed off, and the increase i obtained on acetylating, the percentage of the diglyceride in the fat will be found from the proportion a : 100 : x> hence lOOMi 42a (19). The proportion of diglycerides can also be found volumetrically if the molecular weight of the diglyceride be known. 2 If M be the molecular weight of the diglyceride, K the saponification value of the sample under examination, and C the saponification value of the 1 Lewkowitsch, Jour. Soc. Chem. Ind. 1892, 138. 2 Benedikt, Jour. Soc. Chem. Ind. 1888, 696. VI DIGLYCERIDES 191 acetylated product, then the percentage D of the diglyceride may be calculated from the following formula (56 T being the molecular weight of KOH and 42 that of C 2 H 2 0): D = 100M(C - K) 5610 - 42 C I prefer to use the formula D: 100(C - K)M. (M + 42) ( 20 ). ( 21 ). 56'1(M - 84) which is arrived at as follows : M grms. of a diglyceride require 2 x 56*1 grms. of KOH for saponification; M + 42 grms. of the triglyceride, obtained from it on digestion with acetic anhydride, require 3 x 56‘1 grms. KOH. Therefore 1 grm. of the diglyceride . 2 x 561 requires —, The difference and 1 grm. of the triglyceride 3 x 56T M + 42 3x56 -1 M + 42 2x56'l_56(M M 2x42) M(M + 42) must, for a sample consisting of a pure diglyceride, be equal to C - K, hence 100(C-K)M.(M + 42) 56'1(M- 2 x 42) ' Thus if the proportion of di-erucin - C 3 H 5 ^^|^ 22 ^ 41 ^ 2 (M = 732) in rape oil stearine has to be determined, and K be found = 46'0 for this rape oil stearine, and for the acetylated rape oil stearine C = 67'8, we have, since C - K = 21-8, 100 x21-8 x732 x 774 56-1 x (732-84) ~ 34 ‘ The correctness of this calculation may be proved as follows :— The saponification value of pure di-erucin C 3 H-(0C 22 H 41 0) 9 (0H) is 153-3, that of acetylated di-erucin C 3 H 5 (0C 2 H 3 0)(dC 22 H 41 0) 2 is 217‘4. The difference 217 4 - 153*3 = 64*1 ; found C - K = 21-8 ; therefore If a fat contains, besides diglycerides, glycerides of hydroxylated fatty acids, the calculation becomes more complicated, since the latter, on digesting with acetic anhydride, also assimilate the acetyl group. In such cases it is necessary to prepare the free fatty acids from 50 grms. of the fat, and to determine their acetyl value. iii. Soluble (Volatile) and Insoluble (Non-Volatile) Aeids The proportion of the insoluble or non-volatile fatty acids is indicated by the Helmer value H. 192 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. The proportion of the total fatty acids, as found by the ether value E, is according to equation (11)— 0 = 100-0-02258 E, consequently the percentage of soluble (volatile) acids S is S = Q-H = 100-0'02258 E-H . . . (22). Thus, if for a butter fat the Hehner value has been found = 87‘5, the saponification value = 227, and the acid value = 3, we have, since E = 224 S = 100 - (0'02258 x 224)87 "5 = 7 "44 per cent. iv. Saturated and Non-Saturated Fatty Acids—Proportion of Liquid and Solid Acids in the Insoluble Fatty Acids Before attacking the quantitative estimation of the proportion of liquid and solid acids in the mixed insoluble fatty acids, it will be found useful to examine the mixture qualitatively for presence of any liquid or solid acids. The former are best discovered by applying Hiibl’s test, i.e. by determining the iodine value of all the insoluble acids. If no iodine absorption be found, it is safe to conclude that unsaturated acids are absent. If, on the contrary, a definite value has been obtained, separation of the acids by means of then- lead salts (see below) must be resorted to, since some fats may contain solid unsaturated fatty acids, as isooleic acid and erucic acid, the lead salts of which are either insoluble or sparingly soluble in cold ether. For the qualitative detection of solid fatty acids (stearic, palmitic) in a liquid fat, Allen saponifies with alcoholic potash, and neutral¬ ises accurately the excess of alkali with acetic acid, using phenol- phthalein as indicator. After filtering off, the filtrate is mixed with two volumes of ether, and alcoholic solution of lead acetate is added. A white precipitate will indicate presence of solid fatty acids. A method for the separation of the solid from the liquid acids was proposed first by Varrentrapp. It is based on the solubility of the lead salts of the liquid fatty acids (oleic, linolic, and their homo- logues) in ether, the lead salts of the solid fatty acids (stearic, palmitic, etc.) being insoluble in that menstruum. This process does not yield ver}>- accurate results, inasmuch as small quantities of the solid acids pass into the ethereal solution, as was shown first by Mulder, 1 whilst lead salts of the drying fatty acid remain partly undissolved. Lewkowitsch 2 has also shown that in the absence of drying fatty acids a complete separation of the liquid from the solid acids is impossible. Therefore the separation by means of the lead salts is not a quantitative method, but can only be looked upon as a fractional separation. A 1 Mulder, Chemie der ciustrocknenden Oele, 1867, p. 44 (German translation). 2 Jour. Soc. Chen. Ind. 1890, 845. VI DETERMINATION OF LIQUID FATTY ACIDS 193 glance at the solubilities of the lead salts of the saturated acids in ether given in the following table will corroborate this conclusion :— Lead Salt of 100 c.c. of Ether dissolve Observer. Palmitic Acid. 0-0184 Lidoff 1 Stearic Acid. 0-0148 Mixed Stearic and Palmitic Acids (Iodine value = 0) 0-0150 (at 25° C.) Twitchell 2 Varrentrapp’s reaction has been used in several forms, the more important of which are detailed below. 1. Oudemans’ Process . 3 —Prepare from the sample of fat under examination the fatty acids in the usual manner, add an excess of sodium carbonate, and evaporate on the water-bath to complete dryness. Digest the dry residue with absolute alcohol, and filter the solution through a jacketed funnel. Exhaust the insoluble part by repeated boiling out and washing with absolute alcohol until the sodium soap has been brought completely into solution, dilute the latter with a little water, and add an excess of lead acetate solution. Then thoroughly wash the precipitated lead salts, and dry them first by exposure to air and then by allowing to stand under a desiccator. Next digest an accurately weighed quantity of the lead salts with dry ether in a well-stoppered flask, filter the ethereal solution, and exhaust repeatedly the undissolved mass with fresh quantities of ether ; then distil off the ether. Dry the residue at a gentle heat and weigh. If there is reason to suppose that oleic acid only is present, the dried residue may be considered as lead oleate. If, however, the nature of the liquid acids be unknown, a determination of lead must be made as in the following process. 2. KremeVs Modification . 4 —By this process the object of Oudemans „ viz. to obtain the acids in the form of completely neutral soaps, is attained in the following more expeditious way :— Weigh off accurately 2 to 3 grms. of the sample of fat in a wide¬ mouthed flask of about 100 to 150 c.c. capacity, and saponify on the water-bath with about the same quantity of caustic potash and 10 c.c.. of 95 per cent alcohol. Then add a little water and a few drops of a. phenolphthalein solution, and neutralise accurately with acetic acid. Evaporate off the alcohol on the water-bath, dissolve the soap in 80 c.c. of hot water, and precipitate with lead acetate. The lead soaps will be found, on gentle agitation, to adhere completely to the sides of the flask. Cool completely, pour the liquid through a filter, and wash several times with boiling water. Then melt the lead salts by warming on the water-bath, allow to cool, drain any liquid through, the filter, and dry the contents of the flask, as also the filter, at a gentle heat. Next digest the lead salts with ether, and filter the 1 Berichte, 26, Ref. 97. 2 Jour. Soc. Chem. Jnd. 1895, 515. 3 Jour. f. prakt. Chem. 99. 407. 4 Pharm. Centralhalle, 5. 337. O 194 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. ethereal solution through the same filter into a tared porcelain basin, keeping the filter well covered. After thorough exhaustion with ether, evaporate the filtrate, dry the residue first at a gentle heat on the water-bath, then in a desiccator over sulphuric acid, and weigh. Determine the quantity of lead oxide in an aliquot part of the residue, and subtract the total amount of lead oxide from the weight of the lead salts. The difference thus obtained will indicate the amount of anhydrides of the liquid fatty acids. By adding to this amount the quantity of water corresponding to the weight B of lead oxide found —multiplying B by-^ 0‘0807 — the weight of the liquid acids themselves will be obtained. The lead salts of the solid fatty acids, dried on the filter by allowing the ether to evaporate, are put back into the flask and decomposed by boiling with dilute hydrochloric acid. The separated fatty acids are then dissolved in ether, and their weight determined after evaporating off the ether. 3. Bose’s Modification}—Rose rejects the two preceding processes on account of their tediousness and liability to error caused by oxida¬ tion, especially of the fatty acids of the linolic series, and the formation of basic lead salts during treatment with boiling ether, the basic lead salts of the liquid fatty acids being insoluble in ether. He recommends the following modification :— Prepare the fatty acids from the sample of fat, and place 1 grm. in a 100 c.c. flask, with 0‘5 grm. of lead oxide and about 80 c.c. of dry ether. Allow to stand in a cool place for twenty-four to forty- eight hours, with occasional shaking. Then make up to exactly 100 c.c. with dry ether, shake thoroughly, and allow to settle. Take out 50 c.c. and filter through a small filter into a tared flask, keeping the filter as full as possible. Evaporate the ether, dry the residue in a current of carbonic dioxide, and weigh. After weighing, determine the lead by digesting on the water-bath with 5 c.c. of dilute sulphuric acid (1 : 5), diluting with 80 c.c. of 95 per cent alcohol, and weigh¬ ing the precipitated lead sulphate on a tared filter after drying at 100° C. Test experiments carried out by the author of this method with pure oleic acid gave very accurate results. According to Twitchell 1 2 petroleum ether completely volatile at 80 J C. should be substituted for ether, the former dissolving less of the stearates and palmitates than ether; but even then Rose’s method would only be applicable when the original fat is perfectly fresh and precautions are taken to avoid oxidation during all the manipulations. 4. Muter and de Koningh’s Modification . 3 —In this process the weighing of the lead salts and the determination of the lead is dis¬ pensed with. They proceed as follows :— 3 grms. of the sample of fat are saponified with 50 c.c. of alcohol and a few lumps of stick potash. Phenolphthalein is then added, and 1 Jour. Soc. Chem. Ind. 1887, 306. 2 Ibid. 1895, 515. 3 The Analyst, 1889, 61. Cp. also Lane, Jour. American Chemical Soc. Feb. 1893; Wallenstein and Finck, Jour. Soc. Chem. Ind. 1895, 79. VI DETERMINATION OF LIQUID FATTY ACIDS 195 the solution slightly acidified with acetic acid, and finally titrated with alcoholic potash until neutral. Next 30 c.c. of a 10 per cent lead acetate solution are boiled in a beaker with 200 c.c. of water, and the neutralised solution gradually run into it 1 with constant stirring. After rapidly cooling, the clear supernatant liquid is drawn oflf and the precipitate washed thoroughly with boiling water. The lead salts are then transferred to a flask containing 80 c.c. of ether, the beaker being washed out with small quantities of ether until the united ethereal liquids make up a volume of 120 c.c. The flask is then stoppered and shaken repeatedly during the next twelve hours, when all the lead salts of the liquid acids will have dissolved. The solution is then filtered into a Muter tube (Fig. 39) of 250 c.c. capacity, and the precipitate washed with ether until the filtrate is free from lead; 120 c.c. of ether will be found quite sufficient for the complete washing. The ethereal solution is made up with a mixture of one part of hydrochloric acid and four parts of water to 250 c.c., and shaken until the lead soaps are decomposed com¬ pletely, which is indicated by the ethereal layer be¬ coming clear. The acid liquid is then drawn off, and the ether layer washed with fresh quantities of water until the wash-water is free from acid. The volume of the ether layer is made up to 200 c.c., and 50 c.c. of it run into a small Erlenmeyer flask, and the ether partly evaporated. It is not advisable to evaporate the ether completely, since oxidation of the fatty acids may take place. 2 The residue is mixed with 50 c.c. Pig. 39 . of alcohol, and titrated with decinormal alkali. The alkali used is calculated to oleic acid, 1 c.c. of decinormal alkali equalling 0'0282 grm. C 18 H 34 0 2 . The error caused by presence of linolic and linolenic acids (mol. weight 280 and 278) is so slight that it may be neglected. If the ether be driven off in a current of dry carbonic dioxide or hydrogen, the absolute quantity of liquid fatty acids can be determined. Another quantity of the ethereal solution contained in the Muter tube may be used for the determination of the iodine value in the usual way, after the ether has been evaporated off in a current of car¬ bonic acid. For this iodine value Wallenstein and Finch propose the term “ inner ” or “ absolute ” iodine number of the fat (cp. chap. ix. p. 312). ’ For fats, or fatty acids containing but small quantities of solid acids, Allen’s method, as above described (p. 192), may be used, viz. 1 The writer finds it more convenient to run the lead solution into the soap solution contained in a flask, in which the extraction with ether takes place forthwith. 2 Although Muter in his experiments on the liquid fatty acids of lard—yielding 94 as their iodine number—did not use the precaution of entirely excluding access of air, TwitcheU ’s objection to Muter s method is not conclusive, as the difference between American and European lards (see p. 573) must not be lost sight of. 196 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. collect the precipitate, decompose with hydrochloric acid, and weigh the liberated fatty acids. If a separation of the free fatty acids from the neutral fat has been effected by one of the processes described above, the proportion of solid and liquid fatty acid in both the free acids and the neutral fat may be determined as detailed in this paragraph. For fats containing but small quantities of free fatty acids, as butter fat, Bondzynski and Rufi 1 use the following process :— 10-20 grms. of fat are dissolved in ether, mixed with dry calcium hydrate (slaked lime), and allowed to stand for twenty-four to forty- eight hours with occasional shaking. The precipitate containing excess of lime, and calcium stearate and palmitate is filtered off and washed with ether, the neutral fat and calcium oleate passing into the filtrate. The precipitate is then decomposed by sulphuric acid, and the pre¬ cipitated gypsum, together with the liberated solid fatty acids, extracted in a Soxhlet tube with ether, when the amount of the latter can be determined in the usual way. The ethereal filtrate is evaporated in a platinum dish and the residue burnt; the ash remaining is weighed as CaO, and calculated to calcium oleate (a better plan would be to shake the ethereal solution with dilute hydrochloric acid, and determine the calcium in the acid liquid by precipitation with ammonium oxalate). On adding the quantities of solid fatty acids found by direct weighing and that of oleic acid, calculated from the CaO, the total amount of free fatty acids in the fat will be obtained. This figure can be checked by titrating the solid fatty acids with decinormal alkali, and expressing the quantity of CaO found in terms of decinormal alkali. The sum of the c.c. used must correspond to the number of c.c. of decinormal alkali obtained on titrating the original fat after washing it with water. v. Mixed Palmitic, Stearic, and Oleic Acids, other Non-Volatile Fatty Acids being absent The methods described under this head 2 have been proposed in the first instance for the practical requirements of the candle- maker. It should, however, be borne in mind that “ distilled stearine” (distilled stearic acid) contains considerable quantities of the solid isooleic acid, which absorbs, of course, the same quantity of iodine as ordinary oleic acid. Therefore, in the formulae given below, 0 represents the sum of the two isomeric oleic acids. In order to determine the proportion of ordinary oleic acid alone, the lead-salt-ether method has to be resorted to, lead isooleate being but sparingly soluble in cold ether. It has been pointed out above (p. 192) that the lead-salt-ether method does not yield absolutely reliable results. Hehner, z judging from a series of experiments on almond oil, cotton seed oil, cocoa nut 1 Zeitsch. f. analyt. Chemie, 1890, 1. 2 Chevreul’s method referred to (p. 34) is only of historical interest. a Analyst, 17. 181. VI DETERMINATION OF OLEIC ACID 197 oil, and margarine, condemns this -method as utterly untrustworthy, the solid acids having been found to give definite iodine values (cp. Lewkowitsch, Jour. Soc. Chem. Ind. 1890, 845). Be Koningh, 1 on the other hand, tries to vindicate this process by proposing to decompose the insoluble lead salts with hydrochloric acid, and to re-crystallise the fatty acids so obtained from hot alcohol. Lewkowitsch (l.c .) has employed this method before. Lidoff 2 recommends the lead-salt-ether method (employing absolute ether), but makes a correction for the dissolved lead palmitate and stearate in accordance with the numbers given in the table (p. 193). This correction may meet the first of TwitcheU’s s objections to the lead-salt-ether method; whilst his second objection, viz. that the lead soaps of the unsaturated acids are oxidised even more rapidly than the free acids on exposure to air, does not apply with full force to oleic acid, especially if due precautions (see p. 195) are observed. (a) Determination of Oleic Acid If a fat contains no insoluble fatty acids other than stearic, palmitic, and oleic acids, the proportion of oleic acid can be deter¬ mined from the iodine value of the fat, according to Hubl, or from that of its fatty acids, as proposed by L. Mayer. Theory requires for oleic acid the iodine value 90-07, with which experiments agree (p. 175). The theoretical iodine value for olein is therefore 86 ‘20. Now, if the iodine value of a fat be found = J, the proportion of olein, 0, in per cents, will be o*; or o=i-i6oi j OD ' Z and the percentage of oleic acid, E, obtainable from the fat E = ^ ; or E = 1-1102 J. If J' be the iodine value of the fatty acids, the proportion of oleic acid, E', thereof will be E' = l-ll02 J'. David 4 has proposed for the determination of oleic acid a method based on the fact that the solid acids (stearic and palmitic) are less soluble in a mixture of alcohol and acetic acid than oleic acid. It is very unlikely that such a process will give accurate results. The mixture employed for the separation is prepared in the follow¬ ing way :—Dissolve in a measuring cylinder, indicating tenths of c.c., 1 c.c. of pure oleic acid in 3 c.c. of 95 per cent alcohol, and add drop by drop a mixture consisting of equal parts of glacial acetic acid and water as long as no turbidity appears. It will be found that at 15° C., 2‘2 c.c. of the acetic acid having been added, the further addition of 0*1 c.c. will render this liquid turbid, and all the oleic acid—1 c.c.—will 1 Chem. News, 65. 259." 2 Berichte, 26, Ref. 97. 3 Jour. Soc. Chem. Ind. 1895, 515. 4 Jour. Chem. Soc. 34. 1011. 198 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. eventually float on the top. Shotild this reaction (the proportions stated being used) not take place, the proportions must be varied until the separation is obtained as described. An alcoholic solution of stearic acid behaves totally different, turbidity setting in immediately after the addition of the first drop of acetic acid. Now prepare a mixture of alcohol and acetic acid in the pro¬ portions ascertained (say, 300 c.c. of alcohol and 220 c.c. of acetic acid), introduce 1 or 2 grms. of finely divided stearic acid, and keep the solution in a washing bottle, the delivery tube of which is closed at the bottom by a small sponge in order to retain any undissolved stearic acid. For actual analysis introduce the weighed and finely divided fatty acids (free from neutral fat) into a well-stoppered bottle, add 16 c.c. of the alcohol-acetic-acid mixture per grm. of substance, and allow to stand for twenty-four hours at a temperature of 15° C. with occasional agitation. Then filter, keeping the funnel well covered, and wash the residue on the filter first with the mixture, and afterwards with cold water. Wash the solid acid on the filter into a tared porcelain dish, and heat on the water-bath until the melted acid floats on the top. Allow to cool, pour off the water, dry at 100° C., and weigh. The fatty acid in the filtrate may be separated by neutralising with alkali, evapo¬ rating the alcohol, and liberating the oleic acid with hydrochloric acid. Tallow contains, as a rule, 95 per cent of fatty acids. If, there¬ fore, 0" 9 5 grm. of the fatty acids of a sample of tallow be weighed off, the quantity of solid acids obtained on weighing the residue, multiplied by 100, will give the yield of solid acids from the tallow in per cents. This method cannot be used for liquid mixtures of fatty acids rich in oleic acid, experiments by J. Schuster having shown that in such cases considerable quantities of stearic acid pass into the solution. (' b) Determination of Stearic Acid 1 On triturating the mixed fatty acid from a solid fat with dilute alcohol of specific gravity 0*911 in a mortar, the unsaturated fatty acids are almost completely dissolved, the palmitic acid is partially dissolved, whereas the stearic acid remains almost completely undis¬ solved. In a practical experiment the mixed solid acids had an iodine value of 2-3 only.—If the admixture of oleic acid be neglected, the proportion of stearic acid may be ascertained as described below under (c) Determination of Palmitic Acid, provided no other solid acid be present; lower fatty acids than palmitic acid would be dissolved by the alcohol, but if higher fatty acids, e.g. arachidic acid he sus¬ pected, the method would become entirely unreliable. Far better results, however, are obtained by treating the mixed fatty acids with an alcoholic solution of pure stearic acid saturated at 0° C. Hehner and Mitchell have shown by a series of experiments, carried out on pure stearic acid and on mixtures of stearic acid with 1 Hehner and Mitchell, Analyst, 1896, 321. VI DETERMINATION OF STEARIC ACID 199 (a) saturated acids lower than palmitic; (b) palmitic acid; (c) crude oleic acid ; (d) mixed saturated and unsaturated fatty acids (as e.g. mixed lard fatty acids), that stearic acid is left undissolved and can be determined quantitatively with great accuracy. The analysis is carried out as follows : Prepare a solution of stearic acid by dissolving about 3 grms. of pure stearic acid in 1000 c.c. of warm (methylated) alcohol of specific gravity 0‘8183 (con¬ taining 94‘4 per cent of alcohol by volume) in a stoppered bottle. Immerse the flask up to the neck in ice-water (kept in an ice-chest well protected against radiation of heat), and allow to stand in the ice-water overnight. After twelve hours, syphon off the mother liquor—without removing the flask from the ice-water—by means of a small thistle funnel immersed in the alcoholic solution and covered over with a piece of fine calico (so as to retain the separated stearic acid crystals in the flask). The funnel is twice bent at right angles, and is best fitted into a suction bottle, so that the clear liquor can be di’awn off by means of a filter pump. 0’5 grm. to 1 grm. of the mixed fatty acids under examination, if solid, or 5 grms. if liquid, are weighed off in a flask and dissolved in 100 c.c. of the above alcoholic stearic acid solution. The flask is placed in ice-water overnight, the mixture is agitated next morning while the flask is kept in the ice-water, and then allowed to stand for at least half-an-hour in the ice-water in order to promote crystal¬ lisation. The alcohol is then filtered off as described above, care being taken to draw off the solution as completely as possible. The residue in the flask is then washed three times in succession with 10 c.c. of the alcoholic stearic acid solution, and cooled down to 0° C. The crystals adhering to the calico of the thistle funnel are then washed off with hot alcohol into the flask, the alcohol is evaporated off, and the residue dried at 100° C. and weighed. This residue is considered as pure stearic acid. It is advisable to take the melting point of the acid; it should not be much below 68'5° C. As the walls of the flask and also the undissolved crystals retain a small quantity of the alcoholic stearic acid solution a correction must be applied. Hehner and Mitchell found that in their case the correction was 0'005 grm., which was deducted from the total weight of the residue found. This method unfortunately breaks down in the case of Japan wax fatty acids. In a number of experiments carried out upon mixtures of these acids with pure stearic acid, the latter could only be re¬ covered partially in some cases, whereas in other cases none at all was obtained. (c) Determination of Palmitic Acid In a mixture of palmitic and stearic acids the proportions of the several acids may be calculated from the mean molecular weight of the mixed fatty acids (determined as directed, p. 184), provided that this constant has been determined with the greatest accuracy. 200 CHEMICAL METHODS OF EXAMINING FATS AND WAXES CHA1>. The same method, of course, will hold good for any other mixture of two fatty acids, the molecular weights of which differ sufficiently. The mean molecular weight of the mixed fatty acids should be de¬ termined with not less than 5 grms. of substance. Then, letting M be the mean molecular weight of the mixed acids, M 1 and M 2 the molecu¬ lar weights of the single fatty acids, and x and y their percentages in the mixture, x and y can be calculated from the following equations r— hence * + ?/ = 100 x y _100 Mt(M -M 2 ) . 32=100 mcm,^) and y = 100 M 2 (M, - M) M(Mj - M 2 )‘ Thus, if for 5 grms. of a mixture of palmitic and stearic acids 37‘75 c.c. half-normal caustic soda be used, M equals 264-9, and we have, since M-^284, and M 2 = 256— *=100 284(264-9-256) 264-9(284-256) = 34-08. 100 parts of the mixed fatty acids contain therefore 34 - 08 parts of stearic acid, and 65 - 92 parts of palmitic acid. For other values the following table, due to Mangold, 1 will he found useful:— Mixed Stearic and Palmitic Acids Acid Value. Mgrms. of KOH per 1 grin. Mean Molecular Weight. 100 parts of the mixture contain Stearic Acid. Palmitic Acid. 197-5 284 100 198-5 282-6 95 5 199-5 281-2 90 10 200-5 279-8 85 15 201-5 278-4 80 20 202-5 277-0 75 25 203-5 275-6 70 30 204-6 274-2 65 35 205-6 272-8 60 40 206-7 271-4 55 45 207-77 270-0 50 50 208-86 268-6 45 55 209-95 267-2 40 60 211-06 265-8 35 65 212-18 264-4 30 70 213-30 263-0 25 75 214-45 261-6 20 80 215-60 260-2 15 85 216-77 258-8 10 90 217-95 257-4 5 95 219-13 256-0 — 100 1 Mangold-Marazza, Die Stearinindustrie, p. 167. VI DETERMINATION OF OLEIC, PALMITIC, & STEARIC ACIDS 201 This method, proposed by Hausamann and afterwards by Zulkowsky, although simple in principle, does not yield very accurate results, a small quantity of foreign substance—say of a hydrocarbon—causing considerable differences, as a simple calculation will show. Besides, an error of only 0T c.c. normal caustic in the titration may, for 5 grms. of substance, lead to an error of nearly 3 per cent. If, however, small quantities of oleic acid be present, the method is still applicable for the determination of palmitic acid, the difference between the molecular weights of stearic (284) and oleic (282) acids being too small to influence the result. An approximate estimation of the proportions of palmitic and stearic acids, when quite free from oleic acid, may be obtained from the melting and solidifying points by referring to the subjoined table given by Heintzf supplemented by more recent figures of Helmer and Mitchell. Mixtures of Palmitic with Stearic Acid Stearic Acid per cent. Palmitic Acid per cent. Melting Point ° C. Solidifying Point •c. Heintz. H. & M.2 100 0 69-2 68-5 90 10 67-2 66 "5 62 ; 5 80 20 65-3 64-2 60-3 70 30 62-9 61 - 5 59-3 60 40 60-3 59-4 56-5 50 50 56'6 55'6 55 40 60 56*3 55’5 54-5 32-5 67-5 55-2 54-5 54 30 70 55 T 54-2 54 20 80 57-5 56-5 53-8 10 90 60-1 59-0 54-5 0 100 62-0 61-8 (cl) Determination of Oleic, Palmitic, and Stearic Acids The proportions of these three acids in a mixture can be deter¬ mined from the iodine value and the mean molecular weight of the mixed acids. Let M be the mean molecular weight of the mixed acids, E the percentage of oleic acid as calculated from the iodine value [see (a)], x and y the percentages of steariG and palmitic acid, then we have the two equations— hence as + 2/ = 100 - E x y E _100 284 + 256 + 282“ If ,,(1001100 - 923E) - 2562816 * = M -987M-• 1 Liebig's Annalen, 92. 205. 2 The difference in the melting points of the stearic acid used by these observers will satisfactorily explain the discrepancies; purest stearic acid melts, however, at 7l°-71'5°C. 202 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. In candle-works it is important to know the proportion of the solid fatty acids (“stearine”) to the liquid acids (“oleine ”). For the rapid—although rough—estimation, the melting and solidifying points of the mixed acids are determined and compared with empirical tables worked out for all proportions of the mixed solid and liquid fatty acids. It is, however, not permissible to employ tables worked out say, for tallow, or any other fat. For not only the proportion of solid and liquid fatty acids varies in different fats, but also that of palmitic and stearic acids; besides, small quantities of foreign sub¬ stances, the influence of which almost disappears in other methods, cause considerable alterations of the melting and solidifying points (comp. “Tallow, and Palm Oil,” chap. xii. p. 750). A better and more reliable method would be to calculate the pro¬ portion of oleic acid from the iodine value (a), and to determine the stearic acid direct ( b ). Palmitic acid is then found by difference. vi. Approximate Determination of Liquid Fatty Acids— Oleie and Linolie The determination of the acids belonging to less saturated series than the oleic series is at the present state of our knowledge not yet possible, and we must have recourse to the qualitative methods detailed in chap. vi. p. 141. An attempt to arrive at approximately quantitative results has been made by Twitchell 1 by combining the lead salt method for the separation of solid acids from the liquid acids with the determination of the iodine number of the several fractions into which the liquid fatty acids were broken up. TwitchelVs method will be best illustrated by giving his process as applied to the examination of the fatty acids of lard in full, with such additional explanations as to render his method and his calcula¬ tions more readily intelligible than the perusal of the original paper does. 4 grrns. of lard fatty acids were dissolved in 95 per cent alcohol, and precipitated with 2 - 5 grms. of lead acetate dissolved in 20 c.c. of the same alcohol, both solutions being hot. The mixture was allowed to stand for one hour at 15° C. and filtered. 10 c.c. of the filtrate were drawn off, treated with ether and hydro¬ chloric acid, the isolated fatty acids dried in a current of carbon dioxide, and their iodine number determined. The remainder of the filtrate was kept at 0° C. for an hour, when a precipitate was obtained.. This precipitate was filtered off and washed with 90 per cent alcohol. The fatty acids were isolated from the filtrate, and their iodine value also determined. The examination of the original fatty acids and of these fractions gave the following results :— 1 Jour. Soc. Chem. Ind. 1895, 515. VI OLEIC AND LINOLIC ACIDS 203 Weight in Grms. Iodine Value. Original lard fatty acids 62-57 Fatty acids from filtrate at 15° C. . 0"2675 (46'81 per cent) 109-35 Fatty acids from precipitate at 0° C. 0-1020 Fatty acids from filtrate at 0° C. 0-1915 118-02 The fatty acids obtained from the precipitate at 0° C. solidified at 0° C. and melted at 7° C. [According to the table given, p. 753, it would contain 0‘8 per cent of solid acids.] Its iodine number was not determined, and it is only inferred by calculation that its iodine value would be nearly 90—the theoretical value of oleic acid—to make the iodine number of the mixture 109‘35. The percentage of the liquid acids can now be calculated as follows :— The percentage of the liquid fatty acids in the alcoholic filtrate at 15° C. is calculated from the portion drawn off, and was found to be 46'81 per cent. This, multiplied by the iodine number 109-35, gives 46 - 81 x 109'35 = 51T9 as the iodine required for the total liquid acids in the filtrate. The iodine number of the original fatty acids being 62’57, the difference 62*57 — 51T9 = 11-38 would correspond to the liquid acid left in the pre¬ cipitate, which is most likely oleic acid. 11*38 of iodine repre¬ sents 11-38x1-11 oleic acid (seep. 197) = 12-64 per cent of oleic acid. The total liquid acids in the original fatty acids are there¬ fore 46-81 + 12-64 = 59-45. The mean iodine number of the total 62-57 liquid acids must therefore be = 105*2. The linolic acid—if such be assumed to be present conjointly with oleic acid—can now be calculated from the theoretical iodine numbers of oleic and linolic acids, viz. 90 and 181, and the iodine number of the fatty acids from filtrate at 15° C., viz. 109"35, in the following manner :— Let * be the percentage of oleic acid, and y the percentage of linolic acid in the fatty acids from filtrate ; we then have x + y — 100 hence 90cc 100 + ® = 109-35 x = 78'5 per cent oleic acid y — 21’5 ,, ,, linolic acid and the percentage of linolic acids in the original fatty acids is 21-5 x 46-81 = 10-06. The oleic acid in the original fatty acids would then be 78’5 x 46"81 + 12’64 = 49‘39 per cent. Of course, this calculation holds good only for the several assump¬ tions made. 204 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. By working the lead-salt-ether method in the cold the normal lead salts are formed exclusively {Rose); it is, therefore, possible to calculate from the proportion of lead the mean molecular weight of the liquid fatty acids. Supposing three different unsaturated acids of known molecular weights are present, then the proportion of each of them can be calculated if the iodine value of the total fatty acids present has - been determined. Thus, if the total fatty acids contain p per cent of unsaturated fatty acids, and their iodine value be J t , then the mean iodine value J of the mixed unsaturated acids will be j _ lOOjb. V Let M x , M 2 , M 3 be the known molecular weights of the three unsaturated acids, M the mean molecular weight of the mixed acids as calculated from their lead salts, and J x , J 2 , J 3 the corresponding iodine values, then the percentages x, y, z of the three acids may be calculated from the following three equations :— x+y+z-p x y z _100 » X i X tJ o y J ioo + ioo + Ioo =J *- vii. Hydroxy Aeids A direct determination of the amount of hydroxylated acids in fats has been suggested by Fahrion, 1 in the first instance for boiled linseed oil. The method is based on the insolubility of the hydroxy acids in petroleum ether, the other fatty acids being easily soluble in that menstruum. The operation is carried out in the following way :—3-5 grms. of the sample of fat are saponified with alcoholic potash, the alcohol evaporated off, the soap dissolved in 50 to 70 c.c. of hot water, and decomposed by hydrochloric acid in a separating funnel. After cooling, the liquid is shaken thoroughly with 100 c.c. of petroleum ether (boiling below 80° C.), and allowed to stand until both the aqueous liquid and the petroleum layer have become clear. The hydroxy acids will then be found adhering to the sides of the funnel. The aqueous liquid is run off, the petroleum ether layer poured out, and the remaining hydroxy acids washed several times with petroleum ether. The hydroxy acids are then dissolved in warm alcohol, the alcoholic solution transferred to a tared basin, the alcohol evaporated off, and the residue dried for one hour at 100° to 105° C. and weighed. But experiments (unpublished) made by the writer have proved that this method is not generally applicable, and can, at best, Jour. Soc. Chem. Ind. 1891, 1015. VI HYDROXY ACIDS 205 only refer to oxidised acids of a similar nature to those found in boiled linseed oil. Pure hydroxystearic acid and dihydroxystearic acid are sparingly soluble in cold petroleum ether; the mixed fatty acids from castor oil behave very much like castor oil (chap. xi. p. 425), that is, they dissolve in an equal volume of petroleum ether. A mixture of castor oil fatty acids with oleic acid, however, could not be separated by means of petroleum ether. In the case of the nature of the hydroxy fatty acid in a fat being known, the proportion of it in the mixed fatty acids may easily be calculated, if the increase of weight of the mixed fatty acids attained on boiling with acetic anhydride be determined, by Lewkowitsch’s method (p. 190). Let M be the molecular weight of the mono¬ hydroxy acid, and i the increase of weight of A grms. of the mixed fatty acids, then the percentage of hydroxy acids y will be (cp. equa¬ tion (19), p. 190) lOOM-i y ~A. 42 ' In the case of the hydroxy acid containing n hydroxy groups, and consequently being able to assimilate n C 2 H 2 0 groups, we shall find _ JL00MK ^ A.?i.42’ The percentage of hydroxy acids, provided their molecular weight be known, may also be calculated from the acetyl value c of the fatty acids. Let M be the molecular weight of the monohydroxy acid, requiring 56100 mgrms. KOH for neutralisation, then the molecular weight of the acetylated acid will be M + 42, requiring 2x56100 mgrms. KOH for saponification. One grm. of the hydroxy acid will therefore require —, and one grm. of the acetylated product 2 x 56100 M + 42 ; the difference 2x56100 56100_56100(M - 42) M + 42 M M(M + 42) would represent the acetyl value of the pure hydroxy acid, or 100 per cent; having found c as the acetyl value of the sample, the per¬ centage of the hydroxy acid x will be obtained from the proportion hence 100.c. M. (M + 42) 56100 (M-42) ’ It has been assumed for this calculation that the anhydrides of the acetylated acids have been hydrolysed completely. '206 CHEMICAL METHODS OF EXAMINING FATS AND WAXES CHAr. viii. Lactones—Inner Anhydrides Some products of the fat industry, notably Turkey-red oils and “ stearine ” prepared from oleic acid by v. Schmidt’s process (see chap. xii. p. 747), contain considerable quantities of stearolactone, the inner anhydride of y-hydroxystearic acid. This lactone may be determined either volumetrically or gravimetrically. 1 (a) Volumetric Determination of Stearoladone Fatty acids separated from a fat by the usual method (p. 100) require for neutralisation the same amount of potash, whether aqueous caustic potash be used, or whether they be boiled with an excess of alcoholic caustic potash, or, in other words, the acid and saponification values of fatty acids are identical; consequently fatty acids have no ether value. If, however, lactones or inner anhyrides are in admixture with the fatty acids, the mixed fatty acids will show an ether value, since on titrating with aqueous caustic potash, especially in the cold, neutrality to phenolphthalein will be reached when all the free acids are neutralised, whilst the lactones, being neutral substances, are not saponified. On boiling with alcoholic potash, however, the lactones are converted completely into soaps, but on treating these soaps with a mineral acid, the lactones (but not the free fatty acids) separate out again. Consequently, fatty acids containing a lactone possess a definite ether value, from which the proportion of the lactone may be calculated if its molecular weight be known. Since this ether value does not disappear, the lactone being formed again on acidifying the saponified mass, this ether value has been termed “ constant ether value,” and the corresponding acid and saponifica¬ tion values —“ constant acid value ” and “ constant saponification value” Thus, if for a mixture of fatty acids and stearolactone the constant saponification value has been found 190, and the constant acid value 140, its constant ether value will be 50. The ether value of stearolactone being 198'9, the mixture contains per cent of stearolactone. 100 198-9 5 - = 25T3 (b) Gravimetric Determination of Stearolactone 10 to 100 grms. of the sample are saponified Avith an excess of boiling alcoholic potash. The resulting soap is then diluted with a little water, and, if there be any unsaponifiable matter present, extracted with petroleum ether after cooling. Next the strongly alkaline solution is diluted with hot water, acidified with hydrochloric acid, and evaporated on the water-bath until all the alcohol has been driven off. The fatty layer, floating on the top, is then separated from the 1 Benedikt, Monatshefte f. Chemie, 11. 71 ; Jour. Soc. Chem. Ind. 1890, 658. VI LACTONES 207 aqueous liquid, washed with water, and most carefully neutralised with aqueous caustic soda, the slightest excess of alkali being capable of saponifying part of the stearolactone, thus vitiating the result. One operates best in the following manner:—The whole substance is dissolved in 500 c.c. of alcohol, and 50 c.c. of it are titrated carefully with a dilute caustic soda solution (the titer of which need not be known), phenolphthalein being used as an indicator, until the solution becomes pink. The amount of caustic soda required for the remaining 450 c.c. having been calculated from this preliminary experiment, the greatest part of this quantity is added at once, and then again caustic soda carefully run in, drop by drop, until the solution becomes pink. The stearolactone is then separated from the soap solution by shaking the latter with petroleum ether, evaporating the petroleum ether solution, and weighing the residue. As a check, the saponification value of the stearolactone may be determined; its acid value and iodine absorption must, of course, be found = 0. Lewkowitsch 1 has discovered fatty acids in wool fat which are easily converted on heating to 100° C. into inner anhydrides. Some of these have been isolated by Darmstadter and Lifschutz, and have been described above as lanoceric acid and lanopalmic acid. Hydroxy acids especially will be likely to suffer dehydration with formation of inner anhydrides. On boiling mixtures containing inner anhydrides with acetic anhydride acetyl groups will be assimilated. This can readily be ascertained by weighing the acetylated product after thorough washing with boiling water to decompose anhydrides of fatty acids formed. An increase of weight will point unmistakably to the presence of hydroxy acid (see p. 190). ix. Glycerol For the determination of the proportion of glycerol which a fat yields on saponification, several methods have been proposed. (It would be incorrect to speak of the proportion of glycerol in a fat since glycerol is formed only on saponification.) The yield of glycerin obtainable by saponifying triglycerides has been given above; see table, p. 186. The older processes having for their object the isolation of glycerol in substance, such as Chevreul’s original method, are only suitable as qualitative methods, and the glycerol thus prepared may be tested by any of the reactions given above (p. 80). For quantitative purposes, however, they are not to be relied upon, yielding, as they do, results below the truth owing to volatilisation of small quantities of glycerol at 100° C. (p. 77). This source of error is avoided in David's process, 2 in which the concentration of the glycerol solution is not carried too far, but it introduces another error through the necessity of saponifying with barium hydrate (cp. p. 18). 3 Jour. Soc. Chem. Tnd. 1892, 139 ; 1896, 14. 2 Compt. rend. 94 (1882), 1477. 208 CHEMICAL METHODS OF EXAMINING FATS AND WAXES CHAP. 1. Determination of Glycerol by Titration with Caustic Potash This method is an application of Kuttstorfer’s process for examining fats (p. 151). According to the fundamental equation, in which R stands for the radicle of any fatty acid, C 3 H 5 (RO) 3 + 3KOH = C 3 H 8 0 3 + 3R . OK 3 molecules of caustic potash are required for the saponification of 1 molecule of neutral fat, yielding 1 molecule of glycerol. There¬ fore, for every 168-3 grms. of KOH used, 92 grms. of glycerol will be obtained, consequently 1 grm. of KOH is equivalent to 0‘54664 grm. of glycerol. 1 If, therefore, the ether value E has been determined (p. 154), the theoretical yield of glycerol G will be G= Ex 0-54664x 100 1000 = 0-054664 E (cp. equation (10), p. 187). This method being an indirect method, has naturally all the faults inherent in that class of analysis, and must be used with caution. Its rapidity, however, makes it suitable for determinations in works. If diglycerides or wax-like substances be present in the fat the method obviously becomes useless. 2. Determination of Glycerol by Oxidation Processes (1) Oxidation by Means of Potassium Permanganate in Alkaline Solution On being oxidised in a strongly alkaline solution at the ordinary temperature with potassium permanganate, glycerol is converted quantitatively into oxalic acid, carbonic dioxide, and water, according to the following equation :— C 3 H 8 0 3 + 30. 2 =C 2 H 2 0 4 + C0 2 + 3H 2 0. This reaction, which was originally suggested by Fox and Wan- klyn 2 as a basis for a quantitative method, has been worked out by Benedikt and Zsigmondy 3 in the following manner :—Saponify 2 to 3 grms. of the sample of fat with caustic potash and pure methyl alcohol, evaporate the latter, dissolve the soap in hot water, and decompose it with dilute hydrochloric acid. Then warm until the liberated fatty acids have separated out as a clear oily layer. In the case of a liquid fat some paraffin wax is best added so as to obtain a solid cake on cooling. Next filter from the fatty acids into a spacious flask, wash well, and neutralise with caustic potash, using methylorange as an indicator. Then add 10 grms. of caustic potash in sticks, and run in a 5 per cent solution of potassium permanganate until the liquid no 1 Zulkowsky, Berichte, 16. 1140 ; 1315. . 2 Chem. News, 53. 15. 3 Jour, Soc. Chem. Ind, 1885, 610. VI DETERMINATION OF GLYCEROL BY OXIDATION 209 longer appears green, but blue or blackish. Instead of a solution, finely powdered potassium permanganate crystals may also be used. Heat to boiling, when hydrated manganese dioxide separates and the solution becomes red; discharge the colour by adding carefully the quantity of sulphurous acid solution required (but not more) for the reduction of the excess of the permanganate, taking care that the solution still remains strongly alkaline. Filter through a plain filter of sufficiently large size to hold at least one-half of the liquid, and wash the precipitate well with boiling water. It may happen that with the last wash-waters small quantities of hydrated manganese dioxide pass through the filter, but this does not interfere at all with the accuracy of the process. Acidify the filtrate with acetic acid, whereby sufficient sulphurous acid is set free to reduce the manganese dioxide, and heat the solution, being about 600 to 1000 c.c., almost to the boiling point, and precipi¬ tate with 10 c.c. of a 10 to 12 per cent solution of calcium chloride or calcium acetate. (If more of the precipitant be used, considerable quantities of calcium sulphate are thrown down, vitiating the quantitative determination.) The precipitate contains silicic acid in addition to calcium oxalate, hence the amount of oxalic acid cannot be calculated from the weight of the calcium carbonate (or calcium oxide) after ignition. Therefore the amount of oxalic acid must be either determined volumetrically, or inferred from the alkalinity of the ignited residue. In the latter case dissolve the ignited precipitate in an accurately measured excess of half-normal hydrochloric acid, and titrate with half-normal caustic soda, using methylorange as indicator. If the titer of the acid be expressed in terms of sodium carbonate, 106 parts of C0 3 Na 2 are equivalent to 92 parts of glycerol. Alien 1 has somewhat modified this process, and proceeds in the following manner :—The fat is saponified with aqueous caustic potash in a closed flask. The oxidation is effected as described above, but sodium sulphite is used for reducing the excess of permanganate. The liquid containing the precipitated hydrated peroxide of manganese is then poured into a 500 c.c. flask, made up to 500 c.c., and 15 c.c. of hot water are added above the mark, this being an allowance for the volume of the precipitate and for the expansion of the hot liquid. The solution is next poured through a dry filter, and 400 c.c. of the filtrate, when cold, are measured off accurately, acidu¬ lated with acetic acid, and precipitated with calcium chloride. The precipitate is filtered off, washed well, and rinsed into a porcelain dish after piercing the filter. The neck of the funnel is then plugged and the filter filled with dilute sulphuric acid; after standing for a few minutes it is allowed to run into the dish. Sufficient sulphuric acid is then added to bring the total amount of acid up to a quantity equal to 10 c.c. of concentrated sulphuric acid, when the solu¬ tion is warmed to 60° C. and titrated with potassium permanganate. If decinormal permanganate be used, each c.c. used corresponds to 0’0045 grm. of C 2 H 2 0 4 , or to 0'0046 grm. of glycerol. Commercial Organic Analysis, ii. 290. P 210 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. In connection with this process the following notes may he useful: —Methyl alcohol is used in the saponification of the fat instead of ethyl alcohol, as the latter may, under certain conditions of concentra¬ tion, and for a definite percentage of alkali, give rise to the formation of oxalic acid. The errors resulting from this cause will be found to increase with the amount of alcohol retained by the soap on evapora¬ tion. Again, if a complete elimination of the alcohol be attempted by repeated evaporation of the dissolved soap, loss of glycerol may result. The liquid that is oxidised contains besides glycerol all the soluble fatty acids originally combined with it in the fat. On working strictly according to the directions as given above, neither oxalic acid nor any other organic acid yielding a calcium salt insoluble in acetic acid will be formed. Therefore, it may be safely inferred that the presence of the soluble fatty acids in no way interferes with the cor¬ rectness of the determination of the glycerol. Johnstone j 1 it is true, maintains that in presence of butyric acid the process is useless, this acid being nearly wholly converted into oxalic acid, but both Hehner 2 and Mangold 3 have shown that in the process as given by Benedikt and Zsigmondy no oxalic acid is formed. An explanation of Johnstone's error may be found in Mangold's observation, that butyric acid yields oxalic acid when boiled for a considerable time with an excess of potassium permanganate. An excess of sulphurous acid must be carefully avoided, since in presence of hydrated peroxide of manganese sulphurous acid oxidises the oxalic acid formed. This error is obviated by Allen's proposal to use sodium sulphite instead of sulphurous acid. If the hydrated per¬ oxide be removed by filtration, and the solution be acidified with acetic acid, no action on the oxalic acid can take place. But as towards the end of the washing small quantities of the peroxide pass through the filter, and are reduced by the sulphurous acid set free by the acetic acid, and, moreover, since small quantities of calcium sulphite may be admixed with the precipitated calcium oxalate, it will be best to avoid the use of sulphurous acid or of a sulphite altogether. Herbig 4 substitutes, therefore, for the sulphite, hydrogen peroxide ; he further recommends the use of a smaller quantity of potassium permanganate. Herbig's method has been examined by Mangold , 5 and the following modification of the Benedikt-Zsigmondy process has been recommended by him as yielding reliable results :—The filtrate from the fatty acids, containing from 0‘2 to 0'4 grm. of glycerol, con¬ veniently made up to 300 c.c., is placed in a litre flask, and 10 grms. of potassium hydrate, and as much of a 5 per cent permanganate solution as will correspond to one and a half times the theoretical quantity required for the oxidation of the glycerol (6‘87 parts of Mn0 4 K being the amount required by theory for one part of C 3 H 8 0 3 ) are added. This operation is conducted in the cold and with constant shaking. Allow to stand for half an hour at the ordinary tempera- 1 Jour. Soc. Chem. Ind. 1891, 204. 2 Ibid. 3 Ibid. 1891, 803. 4 Inaugural Dissertation. Leipzig, 1890. 5 Jour. Soc. Chem. Ind. 1891, 803. VI DETERMINATION OF GLYCEROL BY OXIDATION 211 ture, and add sufficient hydrogen peroxide, avoiding, however, a large excess, to completely decolourise the liquid. Then make up to 1000 c.c., shake well, and filter 500 c.c. through a dry filter. Boil the filtrate for half an hour to decompose all hydrogen peroxide, allow to cool to 60° C., acidify with sulphuric acid, and titrate with standard permanganate solution. The following table contains the saponification values of several fats, and the theoretical quantities of glycerol obtainable from them, contrasted with the actual results obtained by Beneclikt-Zsigmondy’s method. The agreement will be found satisfactory, if we consider that the saponification values and yields of glycerol have been deter¬ mined with different samples of fats. In order to prove the utter unreliability of the older methods, von der Becke’s results are given in the last column as obtained by isolating the glycerol in sub¬ stance :— Kind of Oil. Saponification Value. Glycerol. Calculated from Saponification Value. Found by Benedikt- Zsigmondy. Found by von der Becke. Olive oil . 191-8-203 10-49-11T0 10-15, 10-38 6-41 Linseed oil . 188-4-195-2 10-24-10-66 9-45, 9-97 6-20 Cocoa nut oil. 270-275 14-76-14-83 13-3, 14-5 Tallow 196-5 10-72 9-94, 9-98, 10-21 7-84 Butter fat 227 12-51 11-59 10-59 If the glycerol solution prepared from the fat contains any other sub¬ stance yielding oxalic acid on oxidation, as notably in the case of highly oxidised linseed oil, the Benedikt-Zsigmondy process is, of course, useless (cp. also below 3). (2) Oxidation with Potassium Permanganate in Acid Solution Planchon 1 oxidises glycerol completely to carbonic dioxide and water by potassium permanganate and sulphuric acid according to the following equation— C 3 H 8 0 3 + 70 = 3COo + 4H 2 0. This method has been examined and recommended as yielding correct results by Herbigf Griinwaldf and Suhrf when “ chemically pure glycerin ” was used in test experiments. The carbonic acid evolved from the glycerol is determined in exactly the same way as in the ultimate analysis of carbon compounds. The filtrate from 3 grms. of saponified fat, containing about 0’3 grm. of glycerol, is concentrated in a flask of 300 c.c. capacity to about 100 c.c. The flask is attached to an inverted condenser, and the latter is 1 Jour. Soc. Chem. Ind. 1888, 779. 2 Inaugural Dissertation , 1890. 3 Jour. Soc. Chem. Ind. 1889, 308. 4 Inaugural Dissertation. Miinchen, 1892. 212 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. connected with a calcium chloride tube and the caustic potash bulbs used for the absorption of carbonic dioxide. 4 grrns. of permanganate dissolved to a 5 per cent solution and 15 grms. of concentrated sul¬ phuric acid, previously diluted with 50 c.c. of water, are quickly introduced into the flask, and the solution heated to boiling point. A current of air drawn through the apparatus will drive over the last traces of carbonic dioxide. It must, however, be noted that commercial potassium perman¬ ganate contains quantities of carbonates appreciable enough to seriously affect the correctness of the result. If, therefore, determination of glycerol by complete oxidation be wished, it will be preferable to employ the following method proposed by Hehner, sub (3). A serious objection to this method, as well as to the following, with which it is identical in principle, is that any organic substance other than the glycerol will also yield carbonic acid, and render these determinations practically useless. In the Benedikt-Zsigmondy method erroneous results will only be obtained in the presence of organic substances yielding oxalic acid on oxidation, and in consequence of this limitation of the possible errors it will be found to give more reliable results than any other oxidation process. (3) Oxidation with Bichromate of Potash and Sulphuric Acid This method has been recommended by Legler, Burghardt, Cross and Bevan, and Hehner 4 Cross and Bevan 2 measure the carbonic acid evolved, Legler proposes to weigh it, whilst Hehner recommends to determine the glycerol volumetrically by measuring the volume of standard bichromate solution required for the oxidation. Hehner has exhaustively examined his method, and obtained satis¬ factory results. The standard solutions required are :— 1. Solution of potassium bichromate containing 74‘86 grms. of Cr 0 0 7 K 2 , and 150 c.c. of strong sulphuric acid per litre. 3 The exact oxidising value of the solution must be ascertained by titration with a standardised solution of ferrous sulphate or of pure ferrous am¬ monium sulphate or of pure iron wire. 2. Solution of ferrous ammonium sulphate containing about 240 grms. per litre. 3. Bichromate solution, ten times more dilute than solution 1. The ferrous solution is exactly standardised upon the stronger bichromate solution, 1 c.c. of which should correspond exactly to 0‘01 grm. of glycerol. For the determination of the yield of glycerol from a fat, saponify 1 Jour. Soc. Ghem. Ind. 1889, 4. 2 Ghem. News, 55. 2, and Analyst , 1887, 44. The same method has been proposed again by Gantter, Jour. Soc. Ghem. Ind. 1895, 895. 3 It is safer to keep the not-acidified bichromate solution in stock, and to add the sulphuric acid when testing. VI DETERMINATION OF GLYCEROL AS TRIACETIN 213 about 3 grms. of the sample, weighed off accurately, with alcoholic potash. Take care not to drive off all the alcohol lest any glycerol be volatilised. Dilute to about 200 c.c. and decompose the soap with dilute sulphuric acid. Filter off the liberated fatty acids, and boil the filtrate vigorously in a covered beaker to about half its volume, when all the alcohol will have been evaporated off. Then add 25 c.c. of concentrated sulphuric acid, suitably diluted, and 50 c.c. of the stronger bichromate solution, and heat to near boiling for about two hours. Titrate back the excess of bichromate with an excess of the ferrous ammonium sulphate solution, and ultimately the latter with the dilute bichromate solution, using potassium ferri- cyanide as an indicator. 3. Determination of Glycerol by the Aeetin Process Since in the saponification of fat a more or less impure glycerol is necessarily obtained, those processes based on the complete oxida¬ tion of glycerol will undoubtedly yield too high results; even the Benedikt-Zsigmondy process may give too high values, when some of the saponification products are converted into oxalic acid. Therefore LewJcowitsch 1 recommends the aeetin process (see chap. xii. p. 806) for the determination of the yield of glycerol from a fat. The fat is saponified in the usual way, the resulting soap decom¬ posed with sulphuric acid, and the liberated fatty acids filtered off. The filtrate is neutralised with an excess of barium carbonate, and boiled down on the water-bath until most of the water is driven off. The residue is next exhausted with a mixture of ether and alcohol, the ether-alcohol driven off for the most part at a gentle heat, and the residue dried in the desiccator. It is not necessary to await constant weight, since the glycerol can be determined at once in this hydrous crude glycerin. x. Higher Aliphatic Alcohols On saponifying a fat or wax, any higher alcohols of the aliphatic series present, as cetyl alcohol, ceryl alcohol, etc., are isolated together with the other unsaponifiable substances, and the alcohols may be detected in this mixture as detailed in the following chapter. The following methods furnish a means of obtaining a measure of the proportion of alcohols in a fat or a wax without resorting to their isolation :— 1. Saponify 10-20 grms. of the fat with alcoholic potash, or in case of a wax with aqueous potash (cp. Benedikt and Mangold’s method under “Beeswax,” p. 661), dilute the soap with water, acidify and boil until the fatty substance has separated as a clear layer. Syphon off the aqueous solution, wash the fatty layer until free from mineral acid, filter and dry. The fatty substance thus obtained consists of a mixture of free fatty acids, aliphatic alcohols, and possibly of hydro- 1 Chemiker Zeitung, 1889, 659. 214 CHEMICAL METHODS OF EXAMINING FATS AND WAXES chap. carbons. Weigh off accurately part of the mixed substances and de¬ termine their acetyl value. Provided hydroxy acids are absent and anhydrides formed (cp. 164) are hydrolysed, we may calculate from the acetyl value the proportion of hydroxyl combined with the radicle of the alcohols (alcoholic hydroxyl), or of hydrogen contained in the alcoholic hydroxyl group. If only one alcohol of known molecular weight be present, it is, of course, possible to determine its quantity. Instead of determining the acetyl value, the increase of weight after boiling with acetic anhydride may be determined (cp. p. 190). Also in this case the proportion of alcohol can be found, if only one alcohol of known molecular weight be present and hydroxy acids are absent. 1 2. The following method proposed first by C. Hell 2 has been employed later by Buisine for the examination of beeswax. It is based on the fact that, on heating an aliphatic alcohol with soda-lime, one molecule of the corresponding fatty acid is formed, with evolution of two molecules of hydrogen, as expressed by the equation— C 16 H 33 . OH + NaOH = C 36 H 31 0 2 Na + 2H 2 . Cetyl alcohol. Sodium palmitate. It is therefore possible to infer from the quantity of gas liberated the amount of alcohol originally present. According to Hell, the sub¬ stance, intimately mixed with soda-lime, is introduced into the tube i (Fig- 40), and the mixture covered with soda-lime. In order to reduce the volume of air to the smallest possible amount, the sealed tube k is placed inside tube i. The latter is closed by a perforated india-rubber stopper p provided with tube r, which connects i with a Hofmann gas burette, filled completely with mercury, and closed at the top by means of the three-way tap h. The tube i is then immersed in an air-bath provided with a thermometer. Tube i is at first brought into communication with the air by tap h, then the height of the barometer and temperature of the air is taken, and i con¬ nected with the burette by suit- Fi s- 40 - ably turning the three-way tap. * Part of the mercury is then with¬ drawn by tap q, and the air-bath heated to 300°-310° C., until the level of the mercury remains constant. The apparatus is then allowed to cool down to the temperature of the room, when the original 1 Lewlcowitsch, Jour. Soc. Chein. Ind. 1896, 14. 2 Liebig’s Annalen, 223. 269. VI ALIPHATIC ALCOHOLS 215 pressure is re-established by adding mercury. The volume of gas is then read off and calculated for 760 mm. pressure and 0° C. The hydrogen may either be measured saturated with moisture, when a correction for the tension of the water vapour must be made, or by previously drying the gas. This is best done by taking a longer tube i, and placing over Jc a layer of strongly heated soda-lime. A. and P. Buisine 1 have proved that the reaction does not proceed quantitatively if a wax be heated directly with potasli-lime (1 part of potash and 2 parts of lime). They proceed, therefore, in the following way :—2-10 grms. of a wax, weighed accurately, are melted in a porcelain crucible, and an equal weight of finely powdered caustic potash stirred into the melted mass. The hard mass obtained on cooling is carefully powdered and intimately mixed with three parts of potash-lime for every part of wax weighed off. The mixture is filled into a test-tube or a pear-shaped flask, taking care that the vessel is nearly filled completely, and placed in an iron still, filled with mercury, and closed by a cover having three nozzles. Through the one passes the outlet tube from the glass vessel containing the substance, whilst into the second is fixed a thermometer; the third nozzle is provided with a long iron tube to condense and lead away the vapours of mercury. Instead of collecting the gas in a Hofmann burette, A. and P. Buisine prefer to use the apparatus designed by DuprS, and shown in Fig. 41. 1 Monit. scientif. 1890, 1127. 216 CHEMICAL METHODS OF EXAMINING FATS AND WAXES ch.vi The gas evolved can be made to enter the vessel E either from the top —by opening tap A—or from the bottom—by opening tap B. The glass tubes provided with the taps A and B are of very small inner diameter without, however, being capillary tubes. When all the connections have been made, bottle E is filled with water by raising bottle F until water enters C. Tap D is then closed, bottle F lowered, tap A opened, and the mercury heated. At 180° C. the reaction will commence; the temperature is, however, raised to 250° C. and kept thereat for two hours. If gas is liberated copiously the tap A is closed and B opened; thus it is easier to control and watch the progress of the reaction. When bubbles of gas no longer rise through the water, tap B is closed again and A opened. The apparatus is then allowed to cool down, and the gas is introduced into the eudiometer, where it is measured; the volume read off is calculated for 760 mm. pressure and 0° C. Thus the volume of gas obtained for 1 grm. of substance is found. If this has to be calculated to, say, myricyl alcohol, the number of c.c. of hydrogen found must be multiplied by 0 - 984. On raising the temperature to 310° C. no larger volume of gas was obtained. A higher temperature than 250° C., however, should be avoided, since any oleic acid present may become converted into palmitic acid with evolution of hydrogen. It may be pointed out that cholesterol remains practically un¬ changed when treated with potash-lime in the manner described. 1 1 Lewkowitsch, Jour. Soc. Ohern. hul. 1896, 14. CHAPTER YII DETECTION AND QUANTITATIVE DETERMINATION OF UNSAPONIFIABLE MATTER IN FATS AND WAXES We comprise here in the term “ unsaponifiable matter ” all those substances that do not dissolve in water or combine with caustic alkalis to form soluble soaps. Strictly speaking, glycerol itself, not being saponifiable by alkalis—in the same way as wax alcohols—is “ unsaponifiable,” and in this strict sense only the fatty acids would be completely saponifiable, but not so the neutral glycerides, containing, as they do, about 5 per cent of the glycerol-yielding radicle C 3 H 2 . However, as glycerol is soluble in water it does not come under the head of “ unsaponifiable matter,” and, therefore, in a wider sense the neutral fats are considered as completely saponifiable. Resin, which is often met with in fatty substances, is almost com¬ pletely saponifiable. This substance will be fully considered in the following chapter. Waxes, although hydrolysed completely on boiling with alcoholic potash, are usually termed partially saponifiable, on account of their yielding considerable quantities of “ unsaponifiable ” alcohols insoluble in water. We have, therefore, to consider here, besides waxes, the possible presence in any given fatty substance of paraffin wax, cerasin, mineral oils, neutral tar oils, and resin oils. Resin oils contain but small quantities of saponifiable substances, whilst paraffin wax, cerasin, mineral oils, and neutral tar oils are entirely unsaponifiable. Some fats contain in their natural state small quantities of un¬ saponifiable matter in the shape of hydrocarbons, or, more frequently, of cholesterols. 1. Detection of Unsaponifiable Matter A rapid method for the detection of unsaponifiable matter, if present in considerable quantities, consists in boiling the sample of fat with alcoholic potash, and adding to the soap solution aqueous ammonia, when a turbidity will appear (cp. p. 100). Holde 1 draws 1 Jour. Soc. Chem. Ind. 1889, 735. 218 DETERMINATION OF UNSAPONIFIABLE MATTER chap. attention to the necessity of employing strong alcohol and of avoiding excess of ammonia. He recommends to test in the following manner :— Heat in a test-tube a piece of caustic potash about the size of a pea with 5 c.c. of absolute alcohol until dissolved ; add 3 or 4 drops of the sample of fat, heat again and pour 3-4 c.c. of distilled water into the test-tube. The presence of even one per cent of unsaponifiable matter will cause distinct turbidity. 2. Quantitative Determination of Unsaponifiable Matter i. Gravimetric Methods Preparatory to the determination of unsaponifiable matter the sample of fat must be saponified. To accelerate the process, in the case of fats that are not readily saponifiable, it has been proposed to add some easily saponifiable fat. It will, however, be preferable in such cases to have recourse to the method given in chap. ii. p. 23, for the hydrolysis of not readily saponifiable fats. On saponifying a fat containing hydrocarbons in the usual manner, and evaporating oft the alcohol by boiling the strongly diluted aqueous soap solution, the unsaponifiable matter will, for the most part, sepa¬ rate as an oily layer on the top of the soap solution. A small quantity, however, will always remain dissolved in the aqueous solution, and therefore such methods as Geissler’s and Dalican’s, proposing to separate the oil and to weigh it, must naturally give too low results. The following two methods, however, can be recommended as reliable:— (a) Extraction of the Soap Solution with Ether or Petroleum Ether The extraction of the unsaponifiable matter is effected by repeatedly shaking the saponified mass with ether or petroleum ether and separating the two layers by means of a separating funnel. The small quantities of soap that pass into the extract are removed by washing the ethereal solution with water. H. Schwarz 1 and Neu¬ mann 2 have designed special apparatus for this purpose, but their employment for the purposes of fat analysis cannot be recommended. Regarding the choice of the solvent, it is always safer to use common ether in preference to petroleum ether, although the former extracts in most cases larger quantities of soap than the latter. For Lewhowitsch 3 found in the case of shark liver oil and some kinds of whale oil that petroleum ether gave very capricious results, all of which were far too low, owing, no doubt, to the “unsaponifiable matter” from these oils being very sparingly soluble in petroleum ether, whereas constant results were obtained on using common ether. Due attention must be paid to the fact that the solubility of soaps in 1 Jour. Soc. Chem. Ind. 1884, 649. 2 Berichte, 18 (1885), 3061. 2 Jour. Soc. Chem. Ind. 1896, 14. VII GRAVIMETRIC METHODS 219 ether and petroleum ether is increased by the presence of hydrocarbon oils and wax alcohols \ in accurate analysis it is necessary, therefore, after evaporating off the solvent, to shake the extracted unsaponifiable mass with a little warm water, and to extract again with ether or petroleum ether. Lewkowitsch 1 recommends to incinerate the extract; any residue giving an alkaline reaction on treatment with a little water would point to the presence of soap in the unsaponifiable matter. By titration with an acid the amount of alkali can be found and the amount of soap approximately calculated. Very often a distinct separation into two well-defined layers does not take place readily, emulsions being formed on shaking that require a very long time to separate, if, indeed, they separate at all, as notably in the case of wool fat. In such cases it will be found most convenient to add a little alcohol or glycerin after shaking, if ether has been used for extraction, and to impart a slight rotatory movement to the separating funnel without, however, agitating. If petroleum ether has been employed, the formation of emulsions is best avoided by adding to the alcoholic soap solution left after saponification not more than an equal volume of water. Sometimes a flocculent layer will appear between the aqueous solution and the solvent. In the case of wool fat Lewkowitsch ^ has shown that these flocks consist of a soap formed from fatty acids of high molecular weight, which is insoluble in cold water. The appearance of this flocculent stratum, however, does not interfere with the correct estimation of the unsaponifiable matter. The petroleum ether should not contain any hydrocarbons boiling above 80° C.; otherwise it will be found almost impossible to remove the last portions of the solvent without seriously vitiating the results. The commercial article sold as boiling below 170 F. should not be taken on trust. It is, therefore, imperative to fractionate the petroleum ether, using a good dephlegmating column, say Hempel s, and to discard any fractions boiling above 80 J C. (cp. p. 89). Considering the importance of the subject, I think it best to describe fully several methods proposed for the estimation of the unsaponifiable matter. On the whole, preference should be given to the method recommended by Allen and Thomson. Allen and Thomson 3 recommend to saponify 5 grms. of the sample with 25 c.c. of alcoholic caustic soda, containing 80 grms. of NaOH in 1000 c.c., in a porcelain basin in a water-bath, and to boil down to dryness. The resulting soap is dissolved in 50 c.c. of hot water, and transferred to a separating funnel of about 200 c.c. capacity, using about 20 to 30 c.c. of water for rinsing the dish. After cooling, 30 to 50 c.c. of ether are added and the solution thoroughly shaken. Addition of a little alcohol will accelerate the separation. The soap solution is then run off and may be exhausted again with fresh ether. The ethereal solutions are united, washed with a small quantity of water to free them from any dissolved soap, and transferred to a tared 1 Jour. Soc. Ghem. Lid. 1892, 139 ; 1896, 14. 2 Ibid. 1892, 136. 3 Ghem. Nows. 43. 267. 220 DETERMINATION OF UNSAPONIFIABLE MATTER CHAP. flask. The ether is distilled off on the water-bath, and the residue dried and weighed. Nitsche 1 saponifies 10 grms. of fat with 7 grms. of caustic soda solution of specific gravity T35, and 30 grms. of 90-96 per cent alcohol, afterwards adding 40 grms. of glycerin, specific gravity F250, and exhausting the solution with 100 c.c. of petroleum ether. Morawski and Demski 2 treat 10 grms. of the fat with 50 c.c. of alcohol and 5 grms. of caustic potash previously dissolved in the smallest quantity of water. The flask in which the fat is saponified is connected with an inverted condenser, and after half an hour’s boiling 50 c.c. of water are added and the mass allowed to cool. It is then transferred to a separating funnel and shaken out with petroleum ether. When the two layers have separated, the aqueous layer is drawn off as completely as possible, and the petroleum ether repeatedly washed with water without, however, uniting the washings with the main soap solution. Instead of running the ethereal solution directly into the tared flask, it is first drawn off into a dry flask, and from this poured into the tared flask, when any drops of water will remain behind. The main soap solution is again extracted in the same way, and the petroleum ether added to the first portion. On distilling off the petroleum ether the unsaponifiable matter will be left behind. Spitz and Honig 3 recommend washing the petroleum ether layer with 50 per cent alcohol instead of water, thus shortening the time required for the separation of the two layers. Gawalowski 4 states that only alkaline soaps are soluble in petro¬ leum ether, whereas neutral soaps are absolutely insoluble. He recommends the following procedure for obtaining the petroleum ether solutions free from soap:—Saponify 10 parts of the sample of fat with alcohol and 2'5 j^arts of solid caustic potash, dissolve the soap in water, evaporate off the bulk of alcohol, and add, first, calcium chloride solution and then powdered sodium bicarbonate until the solution has nearly ceased to be alkaline. On boiling, owing to the formation of sodium carbonate, the solution acquires an alkaline reaction, but the carbonate, being insoluble in petroleum ether, does not interfere with the accuracy of the analysis. (b) Extraction of the Dry Soap with Solvents For the extraction of the dry soap ether cannot be recommended, as larger quantities of soap would be dissolved than in the foregoing processes. Therefore petroleum ether or chloroform or acetone are, as a rule, preferable. Allen and Thomson have thus determined accurately the unsaponi¬ fiable matter in various fats (cp. p. 6). Their modus operandi is the following :—10 grms. of the sample of fat are saponified in a porcelain dish of 5 inches diameter with 50 c.c. of 8 per cent alcoholic caustic 1 .Tour. Soc. Chem. Ind. 1884, 322. 2 Ibid. 1886, 179. 3 Ibid. 1891, 1039. 4 Zeit. analyt. Chemie , 26. 330. VII EXTRACTION OF SOAP WITH SOLVENTS 221 soda, by gently boiling on the water-bath with constant stirring until the soap commences to froth ; 15 c.c. of methyl alcohol are then added, and the boiling continued until the soap is dissolved. Next 5 grms. of sodium bicarbonate are stirred into the mass, and 50-70 grms. of recently, ignited pure sand mixed with it. After drying for twenty minutes in a water-oven, the mass is transferred to a Soxhlet apparatus, and extracted with petroleum ether, completely volatile below 80° C. The petroleum ether is then distilled off and the residue weighed. For the determination of mineral oil in fatty oils, Finkener 1 uses the following process, which is but a slight modification of that pro¬ posed by Allen and Thomson :—Heat 10 grms. of the sample for fifteen minutes on a water-bath with 50 c.c. of nearly normal alcoholic solution of caustic soda, add 5 grms. of dry sodium bicarbonate to convert the excess of caustic soda into carbonate, and heat on the water-bath until the alcohol has been driven off. Transfer the hot mass to a stoppered cylinder, allow to cool, and shake with 300 c.c. of petroleum ether for some time. Filter into a dry flask, distil off the bulk of the petroleum ether, pour the solution on to a watch glass, and weigh after evaporating off the remainder of the petroleum ether. According to Allen the methods described under (a) cannot be used for the determination of the unsaponifiable portion of beeswax, carnaiiba wax, and other substances containing myricyl alcohol, the latter being but sparingly soluble in the cold solvent. In such cases it is best to neutralise the soap exactly with acetic acid, using phenol- phthalein as an indicator, and to precipitate with lead acetate. The precipitate is washed, dried, mixed with sand, and boiled out re¬ peatedly with petroleum ether. In the case of shark liver oil and some kinds of whale oil, ex¬ amined by Lewlcowitsch, 2 very considerable quantities of soap were dissolved together with the alcohol, so that petroleum ether was use¬ less in these cases. On incineration the extract should yield but traces of ash, thus proving that only traces of soap have been dissolved. The above method, generally yielding good results, becomes, however, less accurate in the case of fats mixed with both mineral and resin oils, perceptible quantities of soap passing into the petroleum ether under these conditions. Horn 3 proposes to extract the saponified mass with chloroform , which is stated not to dissolve soap even in presence of free alkali, so that addition of bicarbonate becomes unnecessary. Grittner 4 also recommends this solvent, but advises to mix the soap with sand if the fat contains considerable quantities of mineral oil. The sand must have been washed previously with hydrochloric acid, as any lime 1 Jour. Soc. Chem. Ind , 1886, 457. s Ibid. 1896, 14. 3 Ibid. 1888, 696. 4 Ibid. 1890, 772. 222 DETERMINATION OF UNSAPONIFIABLE MATTER CHAP. present would cause the formation of a lime soap, which is soluble in chloroform. The copper, zinc, cadmium, aluminium, barium, strontium, mag¬ nesium, and calcium soaps are soluble in both common ether and petroleum ether to some extent. The least soluble are the calcium salts. Several chemists recommend, therefore, to operate on the lime salts. Thus Donath 1 proposes for the determination of paraffin wax in candles to convert the alkali soaps into lime soaps previous to the extrac¬ tion. He proceeds in the following way : 6 grms. of the sample are saponified with alcoholic potash, and the alcohol driven off. The soap is then dissolved in hot water and calcium chloride solution added. If considerable quantities of paraffin wax are present, a good plan is to add a little sodium carbonate before precipitating, so as to obtain calcium carbonate, which will render the precipitate more powdery. The lime soap containing all the paraffin is washed on to the filter, dried at 100° C., reduced to a fine powder, and extracted in a Soxhlet tube with petroleum ether. The error of the method is stated not to exceed 0 - 3 per cent. Herbig 2 uses for the determination of the unsaponifiable matter in wool fat acetone , after having converted the potash soaps into lime soaps in the manner just described. (His process is not described here in full, as he does not completely saponify the wool fat, so that his “ unsaponifiable ” consists of the actual unsaponifiable matter plus that portion of wool wax which is not saponified by the ordinary method of saponification.) ii. Volumetric Methods Lacombe’s Process . 21 —If a mixture of a fat, of known composition, and of unsaponifiable substances has to be examined, the saponifica¬ tion value of the former supplies a ready means of determining volumetrically the amount of unsaponifiable matter. Let S x be the saponification value of the sample, and S the saponi¬ fication value of the pure fat, S of course being greater than S x , then evidently the percentage of unsaponifiable matter U will be In the presence of waxes, of course, this method cannot be used. Instead of determining the saponification value of the fat, Lacombe prefers to titrate its fatty acids. The sample is saponified in the usual manner, and an accurately weighed quantity of the mixed fatty acids is dissolved in alcohol and titrated with alkali, phenolphthalein 1 Dingl. Polyt. Jour. 208. 305. 2 Jour. Soc. Ghem. Ind. 1896, 138. 3 Jacobsen’s Repertorium, 1884, i. 243. VII SMALL QUANTITIES OF FAT IN MINERAL OILS 223 being used as an indicator. Simultaneously the corresponding pure fat is treated in the same way. The number of cubic centimetres of alkali used being proportional to the amount of triglycerides, it is not necessary to know the titer of the alkali solution. A similar method had been proposed by Nitsche 1 before Lacombe. Although not so simple in practice it admits of a more extended use, not requiring, like the former, the composition of the neutral fat in the sample to be previously known. Nitsclie proceeds as follows:—10 grms. of the sample are saponi¬ fied, the soap acidulated, and the acid value of the mixture of fatty acids and unsaponifiable matter ascertained. Another 10 grms. of the sample are then saponified and exhausted with petroleum ether, as described p. 220, when the fatty acids of the neutral fat remain in the soap solution. On acidifying the latter the free fatty acids are recovered and their acid value is determined. The calculation is identical with that given above. Instead of calculating the acid values, the numbers of cubic centimetres of alkali used may be introduced in the formula given above. In that case the alkali need not be standardised. 3. Detection of Small Quantities of Fat in Mineral Oils Small quantities of neutral fatty oils in mineral oils may be de¬ termined by any of the gravimetric processes described above. It will, however, be found necessary, in order to check the results, to liberate the fatty acids from the soap solution, collect them on a filter, and ascertain their weight. If the quantity obtained suffices for the determination of their molecular weight, it is easy to calculate the amount of neutral fat (triglycerides) corresponding to the fatty acids. The safest method for detecting and estimating quantitatively small amounts of neutral fat is to boil 10-20 grms. (or more if neces¬ sary) of the sample with alcoholic potash, and to determine the amount of glycerol after separating the unsaponifiable oil and the fatty acids by one of the methods described above. The yield of glycerol multiplied by 10 will approximately furnish the percentage of fatty oil present. This is a more reliable method than to treat the saponified mass with mineral acid, wash until free from mineral acid, and determine the acid value of the resulting mass, the acid value of the original sample having been previously ascertained. Klimont 2 proposes the following test, by which it is claimed even 1 per cent of fatty oil may be detected :—Heat 15 grms. of the sample for one or two hours in a flask of 400 c.c. capacity with 100 c.c. of a 10 per cent alcoholic potash (not soda) solution; allow to cool, treat with about an equal volume of water, and filter through a wet filter. Then add to the filtrate a solution of calcium chloride, when the appearance of a flocculent precipitate of lime soap will 1 Dingl. Polyt. Jour. 251. 335. 3 Chem. Zeit. 1893, 546. 224 DETERMINATION OF UNSAPONIFIABLE MATTER CHAP- point to the presence of fatty oil. The method described may also be used for quantitative determinations. In that case the flask and the filter are well washed with hot water, the filtrate is exactly neutralised with hydrochloric acid, and, after complete cooling, extracted in a separating funnel with a small amount of petroleum ether. The aqueous layer is then concentrated to about 100 c.c. and precipitated with calcium chloride. The precipitate is filtered through a filter previously dried at 100° C., and washed, until dis¬ appearance of the reaction for chlorides, with the smallest possible amount of cold water, dried at 110° C. and weighed. If the amount of fat is required, the filter paper is incinerated in a crucible, and the weight of calcium oxide ascertained. This weight is multiplied by 0 - 774 — 3CaO : (C 3 H 5 ) 2 0 3 = 168 : 130—and the resulting number added to the amount of fatty anhydrides given by the difference between the weight of the lime soap (dried at 110° C.) and that of the lime left on ignition. This method is not suitable for the determination of larger amounts of fat, the lime soap easily forming lumps from which it is difficult to completely wash out the excess of calcium or potassium chloride. 4. Examination of the Unsaponifiable Matter The unsaponifiable substances isolated by one of the foregoing processes will be either liquid or solid at the ordinary temperature. Liquid substances may consist of mineral oils or tar oils, or resin oils, or of a mixture thereof. Solid unsaponifiable matter will mostly be composed of paraffin wax or cerasin (rarely of other hydrocarbons, as in waxes), and, notably in the case of waxes, of aliphatic alcohols and cholesterols. In manufactured products, as in “commercial stearine” or “ Turkey-red oil,” lactones or anhydrides occur which are not readily saponified, and therefore easily mistaken for unsaponifiable matter. Due care must therefore be taken in such cases to guard against error (chap. vi. “ Lactones,” p. 206). i. Liquid Unsaponifiable Substances Unsaponifiable oils frequently occur admixed with fatty oils in burning and lubricating oils. Mineral Oils. —Of mineral oils one may expect to find those obtained by the distillation of crude petroleum, shale, etc., viz. the fractions boiling from 250° to 300° C., specific gravity 0 - 855 to 0'900 (vulcan oils, mineral lubricating oils), and also the higher distillates, boiling from 300° to 350° C., specific gravity 0‘900 to 0'930. Con¬ sidered chemically, they consist nearly exclusively of aliphatic hydrocarbons belonging to the ethane and ethylene series. VII TAR OILS—RESIN OILS 225 Tar Oils. —The dead tar oils, boiling between 240° and 350° C., freed for the most part from naphthalene and anthracene by cooling, and from phenols by washing with caustic soda, are sometimes used for admixture with lubricating oils. The specific gravity of these tar oils is higher than that of water, and therefore they will sink in water. They consist of liquid hydrocarbons of the aromatic series, holding in solution small quantities of naphthalene, anthracene, and also of paraffinoid aliphatic hydrocarbons. Resin Oils. —These oils are obtained by subjecting colophony to dry (destructive) distillation. The distillate is fractioned by repeated distillation into a lighter—more volatile—portion, “ resin spirit,” and into a heavier—less volatile—portion, the fluorescent “ resin oil.” The specific gravity of resin oils ranges as a rule from 0'96 to 0 - 99 ; but resin oils having the specific gravity TOOl are also met with in commerce; they are therefore heavier than mineral oils and lighter than tar oils. Their chemical composition is not yet fully understood; they consist mostly of hydrocarbons related to the ter- penes, but contain also, according to the care exercised in distilling, larger or smaller quantities of resin acids and other oxygenated substances. Thus a sample examined by Allen and Thompson yielded 1'28 per cent of saponifiable matter. For the isolation of the latter proceed as in the examination of fats. Saponify the sample with alcoholic potash, boil down until the alcohol is driven off completely, dilute with water, and boil for half an hour, when the unsaponifiable constituents will float on the top as an oily layer. Draw off the aqueous layer, filter, and acidify with hydrochloric acid ; the resin acids will then separate in the shape of brown, viscid drops of char¬ acteristic smell. If the unsaponifiable portion of an oil has been found to contain resin oil (by one of the methods described below) it is necessary to determine the amount of resin acids in the soap solution if the quantity of resin oil in the sample be required. This is best done by Twitchell’s method (see p. 244). Discrimination between Mineral , Resin , and Tar Oils In the case of only one of these being present, the specific gravity may be used as a means of identifying it, as is shown by the follow¬ ing table :— Class of Oil. Specific Gravity. 0-850-0-920 0-960-1-001 Higher than 1 '01 Heavy mineral oils Resin oils Tar oils k>ut in the case of a mixture of the oils the specific gravity will be of but little value. According to Allen 1 a characteristic means of detecting the 1 Commercial Organic Analysis, ii. 81. Q 226 DETERMINATION OF UNSAPONIFIABLE MATTER CHAP. presence of hydrocarbons of the first two classes is furnished by their fluorescence. If the oil is distinctly fluorescent an admixture with hydrocarbon oils has undoubtedly taken place. If not, the sample should be shaken up with an equal volume of concentrated sulphuric acid, when fluorescence may appear ; sometimes dilution with ether may be found equally useful. It should, however, be borne in mind that fluorescence is not characteristic of hydrocarbon oils exclusively ; it is also exhibited by some fatty oils and commercial oleine (as palm oil oleine). On the other hand, absence of fluorescence is not always indicative of the absence of mineral oils, for the “ bloom ” shown by a mixture of fatty and mineral oils is frequently masked by the addition of small quantities of nitrobenzene or nitronaphthalene (see chap, xii. “ Lubricating Oils ”). Besides, there are many specimens of mineral oil in commerce that have been freed from the fluorescent constituents by suitable treatment. The fluorescence may be observed by dipping a glass rod in the sample of oil, and laying it on a table in front of a window, so that the oiled end of the rod shall project over the edge, and be seen against the dark background of the floor. Turbid oils must be filtered first. The fluorescence is not perceptible by gaslight. If this test, although not yielding decisive results for the reasons stated above, be resorted to, it will be best to examine the isolated unsaponifiable matter. For the detection of resin oils the following reactions and tests will be found useful :— 1. The Liebermann-Storch 1 Reaction. — Lieberrnann’s colour reaction for resin acids has been utilised by Storch for the detection of resin oils. 1 to 2 c.c. of the sample under examination are shaken with acetic anhydride at a gentle heat; after cooling, the acetic anhydride is drawn off by means of a pipette, and tested by adding one drop of concentrated sulphuric acid. If resin oil is present, a fine violet (fugitive) colour is immediately produced. This test is thoroughly reliable for the detection of resin oils in mineral oil as the writer can testify from his own experience. On applying this colour test to a number of oils and fats Morawski has obtained the following results :— Kind of Oil or Fat. Olive oil Sesame oil Hemp,seed oil Linseed oil Cotton seed oil Arachis oil Rape oil. Castor oil Cocoa nut oil . Colour produced by Acetic Anhydride and concentrated Sulphuric Acid. Light green Gradually becoming greenish-blue Green Green Green Reddish-brown Greenish-yellow Y ellowish Yellowish 1 Jour. Soc. Chem. Ind. 1888, 136. VII RESIN OILS 227 Kind of Oil or Pat. Palm nut oil . Beef tallow Bleached palm oil . Bone fat acids Whale stearine Olein Crude olive oil acids Herring oil Sunflower oil . Colour produced by Acetic Anhydride and concentrated Sulphuric Acid. Yellowish Y ellowish Brownish-yellow Brownish-yellow Brownish-yellow Brownish-yellow Light brown, afterwards dark green Cherry-red turning brownish-black Blue violet to blue These colourations, however, do not prevent the detection of resin oil. Morawski recommends the use of sulphuric acid of specific gravity T53 instead of concentrated acid; the same chemist has also shown that Holde’s 1 proposal to omit the addition of acetic anhydride is inadmissible. It should be borne in mind that cholesterol, which occurs in animal oils, also gives a very similar colour reaction, and its presence may lead to serious error if the isolated unsaponifiable matter be examined. In case, therefore, cholesterol 2 be suspected, a rapid method to prove the presence of resin oil would be to examine the mixed fatty acids, liberated from the soap solution, for resin acids (see below), which always accompany resin oils. A more com¬ plicated method would be to separate the cholesterol as benzoate. 2. Reward’s Test. —Resin oil (10 to 12 drops) treated with an¬ hydrous stannic chloride (1 drop) develops a characteristic beautiful violet colouration. Allen 3 prefers to use for this test stannic bromide, the reaction being much more delicate and more under control. The stannic bromide is prepared by allowing bromine, previously dried by shaking with concentrated sulphuric acid, to fall drop by drop on granulated tin contained in a dry flask immersed in cold water, until a colouration of the product indicates excess of bromine. The stannic bromide is then dissolved in carbon bisulphide, and a few drops of this reagent added to about 1 c.c. of the sample to be tested, pre¬ viously dissolved in carbon bisulphide. If resin oil be present in the sample the beautiful violet colouration already mentioned will appear. 3. The iodine absorption value has been proposed by Valenta 4 as a means of detecting the presence of resin oil, provided tar oils are absent. He finds that mineral oils absorb only 14 per cent of iodine, whilst resin oils gave iodine values of 43 to 48. The conclusions drawn from the iodine absorption should, however, be accepted with caution, since Demski and Morawski have found the iodine number 2T4, and Lewkowitsch 5 26'3 for samples of mineral oil. Older deter¬ minations of Mills 6 have even led to values as high as 35‘3 (calculated 1 Jour. Soc. Chem. Ind. 1888, 526. 2 Green fluorescence of the liquid, after the violet colour has disappeared, points to presence of isocholesterol. 3 Commercial Organic Analysis, ii. 463. 4 Jour. Soc. Chem. Ind. 1884, 644. 5 Ibid. 1892. 144. 6 Ibid. 1883. 436. 228 DETERMINATION OF UNSAPONIFIABLE MATTER CHAP. from the bromine absorption). Instead of the iodine number Klimont takes the bromine number, which he terms somewhat unnecessarily in the case of resin oils “ terebenthene number.” 4. Valenta 1 bases a process for detecting resin oils in presence of mineral oils on the difference of solubilities in glacial acetic acid at 50° C., a number of experiments on various mineral oils having shown that 100 grms. of glacial acetic acid dissolve 2‘6 to 6'5 grms. of mineral oil, whilst of resin oil 16'9 grms. are dissolved under the same conditions. The same relation is also expressed by stating that 10 c.c. of glacial acetic acid dissolve 0 - 2833 to 0‘6849 grm. of mineral oil and T7788 grms. of resin oil respectively. To perform Valenta?s test 2 c.c. of the unsaponifiable matter are mixed in a test-tube with 10 c.c. of glacial acetic acid, and the tube, loosely closed by a cork, is immersed in a water-bath for five minutes, the contents being repeatedly shaken during that time. The mixture is then filtered through a damp filter, and the middle portion of the filtrate collected. A portion of this is weighed off accurately, and the amount of acetic acid determined by titration with normal caustic soda. The differ¬ ence between the weight of the acid taken and the weight thus found is the amount of oil dissolved. Allen 2 points out that any resin acids present in the resin oil would alter the solubility, besides rendering inaccurate the alkalimetric determination of the acetic acid. He proposes, therefore, to neutralise the greater part of the acetic acid, dilute with water, and extract the resin oil by agitation with ether. 5. According to Demski and Morawski , 1 2 3 resin oils are miscible with acetone in all proportions, whereas mineral oils require several times their volume of that solvent to effect complete solution. If, therefore, the unsaponifiable oil mix completely with an equal volume of acetone, it is resin oil, or a resin oil containing but a small quantity of mineral oil; if, however, part of the oil remains undissolved, it is mineral oil, or a mixture of mineral oil with a small quantity of resin oil. Essentially the same test has been proposed by Wiederhold . 4 6. Similarly Finkener 5 recommends the employment of a mixture of one volume of chloroform and of ten volumes of alcohol of specific gravity CF8182 at 15‘5° C. Resin oils are soluble in ten volumes of this mixture, whereas mineral oil is insoluble in even 100 volumes. 7. Resin oils are dextro-rotatory, and therefore by a polariscopic examination of the unsaponifiable matter resin oil will readily be detected when present in large quantity. Valenta has examined a number of samples of resin oils in a Mitscherlich polarimeter, and found, for a length of 100 mm., rotations varying from 30° to 40° (dark specimens were previously clarified by means of charcoal). Demski and Morawski likewise found the rotation about 50°. Mineral oils are, as a rule, without action on the plane of polarised light, only one sample having been found to be dextro-rotatory, causing a deviation of 1'2°. As several vegetable oils have been found to be 1 Jour. Soc. Chem. Ind. 1884, 643. 2 Commercial Organic Analysis, ii. 465. 3 Jour. Soc. Chem. Ind. 1886, 179. 4 Jour. Pract. Chem. 1893 (47), 394. 5 Zeitsch. analyt. Cheviie, 1887, 652. VII SOLID UNSAPONIFIABLE SUBSTANCES 229 slightly optically active, it will be safest to examine the unsaponifiable oil after isolation. It should, however, be remembered that the hydrocarbons resulting from the destructive distillation of wool fat also exhibit optical activity (Lewkomtsch ). The determination of the specific gravity of the unsaponifiable oil enables us to differentiate between mineral and tar oils. If a mixture of both oils be suspected, the presence of tar oils may be detected by the aid of nitric acid, specific gravity B45. 1 Tar oils give a decided rise of temperature on mixing with the acid, whereas pure mineral oils will become but very slightly warmer. It is best to ascertain by a preliminary test whether a violent reaction takes place or not, the size of apparatus to be chosen depending on that. In the latter case 7'5 c.c. of the sample are placed in a graduated tube, cooled to 15° C., and 7’5 c.c. of nitric acid, spec. grav. T45, of the same temperature, added. The tube is then closed by a cork, provided with a thermometer, and the contents shaken thoroughly. The rise of temperature is then read off. If a strong reaction has been found to take place a larger strong-walled bottle must be employed, and the cork, besides holding the thermometer, must be fitted with an open glass tube, which may be closed by the finger whilst shaking. It will, however, be best in the latter case to employ small quantities, and to proceed as in Maumend’s temperature reaction test (see p. 291). The same reaction has been proposed by M c Ilhincy 2 for the detection of resin oil in a mixture of this oil with mineral oils. The methods employed for the quantitative determination of mixtures of mineral and resin oils will be detailed further on under the heading “Lubricating Oils,” chap. xii. p. 721. ii. Solid Unsaponifiable Substances The solid unsaponifiable constituents obtained in the course of analysis of fats and waxes may consist of aliphatic alcohols (cetyl alcohol, ceryl alcohol, myricyl alcohol, etc.) and cholesterols, and also, as in the case of waxes, small quantities of hydrocarbons may be found (see “Beeswax,” chap. xi. p. 657). Other unsaponifiable substances, not being constituents of the fats and waxes, falling under this head are paraffin and cerasin. The properties of paraffin and cerasin will be considered in chap, xii. under “ Candle Materials.” If the isolated solid unsaponifiable matter appears to be homo¬ geneous, i.e. consists of one chemical individual only, ultimate analysis will in the readiest way indicate its composition and nature. If, however, it consists of a mixture of several substances, separation may be effected by repeated recrystallisation from alcohol and ether, until chemically pure substances are obtained. Ultimate analysis may then be resorted to. 1 Brenken, Zeitsch. ccnalyt. Cliem. 1879, 546. 2 Jour. Soc. Cliem. Ind. 1895, 198. 230 DETERMINATION OF UNSAPONIFIABLE MATTER CHAP. The determination of the melting point of the unsaponifiable matter will not lead to decisive conclusions, as a glance at the following table, giving the melting points of some substances most likely to be met with, will show:— Unsaponifiable Substance. Cetyl alcohol Ceryl alcohol Myricyl alcohol Paraffin Cerasin Melting Point. °C. 50 79 85 from 38 to 82 from 61 to 78 If a mixture of several substances is under examination the indication of the melting point becomes valueless, all the more so, as small quantities of impurities depress the melting point of the substance considerably. Only in the case of a very high melting point having been obtained conclusions may be drawn as to the presence of cholesterols, which possess characteristic melting points. Alcohol. Melting Point. °C. Cholesterol ..... 145-146 Isocholesterol ..... 137-138 Phytosterol ..... 132-134 But it should be remembered that a mixture of the first two choles¬ terols melts below 100° C. The “ alcohols ” may be separated roughly from hydrocarbons by warm ethyl alcohol, in which the former are readily soluble, whilst the hydrocarbons are nearly insoluble. A better method, however, is afforded by boiling the unsaponi¬ fiable matter with an equal weight of acetic anhydride for about two hours in a flask connected with an inverted condenser. One of the three following will happen :— 1. The unsaponifiable substance dissolves completely, and remains dissolved on cooling. This points to the presence of aliphatic alcohols. 2. The unsaponifiable substance dissolves completely on boiling; on cooling a magma of crystals separates from the solution—presence of cholesterols or aliphatic alcohols , or of both. 3. The unsaponifiable matter does not intermix with the reagent, floating as an oily layer on the top of the hot acetic anhydride. On cooling, the undissolved portion solidifies again, and can be taken off easily. The undissolved part consists of paraffin or cerasin. In any case the acetic anhydride solution—in the last-mentioned case after separation from any undissolved oil whilst hot—is poured into water, when the acetates of cholesterols and aliphatic alcohols separate. They are boiled out with water until the wash-waters are no longer acid. The product thus obtained is dissolved in alcohol. The acetates of the cholesterols require large quantities of boiling alcohol for complete solution, whereas aliphatic alcohols dissolve VII CHOLESTEROLS 231 easily. If the former be present they will crystallise out on cooling, and may be further identified by their melting points, and iodine and saponification values. A complete separation, however, cannot be effected in this manner, as has been shown by Lewkowitsch. 1 In a mixture prepared from weighed quantities of cholesterol and cetyl alcohol he obtained in two experiments 60 and 69 per cent of the theoretical quantities of pure cholesterol acetate in the first crop of crystals, whilst the second crop of crystals—9 per cent—contained notable quantities of cetyl acetate. Again, on boiling the wool fat alcohols [consisting of cholesterol, isocholesterol, ceryl alcohol, and other unknown alcohols] with acetic anhydride, and trying to separate the acetates by crystallisation from alcohol, Lewkowitsch 2 isolated ceryl acetate in a crystalline state, whilst the acetates of the cholesterols formed with the acetates of the unknown alcohols oily substances from which no crystals could be obtained. The alcoholic solution of the aliphatic alcohols, respectively the alcoholic filtrate from the crystallised acetates, is treated with warm water, when the dissolved acetates separate as an oily layer. This may be solidified by cooling, separated from the water, and examined further, as indicated below. If solid hydrocarbons only have been found, their melting point will be found approximately the same as before treatment with acetic anhydride. On the other hand, the melting points of any acetates will materially differ from those of the original substances. Cholesterol, isoeholesterol, and phytosterol can be detected easily in the unsaponifiable substance by the reactions given above (p. 83). For the detection of phytosterol in oils compare chap. ix. p. 317. Cholesterol and isoeholesterol may be partially separated from the aliphatic alcohols either by boiling with acetic anhydride, and proceeding as described above, or by heating with 4 parts of benzoic anhydride 3 in a sealed tube to 200° C. for thirty hours (p. 84). In the latter case the product is boiled out repeatedly with alcohol, when cholesterol and isoeholesterol benzoates remain behind. If the benzoates have been prepared, separation of cholesterol from isoeholesterol may be effected by crystallising the mixed benzoates from ether. The cholesterol benzoate crystallises in hard rectangular plates, whereas the corresponding salt of isoeholesterol is obtained as a light crystalline powder, which can be separated from the former by decantation and elutriation. Cholesterol ben¬ zoate melts at 150°-151° C., isoeholesterol benzoate at 190°-191° C. By saponifying the benzoates with alcoholic potash and diluting with water, cholesterol and isoeholesterol are precipitated. They may be further identified by their qualitative reactions, melting points, and also by their iodine values. 4 1 Jour. Soc. Chem. Ind. 1892, 143. 2 Ibid. 192, 140, where line 22 from the bottom, left column, “acetates” should be read for “alcohols.” 3 Schulze, Berichte , 5. 1076 ; 6. 251 ; 7. 571 ; Jour.prakt. Chemie, 115. 163. 4 Lewkowitsch, Jour. Soc. Chem. Ind. 1892, 142. 232 DETERMINATION OF UNSAPONIFIABLE MATTER CHAP. In order to gain a further insight into the nature of the alcohols in the unsaponifiable matter, the increase in weight on boiling with acetic anhydride, the saponification values of their acetates, and the iodine absorp¬ tions of the alcohols themselves may be determined. Experiments made by the writer with mixtures prepared from pure specimens of cetyl alcohol and cholesterol have proved that theoretical values are obtained. The acetates are prepared, as described above, by boiling the alcohols with acetic anhydride. By operating with weighed quan¬ tities the increase in weight may be determined simultaneously ; by comparing the values thus obtained with those given in the following table, some conclusions may be drawn as to the composition of the alcohols. The isolated acetates may then be approximately resolved into their constituents by crystallisation from alcohol, and further, by fractional distillation, into several fractions, the saponification value of which may be determined by boiling with alcoholic potash, as in Kottstorfer’s process (p. 151). The acetates of the aliphatic alcohols are easily saponified ; the cholesteryl acetates require pro¬ longed boiling. On titrating back the excess of potash with standard acid the alcohols separate out again. They are precipitated completely by addition of water, collected on a filter, and their melting point and iodine value may then be ascertained. After separating the bulk of the cholesterols as far as possible, a definite iodine value will reveal the presence of aliphatic alcohols belonging to the allylic series. Some numbers are given in the following table which may serve as a guide in the examination of solid unsaponifiable matter :— Unsaponifiable Substances. Formula. Melting Point. °C. Iodine Absorption. Acetates. Increase in Weight on boiling with Acetic Anhydride. 4 Per cent. Saponific. Value. Melting Point. Paraffin wax CnH 2 n+2 38-82 3-9-4-0 1 0 Cetyl alcohol C m H m O ■ 50 0 197-5 22°-23° 17-2 Octodecyl alcohol Ql8 H 38 0 59 0 180-0 31° 15-5 Ceryl alcohol ^27^5^0 79 0 128-1 65° 10-6 Myricyl alcohol . ^30^62^ 85 0 1167 70° 9-6 Cholesterol C 2fi H 44 0 147 68'3 135-5 92° 11-3 Isocholesterol c 26 h 44 o 137-138 68-3 135-5 below 100° 11-3 Phytosterol c 26 h 44 o 132-134 68-3 135-5 11-3 Mixed alcohols from sperm oil r 25 "5-27 "5 64’6-65 - 8 2 161-190 Mixed alcohols from i neutral wool fat . • 36 160'9 Mixed alcohols from crude wool fat. 150 -6" 1 Determined in the writer’s laboratory. 2 The iodine values of the 5 fractions into which the mixed alcohols were resolved (Jour. Soc. Chem. Ind. 1892, 135) were the following:—1, 46"48 ; 2, 63 - 3 ; 3, 69'8 ; 4, 81-8 ; 5, 84-9. 3 Iodine absorption = 44'03 per cent. 4 Lewkowitsch, Jour. Soc. Clwn. Ind. 1896, 14. VII SEPARATION OF ALCOHOLS 233 Reliable methods of separating aliphatic alcohols from cholesterols are not yet available. Two methods have, however, been proposed which may lead to satisfactory results when fully worked out. Lewkoivitsch 1 bases a method on the conversion of aliphatic alcohols into fatty acids when heated with soda-lime or potash-lime, whereas cholesterols remain practically unchanged when so treated. Crucial experiments carried out with sperm oil alcohols and with cholesterol showed that on heating the former with soda-lime the bulk of the alcohols were converted into fatty acids, only 4 to 6 per cent of unsaponifiable matter (unchanged alcohol) being recovered ; whereas on treating cholesterol in the same manner 93 per cent of unchanged alcohol were recovered, only traces of fatty acids having been formed. Cochenhausen 2 proposes heating the mixture of aliphatic alcohols and cholesterols with cone, sulphuric acid, when the aliphatic alcohols yield alkyl sulphates, whereas the cholesterols are converted into hydrocarbons—“ cholesterones.” The alkyl sulphates can be isolated by means of their sodium salts, from which the original alcohol may be recovered by decomposition with boiling hydrochloric acid. If the unsaponifiable matter be heated with potash-lime, as in Hell’s or in A. and P. Buisine’s process, the volume of hydrogen gas may serve as a measure of the quantity of aliphatic alcohols present. Any solid hydrocarbons, as also cholesterols, that may be admixed with the alcohols are then obtained by extracting the powdered residue with ether in a Soxhlet extractor. The extracts are filtered, the ether distilled off, and the residue, if necessary, dissolved again in ether and filtered. The ether is then evaporated from the filtrate, and the hydrocarbons, etc., remaining are weighed (cp. “ Beeswax,” chap, xi. p. 664). In the examination of waxes a good deal of information is obtained by heating the wax directly with potash-lime, measuring the volume of hydrogen gas, and determining the hydrocarbons in the residue. The preliminary isolation of the unsaponifiable matter may thus be dispensed with. 1 Jour. Soc. Chem. hid. 1892, 13 ; 1896, 14. 2 Ibid. 1897, 447. CHAPTER VIII DETECTION AND QUANTITATIVE DETERMINATION OF RESIN IN FATS OR FATTY ACIDS i. Properties of Resin Common resin or colophony is the residue obtained from pine resin by heating in a still until all the moisture and the oil of turpentine is distilled off. Colophony forms a light yellow to dark brown trans¬ parent mass, the colour being modified by the manner in which the distillation has been conducted and by the temperature employed. It possesses vitreous lustre, and is very brittle, breaking with shallow conchoidal fracture. The specific gravity of colophony or common resin—or shortly “resin” 1 —varies from D045 to 1T08 at 15° C.; it is, therefore, considerably higher than that of fats. The melting point of resin also exceeds that of fats, some varieties possessing as high a melting point as 135° C. Resin softens at 70° C., and becomes semi-fluid in boiling water; it does not melt, however, to a clear liquid like fats or fatty acids. On warming, resin emits a pleasant terebinthinate odour; at a higher temperature, in contact with air, it burns with a dense yellow and sooty flame, sending forth a very characteristic smell. Subjected to destructive distillation resin spirit and resin oils are obtained as distillates, 2 and coke is left behind. Distilled in vacuo it yields a hydrocarbon (colophene 1) and an acid C 30 H 32 O o (isosylvic acid). 3 Insoluble in water, resin dissolves easily in alcohol, 1 part of resin requiring only 10 parts of 70 per cent alcohol for complete solution. The alcoholic solution has acid reaction, and its acidity can be ascertained by titration with alkali, using phenolphthalein as indi¬ cator. Resin is also soluble in methyl alcohol, amyl alcohol, ether, benzene, acetone, chloroform, carbon bisulphide, and oil of turpentine ; most of its constituents also dissolve in petroleum spirit. Solutions of resin do not leave a grease-spot on paper. 1 The spelling resin is here adopted throughout instead of “rosin ” often met with ; although the latter spelling would single out rosin or colophony as a special kind of resin, the salts of colophony are nevertheless spelt resinates. This inconsequence is- avoided here. 2 The aqueous distillate contains acetic acid, etc. 9 Bischoff and Nastvogel, Berichte , 1890, 1919 ; Jour. Soc. Ohem. Ind. 1890, 927. CHAP. VIII PROPERTIES OF RESIN 235 The following constants have been obtained by several chemists: Kind of Resin. Acid Value. Saponific. Value. Ether Value. Total Bromine Absorption Value. Bromine Substi¬ tution Value. Bromine Addition Value. Iodine Valued Observer. Austrian . 146-0 167T 21 1 116-8 v. Schmidt and Erban 2 Austrian . 130-4 146-8 16-4 109-6 Austrian, pale . 163-0 Kremel u Austrian, dark . 151-0 American . 173-0 >> English 169-0 >> Refined 181-0 178 *9 4 Mills 5 American . 154-1 183*6 29-5 92-4-93-5 Lewko- witsch 6 American . 159-0 174-7 15-7 ... 111-113 American . 161-4 178-9 17-5 113-114 >> American . 163-3 184-3 21-0 104-107 > 3 American . 164-3 194-3 30-0 62-64 >> American . 164-6 194-0 30-0 55-58 >3 Galipot 138-65 174-76 36-11 121-5-123-5 )! American (W.G.) 212-7 106-35 0 McIlhiney 1 American (E.) . 206-5 103-25 0 3 3 The high acid values, and especially the definite values (cp. column “ Ether Value ”), prove conclusively that colophony is not, as Maly maintains, an anhydride, viz. abietic anhydride, but consists chiefly of free acids and small quantities of an anhydride. The same conclusion has been arrived at by Perrenoud? According to this author colophony does not contain any abietic anhydride, but consists of a resin in which crystals of an acid are embedded. In the case of American colophony (the resin from the trunks of Pinus Strobus and Pinus Picea, and the resin from the root of Pinus sylvestris) the crystals are said to be abietic acid, whereas in the resin from “ galipot ” and from the trunk of Pinus sylvestris they are stated to consist of the isomeric pimaric acid. Both acids possess the same formula w(C 10 H 14 O); that of pimaric acid, as determined by the analysis of a crystalline ammonium salt, is most likely C 40 H 56 O 4 Both abietic and pimaric acid are optically active, and rotate the plane of polarised light to the left. The specific rotatory powers of abietic and pimaric acids are stated by Perrenoucl to be 48 and 56 respectively. 1 M c Ilhiney ( Jour. Soc. Chem. Ind. 1894, 668), working with different samples of resin, found an average iodine value of 155'5. The iodine number varied with the time allowed for absorption and with the excess of iodine used — just as in the case of oils (cp. 173). Therefore M°Ilhiney’s conclusion that the Hiibl process is useless in the examina¬ tion of resins is not justified. 2 Jour. Soc. Chem. Ind. 1889, 308. 3 Wagner’s Jahresbericht, 1886, 443. 127 4 Calculated from the bromine value 112*7 by multiplying by • 5 Jour. Soc. Chem. Ind. 1886, 222. 6 Ibid. 1893, 505, and unpublished experiments. 7 Chem. Zeit. 1885, 1590. 236 DETECTION AND DETERMINATION OF RESIN CHAP. The sylvic acid of some authors is in Liebermann’s 1 opinion identical with abietic acid. His researches, continued by Haller , 2 led to the result that pimaric acid is optically inactive. Vesterberg, 3 again, is of the opinion that three distinct acids are coexistent in “ galipot.” Looking at these partly contradictory views on the ultimate com¬ position of colophony, it is not surprising to find that Mfcch* rejects the formulae given for abietic, sylvic, and pimaric acids by the authors mentioned. He states that these acids are identical, and proposes for abietic acicl, the name he retains, the formula C 19 H 2s 0 2 , as found by numerous ultimate organic analyses and determinations of the molecu¬ lar weight of specimens of the acid prepared by different methods from various samples of colophony. Colophony also contains varying quantities of unsaponifiable matter, viz. hydrocarbons due to the partial breaking up of the acid on distilling pine resin. The following amounts of unsaponifiable matter have been found in commercial resins :— Origin. Unsaponifiable. Observer. French . American W.W. „ W.G. . „ N. . . „ N. . . „ M. . . Per Cent. 15-2 7- 34 5-00 9-00 8- 21 7-61 Jean Evans and Black > J > J Abietic acid, C 44 H 64 0 5 \Maly\ or w(C 10 H u O) [Perrenoud], or Ci 9 H 28 0 2 [Mach], is obtained in a pure state in the form of crystals by digesting 1 part of coarsely powdered colophony with 2 parts of 70 per cent alcohol at a temperature of 50°-60° C. It separates as a crystalline powder, which is purified by recrystallisation from 3 parts of boiling alcohol of the same concentration. Another method is to pass hydrochloric acid gas through an alcoholic solution of colophony, when abietic acid separates (Fluckiger, Jahresberichte der Chemie, 1867, 727). According to Mach, abietic acid occurs in colophony in varying amounts; some specimens contain 90 per cent of the crude acid, from others no acid could be isolated. On treating an alcoholic solution of colophony with water, a precipitate of impure abietic acid is obtained, which remains suspended in the liquid, forming with it an emulsion. On adding a dilute mineral acid and on warming, the resin separates in the form of globules on the side of the containing vessel, so that the clear liquid may be poured off. The resin thus obtained is at first very viscid, but it regains its former consistency by being boiled repeatedly with water, or by being heated to incipient fusion. In its pure state abietic acid crystallises in laminae or small 1 Berichte, 17. 1885. 2 Ibid. 18. 2167. • ! Ibid. 18. 3334. 4 Jour. Soc. Chem. Ind. 1893. 1044. VIII ABIETIC ACID 237 crystals, melting at 165° C.; they are soluble in alcohol, ether, benzene, and glacial acetic acid. Abietic acid is not converted into an anhy¬ dride on heating. Abietic acid is a dibasic acid. On warming colophony with dilute caustic alkalis, it is readily dissolved with formation of salts—resinates or pinates—that resemble in many respects the ordinary soaps. For that reason they are termed “resin soaps.” Thus the solutions of the alkali salts lather on being agitated, and the “ resin soaps ” are thrown up from their aqueous solutions by addition of concentrated alkali or of common salt. This separation, however, does not take place so readily and completely as in the case of the soaps made from fatty acids. Dilute mineral acids liberate the free resin acids from the resinates. Sodium resinate dissolves readily in alcohol, and also in ether con¬ taining alcohol; in pure ether, however, it is but sparingly soluble. According to experiments by Barfoed, 29 c.c. of ether dissolved within twenty-four hours 0'0239 grm., and 19 c.c. after eight days 0’041 grm. of sodium resinate. The solutions of the resinates of the alkali metals are precipitated by salts of the alkaline earths and heavy metals. On the solubility of some of these salts in alcohol and ether, methods of separation of the resin acids from the fatty acids are based. The zinc, copper, silver, and manganese resinates are soluble in ether, whereas calcium resinate is insoluble in this menstruum. As to manganese and lead and copper resinates cp. chap. xii. p. 785. In the quantitative analysis of a resin soap the acid is separated as free resin acid (abietic acid), and it is, therefore, necessary (as will be shown later on under “ Analysis of Soaps ”) for the proper calcu¬ lation of the composition of soap to convert the weight of the resin acids into the weight of the anhydrides. From the formulae for abietic acid, C 44 H 64 0 5 , and for the anhydride, C 44 H ci2 0 4 , it is easy to see that 100 parts of the free resin acid are equivalent to 97'32 1 2 parts of anhydride. Further information as to the composition of resin may be gained from a paper published by Jean? in which he shows that colophony contains besides its chief constituent, viz. abietic acid, two more resinoid substances (cp. above, Vesterberg’s opinion). The following observations are given in support of this view. On boiling colophony with twice the quantity of caustic soda of 15° BA (IT 16 specific gravity), a soap of gelatinous consistency separates from the alkaline solution on cooling. When the latter is poured off, and the gelatinous soap washed with caustic soda of 15° BA, the first resin acid, A, most likely abietic acid, is obtained by decomposing with a mineral acid. The alkaline solution contains the two other acids, B and C. Acid B 1 Pending a confirmation of Mach’s observations, these figures are still retained. 2 Ghevi. Neivs, 26. 207. 238 DETECTION AND DETERMINATION OF RESIN CHAP. is thrown out by acidulating with a mineral acid, acid C remaining dissolved. The three acids are differentiated by their solubilities in water and oil of turpentine. Acid C is soluble in water, whereas acids A and B are insoluble. Acids A and C are soluble in oil of turpentine, whereas B is insoluble in that solvent. All three acids dissolve easily in alcohol. The sodium resinate formed from acid A is sparingly soluble in cold water, but is easily dissolved by hot water, alcohol, and oil of turpentine. Lead acetate, magnesium, sulphate, and barium chloride precipitate the resinates of the corresponding metals. Barium resinate is soluble in ether. The sodium resinate formed from acid B is insoluble in oil of turpentine ; the barium resinate is incompletely precipitated by barium chloride solution. Acid C is prepared from the acid liquid, after acid B has been precipitated and separated by filtration. The filtrate is neutralised with caustic soda, evaporated to dryness, and the residue extracted with alcohol, when a shellac-like substance is obtained possessing a faint acid reaction. Copper and silver salts precipitate the aqueous solution of the acid. ii. Detection of Resin when admixed with Fats, Fatty Acids, and Waxes In mixtures of resin and neutral fats or oils the former, if present in considerable quantity, may be recognised by its peculiar smell and characteristic taste. The determination of the specific gravity may also be usefully employed; presence of resin will be indicated by a higher specific gravity than the normal one. The rapid detection of resin in neutral fats or waxes may be based on the solubility of resin in alcohol and solutions of sodium car¬ bonate. On warming the suspected sample with 70 per cent alcohol the resin only will be dissolved. The alcoholic solution is then diluted with water, when in presence of resin a precipitate is obtained which is collected after warming, and, if necessary, after addition of a mineral acid. The substance thus obtained may be then identified as resin by its appearance, consistency, odour, etc. Barfoed warms the sample with a dilute alcoholic solution of sodium carbonate, prepared by dissolving 1 part of soda crystals (or 0'37 parts of soda ash) in 3 parts of water, and then adding 7 parts of 30 per cent alcohol (2 measures of 93 per cent alcohol and 5 measures of water), when the resin only is stated to be dissolved. Its separation is effected as described already. Bodiger 1 boils 100 grms. of the sample with 7 to 8 grms. of potassium carbonate and 80 to 100 grms. of water in a flask for a quarter of an hour, cools to 50° C., and then shakes vigorously with •> 1 Chem. Zeit. 5. 498. VIII DETECTION OF RESIN 239 petroleum ether. The aqueous layer, holding in solution any resin soap present, is then drawn off and diluted with hot water. Excess of common salt is next added, the solution slightly acidulated and boiled, when an oily layer of resin acid mixed with a little fat and petroleum ether will he obtained. The latter may be driven off by heating the separated resin acid to 100° C. The methods described here can only be used for the qualitative detection; for, on the one hand, the fats, although insoluble in water and in dilute alcohol, are dissolved, to a slight extent, by the resin soaps formed ; and, on the other hand, a petroleum ether solution of fat is apt to dissolve appreciable quantities of resin soap. The most reliable process is the following: Saponify the sample under examination with alcoholic potash and liberate the fatty acids together with the resin acids by acidulating. Then examine the mixed acids by the Liebermann-Storch reaction (p. 226). According to Morawski the Liebermann-Storch reaction is in many cases suitable for the detection of resin acids. The writer recom¬ mends this method as thoroughly trustworthy in every case. To perform this test, the fatty acids are dissolved in acetic anhydride at a gentle heat and the solution cooled. Sulphuric acid of T53 sp. gr. 1 is then carefully allowed to flow into the solution, when the presence of the minutest quantity of resin acid will be indicated by the appearance of a reddish-violet colouration ; if the solution be too warm, this colour will disappear almost immediately, changing into a brownish-yellow. In any case, the colour disappears quickly. Fatty acids do not produce the violet colour, but it should be remem¬ bered that cholesterol, which gives a similar reaction with acetic anhydride and sulphuric acid, might be present amongst the mixed acids. In the latter case the cholesterol must be removed previous to the liberation of the mixed fatty acids by shaking out the soap solution with ether or petroleum ether. This reaction may be also used for the detection of resin in beeswax. Numerous other methods have been proposed, and are still being proposed, for the same purpose (by Sutherland , Vohl, Gottlieb , Barfoed, Jean, Renard, Cornette), but as they are not reliable they are omitted here. For the isolation of the resin it will be found best to use the method described under vi. iii. Quantitative Determination of Resin in Neutral Fats In mixtures of neutral fats with resin—as linseed oil and resin— the writer determines approximately the resin by titrating an accu¬ rately weighed quantity of the sample dissolved in ether-alcohol 1 Sulphuric acid of 1'53 sp. gr. contaius 62'53 per cent of S0 4 H 2 ; it is prepared by mixing 347 c.c. of cone, sulphuric acid with 37'5 c.c. of water. 240 DETECTION AND DETERMINATION OF RESIN CHAP. with standard alkali, using phenolphthalein as an indicator. The combining weight adopted for resin is 346, and the amount of free fatty acids in the oil is, of course, neglected, being, as a rule, very small compared with the acid value corresponding to the resin. Experiments carried out on mixtures of linseed and cotton seed oils with resin gave very accurate results. If greater accuracy be desired, the resin acids are isolated together with the mixed fatty acids, and examined as described under the following head :— iv. Quantitative Determination of Resin Acids in Admixture with Fatty Acids 1. Barfoed’s Method. —The mixed fatty acids—say 10 grms.— are neutralised with warm dilute caustic soda (one measure of caustic soda, specific gravity IT, in six measures of water), avoiding an excess of caustic soda [preferably by titrating with the caustic soda solution, phenolphthalein being used as an indicator]. The solution is then evaporated on the water-bath to complete dryness, the residue finely powdered and dried in a stoppered weighing-bottle at 100° C., until the weight remains constant; the drying sometimes takes several days. The dry powder is then divided into two parts; one part (a) is used for the determination of both resin and fatty acids ; in the second part ( b ) the resin acids only are estimated. (a) This part is dissolved in hot water and acidulated by addi¬ tion of hydrochloric acid. After standing for twenty-four hours the separated acids are transferred to a weighed filter, washed until all traces of the mineral acid have been removed, dried at 100° C. and weighed. ( b) The second portion of the dried residue is placed in a stoppered graduated cylinder (preferably a Muter tube), and 5 to 10 c.c. of absolute alcohol for every grm. of substance added. The volume having been read off carefully, the stopper is tied on to the neck of the cylinder, and the cylinder immersed in a water-bath and heated for some time to 80° C., when all the resin soap and part of the fatty acid soap will pass into solution. On cooling, however, part of the dissolved fatty acid soap will separate and a contraction may take place; this is made up to the former volume with alcohol, and then five times the volume of ether, thoroughly freed from alcohol and water, is added. The contents of the cylinder are agitated at intervals for several hours, and then allowed to stand for twenty-four to forty-eight hours at the ordinary temperature. The resin soap is then dissolved completely, the fatty acid soap having been precipitated and settled out so that an accurately measured portion of the solution may be withdrawn. The resin acids dis¬ solved in. the latter may be determined by first evaporating the ether, dissolving the residue in water, and estimating the resin as VIII DETERMINATION OF RESIN 241 described in (a). The quantity found is calculated to the total volume of the ether-alcohol solution, and thus the percentage of resin acids obtained. By subtracting ( b ) from (a) the amount of fatty acids in the mixture is found. The undissolved fatty acid soap, as obtained in (b), may be collected on a filter and further examined. This method yields reliable results only when oleic acid is almost wholly absent (which is very rarely the case); great care must also be taken to employ absolutely anhydrous alcohol and anhydrous ether, or else the results will be seriously vitiated by the presence of fatty acid in the isolated resin acid. Experiments made by Barfoed on the solubilities of sodium resinate and sodium oleate in the alcohol ether mixture as described above, are recorded in the following short table :— Soluble in parts of Alcohol-Ether Solution. 7-9 935-0 One part of Sodium resinate Sodium oleate Ether alone cannot be used, sodium resinate being but sparingly soluble in it. Barfoed’s method cannot be recommended; it has been fully described here, as process 2 (d) (see below) is based on it. 2. Gladding’s Method. —This method is based on the solubility of silver resinate in ether, and the almost complete insolubility of the silver salts of the fatty acids in this solvent. It was proposed origin¬ ally by Gladding ; later on several modifications have been suggested by various authors. (a) Gladding’s Original Method }—About 0-5 grm. of the mixed resin and fatty acids are dissolved in 40 c.c. of 90 per cent alcohol in a stoppered graduated cylinder, by warming on the water-bath. A drop of phenolphthalein is then added, and a concentrated solution of alco¬ holic caustic potash dropped in carefully until the solution has just acquired a permanent pink colour. A gentle heat may be applied in order to keep the soap dissolved. The solution is then allowed to cool, and made up with ether to exactly 200 c.c. 1 grm. of finely powdered silver nitrate is next added, and the contents of the cylinder shaken vigorously for about twenty minutes, when the precipitate, consisting of the silver salts of fatty acids, will coagulate and settle out, leaving the supernatant liquid clear. An accurately measured quantity—conveniently 100 c.c., being half of the quantity employed —is then run off into a separating funnel, and agitated again with a small quantity of powdered silver nitrate in order to ensure the complete precipitation of the fatty acids. Should there be any precipitate it will be best to reject the assay altogether and to start afresh. The ethereal solution is then shaken vigorously with 40 c.c. of dilute hydrochloric acid (1 volume of hydrochloric acid, specific gravity IT2, and two volumes of water), and the precipitated silver chloride removed together with the acid liquid. The ethereal layer. 1 Chem. News, 14. 159. R 242 DETECTION AND DETERMINATION OE RESIN chap. holding the liberated resin acid in solution, is washed free from mineral acid, transferred to a weighed flask, the ether evaporated, and the residue weighed. The quantity found multiplied by 2 gives the amount of resin acid in the sample. Gladding , supported by two experiments only, makes a correction for the small quantity of silver oleate dissolved, by subtracting from the weight obtained 0'002359 grm. for each 10 c.c. of the ethereal liquid. In order to eliminate the uncertainty of the correction, Alder Wright and Thomson 1 have determined the solubilities of the silver salts of different fatty acids. They are given in the following table, to which a few figures, found by the writer, 2 have been added :— Kind of Acid, Solubility of Patty Acids (as Silver Salts) in 10 c.c. of Alcoholic Ether. Author. Minimum. Maximum. Mean. Pure stearic . Grm. 0-0016 Grm. 0-0008 Grm. 0-00116 Wright and Thompson >> J ) Pure oleic 0-00058 0-00054 0-00056 Lewkowitsch 0-0015 0-0009 0-0012 Wright and Thompson )> >> • ’ Nearly pure palmitic 0-01094 0-01090 0-01092 Lewkowitsch 0-0030 0-0028 0-00291 Wright and Thompson Cotton seed oil 0-0034 0-0020 0-00269 Castor oil 0-0062 0-0049 0-00539 Cocoa nut oil (acids dried on water- bath) . 0-00175 0-0012 0-00148 Cocoa nut oil (acids dried over vitriol) 0-0023 0-0019 0-00211 Stearic and oleic, in nearly equal pro¬ portions 0-0022 0-0018 0-00191 Stearic and cotton seed oil acid, in nearly equal pro¬ portions 0 00255 Oleic and cotton seed oil acid, in nearly equal pro¬ portions 0-00245 Stearic and cocoa nut oil acid (water- bath) in nearly equal proportions 0-00234 Oleic and cocoa nut oil acid (water- bath) in nearly equal proportions 0-00256 > 5 No account is taken in Gladding’s original method of the volume of the precipitated silver salts, and with regard to the solubility of the silver salts of the fatty acids in ether, even granting the accuracy 1 Chem. News, 53. 165. 2 Jour. Soc. Chem. Ind. 1893, 503. VIII DETERMINATION OF RESIN 243 of the corrections given in the preceding table, the proof is still wanting that these figures hold good for a mixture of those silver salts with varying proportions of silver resinates. Lewkowitsch has examined a number of resin soaps by this method, and although the solubility of the silver salts of the fatty acids was determined separ¬ ately, altogether unreliable results were obtained. The method must therefore be rejected. (b) Hiibl and Stadler's Modification of Gladding’s Process. — These chemists dissolve about 1 grm. of the mixed resin and fatty acids in about 20 c.c. of alcohol by warming in a stoppered bottle on the water-bath, and exactly neutralise the acids with caustic potash, using phenolphthalein as an indicator. The soap solution is then transferred to a beaker, made up with water to about 200 c.c., and precipitated with silver nitrate solution. The silver salts are filtered of % protected from sunlight, dried at 100 ' C. in an oven, and exhausted in a Soxhlet extractor b} 1, means of dry ether. The ethereal solution should be yellow or light brown, but not dark brown; it is filtered, if necessary, into a separating funnel, the dissolved resin acids are isolated by hydrochloric acid, as already described, and weighed. A correction for any dissolved aliphatic silver salts is not recom¬ mended. This modification obviates the errors attaching to Gladding’s original method by avoiding the measuring of an ethereal solution, so extremely liable to losses by evaporation. Lewkowitsch, 1 however, who has tried this method, could not get satisfactory results, the values obtained being mostly too low. It appeared that reduction of the silver salts (especially when the percentage of resin in the soap was high) took place in almost all cases, in some going so far as to yield an ethereal solution free from silver. Besides, the solu¬ bility of the silver salts of the aliphatic acids seemed to be greater than in the preceding method. (c) Grittner and Szilazi’s Modification of Gladding’s Process. —These chemists dissolve the sodium salts of the mixed fatty acids in 80 per cent alcohol, neutralise, if necessary, with ammonia, and precipitate with a 10 per cent alcoholic solution of calcium nitrate. Calcium palmitate and stearate are precipitated completely, calcium oleate for the most part, whilst calcium resinate remains in solution. On adding silver nitrate to the filtrate and diluting it strongly, the silver salts are precipitated; these are filtered off and treated with ether according to Cladding's directions. The correction to be made, according to Grittner and Szilazi, is 0‘016 grm. for every 10 c.c. of ether used. The figures which the authors give in their original paper 2 speak certainly in favour of the exactness of the method, but a series of experiments carried out by the writer 3 gave unsatisfactory results. (d) Allen’s Modification of Gladding’s Process.—Allen 4 proposes to combine Gladding’s original method with Barfoed’s. This is done by 1 Jour. Soc. Chem. Ind. 1893, 503. 2 Chem. Zeit. 10. 325. 3 Jour - Soc - Chem. Ind. 1893, 503. 4 Thorpe, Diet, of Applied Chem. iii. 55. 244 DETECTION AND DETERMINATION OF RESIN CHAl’. exhausting the dried sodium salts of the mixed fatty and resin acids with ether-alcohol (whereby the resinates are dissolved easily along with part of the oleate, whereas palmitate and stearate remain behind), converting the dissolved salts into their corresponding silver salts, and treating the latter with ether. Allen states that the com¬ bination of the two methods yields very satisfactory results, without, however, supporting this statement by figures. Since, however, this combined process is based on the same principle as Grittner and Szilazi’s, and since Allen 1 himself declares that this process has been wholly superseded by TwitchelVs (see below), it need not be discussed further. 3. Twitehell’s Method. 1 2 —This method is based on the property of aliphatic acids of being converted into their ethylic ethers when acted upon by hydrochloric acid gas in their alcoholic solution, whereas colophony is said to undergo practically no change under the same treatment, abietic acid separating from the solution (see p. 236). The analysis is carried out as follows :— 2 to 3 grms. of the mixed fatty and resin acids are weighed off' accurately, dissolved in a flask in ten times their volume of absolute alcohol (90 per cent alcohol must not be used, as the conversion of fatty acids into ethers is not complete in that case), and a current of dry hydrochloric acid gas passed through, the flask being cooled by immersion in cold water. The gas is rapidly absorbed at first, and after about forty-five minutes, when gas is noticed to escape unab- soi'bed, the operation is finished. To ensure complete etherification the flask is allowed to stand for an hour, during which time the ethylic ethers and the resin acids separate on the top as an oily layer. The contents of the flask are then diluted with five times their volume of water, and boiled until the aqueous solution has become clear. From this stage the analysis may be carried out either (a) volu- metrically or (b) gravimetrically. (a) The Volumetric Analysis. —The contents of the flask are trans¬ ferred to a separating funnel, and the flask rinsed out several times with ether. After vigorous shaking the acid layer is run off, and the remaining ethereal solution, containing the ethylic ethers and the resin acids, washed with water until the last trace of hydrochloric acid is removed. 50 c.c. of alcohol are then added, and the solution titrated with standard caustic potash or soda, using phenolphthalein as an indicator. The resin acids combine at once with the alkali, whereas the ethylic ethers remain practically unaltered. Adopting as the combining equivalent for resin 346, the number of c.c. of normal alkali used multiplied by 0’346 will give the amount of resin in the sample. 3 1 Jour. Soc. Chem. Ind. 1893, 508 ; Analyst, 1895, 7. 2 Jour. Soc. Chem. Ind. 1891, 804. 3 Wilson [Jour. Soc. Chem. Ind. 1891, 952) shortens the volumetric process by dis¬ solving the contents of the flask in alcohol direct, thus omitting the washing with water. The solution is then titrated with alkali until neutral to methylorange, this amount of alkali being of course neglected. Phenolphthalein is then added, and again titrated until pink ; the second amount of standard alkali is calculated to resin. VIII TWITCHELL’S METHOD 245 (b) The Gravimetric Method .—The contents of the flask are mixed with a little petroleum ether, boiling below 80° C., and transferred to a separating funnel, the flask being washed out with the same solvent. The petroleum ether layer should measure about 50 c.c. After shaking, the acid solution is run oft’, and the petroleum ether layer washed once with water, and then treated in the funnel with 50 c.c. of a solution containing 0'5 grm. of KOH and 5 c.c. of alcohol. The ethylic ethers dissolved in the petroleum ether will then be found to float on the top, the resin acids being dissolved by the slightly alkaline solution. The soap solution is then run off, decom¬ posed with hydrochloric acid, and the separated resin acids collected as such, or preferably dissolved in ether and isolated after evaporating the ether. The residue, dried and weighed, gives the amount of resin in the sample. Of all the methods proposed hitherto for the estimation of resin acids in mixtures with fatty acids, that recommended by Twitchell yields the best results, and should therefore be used to the exclusion of the methods described before. The results, however, must not be considered as absolutely correct; they are only approximate, as Lew- kowitscli 1 has shown by an exhaustive examination of both the volumetric and gravimetric processes. The mean combining weight of different brands of commercial resin varying within considerable limits (cp. p. 235), an uncertainty adheres to the volumetric analysis, of which the gravimetric analysis is free. Under the action of the hydrochloric acid the resin appears to undergo some destruction 2 with the formation of acids of lower molecular weight, since the volumetric analysis gave, as a rule, too high results. In the gravimetric process, again, some of these secondary products pass into the aqueous solution without being dis¬ solved by the petroleum ether. By a subsequent extraction with ether, part of the dissolved substances may be recovered, but even then the results of the gravimetric analysis were found too low. Of course, the unsaponifiable oils occurring in resin (p. 236) remain in the petroleum ether solution and thus escape being weighed. But even this cannot wholly account for the great deficiency. The subjoined tables, giving the analysis of mixtures of oleic 1 Jour. Soc. Ghem. Ind. 1893, 504. 2 The results given in table p. 247 are confirmed by several experiments made since by Evans and Black, as shewn by the following table :— Weight of Resin. Resin calculated from Titration. Loss. Grms. Orms. Per cent. 2-0968 2-054 2-00 2-4723 2-45 0-90 2-035 0-93 2-03 0-69 2-115 1-14 246 DETECTION AND DETERMINATION OF RESIN CHAP. acid and resin acids of ascertained combining weight, will confirm the writer’s critical remarks :— e K £ -

vO *>» 00 00 ^ ^ iO O (M rt< O “ rf CO CO 00 r-H o O (M VO ^ 05 O (M 05 03 y First Alkali Wash. Extracted by Second Alkali Wash. Extracted by Ether. Total. No. Per cent. Per cent. Per cent. Per cent. 2 19-69 19-46 0T15 1-045 20-62 2 • 19-69 18-44 0-074 0-822 19-34 3 21-45 19-14 0-105 0-3615 19-607 3 21-45 19-19 0-061 0-2839 19-54 4 24-66 21-72 0-179 1-203 23-102 4 24-66 22-29 0-239 1-01 23 -54 5 30-31 25-75 0-019 2-41 28-18 5 30-31 26-93 0-085 0-72 27 -73 6 39-81 34-96 1-296 1-567 37-80 6 39-81 34-596 0-190 1-12 bo'91 Evans and Black 1 try to vindicate Twitchell’s method as correct. But as they, like Twitchell himself, experimented only with mixtures containing about 40 per cent of resin acid, for which percentage, curiously enough, the best results are obtained, their experiments cannot refute the writer’s results. In case the resin admixed originally with the fat contained notable quantities of (unsaponifiable) resin oils, the latter are deter¬ mined as described under the following heading :— v. Quantitative Determination of Resin Acids in Admixture with Fats (or Fatty Acids) and Unsaponifiable Matter If a mixture of resin acids, fat, and unsaponifiable matter be under examination, the sample is saponified by boiling with alcoholic potash, and the alcohol driven off by prolonged boiling after diluting with water. The aqueous solution of soap is then transferred to a separat¬ ing funnel—regardless of any undissolved unsaponifiable matter—and shaken out with petroleum ether, whereby the unsaponifiable matter is separated from the fat and resin (cp. p. 219). The soap solution gives, on treatment with a mineral acid, a mixture of fatty and resin acids, which are separated by Twitchell’s process. By using Twitchell’s volumetric method the separation of the un¬ saponifiable matter may be avoided by the following procedure: 2 —The 2 .Tour. Soc. (Mem. Ind. 1891, 804. 1 Amer. (Mem. Jour. 1895, 59. 250 DETECTION AND DETERMINATION OF RESIN CHAP. VIII mixture is saponified with alcoholic potash, and the resin acids, fatt}^ acids, and unsaponifiable matter isolated by acidulating. If a mixture of the acids and unsaponifiable matter be given at the outset, the saponification, of course, is unnecessary. 2 grms. of the mixed acids and unsaponifiable matter are weighed off accurately, titrated with normal caustic soda or potash, and the number of c.c., used until neutrality to phenolphthalein is reached, noted. Another 2 grms. are treated with hydrochloric acid gas, as described above, and titrated with normal alkali. If a be the number of c.c. used in the first experiment, and b the number found in the second experiment, then we shall find, adopting as the com¬ bining weight for resin 346, and for fatty acids (palmitic, stearic, oleic) 275— 1. Weight of resin acids = a x O'346 2. Weight of fatty acids = (a - b) x 0'275 3. Weight of unsaponifiable = 100 - [ax 0'346 + (a - b) x 0*275]. The accuracy of the result will, of course, largely depend on the correctness of the assumed combining weights 346 and 275. vi. Separation of Resin from Fatty Matter Separation of resin acids from fatty acids is effected by passing the mixture of resin and fatty acids through the etherification process described under Twitchell’s method. We then have a mixture of free acids and ethers, and after titration, as e.g. in the volumetric process, there results a mixture of resin soap and ethyl ethers of the fatty acids. Now if the alcohol is distilled off and the remaining mixture is treated with water, the soap is dissolved, leaving the ethers floating on the surface of the soap solution. The two layers are separated, and the soap solution, after washing with common ether to remove the last traces of dissolved ethylic ethers, yields on acidulating the resin acid. The ethylic ethers are saponified by means of caustic alkalis, and the fatty acids separated in the usual manner. Both the resin and the fatty acids may then be examined separately. CHAPTER IX APPLICATION OF PHYSICAL AND CHEMICAL METHODS TO THE SYSTEMATIC EXAMINATION OF FATTY OILS AND LIQUID WAXES A SUBDIVISION of the liquid fats into several classes may be con¬ veniently based on their chemical properties, as will be shown further on. But it should be borne in mind that the distinctions between the members of the different classes are not always very clearly marked, and much less so the differences between the members of one and the same class. For this reason the detection of every individual oil, when in admixture with the others, nay, even the detection of two oils when mixed, is often a very difficult task. As most liquid fats consist chiefly of nearly the same glycerides, a quantitative separation of the individual oils contained in a mixture is altogether out of the question. But though we have no definite quantitative methods as in inorganic analysis, yet, by adopting a systematic plan of examination, we can in the majority of cases decide— (1) Of what kind of oil a sample consists, and (2) Whether it is a pure or an adulterated specimen. If a mixture of but two oils be under examination, it is, as a rule, possible to detect the presence of either oil qualitatively. Frequently it will even be feasible to determine quantitatively the proportions of the mixed oils. A mixture of three or more fatty oils is often met with. In such cases commercial analysis will not always lead to a satisfactory result; still, in most cases it will be possible to identify at least one or two of the individual oils in the mixture. The most important problem required to be solved by commercial analysis is, whether a sample is pure or sophisticated. Adulteration of fatty oils with the unsaponifiable oils (tar oils, resin oils, mineral oils) will be the easiest to detect. Of the fatty oils themselves only those will be used as adulterants that are lower in price than the oil to be adulterated, the object of sophistication being evidently to sell a cheaper article at a higher 252 EXAMINATION OF FATTY OILS AND LIQUID WAXES chap. price. Hence a price list of the different kinds of oils will materially assist the analyst in fixing his attention on the oils lower in the scale of prices than the sample under examination. The following list, arranged in the order of their commercial value, may be found useful. It should, however, be remembered that these prices are subject to wide fluctuations from year to year, causing, e.g. cotton seed oil and linseed oil to change places :— Almond oil 11. Sperm oil 12. Olive oil 13. Neat’s foot oil 14. Lard oil 15. Castor oil 16. Cod liver oil 17. Arctic sperm oil 18. Arachis oil 19. Poppy seed oil 20. Sesam6 oil Seal oil Rape oil Linseed oil Cotton seed oil—maize oil Whale oil Cod oil Japan fish oil Mineral oil Resin oil It will also greatly facilitate the examination of a totally unknown mixture of oils to learn its price, as this alone will tend to exclude a number of the more costly oils from the scope of the analysis. In the following pages a systematic plan for the commercial analysis of oils will be adopted, based principally on the application of the general methods described in the preceding chapters. It must, however, be left to the analyst to select the methods and tests best adapted to each special case. 1 If a known oil be under examination, it will be best to consult first the description of that oil and the tables of constants given in chap. xi. Before entering on the general methods applicable to the system¬ atic examination, we may cursorily glance at the so-called Organoleptic Methods These comprise the odour and taste of the oil. Some adulterants, such as resin and mineral oil, will frequently be detected by the odour. The odour becomes more distinct on heating the oil or, as proposed by Clarke, on mixing it with sulphuric acid. Olive oil, lard oil, rape oil, cameline oil, and especially the oils from marine animals, possess a characteristic smell. To be able to discriminate by smell, however, requires a good deal of practical experience, more frequently possessed in a high degree by dealers in oils than by analytical chemists. The recognition of certain oils by taste is more difficult still, and yet the taste alone is in many cases the only criterion to determine the value of particular brands of oils that are pure in the sense of being wholly 1 Cp. “Olive Oil,” chap. xi. p. 451 ; “ Lard,” chap. xi. p. 563 ; “ Butter fat,” chap. xi. p. 601. IX BY PHYSICAL AND CHEMICAL METHODS 253 free from adulteration. Thus taste alone can discriminate between the fine Tuscan olive oils and the more inferior oils of South-Eastern Italy. Physical Methods The physical methods applied to the examination of oils have been detailed in chap. v.; they may be referred to as affording valuable information. A comparison of the results supplied by the examina¬ tion of the sample with the numbers registered in the following tables will be found useful. The specific gravity, solidifying point, and the melting and solidifying points of the fatty acids furnish, as a rule, the most valuable and useful criteria, but the optical methods also, wherever the necessary apparatus is at hand, should be employed, combining, as they do in many cases, rapidity of observation with certainty of result. In special cases the determination of the viscosity will prove of some assistance. The behaviour of oils with solvents will in many cases serve as a valuable confirmation of indications furnished by other tests. Several attempts at a systematic classification of oils, based on the solubility in some solvents, have been made, but hitherto no general rule has been established. Other physical properties will be referred to for the sake of completeness, although their usefulness is either doubtful or has not yet been fully established. Chemical Methods Most of the chemical methods adopted in testing have been exhaustively described in chap. vi. The so-called quantitative reactions enumerated there, and further the chemical tests described below, in short, those tests that are practised on the fatty substance itself will naturally be of the greatest importance. Those reactions that are caused by foreign matters admixed with the oils, as small quantities of resins, colouring matters, etc., give, as a rule, less decisive results, the quantity and sometimes also the nature of those impurities varying considerably in different specimens of the same oil owing to the different processes adopted for their prepara¬ tion and purification. All the so-called colour reactions fall under this category. In some special cases, however, the colour reactions give definite indications. The following tests and methods will be considered under this head :— (1) Ela'idin Test. (2) Sulphur Chloride Test. (3) Oxygen Absorption Test. (4) Thermal Reactions. (5) Quantitative Reactions. (6) Qualitative Tests. 254 EXAMINATION OF FATTY OILS AND LIQUID WAXES CHA1>. A. Application of Physical Methods in the Identification of Individual Oils and Recognition of their Purity i. Specific Gravities of Fatty Oils and Liquid Waxes If it be simply a question of identifying two oils by comjiarison of their specific gravities, Bonny 1 proposes to colour the one sample - say by alcanna and allow a drop of the other sample to slowly fall into it. If the two oils are identical the drop will float in the oil • if it falls down or floats on the surface, its specific gravity will be greater or smaller. We subjoin the following two tables, due to Allen, and a table con¬ taining a number of values found in the Paris Municipal Laboratory ■ the latter has been supplemented by some determinations of other obseivers. Allens first table (in which one or two corrections have been made as suggested by more recent determinations) contains the principal oils arranged according to their specific gravity; there are added, for the sake of comparison, the specific gravities of some fatty acids and hydrocarbons. It has not been thought necessary to give a complete list of. specific gravities, as they will be found in chap. xi. under each individual oil. 1 Dingl . Polyt . Jour . 174. 78. [Table Table of Specific Gravities of Fatty Oils ancl Liquid Waxes at 15°-16 IX SPECIFIC GRAVITIES 255 5s o *£> 52 a 1-2 ~ ° o o o 0,8 o g . o 2 ^ "3 o fi ri r—« I 'f< CD c3 L ^ O ^ ct ci 5 ^ « C r-( 52 —h 'Tr b n) ^ 5 p>. JP ® o ,i2 t I * 3 a <5 r~ J ing oils 0-9250 0-3 + 20 Yellow ) > + 12 Origin unknown Pearmain ,, ,, (crude) + 16 to 3 samples + 17 Temp. 22° C. ,, ,, (refined) + 17 to 6 samples ,, + 23 Temp. 22° C. Jean Sesame oil 0-9237 2 + 18 0-9210 4-1 + 17-5 Bombay J J + 17 + 17 Pale > > + 45 Bruyn & van Leent + 13 to 5 samples Pearmain + 17 Temp. +22°C. Jean Beechnut oil . 0-9206 + 16-5 0-9206 + 18 > > Colza oil 0-9147 4-6 + 18 + 17-5 + 18 > > 1 0-9142 0-6 + 16-5 French ,, 1 0-9142 1-0 + 18-5 French ,, 0-9142 1-3 + 16-0 + 18-5 ,, 1 0-9142 ro + 17-5 Cawnpore ,, Rape oil 0-9156 11-6 + 17-5 + 18 India . +15 to > > I group Rape oil . + 16 + 16 to 8 samples Pearmain 1 1 + 20 Temp. 22° C. 1 Ravison oil -b 20 to 2 samples ,, + 24 1 Cabbage seed oil Jean J Castor oil 6-3 + 43 1 1-4 + 46 Commercial > > 2-0 + 43-5 Pharmaceutical > > >> > i + 37 Javan Bruyn & van Leent Castor oil + 40 Pharmaceutical > > Deering & 0-9637 to + 41 to Indian oils 0-9642 + 42-5 Redwood + 39 to 8 samples Pearmain + 42 Temp. 22° C. Peach kernel oil + 7-5 to 2 samples Pearmain Non-dry- + 11-5 Temp. 22° C. Jean ing oils Almond oil 0-9177 + 6 + 6 0-9180 + 6 + 6 Pharmaceutical J J 0-9198 3-3 + 5 + 6 J > Bruyn & + 7 van Leent + 8 to 8 samples Pearmain + 10-5 Temp. 22° C. Jean Arachis oil 0-9167 + 3-5 + 3-5 Rufisque 0-9154 + 3-5 + 4-5 J > 0-9187 4-4 + 4 + 4-5 Gambia ) > 0-9176 8 + 5 + 6-5 Boulam > > ” ” : 0-9164 1-7 + 3-5 + 4 + 3-5 La Felicie Bruyn & van Leenl + 5 to 8 samples Pearmain + 7 Temp. 22° C. 1 The purification had been effected by shaking the oils with alcohol to remove the free fatty acids. 266 EXAMINATION OF FATTY OILS AND LIQUID WAXES CHAP. Kind of Oil. Specific Gravity. Acid¬ ity. Deviations of the Oil. Degrees + or -. Remarks. Observer. Class of Oil. Commrl. Purified. 1 Tea seed oil . + 8-0 Temp. 22° C. Pearmain Non-dry- Olive oil + 0 to + 2 20 samples Jean ing oils 99 9: • + 9 very old 9 9 99 99 • + 0 to + 1-5 Bruyn & van Leent 99 99 • + 1-0 to + 3-5 105 samples Temp. 22° C. Pearmain Sperm oil 0-8780 5 - 17 ’5 -17 Jean Liquid 9 9 9 9 • Arctic sperm oil (Bottlenose oil) 0-883 3-3 -12-0 9 9 Pearmain waxes + 50 Lard oil + 5-5 Jean Terrestrial 9 9 9 9 • - 0 to + 1-0 6 samples Temp. 22° C. Pearmain animal oils Sheep’s foot oil Horse’s foot oil 0-9184 0 -12 0 Jean 9 9 9 9 9 9 9 9 0-9205 0-9202 1 -13 -13 9 9 9 9 9 9 Neat’s foot oil 0-9225 - 6 0-9163 - 4 9 9 9 9 9 9 9 9 - 3-5 - 3 American French 9 9 9 9 Pearmain 9 9 9 9 - lto -3-0 2 samples Tallow oil 0-9210 -15 Jean 9 9 9 9 -1-0 to -5-0 2 samples Temp. 22° C. Pearmain Resin oil 0-9732 + 78 Jean The purification had been effected by shaking the oils with alcohol to remove the free fatty acids. The following table, collated by the writer, shows that gross adulterations may be detected by means of the oleo - refracto- meter:— [Table IX OLEO-REFRACTOMETER 267 Kind of Oil. Adulterated with Deviation of the Oil. Observer. Class of Oil. Linseed oil 20 % of resin oil Degrees + or - + 67-0 Jean Drying oils 20 % of hemp seed oil . + 47-0 >> Walnut oil linseed oil + 40-5 >> Whale oil resin oil ... + 60-0 Jean Blubber oil Almond oil 20 % of poppy seed oil . + 14-0 Jean Non-drying oils > J J 1 poppy seed oil + 16-0 >> cotton seed oil + 9'0 )) Olive oil . 20 % of cotton seed oil . + 13-0 10 % of poppy seed oil . + 6-5 5 J J J 20 / ,, ,, ,, + 10-0 J f J J J > 10 % of cotton seed oil . + 3-0 > J 20% „ „ „ . + 5-0 >> If a mixture of two oils be given, and the deviations of the individual oils be known, it is possible to calculate the proportions of the two oils in the mixture from the deviation observed in the oleo- refractometer, as Jean has shown. Let m be the quantity of the one oil having the deviation d, and n the quantity of the other having the deviation d', and let D be the deviation of the mixture, then we have the two equations— n+m= 100 _ IO 7 . -j-'y iwf l+ mi d =D from which n and m may be calculated. The deviations obtained by means of Zeiss’s refractometer will be given in chap. xi. (c) Polarimetric Examination From the remarks made on this subject in chap. v. p. 120, and the table given there, it will be evident that very little information of a discriminative nature can be gained from the polarimetric examina¬ tion of the oils. Croton and castor oils only have distinct rotatory powers, these having shown, on examination in a saccharimeter, a rotation to the right of + 43° and + 40'7° respectively. A strong deviation to the right may reveal the presence of resin oils, and for this reason the polarimetric examination is of great help in the examination of linseed oil (chap. xi. p. 343). 268 EXAMINATION OF FATTY OILS AND LIQUID WAXES chai>. iv. Viscosimetrie Examination The viscosimetrie examination of fatty oils does not lead to results of a discriminative nature; sperm oil, a liquid wax, alone is very characteristic in this respect (chap. xi. p. 646). The application in the examination of butter will be described (chap. xi. p. 630). The following tables give the viscosities of sperm oil and a number of fatty oils, some of which are largely used for lubricating purposes :— Kind of Oil. Number of Seconds required at Observer. 15-5° C. 49° C. 82° C. Sperm oil 47 30-5 25-75 J. Veitch Wilson 1 Olive oil. 92 37-75 28-25 Lard oil . 96 38 28-5 Rape oil . 108 41-25 30 Neat’s foot oil. 112 40-25 29-25 Tallow oil 143 37 25 Engine tallow. Solid 41 26-5 »3 Kind of Oil. Specific Gravity at 15-5“ C. Number of Seconds required at Observer. 15-5° C. 50° C. 100° C. Sperm oil . 0-881 80 47 38 Allen 2 Seal oil (pale) 0-924 131 56 43 Northern whale oil 0-931 186 65 46 Menhaden oil 0-932 172 40 Sesamd oil . 0-921 168 65 50 Arachis oil. 0-922 180 64 Cotton seed oil (refined) 0-925 180 62 40 3 3 Niger seed oil 0-927 176 59 43 33 Olive oil 0-916 187 62 43 Rape oil 0-915 261 80 45 Castor oil . 0-965 2420 330 60 3 3 Kind of Oil. Specific Gravity at 17-5° C. Viscosity (Engler) at Observer. 20° C. 50° C. 100 ° c. 150° C. Rape oil, crude 0-920 9-03 4-0 1-78 1-34 Kiinkler 3 Rape oil, refined 0-911 11-88 4-9 2-05 1-40 3 3 Olive oil. 0-914 10-3 3-78 1-80 >3 Castor oil 0-963 16-46 3-01 Linseed oil 0-930 6-36 3-2 1-76 33 Tallow . 0-951 5-19 2-50 1 *73 33 Neat’s foot oil. 0-916 11-63 4-44 1-92 33 1 Allen, Com. Organ. AnaZys. ii. 195 (1886). 2 Ibid. 3 Jour. Sqc. Chem. Ind. 1890, 198 ; Bingl. Polyt. Jour. 1889, 282. IX SOLUBILITY 269 Kind of Oil. Number of Seconds required (Redwood) at Observer. 60° F. 70° F. 80° F. 90° F. 100° F. 120° F. 150° F. 200° F. 250° F. Rape oil, refined 540 405 326 360 213-5 147 95-5 58-5 43-25 Redwood Sperm oil . 177 136 113 90 80-5 60-5 49 42 34-75 Neat’s foot oil . 470 366 280 219-25 174-75 126 75-5 50-4 44 Beef tallow - 54-75 40 ” Water 25-5 ” v. The Difference in the Solubility of Oils as a means of Identification In some cases it is possible to differentiate oils by means of their solubilities in alcohol and acetic acid. Fatty oils are nearly insoluble, or very sparingly soluble in alcohol, with the exception of castor oil, croton oil, and olive kernel oil. These three oils dissolve easily even in cold alcohol. Oils containing a large proportion of glycerides of the lower fatty acids, such as cocoa nut oil, palm nut oil [butter fat], porpoise oil, are, comparatively, easily soluble in alcohol. The same property is possessed by oils consisting to a large extent of glycerides of linolic and linolenic acids, as e.g. linseed oil. The following table, due to Girard, gives the solubilities of some oils in 1000 grms. of absolute alcohol at 15° C. :— 1000 Grms. of Absolute Alcohol dissolve at 15° C. Kind of Oil. Gmis. Rape oil ...... 15 Colza oil ...... 20 Mustard seed oil ..... 27 Hazelnut oil . . . . .33 Olive oil ...... 36 Almond oil . . . . .39 Sesame oil . . . . .41 Apricot kernel oil . . . .43 Walnut oil . . . . .44 Beechnut oil . . . . .44 Poppy seed oil . . . . . .47 Hemp seed oil . . . . . .53 Cotton seed oil . . . . . .64 Arachis oil . . . . .66 Linseed oil . . . . .70 Cameline oil . . . . .78 Castor oil is sharply distinguished from all other oils by its com¬ parative insolubility in petroleum ether and paraffin oil. (Compare p. 425.) 270 EXAMINATION OF FATTY OILS AND LIQUID WAXES chap. Valenta 1 classifies the fatty oils and solid fats (the latter are also considered here so as to avoid repetition) into three groups according to their solubility in acetic acid. The test is carried out by thoroughly mixing equal volumes of oil and glacial acetic acid of specific gravity 1'0562 in a test-tube, and warming the mixture if no solution has taken place. ls£ Class. —Completely soluble at the ordinary temperature (14° to 20° C.) are : Olive kernel oil and castor oil. 2nd Class. —Completely soluble or nearly so at temperatures ranging from 23° C. up to the boiling point of glacial acetic acid : Palm oil, laurel oil, nutmeg butter, cocoa nut oil, palm nut oil, bassia oil, olive oil, cacao butter, sesam6 oil, pumpkin seed oil, almond oil, cotton seed oil, arachis oil, apricot kernel oil, beef tallow, bone fat (American), beef stearine, and cod liver oil. 3rd Class. —Not completely dissolved—even at the boiling point of glacial acetic acid—are oils obtained from seeds of the Cruciferse : Rape seed oil, mustard seed oil, hedge mustard oil. The oils belonging to the second class may be further differen¬ tiated, by gradually warming the sample with an equal volume of glacial acetic acid in a test-tube with frequent shaking until complete solution is effected. A thermometer is then introduced into the liquid, and the temperature noted at which turbidity appears. According to Valenta , the fats of the second class may be subdivided into two groups : the one embracing the following fats—palm oil, laurel oil, nutmeg butter, cocoa nut oil, palm nut oil, and bassia oil; the remain¬ ing oils of that class forming the second group. The temperatures found by Valenta are given in the following table. Allen’s 2 observations, however, are not in agreement with those published by Valenta. Hurst , 3 who has also studied Valenta’s test, finds the method unreliable—a conclusion in which Ellwood 4 and also Thomson and Ballantyne 4 concur. In the following table the results of Valenta’s, Allen’s, and Hurst’s experiments are placed side by side:— 1 Jour. Soc. Chem. Ind. 1884, 643. 2 Ibid. 1886, 69 ; 282. 3 Ibid. 1887, 22. 4 Ibid. 1891, 233. [Table IX SOLUBILITY IN ACETIC ACID 271 Solubility of Fatty Oils and Solid Fats in Acetic Acid Kind of Oil or Pat. Temperature of Turbidity for equal Volumes of Fat and Glacial Acetic Acid, spec. gray. l - 0562. Valenta. Allen. Hurst. °C. °C. °C. Palm oil 23 83 Laurel oil . 26-27 40 Nutmeg butter . 27 39 Cocoa nut oil 40 7-5 Palm nut oil 48 32 Bassia oil . 64-5 Yellow olive oil . 111 \ Green olive oil (of second expression) 85 28, 47, 62, 65, 71, 76 Cacao butter 105 Insoluble Sesame oil . 107 87 Pumpkin seed oil 108 Almond oil, sweet 110 Cotton seed oil . 110 90 53, 63 Niger seed oil 49 Linseed oil. 57-74 36, 36, 36, 41, 41 Arachis oil . 112 87 72, 92 Apricot kernel oil 114 Beef tallow. 95 Bone fat (American) . 90-95 Tallow stearine (M. P. 55’8°) 114 Cod liver oil 101 79 65 Menhaden oil 64 Shark liver oil . 105 95 Porpoise oil .... 40 84, 74, 74 Whale oil . 38, 86 48, 53, 65, 71 Seal oil ... 72 34 Lard ..... 96-5 Butter fat . 61-5 Oleomargarine .... 96-5 Lard oil ... 69, 73, 76 Tallow oil . 47 Neat’s foot oil 102 65, 85 Arctic sperm oil . 102 Sperm oil. 98-103 85 The following table, comprising oils belonging to Valenta’s third class, more clearly demonstrates the same point:— Kind of Oil. Specific Gravity at 15'5° C. (water at I5‘5 = l). Observer. Valenta. Allen. Hurst. Rape oil 0-9145 Insoluble Insoluble 88 Rape oil 0-9168 86 Rape oil 0-9132 85 Rape oil 73 Colza oil 0-9162 99 Colza oil 0-9131 97 Colza oil 94 Colza oil 94 Colza oil 0-9132 >> ) J 82 272 EXAMINATION OF FATTY OILS AND LIQUID WAXES chap. Thomson and Ballantyne, experimenting with acetic acids of different strengths, arrived at the following numbers :— Temperature of Turbidity with Glacial Free Acid Acetic Acid of calculated Oleic Acid. Sp. Gr. Sp. Gr. Sp. Gr. 1-0542. 1-0552. 1-0562. Per cent. °C. °C. °C. Olive oil (Gioja). 9-42 65 80 91 Same oil, freed from free acid none 87 Olive oil (Syrian) 23-88 42 Olive oil i 5-19 | 3-86 78 85 96 100 li’l Arachis oil (commercial) . 6-20 76 92 112 Arachis oil (French, refined) 0-62 96 114 | Not completely dissolved f 2-43 110 | Not completely 1 Rape oil dissolved \ *• 4-54 105 Linseed oil. 0-76 61 78 90 Linseed oil (Baltic) 3-74 42 59 71 Linseed oil (East India) 0-79 57 Linseed oil (River Plate) 1-21 56 The indications of the last table prove that the amount of free fatty acid in fats considerably influences the indications of Valenta’s test, a fact which has also been brought out by Hurst's experiments. Notwithstanding these serious discrepancies, Valenta’s test may, in conjunction with other tests, afford some valuable hints in the examination of an oil. According to Bach, 1 reliable results are obtained by examining the behaviour of the mixed fatty acids prepared from the oils under exam¬ ination. The solvent recommended by Bach is identical with the alcohol-acetic acid mixture proposed by David. The solvent (prepared as described p. 197) is treated with 1 to 2 grms. of stearic acid, and the clear supernatant liquor only is used. One operates as follows :— Place 1 c.c. of the mixed fatty acids in a test-tube divided into T \j- cubic centimetres, add 15 c.c. of the alcohol-acetic acid mixture, agitate well, and allow to stand at a temperature of 15° C. The mixed acids from pure olive oil give a clear solution, whereas the mixed cotton seed oil fatty acids remain undissolved. However, on dissolving the latter, by gently warming the mixture and allowing to stand, a white gelatinous mass is obtained when the temperature falls to 15° C. The fatty acids from sesamA and arachis oils behave similarly. Sunflower oil acids dis¬ solve in the mixture, but give on standing at 15° C. a granular precipi¬ tate. Bape oil acids do not dissolve at all, but float on the top as an oily layer. Castor oil acids behave like olive oil acids. Olive oil con¬ taining 25 per cent of cotton seed or sesame oil deposits a granular 1 Pharm. Centralhalle, 1883, 159. IX SOLUBILITY IN ACETIC ACID 372 precipitate. Smaller quantities of the admixed oils, however, cannot be detected. In the case of rape oil having been used as an adulterant the limit is 50 per cent. The following modification of Valenta’s test has been proposed by Jean : 1 —Place 3 c.c. of the fat in a graduated test-tube of 1 cm. diameter, and immerse the tube in water of 50° C. Remove, by means of a finely drawn-out pipette, so much oil that exactly 3 c.c. remain at the temperature of 50° C. Next introduce, by means of a graduated pipette, 3 c.c. of acetic acid, specific gravity 1-0565 at 15° C. (prepared from glacial acetic acid by adding the requisite amount of water), measuring off the acid at 22° C., warm the contents of the tube in the water for a few minutes, then cork well, and agitate thoroughly. Allow the mixture to settle out at 50° C. until two distinct layers are noticeable, and read off the volume of the undissolved acetic acid. The volume of the acid dissolved in the fat is then easily calculated. Jean has found the following proportions for the oils and fats given in the table :— Acetic Acid (sp. gr. 1-0565 at Kind of Oil or Pat. 15° C.) dissolved. Per cent. Arachis oil (Boulam) . . 41-65 Aracliis oil (Gambia) . . 43-66 Colza oil . . 30-00 Ravison oil . 33-30 Almond oil, sweet . 33-00 Olive oil . 35-00 Walnut oil . 36-60 Cameline oil . . 36-60 Castor oil . 100-00 Maize oil . 10070 Beechnut oil . . 53-3 Poppy seed oil (Indies) . 63-3 Poppy seed oil, French . 43-3 Neat’s foot oil . 43-3 Sheep’s foot oil 36-66 Horse fat . 30-08 Lard . . 26-66 Veal tallow . 26-66 Butter, 9 samples of different origin . . 63 -33 2 Cotton seed stearine . . 40-00 Butterine . 31-60 Margarine 26-66 Palm oil . 100-00 Cocoa nut oil . . 100-00 For further information the reader is referred to the article on “ Butter Fat,” chapter xi. p. 619. The behaviour of some fats with carbolic acid has been studied by 1 Corps gras industriels, 1892 [19], 4. 2 Besides these nine samples, all of which gave 63‘33 per cent, two abnormal butters were examined, giving 58*7 and 73'0 respectively. T 274 EXAMINATION OF FATTY OILS AND LIQUID WAXES chap. Salzer, 1 after the same solvent had been utilised by Crook for the dis¬ crimination of butter fat (p. 618) from other animal fats. The test is carried out by adding the oil drop by drop to 10 c.c. of phenol (of the specified strength) contained in a graduated cylinder with constant shaking, until the turbidity no longer disappears. In liquefied phenol of more than 91 per cent most oils seem to be equally soluble, im¬ portant differences appearing with the employment of weaker solutions. In the following table Salzer’s results are reproduced :— Dissolved are by 10 c.c. of Phenol of Kind of Oil. 91 per cent. 87 per cent. 83 per cent. C.C. C.C. C.C, Almond oil. f Min. 2-5 1 Max. 3-5 Olive oil. j Min. 2 - 0 \ Max. 3‘0 Rape oil. Linseed oil. 4 3 Poppy seed oil .... 6'8 Min. 2 Croton oil . 16 8-5 4-0 Arachis oil. 11-5 4-3 0-8 Cotton seed oil . 10-5 5-5 1-0 Sesame oil. 10 3-8 0-8 1 part of olive oil +1 pt. of poppy seed oil 4-8 3partsofoliveoil + lpt. of poppy seed oil 3'4 3 parts of olive oil +1 pt. of aracliis oil 3'0 1 part of olive oil +1 pt. of arachis oil. 3'8 9 parts of olive oil +1 part of rape oil . 2-1 ( Distinct Croton oil ..... • •• 4 turbidity ( with 2'3 1 Salzer claims to be able to detect adulteration with mineral oil in almond oil, cod liver oil, etc. The figures recorded in the table are not of the kind to inspire great confidence in this method ; moreover, free fatty acids increase the solubility. Salzer’s method can, therefore, at best only serve as a preliminary test. vi. Other Physical Properties Several other physical methods have been proposed for the examination of liquid fats, but hitherto they have been of little use for practical purposes, and need only be enumerated for the sake of completeness. Tomlinson and also HallwacJis , state that every kind of oil furnishes characteristic figures when allowed to fall on the surface of water so as to spread out into a thin film. These figures—the so-called cohesion figures —are said to be sufficiently characteristic of each 1 Arch. d. Pharmac. 227. 433. IX COHESION FIGURES—ELECTRICAL CONDUCTIVITY 275 particular oil to serve for identification or detection of adulterations. Without going any further into the subject, it may be said that definite results can only be obtained by a very long and exhaustive series of experiments, without, however, yielding as satisfactory results as other physical methods. According to Girard, the method of examining the cohesion figures may be of some use for the detection of castor and croton oils, these two oils rendering the surface of the water strongly iridescent. 1 Wynter Blyth has studied the figures or patterns which drops of various fats assume under certain conditions, and states that each fat appears to have its own distinctive pattern and can be identified by this pattern alone. But as every alteration of the experimental condition modifies more or less the pattern, it is evident that this “ pattern test ” must be considered as only of use in the hands of an observer with special experience in this branch of examination. The electrical conductivity was made use of by Rousseau and afterwards by Palmieri in the examination of olive oil, but this method has not met with any extended application in the commercial analysis of oils. Recently, however, the electrical conductivity has been proposed again by Herlant (chap. v. p. 121) for detecting adulteration in butter (see chap. xi. p. 630). The following numbers have been obtained by Herlant for the oils enumerated in the table. A few values for butter and margarine are added here, as this chemist believes that the method will be useful in the examination of butter. The third and fourth columns are added in order to show that the conductivity stands in direct relation to the refractive index and critical temperature :— Specific Conductivity at 18° C. Refractive Index. Critical Oil or Fat. Degrees in Leiss’s Butvro-refractometer Temperature of Dissolution. at 35° C. °C. Cotton seed . 0-008629 63 115-116 Arachis I. . . 0-008700 58-25 115-116 „ lb • • Sesam6 0-008741 60-25 123 0-008779 63 120-5 Olive .... 0-009927 57 "25 123 Butter 1 . . . 0-006457 ] l 44-5 ,, 2 . . . ,, 3 . . . 0-006500 0-006507 h 98-103 1 45 45 ,, 4 . . . Margarine 1 . . 0-007010 1 [ 48 0-008221 52-5 „ 2 . . „ 3 . . 0-008459 0-008472 [ 122-123 i 56-5 54 „ 4 . . 0-008489 1 [ 58 1 The “pattern test” has recently been applied to butter fat and margarine (J, Hoffmann, Chem. Zeit. 1897, 572) without any useful result. 276 EXAMINATION OF FATTY OILS AND LIQUID WAXES chap. vii. Critical Temperature of Dissolution There have not yet been collected sufficient data to allow definite conclusions to be drawn as to the value of this constant (cp. chap. v. p. 122) in the examination and discrimination of oils. The observations obtained hitherto are collated in the following table :— Critical Temperatures obtained with Alcohol, Specific Gravity (P8195, at 15*5° C. Substance. No. of Samples. °C. Observer. Japanese fish oil . . 108 Crismer and Motteu 1 Cotton seed oil . . 115-116 Herlant 2 Colza oil ... . 132-135 Crismer and Motteu Sesame oil ... 120-5 Herlant Arachis oil . . . 1 115-116 ,, Arachis oil ... 2 123 > > Olive oil ... . 123 Crismer and Motteu Animal oil ... 120 Sheep’s foot oil . Neat’s foot oil . . 102 95 Lard oil .... 104 > > Cocoa nut oil . 71-75 Crismer 3 Cacao butter . . . 126 ” Butter. 14 98-102 Crismer Butter. 4 98-103 Herlant Margarine .... 122-126 Crismer Carnaiiba wax . . 154 Crismer Beeswax .... from various sources 129-133 Ozolterit .... 175 Crismer Paraffin wax . . . according to constitution and melting points 140-160 Oil of turpentine 14 ” By using more dilute alcohol higher values are obtained for the critical temperatures, as will be seen from the following table, due to Asb6th i :— 1 Jour. Soc. Chem. Ind. 1896, 300. 3 Cp. cliap. v. p. 123. 2 Ibid. 1896, 562. 4 Chem. Zeit. 1896, 685. IX CLASSIFICATION OF OILS 277 Critical Temperatures with Alcohol of 90 per cent by volume, Specific Gravity 08332 No. of Samples. Becomes perfectly'clear at °C. Commences to become cloudy at °C. Commences to form 2 layers at °C. Critical Temperature. °C. Butter 1 . . 7 119-134 117-5-131 113-5-120 111-5-115 Fresh Butter 1 124 121 116 115 Margarine 2 . 2 ' 140-151 138-148 135-144-5 133-5-142 If absolute alcohol be employed, an open tube may be used. The results obtained for butter will be given in chap. xi. under “ Butter.” B. Application of Chemical Methods in the Identification of Individual Oils and Becognition of their Purity The fixed oils may be subdivided according to their chemical behaviour into the following four large classes :— i. Liquid Waxes. —These oils, occurring solely in marine animals, contain but small quantities of glycerides, if any, and consist chiefly of compound ethers of fatty acids of monovalent alcohols. They yield, therefore, on saponification large quantities of “ unsaponifiable matter.” They absorb but little oxygen from the atmosphere, do not dry, and yield elaidin. ii. Fish Oils, Liver Oils, and Blubber Oils . 3 —These oils are liquid glycerides occurring in marine animals. They absorb large quantities of oxygen, without, however, drying into varnishes; they yield but little or no elaidin. iii. Drying 1 Oils. —The drying oils consist for the most part of glycerides of linolic and linolenic acids. They absorb large quantities of oxygen, and also of iodine, and dry into varnishes on exposure to the air in a thin layer. The drying oils do not yield elaidin. iv. Non-drying Oils. —These oils, containing large proportions of olein, do not dry on exposure to the atmosphere, at any rate not at the ordinary temperature, absorb but little oxygen, assimilate less iodine than the drying oils, and yield elaidin. As an intermediate class between classes iii. and iv. there may be interposed the Semi-drying Oils (see p. 366). i. Liquid Waxes The liquid waxes—of which but two true representatives are yet known, viz. sperm oil and Arctic sperm oil—are readily distinguished 1 Cp. more detailed results, chap. xi. p. 628. 2 Chap. xii. p. 679. 3 These three groups of oils, as also the liquid waxes, are comprised in German under the term “ Thrane,” the English equivalent of which— 111 train oils ”—only denotes blubber oils. To avoid confusion, the term “ train ” oil is not used in this work. 278 EXAMINATION OF FATTY OILS AND LIQUID WAXES chap. from all other fixed oils by their yielding a large proportion of unsaponifiable matter. Whereas most oils yield 95 per cent of fatty acids on saponification, the remainder forming glycerol, the liquid waxes contain but 60 to 65 per cent of fatty acids, the remaining 40 to 35 per cent consisting of monovalent aliphatic alcohols. The pro¬ portion of glycerides, and consequently of glycerol, in the liquid waxes is but very small (cp. chap. xi. p. 643). Their physical properties also admit of their being readily dis¬ tinguished from other oils, their specific gravities being very low, and their viscosity much less influenced by variation of temperature than is the case with other oils. The following table gives a few constants of the two liquid waxes:— Name of Oil. Source. Fatty Acids. Per cent. Sperm oil . Arctic sperm oil (or bottle- nose oil), doegling oil . . . 61-58-5 60-65 Mono¬ valent Alco¬ hols. Sponific. Value. Iodine Value. Specific Gravity. Per cent. At 15°-16° C. At 98°-99° C. 39-41-5 123-4-147-4 84-3 0-875-0-884 0-S22-0-S30 40-35 123-0-134 SO-4 0-S76-0-881 0-823-0-82S Dolphin oil (from Delphinus globiceps ; spec. grav. 0922 at 15°-16° C.) contains large quantities of waxes, but will be classed, on account of its proportion of glycerides, amongst blubber oils. ii. Fish Oils, Liver Oils, and Blubber Oils The fish, liver, and blubber oils are easily distinguishable from other liquid fats by their fishy smell and taste. According to some chemists they are further characterised by the intense colourations they give with caustic soda, sulphuric acid, nitric acid, and phosphoric acid. The phosphoric acid test was proposed by Schaedler as the most characteristic, enabling one to detect even OT per cent of these oils. The best results were stated to be obtained by warming five measures of the oil under examination with one volume of syrupy phosphoric acid, when all oils belonging to this class, both in their pure state or in admixture with other oils, were said to show intensely red, reddish-brown, or brownish-black colourations. Holde 1 states that the phosphoric acid test is uncertain, for on the one hand resin oils pro¬ duce red colourations with this acid, and on the other hand distinct 1 Jour. Soc. Chem. Ind. 1890. 419. IX CLASSIFICATION OF OILS 279 colourations only appear when large quantities of marine animal oils are present in other oils. The writer, 1 after extensive examination of these colour reactions, has come to the conclusion that they are not exclusively characteristic of these oils, but are due to impurities which can be removed by proper modes of refining. Thus, a sample of horses’ foot oil (not refined), prepared in the laboratory, gave, with the above-mentioned reagents, reactions which might be considered as typical of marine animal oils. Also old samples of linseed and cotton seed oils behaved similarly. The same conclusion holds good of the chlorine test, which is stated to blacken these oils, whereas vegetable oils are bleached by chlorine. The liver oils contain notable proportions of cholesterol. The nature of the fatty acids in these oils is very imperfectly known. Some of them have high Reichert values, pointing to the presence of large quantities of volatile acids. Most of these oils con¬ sist of glycerides of unsaturated fatty acids, as is shown by their high iodine values, ranging, as they do, from 120 upwards. The physetoleic acid of the earlier authors could not be detected by Fahrion 2 on examining various fish oils. He thinks, however, that he has proved the presence of an unsaturated acid C 18 H 30 O.,—jecoric acid—(cp. p. 62), and infers the presence of an unsaturated acid of the composition C 17 H 32 0 2 —asellic acid—from the dihydroxyasellic acid obtained on oxidising the fatty acids of sardine oil. An investigation of the fatty acids of the oils belonging to this class is still a desideratum, especially since Heyerdahl claims to have discovered two new unsaturated fatty acids in cod liver oil, viz. jecoleic acid (p. 59), and therapic acid (p. 63). Owing to the large amount of unsaturated fatty acids they con¬ tain, they develop a considerable amount of heat when treated with sulphuric acid (Maumend test) or with bromine (see p. 301). iii. iv. Drying- and Non-drying- Oils Although the extremes of these two groups, as represented by linseed oil and, say, olive oil, are sharply defined in that the former easily “dries up” to a varnish on exposure to air, even at the ordinary temperature, whereas the latter remains comparatively unchanged under the same conditions, there exist so many gradations between these two extremes, that a sharp line of demarcation cannot be drawn. The gradual transition from the true drying oils to the decidedly non-drying oils admits of the interposition of an inter¬ mediate class of semi-drying oils (cp. chap, xi.), but as the process of drying into a varnish may occupy in some cases as much as several months, it is evident that a strict subdivision cannot be based on the more or less defined drying properties. It should be noted that the distinction drawn here is based on the behaviour of the oils at the ordinary temperature, for according 1 Jour. Chem. Soc. Ind. 1894, 617. 2 Ibid. 1893, 938 ; 935. 280 EXAMINATION OF FATTY OILS AND LIQUID WAXES chap. to Livache (cp. p. 288) all oils, even solid fats, are oxidised on exposure to air at higher temperatures. Some preliminary tests, admitting of an approximate discrimina¬ tion of the various oils belonging to these groups, are the Elaidin test, the Sulphur Chloride test, the Oxygen Absorption test, and the Thermal tests. The most reliable methods, however, of distinguishing the oils are furnished by the quantitative reactions. A workable principle of classification appears to be the iodine-absorbing power of these oils, and this principle will be adopted in chap. xi. 1. Elaidin Test This test is based on the fact that olein is converted into the solid isomeric elaidin by nitrous acid, whilst the glycerides of linolic, linolenic, and isolinolenic acids remain liquid under the same con¬ ditions. The non-drying oils yield therefore solid masses, whereas the semi-drying and the drying oils give more or less liquid products (cp. chap. i. p. 13, Lidoff ). This test was proposed first by Poutet in 1819 for the examination of adulterated olive oil; his original directions have been modified by many experimenters. Poutet’s test, as practised in the Paris Municipal Laboratory, is carried out in the following manner :—10 grms. of the oil under examination, 5 grms. of nitric acid of spec, gravity 1’38 to 1'41, and 1 grm. of mercury, are placed in a test-tube, and the mercury dissolved by shaking continuously for three minutes. The mixture is then allowed to stand for twenty minutes, when it is shaken again for one minute. The behaviour of different oils after that time is recorded in the following table :— Kind of Oil. Olive oil Arachis oil Sheep’s foot oil Sesame oil Colza Oil (“ Saponified ” oleine Linseed oil . Cod liver oil . Whale oil Hemp seed oil Consistency. Solidified after 60 minutes. ,, „ 80 ,, ,, 120 „ „ 185 „ „ „ 185 „ Assumes the consistency of dough after 120 minutes.) Forms a red, dough-like scum. Becomes doughy, red, and forms a scum. Same appearance. Remains unchanged. For mercury copper maybe substituted. 10 c.c. of oil are placed together with 10 c.c. of 25 per cent nitric acid and 1 grm. of copper wire in a test-tube, and allowed to stand. The various modifications proposed of the elaidin test have been discussed by Archbutt ,* who has made a thorough examination of them. His results point to the following conclusions :— (1) That the test must be made at a temperature not lower than 25° C., and that the temperature must be uniform throughout the experiment. 1 Jour. Soc. Cliem. Ind. 1886, 304. IX ELAIDIN TEST 281 (2) That the length of time required for solidification is of far greater importance than the ultimate consistency of the elaidin formed. Archbutt prepares and applies Poutet’s reagent in the following manner:—18 grms. of mercury are placed in a dry stoppered 50 c.c. cylinder, and 15‘6 c.c. of nitric acid of T42 spec, gravity are added from a burette. The nitrous acid is entirely absorbed with production of a green colouration ; as long as the reagent retains its green colour it is fit for use. 8 grms. of the reagent are shaken up with 96 grms. of the oil in a wide-mouthed stoppered bottle, placed in water of the required temperature, and again shaken at intervals of ten minutes during two hours. When tested in this manner, the more important oils may be arranged according to Allen 1 in four groups :— (a) A solid, hard mass is yielded by : Olive oil, almond oil, arachis oil, lard oil, sperm oil, and sometimes neat’s foot oil. (b) A butter-like mass is yielded by : Neat’s foot oil, Arctic sperm oil, mustard seed oil, and sometimes by arachis, sperm, and rape oils. (c) A pasty or buttery mass, separating from a fluid portion, is yielded by : Rape oil, sesam6 oil, cotton seed oil, sunflower oil, Niger seed oil, cod liver oil, seal oil, whale oil, and porpoise oil. (cl) Liquid products are yielded by : Linseed oil, hemp seed oil, walnut oil, and other drying oils. Archbutt has also experimented with a reagent prepared by passing dry sulphur dioxide into cold nitric acid of spec, gravity 1’42. By this reagent cotton seed oil and rape oil also are solidified; the pro¬ duct yielded by pure cotton seed oil is red, that given by rape oil deep red ; but 10 per cent of either of these oils in olive oil does not sensibly colour the white elaidin yielded by the latter oil. The hardest elaidins are obtained from olive oil, arachis oil, and lard oil. The elaidin test has been specially applied to the examina¬ tion of olive oil (cp. p. 461). The elaidin test cannot, however, be made to serve as a quanti¬ tative reaction. It has been shown by Hilbl that the most serious errors may be committed, when an attempt is made to draw con¬ clusions as to the composition of an oil from differences in the time required for the formation of elaidin, and from observations of the consistency and colour of the solidified mass, since the mode of preparing the nitrous acid, the mode of mixing the acid and oil, the shape of the vessel, and chiefly the temperature, influence the results to a very considerable extent. 2 Nor should it be forgotten that the age of an oil and the manner in which it has been kept 1 Comm. Orff. Analysis, ii. 58. 2 The same conclusions have been re-stated by Wellemann, Jour. Soc. Chem. Ind. 1891, 800. 282 EXAMINATION OF FATTY OILS AND LIQUID WAXES chap. (exposure to air and light) have an important bearing on the results of the elaidin test. Thus Gintl has shown that an olive oil after exposure to sunlight for a fortnight did not yield any elaidin at all. In order to obtain trustworthy results, it will be found best to institute side by side with the oil under examination a test with standard oils of known purity under exactly the same conditions. 2. Sulphur Chloride Test E. Bruce Warren states that drying oils , on treatment with sulphur chloride, S 2 C1 2 , yield solid masses, insoluble in carbon bisulphide, whereas non-clrying oils on the same treatment give soluble products. On this reaction he bases a mode of discriminating between drying and non-drying oils. He determines the amount of drying oils in mixtures of fatty oils in the following manner:— The reagent employed is sulphur chloride, diluted with an equal volume of carbon bisulphide. The sulphur chloride is obtained from the commercial yellow sulphur chloride, or “ chloride of sulphur,” by fractional distillation, rejecting the portion boiling below 137° C. [The portions having a lower boiling point may be digested with a moderate excess of sulphur and fractionated again.] The sulphur chloride is mixed with an equal volume of carbon bisulphide, and the reagent is kept in bottles closed by corks coated with paraffin wax. The exact quantity required for a test is withdrawn by means of a pipette. To perform a test, 5 grms. of the oil under examination are mixed in a porcelain crucible of about 120 c.c. capacity with 2 c.c. of the reagent and 2 c.c. of carbon bisulphide, and [warmed on the water-bath, with constant stirring, until reaction sets in. The mass soon becomes hard. The product must be broken up with a glass rod as completely as possible, in order to allow thorough expulsion of the volatile substances, and is dried until constant weight is obtained. The appearance of the product, both before and after drying—especially its colour and consistency—should be noted. The dried mass is then finely powdered and exhausted with carbon bisulphide, the solution evaporated to dryness, and the residue weighed. The quantity of the insoluble portion is found by difference. [It should be noted that every trace of moisture must be rigorously excluded.] d hus Warren has obtained the following figures on examining poppy seed and linseed oils :— 5 grms. of Solid insoluble Pro¬ duct. Liquid soluble Pro¬ duct. Grms. Grms. Poppy seed oil gave 6-46 1-96 Linseed oil ,, 6-36 0-78 IX SULPHUR CHLORIDE TEST 283 Warren's method is based on older observations made by Rochlederf Roussin , 2 Perraf and Merrier} His results, however, do not agree with Rochleder’s statement that olive oil, eminently a non-drying oil, yields an insoluble product, and are further contradicted by Sommer 5 and by Ilenriques . 6 The experiments carried out by the latter prove conclusively that there exists no relationship between the drying- power of an oil and the proportion of sulphur chloride it requires to form a solid product. Also work, undertaken by the writer (with a view to converting the sulphur chloride test into a quantitative reaction) proves the unreliableness of Warren’s statements, as is shown in the following table :— Oils and Pais treated with S 2 C1 2 ; 5 grms. of fat with 2 c.c. S.,C1 0 , and 2 c.c. CS 2 ( Lewkowitsch) A. Product completely soluble in Carbon Bisulphide Class of Oil. Kind of Oil. Mass thickens after Minutes. t Sperm oil, No. 1 20 Sperm oil, No. 2 45 Liquid waxes . . J Arctic sperm oil, No. 1 45 Arctic sperm oil, No. 2 55 l Arctic sperm oil, No. 3 30 I Palm oil > Vegetable fats . . i Palm nut oil ° Cocoa nut oil l Mowrah seed oil Does not f Beef tallow thicken. Animal fats . . -j Mutton tallow Lard 1 Butter fat 1 Dingl. Polyt. Jour. 111. 159. 2 Ibid. 151. 136. 3 Ibid. 151. 138. 4 Compt. rend. 84. 916. 5 German Patent, No. 50,282. 6 Jour. Soc. Chem. Ind. 1894, 47. [Table 284 EXAMINATION OF FATTY OILS AND LIQUID WAXES chap. B. Products not completely soluble in Carbon Bisulphide Class of Oil. Kind of Oil. ( Linseed oil Drying oils . Hemp seed oil Poppy seed oil Fish oils . Japan fish oil Liver oils . . j Cod liver, pure Cod liver, rancid Blubber oils . i Seal oil Whale oil l Cotton seed oil Sesame oil Semi-drying oils - Colza oil Kape oil Croton oil Castor oil Peach oil Almond oil, sweet Almond oil, bitter Arachis oil Non-drying oils - Olive oil Sheep’s foot oil Horses’ foot oil Neat’s foot oil Lard oil Tallow oil Solidifie In the Cold. after Minutes. On the Water-bath. Soluble in CS 2 . 10 2 Per cent. 14-4 11 9-2 21 10'6 9 ... 12-4 15 4-4 H ... 6'4 11 4'4 13 3-0 20 4 24-0 21 18-4 23 2-8 12 2 4-2 18 25-4 4 at once 3'8 26 4-8 27 4-0 28 3-4 30 6-0 22 4 4-2 36 6-0 20 13-6 23 9-4 10 ... 15-0 12 29-8 I have further found a remarkable difference in the action of sulphur chloride on vegetable oils on the one hand, and on their mixed fatty acids on the other. Whereas in the case of the former the reaction takes place quickly with the formation of a solid product, the free acids react more slowly, yielding but semi-solid, viscous products. The reaction that takes place, when sulphur chloride is allowed to act on oils, appears to consist in an absorption of the elements of sulphur chloride, much as iodine is absorbed in HuMs test. In fact, Henriques has shown that oils after treatment with sulphur chloride have a far lower iodine absorption value than before. Pfizer and Horn, and afterwards also Henriques, have proved that the products of reaction contain sulphur and chlorine in approximately the same pro¬ portion as sulphur chloride (S 2 C1 2 ). Thus, the action of sulphur chloride on oils appears to consist in the conversion of unsaturated fatty acids or their glycerides into saturated compounds. Further research will be required to show whether a separation of saturated from unsaturated glycerides can be effected by means of this reagent. In this connection the difference is remarkable between lard and tallow on the one hand and their oleines on the other. Much light has been further thrown on the rationale of the IX OXYGEN ABSORPTION TEST 285 chemical reaction involved by researches of C. 0. Weber. 1 Further information on that subject will be given under “ Rubber Substitutes ” (p. 742). For the thermal reaction with sulphur chloride cp. p. 299. 3. Oxygen Absorption Test. Livaehe Test The drying of an oil not being complete before the lapse of several months, a convenient method of distinguishing drying and semi-drying oils from non-drying oils cannot be based on the determination of the increase in weight which oils attain on being exposed to the atmosphere in thin layers. Casselmann has therefore proposed to shorten the period of ex¬ posure by heating 3 to 4 grms. of an oil for three hours daily up to 150° C. His results are tabulated below :— Kind of Oil. Behaviour on heating to 150° C. for Three Hours daily. Linseed oil Poppy seed oil Hemp seed oil Sunflower oil . Dried up after 1^ to 2 days. ,, ,, ,, 4 to 5 days. ,, ,, ,, a few more days. Gives a viscid, gelatinous mass after three months. It is evident that no reliable results can be obtained by proceeding in this manner. The following table, due to Kissling 2 shows the gain in weight of several oils, 10 grms. of each, spread out so as to cover a surface of 35 sq. cm., having been exposed to the air for ten days at the ordinary temperature. Kind of Oil. Gain in Weight of 100 parts in Ten Days at ordinary Temperature. Olive oil . o-o Rape oil, crude .... 0-05 Rape oil, refined .... O'O Neat’s foot oil, refined . 0'065 Cotton seed oil . 0'545 Linseed oil, crude 1-130 Linseed oil, boiled 3-400 Triolein . o-o Experiments carried out by the same author at temperatures fi om 100° to 105° C. show a different result 3 :— 1 Jour. Chem. Soc. Ind. 1894, 11. “ Ibid. 1891, //8. 3 On passing air through linseed oil at 100° C. for 6 days Kissling [Jour. Soc. them. Ind. 1895, 479) found that 0'87 per cent of oxygen was taken up daily, 0'41 per cent ol which remained in the oil, whilst 0*46 were carried away as volatile gases consisting of 15 per cent C0 2 and 85 per cent of volatile acids of the methane series and other organic substances. 286 EXAMINATION OF FATTY OILS AND LIQUID WAXES CHAP. Kind of Oil. Gain (+) or Loss (-) in Weight of 100 parts after exposure to Air for 2 Hours. 22 Hours. 42 Hours. Kemarks. Crude Rape oil, fresh Crude Rape oil, old .... Crude Rape oil, very old . Refined Rape oil ... Refined Rape oil, old Olive oil . Crude Neat’s foot oil, German . Crude Neat’s foot oil, partially refined Crude Neat’s foot oil, refined American Crude Lard oil, American . Refined Lard oil, American Cotton seed oil, old . Crude Linseed oil ... Boiled Linseed oil Triolein ...... + 0T2 -0T4 -0-02 -0-13 -o-io -0T5 -0-67 -0-23 -0-08 -0-21 -0-08 -0-52 + 0-26 -0-53 + 1-08 + 0-55 + 0-42 + 0-57 + 0-51 -077 -1-40 + 0-06 -0-40 -1-44 -0-56 -0-43 + 0T9 + 0-97 -3-34 - 0-27 - 0-96 Moderate skin Moderate skin Moderate skin Moderate skin Moderate skin Slight skin No skin Moderate skin Moderate skin No skin Moderate skin Strong skin Strong skin Strong skin No skin It will be observed from these data, that the better drying an oil is, the more oxygen it absorbs, and consequently the greater the gain in weight after a certain time. The rate of absorption of oxygen is very much accelerated, accord¬ ing to Livache, 1 by addition of finely divided lead. Thus, linseed oil leaches, in consequence of this treatment, the maximum of absorption within a few days, whereas under ordinary conditions the same result is only ailived at after several months. The lead-powder is prepared by precipitating a lead salt with zinc, washing the precipitate rapidly in succession with water, alcohol, and ether, and finally drying in a vacuum. In actual testing one operates as follows :—Spread about 1 grm. of the lead, weighed off accurately, on a somewhat large watch-glass in a thin layer, and then allow to fall on to it from a pipette 0’6 to O'7 grms. (not more) of the oil to be tested, placing each drop on a different portion of the lead, and taking care that the drops do not run into one another. Then allow the watch-glass to stand at the ordinary temperature at a place exposed to light. Drying oils will be found to have absorbed the maximum quantity of oxygen after eighteen hours, or in some cases after three days, whereas non-drying oils do not gain any weight before four or five days. The free fatty acids, with the notable exception of cotton seed oil fatty acids, behave like their glycerides, i.e. their increase in weight corresponds to the gain in weight of the corresponding neutral oils. Livache's results are recorded in the subjoined table :— 1 Jour. Soc. Ghem. Ind. 1886, 494. IX LIVACHE TEST 287 Kind of OiL Gain in Weight of 100 parts Of Oil 2 Days. after 7 Days. Of Fatty Acids after 8 Days. Linseed oil. 14-3 11-0 Walnut oil. 7'9 6-0 Poppy seed oil . 6'8 3-7 Cotton seed oil . 5'9 0-8 Beechnut oil 4-3 2-6 Colza oil o-o 2'9 2-6 Rape oil o-o 2-9 0-9 Sesame oil . o-o 2'4 2-0 Arachis oil. o-o 1-8 1-3 Olive oil o-o 1-7 0-7 In order to obtain a correct estimation as to the drying properties of an oil, regard must be had not only to the increment in weight, but also to the length of time required. Thus, of the two oils, the drying powers of which are given in the following table :— No. of Oil. Weight of Oil. Weight of Lead. Gain in Weig lit of 100 parts after 1 Day. 3 Days. 6 Days. 9 Days. 1 3-246 1-012 14-4 15-7 unchanged 2 3-154 0-653 2-45 12-0 15-9 unchanged the oil No. 1 must be considered the better drying, although both oils [evidently both linseed oils] finally reach the same absorption of oxygen. Jean has used Livache’s method for the examination of the follow¬ ing oils, allowing them to stand for three days in a dry atmosphere (under a desiccator over sulphuric acid); there are added Tortelli’s 1 numbers, obtained by the same method :— Kind of Oil. Gain in Weight of 100 parts after 3 Days (Jean). until weight remained constant (Tortelli). Whale oil . 8-266 7-62 Japan fish oil 8-194 Cod liver oil ... 6-383 5-43 Menhaden oil 5-454 Sperm oil 1-629 Sardine oil . 4-22 Neat’s foot oil 1-19 1 Annali del Led). Chim. Centr. delle Gabelle, iii. 1897, 211. 288 EXAMINATION OF FATTY OILS AND LIQUID WAXES chap. Long before Livache, the amount of oxygen absorbed by oils was used by van KerTchoff in the examination of rape oil. His method, which can only claim historical interest, was to run the oil from a burette into a known volume of a permanganate solution 1 until it was decolourised. Thus he has found that— 15 c.c. of permanganate solution were reduced by 3*21 c.c. of rape oil. 1 *01 ,, cameline oil. LOO ,, linseed oil. Fox has modified Livache's process by heating 1 grm. of the oil to be tested with 0'5 grm. of precipitated lead to 105° C. (220° F.) in a sealed tube, and measuring the quantity of oxygen absorbed. His results are tabulated below :— Kind of Oil. c.c. of Oxygen absorbed. Linseed oil (Baltic) 191 Linseed oils from other sources . . 126-186 Cotton seed oil . 24-6 Rape oil . 20 Olive oil . . 8 '2-8 -7 0. Bach has adopted Fox’s method for the examination of lubricat¬ ing oils (see p. 714). As will be seen from Fox’s table, even olive oil, the type of a non¬ drying oil, absorbs oxygen at an elevated temperature. Livache 2 has shown recently that rape oil and olive oil behave like drying oils when they are kept at a sufficiently high temperature (120°-160° C. with or without previous treatment with litharge or manganese borate), and become finally transformed into a solid substance, viz. Mulder’s “linoxyn” (see p. 337). Further experiments of Livache demonstrate that all fatty substances without exception, whether of vegetable or animal origin, even solid animal fats, can be converted into “ linoxyn,” the rapidity of the change depending on the temper¬ ature used and the previous treatment to which the fatty substance has been subjected. It will therefore be evident that the subdivision of oils into drying, semi-drying, and non-drying oils (see p. 277) is only admissible on the understanding that this distinction holds good for the ordinary temperature. Fahrion 3 has recently proposed to determine the oxygen absorption of oils by impregnating a strip of chamois leather with the oil under examination, and exposing it, suspended from a brass hook, to the atmosphere. Side by side with it is suspended a similar strip of leather, serving as a blank test, so as to eliminate the influence of evaporation of moisture from the leather, etc. Fahrion’s results are tabulated below; the absorption of oxygen has been calculated to per cents of oil used:— 1 This method has been proposed again by Crauzel (Jour. Soc. Chem. Ind. 1895, 316) for detection of fatty oils in vaseline. 2 Jour. Soc. Chem. Ind. 1895, 811. 3 Ibid. 1894, 405. Absorption of Oxygen in 100 parts of Oil after OXYGEN ABSORPTION U 290 EXAMINATION OF FATTY OILS AND LIQUID WAXES chap. In order to obtain more rapid oxidation Bishop 1 spreads the oil on precipitated silica, and adds a little manganese resinate obtained from the commercial product by extraction with petroleum ether or common ether. Bishop proceeds as follows: 5 to TO grms. of the oil are placed in a dish and mixed on the water-bath with exactly 2 per cent of manganese resinate, until the latter is completely dissolved. Meanwhile 1 grm. of calcined precipitated silica is weighed out into a flat-bottomed dish, and T02 grm. of the resinated oil, drop by drop, by means of a pipette, is added. The mass is intimately mixed by means of a glass rod, carefully spread over the bottom of the dish so as to offer a large surface to the air, and then left at a temperature of 17°-25° C. for drying oils, and at 20°-30° C. for other oils. The dish is weighed after six hours, and twice again in the twenty-four hours, a fresh surface being exposed after each weighing by stirring the mass. The maximum increase in weight, calculated to per cents, is termed by Bishop the degree of oxidation. The following table contains the results obtained by Bishop .-— Oils. Specific Gravity. Absorption of Oxygen in Per Cent ‘ 1 Degrees of Oxidation.” Mean Values. Linseed oil, French .... 0-9327 17-70-16-40 17-05 ,, ,, La Plata 0-9304 15-45-15-00 15-20 Hemp seed oil . 0-9287 14-55-14-30 14-40 Poppy seed oil, French 0-924 14-50-13-90 14-20 Walnut oil, French .... 0-924 13-70 13-70 Cotton seed oil .... 0-924 8-60 8-60 ,, ,, without stearine 0-923 9-60-9-30 9-45 Sesame oil, Senegal .... 0-9215 8-95-8-50 870 ,, ,, Indian .... 0-921 7-40 7-40 Arachis oil, African .... 0-916 670 6-70 ,, ,, white .... 0-916 6-50 6-50 Colza oil, French .... 0-9142 6-40 (?) 6-40 (?) ,, ,, Indian .... 0-9137 5-90-5-80 (?) 5-85 (?) Olive oil . 0-9155 5-30 (?) 5-30 (?) The chemical changes occurring during the drying of oils are but very imperfectly understood, and further experiments are required to elucidate this important question (cp. “Boiled Oil,” p. 738). The drying properties of an oil seem to stand in direct ratio to the pro¬ portion of glycerides of linolic and linolenic acids in the oil. There¬ fore, in a general way, the rule holds good that the higher the iodine value the better drying is an oil (Japanese wood oil seems to form an exception, p. 345). It should, however, be borne in mind that oleic acid, although an unsaturated acid, possesses no drying pro¬ perties. Therefore a direct proportionality between the quantities of oxygen and of iodine, which drying oils assimilate, cannot be estab¬ lished, inasmuch as two atoms of iodine absorbed should correspond to one atom of oxygen. Still, a certain proportionality does exist, as will be seen from the following table, in which the percentage of 1 Jour. Pharm. et Chimie, 1896, 55 ; Jour. Soc. Chem. Ind. 1896, 475. IX MAUMENTi TEST 291 oxygen actually absorbed is compared with the quantity of oxygen calculated from the iodine absorption value by multiplying the latter , 16 by 254 ==0 ' 063 - Kind of Oil. Oxygen absorbed. Determined by Analysis. Calculated from Iodine Value. Linseed oil 14-3 11-0 Walnut oil 7-9 9-0 Poppy seed oil 6-8 8'6 Cotton seed oil 5-9 67 Hubl obtained values in better agreement with the iodine num¬ bers by using finely-divided copper instead of lead. If a correct method of determining accurately the oxygen absorbed were known, it would be possible to class the determination of the drying power, or, as it might be called, of the “ oxygen value,” amongst the quantitative reactions. The absorption of oxygen from the atmosphere is of great practical importance for the industry of paint oils, and has a very important bearing on the liability of oils to cause spontaneous combustion when spread in a finely-divided state on fibrous organic substances (cp. chap. xii. p. 706). 4. Thermal Tests (a) Thermal Reaction with Sulphuric Acid: Maumend Test Maumend 1 has found that, on mixing concentrated sulphuric acid with drying oils, a higher temperature is produced than is the case with non-drying oils, and he proposed therefore the sulphuric acid test as a useful reaction in the examination of fats. Fehling, Casselmann, Allen, Archbutt, and others have confirmed Maumend's observation, and proved that comparable results are ob¬ tained if the experiments are carried out under exactly the same condi¬ tions. It is therefore necessary to always use sulphuric acid of precisely the same strength (the acid must be kept carefully protected from access of air), to cool the oil and the reagent to exactly the same temperature before commencing the operation, and even to use the same vessel for each determination. 2 ( Archbutt , however, thinks that it is unnecessary to work at some constant initial temperature.) Maumend 3 has found that sulphuric acid heated to 320° C., and used immediately after cooling, gave a different temperature reaction to that given by acid that had not been so treated. This is due to partial dissociation of the sulphuric acid having taken place. Since, according to Lunge and Naef, sulphuric acid of 99 per cent and 96 1 Compt. rend. 35. (1882), 572. 2 Jour. Soc. Chem. Ind. 1891, 234. 3 Compt. rend. 92. 721. 292 EXAMINATION OF FATTY OILS AND LIQUID WAXES chav. per cent of S0 4 H 2 possess the same specific gravity, it is best to ascertain the strength of the sulphuric acid by titration (Archbutt 1 ). The influence of the concentration of the acid on the result is shown in the following table due to Archbutt (cp. also below, Thomson and Ballantyne’s table):— Kind of Oil. Rise of Temperature observed with Acid containing per cent of SO 4 H 2 . 97-38. 96-71. 95-72. 94-72. 93-75. 92-73. 91-85. °C. °C. °C. °C. °C. °C. °C. Olive oil, genuine . -j 43-25 42-25 | 42 39 36-5 34-5 31 { 28 29-25 Rape oil, genuine 63, 62 61 58 54 50-25 47 40-5,43 Olive oil, impure . 48-5 \ 48-5 J 47,47-5 / 43-75 \ 44-25 VO VO 4>- O O 38-5, 39 / 35-5 \ 35-5 32-5 32-5 It should also be noted that on using weak acid the rise of temperature is very slow. Archbutt recommends the following method of operating: 50 grms. of the oil to be tested (weighed accurately to within 10 to 20 milligrms.) are placed in a beaker of 200 c.c. capacity. The bottle of acid and the beaker of oil are then placed in a large vessel of water until both liquids have acquired the same temperature, which should be about 20° C. The beaker containing the oil is then removed, wiped outside, and placed in a “ nest ” of cardboard, having hollow sides stuffed with cotton wool, or in a larger beaker lined with cotton wad¬ ding. A thermometer is then im¬ mersed in the oil, and the temperature having been read off, 10 c.c. of the concentrated sulphuric acid are rapidly withdrawn from the bottle with a pipette and run into the oil, the time allowed for the emptying of the pipette occupying one minute. During this time the oil should be stirred with the thermometer, and the stirring continued until no further rise of tempera¬ ture is observed. The highest point is easily noticed, as the tempera¬ ture remains constant for some little time before it begins to fall. In order to secure a more perfect admixture of oil and acid, Allen fastens the thermometer to a tin plate, bent into the shape of a screw- paddle. This piece of apparatus, shown in Fig. 42, forms an efficient stirrer, producing a complete intermixture of the two liquids. 1 Jour. Soc. Cthem. Ind. 1886, 304. IX MAUMENfi TEST 293 The following table, compiled by Allen, 1 from the observations of various chemists, gives the rise of temperature by Maumend’s test for various oils. The writer has re-arranged the table according to the iodine values, and has added the last column in order to show the correlation of the thermal reaction and the iodine absorbing power of the oils. Further numbers will be found in chap, xi., where the individual oils will be described. Kind of Oil. Rise of Temperature with Sulphuric Acid. °C. Class of Oils. Maumene. Baynes. Dobb. Archbutt. Allen. Wiley. Linseed oil . 103 104-124 104-111 Drying oils Hemp seed oil 98 Walnut oil . 101 Poppy seed oil 74 86-88 Niger seed oil 82 81 African fisli oil 156 Liver, fish, and blubber Menhaden oil 123-128 126 oils Cod liver oil. 102-103 [116 113 Shark liver oil 90 Seal oil 92 Whale oil, 91 northern Whale oil, 85-86 92 southern Porpoise oil . 50 Cotton seed oil, crude 84 61 70 67-69 79 Semi-drying and non- Cottonseed oil, 77 75-76 74-75 drying oils refined Sesame oil . 68 65 Beechnut oil 65 Rape and 57-58 60-92 54-60 55-64 51-60 Colza oils Castor oil 47 46 Almond oil . 52-54 35 Olive oil 42 * 40 39-43 41-45 41-43 Arachis oil . 67 47-60 69 Cocoa nut 26-27 oleine Neat’s foot oil 43 Terrestrial Horses’ foot oil 51 animal oils Lard oil 41 54 Tallow oil 41-44 Sperm oil 51 45-47 Liquid waxes Arctic sperm oil 42 41-47 Oleic acid 37-5 38-5 1 Comm. Org. A nalysis, ii. 56 ; Thorpe, Dictionary of Applied Chemistry, iii. 36. 294 EXAMINATION OF FATTY OILS AND LIQUID WAXES chap. There is undoubtedly a correlation between the rise of tempera¬ ture in Maumend’s test and the iodine value of an oil; the higher the temperature rises the higher is the iodine number (cp. chap. xi. under “Olive Oil,” p. 461). However, this correlation cannot be expressed by a constant factor, for Hehner and Mitchell 1 derived from Iodine number Maumene test. 9 observations, made by one and the same observer, on lards, the factor ....... 1748 10 observations on olive oils, the factor .... 27837 203 observations on olive oils, the factor . . . . 2 ’314 Even on applying the last-named factor to other oils examined by the same observers, discordant results were obtained. Oils causing a very high rise of temperature should be diluted, according to MaumenS, with a measured quantity of olive oil. Bishop 2 recommends mineral oil for the same purpose. The rise of tempera¬ ture, which the original oil would show, is then calculated from the observed rise of temperature in the following way, which, however, is not quite correct. Let 67° C. be the rise of temperature obtained with 10 grms. of cod liver oil, 10 grms. of mineral oil, and 20 grms. of sulphuric acid ; if the rise of temperature of the mineral oil alone be 14° C., then the figure for cod liver oil would be 2(67 - 14) = 106° C. (Bishop). Bishop obtained in this way the following results :— Kind of Oil. Rise of Temperature calculated. °C. Cod liver oil, white ..... 100 Cod liver oil, pale ..... 102 Cod liver oil, brown ..... 102-5 Arachis oil 66 Mixture consisting of 80 parts of cod liver oil, pale, and of 20 parts of arachis oil Mineral oil | 97 14 Ellis 3 has also recommended mineral oil as a diluent. Having found that no concordant results were obtained when the maximum temperature was much over 60° C. (which seems to indicate that above that temperature further reactions set in between sulphuric acid and the oil), Ellis considers it necessary to dilute each oil, if required, with mineral oil in such proportions that the highest temperature attained may be below 60° C. For his mode of calculation and his results the original paper must be consulted. Jean 4 determines the heat evolved in Mawnend’s test by means of a special form of apparatus, styled by him “ Thermelseometer.” This 1 Analyst, 1895, 147. 2 Jour. Phar. Chem. 20. 302. 3 Jour. Soc. Chem. Ind. 1886, 150 ; 361. 4 Ibid. 1890, 113. IX THERMELiEOMETER 295 apparatus (Fig. 43) consists of a small vessel, A, 4 cm. wide and 6 cm. high, graduated for the reception of 15 c.c. of oil, and of the acid holder B. The latter is fitted with a hollow glass-stopper C, to which is attached the india- rubber tube R. The neck of the acid holder is fastened to a clamp, to which a thermometer is fixed. 1 The mode of operation is as follows: 15 c.c. of oil, previously warmed to about 40° to 50° C., are placed in A, and 5 c.c. of concentrated sulphuric acid of specific gravity 1 - 819 are intro¬ duced into B. Vessel B is then placed in A, and the apparatus allowed to cool to 30° C., the thermometer being used to stir the oil occa¬ sionally. To prevent further cooling, A is placed in the felt-lined brass case E. The acid is then forced out of B through the small syphon tube into A by blowing through R, and the mixture of oil and acid is well stirred until the maximum temperature is reached. Drying oils should be Fi s- 43 - mixed with 5 c.c. of mineral oil. If the oils are much oxidised they must be treated with alcohol before testing; a better plan still is to prepare the fatty acids and test the latter. Jean has obtained the following results with his “ thermelseometer ” :— Rise of Temperature of the Kind, of Oil. Neutral Oil. Fatty Acids. °C. °C. Olive oil . 41-5 45 Linseed oil 61 109 Colza oil, French 37 44 Colza oil, India. 37 46 The numbers obtained by Jean are, of course, not directly com¬ parable with those given in the table, p. 293. Exposure to light and air with its concomitant oxidation in¬ creases the temperature reaction with sulphuric acid. Thus Arch- butt records for a sample of olive oil, which, kept in the dark, gave a Maumene test of 41'5° C., after exposure, the higher figure 52-5° C. This fact is brought out more prominently by Ballantyne’s results :— 1 Another apparatus, offering no special feature, has been used by Wiley (cp. Wiley, Lard and Lard Adulterations , Washington, 1889). 296 EXAMINATION OF FATTY OILS AND LIQUID WAXES CHAP. Rise of Temperature. Kind of Oil. Original Oil. After Exposure. °C. °C. Olive oil . 44 67 Castor oil .... 73 78-5 Rape oil. 61-5 72-5 Cotton seed oil ... 75-5 100 Arachis oil ... 73-5 90 Linseed oil ... 113-5 131 It should be noted that the reverse holds good for the iodine absorption numbers. Thomson and Ballantyne 1 propose to refer the rise of tempera- ture obtained with 50 grms. of oil and 10 c.c. of sulphuric acid to the rise of temperature which 50 grms. of water give under exactly the same conditions in the same vessel. The quotient Rise of temperature with oil . Eise of temperature with water 18 termed by them “ 6 P ecific tem P eril - ture reaction ”; it expresses, therefore, the rise of temperature com¬ pared with water as unity. In the following table the results are multiplied by 100 in order to dispense with decimals. By recording the results in this way the discrepancies obtained on testing with sulphuric acids of varying strengths are, of course, considerably re¬ duced, as will be seen from the following table :— Kind of Oil. Sulphuric Acid of 95 - 4 per cent. Sulphuric Acid of 96 - 8 per cent. Sulphuric Acid of 99 per cent. Rise in Tempera¬ ture. °C. Specific Tempera¬ ture Reaction. Rise in Tempera¬ ture. °C. Specific Tempera¬ ture Reaction. Rise in Tempera¬ ture. -c. Specific Tempera¬ ture Reaction. Olive oil . 36-5 95 39-4 95 44-8 96 Olive oil . 39 94 43-8 94 Rape oil 49 127 58 124 Castor oil . 34 88 37 89 Linseed oil 104-5 270 125-2 269 Water 38-6 100 41-4 100 46-5 100 The following specific temperature reactions are given by Thomson and Ballantyne, and by Jenkins 2 :— 1 Jour. Soc. Chem. Ind. 1891, 234. 2 Ibid. 1897, 194. IX SPECIFIC TEMPERATURE REACTION 297 Kind of Oil. Specific Te Reac Water Thomson and Ballan- tyne. mperature tion. =100. Jenkins. Class of Oil. Japanese wood oil . 372 Drying oils Linseed oil, Baltic .... 349 ,, East India . 320 ,, ,, River Plate . 320 ,, ,, raw .... 313 ,, ,, boiled .... 248 Menhaden oil . 306 Fish oils Cod liver oil, medicinal . 272 Liver oils ,, ,, Scotch 246 ,, ,, Newfoundland . 243 Seal oil . 278 Blubber oils ,, ,, tinged .... 229 ,, ,, cold drawn, pale . 225 ,, ,, Norwegian .... 223 ,, ,, steamed, pale 212 Whale oil, pale .... 157 Cotton seed oil, refined Egyptian . 170 Semi-drying oils 169 ,, ,, crude Egyptian 163 Ravison rape oil 162 Rape oil . 144 135 133 130 127 125 Castor oil, commercial 89 105 Sperm oil, southern 100 Liquid waxes Arctic sperm oil (Bottlenose) . 93 103 Arachis oil, commercial . 137 Non-drying oils ,, ,, French, refined . 105 Olive oil, Malaga .... 94 ,, ,, Mogador .... 93 ,, ,, Mytilene 93 ,, ,, Syrian .... 93 ,, ,, commercial 92 94 ,, ,, Candia .... 92 ,, ,, Gioja .... 89 Neat’s foot oil .... 87 Animal oils Blown cotton seed oil 164 Manufactured oils Blown rape oil ... 153 The writer arranged the values in the order of their magnitude, and, as was to be expected, the same order obtains for the different classes of oils as in the table given above, p. 293. 298 EXAMINATION OF FATTY OILS AND LIQUID WAXES chap. Although the Maumend test is not accurate enough to admit of its being classed among the “quantitative reactions,” it must be con¬ sidered a valuable test which, in conjunction with other reactions, notably the “quantitative reactions” (see below), renders valuable services in detecting sophistications. Thus, adulterations practised on olive oil may be detected with comparative ease, olive oil having the lowest rise in temperature, with the exception of animal oils. This reaction may further be used with advantage in the examination of linseed oil for its drying power. Archbutt recommends that every observer should construct a table for himself, using oils of known purity, and whenever a sample of oil is tested, compare the results with those furnished by the standard samples. H. D. Richmond proposes a modification of the Maumend test by intro¬ ducing the Relative Molecular Maumene figure (R.M.M.), that is, the total heat evolved per mean molecule. As his paper does not give experimental values, and bears the character of a preliminary note, the reader must be referred to the original paper. 1 (b) Thermal Reaction with Sulphur Chloride Fawsitt 2 proposed to measure the heat evolved by the action of sulphur chloride on various oils, with a view to discriminating between drying and non-drying oils, after the manner of Maumend’s test (see p. 291). Since, however, this procedure offers no advantage over Maumend’s test, or the bromine heat test (p. 300), it may suffice to briefly describe the modus operandi, and to record the values obtained in the table given below. 30 grms. of the sample are weighed out in a small beaker, which is then placed in a larger beaker, the space between the two beakers being packed with cotton wool. A thermometer is then in¬ serted into the oil, the temperature observed, and the sulphur chloride poured in slowly, with constant stirring. The time is then taken, the thermometer kept stationary until the temperature ceases to rise, and both highest temperature and time noted. 1 Analyst, 1895, 58. 2 Jour. Soc. Chem. Ind. 1888, 552. [Table IX SULPHUR CHLORIDE THERMAL TEST 299 Class of Oil. Kind of Oil. Number of c.c. s 2 ci 2 added. Rise in Tem¬ pera¬ ture. Time in Rising. Rise per Minute. Final Condition of Oil. °C. Min. °C. Drying oils Linseed 2 57 5 11-4 Liquid, viscous > > 3 79 3 26-3 Liquid, very viscous ” 4 97 2 487 Solid, sticky Liver oils . Cod liver 2 55 4 13-7 Liquid, viscous ,, 3 82 3 27-3 Solid, very sticky ) 1 4 103 3 34-3 Solid, dry Blubber oils Seal 2 45 10 4-4 Liquid, more viscous 3 79 6 13-2 Solid, sticky Whale 4 112 5 22-4 Solid, dry 2 57 6 9'4 Liquid, more viscous ,, 3 71 5 14-1 Liquid, very viscous ” 4 91 3 30-2 Solid, dry Semi-drying oils Cotton seed 2 49 11 4-4 Liquid, more viscous ,, 3 64 9 7-1 Liquid, very viscous > > Rape 4 93 6 15-4 Solid, sticky 2 53 10 5-3 Liquid, more viscous ,, 3 66 7 9-3 Solid, slightly sticky ” 4 89 6 14-8 Solid, dry Castor 2 56 2 277 Liquid, very viscous Non-drying oils Olive 2 52 6 87 Liquid, viscous ,, 3 69 5 137 Liquid, very viscous ” 4 94 4 23-5 Solid, dry Liquid waxes . Sperm 2 37 16 2-3 Liquid 3 54 11 4-9 Liquid, more viscous 4 71 8 8-8 Liquid, more viscous ” 5 86 6 14-2 Liquid, very viscous Animal oils Neat’s foot 2 51 7 7-3 Liquid, more viscous 3 66 5 13-2 Liquid, very viscous Lard 4 82 4 20-5 Solid, sticky 2 40 16 2-4 Liquid, very viscous ” 3 62 9 6‘9 Solid, got dry on standing Oleic Acid 2 53 6 10-6 Liquid, viscous 3 74 5 14-9 > > ? > Stearic Acid 4 99 6 16-5 Solid 2 5 ] 7 07 J J J 5 4 8 1 5 1-6 Solid Glycerol 4 21 7 3-0 Liquid 1 Initial temperature. 300 EXAMINATION OF FATTY OILS AND LIQUID WAXES CHAP. (c) Thermal Reaction with Bromine or Heat of Bromination Test. Bromine Thermal Value The action of bromine on fats and oils is attended with consider¬ able evolution of heat. Hehner and Mitchell 1 proved by their re¬ searches that the measurement of the heat thus evolved leads to results furnishing more definite data than those obtained in the Maumen6 test. Hehner and Mitchell proceed as follows:— One grm. of the oil under examination is placed in a Dewar vacuum-jacketed test-tube 2 and dissolved in 10 c.c. of chloroform, the diluent being used to moderate the action. Exactly one c.c. of bromine, measured by means of a pipette (provided at its upper end with a narrow tube filled with caustic lime, and having an asbestos plug at each end), and previously brought to the same temperature as the oil in the vacuum tube, is run in, and the rise of temperature due to the instantaneous reaction is measured by means of a correct thermometer divided into fifths of a degree centigrade. The whole operation occupies only a few minutes. Fatty acids are dissolved in glacial acetic acid instead of chloroform, and treated as above. Hehner and Mitchell compared the numbers obtained for the rise of temperature of various fats and oils with their iodine numbers, with a view to elucidating the correlation, if any, existing between these two values. As will be seen from the following table, given by Hehner and Mitchell, the factor 5'5 serves to express the relation with considerable accuracy for the majority of the fatty substances examined by them under their particular conditions. The column headed “ Deviation ” has been added by the writer. 1 Analyst , 1895, 148. " Ihe oil may be weighed in the tube, suspended obliquely, by means of platinum wire, from the arm of the balance. (Cp. Archbutt, Jour. Soc. Chem. Ind. 1897, 310.) In t^eir earlier experiments Hehner and Mitchell employed an ordinary test-tube packed with cotton wool into a beaker ; the results thus obtained are, cceteris paribus, two degrees centigrade lower. [Table IX BROMINE THERMAL TEST 301 I. Oil or Fat. II. Heat of Bromi¬ nation. III. Iodine Number. IV. Deviation. °C. Experi¬ ment. Calculated from Column II. by multiply¬ ing by 5'5. Absol. Per Cent. Lard, No. 1 . 10-6 57-15 58-3 + 1-15 + 2-00 „ 2. 10-4 57-13 57-2 + 0-07 + 0-12 ,, 3. 11-2 63-11 61-6 -1-51 -2-40 ,, 4. 11-2 61-49 61-6 + 0-11 + 0-18 ,, 5. 11-8 64-69 64-9 + 0-21 + 0-32 „ 6. 11-8 63-96 64-9 + 0-94 + 1-50 „ 7 . 10"2 57-15 56T -1-05 -1-90 „ 8. 10-4 57-80 57-2 -0-60 -1-05 ,, 9. 9'0 50-38 49-5 -0-88 -1-70 „ io. 11-0 58-84 60-5 + 1-66 + 2-7 ,, +10 per cent cotton seed oil. 11-6 64T3 63-8 -0-33 -0-52 Lard fatty acids .... 10-4 59-60 57-2 -2-40 -4-20 > ) 5 ) Mutton fat (kidney) 11-0 59-15 60-5 + 0-35 + 0-57 8'1 44-48 44-5 + 0-02 + 0-05 ,, ,, (flare) 7-6 39-70 41-8 + 2-10 + 5-0 Butter, No. 1 6-6 37-07 36-3 -0-77 -2-1 „ 2 ... . 7-0 38-60 38-5 -o-io -0-27 ,, fatty acids 6-2 36-50 34-1 -2-40 -7-04 Almond oil . 17-6 96-64 96-68 + 0-04 + 0-041 Olive oil .... 15'0 80-76 82-50 + 1-74 + 2-1 Maize oil .... 21-5 122- 118-20 -3-80 -3-2 Cotton seed oil 19-4 107T3 106-70 -0-43 -0-4 Castor oil .... 15-0 83-77 82-50 -1-27 -1-5 Linseed oil, No, 1 30-4 160-7 167-20 + 6-5 + 3-9 ,, ,, 2 ... 31-3 154-9 172-00 + 17-1 + 10-0 Rape oil, No. 1 18-4 88-33 101-20 + 12-87 + 12-7 „ 2 . . . . 17-6 77-2 96-80 + 19-6 + 20-0 Cod liver oil .... 28-0 144-03 140-00 -4-03 -2-9 Commercial oil 19 108-5 104-5 -4-00 -3-8 19-2 105-7 105-6 -o-oi -0-009 18-9 105-7 103-9 -1-8 -1-7 It should be distinctly understood that the factor 5'5 must not be taken as an absolute one, but as depending on the particular vacuum- tube and the modus operandi adopted by Hehner and Mitchell. It is therefore absolutely necessary that each chemist using this method should ascertain the factor applying to his individual case by deter¬ mining the heat of bromination of a non-drying oil, the iodine value of which has been fixed by means of Hiibl’s method. Thus Jenkins 1 obtained the constant factor 5"7, and Archbutt 2 found it to vary in the case of tallow, olive oil, rape oil, and linseed oil from 5'7 to 6"2. In the latter case the variation may be partly due to the fact that the weight of substance taken was not the same in every instance. 1 Jour. Soc. Chem. Ind. 1897, 194. 2 Ibid. 1897, 310. Cp. also Wilson, Churn. Neivs, 1896, 27. CHAP. 302 EXAMINATION OF FATTY OILS AND LIQUID WAXES Notwithstanding the considerable differences shown in the case of linseed and rape oils, Hehner and Mitchell considered that the deter¬ mination of the iodine number by Hiibl’s method may be replaced by that of the heat of bromination. They even went so far as to express the opinion, that the calculated iodine values of linseed and rape oils examined are more correct than those found by Hubl’s method. In the writer’s opinion this is tantamount to begging the question, and a larger number of experiments is required to substantiate so far- reaching conclusions. This is all the more necessary as further serious deviations have been stated by Jenkins for Japanese wood oil, and for “blown oils.” On account of the exceeding simplicity of this test, and the rapidity in its execution, the heat of bromination test will prove a very useful auxiliary test, especially where a large number of specimens of the same kind have to be examined in a short time. It will be no less useful as a sorting test (Hehner), affording rapid information as to the class an oil belongs to. (Of course, if accuracy is required the iodine value must be determined as described above p. 172.) The great rapidity being one of the chief recommendations in favour of using this test, Wiley's 1 modification to employ a chloro- formic solution of bromine would seem to complicate matters, all the more so as a lowering of temperature takes place when bromine is dissolved in chloroform. The latter fact has already led to the suggestion to substitute carbon tetrachloride for chloroform. In the case of oils giving a very violent reaction, as linseed oil, Archbutt 2 suggests to work with 0'5 grm. of oil, and to multiply the result by 2, whilst in the opposite case, viz. of solid fats, which develop but little heat, to take 2 grms., and divide the result by 2. 5. The Discrimination of the Different Oils by “Quantitative Reactions ” The values obtained by the methods described in chap. vi. pp. 148-180, i.e. by the so-called quantitative reactions, furnish the most valuable indications as to the nature and purity of an oil. We consider here the following quantitative values :— (a) Saponification values. (b) Hehner values. (c) Reichert (Meissl) values. (d) Iodine (and Bromine) values. (e) Acetyl values. (a) Saponification Values The subjoined table contains the saponification values of a number of oils and liquid waxes, as determined according to Kottstorfer’s 1 Jour. Soc. Chem. Ind. 1896, 384. 2 /^_ ^897, 310. IX SAPONIFICATION VALUES 303 method by Allen, 1 Moore? De Negri and Fabris , 3 Lewkowitsch , 4 and other observers. The figures given in the column headed “Mean value ” do not always represent the actual means of the highest and lowest values recorded; in the case of the better known oils, the mean value is the number most frequently found. The classification in the following table is that adopted in the preced¬ ing pages, with subdivisions according to the plan arranged in chap, xi.: Saponification Values of Oils and Liquid Waxes Kind of Oil. 1 Grm. of Oil requires for Saponifi¬ cation Mgrms. KOH. Minimum. Maximum. Mean Value, Class of Oil. Sperm oil ... Arctic sperm oil (Bottlenose) 123 123 147 134 135 128-5 Liquid waxes. Menliaden oil . Sardine oil Japan fish oil . Pilchard oil Cod liver oil Haddock liver oil Skate liver oil . Shark liver oil Seal oil . Whale, northern oil Whale, southern oil Dolphin, body, oil Dolphin, jaw, oil Porpoise, jaw, oil Porpoise, fluid portion, oil 189-8 186 171 140 191-2 188-5 253-7 192-1 187 213-2 197-6 196 224 272-3 192 185- 5 190-9 186- 5 185 188-8 185-4 168 193-5 206 193-1 197-3 290 143-9 263 Fish oils. -Liver oils. Blubber oils. Linseed oil Japanese wood oil Lallemantia oil Hemp seed oil Walnut oil Poppy seed oil Niger seed oil Sunflower oil Fir seed oil Madia oil Garden rocket oil Henbane seed oil Celosia oil Indian laurel oil Cameline oil Soja bean oil . Pumpkin seed oil Maize oil . Kapok oil Cotton seed oil Sesame oil Beechnut oil . Brazil nut oil . 187-4 155-6 192-8 189 195-2 211 194-6 191 193 193 185 193-1 196 193-7 190 193 191- 3 192- 8 191-8 170-8 190-5 170 Drying oils. 192-5 188 191 187-6 191-1 192- 9 193- 4 210-5 192-2 196-3 188 192-7 188-1 1907 181 192- 5 190 193- 7 193-4 Semi-drying oils. 1 Jour. Soc. Cliem. Ind. 1883, 50. 3 Annali del Labomtorio delle Gabelle, 1893. 2 Chem News, 50. 268. 4 Cp. tables, chap. xi. 304 EXAMINATION OF FATTY OILS AND LIQUID WAXES CHAP. Saponification Vilues of Oils and Liquid Waxes — continued. Kind of Oil. 1 Grm. of Oil requires for Saponifi¬ cation Mgrms. KOH. Class of Oil. Minimum Maximum Mean Value. Garden-cress oil Hedge mustard oil . Rape oil. Black mustard oil . White mustard oil . Radish seed oil ... Jambo oil .... Charlock oil 175 174 170-3 176 179 174-6 171-4 177 178 174 177 174-3 170-8 178 172-26 176-5 Semi-drying Oils: Rape oil group. i 1 Castor oil | group. Croton oil .... Curcas oil .... Grape seed oil . Castor oil .... 210 210-2 178-4 176 215 230-5 179 186 212-5 220-3 178-7 183 Cherry kernel oil 193-4 195 194-2 Non-drying Cherry laurel oil 194 Apricot kernel oil . 192-2 193-1 192-7 Plum kernel oil 191-5 Peach kernel oil 189-1 192-5 190-8 Wheat meal oil 166-5 (?) Acorn oil. 199-3 Almond oil 187-9 190-4 191 Sanguinella oil ... 192 Californian nutmeg oil 191-3 Arachis oil 190-1 197 193-5 Rice oil . 193-2 Tea seed oil 194 195-5 194-8 Pistachio oil 191 191-6 191-3 Hazelnut oil 191-4 197-1 194-2 Olive oil . 185-2 196 193 Olive kernel oil 188-5 Coffee berry oil ... 165-1 173-4 169-3 Ungnadia oil . 191 192 191-5 Strophantus oil 187-9 Secale oil. 178-4 Sheep’s foot oil ... 194-7 Terrestrial Horses’ foot oil ... 195 196 7 195-8 animal oils. Egg oil. 185-2 186-7 186 Neat’s foot oil . 191 194-3 192-6 Lard oil . 191 196 193-5 A glance at the table shows that the saponification values, as given by different observers, do not agree very well, and further seiies of determinations, carried out with genuine oils, are required to ascertain within what limits the values vary for each kind of oil. Definite variations found could then be safely attributed to differences of soil, climate, etc. IX SAPONIFICATION VALUES 305 In the above table an attempt has been made to arrange the oils according to the system which appears to the writer to be the nearest approach to a natural one. Artificial classifications based on the saponification number are hardly of any value, if strictly carried through. Still, if judiciously used, the saponification value may give useful hints as to the class to which an oil of unknown origin may belong. The majority of oils have a saponification value of 193. A con¬ siderably lower number—such as 178—will justify the suspicion that the oil giving it belongs to the rape oil group. True, castor oil and grape seed oil are also distinguished by similarly low values, but they are easily differentiated from the oils of the rape oil group by their solubility in alcohol and acetic acid respectively, and chiefly by their acetyl values. The lower saponification values of these oils are easily explained by the large proportion of higher fatty acids they contain. Thus, rape oil is characterised by the glyceride of erucic acid, and castor and grape seed oils by glycerides of hydroxy acids. The low saponification values of the liquid waxes are so character¬ istic that they afford a ready means of distinguishing them from other oils. On the other hand, the high saponification values of the fluid portions of dolphin and porpoise oils (used for lubricating purposes) single them out in such a manner as to make their recognition com¬ paratively easy. Croton and curcas oils also are remarkable for their high numbers. With a view to eliminating the variations in the saponification values due to the presence of free fatty acids in the oils, Valenta has proposed to determine the saponification values of all the fatty acids, i.e. the total acid values. Obviously, the values so obtained will only lefer to the insoluble fatty acids of the oils. Therefore, the character¬ istic differences due to the presence of glycerides of soluble fatty acids will disappear. Thus, to choose a striking example, the difference of the saponification values of the fatty acids from butter and oleo¬ margarine respectively will be far less remarkable than the saponifica¬ tion values of the corresponding neutral fats. If, however, the differences of the saponification values of two oils under examination are due to a difference in the molecular weights of the fatty acids, the determination of the saponification values of the free acids will afford useful indications as to the nature of the oil. Thus, Valenta has obtained the following values :— Fatty Acids from Milligrms. KOH. Molec. Weight calculated. Cotton seed oil . 203-9 275-1 Olive oil ..... 203-0 276-0 Sesame oil . 199-3 281-5 The mean molecular weight of the rape oil fatty acids is 314. x 306 EXAMINATION OF FATTY OILS AND LIQUID WAXES chap. These molecular weights, howevei', must not be confounded with Allen’s Saponification Equivalents (p. 152), which are calculated from the saponification value, K, by dividing 5610 by K, the proportion of glycerol in the fat being disregarded. As already pointed out, Allen’s Saponification Equivalents furnish no further quantitative information than is given by the saponification values, and for this reason they are altogether omitted in this treatise. (b) Ilehner Values The Hehner values of the majority of the fatty oils are about 95. Only croton and curcas oils give lower numbers, viz. 88*9 and 87"9. With regard to the Hehner values of the liquid waxes compare chap. x. p. 329. (c) Reichert (Meissl) Values Most of the naturally-occurring fats contain but small quantities of soluble, i.e. volatile fatty acids, therefore their Reichert values are very low. As a rule they are below 1. It is evident, therefore, that a somewhat higher Reichert (Meissl ) value will be characteristic of an oil, and that very valuable indications as to the nature of an oil may be obtained by the determination of the volatile acids. Subjoined is a table containing those oils which possess Reichert or Reichert-Meissl values above 1. It must be understood that such oils as olive oil, cotton seed oil, etc., naturally fall outside the range of this list. Kind of Oil. Reichert Value, for 2 - 5 grins. Reichert-Meissl Value, for 5 grms. Observer. Sperm oil 1-3 Allen Arctic Sperm oil . 1-4 ,, Whale oil 3-7 „ Whale oil 12-5 Moore Dolphin oil, body 5-6 Dolphin oil, jaw . 65-92 Allen Porpoise oil . 11-12 Porpoise oil . 46-9 Steenbuch Porpoise oil, jaw oil, skimmed 47-77-56-00 Moore and strained Porpoise oil, jaw oil, skimmed 131-6 Steenbuch and strained Porpoise oil, jaw oil, not 2-08 Moore skimmed Croton oil 13-42 1 Lewkowitsch The extraordinarily high values of dolphin and porpoise oils are due to the presence of a large proportion of the glyceride of isovaleric acid. 1 Cp. also p. 313. IX IODINE VALUES 307 (d) Iodine (and Bromine) Values The subjoined table contains the iodine values of some oils as determined by the earlier observers Hiibl and Moore :— Iodine Value. Kind of Oil. Hiibl (mean values). Moore. Linseed oil 158 1 155-2 1 Drying oils Hemp seed oil 143 Walnut oil 143 Poppy seed oil 136 134 Pumpkin seed oil . 121 Semi-drying oils Cotton seed oil 106 108-7 Sesame oil 106 102-7 Arachis oil 103 87-4 Rape oil. 100 103-6 Apricot oil 100 Non-drying oils Almond oil (sweet) . 98"4 98-1 Mustard seed oil Castor oil 84-4 96-0 Olive oil 82-8 83-0 Olive kernel oil 81-8 Bone oil 68-0 As will be seen from this table, the drying oils, headed by linseed oil, are characterised by the highest iodine values, whereas the non-drying vegetable oils and bone oil, like other oils of terrestrial animals, possess distinctly lower values. The semi-drying oils occupy an inter¬ mediate place. The high absorptions of the drying oils are due to their containing large amounts of the glycerides of the linolenic acids and of linolic acid, which absorb 18 atoms and 12 atoms of iodine respectively, whereas the glycerides of oleic acid, the chief constituents of the non¬ drying oils, assimilate but 6 atoms of iodine. Consequently, the determination of the iodine value affords a very valuable and easily ascertainable characteristic in the examination of oils. Provided fish, liver, and blubber oils, possessing high iodine values but no drying properties, be absent, the mere determination of the iodine value allows of the discrimination of a drying oil from a non¬ drying one. It has, therefore, become customary, since the publication of Hull’s very useful method, to determine in the first instance the iodine absorp¬ tion of an oil under examination. Numerous determinations done by a great number of chemists prove that the iodine values of all oils are constant within narrow limits. Thus, Dieterich, on examining 200 1 Compare the correct value of the following table. 308 EXAMINATION OF FATTY OILS AND LIQUID WAXES chap. samples of olive oil, has found no greater variations than from 81 to 84‘5. In the case of linseed oil greater differences have been observed; but the apparent discrepancies have for the most part disappeared since it has been shown by Benedikt that a larger excess of iodine solution was required than had been used by Hubl and Moore. Besides, it must be borne in mind that the iodine values of linseed oil depend greatly on the age of the oil (comp. “ Linseed Oil,” chap, xi p. 341). In the following table I give the iodine values of oils and liquid waxes compiled from the publications of numerous observers, of whom the following may be mentioned:— Hubl, Moore, Dieterich, Wilson, Urban, Herz, Sputter, Horn, Richter, Kremel, Beringer, Benedikt, Archbutt, Micko, De Negri and Fabris, and Lewkowitsch. There are also added the bro¬ mine absorptions, as determined by Mills, Snodgrass, Akitt, and Maben ; 127 these values have been calculated to iodine values by multiplying by in order to facilitate comparison. 1 The oils have been arranged, as in the table given by Hubl, according to the magnitude of their iodine values, subject, however, to the keeping together of the members of some natural groups. This order has been carried through systematically by the writer for the members of the several groups in chap, xi., this system suggesting itself as the most natural one. Morawski and Demski (cp. p. 180) proposed to determine the iodine values of the mixed fatty acids. It has been pointed out already (p. 180) that a close correspondence between the iodine values of the oils and their (insoluble) fatty acids cannot be expected. It has, however, become customary in the commercial examination of fats and oils to ascertain also the iodine absorptions of the (insoluble) fatty acids as obtained on saponification. Therefore we have added in the sub¬ joined table the iodine values of the mixed fatty acids. Compare also tables, chap. xi. 1 It must be, however, understood that, a priori, these calculated iodine values need not be identical with those obtained by Hiibl’s process, the disagreement being no doubt due to the varying amount of substitution. This will be clearly seen from the following table containing the bromine and iodine values of a number of seal oils, determined by Chapman and Rolfe {Jour. Soc. Ohem. Ind. 1894, 843), to which I have added the calculated iodine values :— Seal Oil, No. Bromine Value. Iodine Value Experiment. Iodine Value calculated. 1 69-6 129-5 110-5 2 77-6 133-0 122-6 3 77-2 136-4 122-6 4 80'0 137-4 127-0 5 78-2 139-0 124-1 6 79-S 141-0 126-7 On the whole, the iodine values show greater regularity than the bromine values. IX IODINE VALUES 309 Iodine Values of Oils and Liquid Waxes, and of their Mixed Fatty Acids Kind of Oil. Oils. Mixed Patty Acids. Class of Oil. Bromine Absorption. Brx 127 Iodine Absorption. Iodine Absorption. Minim. Maxim. Mean. Minim. Maxim. Mean. 80 Linseed, fresh . . 76 120-8 170 181 175 Drying ,, commercial 148 181 170 155-1 182 179 oils. Japanese wood 156 166 161 150 Lallemantia. . . 162 166 Garden rocket . . 145-9 155-3 155-1 157 Hemp seed . . . 142 158 150 122 141 131-5 Walnut .... 132 152 146 150-5 Poppy seed . . . 50-5 89-9 134 142 138 116 139 Henbane seed . . 138 Niger seed . . . 35-1 55-S 133 Sunflower . . . 54-3 86-2 122 133 128 124 134 129 Celosia .... 126 Fir seed .... 118-9 120 119-5 121-5 Madia. 117-5 119-5 118-5 120-7 Candle nut . . . 118 Indian laurel . . 118-6 Sardine .... 193 Fish oils. Menhaden . . . 148 160 154 Japan fish . . . 96 122 109 Cod liver.... 81‘6-86-7 129-5-137-6 126 166-6 146-3 Liver Skate liver . . . 157-3 oils. Haddock liver . . 154-2 Coal fish liver . . 123 137 130 Shark liver . . . 84-36 133-3 90 114-6 102-3 Ling liver . . . 82-4 131 Seal. 57-3-59-9 91-95 125 152 138-5 Blubber Whale. 30-9 49 109-2 126-7 117-9 oils. Blackfish, body . 99-5 „ jaw 32-8 Porpoise, skimmed 30-9 49-6 40-2 ,, not skimmed 76-8 Cameline .... 132-6 135-3 133-9 136-8 Semi- Soja bean.... 121-3 122-2 121-7 115 122-2 118-6 drying Pumpkin seed . . 121 Oils. Maize. 66-5-74-4 105-5-118-1 111-2 119-9 115-6 113 125 119 Kapok. 116 108 Cotton seed . . . 50 79-5 102 111 108 110-9 115-7 113-3 Sesame .... 47-4 75-2 103 112 108 108-9 112 110-5 Beechnut . . . 65-2 103-5 104-4 111-2 107-8 114 Brazil nut . . . 106-2 108 Garden cress . . 108 108-8 108-4 111-4 Hedge mustard 105 Rape. 69-4 iio-4 99 105 101 96 105 100-5 Rape Black mustard. . 96 106 101 109-6 White mustard. . 92-1 97-7 94-9 94-7 95-9 95-3 Charlock .... 96 97 96-5 Radish seed . . . 95-6 95-9 95-7 97-1 Jarnbo. 95-2 95-6 95-4 96-1 96-2 96-1 Croton .... 46-7 74-1 101-7 104-7 103 r* i Curcas .... 100-9 127 113-9 105-5 Grape seed . . . 94 96-2 95-6 98-6 99 98-8 Castor. 58-3 92-7 83-6 85-9 84-7 86-6 93-9 90-2 J 310 EXAMINATION OF FATTY OILS AND LIQUID WAXES OHAP. Iodine Values of Oils and Liquid Waxes , and of their Mixed Fatty Acids—continued Oils. Mixed Fatty Acids. Iodine Absorption. Iodine Absorption. Class Kind of Oil. Bromine Br x 127 Oil. Absorption. 80 g g £ A *2 V. OS 05 s o3 Cherry kernel . . 110-8 114-3 112-5 104-3 114-3 109-3 ,, laurel . . Apricot kernel. . 118-9 112-1 70 iii-i 100 ids 104 102-6 103-8 103-2 Plum „ . . 100-2 100-4 100-3 102 104-2 103-1 Peach ,, . . Wheat meal . . . 25'4 40-4 92-5 99-7 96-6 94-1 101-9 98 101-5 Pine nut .... 101-3 Acorn. 100-7 Almond .... 26‘3-33'7 41-8-85-3 93 101-9 97-4 93-5 96-5 95 Sanguinella . . . 100-8 102-7 Californian nutmeg 94-7 Arachis .... 46-2 73-3 85-6 101-3 93-5 95 "5 103 99-2 Rice. 96-4 Tea seed .... 88 Pistachio.... 86-S 87-8 S7*4 88-9 Hazelnut.... 83-2 S8-5 85-8 90-1 Olive. 54-60-6 85-9-96-4 79-2 8S-7 82-8 86-1 90-2 88-1 „ kernel . . . Coffee berry. . . 81-8 85-89 87-34 86-5 78-65 88-8 90-4 89-6 81-8 Ben. 50-89-52-95 SO-8-84-1 81-5 82-0 81-7 Ungnadia . . . Strophantus seed . 73 Secale. 71 Sperm. Arctic sperm 54-5 S6'5 84 S3-2 85-6 84-4 Liquid waxes. (Bottlenose) . . 48-7 77-4 SO-4 82-1 81-3 82-2 83-32 82*7 Lard. 72-8 85 79 Sheep's foot. . . 74-0 74-4 74-2 Horses’ foot. . . 73-7 73-9 73-S animal Egg. 6S-5 SI-6 70 73 oils. Neat’s foot . . . 38-3 60-8 69-3 70-4 69-8 62 Bone. 67 70 68 The important place the iodine value occupies in the commercial examination of oils will he best illustrated by the following quotation from HubVs classic paper :— “ The determination of the iodine absorption furnishes a ready means of ascertaining the nature of an oil under examination, as it affords a standard by which we can gauge its purity, and by allowing conclusions to be drawn as to its qualitative composition; it will even permit it in some cases to be inferred approximately in what proportions two oils have been mixed. “ If it be required to identify an oil or fat, the iodine value will indicate the class to which it belongs, and it will then, as a rule, not be difficult to distinguish it from other oils and fats belonging to the same class by other characteristic reactions. It should, however, be IX IODINE VALUES 311 borne in mind that it is quite possible, nay, even likely, that some kinds of oils or fats may occur the iodine values of which may not lie within the limits given, since the values given above have been derived from but a limited number of samples. In such cases the connection existing between the iodine value and the melting point of the mixed free fatty acids will afford some indications as to the nature of the oil. “ If a mixture of two oils is under examination, one constituent of which is unknown, as in the case of an adulterated oil, or if the nature of either constituent be unknown, it will, of course, be required to utilise all those methods that are likely to throw some light on the nature of the components of the mixture. But even in such a case the iodine value of the mixture will furnish the first clue as to the order in which further tests, such as determination of the melting and solidifying points of the mixed fatty acids, of the saponification value, of the solubilities, and of other chemical and physical constants, have to be undertaken. “If the nature of two oils in a mixture be known, or if we have succeeded in identifying them, it is possible to approximately calculate the proportions of both oils in the sample if they belong to two different classes. Let x be the percentage of one oil and y the percentage of the other oil in the sample under examination, conse¬ quently x + y = 100, and further, let m be the iodine value of the oil x in the pure state, and n the corresponding value of the oil y, then we find from the iodine value J of the sample— _100( J -n) m - n “ The age does not materially affect the iodine absorption as long as the oil has not undergone any important change. Samples of linseed and rape oils, even fifteen years old, gave correct values. If, however, an oil has become thickened and rancid on exposure to light and air, the iodine absorption is diminished in a corresponding degree. Thus, an exposed linseed oil yielded 130, and an exposed olive oil but 75. 1 Oils thus changed are, however, characterised by their greater solubility in acetic acid, and by abnormally high per¬ centages of free fatty acids.” Ballantyne 2 has studied the influence of exposure to light and air on the iodine values of some oils. His results are recorded in the following table :— 1 An exposed olive oil, examined by the writer, absorbed 70 per cent of iodine. 2 Jour. Soc. Chem. Ind. 1891, 31. [Table 312 EXAMINATION OF FATTY OILS AND LIQUID WAXES CHAP. Kind of Oil. Original Value. After Six Months’ Exposure to Sunlight. Protected against Access of Air. Exposed to Air. Linseed oil 173-46 172-88 166-17 Cotton seed oil 106-84 106-40 100-12 Rape oil . 105-59 105-27 102-13 Arachis oil 98-67 97-60 93-20 Castor oil 83-63 83 "27 (after 2 months) 83-27 Olive oil . 83-16 82-64 78-24 The same fact is brought out by comparing the iodine values of the “ blown oils ” with those of the original oils (cp. table, chap. xii. p. 734). It is apparent that the action of both light and air is required to reduce the iodine value (cp. p. 11). Just as in the examination of a fat of unknown composition it is expedient to separate its constituents into a solid and into a liquid portion, it will be found useful to break up the fatty acids of an oil into a solid and a liquid part. For it is quite possible that two oils may absorb the same amount of iodine, whereas their liquid fatty acids may have very different iodine values. Such cases may be represented by two oils, one of which consists chiefly of triolein, and the other of trilinolin, tristearin, and tripalmitin. Wallenstein and Finch 1 have determined for a number of oils the iodine values of the liquid fatty acids (for which they propose the term “ inner ” or “ absolute ” iodine value of the oil (this term is not used in this work, as it may lead to confusion). Their numbers, contrasted with the iodine numbers of the oils themselves, are given in the following table :— Oil. Iodine Value of Oil. Iodine Value of the Liquid Fatty Acids. Niger seed oil. 133-5 147-5 Maize oil .... 122 140-7 Cotton seed oil—American 107-8-108 147-3-147-5 ,, ,, Egyptian 106-5-108 146-8-148-2 ,, ,, Peruvian 106-8 147-8 Rape oil . 101-1 120-7 Arachis oil ... 98-9 128-5 Tallow oil ... 92-2-92-7 Lard oil—European 2 95-2-96-2 ,, American 103-105 Cocoa nut oil . 8-4 54-84 1 Jour. Soc. Chevi. Ind. 1895, 97. 2 Ibid. 1897, 503. IX ACETYL VALUES 313 (e) Acetyl Values The determination of the acetyl value is especially suitable for the detection of castor oil, grape seed oil, and the “ blown oils.” The following acetyl values have been recorded by Lewkowitscli 1 :— Acetyl Value. Kind of Oil. (a) By Distillation Process. (6) By Filtration Process. Castor—I. . 150*5 149-6 „ II. . 149-9 149-4 ,, III. . 146-7 2 Croton—I. . 19-61 20-02 „ I. . 19-78 19-84 Maize—I. 8-75 8-25 I. . 8-21 „ II. . 7-81 7-9 Cotton seed —I. . 24-76 25-1 ,, II- • 21-1 III. . 21-9 Olive .... 12-78 13-48 Colza .... • 13-62 17-2 16-6 Linseed 6-85 6-92 Fish .... Shark liver . 7-03 41-0 17-83 Animal 22-04 22-38 Horses’ foot. 14-40 6. Qualitative Reactions Various colour reactions have been proposed from time to time, and are still being proposed, for the recognition of oils. A very complete synopsis of the older methods has been given by Chateau in his work On Fats. 3 The following tests may be mentioned in chronological order :— Heydenreich (1848) first employed concentrated sulphuric acid for the examination of oils ; his test consists in letting fall five drops of the oil under examination on the surface of pure concentrated sul¬ phuric acid in a porcelain basin, and observing the colours developed during the first three minutes. Penot introduced sulphuric acid saturated with potassium bichro¬ mate as a general reagent, the various colours obtained with different oils being considered as characteristic for those oils. Behrens used a mixture of equal parts of sulphuric and nitric acids. 1 Jour. Soc. Chem. Ind. 1897, 503. 2 The apparent acetyl values (p. 166) of croton oil, having a high Reichert value (p. 306), were found 40'68 and 40*85, from which 21 '07 had to be deducted for the volatile acids. 3 Chateau, Die Fet.te , bearbeitet von H. Hartnumn. Leipzig, 1864. 314 EXAMINATION OF FATTY OILS AND LIQUID WAXES chap. FaurS (1839) has stated that vegetable oils can be distinguished from animal oils by gaseous chlorine, the latter oils—with the excep¬ tion of foot oils from terrestrial animals—becoming black on treat¬ ment with this reagent (p. 279). The same chemist also employed ammonia as a general reagent. Hauchecour-Yvetot proposed hydrogen peroxide as a general re¬ agent. Crace Calvert’s (1854) method has for a long time been in vogue. This chemist examined the colour reactions noticeable on treating oils with the following reagents : (1) caustic soda, T340 spec. grav.; (2) sulphuric acid, T475 spec. grav.; (3) sulphuric acid, T530 spec. grav. ;. (4) sulphuric acid, T635 spec. grav. ; (5) nitric acid, IT80 spec, grav.; (6) nitric acid, T220 spec, grav.; (7) nitric acid, T330 spec, grav., and subsequently caustic soda, T340 spec, grav.; (8) syrupy phosphoric acid; (9) mixture of equal volumes of nitric acid, T330, and sulphuric acid, T345; (10) aqua regia, consisting of 25 measures of hydrochloric acid and 1 measure of nitric acid, 1*330, and subse¬ quent treatment with caustic soda. In the older text-books Crace Calvert’s results are presented in a tabular form; for reasons stated below the table is omitted in this work. Chateau , in his book On Fats , has published very extensive tables, in which an attempt is made to distinguish the oils by systematic application of the following reagents : (a) calcium polysulphide, ( b) zinc chloride, (c) concentrated sulphuric acid, (d) fuming stannic chloride, ( e ) syrupy phosphoric acid, (/) phosphoric acid, ( g ) mer¬ curic nitrate, with subsequent addition of sulphuric acid, ( h ) mercuric nitrate alone. All these tests must, on the whole, be considered of very little value, and are therefore not recorded here. Later on Glaessner also proposed a systematic course for the examination of oils, using as reagents caustic potash, fuming nitric acid, and concentrated sulphuric acid. In order to avoid a rise of temperature with the last-mentioned acid, whereby some characteristic colour reactions may become in¬ distinct, or the oil may become partially charred, Finkener dilutes the oils with carbon disulphide. This solvent is said to be specially adapted to the test, since no thermal reaction takes place on mixing it with concentrated sulphuric acid. All colour reactions must be used with the greatest caution, small quantities of resinoid or albuminoid substances, or other foreign matters, such as cholesterol, influencing the tints to such an extent that in most cases it will remain doubtful whether the reactions are due to the oils themselves or to the presence of small quantities of foreign substances. A notable example of a serious mistake of this kind was the reddish-brown colour obtained on treating imperfectly purified tallow with nitric acid being erroneously attributed to the presence of cotton seed stearine. The colour reactions were resorted to chiefly for want of better methods; they have been in most cases superseded by the “ quanti- IX QUALITATIVE REACTIONS 315 tative reactions.” It should be borne in mind that many colour reactions quoted in older text-books, and perpetuated in even more recent treatises, were not always obtained with typical samples, little or no regard having been paid to their source, their age, their mode of purification, and all that host of circumstances that have a vital influence on the colour the reagents produce. With the progress of technology a number of impurities, the very substances that gave origin to the colours supposed to be characteristic, have ceased to occur in commercial samples. A colour reaction can only be of value if it be produced by a well- defined substance, naturally occurring in an oil, and characteristic of it to such an extent that the oil may be identified by that reaction. Of course, these characteristic substances occurring only in minute quantities must not be easily removable by the process usually applied in practice. As a type of a most valuable reaction of this kind we may refer to BoMdouin’s test for sesam6 oil which has recently obtained its scientific explanation and confirmation by the isolation of the colour- producing principle in that oil (cp. “ Sesamb Oil,” p. 389). The colour reaction for cholesterol, although highly characteristic, requires more circumspection, as other substances also give the same or a very similar colouration (p. 84). Group reagents, such as are used in inorganic analysis, do not exist, and every new reagent recommended as such must be received with great suspicion. The writer 1 has carefully examined four of the so-called group reagents, viz. concentrated sulphuric acid, gaseous chlorine, syrupy phosphoric acid, and phospho-molybdic acid. From his experiments the following conclusions have been arrived at :— Sulphuric Acid .—This reagent enables, at best, with a gqod deal of practice, to discriminate between drying oils, semi-drying, and non¬ drying oils, if the acid be applied to the oil direct. The first-named oils may be recognised by their forming dark clots, when, say, two drops of concentrated acid are stirred into twenty drops of oil. A discrimination between semi-drying and non-drying oils, however, is more difficult and indeed scarcely possible in every case. The better drying an oil is, the darker it will be coloured by the acid, so that it may be possible, judging from the depth of the colour, to distinguish between oils standing at the extreme ends of these classes, such as cotton seed oil and olive oil, whereas it is impos¬ sible to differentiate by this test alone, e.g. rape oil from cotton seed oil. The colour reactions obtained with a solution of the oil in carbon bisulphide cannot be said to yield more reliable results, the dilution tending to obliterate the otherwise sharp distinction between the eminently drying and the other oils. In the case of liver oils, the blue and purple colourations due to the presence of cholesterol and colouring principles—lipochromes— are very characteristic; they are best observed if the oil is previously 1 Lewkowitsch, Jour. Soc. Chem. Ind. 1894, 617. 316 EXAMINATION OF FATTY OILS AND LIQUID WAXES CHAP. dissolved in carbon bisulphide. But the value of this test is greatly diminished by the fact that some blubber oils (perhaps due to an accidental admixture tvith liver oils) show the same reaction, but chiefly for the reason that rancidity seems to destroy the chrormo- genetic substances. Chlorine gas cannot be admitted as a group reagent for marine animal oils, the black colour being influenced by the state of purity and rancidity of the oil, so that even vegetable oils or terrestrial animal oils may give stronger colourations than pure liver oils. Phosphoric acid appears to indicate only impurities that may be eliminated by refining, or that are products of oxidation or rancidity. Phospho-molybdic Acid. —This reagent has been proposed by Welmans. 1 The test is performed as follows : 1 grm. (or 25 drops) of an oil or fat is dissolved in 5 c.c. of chloroform in a test-tube, and agitated with 2 c.c. of a freshly prepared solution of phospho- molybdic acid, 2 or of sodium phospho-molybdate and a few drops of nitric acid. After standing for a short time the chloroformic layer becomes colourless, whereas the upper layer shows, in the case of a vegetable oil and of cod liver oil, according to Welmans , a green colour. On adding ammonia or a fixed alkali a beautiful blue colour appears, the intensity of which corresponds to that of the green tint noticed before. Animal fats—with the above stated exception of cod liver oil—were said to cause no reduction, and consequently to pro¬ duce no green with subsequent blue colouration. The writer’s experiments, 3 however, demonstrate that such a dis¬ tinction cannot be upheld. Several kinds of olive oil, as also almond, arachis, and peach oils, showed far less distinct colours than tallow oil, and even lard oil. Amongst the large numbers of oils and fats of undoubted genuineness and belonging to all classes of oils and fats he has examined, only pure, freshly rendered lard left the phospho- molybdic acid unreduced, so that it remained colourless on being supersaturated with ammonia. But a slightly rancid lard behaved almost like a vegetable oil in Welmans’ test (cp. “Lard,” p. 580). Moreover, mineral oil and resin oil gave deep colourations; the phospho-molybdic acid test can, therefore, only rank amongst pre¬ liminary tests. Special colour reactions, useful in some instances for the identi¬ fication of an oil or for the detection of an adulterant, will be exhaustively dealt with in the chapter treating of the distinctive properties of the individual oils and fats. 1 Jour. Soc. Ghevi. Ind. 1892, 548. 2 The reagent is prepared by precipitating a solution of ammonium molybdate with sodium phosphate, washing the precipitate thoroughly and dissolving it in a warm solu¬ tion of sodium carbonate. The solution is boiled down to dryness and the residue heated. If the residue becomes coloured blue, add a few drops of nitric acid and heat again. Then boil the residue with water, add nitric acid until strongly acid, and dilute so as to obtain a 10 per cent solution. Filter if necessary and keep the reagent pro¬ tected from dust. 3 Lewkowitsch, Jour. Soc. Ohem. Ind. 1894, 619. IX ANIMAL AND VEGETABLE OILS 3i 7 Distinction between Oils of Animal and Vegetable Origin A frequently occurring problem in commercial fat analysis is to detect vegetable oils in oils of animal origin. It has been shown in the preceding pages that the colour reactions are of very limited value. The methods described below may, how¬ ever, in some cases lead to definite results if used judiciously. They are based on the fact that (a) the vegetable oils, with the exception of olive oil, contain appreciable quantities of phytosterol, whereas animal fats—butter fat, however, excepted—are free from it, they in their turn being characterised by presence of cholesterol; and ( It) that all vegetable oils and also the vegetable fats hitherto examined contain linolic acid, yielding on oxidation sativic acid; whereas oils of animal origin—excepting the fish, liver, and blubber oils—as a rule contain no other unsaturated acid than oleic acid. This rule, how¬ ever, breaks down in the case of oils from animals fattened with oleaginous substances (as linseed cakes, maize), notably so in the case of American lard oil (cp. also p. 332). (1) Cholesterol or Phytosterol Test. 1 —50 grms. of the sample are saponified with alcoholic potash; the soap solution is diluted with 1000 c.c. of water and exhausted with ether. When the two layers have separated, the aqueous layer is run off and the ethereal liquid filtered and evaporated to a small bulk. .To ensure complete absence of unsaponified fat, it is best to saponify again with alcoholic potash, and to repeat the exhaustion with ether. The ethereal layer is then washed with water and the ether evaporated in a deep basin. This method being somewhat cumbersome, it will be found prefer¬ able to boil out 50 grms. of the sample twice with 95 per cent alcohol, using 75 c.c. each time, then to pour off the alcoholic layers and to saponify only the dissolved portion. 2 The saponified mass is then extracted with ether. The residue left after evaporating off the ether is next dis¬ solved in hot alcohol, the solution boiled down to 1 to 2 c.c., and the residue allowed to cool. If phytosterol or cholesterol be present, crystals will separate out. They are dried on unglazed porcelain and their melting points determined. If the sample consisted of a mixture of animal and vegetable oils, as a rule, almost pure phytosterol, melting point 132°-134° C., will be obtained. In the case of, say, an unadulterated cod liver oil the crystals will be pure cholesterol, melting point 146° C. A cod liver oil adulterated with vegetable oils will yield crystals melting at, say, 139°-140° C.; in this case microscopic examination is necessary, and the colour reaction with sulphuric acid (p. 315) must be resorted to. (2) Iodine Value of the Liquid Fatty Acids. 3 —Provided fish, liver, and blubber oils are absent (which may be ascertained by the absence of the peculiar smell and taste of these oils), the determination of the 1 Salkowski, Jour. Soc. Chem. Ind. 1888, 37. 2 Forster and Riechelmann, Zeits. offentl. Chemie, 3, 10 ; cp. also Lewkowitscli, Jour. Soc. Chem. Ind. 1892, 136 ; and above, chap. vii. p. 230. 3 Muter and Koningh, Analyst , 1889, 61 ; and Wallenstein and Finck, Jour. Soc. Chem. Ind. 1895, 79. 318 EXAMINATION OF FATTY OILS AND LIQUID WAXES chap, ix iodine value of the liquid fatty acids of the sample will furnish the information whether vegetable oils are present. As will be seen from the table giving the iodine values of the liquid fatty acids (p. 312), the vegetable oils, with the exception of cocoa nut oil and palm nut oil, give higher numbers than the animal oils. Tallow oils 1 have almost the theoretical value of oleic acid—90—whereas lard oils vary from 95 to 105 according to their origin. 2 Now, if the iodine value of the liquid fatty acids of a sample be found above 105, it is certain that vegetable oils are present. If numbers lying between 95 and 105 be found, there may be an admixture of a vegetable oil; in such a case Wellman's reaction may perhaps be of some help. But if the iodine value of the liquid fatty acids be below 90, then there must be an admixture of cocoa nut oil, provided no unsaponifiable oil be in the sample to a notable extent (cp. “Edible Fats,” chap, xii., and “ Detection of Cotton Seed Oil in Lard ”). It will thus be seen that the opinion held for some time that terrestrial animal oils con¬ tain oleic acid only is erroneous, and that we must therefore assume the presence of small quantities of less saturated fatty acids. This has become a certainty since Kurbatoff 3 has proved the presence of linolic acid in the fat from the common hare, the white hare, the Caspian seal, the sturgeon, and the shad-fish, and, furthermore, since Fahrion has obtained sativic acid from lard—cp. (3), and Amthor and Zink have discovered drying fats (p. 331). (3) Sativic Acid Test. Benedikt and Hazura’s method.—50 grms. of the liquid fatty acids are oxidised with potassium permanganate (p. 141); the solution is then acidified, the liberated fatty acids extracted with ether, and boiled out repeatedly with water. A turbidity appearing in the filtrates on cooling does not neces¬ sarily prove the presence of sativic acid, since small quantities of soap retained by the precipitated acids may have passed into the filtrate causing opalescence. Again, if a few drops of dilute sul¬ phuric acid have been added to the water employed for washing, in order to decompose the soap, a little dihydroxy stearic acid, the oxidation product of oleic acid, will be dissolved. The latter, how¬ ever, may be easily distinguished from sativic acid by its melting point and crystalline habitus. Benedikt and Hazura were unable to obtain sativic acid from lards rendered by themselves, although they very carefully looked for this substance. The specimen of lard examined by Fahrion yielded, how¬ ever, sativic acid; this confirms the observation frequently made that the food taken by an animal has a considerable influence on the composition of its fat. Further research must decide whether vegetable oils can be readily distinguished from animal oils by means of the oleo-refradometer (cp. p. 263). 1 Fileti and Baldracco ( Ghern. Zeit. 1896, 239) could not obtain from tallow oleic acid the tetrachlorostearic acid readily yielded by almond oil “ oleic ” acid. 2 American lards show higher iodine values than European lards, because in America hogs are fattened with maize. 3 Berichte, 25, Abstracts, 506. CHAPTER X APPLICATION OF PHYSICAL AND CHEMICAL METHODS TO THE SYSTEMATIC EXAMINATION OF SOLID FATS AND WAXES The fats and waxes considered in this chapter may be recognised chiefly by the following definite characteristics :— 1. Specific gravities. 2. Melting and solidifying points of the fats or waxes. 3. Melting and solidifying points of their fatty acids. 4. Behaviour with solvents. 5. Hehner values. 6. Reichert ( Meissl ) values. 7. Saponification values. 8. Iodine values. Further information may be gathered from the acetyl values, thermal tests, and refractive indices. The consistency, colour, degree of transparency, etc., will, as a rule, give some clue as to the nature of a fat. As to the consistency at ordinary temperature, the various grada¬ tions between the butters, lards, and hardest fats will help to limit con¬ veniently the range of substances to which examination may extend. The colour of most fats is almost white or yellowish. However, palm oil in its crude state will always be easily recognisable by its red colour, shea butter by its grey or greenish-grey colour, and laurel oil by its yellowish-green colour. The examination of the unsaponifiable matter will also furnish valuable information in many instances, as notably in the case of waxes. Many semi-solid or solid fats may be separated by pressure, at the ordinary or slightly higher temperature, into a fluid portion and a solid fat, possessing a higher melting point than the original substance. The separate examination of the two constituents may lead to important conclusions, especially in the case of adulterated samples (see “ Beef Tallow ”). Beactions affording means of detecting vegetable oils in animal fats have been pointed out above (p. 317). The most reliable method consists in the determination of the iodine value of the liquid 320 SYSTEMATIC EXAMINATION OF SOLID FATS AND WAXES chap. fatty acids. 1 The sativic acid method is more tedious. It may be mentioned that Benedikt and Hazura have obtained from the liquid fatty acids of palm oil and cacao butter 0‘6 and 0’5 per cent respect¬ ively of sativic acid. It should, however, be noted that palm oil, in contradistinction to most vegetable oils, is free from phytosterol. 1. Specific Gravities of Solid Fats and Waxes The recorded specific gravities of fats vary to a considerable ex¬ tent, as will be seen from the values given for each individual fat in the following chapter. In order to give a synopsis I subjoin several tables. The following table summarises the results obtained by Hager and Dietericli for some solid fats and allied substances likely to be met with (as adulterants) in fats :— Specific Gravities of Solid Fats and Wtaxes at 15° C. Kind of Fat. Hager. Dietericli. Beef tallow ..... 0-925-0-929 0-952-0-953 Fats Butter fat (clarified) 0-938-0-940 ,, ,, (several months old) Artificial butter .... 0-936-0-937 0-924-0-925 JJ >> . • • • Lard (fresh). 0-925-0-930 0-931-0-932 ,, (old) . 0-940-0-942 0-961 Mutton tallow .... Mixed beef and mutton tallow (equal 0-937-0-940 parts). 0-936-0-938 0-980-0-981 Cacao butter (fresh) .... 0-950-0-952 ,, ,, (very old) Nutmeg butter .... 0-945-0-946 0-965-0-966 Japan wax . 0-977-0-978 0-975 „ „ (very old) 0-963-0-964 Beeswax (yellow) .... 0-959-0-962 0-963-0-964 Waxes ,, (African) .... 0-960 0-973 ,, (white) .... Spermaceti ..... 0-919-0-925 0-960 Stearic acid (fused) .... 0-964 0-971-0-972 Solid substances ,, ,, (crystallised). 0-967-0 969 0-918 met with as ad- Ceresin (perfectly white) . 0-905-0-908 mixtures. ,, (half white) .... 0-923-0-924 0-920 „ (yellow) .... Paraffin wax. 0-925-0-928 0-922 0-913-0-914 Ozokerit (crude) .... 0-952 Pine resin (purified) 1-045 Colophony (American) 1-100 1-108 ,, (French).... 1-104-1-105 1 This statement must be qualified, since “drying” animal fats (cp. chap. xi. p. 331) have been detected. X SPECIFIC GRAVITIES 321 For the reasons stated (chap. v. p. 128) it is more convenient to determine and compare the specific gravities of the solid fats at higher temperatures, i.e. in their liquid state. The following table, due to Allen, gives the specific gravities of solid fats and waxes arranged according to their specific gravities at the boiling point of water :— Class of Fat, Wax, etc. Specific Gravity at 98° 0.-100° C. (Water 15 - 5° C.=l.) 0-750 to 0-800. 0-800 to 0-855. 0-S55 to 0-863. 0-863 to 0-867. Vegetable fats . Palm oil Cacao butter Palm nut oil ( Cocoa nut oil Japan wax Myrtle wax Manufactured. Cocoa nut stearine Cotton seed stearine Animal fats Tallow Lard Bone fat Manufactured. Oleomargarine Butterine Butter fat 0 Waxes Spermaceti Beeswax Chinese wax Carnaliba wax Fatty acids Stearic acid Palmitic acid Oleic acid Hydrocarbons . Paraffin wax Ozokerit Shale products Petroleum products Vaseline Dividing the fats into two groups, according to presence or absence of glycerides of soluble fatty acids, we obtain the two following tables. The values are due to Allen and to Konigs. Y [Table 322 SYSTEMATIC EXAMINATION OF SOLID FATS AND WAXES chap. A. Fats, Free from Glycerides of Soluble Fatty Acids Class of Fat. Kind of Fat. Specific Gravities at 100° C. (Water at 15° C. = 1.) Vegetable Fats Cacao butter CF857 Palm oil 0-857 Japan wax 0-8755 Animal Fats Lard 0-861 Tallow (beef and mutton) 0-860- Horse fat 0-861 Oleomargarine 0-859 B. Fats, containing Glycerides of Soluble Fatty Acids Class of Fat, Wax, etc. Kind of Fat. Specific Gravities at 100° C. (Water at 15° C. =1.) Vegetable fats Cocoa nut oil Palm nut oil 0-8736 0-8731 Animal fats .... Butter fat 0-865-0-868 On comparison, it will be seen that the specific gravities of the fats belonging to group B are higher than those of group A. Allen has determined the specific gravities of a number of fats at two distant temperatures, and calculated from them the differences per 1° C., by means of which specific gravities determined at tem¬ peratures other than the normal temperatures may be reduced to the latter. As pointed out already, Allen has calculated the expansion coefficients of the fats from these differences. [Table X SPECIFIC GRAVITIES—MELTING POINTS 323 Specific Gravities of Melted Fats, Waxes, etc., at 40° to 90° 0., and at 98°- 99° C. Kind of Fat, Wax, etc. °C. Specific Grav. (Water at 15-5° C. =1.) °C. Specific Grav. (Water at 15'5° c. = 1 .) Difference per 1° C. Palm oil ... 50 0-8930 98 0-8586 0-000717 Cacao butter . 50 0-8921 98 0-8577 0-000717 Japan wax 60 0-9018 98 0-8755 0-000692 Tallow .... 50 0-8950 98 0-8626 0-000675 Lard .... 40 0-8985 98 0-8608 0-000650 Oleomargarine 40 0-8982 98 0-8592 0-000672 Butter fat 40 0-9041 99 0-8677 0-000617 Cocoa nut oil 40 0-9115 99 0-8736 0-000642 Palm nut oil . 40 0-9119 99 0-8731 0-000657 Spermaceti 60 0-8358 98 0-8086 0-000716 Beeswax 80 0-8356 96 0-8221 0-000750 Carnaiiba wax 90 0-8500 98 0-8422 0-000975 Stearic acid (commercial) 60 0-8590 98 0-8305 0-000750 Oleic acid (commercial) . 15-5 0-9032 99 0-8484 0-000656 Paraffin wax . 60 0-7805 98 0-7530 0-000724 2. Melting and Solidifying Points of Solid Fats and Waxes The melting and solidifying points recorded in the following tables vary considerably; these variations may be due to the varying condition of the fats, the irregularities during the melting and solidifying, and, lastly, discrepancies inherent to the methods employed. The following table contains the observations of Wimmel, Pdidorff, Bensemann, Allen, and others. (Cp. also the tables given, chap, xi., for the individual fats.) [Table Melting and Solidifying Points of Fats and Waxes 324 SYSTEMATIC EXAMINATION OF SOLID FATS AND WAXES chap. Oa •Oo - WO t>o m -a •0. 'W°d gutAjipnog ’Do 'inioj WlOO Sts •Do 0^ Smsu 'duiax CO 5! ‘5 >>£?-§ « =S.£+3 S & Cj ^ O C •rH m ^ R > ^ •Oo 'W\o& Sni^9j\[ L- o 9 °? (M o ■* °?3"s JS rC 22 * 3 u &-T _ „ i> «b Woo ®INO Jour. Soc. Chem. Ind. 1890, 744. X TITER TESTS 327 The melting and solidifying points of the mixed fatty acids of the most important commercial fats, as tallow and palm oil, will be dealt with in the following two chapters (cp. p. 519). The writer recommends as the most reliable method, especially for the commercial valuation of fats, the determination of the “ titer test.” The following table gives the results collated from a very large number of observations made by the writer during a number of years :— Titer Tests of Mixed Fatty Acids ( Lewkowitscli) Class of Fat. Kind of Fat. Titer Test. Remarks. Vegetable fats Cotton seed stearine Chaulmoogra oil Laurel oil Mowrah seed oil Shea butter Vegetable tallow 1 Palm oil, Bonny ,, Bassam ,, Lagos ,, Old Calabar ,, Salt Pond ,, New Calabar ,, Congo Macassar oil Sawarri fat Nutmeg butter Cacao butter 34- 9 -35-1 39'5 -39-6 14-3 -15-1 38-3 -38-5 5375-53-8 52-1 -53-4 35- 8 -35-9 38-0 -38-47 43- 8 -43-925 44- 3 -44-6 44- 3 -44-475 45- 4 -45-55 44-9 -45-05 51-6 -53-2 46- 0 -47-0 35-5 -35-95 48-0 -48-27 Palm nut oil 20-0 -20-5 Lowest 99 99 Cocoa nut oil, commercial 24-6 -25-5 Highest 21-2 -22-55 Lowest 9 9 9 ,, Cochin 24-8 -25-2 24-8 -25-2 Highest Japan wax 58-8 -59-4 Animal fats Horse fat Horse marrow 33-6 -33 7 38-4 -38-55 Lard 41-45-42-0 Beef tallow, English 38-45-387 Lowest ,, ,, North American 45-0 -45-1 Highest 38-9 -41-1 Lowest 99 99 99 99 ,, ,, South American 43-3 -44-15 Highest 4275-42-95 Lowest 9 9 9 9 9 9 < 9 9 ,, ,, Australian 45-7 -46-25 Highest 37-9 -38-3 Lowest 9 9 9 9 99 Mutton tallow, English 43-05-43-3 Highest 40-15-41-5 Lowest ,, ,, Australian 47-5 -48-3 Highest 41-65-42-35 Lowest Beef marrow 47-8 -48-05 Highest 37-9 -38-0 1 Commercial. 328 SYSTEMATIC EXAMINATION OF SOLID FATS AND WAXES chap. 4. Behaviour with Solvents Dubois and PacU have studied the solubility of some solid fats in benzene and of their mixed fatty acids in absolute alcohol. Their observations are given in the following two tables :— Solubility of Solid Fats and Benzene Kind of Fat. 100 grins, of Benzene dissolve at 12° C. Grins. Mutton tallow 1470 Beef tallow .... 15-89 Yeal tallow .... 26-08 Lard .... 27-30 Butter fat 69-61 Margarine .... 12-83 Solubility of Mixed Fatty Acids in Absolute Alcohol Mixed Fatty Acids from 100 Grms. of absoli: at 0° C. te Alcohol dissolve at 10° C. Grms. Grms. Mutton tallow .... 2-48 5-02 Beef tallow .... 2-51 6-05 Veal tallow .... 5-00 13-78 Lard ..... 5-63 11-23 Butter fat .... 10-61 24-81 Margarine .... 2-37 4-94 The indications furnished by Valenta’s test are less characteristic than those recorded in the last two tables. Valenta’s turbidity tem¬ peratures for some of the solid fats have been given already (p. 271). (Cp. also “Butter Fat,” p. 619). 5. Hehner Values The Hehner value for the majority of solid fats lies between 95 and 96. The following fats containing considerable quantities of glycerides of soluble fatty acids form notable exceptions :— Kind of Pat. Butter fat Cocoa nut oil . Palm nut oil . Mocaya oil 1 . Hehner Value. 87-5 89-6 91-1 1 Although the Hehner value has not been determined, yet there can be no doubt but that the value in this case will lie in the neighbourhood of 90. X REICHERT VALUES—SAPONIFICATION VALUES 329 On saponifying waxes, such as beeswax and wool wax, the fatty substance separating on acidulating the alcoholic solution consists of a mixture of fatty acids and (unsaponifiable) insoluble alcohols. Therefore, in these cases an apparent Hehner value of more than 100 will be found, water having been assimilated during the saponifi¬ cation. In order to find the real Hehner value, it is necessary to separate, by shaking with ether, the alcohols from the soap solution, and to acidulate the latter. The Hehner value, however, is not taken in the case of waxes, other characteristics more readily enabling us to distinguish them from glycerides. 6. Reiehert-Meissl Values The Reichert-Meissl value of most fats and waxes lies below 1 ; the following exceptions are notable, the Reiehert-Meissl value serving in these cases as a most valuable means of identifying and readily distinguishing them from other fats. Kind of Fat. Butter fat Cocoa nut oil Mocaya oil . Palm nut oil Reiehert-Meissl Value. . 28 7 7 5 7. Saponification Values Most solid fats have saponification numbers varying from 195 to 197, only the saponification values of butter fat, cocoa nut oil, probably also Mocaya oil, and palm oil are exceptionally high. The four fats forming the exception are recorded in the following table :— Kind of Fat. Butter fat Cocoa nut oil Palm nut oil Mocaya oil 1 Mean Saponification Value. 227 255 247 The saponification values of all the waxes are considerably lower, as shown in the following table:— Kind of Wax. Insect wax Carnaiiba wax Beeswax . Wool wax Spermaceti Mean Saponification Value. 63 . 79-95 . 97-107 102-4 129 8. Iodine (and Bromine) Values The iodine (and bromine) values of the solid fats and waxes, and their mixed fatty acids, as far as they have been determined, are collated in the following table. The means given do not always represent the actual means (cp. p. 303):— 1 Not determined yet, but it is very likely that the value will be about 250. Iodine (and Bromine) Values of Solid Fats and Waxes, and of their Mixed Fatty Acids 330 SYSTEMATIC EXAMINATION OF SOLID FATS AND WAXES chap. Iodine {and Bromine ) Values of Solid Fats and Waxes, and of their Mixed Fatty Adds — continued. x IODINE VALUES 331 332 SYSTEMATIC EXAMINATION OF SOLID FATS AND WAXES chap. The liquid fatty acids of the animal oils were until recently con¬ sidered to consist of oleic acid only, and this was thought naturally to constitute an important difference between vegetable and animal fats. It has, however, been proved that some animal fats contain less saturated fatty acids than oleic, notably so, lard, and especially American lards. It is very likely that the less saturated acid is linolic acid, as Fahrion obtained sativic acid on oxidising the liquid fatty acids from lard. In the case of hare fat, in which also linolic acid has been proved to be present by Kurbatoff, the iodine value is as high as 102*2, and in the case of blackcock fat it rises to 12IT. It is therefore not surprising that the hare fat should exhibit drying properties; black¬ cock fat, however, although possessing the higher iodine number, has less marked drying properties than hare fat. Also two other animal fats, viz. that of the wild rabbit and of the wild boar, dry on exposure to the air, so that in a similar fashion to the subdivision of oils into drying and non-drying oils we may classify the animal fats into dry¬ ing fats and non-drying fats. The former would in some sense correspond to the oils of marine animals. Nor is there wanting a fat forming, as it were, the intermediate link between the drying and the non-drying fats. This is represented by wild boar fat, whereas the ordinary lard has no drying properties whatever at the ordinary temperature. The high iodine values of the American lards are due to the mode of fattening the hogs in the United States. The iodine values of fats from cattle fed on oil cakes is higher than those fed on grass, from which one may conclude that domestic animals yield fats richer in olein than wild animals. The contrary, however, appears to be true, judging from several determinations made by Amtlior and Zink. 1 These are given in the following table :— Fat from Iodine Value. Rabbit, wild .... 101-1 tame .... 64-4 Goose, wild .... 99-6 J J wild, held in captivity 2 years . 67-0 > > domestic.... 67-6 Duck, wild .... 84-6 > J domestic .... 58-5 Hog, wild boar 76-6 ,, domestic 63 (max.) Cat, wild .... 57-8 J ? domestic.... 54-5 line value of the liquid fatty acids has become of the greatest importance in the examination of the animal fats used as edible fats. For this reason the numbers given in the following table will be found useful:— 1 Zeits.f. analyt. Cliemie, 1897, 1. X ACETYL VALUES—REFRACTIVE INDEX 333 Kind of Fat. Iodine Value of Liquid Fatty Acids. Observer. Cocoa nut oil 54-0 Wallenstein and Finck Tallow, beef 92-2-92-7 >> Lard, European . 95-2-96-6 ,, ,, ,, ,, home rendered . 90 Dietericli ,, American . 103-105 Wallenstein and Finck ” ” 97-8-103-2 Raumer 9. Acetyl Values The determination of the acetyl values is hitherto of little use in the examination of solid fats. The following numbers have been determined by LewJcowitsch 1 :— Fat. Cocoa nut oil Beef marrow Tallow Butter Horses’ foot oil Acetyl Value. o-o 4- 2 5- 4 O'O * . 9-1-10-3 Thermal Tests. — Mavmend’s thermal reaction test is but rarely employed in the examination of solid fats. It has, however, been used with advantage for the detection of vegetable oils in lard and butter fat. The heat of bromination test is likely to supersede the Maumene test on account of the shorter time required to carry out the operation (cp. p. 300). For the sulphur chloride test compare chap. ix. p. 282, and under “ Lard,” chap. xi. p. 582. The refractive indices of several fats and of their fatty acids, determined by Tliurner , 2 are given in the following table :— Kind of Fat. Refractive Index at 60° C. of the Fat. of the Mixed Fatty Acids. Palm oil 1-4510 1-4441 Cacao butter 1-4496 1-4420 Palm nut oil 1-4431 1-4310 Cocoa nut oil 1-4431 1-4295 Lard . 1-4410 1-4395 Tallow, Beef 1-4539 1-4375 ,, Mutton . 1-4510 1-4374 Butter 1-445-1-448 1-437-1-439 Margarine . 1-443-1-453 1-443-1-444 For further information under this head cp. “Lard” (p. 577) and “Butter” (p. 623). 1 Jour. Soc. Chem. Ind. 1897, 506. Other acetyl values recorded for fats have been omitted as being evidently incorrect (cp. Butter Fat, p. 604). 2 Ibid. 1895, 43. CHAPTER XI DESCRIPTION OF NATURAL FATS AND WAXES : METHODS OF EXAMINING THEM AND DETECTING ADULTERATIONS We now come to the consideration of the individual natural fats and waxes, arranging them according to the classification adopted in the two preceding chapters. The tables appended will he found to give in a handy form the physical and chemical constants of each fat and wax, as recorded by the various observers, and also the variations, within narrow limits, of these constants as found in the examination of different specimens of the same kind of fat or wax,—due to the difference of age, source, mode of preparation, etc. It is hoped that by following this plan the analyst will have placed in his hand a ready means of identifying any unknown fat or wax that he may have to examine. The methods followed in testing for adulteration will also be found fully described in each case. It should be mentioned that the writer has very carefully examined the various colour reactions that have been proposed from time to time (see chap. ix. p. 313), and, as the result of his investigations, many of those reactions usually found in text-books have been omitted as worthless. As the order in which the fats and waxes are enumerated here is determined by the iodine value, a number of these values had to be ascertained by the writer. The subject matter will be found arranged under two principal divisions and a number of subdivisions. A. OILS AND FATS. GLYCERIDES I. OILS OR LIQUID FATS 1. VEGETABLE OILS (1) Drying Oils (2) Semi-drying Oils (3) Non-drying Oils CHAP. XI CLASSIFICATION OF FATS AND WAXES 335 2. ANIMAL OILS (1) Marine Animal Oils a. Fish Oils (3. Liver Oils y. Blubber Oils (2) Terrestrial Animal Oils II. SOLID FATS 1. Vegetable Fats 2. Animal Fats B. WAXES. NON-GLYCERIDES I. LIQUID WAXES II. SOLID WAXES 1. VEGETABLE WAXES 2. ANIMAL WAXES 336 GLYCERIDES—DRYING OILS CHAP. A. OILS AND FATS. GLYCERIDES I. OILS OR LIQUID FATS 1. VEGETABLE OILS (1) Drying Oils The general characters of drying oils have been described already (p. 279). The following are the most important drying oils con¬ veniently arranged according to their iodine values, as approximately indicating the order of their drying powers : Linseed oil, Japanese wood oil, Lallemantia oil, hemp seed oil, walnut oil, poppy seed oil, Niger seed oil, sunflower oil, fir seed oil, madia oil, candle nut oil. Lesser known oils are : Isano oil, Mohamba oil, garden rocket oil, henbane seed oil, celosia oil, Indian laurel oil, tobacco seed oil, weld seed oil. LINSEED OIL French —Huile de lin. German— Leinoel. For tables of constants see pp. 338-340. • Linseed oil is obtained from the seeds of the flax plant, Linum usitatissimum, L. The principal countries where it is grown and whence the seed is shipped to this country are Russia and India. Two qualities of Russian seed are recognised in the trade, and known, according to their source, as Baltic and Black Sea seed; hence Baltic linseed oil and Black Sea linseed oil. The oil expressed from Indian seed is known as East India oil. The Baltic linseed oil, yielding the best drying oil, is the first, the East Indian the lowest in quality ; this is explained by the fact that the Baltic seed is the purest, whereas in Black Sea seed 5 per cent of hemp seed or ravison seed is usually present, and that Indian seed is always mixed with mustard, rape, and cameline seed, owing to the plants yielding the latter being grown along with the flax plant. For it has been proved by experiments that if the linseed was carefully separated from the foreign seeds and then expressed, the oil was possessed of as good drying properties as best Russian oil. The addition of hemp seed or ravison seed to Black Sea oil has, however, been recently abandoned, and it is hoped that more attention will be paid in India to this growing industry. South American seed, yielding the River Plate oil, has recently been imported into this country, as also Canadian oil, in small quantities. Linseed oil expressed from the seed in the cold has a golden yellow colour; the oil obtained at a higher temperature is of a yellowish-brown hue. The taste and odour are peculiar, that of the oil obtained by hot pressure being more pronounced and more acrid than the cold drawn oil. XI LINSEED OIL 337 On exposure to the air linseed oil turns easily rancid with absorp¬ tion of oxygen; when spread in a thin film on a large surface it dries to a neutral substance insoluble in ether, termed linoxyn, the nature of which has not hitherto been ascertained. The linoxyn in its turn is further oxidised to a liquid substance (chap. xii. p. 738). Linseed oil contains about 10 to 15 per cent of glycerides of solid fatty acids—stearic, palmitic, and myristic—and 90 to 85 per cent of liquid glycerides. The liquid fatty acids consist, according to Hazura and Grilssner, 1 of about 5 per cent of oleic, 15 per cent of linolic, 15 per cent of linolenic, and 65 per cent of isolino- lenic acids. Pure linseed oil, prepared by Moerk 2 from pure seed, dissolved in 5 parts of absolute alcohol; by the purification of the oil with sulphuric acid the solubility is decreased. Girard’s figure has been stated above (p. 269), as also the solubility in acetic acid (p. 271). The amount of free acid in commercial linseed oil has been deter¬ mined by Nordlinger , 3 Thomson and Ballantyne , 4 and Beering. 5 The following table gives their results :— Free Fatty Acids in Linseed Oil Observer. No. of Samples. Free Acid as Oleic Acid. Nordlinger .... 10 Per cent. 0-41-4-19 Thomson and Ballantyne 4 0-76-374 Deering .... 5 0-75-1-60 The proportion of unsaponifiable matter in linseed oil has been found by Thomson and Ballantyne to vary between L09 and 1'28 per cent. For the purposes of ascertaining the purity of linseed oil and its drying power, and for the detection of adulterations, its specific gravity and iodine value are determined, and the thermal tests (p. 291) and Livache’s (p. 285) test applied. Linseed oil possesses a higher specific gravity than any fatty oil that would be used as an adulterant with the exception of Japanese wood oil. A lower gravity than CL930 would point to the presence of fish oils or mineral oils; a higher gravity would indicate probable adulteration with resin oils. According to Allen, linseed oil, intended for the manufacture of boiled oil, should possess a specific gravity of not less than 0'935. 1 Jour. Soc. Clievi. Ind. 1888, 506. 2 Ibid. 1888, 330. 3 Ibid. 1889, 806. 4 Ibid. 1891, 2(36. 5 Ibid. 1884, 541. Z These numbers must be accepted with reserve, as the iodine was allowed to act on the oil far too long a time. Physical and Chemical Constants of Linseed Oil—continued Physical and Chemical Constants of the Mixed Fatty Acids GLYCERIDES—DRYING OILS |1 ©"5 Q 3 £ 'g o B •< Q Q B 3 S B § § « II S-eo XI LINSEED OIL 341 Linseed oil, being the best drying oil, next to Japanese wood oil, possesses the highest iodine value of all known fatty oils. Un¬ fortunately the published values disagree to a considerable extent, the older numbers being much too low, owing to too small an excess of iodine solution having been used by the earlier experimenters (Benedikt 1 ). Thus Iliibl had found 156-160, Moore 155'2, Dieterich 16T9-180-9, and Wilson 148T-149T. Since then the more correct values, registered in the above given tables, have been obtained. Some chemists, however (Thomson and Ballantyne, Williams, Filsinger), go further, and allow the iodine to act 18 and more hours on the oil, and, consequently, obtain higher numbers. Such arbitrary alteration of a standard method is, however, not admissible. Fahrion' 2 has pointed out that the iodine value of linseed oil does not reach the figure calculated for its composition as given by Haznra and Griissner (see above), and he assumed, therefore, that raw linseed oil is partly polymerised during the process of manufacture. The fact, however, that, according to their own showing, Hazura and Grussner’s results represent but an approximation to the true values, should be sufficient to overthrow Fahrion’s hitherto unsub¬ stantiated assumption. The iodine value of fresh linseed oil should, therefore, as a rule, be above 170. A decrease of this value consequent upon exposure to the air has been shown to take place by Ballantyne , 3 This observer obtained for a sample of linseed oil, originally absorbing 173*46 per cent of iodine, after exposure to sunlight in an uncorked bottle and daily agitation, the following numbers :— After one month ,, two months „ five „ ,, six 171-8 171-78 169-07 166-17 Another sample of the same oil, but kept in a corked bottle, though exposed to sunlight, possessed after that time very nearly the original value, viz. 172 - 88. A sample of linseed oil, that had been kept by the writer for seven years in a stoppered bottle, absorbed 162*3 per cent of iodine. The following results given by Thomson and Ballantyne 4 for various brands of linseed oil are also instructive, being made under the same conditions :— Kind of Linseed Oil. Baltic . East India River Plate > > ? ) Iodine Value. 187-7 178-8 175-5 173-5 The temperature reaction of linseed oil with sulphuric acid— MaumenS test—is also very characteristic, linseed oil giving the 1 Zeit. f. angew. Cthemie, 1887, 213. 2 Ibid. 1892, 172. 3 Jour. Soc. Chem. Ind. 1891, 31. 4 Ibid. 1891, 236. 342 GLYCERIDES—DRYING OILS CHAP. highest rise of temperature with (cp. p. 293). The better a linseed pronounced is the thermal reaction, table due to Baynes 1 .•■— Kind of Linseed Oil. Baltic, two years old ,, similar sample English, old sample Russian . River Plate East Indian, fresh The bromine thermal value Maumene test and the iodine value, The values obtained are given i: the exception of some fish oils oil for varnish-making, the more as shown by the following short Rise of Temperature. ° C. 124 123 115 113 112 104 is, in correspondence with the also the highest on record, d the following table :— I. II. Kind of Linseed Oil. Bromine Thermal Value ”C. Hiibl Iodine Value. I x5"5. 1x5-7. 1x6-0. Observer. 30- 4 31- 3 160-7 154-9 167-2 172-0 Hehner & Mitchell 9 9 9 9 Raw linseed . Old sample . American (?) East Indian . 9 9 9 9 Baltic . 30-55 28- 5 28-8 29- 6 297 29- 8 30- 45 31- 35 31-4 31- 75 32- 5 174-3 167-1 177-0 177-0 177- 8 178- 7 183-3 188-5 188-8 188-8 192-5 173-9 171- 0 172- 8 177- 6 178- 2 178-8 182-7 188-1 188-4 190-5 195-0 Jenkins 2 Archbutt 3 9 9 9 9 9 9 Livaehe’s test yields the highest numbers for linseed oil (see p. 285), as also does, of course, the oxygen absorption test proposed by Fahrion (p. 288). Therefore the commercial value of a sample of linseed oil intended for the manufacture of varnish is best ascer¬ tained by determining its oxygen absorption power. Linseed oil is further characterised by not yielding a solid elaidin. The colour reactions, such as Brulld’s, Heydenreich’s, Hauchecorne’s, are not characteristic enough to be used as a means of distinguishing linseed oil from other oils, or to ascertain its presence in mixtures of oils, the concentrated sulphuric acid test (p. 315) excepted. On allow- 1 Allen, Com. Org. Analys. ii. 123. 2 Jour. Soc. Chem. Ind. 1897, 194. 3 Ibid. 1897, 311. XI LINSEED OIL 343 ing 2 drops of concentrated sulphuric acid to fall into 10 drops of linseed oil, a reddish-brown clot is produced ; if other oils are present the linseed oil (and other drying oils) only is resinified, and the brown clots are readily observed as they float in the unresinified oil. Adulteration of Linseed Oil. — Linseed oil being one of the cheapest fatty oils—sometimes even cheaper than cotton seed oil— a fraudulent admixture of a vegetable oil will seldom occur. However, presence of vegetable oils, of the rape oil and cotton seed oil group, would be revealed at once by the considerably lower iodine value of the sample. Piape oil would be indicated by a lower saponification value than the normal one (p. 305) [in the absence of unsaponifiable matter], and cotton seed oil, perhaps, by the colour test with nitric acid, etc. (see “Cotton Seed Oil,” p. 381). The presence of vegetable oils belonging to the drying oils, such as hemp seed oil or Japanese wood oil, would not be pointed out unmis¬ takably by the iodine value, their iodine absorptions being too close to those of pure linseed oil. Admixture of Japanese wood oil, if such should occur, would most likely be ascertained by the deter¬ mination of the viscosity of the sample. As some fish oils assimilate fully as much iodine as linseed oil, the iodine test would be of no practical use for the detection of such oils. The presence of fish oils would, however, be recognised by the charac¬ teristic smell of the oil, especially on warming, and perhaps also by the intensity of the phospho-molybdic acid colour reaction (see p. 475). According to Livaclie 1 linseed oil fatty acids are frequently used as an adulterant. Their presence in linseed oil would be detected by a considerable acid value of the sample; the acids could be separated from the oil by agitating the sample with alcohol, in which linseed oil is but sparingly soluble. Adulteration with mineral oils and resin oils is frequently practised. If only one of these two oils be the adulterant used, the specific gravity of the sample would indicate the line of examination. A judiciously prepared mixture of both oils, however, might possess the specific gravity of linseed oil. The presence of either adulterant, however, is recognised by the estimation of the unsaponifiable matter (p. 218). This determination yielding unmistakable results, the tests proposed by Coreil 2 —viz. action of gaseous chlorine and determination of the saponification value, and subsequent calculation on the basis of assumed average values—are altogether superfluous. If the further examina¬ tion of the unsaponifiable matter be desired, especially with a view to ascertaining the presence of either mineral oil or resin oil, the methods pointed out above must be resorted to (p. 225). Aignan 3 states that the French linseed oils are, as a rule, adulter¬ ated with resin oil, and recommends the polarimetric method for its detection. Linseed oil being optically inactive (or at all events almost so for all practical purposes) he employs a saccharimeter (or 1 Vernis et Huiles Siccatives, Paris, 1896, p. 158. 2 Jour. Soc. Ohcm. Ind. 1892, 550. 3 Ibid. 1890, 903. 344 GLYCERIDES—DRYING OILS CHAP. any other polarimetric apparatus), a deviation to the right indicating resin oil. Resin itself is best detected in linseed oil by applying the Lieber- mann-Storch reaction (p. 226). If the oil be very dark in colour, extraction of resin with alcohol may be resorted to. The amount of resin can be determined quantitatively by titration of the sample of oil with aqueous normal alkali, using phenolphthalein as an indicator, subtracting, however, from the amount of alkali used the small quantity of alkali required for free acid in the linseed oil (from 0‘4 to 4 per cent). Test experiments instituted in the writer’s laboratory proved the correctness of this method (cp. p. 239). Linseed oil is used as stock material for soft soaps ; its principal application, however, is found in the manufacture of boiled oil foi] paints and varnishes. On treatment with yellow sulphur chloride a rubber-like mass is obtained, used as a rubber substitute; on heating with sulphur the official oleum lini sulf. is obtained. Boiled oil and the rubber substitute obtained from linseed oil will be described in the following chapter (pp. 736, 742). [Table Physical and Chemical Constants of Japanese Wood Oil XI JAPANESE WOOD OIL 345 JAPANESE WOOD OIL 1 French —Haile de hois. German— Oelfirnissbaumoel, Tangoed. Japanese wood oil must not be confounded with the ethereal wood oil or Gurjun balsam. 346 GLYCERIDES—DRYING OILS CHAP. Physical ancl Chemical Constants of the Mixed Fatty Acids Solidifying Point. Melting Point. Saponification Value. Iodine Value. Thermal Test. Heat of Bromination. °C. Observer. °C. Observer. Mgrms. KOH. Observer. Per Cent. Observer. °C. Observer. 34 31-2 Jenkins D. N. & S.l 37 43’SI Jenkins D. N. & S. 188-8 D. N. & S. 150-1 159-4 Jenkins D. N. & S.l 26 Jenkins Japanese wood oil is obtained from the seeds of Aleurites cordata —(its Japanese names are Aiwa giri, and Jani, Kiri)—(.Elseococca vernicia), a tree indigenous to China 2 and Japan. The cold-drawn oil is pale yellow, whereas the oil obtained by hot pressure is dark brown, and has an unpleasant taste and odour. It thickens at — 18 C. without, however, solidifying. A specimen examined by Jenkins, 3 contained 3'84 per cent of free acid calculated as oleic acid, and another specimen, examined by Peering, 5‘9 per cent. The former specimen contained 0'44 per cent of unsaponifi- able matter. The oil does not give the elaidin reaction; by this test an oily layer was obtained resting on a lower, nearly solid product; when stirred up, the whole mass would flow. Tested in Redwoods viscosimeter, 50 c.c. took 1433 seconds to run through (water, 28 seconds). In Vilenta’s test the temperature of turbidity was 47° C. In the sulphur chloride test 5 grms. of the oil treated in the cold with 2 c.c. of S 2 C1 2 and 2 c.c. of CS 2 gave in 1J minutes a thick and stiff jelly. The refractive index is very high, approaching that of resin oil. Japanese wood oil consists, according to Cloezf of the glycerides of oleic and elaeomargaric acids (p. 60). The existence of the latter acid has been confirmed by De Negri and Sburlati. Japanese wood oil possesses even more strongly pronounced dry¬ ing powers than candle nut oil, and is consequently the best drying oil known. In thin layers the oil dries completely within 20 hours (linseed oil 20 hours). In an experiment made by Jenkins, 4 grms. of oil exposed in the boiling-water oven in a shallow porcelain dish, 7 cm. diameter, showed after ^ hour evidence of a skin commencing to form round the edges. In two hours the oil would not flow, and was entirely covered by a crinkled skin. The average gain of weight during four hours’ exposure was CP36 per cent per hour. (Raw linseed oil treated similarly showed after four hours no evidence to skin.) Heated with lead oxide and red lead, the oil gelatinises within fifteen minutes to a light brown mass. 1 Prepared by these observers from seeds. 2 Cp. Jour. Soc. Chem. Ind. 1897, 684. 3 Ibid. 1897, 194. 4 Bulletin Soci&te Cliimique, 26. 286 ; 28. 23. XI JAPANESE WOOD OIL 347 According to these experiments, one would expect Japanese wood oil to absorb more iodine than linseed oil. It appears likely that if the freshly expressed oil were examined, wood oil may be found to have so high an iodine value as to take its place before linseed oil. But it should be pointed out that the heat of bromination test leads to a calculated iodine value of 133-4 only, whereas the Hiibl test indicates 165‘7. This difference, however, disappears when the fatty acids are examined, the bromo-thermal test giving by calculation 148 - 3 instead of the observed iodine number 150T. Concentrated sulphuric acid gives a black clot with the oil. When 1 grm. of the oil is dissolved in 5 c.c. of chloroform, and 5 c.c. of a saturated solution of iodine in chloroform are added and the mixture stirred, the whole is converted into a stiff jelly after about 2 minutes. If 2 grms. of the oil be employed under the same conditions, the jelly is so stiff that it can be granulated. On heat¬ ing the oil to 250° C., contact with air being carefully excluded, it is converted into a clear, solid, elastic substance; this body is insoluble in the ordinary solvents of oils, and shows no tendency to melt, on being again heated to 250° C. Wood oil has not yet been imported to Europe as a commercial article, but is at present attracting some attention. In China and in Japan it is produced in enormous quantities, and is used there chiefly as a natural varnish for wood, and also for lighting. LALLEMANTIA OIL 1 French— Huile tie Lallemantia. German— Lallemantia Oel. Physical and Chemical Constants of Lallemantia Oil Specific Gravity at 20° 0. Solidifying Point. Helmer Value. Reichert Value. Saponifica¬ tion Value. Iodine Value. 0-9336 - 35° C. 93-3 1-55 185 162-1 Physical and Chemical Constants of the Mixed Fatty Acids Solidifying Point. Melting Point. Iodine Value. 11° C. 22-2° C. 166 Lallemantia oil is obtained from the seeds of Lallemantia iberica, a plant belonging to the Labiatx, growing wild in the Caucasus, and cultivated in Russia (near Kieff). 1 Richter, Jour. Soc. Chem. Ind. 1887, 825 ; Zeitscli.f. Chem. Ind. 1887, 230. 348 GLYCERIDES—DRYING OILS CHAP. As will be seen from the iodine value, the oil belongs to the best drying oils, and surpasses in this respect, according to Richter , even linseed oil. A sample of the oil spread on a watch-glass dried after 9 days to a thick resin-like skin. If the oil was heated to 150° C. for 3 hours, complete drying took place after 24 hours. The absorption of oxygen, determined according to Livache, using copper powder, was for the oil 15'8 per cent after 24 hours, and for the mixed fatty acids 14 per cent after 8 days. 10 grms. of the oil at 18° C. mixed with 2 grms. of concentrated sulphuric acid rose to a temperature of 120° C. In the elaidin test 10 grms. of the oil, 5 grms. of nitric acid, specific grav. T4, and 1 grm. of mercury, gave after shaking for 3 minutes a dark red dough-like mass. Lallemantia oil is used for illuminating purposes. It should prove an excellent material for varnishes. HEMP SEED OIL French— Huile de chhievis, Unite de chanvre. German— Hanfoel. For tables of constants see p. 349. Hemp seed oil is obtained from the seeds of the hemp plant, Cannabis sativa. The colour of the freshly expressed oil is light green to greenish-yellow, becoming brownish-yellow on keeping. It pos¬ sesses a characteristic smell, has a mild taste, and dries easily. Hemp seed oil is soluble in 30 volumes of cold alcohol; from a solution of the oil in 12 volumes of boiling alcohol “stearine” is deposited on cooling. The fatty acids of the liquid glycerides of hemp seed oil consist, according to the researches of Bauer , Hazura, and Griissner, principally of linolic acid and of smaller quantities of oleic, linolenic, and iso- linolenic acids. The solid glycerides in hemp seed oil are : stearin and palmitin. Pure hemp seed oil may be easily identified by its high iodine absorption. Mixtures of the same iodine value can only be prepared with the help of linseed (or Lallemantia) oil. The price of the latter, however, being against it, linseed oil is rather adulterated with hemp seed oil (and Lallemantia oil). This used to happen regularly until recently in the case of Black Sea linseed oil, as the growers had been in the habit of mixing hemp seed with the linseed. Hemp seed oil is used as a paint oil, though less frequently in this country than on the Continent, where considerable quantities are also employed for making soft soaps, characterised by a dark green colour. Although not drying so quickly as linseed oil (cp. chap. ix. p. 287), it is used in the manufacture of varnishes. Physical and Chemical Constants of Hemp Seed Oil HEMP SEED OIL 349 . 4 B-S ■§§ hH O P o Observer. Jean Pearmain £ C2 ■s g «o “Degrees.” ^ *P CO N- 4- CO q „ +r ^ ^ -M 00 co ce + + n “ c« • rt’ cS os vo ca os Refractive Index. Observer. Blasdale Oleo-refractometer. Observer. Jean Tfl o OO “Degrees.” co CO + o 4-> VO CO + Maumene Test. _ Observer. Maumene De Negri and Fabris Blasdale d 101 96 110 Value. Observer. Hiibl Dieterich Hazura Peters De Negri and Fabris Blasdale Iodine Value. Observer. De Negri and Fabris Per cent. 150-05 Melting Point. Observer. Hiibl De Negri and Fabris Blasdale d 20 16-18 15 -g > 3 o £ hp o '3 d 16 Blasdale {.lour. Soc. Chen. Ind. 1896, 206). Oil from Juglans regia grown in California. 352 GLYCERIDES—DRYING OILS CHAP. POPPY SEED OIL French— Huile d’ceillette, Huile blanche, Huile de pavot de pays. German— Mohnoel For tables of constants see p. 353. Poppy seed oil is obtained from the seeds of the poppy, Papaver somnifervm, by pressing. The cold-drawn oil, the oil of the first pressing, is almost colourless or very pale golden yellow; this is the “white poppy seed oil” of commerce. The second quality, expressed at a higher temperature, is much inferior, and constitutes the “ red poppy seed oil ” of commerce. Poppy seed oil has little or no odour and a pleasant taste, so that it is largely used as salad oil, especially as it does not easily turn rancid. The oil of unsound quality, however, possesses an acrid taste. Poppy seed oil dissolves in 25 volumes of cold, or in 6 volumes of boiling alcohol. The glycerides of myristic and lauric acids are absent; the fatty acids of the solid glycerides are : stearic and palmitic acids. The liquid fatty acids of poppy seed oil consist chiefly of linolic acid (65 per cent) and smaller quantities of oleic acid (30 per cent); the less satu¬ rated linolenic acids are present only in small quantities (5 per cent). Poppy seed oil contains varying quantities of free fatty acids, as shown in the following table :— Kind of Oil. Free Fatty Acids calculated to Oleic Acid. Observer. Salad oil, 26 samples Commercial oil, expressed, 5 samples Commercial oil, extracted, 5 samples Per cent. 2-09 2'29 0-70-2-86 12*87-17-73 215-9-43 ' Reclienberg Salkowski Nordlinger > > Poppy seed oil is but rarely adulterated with other oils; the adulterant chiefly used is sesame oil. The latter can he detected by the lower iodine absorption of the sample, and by the characteristic Baudouin colour reaction (cp. “ Sesame Oil,” p. 390). Poppy seed oil is in its turn fraudulently added to olive oil (cp. p. 460); the high iodine value in conjunction with the comparatively high specific gravity chiefly indicate the adulteration. The finer qualities of oil are used for culinary purposes, and also for the best quality of paints for artists, because of its excellent drying properties (see chap. ix. p. 290). A mixture of equal volumes of “ sun-bleached ” poppy seed oil and bleached poppy seed oil var¬ nish is extensively used for white pigments (Loiter 1 ). A solution of fused gum mastic and Japan wax in poppy seed oil is obtainable in commerce as “ wax oil.” On account of its high price but the lowest qualities can be employed for making soft soaps. 1 Jour. Soc. Chem. Ind. 1895, 168. Physical and Chemical Constants of Poppy Seed Oil POPPY SEED OIL Observer. Jean Pearmain “Degrees.” +23-5- 29 +351 +30 to +35 at 22° C. 2 ££>■£ rQ 05 0 -afc =s o cL L D h <(o W Sflfe m P^OP h gha cd h. Jfe'G o .2 c s 5 gqQ^O Os OS OS CM Os ce 2D 2D O 1 Very old sample. 354 GLYCERIDES—DRYING OILS CHAP. NIGER SEED OIL French —Huile de Niger. German— Nigeroel. For tables of constants see p. 355. Niger seed oil is expressed from the seeds of Guizotia oleifera, a plant cultivated in the East and West Indies, and also in Germany. The oil is yellow, has a nutty taste, and has poorer drying powers than the preceding oils. According to Allen it dries rapidly at 100° C. Niger seed is crushed in this country (Hull), and the oil ob¬ tained is used as a substitute for linseed oil, and for adulterating rape oil. [Table Physical and Chemical Constants of Niger Seed Oil 356 GLYCERIDES—DRYING OILS CHAP. SUNFLOWER OIL French —Huile de soleil, Huile de tournesol. German— S'onnenblumenoel. For tables of constants see p. 357. This oil, obtained from the seeds of Helianthus annuus, is a limpid, pale yellow oil of mild taste and pleasant smell. A sample of sunflower oil was found to contain 0 - 31 per cent of unsaponifiable matter ; free fatty acids and volatile acids were absent; another sample prepared by Holde 1 from sunflower seed by extraction with petroleum ether contained 5'6 per cent of free fatty acids calcu¬ lated to oleic acid. The liquid fatty acids consist chiefly of linolic acid, oleic acid being present in small quantities only. This oil dries more slowly than those already described. The absorption of oxygen, according to Hull’s method, using copper powder as an oxygen carrier, took place at the following rate :— Absorption of Oxygen. After 2 days. After 7 days. After 30 days. Per cent. Per cent. Per cent. Sunflower oil. 1-97 5-02 Sunflower oil fatty acids . 0-85 3-56 6-3 Sunflower oil is chiefly cultivated in Russia,“ where the cold- drawn oil serves for culinary purposes ; the oil expressed at a higher temperature is employed in soap-making and for the manufacture of varnishes. It is added fraudulently to olive oil {Allen), and recently also, in place of cotton seed oil, to margarine ( Jolles 3 ). The nitric acid test has been found reliable for distinguishing sunflower oil from cotton seed oil in mixtures with other oils ; whereas the latter becomes brown on treatment with this reagent (see “ Cotton Seed Oil,” p. 381), sunflower oil does not change its colour. 1 Jour. Soc. Chem. Ind. 1894, 892. 2 Ibid. 1892, 4 1 0. 3 Ibid. 1893, 935. [Table Physical and Chemical Constants of Sunflower Oil. 358 GLYCERIDES—DRYING OILS CHAP. FIR SEED OIL French— Huile de Pignon. German— Fichtensamenoel. For tables of constants see p. 359. Fir seed oil is obtained from the seeds of several kinds of pine-trees —Pirns sylvestris (Scotch fir seed), Pinus Picea, and Pinus Abies. 1 This oil is limpid and of pale yellow colour (Scotch fir seed oil brownish-yellow— Allen), and has a sweet taste. Fir seed oil dries easily, and is therefore used in the preparation of varnishes. The following are the constants of the oils obtained from the different seeds:— 1 The fatty oil from Pinus monojohylla (?) is described as Pine nut oil by Blasdale (Jour. Soc. Chevi. Ind. 1896, 205). It is a brown, drying oil with an unpleasant odour and taste. The following constants are given :— Physical and Chemical Constants of Pine Nut Oil. Spec. Grav. at 15° C. Saponification Value. Iodine Value. Maumene Test. Refractive Index. 0-933 192-8 101-3 71° 1-4769 Physical and Chemical Constants of the Mixed Fatty Acids. Melting point . . . . . 19° C. [Table Physical and Chemical Constants of Fir Seed Oil 360 GLYCERIDES—DRYING OILS CHAP. MADIA OIL French —Iluile de Madia. German— Madiaoel. For tables of constants see p. 361. Madia oil is obtained from the seeds of the Chilian plant Madia sativa. It has been also cultivated successfully in South Germany. This oil is dark yellow, and possesses a characteristic, not un¬ pleasant odour. It dissolves in 30 volumes of cold or 6 volumes of hot alcohol ( Schaedler ). Madia oil occupies an intermediate place between drying and semi¬ drying oils. Treated with nitrous acid (elaidin test) it remains liquid ; for this reason, and on account of its high iodine value, it is placed amongst the drying oils. It absorbs, indeed, considerable quantities of oxygen, becoming thereby viscid. The oil is chiefly used for burning and also for soap-making. [Table Physical and Chemical Constants of Madia Oil 362 GLYCERIDES—DRYING OILS CHAP. CANDLE NUT OIL French— Huile de noix de chandelle. German— Candlenussoel, Bankulnussoel. Candle nut oil is obtained from the seeds of the tropical plant Aleurites moluccana. The constants recorded for this oil are of a somewhat conflicting nature, owing, no doubt, to different observers having had under examination oils from different sources. A sample of oil examined by Clo'ez had a specific gravity of 0 - 9232 at 15° C. The cold-drawn oil is limped, colourless or yellowish, and has a pleasant odour and taste ( Bornemann ); on account of its purging properties, however, it cannot be used for edible purposes. A sample of candle nut oil, three years old, contained 56’5 per cent of free fatty acids ( Nordlinger 1 ). Candle nut oil possesses powerful drying properties; on boiling, a good varnish is obtained, drying far better than the oil itself. Candle nut oil varnish surpasses even boiled linseed oil as a rapidly drying oil. The oil is also used for soap-making, especially in France, and is said to be a good substitute for cocoa nut oil. Lacli 2 has examined a sample of candle nut oil (perhaps candle nut “ stearine ”)• The consistency was that of a salve, its colour light yellow, and its smell nauseous. On exposure to light and air it dried to a horny mass. It dissolved sparingly in alcohol, easily in petroleum ether. The alcoholic solution had an acid reaction, owing, no doubt, to the large percentage of free fatty acids (see above). The following constants were determined by Lack for this sample:— Hehner value . . . . . . 94’56 Solidifying point of the mixed fatty acids . . 56° C. Melting ,, ,, ,, . 65'5° C. Iodine value . . . . . .118 The fatty acids were amorphous, consequently the fat was unsuit¬ able for candle-making. Lesser Known Drying Oils ISANO (UNGUEKO) OIL 3 Isano (I’Sano) oil is obtained from the seeds of the I’Sano 4 or Ungueko, 5 a large tree of the family Oleaceai, growing in the French Congo. The ground and dried seeds yield 60 per cent of oil. 1 Jour. Soc. Chem. Ind. 1889, 806. 2 Chem. Zeit. 1890, 871. 3 Hebert, Jour. Soc. Chem. Ind. 1896, 660. 4 Local name in Loango. 8 Local name. XI MOHAMBA OIL—GARDEN ROCKET OIL 363 The specific gravity of the oil is 0'973 at 23° C. It is liquid even at - 15° C., is reddish in colour, has an insipid flavour and fishy smell. The oil is viscous and possesses strong drying powers. Tested by Maumen^’s test it gives a thermal reaction of 115° C. The bromine value is stated to be double that of oleic acid. It is further stated that the oil contains 86 per cent of liquid fatty acids (the lead salts being entirely soluble in ether), consisting of 15 per cent oleic acid, 75 per cent linolic acid, and 10 per cent of isanic acid (chap. iii. p. 63). On saponification from 12 to 13 per cent of glycerol are said to be obtained. MOHAMBA OIL 1 The seeds yielding Mohamba oil are very similar to those of the Isano tree, but after drying they give only 12 per cent of oil. The oil has a specific gravity of 0‘915 at 23° C.; it remains liquid at - 15° C., is of yellow colour, fairly fluid, inodorous, and of insipid taste. The thermal reaction—Maumene’s test—gave a rise of 55° C. On saponification about 9 per cent of glycerol and 90 per cent of brown liquid unsaturatecl fatty acids are obtained from the oil. From the lead salts of the acids, which are entirely soluble in ether, there was obtained, on separating the free acids, a white fatty acid, soluble in alcohol and ether, and crystallising from the latter in laminae, melting at 34°-35° C. This acid absorbs about as much bromine as oleic acid, and would therefore belong to the oleic series, but does not seem to correspond with any known acid. The liquid acids appear to consist of oleic acid, as they absorb an amount of bromine corresponding to oleic acid and give the elaidin reaction. GARDEN ROCKET OIL 2 —DAME’S VIOLET OIL French —Huile de julienne. German— Eothrepsoel. For tables of constants see p. 364. This oil is expressed from the seeds of the garden rocket, Hesperis matronalis. When fresh it is of green colour, becoming brownish on keeping. It is an odourless oil possessing a somewhat bitter taste. Rocket garden oil is expressed in France and Switzerland, and used as a burning oil. 1 Hebert, Jour. Soc. Chem. Ind. 1896, 660. 2 De Negri and Fabris, Annali del Labored. Chim. delle Gabelle, 1891-92, 151. Per cent. XI HENBANE SEED—CELOSIA—INDIAN LAUREL 365 HENBANE SEED OIL 1 German— Bilsenkrautsamenoel. Henbane seed oil is obtained from the seeds of Hyoscyamus niger. This oil is yellow, somewhat viscous, slightly fluorescent, and readily drying. Physical and Chemical Constants of Henbane Seed Oil Spec. Gravity at 15° C. Saponific. Value. Reicliert Value. Hehner Value. Iodine Value. 0-939 170-8 0-99 94-7 138 CELOSIA OIL 2 This oil is obtained from the seeds of Celosia cristata; it is a greenish-brown, drying oil, sparingly soluble in alcohol. Physical and Chemical Constants of Celosia Oil Solidifying Point. Saponific. Value. Iodine Value. - 10° C. 190-5 126-3 Physical and Chemical Constants of the Mixed Fatty Acids Solidifying Point. Melting Point. 21°-19° C. 27°-29° C. INDIAN LAUREL OIL 3 The fruits from Laurus indica yield a brown, viscous oil, having the constants given in the following table. The specimen examined contained 33 per cent of free fatty acids. Physical and Chemical Constants of Indian Laurel Oil Spec. Grav. at 15° C. Solidifying Point. Saponific. Value. Iodine Value. 0-926 Thickens at - 15° C., but does not solidify. 170 118-6 1 Mjoen, Jour. Soc. Chem. Ind. 1897, 340. 2 De Negri and Fabris, Chem. Zeit. 1896, Rep. 161. 3 Ibid. 366 GLYCERIDES—SEMI-DRYING OILS CHAP. Physical and Chemical Constants of the Mixed Fatty Acids Solidifying Point. Melting Point. 19°-18° C. 24°-26° C. TOBACCO SEED OIL French —Huile de Tabac. German— Tabaksamenoel. Specific gravity 09232 at 15° C., solidifies at -25° C. Colour— pale greenish-yellow. The oil dries easily. WELD SEED OIL Ger nia i i— Besedasamenoel. This oil is obtained from the seeds of the dyer’s weld, Peseda luteola. Owing to the presence of chlorophyll the oil has a dark greenish tint. Specific gravity 0’9058. Solidifying point -20° C. It has a bitter taste and nauseous odour. The oil dries easily on exposure to air, and is used for burning and making varnishes. (2) Semi-drying Oils The oils comprised in this class form an intermediate link between the drying and the non-drying oils (cp. also chap. ix. p. 279). This finds its readiest expression in the iodine values. For this reason these oils are described in the order of their iodine values. The members of this class appear to range themselves naturally into three groups— a. The cotton seed oil group. f3. The rape oil group, y. The castor oil group. a. The Cotton Seed Oil Group The members of the group possess distinct drying properties, although less pronounced than in the case of the true drying oils. The group takes its name from its most prominent member, which may be considered as the type of a semi-drying oil. We shall describe the following oils : Cameline oil, soja bean oil, pumpkin seed oil, maize oil, kapok oil, cotton seed oil, sesame oil, basswood oil, beechnut oil, Brazil nut oil. XI CAMELINE OIL 367 CAMELINE OIL (GERMAN SESAME OIL) French— Haile cle Camelina. German— Deutsches Sesamoel, Leindotteroel. For tables of constants see p. 368. Cameline oil is obtained from the seeds of Myagrum sativum (or Camelina sativa), belonging to the Crucifer se. The oil has a golden-yellow colour and a pungent taste and smell. On exposure to air it dries slowly. Boiled with litharge or man¬ ganese borate it yields a slowly drying varnish. The low saponification value of the oil points to the presence of glycerides of erucic acid. The oil prepared by expression is free from sulphur, like all the oils drawn in the cold from seeds of the Cruciferse (cp. “ Rape Oil,” p. 406). On account of its low price the oil is not likely to be adulterated. It is used, however, for the adulteration of rape oil, in which it may be detected by the high iodine value. Cameline oil is naturally present in linseed oil expressed from East Indian seed (cp. 336). The cold-drawn oil is sometimes employed for culinary purposes. Its chief use, however, is for soap-making, yielding as it does a very soft soap, which suitably replaces linseed oil in winter. In summer, however, cameline oil cannot be used alone, the soap being liquid at a temperature below 20° C. [Table XI SOJA BEAN OIL 369 SOJA BEAN OIL French —Huile de Soya. German— Sojabohnenoel. For tables of constants see p. 370. This oil is obtained from the seeds of Soja hispida, a plant in¬ digenous in China and Japan, where the oil is used for culinary purposes. A sample of the oil extracted with ether by Morawski and Stingl gave 0 - 22 per cent of unsaponifiable matter, and 2’28 per cent of free acid calculated to oleic acid. On exposure to air it dries slowly with formation of a thin skin. 2 B [Table Physical and Chemical Constants of Pumpkin Seed Oil XI PUMPKIN SEED OIL 371 PUMPKIN SEED OIL French —Huile cle pepins de citronelle. German— KurUssamenoel. -rtt H H CO (N (N h no ^ t-H 'O 4-3 zo t-H t-H I I CO CO CM Ci Oi 372 GLYCERIDES—SEMI-DRYING OILS CHAP. Pumpkin seed oil is expressed from the seeds of Cucurbita pepo. The cold-drawn oil is used for culinary purposes ; it is stated that the oil from the large cucumber grown on the Slave Coast far exceeds in flavour the finest olive oil. The lower qualities serve for burning. This oil dries very slowly. MAIZE OIL—CORN OIL 1 French —Huile de mats. German— Maisoel. For tables of constants see p. 374. This oil is obtained from the seeds of the maize plant, Zea Mays, either by expressing the seed before it is employed for the manu¬ facture of starch, or, where they have been used for production of alcohol, by recovering it from the residue of the fermentation vats. Maize oil prepared by the former process is of a pale yellow or golden-yellow colour, whereas the oil furnished by the second process is reddish-brown. The latter oil will most likely be characterised by a large proportion of free fatty acids. Thus the sample of oil ex¬ amined by Hart, 2 being reddish-brown, contained 0'75 per cent of free fatty acids, whereas the sample analysed by Spuller, z was absolutely neutral. The oil dissolves readily in acetone and more sparingly in alcohol and glacial acetic acid. The following table, due to Smith,^ gives the volumes of oil dissolved by 100 volumes of these three solvents :— Solubility of Maize Oil in 100 volumes of Absolute Alcohol. Acetone, commercial. Glacial Acetic Acid. At 16° C. At 63° C. At 16° C. At 16° C. At 63° C. 2 13 24 3 9 Maize oil is, notwithstanding its high iodine value, 5 almost devoid of drying powers. No decided drying properties are imparted to it by subjecting it to the process of “boiling,” or by addition of lead oxide. If, however, a current of air is passed through it at 150° C., it will, on addition of manganese borate, acquire to a small extent 1 So termed in the United States. 2 Jour. Soc. Chem. Ind. 1894, 257. 3 Dingl. Polyt. Jour. 264. 626. 4 Jour. Soc. Chem. Ind. 1892, 505. 5 Rokitansky {Jour. Chem. Soc. 1895, Abstr. i. 509) describes a maize oil obtained from the yellow Italian maize plant, grown in Southern Russia as a yellow, neutral oil of 0'836 specific gravity, and the (Htibl) iodine number 75 - 8. These numbers differ so much from those given in the table, that they have not been embodied therein. XI MAIZE OIL—CORN OIL 373 drying properties, and a thin film on lead dries in ten to twenty hours, but not completely. Maize oil appears to contain no stearin, since no stearic acid crystals could be obtained from a specimen of maize oil by Hehner and Mitchell’s method (chap. viii. p. 198). Like cotton seed oil, maize oil yields in the elaidin test a mass having a pasty or buttery consistency. The unsaponifiable matter in maize oil consists mostly of phyto¬ sterol. Spilller found 1*35 and Hart 1’55 per cent of unsaponifiable matter. The colour reactions ( Wellmann’s , Becchi’s) are not sufficiently characteristic to identify the oil, or to detect it in admixtures with other oils. Adulteration of maize oil with mineral oil or resin can be easily recognised by the quantitative determination of the Unsaponifiable matter and by the Liebermann-Storch reaction (p. 226). Maize oil is used as a burning and lubricating oil, and also for soap-making. Latterly it is being used extensively in place of cotton seed oil for the adulteration of lard. [Table Physical and Chemical Constants of Maize Oil 374 GLYCERIDES—SEMI-DRYING OILS CHAP. Iodine Value. Observer. Spiiller Smetham Smith Do Negri and Fabris Hart Wallenstein Per cent. 119-4- 119-9 116-3 122-9 111-2- 112-6 117 122 Reichert Value. Fh £ o Spiiller Smith De Negri and Fabris Mgrms. KOH. 188-189 193-4 190-4 Hehner Value. Observer. Lloyd Spiiller Hart Per cent. 96-67 94- 7 95- 7 Solidifying Point. Observer. Schaedler Smith De Negri and Fabris d -10 -10 to -20 -10 to -15 Specific Gravity. Fd 0) t ® rO o Bornemann Smith Lloyd De Negri and Fabris Hart At 15° C. 0-9215 0-9244 0-9160 0-9215- 0-9220 0-9239 •J! e § ^3 Si *3 Rh Saponification 1 Value. Ob¬ server. Spiiller Mgrms. KOH. oo Oi Iodine Value. Observer. Spiiller De Negri and Fabris Value of the Fatty Acids. Wallenstein and Finck Per cent. 125 113-115 Iodine Liquid 1407 Melting Point. Observer. De Negri and Fabris Jean d 18-20 20 Solidifying Point. Ob¬ server. De Negri and Fabris 1 ^ p S o 6 § m Q ^ U-t -d -d g w E a § * KH , ffl , T3 1 ,0 o 5>)'© g g«2 3 03 S GO . CO 05 CO CO Q CO “go >> ■—I > Thomson and Ballantyne Commercial oil . 5 2*43-6*24 | Commercial oil . 50 1*7-5 *5 Archbutt Commercial oil . 5 1*05-3*9 Deering If the oil is to be used for burning, the proportion of free fatty acids should be as small as possible. The oils obtained by extraction are, as a rule, purer than those prepared by expression, a large amount of albuminoid and mucilaginous substances passing into the oil in the latter process. Tested according to Livache, rape oil absorbs 2’9 per cent of oxygen after seven days, whereas the fatty acids absorb only 0*9 cent after eight days. (Cp. also p. 287.) The oil thickens and becomes rancid, without, however, drying. Rape oil may, therefore, be considered as representing a class of oils occupying an inter¬ mediate position between the semi-drying and the non-drying oils. The elaidin test does not yield characteristic indications. Rape oil is largely adulterated with the following fatty oils : Linseed, hemp seed, poppy seed, cameline, cotton seed, fish oils, and hedge mustard oil; paraffin and resin oils are also fraudulently added. The unsaponifiable oils are easily detected by the estimation of the unsaponifiable matter. Addition of large quantities of linseed, hemp seed , poppy seed, cameline, and fish oils, would be indicated by the iodine value and by the determination of one of the follow¬ ing constants: specific gravity, melting point of the fatty acids, thermal tests, saponification value, and especially the viscosity of the oil. The specific gravity of rape oil rarely exceeds 0*916, and this may be considered for practical purposes as the limit, although, as will be seen from the table given above, higher values have been recorded. Of the fifty-two samples examined by Archbutt — 7 samples had a specific gravity below 0*9140 27 ,, ,, ,, above 0*9139, but below 0*9150 18 0*9149, ,, 0*916Q XI RAPE OIL 405 The specific gravities of the other fatty oils that may be used as adulterants are higher than 0'9160, so that a sample of oil the specific gravity of which exceeds that figure must be looked upon with suspicion. Of course, presence of an unsaponifiable oil cannot be detected by determination of the specific gravity. The melting point of the fatty aeids, or, better still, the solidifying point (titer test), will be higher than the normal one if cotton seed oil has been added; on the other hand, it will be lowered by the presence of linseed oil or of any of the other oils mentioned above. The temperature test with sulphuric acid or bromine 1 will indi¬ cate admixture of linseed or other drying oils, or semi-drying oils, such as cotton seed oil. The saponification value of the sample under examination will easily lead to a decision whether any other fatty oil, with the excep¬ tion of the oils belonging to the rape oil group , such as hedge mustard oil, is present. In consequence of the large proportion of erucin in rape oil its saponification value is very low, lower than that of any of the fatty oils mentioned above. [Castor oil and grape seed oil, which are also characterised by low saponification values, need not be con¬ sidered here, as their employment as an adulterant for rape oil is out of the question.] It should not be forgotten, however, that a low saponification value may also be found if unsaponifiable oils are present. If so, they must be first separated, and the saponi¬ fication value of the fatty acids determined subsequently. The following are the saponification values of the fifty-two samples examined by Archbutt :— For 4 samples 170 to 171 12 ,, 171 „ 172 9 ,, 172 ,, 173 14 ,, 173 „ 174 11 ,, 174 „ 175 1 „ 175 ,, 176 1 ,, 176 ,, 177 It may be repeated that the other members of the rape oil class have also low saponification values. The determination of the viscosity of rape oil is a very valuable means of ascertaining its purity. It will be found best to compare the sample with a standard rape oil of known purity, as the viscosity of rape oil is fairly constant. Since no other oil likely to be used as an adulterant possesses so high a viscosity as rape oil, the genuine¬ ness of the sample can be easily and quickly ascertained. The Valenta test (p. 270) is very characteristic of rape oil, and will prove useful as an additional means of deciding whether a sample of rape oil is genuine or not. Fish oils in rape oil may be recognised by their peculiar smell 1 Cp. Archbutt, Jour. Soc. Chem. Incl. 1897, 311. 406 GLYCERIDES—SEMI-DRYING OILS CHAP. and taste, especially on warming, and perhaps also by the intensity of the phospho-molybdic acid reaction (p. 316). There is, according to Schweissinger, 1 in commerce a specially pre¬ pared “ refined fish oil ” recommended as an adulterant for rape oil, which could not be detected in rape oil by the chlorine, and other anti¬ quated colouring reactions for fish oils (p. 278). The determination of the iodine value, of the saponification value, and the detection of cholesterol, however, were quite sufficient to prove the addition of this adulterant. The figures collated in the following table for pure rape oil, this “ refined fish oil,” and a mixture of the two oils, demonstrate this clearly :— Rape oil. “ Refined Fish Oil.” Rape oil, containing 20 per cent of “ Refined Fish Oil.” Specific gravity at 15° C. . 0-915 0-931 0-919 Saponification value.... 181 218 191 Iodine value. 98 142 107 Melting point of the mixed fatty acids 21 26 23 Solidifying!,, ,, ,, 16 19 17 Besides these constants, the examination of the unsaponifiable matter furnishes a very valuable clue as to the nature of the adulterant. The unsaponifiable matter of rape oil consists of phytosterol, whereas the fish oils are characterised by cholesterol, which can be detected by the colour reactions given for the latter (p. 84). As rape oil is refined with concentrated sulphuric acid, commercial oils should be tested for the presence of sulphuric acid by shaking the oil with warm water and examining the latter. The detection of rape oil in other oils by means of Mailho’s or Schneider's 2 reagents, purporting to show presence of sulphur, can no longer be considered as useful, since it has been proved that sulphur is not a constitutive element of the oils obtained from the seeds of Cruciferee. The “ cold-drawn ” oils of commerce are completely devoid of sulphur, but oils extracted by means of carbon disulphide (as olive kernel oil, etc.) may retain some sulphur, the last traces of the solvent being extremely difficult to remove. Rape oil would be detected by its characteristic smell, or by the influence its presence exercises on the constants of the oil under examination, especially on the saponification value (cp. “ Olive Oil,” p. 461). The colour reaction proposed recently by Palas 3 for the detection of rape oil in olive oil (viz. agitation with rosaniline sulphite) is not characteristic of rape oil only, as any other oil containing silver-reducing substances, such as, e.g., cotton seed oil, gives the same reaction. Experiments instituted by the writer proved that Palas’ statement to the contrary is erroneous. 1 Pharm. Central-Halle, 1890, 713. 2 Cp. page 463. 3 Jour. Soc. Chem. Ind. 1897. 361. XI BLACK MUSTARD OIL 407 BLACK MUSTARD OIL French —Huile de moutarde noire. German— Schwarzsenfoel. For table of constants see p. 408. Black mustard oil is obtained from the seeds of Sinapis nigra. The oil has a brownish-yellow colour, and possesses a mild taste; it smells of the ethereal mustard seed oil. In its chemical composition it closely resembles rape oil; like the latter, it contains the glycerides of erucic and behenic (or arachidic 1), and also of a liquid fatty acid 1 (rapic acid 1). Ndrdlinger has found in two samples of the oil free fatty acids to the extent of 068 and 1‘02 per cent, calculated to oleic acid. The oil is a by-product; it is not so suitable for burning as the white mustard oil, and is therefore used for soap-making. 1 Goldschmiedt, Wiener Berichte, 70. [[2], 451. [Table Physical and Chemical Constants of Black Mustard Oil 408 GLYCERIDES—SEMI-DRYING OILS CHAP. Jour. Soc. Cliem. Ind. 1896, 206. XI WHITE MUSTARD OIL 409 WHITE MUSTARD OIL French —Huile cle moutarde blanche. German —JVeisssenfoel. For tables of constants see p. 410. White mustard oil is obtained from the seeds of Sinapis alba The oil is of a golden-yellow colour, and has a burning taste. Most of its physical and chemical constants are almost identical with those of black mustard oil. The iodine values, however, appear to differ considerably. The oil is used as a burning and lubricating oil. [Table Blasdale XI RADISH SEED OIL 411 RADISH SEED OIL French —Huile de raifort. German— Iiettigoel. For tables of constants see p. 412. Radish seed oil, like the oils described last, closely resembles rape oil. The green colour, which is said to be characteristic of the soap solution of hedge mustard oil, is not obtained with this oil (De Negri and Fabris). [Table Physical and Chemical Constants of Radish Seed Oil GLYCERIDES—SEMI-DRYING OILS XI CASTOR OIL GROUP 413 JAMBO OIL 1 Physical and Chemical Constants of Jarnbo Oil Specific Gravity at 15° C. Solidifying Point. °C. Saponification Value. Iodine Value. Maumene Test. °C. 0-9150-0-9158 -10 to -12 172-26 95-2-95-6 51-53 Physical and Chemical Constants of the Mixed Fatty Acids Solidifying Point. Melting Point. Saponification Value. Iodine Value. °C. °C. Mgrms. KOH. Per cent. 16-11 19-21 173-8-174 96-1-96-2 This oil, obtained from the seeds of a plant belonging to a variety of the genus Brassica , is closely related to rape oil. It is free from sulphur. y. Castor Oil Group In this group are comprised four oils which, in consequence of their very weak drying properties, stand on the borderland between the semi-drying and the non-drying oils. Croton oil and curcas oil resemble castor oil in their medicinal properties and solubilities in alcohol—differing, however, from it in their chemical composition. Castor oil and grape seed oil are remarkable as containing an extremely high proportion of hydroxy acids. All four oils occupy a somewhat exceptionable position as regards their behaviour with solvents. 1 De Negri and Fabris, Annali del Laboratorio delle Gabelle, 1891-92, 137. 414 GLYCERIDES—SEMI-DRYING OILS CHAP. CROTON OIL French— Huile de croton, German— Crotonoel. For table of constants see p. 415. Croton oil is obtained from the seeds of Croton Tiglium. The oil is of amber-yellow, or orange, or brown colour according to age, has a nauseous odour, a burning taste, and is a very powerful purgative. According to Robert 1 there are some kinds of croton oil in commerce that are miscible with alcohol in every proportion. The solubility of different samples, however, varies so much that definite proportions cannot be given. Croton oil is soluble in petroleum ether , differing in this respect from castor oil. According to Peter it is strongly dextro-rotatory. Croton oil has not yet been exhaustively examined. Its chemical composition differs so widely from that of all other oils that its recognition by means of quantitative reactions is easy. The writer has found 0‘55 per cent of unsaponifiable matter in various specimens of croton oil. Croton oil contains the following fatty acids partly as free acids and partly as glycerides : Stearic, palmitic, myristic, lauric, valeric (isobutyl formic), butyric, acetic, formic, oleic, and tiglic. “ Croton- oleic acid,” which was said to constitute the purgative principle of the oil, and had been described as a non-volatile, unsaturated fatty acid, differing from oleic acid in that its barium salt was soluble in alcohol, is, according to Dunstan and Bole, 2 a resinous substance possessing extraordinary power as a vesicant. 3 Croton oil is a weak drying oil; it thickens somewhat on exposure to air ; it yields no elaidin. Castor oil is detected in croton oil, according to Maupy , 4 by heating 10 grms. of the sample in a silver dish with caustic potash; capryl alcohol escapes, recognisable by its characteristic smell, and sebacic acid crystallises from the aqueous solution obtained on boiling the residue with water. 1 Chem, Zeit. 1887, 416. 2 Jour. Soc. Chem. Ind. 1895, 985. 3 Its empirical formula is C ]3 H 18 0 4 ; it is a hard, pale yellow, brittle resin, nearly insoluble i'll water, petroleum ether, and benzene, but easily soluble in alcohol, ether, and chloroform. On heating it softens gradually, and is quite fluid at 90° C. It has neither acid nor basic properties, and is decomposed by boiling with alkalis, yielding a mixture of acids, and losing its vesicating properties. This seems to point to this substance being a lactone or an anhydride. 4 Jour. Phami. Chim. 1894 [29], 362. [Table Physical and Chemical Constants of Croton Oil 416 GLYCERIDES—SEMI-DRYING OILS CHAP. CURCAS OIL (PURGING NUT OIL) French— Huile de mklicinier. German— Curcasoel. For tables of constants see p. 417. Curcas oil is obtained from the seeds of Jatropha Curcas (purging nut). It has a pale colour, but becomes yellow on exposure to air. Its odour is nauseous and slightly acrid. On account of its purging properties it is used in medicine. Of its chemical composition but little is known; it appears to contain ricinoleic acid. According to Bonis it contains the glyceride of isocetic acid (p. 45). Curcas oil differs from castor oil in its behaviour with solvents, being soluble in petroleum ether and insoluble in acetic acid. It is less soluble in alcohol than castor oil, requiring 100 parts of 96 per cent alcohol (De Negri and Fabris). According to Arnaudon and Ubaldini , curcas oil is soluble in cold alcohol, but when treated repeatedly with small quantities of this solvent a residue is left consisting of a solid fatty substance which requires a much larger proportion of alcohol for its solution. The oil obtained from the alcoholic solution, and from which the solid fat had been separated, was found to be more fluid and more readily soluble in alcohol than the original oil. The specific gravity and also the iodine value serve to distinguish this oil from castor oil. Curcas oil has been used to adulterate olive oil (see p. 463). [Table Physical and Chemical Constants of Curcas Oil 418 GLYCERIDES—SEMI-DRYING OILS CHAP. GRAPE SEED OIL French —Huile de raisins. German— Traubenkernoel. For tables of constants see p. 419. Grape seed oil is obtained from grape seeds by expression or by extraction. The figures given in the tables refer to extracted oil. The oil has a greenish-yellow colour, is transparent, and free from odour. It dissolves easily in glacial acetic acid at 70° C.; the solution becomes turbid at 66 ‘5° C. In alcohol it dissolves only partially. Grape seed oil does not dry on exposure to air. The most prominent characteristic of this oil is its very high aeetyl value, placing it, in this respect, in close relationship to castor oil. The occurrence of a large quantity of hydroxy acids renders Fitz’s statement, 1 that grape seed oil contains largely erucic acid, more than doubtful. The sample examined by Horn had the acid value 16'2. Grape seed oil is expressed in various localities, and used as an edible oil and for burning. Horn 2 proposes to use this oil as a substitute for castor oil in the manufacture of turkey-red oil. 1 Berichte, 1871, 444. 2 Mitth. des technolog. Gewerbe-Museums, 1891, 185. [Table Physical and Chemical Constants of Gmpe Seed Oil 420 GLYCERIDES—SEMI-DRYING OILS CHAP. CASTOR OIL French— Huile de ricin. German— Ricinusoel. For tables of constants see pp. 422-424. Castor oil is obtained from the seeds of Ricinus communis. It is imported in large quantities from India, and is also produced on a commercial scale in Java. 1 Castor oil is a colourless or pale greenish, transparent oil, having a taste at first mild, then harsh; this harsh taste is more pronounced in American than in Italian or French oils. It is very viscous, and thickens on exposure to air, finally forming a viscid mass, without, however, solidifying. It does not dry even when exposed in thin layers. According to Peter (p. 120) it is strongly dextro-rotatory. Whereas Allen states that none of the samples examined by him were optically active, Beering and Redwood have recently observed a strongly marked rotatory power in the twenty-three samples of Indian castor oil they examined, the rotation caused by 200 mm. of oil varying from + 7'6° to + 9'7° in a Hoffmann-Laurent polarimeter. These observa¬ tions, in conjunction with the fact that ricinoleic rotates the polarised light, leave no doubt as to the optical activity of castor oil. If castor oil is allowed to stand in a very cool place, 3 to 4 per cent of a solid mass is deposited, consisting, according to Krafft, 2 of tristearin and triricinolein. Palmitic acid is absent, and a small quantity of sebacic acid found is, perhaps, due to a secondary reaction taking place on saponification. Amongst the fatty acids Juillard discovered dihydroxystearic acid (the first natural hydroxy fatty acid) to the extent of 1 per cent. Triricinolein is, according to Krafft , solid in its pure state, and the liquid state of castor oil must be ascribed to a state of superfusion of the oil. Hazura and Griissner, however, have shown that the liquid fatty acids from castor oil consist of two isomerides, ricinoleic and ricinisoleic acids ; perhaps Krafft’s solid acid is identical with one of these acids (cp. also p. 65, Mangold). Olein does not occur in castor oil. 3 Castor oil may therefore be said to consist of a small quantity of tristearin, of the glyceride of dihydroxystearic acid, and the glyceride of ricinoleic acid, all the isomerides being comprised under that term. The amount of free fatty acids in samples of castor oil has been determined by Nijrdlinger, Thomson and Ballantyne, and by Beering and Redwood. Their results are recorded in the following table :— 1 Jour. Soc. Chem. Ind. 1895, 821. 2 Berichte, 1888, 2730. 3 Hazura and Griissner, Jour. Soc. Chem. Ind. 1888, 681. xr CASTOR OIL 421 Free Fatty Acids in Castor Oil Description of Oil. No. of Samples. Free Fatty Acids cal¬ culated to Oleic Acid. Observer. Expressed oil . 9 Per cent. 0-68-14-61 Nordlinger Extracted oil . 5 1-18-5'25 Thomson and Commercial oil 2 1-46-2-16 Indian oils 23 0-14-1-06 Ballantyne Deering and Redwood The amount of unsaponifiable matter in the samples examined by Thomson and Ballantyne varied from 030 to 0 - 37 per cent. The specific gravity of castor oil, its very high viscosity, and its behaviour with solvents, afford ready means of identifying it. Castor oil has the highest specific gravity of any natural fatty oil. The “ blown oils” only (p. 734) have such a high gravity acquired in the course of manufacture. According to A lien, any sample of castor oil having a less specific gravity than 0'958 must be regarded with suspicion. Kesin oil of specific gravity 0 - 998 may have been added to mask the influence of a foreign fatty oil; it can be easily detected by determining the unsaponifiable matter (p. 218). Of all known oils castor oil has the highest viscosity, only “ blown oils” (p. 734) and resin oil approach it in this respect. The viscosity of the twenty-three samples examined by Beering and Piedwood was from 1160 to 1190 seconds for 50 c.c. at 100 F. Castor oil is miscible with glacial acetic acid in every proportion ; it shares this property with croton and olive kernel oils (from which it can, however, be easily distinguished by its acetyl value). Pure castor oil is miscible in every proportion with absolute alcohol ; it also dissolves, at 15° C., in 2 volumes of 90 per cent, and in 4 volumes of 84 per cent alcohol. Itallie 1 has determined the solubility of five samples of castor oil (three of which, A, B, C, had been expressed by himself at the temperatures of 20° C., 50 J C., and 80° C. respectively, whereas D and E were commercial oils) in 90 per cent alcohol, with the following result :— „„ Require 90 per cent Alcohol at 20° C. 10 c.c. of Oil 1 1 c c . A.26-4 B . . . . . . • 26-8 C . . . • • • • 27-8 D . . . . . • • 29-4 E . . . . . • • 24-0 Though oleic acid, fraudulently added to castor oil, would also dis¬ solve in alcohol, it would be easily recognised by the excessive amount of free fatty acids, and by the low specific gravity of the sample. 1 Chem. Zeit. 1890, Rep. 367. 1 Twenty-three samples of Indian oil. Jour, Soc, Chem. Ind. 1894, 959. 2 American oil, which is richer in solid glycerides than Indian or Italian oil. 2 Java oil. 4 Calculated from bromine values, 52‘8-53'7. Physical ancl Chemical Constants of Castor Oil — continued. Physical and Chemical Constants of the Mixed Fatty Acids GLYCERIDES—SEMI-DRYING OILS CHAP. XI CASTOR OIL 425 Castor oil is nearly insoluble in petroleum ether, kerosene, and paraffin oils. At a temperature of 16 C. as little as 0 - 5 per cent of castor oil in these solvents causes a turbidity. However, castor oil gives a homogeneous solution with an equal measure of petroleum ether, or a volume and a half of kerosene or paraffin oil; if more of the solvents is used, any excess will float on the top of the mixture. This characteristic insolubility is lost at the ordinary temperature when castor oil is adulterated with a small quantity of a soluble oil. For the rapid examination of castor oil (as by custom-house officers), Finkener 1 recommends agitation of 10 c.c. of the sample with 50 c.c. of alcohol, specific gravity 0'829 at 17'5 C., in a graduated cylinder. A strong turbidity, which does not disappear even at 20 C., shows that the oil is not pure ; even 10 per cent of foreign oils (as sesame, linseed, rape, cotton seed oils) may thus be detected. Klie employs 5 volumes of alcohol, of specific gravity 0‘8371, for 1 volume of oil at the temperature of 22 to 26 C. Castor oil is distinguished from all other oils—with the exception only of grape seed oil—by its very high acetyl value. The detei- mination of this constant furnishes, therefore, the surest means of ascertaining its purity, and enables the analyst to estimate the amount of adulteration. Also the saponification value (approaching that of the oils belonging to the rape oil group) and the iodine value will afFoid means of detecting fraudulently added oils. W ith regard to the saponification value it may be pointed out that Henriques 2 is of the opinion that castor oil is not so readily saponifiable as is generally believed, and that, therefore, the lower values are open to doubt (cp. table). 3 This is confirmed by the number given by the writer in the table, p. 422. In the elaidin test castor oil gives a whitish solid mass, due to the formation of ricinelaidin Rape oil, resin oil, and especially the “ blown oils prepared from rape, linseed, and cotton seed oils, are used as adulterants of castor oil. Resin oil will be easily detected by determining the unsaponifiable matter. Gilbert’s i test, viz. agitation of the sample with an equal volume of nitric acid of specific gravity 1*31, when castor oil thus adulterated is stated to assume a very dark colour, appears a some¬ what doubtful method. The “ blown oils ” simulate castor oil in specific gravity and viscosity, but they differ from it in having a smaller acetyl value, a higher saponification value (except those prepared from rape oil, cp. p. 305), and lesser solubility in alcohol. Castor oil is easily detected in other oils by its acetyl value and behaviour with solvents (cp. “ Olive Oil,” p. 463). 1 Jour. Soc. Chem. Incl. 1887, 148. 2 Ze.it. f. angew. Chemie, 1895, December. 3 The saponification and iodine values given by Thoerner, viz. 201-203 and 93-94 respectively, are so abnormal that they have been omitted from the table. 4 Jour. Soc. Chem. Ind. 1890, 112. 426 GLYCERIDES—NON-DRYING OILS CHAV. The following qualitative test for castor oil is given by Draper :— Heat a few drops of the oil with five to six drops of nitric acid, and after the action of the acid is over, neutralise with sodium carbonate. As soon as the smell of nitric acid has disappeared, cenanthylic acid may be recognised by its odour. It will be best to make a test side by side with a sample of genuine castor oil. Castor oil is used in medicine, for soap-making, and in the manu¬ facture of Turkey-red oil. (3) Non-drying Oils The general characters of the non-drying oils have been given already (p. 279). The oils described here have been arranged accord¬ ing to their iodine values, in the following order :—Cherry kernel oil, cherry laurel oil, apricot kernel oil, plum kernel oil, peach kernel oil, wheat meal oil, acorn oil, almond oil, sanguinella oil, Californian nut¬ meg oil, arachis oil, rice oil, tea seed oil, pistachio oil, hazelnut oil, olive oil, olive kernel oil, coffee berry oil, ungnadia oil, ben oil, stro¬ phantus seed oil, secale oil. CHERRY KERNEL OIL German— Kirschkernoel. For tables of constants see p. 427. The constants given in the tables refer to extracted oil. Cherry kernel oil is obtained from the kernels of the cherry (Prumis cerasus). The oil has a golden-yellow colour when fresh, and a faint odour of almonds, which it loses in time, turning easily rancid. With nitric acid of specific gravity 1‘4 cherry kernel oil becomes dark reddish-brown ; when tested with Bieber’s reagent (p. 439), a brown colouration is obtained. De Negri and Fabris have found a notable quantity of hydrocyanic acid in the extracted oil. In South Germany (Wiirttemberg) the “ cold-drawn ” oil is used as an edible oil; the oil expressed at a higher temperature serves as a burning oil, and also for soap-making. Owing to its property of turning easily rancid, cherry kernel oil cannot be used to any large extent for the adulteration of almond oil. [Table Physical and Chemical Constants of Cherry Kernel Oil 428 GLYCERIDES—NON-DRYING OILS CHAP. CHERRY LAUREL OIL 1 German— Kirsclilorbeeroel. Physical and Chemical Constants of Cherry Laurel Oil Specific Gravity. Solidifying Point. Saponific. Value. Iodine Value. Maumene Test. At 15” C. ”C. Mgrms. KOH. Per cent. ”C. 0-9230 -19 to - 20 194 10S-9 44-5 Physical and Chemical Constants of the Mixed Fatty Acids Solidifying Point. Melting Point. Iodine Value. ”C. ”C. Per cent. 17-15 20-22 112-1 This oil has been extracted from the kernels of the cherry laurel (Prunus laurocerasus ).. Cherry laurel oil is a transparent oil of golden-yellow colour ; its odour resembles that of bitter almonds. This oil also, like the'pre¬ ceding, contains appreciable quantities of hydrocyanic acid. APRICOT KERNEL OIL French— ILuile d’abricotier. German— Aprikosenkernoel. For tables of constants see p. 429. Apricot kernel oil is obtained from the kernels of the apricot (Prunus Armeniaca). The freshly expressed oil is almost colourless; it becomes, how¬ ever, yellow on keeping. With nitric acid, spec. grav. T4, apricot kernel oil assumes an orange colour. With Bieber’s reagent (p. 439) a peach-blossom colour is obtained ; this was formerly considered characteristic of peach kernel oil, and by means of this colour reaction apricot kernel oil was said to be detected if present in almond oil. The sample of oil (extracted) examined by Micko had fhe acid value 064. Apricot kernel oil is used as an edible oil, and in perfumery like almond oil; it is also employed for adulterating the latter. Apricot kernel oil forms an important article of commerce. 1 De Negri and Fabris, Annali del Laboratorio Chimico delle Gabel!e, 1891-92, 173. Physical and Chemical Constants of Apricot Kernel Oil APRICOT KERNEL OIL 429 u © X © 75 s 1—1 o £ Observer. Beckurts and Seiler Mansfeld g 6 © >a At 25° C. 50 50 lO 50 50 50 © H © Observer. Girard De Negri and Fabris c3 d o 50 ^ CM © © Observer. .g -rH 3 -H S3 QOEcj O So s O Per cent. 100 101 108 © I> o Observer. De Negri and Fabris Micko Valenta _© ’3 o o3* m Mgrms. KOH.

‘o co £* Observer. Schaedler Maben r§ 'o m d ^ O rH (M 1 1 >> > cj o Observer. Schaedler Valenta Maben d rH 1C 02 O a. rH rH (M 02 02 02 < o o o 430 GLYCERIDES—NON-DRYING OILS CHAP. PLUM KERNEL OIL German— Pflaumenkernoel. For tables of constants see p. 431. The constants given in the tables refer both to expressed and extracted oils. Plum kernel oil is obtained from the kernels of plums (Primus domestica and Prunus damascxna). The oil is light yellow in colour, and possesses an agreeable, mild, almond-like taste. With nitric acid, of specific gravity 1*4, plum kernel oil assumes an orange colour (like apricot kernel oil). With Pieter’s reagent, con¬ sisting of equal parts (by weight) of concentrated sulphuric acid, fuming nitric acid, and water, a pink colouration is obtained. The sample examined by Micko had the acid value 0'55. The oil is chiefly used to adulterate almond oil. [Table Physical and Chemical Constants of Plum Kernel Oil 432 GLYCERIDES—NON-DRYING OILS CHAP. PEACH KERNEL OIL German— PjirsichTcernoel. For tables of constants see p. 433. Peach kernel oil (peach oil) is obtained from the kernels of the peach (Amygdalus per ska). The oil has a pale yellow colour, and is very similar to almond oil. With nitric acid peach kernel oil becomes first yellowish-brown, afterwards dirty orange. Tested with Bieber’s reagent it remains un¬ changed for half an hour, and becomes brown after about one hour’s O 1 standing. This oil is chiefly used for adulteration of almond oil; in fact, according to Schaecller, the commercial “ sweet almond oil ” is nothing else than peach oil. [Table Physical and Chemical Constants of Peach Kernel Oil ’ 434 GLYCERIDES—NON-DRYING OILS CHAP. WHEAT-MEAL OIL German— Weizenmehlfett. This oil was extracted from wheat flour. 1 Physical and Chemical Constants of Wheat-Meal Oil Specific Gravity at 100° (water 15° C.=l). Saponification Value. Reichert- Meissl Value. Iodine Value. Refractive Index. At 25° C. 0-9068 166-5 2-8 101-5 1-4851 Butyro-refracto- meter. 92 ACORN OIL 2 German— Eiclieckernoel. This oil is obtained by extracting the fruit of Quercus agrifolia with solvents. It is a deep brown fluorescent oil. On long stand¬ ing it deposits wax. Physical and Chemical Constants of Acorn Oil Specific Gravity at 15° C. Solidifying Point. °C. Saponification Value. Iodine Value. Maumene Test. °C. Refractive Index. 0-9162 10 199-3 100-7 60 1-4731 The melting point of the fatty acids is 25° C. 1 Spaeth, Analyst, 1896, 234. 2 Blasdale, Jour. Soc. Ghem. Ind. 1896, 206. XI ALMOND OIL 435 ALMOND OIL French— Huile d’amandes. German— Mandeloel. For tables of constants see pp. 436-438. Almond oil is expressed [or extracted] from sweet and bitter almonds, the seeds of the two varieties of the almond tree, Prunus amygdalus, var. dulcis and var. amara. Almond oil is a thin oil, of a pale yellow colour and bland taste. The oils obtained from both varieties are very much alike, so much so, that no definite difference has been established by chemical means, as will be seen by glancing at the accompanying table. [The bitter almonds yield more oil than the sweet ones.] Almond oil is very rich in olein. According to Gusserow it is free from stearin; this is confirmed by Idehner and Mitchell} The iodine value points to the presence of glycerides of fatty acids belonging to a less saturated series than the oleic. Almond oil easily turns rancid. A specimen examined by Sal- kowski contained 0*75 per cent of free fatty acids calculated to oleic acid. Tested by the ela’idin test, almond oil from sweet almonds solidifies after about eight to nine hours, whereas the oil from bitter almonds is stated to become ' solid only after twenty-four hours. Since, however, various specimens of oil behave very differently no definite conclusion can be drawn from the behaviour of the oil in this test. Almond oil is adulterated with the following oils : Poppy seed, sesame, walnut, olive, lard, arachis, cotton seed, and (on a very large scale) peach and apricot kernel oils. The last two oils are used to such an extent that they are stated to be wholly substituted for almond oil, so much so, that “ foreign almond oil ” may be considered as wholly consisting of peach kernel or apricot kernel oil. The close relationship in which these two oils stand to almond oil renders it impossible to detect the adulteration by means of the quantitative reactions. According to Allen many of these additions may be detected by observing the absorption spectrum of the sample, almond oil differ¬ ing from most vegetable oils in giving neither a banded spectrum nor producing strong absorption in the red or in the violet. Whereas the specific gravity of a sample may only indicate adulteration with heavier oils, the behaviour of the oil on cooling may lead to the detection of lard oil and also of olive oil, the latter two depositing “stearine” at - 5° C. Lard oil is stated to be indi¬ cated by the odour on heating the sample. 1 Analyst, 1896, 328. From bitter almonds. 2 From sweet almonds. Physical and Chemical Constants of Almond Oil — continued. Physical and Chemical Constants of the Mixed Fatty Acids GLYCERIDES—NON-DRYING OILS CHAr. XI ALMOND OIL 439 The determination of the melting 1 point of the mixed fatty acids also furnishes a valuable means of ascertaining the presence of foreign oils, almond oil being characterised by the low melting point of its mixed fatty acids. According to the German Pharmacopoeia the mixed fatty acids of pure almond oil must remain liquid at 15° C. for an indefinite length of time; mixed with an equal volume of alcohol they must give a clear solution at 15 C., and not become turbid on adding twice the volume of alcohol. Olive, sesamb, arachis, and cotton seed oils may thus be recognised. Peach or apricot kernel oils will, however, escape detection. A higher iodine value than the normal one will point to adultera¬ tion with poppy seed or walnut oils. (Thoerner gives for almond oil the iodine value 82-83, and for the mixed fatty acids 87-90. These figures being so exceptionally low, have not been entered in the table, pending confirmation.) Cotton seed oil may be detected by the nitric acid or silver nitrate test; but the surest test will be afforded by the solidifying point of the mixed fatty acids. Sesame oil will be indicated by the furfurol reaction, rape oil by the decrease of the saponification value, and araehis oil by Eenard’s test (cp. “Arachis Oil,” p. 445). The detection of peach kernel, apricot kernel, and also plum kernel oils in almond oil is a very difficult problem, and is, as has been pointed out already, impossible by means of the quantitative reactions; nor would their presence be indicated by the organoleptic reactions (taste and odour). The nitric acid colour test 1 and Bieber’s test, however, are said to be useful for the detection of these oils. Whereas almond oil remains colourless with nitric acid of specific gravity 1 '4, or becomes only slightly yellow, plum and apricot kernel oils assume an orange colour, and peach kernel oil becomes first yellowish-brown and after¬ wards dirty orange. Biebeds 2 test is carried out by agitating one part of the oil under examination with five parts of a mixture consisting of equal parts (by weight) of concentrated sulphuric acid, fuming nitric acid, and water, when the following colour reactions are stated to appear:— Pure almond oil gives a slightly yellowish-white liniment, chang¬ ing to reddish. Plum kernel oil is characterised by a pink colouration, apricot kernel oil by a peach-blossom colour [ Micko; whilst Bieber ascribes this colouration to peach kernel oil], whereas peach kernel oil (according to Micko) gives no colour after half an hour, and only assumes a light brown colouration after that time. If any sesamS oil be present [which is detected with certainty by the furfurol test] a pale yellowish-red colouration appears at first, changing to a dirty orange-red; in presence of sesame oil, the 1 Micko, Jour. Soc. Chem. Ind. 1893, 935. 2 Zeitsch. f. nnalyt. Chem. 17. 264 ; cp. also Micko, Jour. Soc. Chem. Ind. 1893. 935. 440 GLYCERIDES—NON-DRYING OILS C1IAP. detection of peach kernel oil, in any case a difficult task, would be impossible. Maben 1 recommends for the discrimination of almond, peach kernel, and apricot kernel oils the colour reactions given in the following table:— Almond Oil. Apricot Kernel Oil. Peach Kernel Oil. Elaidin test; product Nitric acid colour test (spec. grav. 1"42) Sulphuric acid colour test Zinc chloride (5 drops of a saturated solution of ZnO in HC1 and 10 drops of oil stirred to¬ gether with a glass rod) White, hard Slight action Yellow to orange No change Light yellow, hard Coffee-brown Light brown to reddish-brown Muddy brown, with shade of purple Lemon-yellow, soft Dark brown Dark brown Purple-brown According to the German Pharmacopoeia, no brown or reddish colouration should appear if five measures of pure almond oil are agitated with one measure of a mixture consisting of two parts of fuming nitric acid and two parts of water; after several hours’ stand¬ ing the fatty layer should form a solid white mass, and the aqueous liquid should be colourless. SANGUINELLA OIL 3 G erman— Hartriegeloel. Physical and Chemical Constants of Sanguinella Oil Specific Gravity at 15° C. Solidifying Point. °C. Saponific. Value. Mgrms. KOH. Iodine Value. Per cent. Maumene Test. °C. 0'921 -15 192-05 100-8 52 Physical and Chemical Constants of the Mixed Fatty Acids Solidifying Point. ° 0 . Melting Point. °C. Saponific. Value. Mgrms. KOH. Iodine Value. Per cent. 31-29 34-37 1951 102-75 This oil is obtained from the seeds of the dog-wood, Cornus sanguinea. It has a green-yellowish colour; its odour is similar to that of inferior olive oil. Phannac. Jour. [3] 16. 797. 2 De Negri and Fabris, Annali, etc., 181. XI ARACHIS OIL 441 CALIFORNIAN NUTMEG OIL 1 Californian nutmeg oil is obtained from the fruit of Tumion Californicum. Physical and Chemical Constants of Californian Nutmeg Oil Specific Gravity at 15° 0. Saponific. Value. Mgrms. KOH. Iodine Value. Per cent. Maumene Test. °C. Refractive Index. 0-9072 191-3 94-7 77 1-4766 The melting point of the fatty acids is 19° C. ARACHIS OIL (PEANUT OIL, EARTHNUT OIL) French— Huile d’arachide. German— Erdnussoel, Arachisoel. For tables of constants see pp. 443, 444. Arachis oil is obtained from the earthnuts, the seeds of Arachis hypogsea (Leguminosse), a plant largely cultivated on the West Coast of Africa, in India, North America, South of Europe, etc. The “ cold-drawn oil ” of the first expression is nearly colourless, and has a pleasant taste resembling the flavour of kidney beans. It is used as salad oil. The oil obtained by second expression also serves as an edible oil or for burning. The third quality expressed at higher temperature is chiefly used for soap-making. Of solid fatty acids, palmitic has been stated by Caldwell 2 to occur in arachis oil. Kreiling 3 could not detect this acid, without, however, having adduced absolute proof of its absence. The same chemist has shown that besides arachidic acid (melting point 74-5° C.), as proved by Gossmann’s researches, another solid fatty acid, of the melting point 81° C., viz. lignoceric acid, occurs in combination with glycerol. Lignoceric acid, being less readily soluble in alcohol than arachidic acid, may be separated from the latter by means of this solvent.— A specimen examined by Hehner and Mitchell 4 gave 7 per cent of stearic acid crystals of the melting point 67° C. The liquid fatty acids of arachis oil consist of oleic and linolic acids. Gossmann and Schevenf and also Schroder , 6 claim to have found the unsaturated fatty acid—hypogseic acid (p. 53). Schoen, 1 however, having been unable to detect this acid, asserts that oleic acid is the 1 Blasdale Jour. Soc. Chem. Ind. 1896, 206. 2 Liebig's Annalen, 101. 97. 3 Berichte, 21. 880. 4 Analyst, 1896, 328. 5 Liebig’s Annalen, 94. 230. 6 Ibid. 143. 22. 7 Ibid. 244. 253; Berichte, 21. 878. 442 GLYCERIDES—NON-DRYING OILS CHAP. only unsaturated acid in arachis oil. Hcizura’s 1 conjecture that hypogseic acid may form a constituent of the unsaturated glycerides in arachis oil is confirmed by the fact that synthetical hypogaeic acid has the same properties as the natural acid found in arachis oil by Gossmann and Scheven, and Schroder (cp. chap. iii. p. 53). A number of samples of arachis oil, examined for the amount of free fatty acids, gave the following result:— Description of Oil. Number of Samples. Free Fatty Acids in terms of Oleic Acid. Observer. Expressed salad oil. 13 Per cent. 0-85 to 3-91 Nordlinger Expressed commercial oil 12 3-58 to 10-61 Extracted oil . 16 0-95 to 8-85 Refined oil 1 0-62 Thomson and Commercial oil 1 6-20 Ballantyne The last two oils in the preceding table contained 0‘54 and 0'94 per cent of unsaponifiable matter respectively. 1 Wiener Monatshefte, 10. 242. [Table Physical and Chemical Constants of Aracliis Oil 5 Bensemann’s method. XI ARACHIS OIL 445 Arachis oil is very similar to olive oil, so much so that it cannot be detected with certainty in the latter by the quantitative reactions, the differences in the iodine values of the two oils not being large enough. Nor are any chromatic reactions available for this purpose. 1 Arachis oil, if present in not too small a quantity in an oil, can how¬ ever be detected with certainty by the isolation of arachidic acid. This test, proposed by Renard , 2 is carried out as follows :—Saponify 10 grms. of the oil, separate the fatty acids from the soap solution by hydro¬ chloric acid, dissolve these in 90 per cent alcohol, and add a solution of lead acetate. I shorten the process by neutralising the excess of alkali with acetic acid, and precipitating with a lead salt without isolating the fatty acids. 3 Filter off the precipitated lead salts, and extract them with ether, thus separating the lead salts of the unsaturated acids from the lead palmitate and arachidate. Treat these latter salts with hydrochloric acid, separate the fatty acids when solidified, after cooling, from the lead chloride, and dissolve them in 50 c.c. of hot 90 per cent alcohol. If arachis oil is present in the sample, a crop of crystals consisting of arachidic acid will be obtained on cooling the alcoholic solution. No doubt the crystals will also contain the lignoceric acid discovered by Kreiling. Filter the crystals off and wash them on the filter, first with a measured quantity of 90 per cent, then with 70 per cent alcohol, which dissolves but small quantities thereof, and finally dissolve them by pouring boiling absolute alcohol on the filter, receiving the filtrate in a porcelain dish or in a flask. Evaporate to dryness and weigh the residue, consisting of crude arachidic acid. Add to the weight thus found the quantity dissolved by the 90 per cent alcohol used for washing, 100 c.c. of which dissolve 0'022 grm. at 15° C., or 0'045 grm. at 20 C. Finally determine the melting point of the crude arachidic acid, which should be from 71° to 72° C. Renard has isolated from 4’5 to 5'0 per cent, Allen 5 - 5, and De Negri and Fabris from 4‘37 to 4 - 80 per cent of arachidic acid from genuine samples of arachis oil. Hence the amount of acid found will represent roughly a of the arachis oil present, and the latter may therefore be approximately calculated by multi¬ plying the weight of the crude acid by 20. Renard’s method being a somewhat tedious one, several authors have proposed shorter processes. Thus Souchere dissolves the mixed fatty acids directly in boiling alcohol. The crystals obtained on cooling are recognised as arachidic acid by their characteristic nacreous lustre. Marie, and also Peters, proceed in a similar way. The method adopted in the Paris Municipal Laboratory is to saponify the sample with an equal weight of an alcoholic potash solution prepared by dis¬ solving 200 grms. of solid caustic potash in 500 grms. of 90 per cent alcohol. The oil is heated with the alcoholic potash on the water-bath 1 A. van Engelen’s “ molvbdic ” reagent (being a solution of 0'25 grm. of sodium molybdate in 20 c.c. of concentrated sulphuric acid) proposed recently (cp. p. 392)- is valueless, on this chemist’s own showing, in the case of a mixture of olive and arachis oils. 2 Oompt. rend. 73. 1330. 3 Kreiss [Jour. Soc. Ghem. Ind. 1895, 688) employs an alcoholic solution of lead acetate. 446 GLYCERIDES—NON-DRYING OILS CHAP. from 30 to 45 minutes, and allowed to cool down to a temperature between 0° and 6° C. In presence of as small a quantity as 5 per cent of arachis oil, there separate on the walls of the vessel granular masses of potassium arachidate which are insoluble in alcohol. Larger quantities of arachis oil are indicated by solidification of the whole mass. Be Negri and Fabris, 1 after having examined these abbreviated methods, state that they yield uncertain results, a conclusion which is also arrived at by Holde} The original method of Renard is there¬ fore recommended by these authors as giving the most reliable results. The small quantity of arachin naturally occurring in olive oil does not interfere with the correctness of the method. Ponzio has recently stated that rape oil also contains arachidic acid (04 per cent, and not 4 per cent as given in the original paper in consequence of a clerical error). I have examined rape oil by Renard’s test, but the quantities of arachidic acid were so small that they cannot vitiate this method for the detection of arachis oil. Be Negri and Fabris have examined mixtures of olive oil and arachis oil, obtaining the following numbers :— Sample Containing Arachidic Acid Found Arachis Oil Olive Oil. Arachis Oil. Weighed as Crystals. Calculated as Dissolved. Total. Per cent. Per cent. Per cent. Grms. Grms. Grms. 70 30 0-107 0-0315 0-1385 29-08 80 20 0-0605 0-0315 . 0-0920 20-24 85 15 0-0385 0-0315 0-070 14-00 90 10 0-0200 0-0315 0-0515 10-30 90 ID non-weighable 90 10 0-0280 0-0154 0-0434 9-54 90 10 non-weighable It will thus be seen that on employing 10 grms. of the sample, the limit is reached if it contain only 10 per cent of arachis oil. Holde recommends, therefore, that 40 grms. of the oil should be taken. Herz 3 states that arachidic acid can be recognised with certainty under the microscope by the characteristic habitus of its crystals when allowed to crystallise from its alcoholic solution on an object glass. The safest plan will be to compare the crystals obtained with those similarly prepared side by side from a specimen of pure arachidic acid. Arachis oil is adulterated with poppy seed, sesam.6, cotton seed, and rape oils. Poppy seed oil would be detected by the specific gravity 1 Annali del Laboratorio Chimico delle Gabelle, 1891-92, 123. 2 Jour. Soc. Chem. Ind. 1891, 952. 3 Repert. Anulyt. Chemie, 1886, 604. XI RICE OIL—TEA SEED OIL 447 and the iodine value of the sample; sesame oil by the furfui'ol reaction, cotton seed oil by the melting point of the fatty acids and perhaps also by the chromatic reactions, and rape oil by the saponification value of the oil and the melting point of its fatty acids. RICE OIL 1 German— Eeisoel. Saponification Value. Iodine Value. 193-2 96-4 This oil, obtained from Rangoon rice meal by hydraulic pressure, had a dirty greenish colour, and in part solidified at the ordinary temperature. The oil appears to be remarkable for the large proportion of free fatty acids it contains, viz. from 31‘6 to 77‘20 per cent. Rangoon rice meal contains about 15 per cent of oil, common rice meal only 8-9 per cent. TEA SEED OIL German— Theesamenoel. For table of constants see p. 448. Tea seed oil is the oil obtained from the seeds of the tea plant, Camellia theifera, which is expressed on a large scale in China; the finest quality serves there as an edible oil, and the lower as burning oil and for soap-making. There are two varieties, viz. Chinese and Assam oil. Tea seed oil is a limpid, straw or amber coloured yellow oil, closely resembling olive oil; like the latter it gives a hard elaidin. Similar to this oil is the fatty oil from Camellia oleifera, a plant largely cultivated in China for the sake of the pale bland oil prepared from its seeds. Its specific gravity is 0‘9175 at 15° C. ( Scliaedler). 1 Smetham, Jour. Soc. Chem. Ind. 1893, 848. [Table Physical and Chemical Constants of Tea Seed Oil GLYCERIDES—NON-DRYING OILS CHAP. XI PISTACHIO OIL—HAZELNUT OIL 449 PISTACHIO OIL 1 German— Pistazienoel. Physical ancl Chemical Constants of Pistachio Oil Spec. Grav. Solidifying Point. Saponification Value. Iodine Value. Maumene Test. At 15° C. °C. Mgrms. KOIi. Per cent. °C 0-9185 -8 to -10 191-0-191-6 86-8-87-8 44-5-45 Physical and Chemical Constants of the Mixed Fatty Acids Solidifying Point. Melting Point. Iodine Value. °C. °C. Per cent. 13 17-18 \ 88-9 14-13 18-20 J This oil is contained in the seeds of the pistachio nuts (from Pistacia vera or P. lentiscus). As it has no commercial value it may suffice to record the constants only. HAZELNUT OIL French— Haile de noisette. German— Haselnussoel. For tables of constants see p. 450. Hazelnut oil is prepared from the seeds of the hazelnut tree, Corylus Avellana, by pressing, or by extracting with solvents. This oil has a golden-yellow colour; it is transparent, and has the odour of hazelnuts. For want of better methods this character¬ istic odour must be used for its detection in other oils. According to Schaedler it contains a minute quantity of arachin. In the elaidin test it yields a solid white mass. Hazelnut oil resembles almond oil very closely, their mixed fatty acids behaving similarly with alcohol; its lower iodine value, how¬ ever, may be used for discriminating it from almond oil. According to Filsinger 2 hazelnut oil is used to adulterate choco¬ late. Hazelnut oil is used in perfumery. In its turn it is liable to adulteration with olive oil; this would be detected by the high solidifying point of the sample. 1 De Negri and Fabris, Jour. Soc. Chem. Ind. 1893, 453, 2 Jour. Soc. Chem. Ind. 1893, 51. XI OLIVE OIL 451 OLIVE OIL French— Iiuile d’olive. German— Olivenoel. For tables of constants see pp. 454-456. Olive oil is prepared from the fruits of the olive tree, Olea europsea sativa, by expression or by extraction. The specimens of olive oil found in commerce vary to a consider¬ able extent, their quality depending on many circumstances, such as the variety of the olive itself [Italy alone produces about 300 varieties of the olive tree], the degree of ripeness of the fruit, the manner of gathering it, the mode of expressing, and many others. The very finest oils, prepared from handpicked fruits—virgin oil, Provence oil, Aix oil—are used as best edible oils; next in quality rank the oils sold in this country as “ Finest Tuscan cream.” A somewhat inferior quality is also used as salad oil; the next lower grade oil serves as burning oil and for soap-making; for the latter purpose especially those oils are employed which have been recovered from the once or twice expressed marc, by mixing with a small quantity of water (“lavate” oils) and grinding it up, crushing at the same time the olive kernels. Lower grades still, partly obtained by ex¬ traction of the press residues with solvents (carbon bisulphide or petroleum ether), are met with in commerce under the name of Indies de ressence, Indies d’enfer (from marc fermented in pits), sottochiari, sulpho-carbon oils, etc. “ Tournant oil ” is a commercial product of the quality of the “ huiles d’enfer,” obtained from the fermented marc of expressed olives, and containing a large quantity (up to 26 per cent) of free fatty acids. It possesses, therefore, the property of giving a very complete emulsion with a solution of sodium carbonate, and this constitutes its value as Turkey-red oil (p. 464). Still lower qualities contain more fatty acids. Thus a sample of “ olive oil grease” examined in the writer’s laboratory had 48 per cent of free fatty acids. The colour of olive oil naturally varies considerably, all shades from colourless to golden-yellow occurring ; some kinds are always green, due to a small proportion of dissolved chlorophyll. The taste of olive oil in its purest state is bland and pleasant, varying, however, with the locality where the fruit has been grown. Thus, the oils obtained from Tuscan fruits possess a decidedly more agreeable taste than those from Ligurian olives. Therefore purity alone is not sufficient for the valuation of a sample of olive oil. An oil may be free from adulteration and still be an inferior oil, on account of its rank and even nauseous taste. Olive oil contains about 28 per cent of solid glycerides, consisting of palmitin and a minute proportion of arachin. Hehner and Mitchell 1 1 Analyst, 1896, 328. 452 GLYCERIDES—NON-DRYING OILS CHAP. did not obtain any stearic acid crystals from olive oil, therefore absence of stearin must be taken as proved. The rest—about 72 per cent—was formerly considered to be practically pure olein (notwithstanding a conjecture of Mulder's as to the presence of an unsaturatecl fatty acid other than oleic), but Hazura and Grilssner have shown that the liquid portion contains, besides oleic acid, the less saturated linolic acid (approximately in the proportion of 93 oleic acid to 7 linolic acid). This fact is in complete harmony with the somewhat high iodine value of olive oil. Since, according to theory, pure olein absorbs only 86-2 per cent of iodine, the corresponding absorption of olive oil should be equal to 62 per cent for a proportion of 72 per cent of olein. Experiments, however, give far higher iodine absorptions (cp. table p. 455). The unsaponifiable matter occurring in olive oil is cholesterol, whereas all other vegetable oils contain phytosterol. Thomson and Ballantyne found in 12 samples of oil the proportion of unsaponifiable matter between 1-04 and 1"42 per cent. Varying amounts of free fatty acids have been found in com¬ mercial olive oils. The following table gives the results published by several chemists :— Free Fatty Acids in Olive Oil Description of Sample. Number of Samples. Free Fatty Acids as Oleic Acid. Observer. 1 Per cent. 1-17 Salkowski 1 1-66 Rechenberg Commercial oil 49 Less than 5 Archbutt 66 5-10 » > 44 10-15 > > 1 20-25 11 3-86-11-28 Thomson and ,, ,, (Syrian) 1 23'88 Ballantyne » > ,, ,, (Californian 3 1-55-8-33 Moerck ,, ,, (European) 3 0-97-1-09 J ) Olive oils containing more than 5 per cent of free fatty acids are, according to Allen, not suitable for lubricating purposes; they are also unsuitable as burning oil, causing charring of the wick [Archbutt). Olive oil must be considered as the type of a non-drying oil. Hence it gives in MaumenS’s test, as also in the heat of bromination test, of all vegetable oils the smallest rise of temperature, and shows also the lowest absorption of oxygen in Livache’s test (p. 287). On account of its comparatively high price olive oil is adulterated to an enormous extent. The oils mostly admixed with it are sesame, XI OLIVE OIL 453 rape, cotton seed, poppy seed, and arachis oils. The olive oils sold under fancy names are, as a rule, adulterated. Thus a “ sweet nut oil ” consisted of a mixture of olive and arachis oil, and a “ Union salad oil ” was found to be almost pure cotton seed oil. The importance of the examination of olive oil may justify our dealing with it at some length. At the same time the following lines may illustrate the way in which the methods, discussed in chap, ix., are employed for the commercial analysis of an oil, with a view to ascertaining the presence of adulterants. [Table Physical and Chemical Constants of Olive Oil 11 Virgin oil." 2 Gallipoli oil. 3 Commercial oil. 4 Derived from observations on 203 samples. 5 Californian oils. 6 Dark oil. 7 Derived from observations on 106 samples. 8 Jour. Soc. Chem. Ind. 1895, 206. 1 Derived from observations on 203 samples. 2 Finest Tuscan cream. 3 Commercial oil. 4 Gallipoli oil. 5 Californian oils. 6 Jour. Soc. Chem. Ind. 1896, 206. XI OLIVE OIL 457 The specific gravity of olive oil ranges from 0-914 to 0 917 at 15° C., but may rise to 0-920, and even 0‘925 in the case of com¬ mercial oils expressed at a higher temperature, owing to their larger proportion of palmitin. These oils are mostly recognisable by their darker colour. Free fatty acids in the oil cause, as a rule, a depression of the specific gravity. If the specific gravity of a pale olive oil be found higher than 0*917, it must be looked upon with suspicion, and as possibly adulterated with sesamd, cotton seed, or poppy seed oil. Sophistication with rape or arachis oil is, however, not indi¬ cated by the specific gravity, the differences in their respective gravities being too insignificant. Special araeometers—oleometers—have been designed for the testing of olive oil, as those of Lefebre, Gobley, Fischer, giving either the specific gravities directly or in “ degrees ” calculated in different ways (p. 124). Some of these araeometers bear also marks indicating the point to which the hydrometer dips in other oils. Souchbre 1 has determined by means of Lefebre 1 s oleometer (which is in use in France) the specific gravities of olive oil mixed with various proportions of other oils. His numbers are reproduced in the follow¬ ing table :— Kind of Oil. Specific Gravity at 15° C. Pure Oil. Olive Oil containing 10 Per cent. 20 Per cent. 30 Per cent. 40 Per cent. 50 Per cent. Olive oil . Colza oil . Sesame oil Cotton seed oil Arachis oil 0-9153 0-9142 0-9225 0-0230 0-9170 0-91519 0-91602 0-91607 0-91547 0-91508 0-91674 0-91684 0-91564 0-91497 0-91741 0-91761 0-91581 0-91468 0-91818 0-91838 0-91598 0-91475 0-91890 0-91915 0-91615 Souchbre thinks that it is not only possible to discriminate olive oil from other oils by means of Lefbhre’s oleometer, but also to deter¬ mine quantitatively the proportion of the foreign oil added, provided the nature of the latter be known. This statement, however, is decidedly misleading as regards rape (colza) and arachis oils, and for the other oils is, to say the least, doubtful. The solidifying point is also characteristic of olive oil. On referring to the table given on page 259 it will be seen that olive oil has of all vegetable oils the highest solidifying point. According to Serra Carpi, 2 the degree of hardness of the solidified olive oil may also serve for the detection of foreign oils, inasmuch as the latter are far softer than olive oil at - 20° C. Carpi’s test is carried out as follows:—The sample of oil is cooled down to - 20 C., and kept at 1 Moniteur scientif. 11. 791. 2 Zeitsch. f analyt. Ghemie, 23. 566. 458 GLYCERIDES—NON-DRYING OILS CHAP. that temperature for three hours. A cylindrical iron rod, conical at the bottom, 1 cm. long and 2 mm. thick, is then placed, by suitable means, on the solidified fat, and weights are put upon it until it sinks in the oil. His results are given in the following short table :— Kind of Oil. Weights required. Grins. Purest olive oil . . . . 1700 Commercial olive oil . .Not quite 1000 Cotton seed oil ... 25 The apparatus designed by Legler might be advantageously used for this purpose (p. 103). It should, however, be noted that the solidifying point of mixtures of olive oil with other oils does not give any positive results. 1 As a rule a mixture of olive oil with other oils will have a lower melting point than either of these oils. The melting and solidifying points of the fatty acids (or titer test) will also furnish useful indications as to the purity of the oil, as reference to the table given on page 260 will readily show. A good plan is to test the sample side by side with specimens of pure oils. Bach has determined the melting points of the mixed fatty acids from pure olive oil, and from mixtures of olive oil with other oils :— Mixed Fatty Acids from Melting Point. °C. Solidifying Point. °C. Pure olive oil ..... 80 parts olive oil, 20 parts sunflower oil . 80 ,, ,, 20 ,, cotton seed oil. 80 ,, ,, 33£ ,, rape oil . 26-5-28-5 24 31-5 23-5 Above 22 18 28 16-5 Dieterich, however, states that additions of foreign oils amounting to less than 25 per cent cannot be detected with certainty. Hence this method is not of much importance, since sophistication with so large quantities can be detected more easily by other means. Dieterich has recorded the melting points of the following mixtures of fatty acids from olive oil with the fatty acids derived from other oils :— Mixed Fatty Acids from Pure olive oil (mean of 17 samples) 75 parts of olive oil and 25 parts of arachis oil . 75 ,, ,, ,, 25 ,, cotton seed oil 75 ,, ,, ,, 25 ,, sunflower ,, 75 ,, ,, ,, 25 ,, sesame ,, 75 ,, ,, ,, 25 ,, linseed ,, 75 ,, ,, ,, 25 ,, rape ,, Melting Point. °C. 26-28-5 29 30 25 28 24-5 23 Solidifying Point. °C. 23 5-24-6 26 27-3 20-5 25 19-5 19 1 Cp. Goldberg, Jour. Soc. Cheru. Ind. 1897, 447. XI OLIVE OIL 459 The electrical conductivity of olive oil being considerably less than that of any other vegetable oil—according to Rousseau 675 times less than that of the next oil in point of low conductivity the determination of that physical constant should easily allow definite conclusions to be drawn as to the purity of a sample. Palmieti s “ Diagometer ” has been specially constructed for the examination of olive oil. This method, however, has not yet come into practical use, but it may be hoped that, since the determination of this physical constant has recently been introduced to chemical laboratories as a means of determining the constitution of chemical compounds, a simple apparatus may be devised for the examination of oils. A glance at the table given (p. 275) will show that Herlants method (chap. v. p. 122) may prove of use in this direction. Olive oil has also of all vegetable oils the smallest refractive power (cp. p. 262). Leone and Longi have proposed to examine olive oil for adulterants, especially for cotton seed and sesamd oils, by deter¬ mining the refractive index of the oil. The results obtained will, however, hardly repay the trouble involved, inasmuch as only large proportions of foreign oils can be detected by this means, and other methods give much more definite indications. Amagat and Jean’s oleo-refractometer, 1 however, seems to lend itself with more advantage to the optical examination. As has been stated by Oliveri , 2 the deviation of a very large number of samples, of olive oil ranged from + 1 and + T50. The following table contains Oliveri’s results :— Kind of Oil. Olive (106 samples) Cotton seed Sesame Colza Arachis . Poppy seed Castor Deviation. 0 to 2 18 15-5 26-5 7‘5 28-5 41-44 3 A sample consisting of two oils, having the deviations D and D^, and mixed in the proportion of m and n per cent respectively, would have a deviation equal to no -rx io -p. Too D x Too l * Thus a mixture of 80 parts of olive oil (deviation 1) with 20 parts of cotton seed oil (deviation 18) showed a deviation of 80 . _ 2 ^-18 = 4-4 Mixtures of olive oil with any considerable 100 100 i . quantity of the above-named oil will, as a rule, show deviations exceeding + 2, the limit stated above. Adulteration with arachis oil, 1 Gazz. Chimica, 16. 393. 2 Jour. Soc. Chem Ind. 1894 45. 3 Castor oil has been used to adulterate olive oil (Di Vetere and Leonarch). Cp. also Jour. Soc. Chem. Ind. 1894, 961, 981. 460 GLYCERIDES—NON-DRYING OILS CHAP. however, may still escape detection, since a mixture of 25 parts of aiachis oil with 75 parts of olive oil—deviation 0*25—would pro¬ duce a deviation of + 2°. Zeiss s butyro-refractometer will, of course, prove itself equally useful. According to Guezclenovic, Dalmatian oils appear to have abnormal refractive power (cp. also table, p. 455). Behaviour with Solvents. —Olive oil being but slightly soluble in absolute alcohol (3‘6 in 100), can be distinguished by means of that solvent from castor and olive kernel oils; its solubility in glacial acetic acid may help to detect rape or hedge radish oil. The behaviour of olive oil fatty acids with a mixture of alcohol and acetic acid has been detailed above (p. 272). It should, however, be borne in mind that smaller quantities than 25 per cent of cotton seed or sesarnd oil cannot be thus detected \ if larger quantities be present in the sample granular precipitates are obtained. This test is less reliable still in the case of rape oil, addition of over 50 per cent only being recognisable. The insolubility of arachidic acid in cold alcohol allows its isolation from the other mixed fatty acids (cp. test for arachis oil). Of the quantitative reactions the most important is the iodine test, constituting, as it does, the most valuable means of detecting adulteration. Olive oil has nearly the lowest iodine absorption of any oil that might be used for adulteration. As a rule, the iodine value of olive oil should be from 8T6 to 84‘5. There are, however, undoubtedly genuine oils, the iodine number of which reaches 86 (from the Colombaio olive), and even 88, as in the case of Californian pil* Still these cases are notable exceptions, and an oil with an iodine value of more than 85 must be looked upon with suspicion. The extraordinarily high iodine values of four Dalmatian oils (see table, p. 455) should stimulate further investigation. If there is reason to exclude abnormal oils, a higher iodine absorp¬ tion may indicate adulteration with as little as 5 per cent of a drying oil (poppy seed, hemp seed oil) or 15 per cent of sesamd, cotton seed, and mpe oils. Less positive results are obtained in the presence of aiachis oil, the lowest values recorded for that oil almost coinciding with the highest given for olive oil. Paparelli 1 has studied the causes of the variability of the iodine values, and arrives at the following conclusions :—The more mature the olives are the higher is the iodine absorption of the oil. Old and rancid oil has generally a slightly lower number. The method of preparing the oil has also its influence. Oil from the pulp shows slightly lower iodine absorption than that obtained by grinding pulp and pits together; oils extracted by solvents show lower values than the same obtained by pressing; oils from pits are, again, characterised by higher numbers than those extracted from the fruit. The greatest variation, however, is found to be due to the variety of the olive from which the oil is made. 1 Jour. Soc. Chem. Iml. 1892, 848. xr OLIVE OIL 461 It may be pointed out here that the iodine values of the semi-solid and the liquid portions into which olive oil separates on partial solidification almost coincide {Goldberg). 1 The saponification value will only lead to definite results if large quantities of rape oil be admixed with the sample. In the elaidin test olive oil yields the hardest elaidin of all oils, and also requires the shortest time for solidification. The effect of an addition of rape or cotton seed oil to olive oil is shown in the following table compiled from tables published by Archbutt ,- 2 — Kind of Oil. Minutes required for Solidification, at 25° C. Consistency. Olive oil ..... Olive oil+ 10 per cent of rape oil „ +20 „ ,, +10 ,, cotton seed oil . ,, +20 ,, 230 320 From 9 to 11| hours From 9 to ll| hours More than 114 hours Hard, but penetrable j Buttery \ Very soft J butter The effect of a foreign oil on the hardness of the ela'idin can be measured quantitatively by using Legler’s method (p. 103). It should, however, be borne in mind that, according to Gintl (p. 282), olive oil, after exposure to sunlight for a fortnight, no longer gives a solid elaidin. The thermal reactions give lower values than any other vegetable oil. Lengfeld and Paparelli assert that there exists a pro¬ portionality between the iodine number and the Maumene test of various olive oils. They obtained for fourteen oils numbers varying from 33-5 to 41 C. (compare also table, p. 455), the oil possessing the highest iodine absorption giving the greatest rise of temperature. Their results, arranged by the writer according to the iodine values, do not, however, bear out fully the correctness of this rule. Olive Oil, No. Iodine Value. Per cent. Maumene Test. °C. 1 77-28 35 2 78-42 33-5 3 78-51 33-5 4 78-52 34 5 79"50 36 6 79-53 34-5 7 80-80 37 8 81-45 38 9 ■ 81-50 35 10 81-70 34 11 83-35 37-5 12 85-44 36-5 13 87-15 41 1 Jour. Soc. Chem. Ind. 1897, 447. 2 Ibid. 1886, 308. 462 GLYCERIDES—NON-DRYING OILS CHAP. The proportionality between iodine number and heat of bromina- tion test shows in a general way the same regularity, as will be seen from the numbers given in the following table ( Archbutt *):— Olive Oil. Iodine Value. Per cent. Heat of Bromination. “C. Malaga 78-4 14-2 78'7 13-55 78-9 13-8 Malaga 79-3 13-8 81-4 14-2 81'4 14-35 Gallipoli 82'0 14-4 82-1 14-5 82-5 14-5 84-2 14-45 The unsaponifiable matter in olive oil is, as a rule, below 1 per cent.' 2 The phytosterol reaction has been proposed by Salkowski as a means of detecting seed oils in olive oil, the latter containing but very minute quantities of phytosterol in contradistinction to the former. 50 grms. of olive oil do not yield a quantity of phytosterol sufficient for the determination of its melting point. Hehner recom¬ mends this test especially for the detection of cotton seed oil. The colour reactions proposed by various authors are altogether unreliable and yield no definite results, with the exception of the colour test for sesamS oil, and perhaps also those for cotton seed oil (see below). A curious reagent, consisting of egg-albumen and nitric acid, has been proposed by BrulU 3 for the rapid detection of seed oils. 0T grm. of egg-albumen, 2 c.c. of nitric acid (specific gravity ?), and 10 c.c. of the sample, are placed in a test-tube and gently warmed over a spirit lamp, so that acid and oil have the same temperature. The albumen gradually dissolves in the oil. Whereas pure olive oil thus treated assumes a yellow colour with a faint greenish tint, an oil adulterated with only 5 per cent of a seed oil becomes distinctly amber-yellow, and, in the presence of larger quantities of the latter, dark orange. Jean states that this process gives reliable results, whilst Holde rejects it as absolutely untrustworthy. BrulU himself appears to have abandoned this “ albumen test,” as he adopts in his later publications a modification of Becchi’s test for cotton seed oil. His colour reactions, however, stand greatly in need of confirmation, and the reader must therefore be referred to the original papers and table. 4 1 Jour. Soc. Chem. Ind. 1897, 311. 2 It should be noted that in Germany commercial oil is denatured with rosemary oil, which of course increases the amount of unsaponifiable matter. 3 Jour. Soc. Chem. Ind. 1888. 457. 4 Ibid. 1890, 924 ; 1891, 390. XI OLIVE OIL 463 Green olive oils should be tested for copper, some specimens of “ Malaga oil ” being coloured green by admixture with copper acetate. Cailletet 1 detects the copper by agitating 10 c.c. of the sample with 5 c.c. of ether, in which 0T grm. of pyrogallol has been previously dissolved, when presence of copper will be indicated by the mixture becoming brown with separation of copper pyrogallate. Pure oils are not discoloured, nor do they become turbid. Copper may also be detected in the manner described above (p. 98). In conclusion, we collate the tests useful for the detection of oils occurring as adulterants in commercial olive oils :— 1. Araehis Oil. —Iodine absorption ; as a rule, higher than that of normal olive oil. Detection of arachidic acid (see “ Araehis Oil,” p. 445). 2. Sesamd Oil. —Specific gravity ; solubility of fatty acids ; iodine absorption; and, as most characteristic, Baudouin’s test as modified by Villavecchia and Fabris (see “ Sesame Oil ”) in order to avoid errors that might possibly be caused by abnormal oils, such as Tunisian, etc. 3. Cotton Seed Oil. —Specific gravity; melting point of fatty acids, behaviour of fatty acids with solvents, iodine absorption, Livache test; nitric acid colour test; Becclii’s test (see “ Cotton Seed Oil ”); phytosterol test (p. 317). 4. Rape Oil. —Iodine absorption ; melting and solidifying points of the mixed fatty acids; behaviour of the mixed fatty acids with solvents; saponification value. ( Palas’ colour reaction 2 cannot be recommended, cp. p. 406.) Presence of sulphur will not always, as has been assumed until recently, indicate rape oil without fail, since on the one hand the “ cold-drawn ” oils from seeds of Crucifers are free from sulphur, and on the other hand olive oils extracted by carbon disulphide (sulpho- carbon oils) give the reactions characteristic of sulphur. These sulpho-carbon oils possess a dark colour and an unpleasant smell, and dissolve easily in alcohol. They are thereby, and more especially by their iodine absorption, easily distinguished from rape oil. Sulphur not being a constitutive element of rape oil, the colour test proposed by Schneider, and stated to detect the presence of even 2 per cent of rape oil in olive oil, is valueless. Besides, cotton seed oil may give a similar reaction. Schneider’s test is as follows :—Dis¬ solve one volume of the sample in two volumes of ether, and add 20-30 drops of a saturated alcoholic solution of silver nitrate ; the lower layer becomes brownish and at last black, if rape oil is present in large quantity, if in small quantity, distinctly brown after twelve hours’ standing. 5. Castor Oil. —Specific gravity ; behaviour with solvents; acetyl value. 6. Cureas Oil (used in Portugal, according to Iiiepe, to adulterate olive oil).—Iodine absorption ; saponification value. Admixtures of even 10 per cent are said to be detected by the intense reddish-brown 1 Zeitsch. f. analyt. Chemie, 18. 628. 2 Jour. Soc. CTiem. Ind. 1897, 361. 464 GLYCERIDES—NON-DRYING OILS CHAP. colouration the sample will assume a short time after treatment with nitric acid and metallic copper. 7. Lard Oil (the price permitting).—Melting point of fatty acids ; viscosity; odour of lard on warming. 8. Drying Oils. —Iodine value. Thermal tests. Livache test. 9. Fish Oils. —Iodine test; taste and smell. 10. Hydrocarbons.-— Determination of unsaponifiable matter. Adulterants falling under this class are: colourless vaseline and mineral oils. Turkey-red oil (Tournant oil) is tested for the percentage of free fatty acids, which should be present to the extent of about 25 per cent, calculated as. oleic acid. Adulterations may be detected by the iodine test. A complete analysis of an adulterated Turkey-red oil is given below (chap. xiii. p. 811). OLIVE KERNEL OIL German— Olivenkernoel. Physical and Chemical Constants of Olive Kernel Oil Specific Gravity. Saponification Value. Iodine Value. Acetyl Value. At 15° C. Observer. Mgrms. KOH. Observer. Per cent. Observer. Observer. 0-9202 Yalenta 188-5 Yalenta 81-8 Hiibl 22-5 Benedikt Olive kernel oil is the oil obtained by pressing or extracting from the seeds of the olive kernels. This oil differs from olive oil by its dark greenish-brown colour, and by being more readily soluble in alcohol and acetic acid. [This is, no doubt, due to the large quantity of free fatty acids in the oils. Thus a sample examined by Benedikt had the acid value 90‘L] The oil is, however, not miscible with absolute alcohol in every pro¬ portion like castor oil. Thus a sample of olive kernel oil, on being mixed with 3'5 volumes of absolute alcohol, gave a clear solution, whereas with 4 volumes it gave a slight, and with 5 volumes a strong turbidity which, however, disappeared on adding more alcohol. In other respects—ela'idin test, iodine absorption, etc.—the oil resembles olive oil closely. Olive kernel oil naturally occurs in those olive oils obtained from olive marc crushed with the kernels. Physical and Chemical Constants of Coffee Berry Oil 466 GLYCERIDES—NON-DRYING OILS CHAP. Coffee berry oil—extracted by means of ether from the coffee belies—has an intense greenish-brown colour; it possesses a faint odour of raw coffee. By roasting the berries the oil is very little changed. The samples examined by Spaeth contained from 2‘25-2’29 per cent of free acid, calculated as free acid. According to Hilger, coffee berry oil consists of olein and small quantities of palmitin and stearin. 1 UNGNADIA OIL 2 Physical and Chemical Constants of Ungnadia Oil Specific Gravity. Solidifying Point. Heliner Value. Saponification Value. Iodine Value. At °C. • °c. Per cent. Mgrms. KOH. Per cent. 15 100 0-9120 0-8540 -12 9412 191-192 81-5-82 Physical and Chemical Constants of the Mixed Fatty Acids Solidifying Point. Melting Point. Iodine Value. °C. °C. Per cent. 10 19 86-87 Ungnadia oil is obtained from the seeds of Ungnadia speciosa, a tree indigenous in Texas. The oil is limpid, and is remarkable (like ben oil) in not easily turning rancid. 1 Chem. Zeit. 1895, 776 (Heliner and Mitchell’s method was not known then). 2 Schaedler, Pharmac. Zeitung , 1889, 340. [Table XI BEN OIL—STROPHANTUS SEED OIL 467 BEN OIL French— Iluile de ben. German— Behenoel. Physical and Chemical Constants of Ben Oil Specific Gravity. Solidifying Point. Iodine Value. 1 At 15° C. Observer. °C. Observer. Per cent. Observer. 0-9120 0-9198 2 0-9161 3 Chateau Mills >> Solidifies completely at 0 ; deposits crystals at 7 Chateau 84-1 2 80-8 3 Mills Ben oil is prepared from the seeds of the ben nut from Moringa oleifera. This oil has a slightly yellowish colour, is odourless, and has a sweet taste. On standing it separates into a solid and a liquid portion. Ben oil consists of the glycerides of oleic, palmitic, and stearic acids, and of a solid acid of high melting point; according to FolJcer, this is identical with behenic acid, melting point 76° C. [arachidic acid ?] It appears strange that, according to Mills , the specimen of oil containing much solid fat should absorb more iodine than the oil free from solid fat. In the East ben oil serves as a cosmetic, and used to be employed in the “ maceration ” process for extracting perfumes from flowers, The liquid portion of the oil becomes rancid only after long exposure, and therefore this oil is very valuable for lubricating watch springs. STROPHANTUS SEED OIL 4 German— Strophantusoel. Physical and Chemical Constants of Strophantus Oil Specif c Gravity at 13° C. Hehner Value. Saponification Value. Keichert-Meissl Value. Iodine Value. 0-9254 95-3 187-9 0-5 73-02 The melting point of the fatty acids was 28°-30 C. This oil was obtained from the seeds of Strophantus hispidus. 1 Calculated from bromine value. 2 Containing much solid fat. 3 Containing no solid fat. 4 Mjoen, Archiv. d. Pharmacie, 1894 (234), 283. 468 GLYCERIDES—MARINE ANIMAL OILS CHAP. SECALE OIL 1 German— Mutterkornoel. Physical and Chemical Constants of Secale Oil Specific Gravity at 13° C. Hehner Value. Saponification Value. Reichert-Meissl Value. Iodine Value. 0-9254 96-3 178-4 0-20 71-08 The melting point of the fatty acids was 39‘5°-42° C. Secale oil was obtained from Secale cornutum. 2. ANIMAL OILS Under this section we shall describe the oils obtained from animals, dividing them into two groups— (1) Marine animal oils, and (2) Terrestrial animal oils. This subdivision is not made merely for the sake of convenience; it is based on striking chemical differences. Broadly speaking, these two groups may be compared with the two large groups of vegetable oils : the drying and the non-drying oils. Like the drying oils the marine animal oils are characterised by very high iodine values, by their rapid absorption of oxygen, and by not yielding elaidins. On the other hand, the terrestrial animal oils compare with the non-drying oils in that they have low iodine values, do not easily absorb oxygen, and yield solid elaidins. Just as amongst the vegetable oils there are a number of oils occupying an intermediate position between the drying and the non¬ drying oils, viz. the semi-drying oils, we find among the marine animal oils gradations from the most pronounced type of easily oxidisable oils—the liver oils—to oils containing large quantities of glycerides of saturated fatty acids, thus approaching the chemical constitution of terrestrial animal oils. 1 Mjoen, Archiv. d. Pharmade, 1894 (234), 278. XI MARINE ANIMAL OILS 469 (1) Marine Animal Oils The oils belonging to this class are liquid at the ordinary tempera¬ ture, yielding, however, on cooling, varying amounts of solid glycerides. The classification of these oils is difficult, owing to our imperfect knowledge of them. The uncertainty of the colour reactions (p. 315) excludes them as a basis of subdivision. The members of this class may conveniently be subdivided into the following three groups :— a. Fish oils. [3. Liver oils. y. Blubber oils. The term “ train oil ” has been avoided, as its German equivalent “Thrane” includes all three groups, and may therefore cause con¬ fusion. It must further be premised that, under blubber oils, those oils only are included that consist wholly or in greater part of glycerides. Therefore the liquid waxes—viz. sperm oil and Arctic sperm oil, although usually classed with blubber oils—are excluded from this group, as, according to their chemical constitution, they belong to the waxes proper. The specific gravities of the marine animal oils do not vary much, lying, as they do, between 0‘915 and 0’930. The saponification values of some of the blubber oils are notable for their great devia¬ tions from the normal value of about 195, according as they contain large amounts of spermaceti or of glycerides of volatile fatty acids; so that this constant, like the specific gravity, cannot be used for purposes of classification. The liver oils, however, appear to form a natural group, character¬ ised by notable amounts of cholesterol and other biliary substances. If, for the purposes of subdivision, we adopt the iodine value as basis, the liver oils may be interposed between the fish oils and the blubber oils. The chemical constitution of the liquid fatty acids is as yet unknown (cp. p. 279). The high iodine values, especially those of the fish and liver oils, clearly point to the presence of acids belonging to a less saturated series than oleic acid. These hypothetical acids, however, cannot be identical with linolic acid or the linolenic acids, as the oils, although absorbing large amounts of oxygen (p. 287), do not dry like linseed oil. 1 The occurrence of acids belonging to the series C n H m _ 2 0 2 , G n H 2n _ 6 0 2 , and CJH m _ 8 0 2 , has been made prob¬ able, although it is not proved yet, and therefore the existence of asellic (p. 54), jecoleic (p. 59), jecoric (p. 62), and therapic acids (p. 63) is open to doubt. All the marine animal oils are easily recognised by their fishy taste and smell. 1 The free fatty acids from seal and cod liver oil kept in .stoppered glass bottles deposited after three months a resinous substance, which I intend to examine. 470 GLYCERIDES—MARINE ANIMAL OILS CHAP. a. Fish Oils The fish oils are obtained from all parts of the body of common fish—such as herring, sardine, salmon, etc.—by boiling. The livers of these fish contain, as a rule, very little oil, whereas the body of the liver oil-yielding fish, notably cod fish, gives so little oil, that it is not prepared commercially. MENHADEN OIL French —Huile de Menhaden. German— Menhadenthran. For table of constants see p. 471. Menhaden oil is an American fish oil, and, like other fish oils, is prepared from the heads and intestines of fish, especially of the menhaden, Alosa Menhaden. The oil is of brownish colour, has a fishy odour, and absorbs oxygen readily. Its composition is not known, but it may be considered to consist almost entirely of glycerides, as shown by the saponification value, its proportion of glycerol, and the small amount of “ unsaponifiable matter.” Unsaponifiable Matter Colour of the Oil. Per cent. Observer. Pale yellow 0-61 Falirion Red .... 0-82 Yellowish-red (Levantine) 1-43 Thomson and Ballantyne Brown .... 1-60 Jean states that menhaden oil usually contains CP02 per cent of iodine. Menhaden oil is frequently adulterated with mineral oil. Its principal use is in the currying trade, and for the manufacture of sod oil. The oil is employed for adulterating linseed oil. [Table Physical and Chemical Constants of Menhaden Oil 472 GLYCERIDES—MARINE ANIMAL OILS CHAP. SARDINE OIL French —Iluile de Sardine. German— Sardinenthran. For tables of constants see p. 473. This oil is obtained in the preparation of tinned sardines. The Japanese sardine oil—Japan fish oil—prepared on a large scale in Japan, is extracted from the fish either by boiling with water or by allowing them to rot in heaps, when the greater part of the oil flows out, the remainder being obtained by pressure. This oil con¬ tains about 30 per cent of solid fat. 1 It is refined in Yokohama by heating to 50°-60° C. for an hour, and then run off into wooden vessels, where it soon separates into three layers. The upper layer is liquid and clear, the middle layer consists of solid fat, 1 and the lowest is water with albuminous substances and portions of the fish. 2 Some constants of this oil, which seems to differ from ordinary sardine oil, especially in its iodine absorption, have been recorded in the table given page 473. Falirion 3 has recently examined samples of sardine oil and Japan oil with a view to determining their ultimate constitution. Besides the values given in the table, we reproduce the following ] This solid fat, brought into commerce under the name “refined fish tallow,” is chiefly used as a degras substitute for currying leather. Jour. Soc. Ckem. Ind. 1894, 894. 2 Villon, Jour. Soc. Chem. Ind. 1887, 372. 3 Ibid. 1893, 938 ; 935. [Table Physical and Chemical Constants of Sardine Oil 474 GLYCERIDES—MARINE ANIMAL OILS CHAP. Sardine Oil. Japanese Oil. Acid value .... Unsaponifiable Hydroxy acids Solid hydroxy acids 20-6 0’62-0'66 percent OJ ,, ,, 0-2 ,, ,, 31-2 0'56-l'44 per cent 0'5 „ „ The solid fatty acids of sardine oil were at first stated by Fahrion to consist of palmitic acid only ; afterwards he modified this state¬ ment by allowing a small quantity of stearic acid, palmitic, however, preponderating. The liquid fatty acids do not contain physetoleic acid (p. 53), nor could any oleic, linolic, or either of the two linolenic acids be detected. The unsaturated fatty acid is said to be jecoric acid, C 18 H 30 O 2 (from jecur, liver • though sardine oil is not a liver oil), an acid isomeric with linolenic acid, but differing from it essentially in that it does not conform to Hazara’s rule (p. 67), according to which it should yield, on oxidation with permanganate in alkaline solution, a hexahydroxy acid, whereas it is apparently broken up with formation of carbonic and volatile fatty acids. Fahrion, there¬ fore, considers this sample of sardine oil to consist of Tripalmitin, 14’3 per cent. Trijecorin, 85'7 „ „ The examination of the other Japanese oil mentioned by Fahrion gave an entirely different result, inasmuch as he could not detect any jecoric acid in it. [The low iodine value of this Japanese oil seems to confirm this.] He has, however, shown in an indirect way the occurrence of an unsaturated acid having seventeen carbon atoms in the molecule and belonging to the oleic series. This acid has been named asellic acid (p. 54). In the present state of this difficult research no definite conclu¬ sions can be drawn, the less so as the various specimens seem to behave differently. The whole question must therefore be considered an open one, especially so as Fahrion's results have been severely criticised by Weiss J Japan fish oil has frequently been referred to by some chemists as a liver oil. /?. Liver Oils The liver oils contain notable amounts of cholesterol and other unsaponifiable substances, giving rise to colour reactions (especially when the oils become rancid) which were formerly considered as characteristic. Only the sulphuric acid colour test can be looked upon as really decisive ; in the case of pure and fresh liver oils the 1 Jour. Soc. Ohem. Ind. 1893, 937. . XI COD LIVER OIL 475 blue colour in the carbon bisulphide solution is very distinct ; if the oils have become rancid a purple colouration takes the place of the blue. The examination of other liver oils than cod by Tichomirow and Kaiser 1 confirms this colour reaction to be a general one of the liver oils. The intensity of the phospho-molybdic acid test is also remarkable. If the chloroformic solution of a liver oil, after shaking with the phospho-molybdic acid, be allowed to stand, there is formed a blue ring at the zone of contact of the two layers, no doubt due to the neutralising action of the bases in the oil. In this form the phospho- molybdic test may serve to identify a liver oil. Rancid liver oils, however, do not give a very distinct colour reaction. The existence of jecoleic and therapic acids has been referred to already. COD LIVER OIL French— Huile de foie de morue. German— Dorschleberthran, Leberthran. For tables of constants see pp. 477, 478. Genuine cod liver oil is obtained from the liver of the cod, Gadus morrhua (and the dorsch, the young of G. morrhua, formerly con¬ sidered as a separate species, Gadus Callarias). The following three qualities of cod liver oil, as obtained by the natural decay of the livers (in the Lofoten islands), are known in commerce : (1) pale cod liver oil, (2) light brown oil, (3) brown oil. Pale cod liver oil 2 and light brown oil are used in pharmacy. The former is the first product, the light brown oil forming a second product, after the putrefaction of the livers has proceeded further. At present large quantities of medicinal oil are prepared by heating the livers by means of steam, when the cell membranes burst and the oil exudes—“steam liver oil.” The medicinal cod liver oil prepared in this country is exclusively obtained by the steam process. The livers must be absolutely fresh; they are taken from fish brought ashore alive and steamed the same day. The brown oil —the “ cod oil ” of commerce—is also a genuine cod liver oil. As the fish cannot be brought alive to shore, they are opened in the boat and the livers collected. These are landed in a more or less putrid state, and the oil is therefore unfit for medicinal purposes. It is largely employed in the leather industry. The “unracked” cod oil is recovered by boiling the livers at a high tem¬ perature ; this oil contains considerable quantities of “ stearine,” which is collected, especially in winter, and sold as “ fish stearine ” for soap-making or “fish tallow” for currying. “Norwegian cod oil ” and “ Newfoundland cod oil ” are special brands of cod oil. 1 Chern. Zeit. 1895, Rep. 310. - The pale yellow colour is due, according to P. Moller, to a pigment (lipochrome) which is destroyed by the action of bright light—artificially bleached oils. 476 GLYCERIDES—MARINE ANIMAL OILS CHAP. P. Moller 1 discerns four qualities: (1) raw medicinal oil; (2) pale oil; (3) light brown oil; (4) brown oil. As a rule, however, so little is obtained of oil (1) that it is not collected separately. Therefore the writer retains the subdivision into three qualities. 2 The commercial “ Coast cod oil ” is a liver oil obtained from other fish besides cod, as hake ( Merluccius vulgaris), haddock ( Merluccius xglefinus), ling (Molva vulgaris), coal fish ( Gadus virens), in fact any fish that is caught in the nets of the trawlers on the open sea. The livers from these fish are collected in barrels, and reach the works of the cod oil extractor in a very putrid state. According to the temperature reached in the manufacture, cod liver oil contains larger or smaller quantities of “ stearine ” which is allowed to settle out. Therefore the solidifying point of different samples will be found to vary greatly. 1 Godliver Oil and Chemistry , London, 1895. 2 Complete details as to the manufacture of cod liver oil in Norway are given in P. Mdller’s book, Godliver Oil and Chemistry . [Table Physical and Chemical Constants of Cod Liver Oil Physical and Chemical Constants of the Mixed Fatty Acids GLYCERIDES—MARINE ANIMAL OILS >■> ^ Ph f-* cc P Iffi IS P Eh O S CO ce o £ t-3 co os co os co ^ CO O 00 CO (N r d nd ce ^ • §■§> 'g "m ^ p' o §0^2 OlZiP CHAP. XI COD LIVER OIL 479 The chemical composition of the glycerides in cod liver oil appears to be very complicated. As palmitic and stearic acids have been isolated, the occurrence of palmitin and stearin is certain. But the “ stearine ” separating from cod liver oil on cooling contains but little true “ stearine,” i.e. glycerides of stearic and palmitic acids, the cod liver oil stearine having a very high iodine value (113*4, Heyerdahl; 94, Lewko- witsch ). The nature of the liquid fatty acids is but imperfectly under¬ stood as yet; the high iodine value points to the presence of large pro¬ portions of less saturated acids than those belonging to the oleic series. Small quantities of glycerides of the lower fatty acids have been stated by various authors to occur in cod liver oil, such as glycerides of acetic, butyric, valeric, and capric acids. Thus Allen has found for a sample of oil a Reichert value of IT to 2*1. According to Salkowski and Steenbuch, however, the volatile fatty acids found are but secondary products due to putrefaction of livers, which in the older processes of manufacture always occurred to a greater or less extent. The best medicinal liver oils prepared by steam are, indeed, free from volatile acids. Fahrion , l examining the liquid fatty acids from a cod liver oil absorbing 175 - 5 per cent of iodine, could not identify amongst them jecoric acid with certainty, and assumes the presence of an acid, Ci 7 H 32 0 2 , named asellic acid. Physetoleic acid (iodine value = 100), however, said to form the chief constituent of cod liver oil, could not be detected by this investigator. The latest researches of Heyerdahl 2 led this chemist to the conclusion that the mixed fatty acids from cod liver oil, freed from its “stearine,” contained amongst other acids, not identified hitherto, about 4 per cent of palmitic acid, 20 per cent of jecoleic acid (p. 59), and 20 per cent of therapic acid (p. 63). The presence of jecoleic acid is inferred from the existence of dihydroxy jecoleic acid prepared by oxidation of the mixed fatty acids by means of potassium permanganate, and that of therapic acid from the octobromide C l7 H 26 Br 8 0 2 obtained on brominating the liquid fatty acids. No oleic acid has been found in cod liver oil, and the “stearine,” no doubt, contains some unknown unsaturated acid or acids. In the fresh state cod liver oil contains no hydroxy acids, according to Heyer¬ dahl. The peculiar composition of some of the fatty acids satisfactorily explains the extraordinary facility with which cod liver oil is oxidised and turns rancid. Heyerdahl’s opinion, however, that rancidity is due to the formation of hydroxy acids requires confirmation. A characteristic constituent of cod liver oil is cholesterol, which can be isolated by saponifying the oil and exhausting the soap with ether. The residue obtained on evaporating the ether is then crystallised from alcohol when the characteristic cholesterol crystals are deposited. The quantity of cholesterol, according to Allen and Thomson, is from 046 to 1*32 per cent; Salkowski 3 gives as an average 03 per cent. Jean 4 obtained 6 per cent of unsaponifiable 1 Jour. Soc. Chern. Ind. 1893, 935. 2 Codliver Oil and Chemistry, p. lxxxix. 3 Zeitsch. f. analyt. Chemie, 26. 565. 4 Moniteur scientif. 1885, 892. 480 GLYCERIDES—MARINE ANIMAL OILS CHAP. matter from a sample, which must, in the opinion of the writer, be due to sophistication with shark liver oil. The figures recorded in the following table undoubtedly prove that 6 per cent is an excep¬ tionally high figure :— XI COD LIVER OIL 481 Raw medicinal oil, i.e. the first oil exuding spontaneously from the livers, contains but very small quantities of ptomaines ( Heyerdahl). In light brown cod liver oil, however, organic bases to the extent of from 0 - 035 to 0-050 per cent have been shown to occur by Gautier and Morgues. 1 The following bases have been isolated :— Bases in Cod Liver Oil Volatile. Non-volatile. Butylamine Morrhnine, G ]9 II 27 X :J Isoamylamine Aselline, C 25 H :J2 N 4 Hexylamine Dihydrolutidine Besides these bases an acid containing nitrogen has been found. This acid, morrhuic acid, C 9 H 13 N0 3 (differing from tyrosine by H., only) is probably identical with De Jongh’s gaduine. Heyerdahl has isolated trimethylamine by means of its platino- chloride. This base, however, must, like those mentioned above, be considered as a product of decomposition of the cellular tissue of the livers. Biliary colouring matters, as stated by earlier observers, are absent. According to Salkowski the colouring principle in cod liver oil belongs to the class of lipochromes. As products of decomposition must also be considered small quantities of albuminoid substances occurring in cod liver oil. According to Unger , 2 there are combined with these latter minute quantities of iron, manganese, and phosphoric acid (a substance similar to lecithin, yielding phosphoric acid, glycerol, and the above-mentioned morrhuic acid, has been obtained by Gautier and Morgues). Also calcium, magnesium, and sodium have been found, and the metalloids chlorine, bromine, and iodine. The following amounts of iodine have been obtained by several chemists :—• Proportion of Iodine in Cod Liver Oil Description of Oil. Iodine. Observer. Pale Yellow . Per cent. 0-020 0-031 0-00138-0-00434 0-0002 Andres J } Stanford Heyerdahl Formerly the therapeutic value of cod liver oil was supposed to be due to the small amount of iodine it contained (therefore cod liver oils are met with to which iodine or potassium iodide has been added fraudulently), or to any of the many “ active principles ” stated to 1 Compt. rend. 107, 254 ; 626 ; 740. 2 Pharniac. Gentr. Halle, 1889, 261. 482 GLYCERIDES—MARINE ANIMAL OILS CHAP. occur by various writers. Thus, according to Marpmann, 1 it is due to a substance which may be precipitated by ether and alcohol, and is said to cause the cod liver oil to be completely emulsified on coming in contact with the gastric juice. The medicinal effect of cod liver oil, however, has rather to be looked for in the facility with which it is split up, or, as others will have it, digested, and it cannot be doubted that this property is caused by the peculiar constitution of the unsaturated fatty acids (therapic and jecoleic acids). According to Heyerdahl , that cod liver oil should be the best from' the medicinal point of view which has been protected from oxidation. Cod liver oil, becoming so easily rancid, contains varying amounts of free fatty acids. In fact, Hosmann states that cod liver oil is the only animal oil which is characterised by the presence of free acids even when freshly rendered. On testing a number of oils Kremel found the amounts of caustic potash required to saturate the free acids in 1000 grms. of each oil to vary from 062 grm. to 28’67 grms. The former number calculated to oleic acid corresponds to 0'312 per cent. Heyerdahl has studied the influence that the length of time the livers are heated has on the proportion of free fatty acids in the oil produced. He found that, contrary to expectation, the percentage of free fatty acids decreased slightly but perceptibly as the time of heating was increased (from 20 to 80 minutes) and the temperature raised (from 62° to 85° C.). This result might be due to the vola¬ tilisation of free volatile acids at the higher temperature, or to the first portions of the extracted oil being richer in fatty acids, or to both causes together. Experiments, in which measured volumes of air were driven through samples of oil heated in the water-bath, proved that the free fatty acids decreased up to a certain point, and then slowly rose to or beyond the original percentage. The propor¬ tions of free fatty acids never exceeded 0 - 69 per cent calculated as oleic acid. The oil obtained by passing steam directly into the livers is, according to the same chemist, practically devoid of volatile fatty acids, and their occurrence must therefore be due to some secondary process. This statement has been corroborated by the examination of liver oils from other species of fish ( Heyerdahl). How far the oil may thus be affected is shown in the following table :— 1 Chem. Centr. Blatt. 19. 1213. [Table XI COD LIVER OIL 483 Free Fatty Acids in Gocl Liver Oils , calculated as Oleic Acid Description of Oil. Colour. Acid Value. Free Fatty Acids. Observer. Raw medicinal oil . Pale 7-38 Per cent. 379 Heyerdahl Somewhat 7-55 3-87 darker Darkest 7-72 3-96 Pale oil \ obtained from Pale 21-20 10-9 Brown ,, j livers by decay Brown 54-4 28-0 Thomson and Medicinal oil . Yellow 0-36 Scotch cod oil Brown 9-73 Ballantyne y y Newfoundland cod oil Red-brown 23-31 Parry and Sage Medicinal oils 0-34-0-60 Examination of Cod Liver Oil Cod liver oil is liable to be adulterated with not only the liver oils of other fish than those belonging to the “ Gadus ” family, but also with fish oils (such as Japan fish oil), and blubber oils (refined seal oil), the detection of which, in the present state of our knowledge, is extremely difficult. Colour alone is not the decisive characteristic, as oils are bleached artificially. In Holler's opinion, such oils are worse than brown oils. We are indebted to Kremel 1 for an ex¬ haustive examination of this subject. His results are given in the following table, the inspection of which will show that the specific gravity affords us little help in identifying any of the oils mentioned when in admixture with cod liver oil:— 1 Pharmac. Centr. Halle , 1884, 337. [Table This is the Danish “Sejthran.” 2 This is most likely Japan fish oil. XI COD LIVER OIL 485 The amount of solid fatty acids in the liver oil from Merlangus is about twice as great as in cod liver oil. This, however, may be due to the “ stearine ” not having been allowed to settle out thoroughly. The solid fatty acids of seal oil have a somewhat higher melting point than those of the other oils. Allen 1 also has pointed out that the specific gravity affords no reliable indication of the presence of fish oils in cod liver oil, as will be seen from the following table : 2 — Specific Gravity of various Liver, Fish, and Blubber Oils (Allen) Oil. Specific Gravity at 15’5° C. Cod liver oil 0-929 Hake liver oil 0-927 Skate liver oil 0-9327 Shark liver oil 0-9285 Mixed liver oils from cod, haddock, ling, whiting (prepared in Grimsby) 0-930 Haddock liver oil, Aberdeen 0-931 Ray liver oil 0-928 Herring oil 0-9326 Sprat oil 0-9284 Seal oil 0-9245 Whale oil . 0-9301 According to Kremel the following colour reaction with fuming nitric acid is said to give reliable results. Place 10 to 15 drops of the sample on a watch-glass, and allow 3 to 5 drops of nitric acid, specific gravity 1 *5, to flow in slowly from the side, when the following colourations will be observed :— Oil. Genuine cod liver oil Oil from Merlangus Japan fish oil Seal oil . Colour Reaction with Fuming Nitric Acid, Spec. Gray. 1-5. Red at the place of contact; on stirring, fiery rose, changing quickly to lemon-yellow. Intense blue at the place of contact ; on stirring, brown, and remaining so for two to three hours, and then changing to yellow. Like the preceding, sometimes there appear red streaks as well as blue. No change at first; turns brown after some time. Kremel considers the reactions described so characteristic that 25 per cent of the three other oils may be detected with certainty in cod liver oil. Meyer uses as reagent a mixture consisting of equal parts of concentrated sulphuric and nitric acids, with which he mixes 10 volumes of the sample. If the oil is genuine a fiery rose colour is obtained, which changes quickly to lemon-yellow. Other oils either do not give the change in such a distinct manner or cause a brownish- violet colouration. 1 Commercial Organic Analysis, ii. 163. 2 Cp. also table p. 489. 486 GLYCERIDES—MARINE ANIMAL OILS CHAP. Eoessler states that seal oil in cod liver oil can be detected by shaking the sample with aqua regia; genuine oil gives a greenish, dark yellow liniment, turning brown after half an hour, and remaining so; whereas in the case of pure pale seal oil, or of a mixture thereof with cod liver oil, a pale yellow colour is produced. The experiments which the writer has made with pure samples prove that these colour reactions are valueless. 1 Other qualitative reactions are the following: — The Hager - Salkowski cholesterol test (p. 84) gives with pure cod liver oil at first a violet-blue, then purple, then brownish-red colour, changing at last into a deep brown. According to Salkowski there participates in these colourations not only the cholesterol, but also a lipochrome and the cod liver oil acids. For if the unsaponifiable matter isolated from cod liver oil be dissolved at once in chloroform, without sepa¬ rating the cholesterol by crystallisation from alcohol, a clear, golden- yellow solution is obtained, giving a beautiful indigo-blue colour with sulphuric acid in the first instance, and afterwards the cholesterol reaction. The blue colour is due to a lipochrome. The German Pharmacopoeia prescribes as follows :—Dissolve one drop of oil in twenty drops of carbon bisulphide, and add one drop of concentrated sulphuric acid, when a beautiful violet-blue colour appears at once, changing afterwards into red and brown.—This test cannot serve as an identity reaction, as other liver oils, e.g. Arctic shark liver oil, gives the same violet-blue colour. Cod liver oil, as also other liver oils which have become rancid, do not show the violet-blue, but give at once the red colour (which is also shown by palm oil, see below). Medicinal cod liver oils when poured carefully on nitric acid, of specific gravity 1*4, so as to form two separate layers, should, according to linger , give a white ring, indicating albumen. This ring should appear, at latest, after five hours’ standing. The writer could not obtain this reaction. Of the quantitative reactions the acid value, the iodine value, the Reichert value, and the proportion of unsaponifiable matter, will give useful indications as to the quality and purity of the oil. Steam cod liver oil contains, according to Kremel , Salkowski , and Heyerdahl , only from 03 to 1*5 per cent, medicinal oil, prepared by older processes, from 3 - 3 to 6 per cent of free fatty acids. The free fatty acids may be determined by Hofmann’s method:— 0'5 to 7 grms. of oil (according to the proportion of free acids present) are dissolved in 20-40 c.c. of neutralised ether, and titrated with caustic potash, using an alcoholic solution of rosolic acid (1 : 1000) as an indicator, phenolphthalein giving unsatisfactory results ( Heyerdahl). Free volatile acids should not occur in a medicinal oil, as their presence would indicate that putrefied livers had been used in the preparation of the oil. These acids are detected by shaking the oil with water and examining the latter for acidity. 1 Cp. also Jorissen, Jour. Soc. Chem. Ind. 1896, 460. XI COD LIVER OIL 487 The higher the iodine value the better the oil; oil exposed to the atmosphere, or oil obtained from livers by the process of decay will show low numbers (cp. table p. 477). The determination of the Reichert value would also indicate presence of volatile acids. No good oil should have a higher Reichert value than 0'20 ( Salkowski ). The amount of unsaponifiable matter would possibly point to adulteration with (besides mineral oil) shark liver oil, this latter oil containing notable proportions of spermaceti, and consequently of ether soluble residue. Several samples of shark liver oil gave the following numbers :— Shark Liver Oil. Unsaponifiahle. Observer. Yellow, steamed . Per cent. 5-27 Fahrion Red 4-44 , , Yellow . 1-24 Yellowisli-red 0-93 Allen Japanese 2-82 Crude . 8-70 ,, Refined . 070 , , Pale yellow, from\ 10-25 17-30 10-34 10-20 Lewkowitsch Scymnus borealisJ The amount of iodine in iodised cod liver oils is ascertained, according to Stanford , x by saponifying 300 grms. of oil with 60 grms. of caustic soda (free from iodine), evaporating to dryness and burning the soap in a porcelain crucible. The charred mass is boiled out with water, filtered, and the filtrate evaporated to 300 c.c. 30 c.c. of this solution are then shaken with 12 c.c. of carbon bisulphide after a few drops of nitrosulphuric acid have been added (prepared by passing nitrous acid, evolved on heating starch or arsenious acid with nitric acid, into sulphuric acid). The amount of iodine dissolved in the carbon bisulphide is then estimated colorimetrically by com¬ paring its depth of tint with that of another solution prepared similarly from a known amount of potassium iodide. Andres 2 burns off 3 grms. of cod liver oil, previously mixed with 2 grms. of sodium carbonate in a porcelain crucible, then exhausts the mass with boiling water, and evaporates down to a few c.c. The solution is mixed with five to six drops of fuming nitric acid, agitated with carbon bisulphide, and the iodine dissolved in the latter titrated with a standardised solution of sodium thiosulphate. 3 On shaking pure cod liver oil with water or alcohol no iodine passes into solution; fraudulently added potassium iodide can there¬ fore be detected by this means. 1 Pharm. Jour. (3) 14. 353. 2 Chem. Zeit. 1889, Rep. 106, 3 Cp. also Gorges, Jour. Pharm. Ghim. 1896 [16], 2. 488 GLYCERIDES—MARINE ANIMAL OILS CHAP. Besides the oils already mentioned, the following are used for- adulterating cod liver oil: Mineral oil, resin oils, and vegetable oils. Mineral and resin oils may be detected by determining the amount of unsaponifiable matter and examining the latter. Non-drying and semi-drying oils lower the iodine absorption and temperature in Maumend’s test. Drying oils , as poppy seed and linseed oils, may be recognised by spreading the sample in a thin layer on a glass plate. Cod liver oil becomes oxidised, but does not yield a solid skin like a typical drying oil, but, at most, becomes resinous. The Livache test would not be applicable in this case (cp. p. 287). If the amount of seed oil present in a cod liver oil reaches 20 per cent the adulteration can be detected, according to SalkowsJci, by the phytosterol test (p. 317), the crystals obtained from the un¬ saponifiable matter melting, in the case of pure cod liver oil, at 146° C., and in the case of adulterated oil at from 139°-140° C. In the presence of rape or cotton seed oil the crystals of phytosterol may be recognised under the microscope ; they are not so distinctly discerned in the case of linseed oil. For the detection of cod liver oil in other oils Salkowslci examines the liberated fatty acids. Cod liver oil fatty acids, dissolved in sufficient chloroform to yield a 5-8 per cent solution, assume on mixing with an equal volume of concentrated sulphuric acid a deep reddish-brown colour appearing dirty green in reflected light. If the mixture be allowed to settle half an hour and the colourless chloroform be poured off, the addition of a few drops of a mixture of sulphuric acid in a few c.c. of glacial acetic acid gives, after one to two hours’ standing, a very beautiful reddish-violet colour, showing a dirty green reflection, 1 which remains for a few days. No seed oil shows this reaction with the mixture of sulphuric and acetic acids, oleic acid and the fatty acids from palm and linseed oils only giving a very faint indication. A better and more characteristic test is the sulphuric acid test already described (only palm oil, and in very minute quantity, also cotton seed oil, contain a colouring substance producing a blue coloura¬ tion with the mixture of chloroform and sulphuric acid). Other liver oils are commercially of minor importance, and there¬ fore need not be considered here individually. Some of these oils and their characteristics, as specific gravity, iodine values, etc., have been already referred to under cod liver oil. Shark liver oil appears to be no longer used in this country; at any rate it is not prepared here commercially. This oil is prepared in considerable quantities in Iceland, and exported to the Continent for use in tanning. The livers from any shark caught by the trawlers will no doubt be mixed with other livers, and therefore the “Coast Cod Oil” (p. 476) may 1 Isocholesterol reaction ? XI COD LIVER OIL 489 contain varying quantities of shark liver oil. From the table given p. 487, it is apparent that shark liver oil contains a larger amount of unsaponifiable matter than cod liver oil. I add here a few constants of several liver oils ; the first three oils are undoubtedly genuine. 1 1 I am indebted for these oils to the kindness of Mr. W. Corder, South Shields. 490 GLYCERIDES—MARINE ANIMAL OILS CHAP. y. Blubber Oils This group comprises oils of varying composition. Seal oil consists almost wholly of glycerides; whale oil and dolphin oil contain notable amounts of spermaceti, forming, as it were, inter¬ mediate members between true oils and liquid waxes. We describe here the following oils : Seal oil, whale oil, dolphin (black fish) oil, porpoise oil. The last two members of this group occupy an exceptional position on account of their containing considerable proportions of glycerides of volatile acids. SEAL OIL French —lliiile de pJioque. German— Robbenthran. For tables of constants see pp. 491, 492. Seal oil is the oil obtained from the blubber of the various species of the seal, as Phoca vitulina, Phoca grcenlandica, Phoca lagura, Phoca caspica, etc. The colour of seal oil varies with its quality; it is either white, or yellow, or brown. In commerce we find four brands of seal oil, and besides these, mixtures of seal oils with various fish oils are sold as seal oil ( e.g . the Swedish “ Three Crown ” oil). The fatty acids of two specimens of seal oil examined by Kremel consisted of— No. Liquid Fatty Acids, i Solid Fatty Acids. Per cent. Per cent. 1 85-02 10-23 2 89-25 9-81 1 Kurbatoff has found linolic acid among the liquid fatty acids of the Caspian seal, cp. p. 318. [Table Physical and Chemical Constants of Seal Oil. Calculated from bromine value. 2 Bromine values 69'6-80, corresponding to iodine values 110'5-126'7. Cp. p. 308, footnote. 492 GLYCERIDES—MARINE ANIMAL OILS CHAP. Physical and Chemical Constants of the Mixed Fatty A cids Solidifying Point. Melting Point. Saponific. Value. °C. Observer. °C. Observer. Mgrms. KOH. Observer. Titer 15-5-15-9 Test. Lewko- witsch 22-33 Chapman and Rolfe 190-4-196 Chapman and Rolfe The following table contains the proportions of free fatty acids and unsaponifiable matter found by several observers :— No. Kind of Seal Oil. Free Fatty Acids (as Oleic Acid). Unsaponifiable Matter. Observer. 1 Per cent. 1-95 Per cent. Deering 2 2-01 3 Cold-drawn, pale . 1-80 0-5 Thomson and Ballan- 4 Steamed, pale 1-46 0-38 tyne 1 5 Tinged (brown) . 8-29 0-42 6 Norwegian . 7-33 0-51 7 Swedish “Three Crowns” 1-4 Fahrion 2 8 Very pale . 0-98-1-13 Chapman and Rolfe 3 9 Yellow 1-41 10 Light brown 4-09 11 Dark brown 19-95 ” Adulteration with resin oil can be easily detected by determining the proportion of unsaponifiable matter. WHALE OIL French— Haile de baleine. German— Walfischthran. For tables of constants see pp. 493, 494. Whale oil is the oil extracted from the blubber of various species of the genus Balsena, as Balrena mysticetus, Greenland or “ Right ” whale (Northern whale oil), Balsena australis (Southern whale oil), Balsenoptera longimana, Balsenoptera borealis (Fin-back oil, Humpback oil). The northern whale oil is the “ train oil ” proper ; but this name has become a generic name, and has been extended to all other “ blubber oils ” included in this class. 1 Jour. Soc. Chem. Ind. 1891, 286. 3 Ibid. 1894, 843. 2 Ibid. 1893, 607. Physical and Chemical Constants of Whale Oil 494 GLYCERIDES—MARINE ANIMAL OILS CHAP. Physical and Chemical Constants of the Mixed Fatty Acids Specific Gravity. Solidifying Point. Melting Point. Iodine Value. At 100° C. (Water 100° C. = i.) Observer. °C. Observer. °C. Observer. Per cent. Observer. 0-8922 Arch butt Titer 22-9-23-9 Test. Lewko- witsch 27 14-151 16 ( 16-2 ( 18 ) Jean Schweitzer and Lungwitz 130-3-132 Schweitzer and Lungwitz Whale oil has a yellowish-brown or dark brown colour, and an offensive “ fishy ” smell. Refined oil, freed from the “ stearine ” by cooling, possesses a light colour. The physical and chemical pro¬ perties vary considerably according to the kind of animal from which the oil has been obtained. The constitution of whale oil is not known. Fahrion isolated from one sample palmitic acid. Allen , again, found in some whale oils glycerides of volatile fatty acids, whereas other specimens (see table) are practically devoid of them. The “ stearine ” deposited on cooling consists of palmitin, and most likely of a small quantity of spermaceti. The amounts of unsaponi- fiable matter found in whale oils (see following table) point to the presence of the latter. Description of Oil. Per cent. Observer. Norwegian, yellowisli-red . 0-65 Fahrion ,, yellowish-brown 1-26 ,, brown Pale ..... 1-37 J > Thomson and Ballantyne 1-22 ,, refined 0-92-372 Lewkowitscli Whale oil is used as a burning oil and for leather-dressing; the pale or water-white brands are employed in soap-making. It is largely adulterated with seal oil and resin oil. XX DOLPHIN OIL 495 DOLPHIN OIL (BLACK FISH OIL) French— Huile de dauphin. German— Delphinthran. For table of constants see p. 496. Dolphin oil, from the blubber of the black fish (bottlenose dolphin) Delphinus globiceps, forms an intermediate link between whale oil (consisting nearly wholly of glycerides with but a small quantity of spermaceti), and sperm oil (which must be considered, from its chemical composition, a true wax). This oil is of a pale yellow colour. On standing it deposits sper¬ maceti (cetyl palmitate, p. 15) [Chevreul]. It is remarkable for the large amount of glycerides of volatile fatty acids it contains, a characteristic which it shares with porpoise oil. Larger still is the proportion of glycerides of volatile acids in the jaw oil, the liquid oil from the soft blubber contained in the head and jaw of the black fish. This jaw oil has a straw-yellow colour; it is limpid, transparent, and has a not unpleasant smell. It is used for lubricating fine machinery. [Table XI PORPOISE OIL 497 PORPOISE OIL French— Huile de Marsouin. German— Meerschweinthran. For table of constants see p. 498. Porpoise oil is obtained by boiling with water the whole tissue of the black porpoise, Delphinus phocsena. This oil has been examined first by Chevreul, who discovered in it valeric acid, named by him “ acide phocenique.” The oil is pale yellow or brown, and consists of the glycerides of valeric, palmitic, stearic, and oleic (and physetoleic ?) acids. The porpoise also yields a jaw oil which appears to be very similar to the jaw oil of the black fish. The two “ body ” oils also resemble one another. . Since, however, porpoise oil does not deposit spermaceti, we have described the two oils separately, following Chevreul’s example. The jaw oil is easily soluble in alcohol at 70° C., and taking advantage of this it is possible to extract it from a mixture of the body and jaw oils. 2 K [Table 1 Reichert-Meissl values 46 9 and 131'6 halved for the sake of comparison. 2 Jour. Soc. Ghem. hid. 1890, 331. 3 Zeit. angew. Cliem. 1889, 64. XI SHEEP’S FOOT OIL 499 (2) Terrestrial Animal Oils Under this heading we shall describe the oils obtained from the feet of oxen, sheep, and horses, and from eggs. Liquid fats are also obtained from lard and tallow by pressing. These oils are characterised by a low iodine value, lower than that of the non-drying oils, and a low thermal reaction. They yield solid elaidins with nitrous acid. sheep’s foot oil French —Huile de pieds de mouton. German— Hammelklauenoel. For tables of constants see p. 500. This oil is obtained from sheep’s trotters in the manner described for neat’s foot oil (see p. 504). It resembles very much neat’s foot oil, and is, as a rule, mixed with it. [Table Specimen prepared in the laboratory. 2 Sheep’s foot oil is the standard oil for Jean’s oleo-refractometer. XI HORSES’ FOOT OIL 501 horses’ foot oil French —ILuile de pieds de cheval. German— Pferdefussoel. For tables of constants see p. 502. This oil, obtained from horses’ feet, is prepared and used like the preceding oil. A sample rendered in my laboratory and filtered contained certain impurities, so that the oil gave a number of colour reactions which have been considered hitherto as characteristic of marine animal oils (cp. p. 279). The oil also gave a high acetyl value. [Table Physical and Chemical Constants of Egg Oil 004 GLYCERIDES—TERRESTRIAL ANIMAL OILS chap. Egg oil is contained in the yellow of the egg (of chicken). It is extracted from the yolk of hard-boiled eggs either by pressure or by solvents. Palaclino and Toso obtained by the former method 25 to 35 per cent, Kitt, using ether as a solvent, 19 per cent only. The ether extracts, besides egg oil, other substances, notably lecithin. The expressed oil was limpid and of a yellow colour. On cooling it deposited crystals of cholesterol. The extracted oil, freed by filtra¬ tion from other ether-soluble substances, was semi-solid and of an orange-yellow colour. The specimen examined by Kitt contained 0‘2 per cent of lecithin, and 1 ‘5 per cent of cholesterol, and had an acid value of only 1-2. Egg oil gives the elaidin reaction. The acetyl value 11 -9 given by Kitt must be accepted with reserve (see p. 164). It is apparently high on account of the cholesterol present. neat’s foot oil French Huile de pieds de boeuf. German— Oclisenldauenoel. For tables of constants see p. 505. Jveats foot oil is the oil obtained from the feet of oxen by boiling in water. It is a pale yellow, odourless oil, of bland taste. The commercial samples, even if unsophisticated, consist mostly of true neat s foot oil mixed with sheep’s foot and horses’ foot oils. On standing the oil deposits “ stearine.” Neat’s foot oil is valued as a lubricating oil, for the reason that it does not turn rancid easily. The high price of the oil acts as an incentive to fraud. It is largely adulterated with fish, poppy seed, rape, cotton seed, and mineral oils. These adulterations can be easily detected by deter¬ mination of the iodine absorption, the proportion of unsaponifiable matter, the thermal reaction, etc. Lard Oil (see p. 584). Tallow Oil (see p. 591). [Table Physical and Chemical Constants of NeaPs Foot Oil 506 GLYCERIDES—VEGETABLE FATS CHAP. II. SOLID FATS 1. Vegetable Fats The members of this group are solid at the ordinary temperature, presenting, however, a variety of gradations from the soft, buttery masses of, say, cotton seed stearine, to the hard, wax-like Japan wax. As the hardness of the fats increases approximately in direct propor¬ tion to the decrease of glycerides of oleic acid (including with it the small quantities of linolic acid, if present), the iodine value seems to indicate the order in which the individual fats should be enumerated in the absence of other chemical characteristics. Palm nut oil and cocoa nut oil, however, have been placed together as undoubtedly con¬ stituting, together with mocaya oil, a well-defined group, distinguished by a considerable amount of glycerides of lower fatty acids, and in that respect resembling to some extent butter fat. The following fats are described : Cotton seed stearine, chaul- moogra oil, carapa oil, laurel oil, mowrah seed oil, shea butter, vegetable tallow, palm oil, macassar oil, sawarri fat, mafura tallow, nutmeg butter, Kambutan tallow, Mkanyi fat, cacao butter, kokum butter, Borneo tallow, dika oil, Mocaya oil, palm nut oil, cocoa nut oil, myrtle wax, ucuhuba fat, Japan wax, Malabar tallow, wild olive fat. COTTON SEED STEARINE French— Margarine de coton, Margarine vdgetale. German— Baumwollenstearin, Vegetabilisches Margarin. For tables of constants see pp. 507, 508. Cotton seed stearine is the solid fat deposited from cotton seed oil. This “stearine” is obtained on a large scale, especially in America, by cooling cotton seed oil (the fluid part constituting the “winter” oil) and pressing the solid deposit. According to the pro¬ cess of manufacture, the “stearine” will contain larger or smaller proportions of liquid glycerides, therefore the numbers given in the table for the melting point vary considerably. A sample examined by Hehner and Mitchell contained 3’3 per cent of stearic acid. Cotton seed stearine is a light yellow fat of buttery consistency. It is used for soap-making, but is chiefly employed in the manufacture of lard and butter substitutes, for which purpose it is specially adapted on account of its neutrality and its physical properties. Under the name of “ cotton seed stearine ” there is in commerce a distilled stearic acid (p. 692) with which the neutral cotton seed stearine must not be confounded. Physical and Chemical Constants of Cotton Seed Stearine XI COTTON SEED STEARINE £-4 o3 Eh GG s O <£> C3 S O 00 r c5 > o M o -4-5 c3 *E *£ Lew- Dwitscli hweitzer and ngvvitz D o < W « 1 *4 o P 'S . , 00 O 00

K 05 co CO CM CM 05 O Oi 05 05 § ?h' > J-i <3 i ^ £ -2 > W ^ £ o rM o ft Sa p 00 T 1 c5 CQ ? o £ c m <4 4jh o _H VO g°$ : s £ f-t o : > J§ ■g £h ci o o s w w „® S vp VO 00 CO w o 05 05 a o wc g mfm4 m libjS : {z; O ^ Q P . CM : CO ^ -2 o rO Cj , fit s sM g =« -ggs 2 ^ MOS o o o o o o o o CO CO 00 CO 508 GLYCERIDES—VEGETABLE FATS CHAP. Physical and Chemical Constants of the Mixed Fatty A cids Solidifying Point. Melting Point. Iodine Value. °C. Observer. °C. Observer. Per cent. Observer. 23-21 1 De Negri and Fabris 27-30 De Negri and Fabris 94-3 De Negri and Fabris Titer Test. 34-9-35-1 Lewkowitsch CHAULMOOGRA OIL French— Beurre de Chaulmougra. German— Chaulmugraoel. Phijsical and Chemical Constants of Chaulmoogra Oil Saponification Value. Iodine Value. Mgrms. KOH. Observer. Per cent. Observer. 204 Lewkowitsch 90-35-90-9,' Lewkowitsch Physical and Chemical Constants of the Mixed Fatty Acids Solidifying Point. Iodine Value. °C. Observer. Per cent. Observer. Titer Test. 39-5-39 "6 | Lewkowitsch 86 Lewkowitsch Chaulmoogra oil is a fat of buttery consistency obtained from the seeds of Gynocardia odorata. Its chemical constitution is unknown. According to Allen 2 this fat contains umbellulic acid. The acid value of a sample examined in my laboratory was 37 - 4. 1 This figure cannot possibly be correct. 2 Thorpe, Dictionary of Applied Chemistry, iii. 43. XI CARAPA OIL—LAUREL OIL 509 CARAPA OIL (CRAB WOOD OIL) French— Beurre (liuile) de Carapa. German— Carapafett. Physical and Chemical Constants of Carapa Oil Solidifying Point. Melting Point. Saponification Value. Iodine Value. °C. Observer. °C. Observer. Mgrms. KOH. Observer. Per cent. Observer. 18 36 Schaedler Hannau 1 23-25 31 Schaedler Hannau 239 Hannau 721 Hannau This fat is expressed from the seed of several species of plants belonging to the genus Carapa , as Carapa guianensis, Carapa moluc- censis. Carapa oil is a product of Brazil, Guiana, West Coast of Africa, India, Moluccas, where it is chiefly used for soap-making, etc.; it is also imported into this country and France for the same purpose. LAUREL OIL French— Beurre de laurier. German— Lorbeeroel. For tables of constants see p. 510. Laurel oil 2 is obtained from the berries of the laurel-tree ( Laurus nobilis, L.) either by pressing, or by boiling the pounded berries with water. It has a green colour, and at the ordinary temperature a buttery consistency; its taste and aromatic odour are peculiar. Laurel oil is completely soluble in boiling alcohol; on cooling, crystals of trilaurin separate. Trilaurin is stated to be the chief con¬ stituent of this oil, but judging from the high iodine value it must contain considerable quantities of olein. Allen has found small quantities of volatile acids (acetic). A sample examined by the writer had the acid value 26'3. Laurel oil is only used in veterinary practice. It is sometimes adulterated with other fats (lard) coloured green with copper salts (detected by incinerating, cp. p. 98). 1 Annali del Laboratorio delle Gabelle, 1891-1892, p. 271. a Laurel oil must not be confounded with the oil from the seeds of Calophyllum inophyllum, described by Hooper {Jour. Chevi. Soc. 1889, Abstr. p. 541) under the name of Lo.urel nut oil. According to Schaedler, this substance is Poonseed oil (German Tacahamacfett). The greenish-yellow colour seems to have been the cause of the mis¬ nomer laurel nut oil. Nor must laurel oil be confounded with Indian laurel oil, described p. 365, from the fruits of Laurus indica. XI MOWRAH SEED OIL 511 MOWRAH SEED OIL 1 (MAHWAH BUTTER) French— Beurre d’lllipd 2 Huile de Mowrali. German— Mahwabutter, Illipeoel 2 Bassiaoel. For tables of constants see p. 512. Mowrali seed oil is obtained from the seeds of Bassia longifolia, but the commercial fat is a mixture of this fat with that prepared from Bassia latifolia . 3 When in the fresh state the fat is yellow; it is bleached on ex¬ posure to the air, becoming white, at the same time turning rancid. The fat has the consistency of lard, possesses a bitter aromatic taste, and a characteristic odour recalling that of cacao beans. It contains considerable quantities of free fatty acids, the crystals of which can be recognised under the microscope. Nordlinger found in a sample 28*54 per cent of free fatty acids ; the sample examined in the writer’s laboratory contained 17*2 per cent. The proportion of glycerol in the sample examined by Valenta was but 3*09 per cent. The fatty acids consist of 63*5 parts of oleic acid and 36*5 solid fatty acids; the chief constituent of the latter is palmitic acid. Mowrali seed oil is an important article of commerce; it is im¬ ported from India into this country and France, and used for candle and soap making. 1 Valenta, Dingl. Polyt. Jour. 251. 461. 2 It should be noted that Illipe oil is not necessarily identical with Mowrali seed oil. 3 The fat from Bassia butyracea is the commercial Phulwara butter. [Table Valenta, Dingl. Polyt. Jour. 251. 461. 2 From Bassia longifolia. 3 From Bassia latifolia. 4 Commercial fat. XI SHEA BUTTER 513 SHEA BUTTER (GALAM BUTTER) French —Beurre de Ce, Beurre de Slide, Suif de Noungou. German— Sheabutter, Galcimbutter. For tables of constants see p. 514. This fat is obtained from the seeds of Bassia Parkii. It is characterised by its grey or greyish-white colour and a peculiar aromatic odour. It is somewhat viscous, possessing, at the ordinary temperature, the consistency of butter. Shea butter consists, according to Stohmann, 1 of tristearin and triolein, in the proportion of seven parts of the former to three parts of the latter, and contains also 3'5 per cent of a wax-like substance. The sample examined in my laboratory had the acid value 29‘43 ; its low saponification value points to the presence of a notable amount of an unsaponifiable, or not readily saponifiable substance. 1 Muspratt’s Ohemie, 4th edition, vol. iii. p. 574. 2 L [Table XI VEGETABLE TALLOW 515 VEGETABLE TALLOW (OF CHINA) French— Suif vegetal cle la Chine. German— Chinesischer Talg. For tables of constants see p. 516. Vegetable tallow is the fat obtained from the seeds of the Chinese tallow-tree Stillingia sebifera (Croton sebiferum). The seeds are coated with the fat, which is removed by steaming. From the endosperm a brownish-yellow oil ( Ting-jou ) is obtained, used as a burning oil, and also for the preparation of varnishes on account of its drying properties. 1 Therefore vegetable tallow pre¬ pared in the laboratory by extracting the seeds with solvents contains some oil and is characterised by an iodine number higher than that of the commercial fat (cp. table). The following constants of the oil were ascertained by Hobein :— Specific gravity Saponification value Iodine value 0-9458 203-8 145-6 In its pure state this fat leaves no grease-spot on paper. The samples examined in my laboratory possessed an acid value varying from 7‘07 to 7*51. Be Negri and Fabris found 2*4, both for com¬ mercial fat and fat extracted from the seeds; Be Negri and Sburlati 1 give 2'2 as acid value. According to Maskelyne, vegetable tallow consists of palmitin and olein. A confirmation of this statement may be found in the fact that Hehner and Mitchell 2 obtained no stearic acid crystals from a specimen absorbing 22"87 per cent of iodine. The commercial vegetable tallow represents, as an inspection of the numbers recorded in the tables, demonstrates, a harder material than the fat extracted from the seeds by means of solvents (see above). Very likely the commercial article consists of a mixture of fats obtained from different species or even different families. Vegetable tallow is imported from China in hard, brittle white cakes weighing about 1 cwt., and is used for candle and soap making.. 1 De Negri and Sburlati, Jour. Soc. Chem. Ind. 1897, 339. 2 Analyst, 1896, 328. [Table. i Commercial sample. 2 Extracted from the seeds by means of ether (and carbon bisulphide), II Sclmi, 1S94, 32. No doubt the fat thus obtained contained some of the endosperm oil. 3 Prepared from the seeds by steaming. 4 Ten samples of commercial fat. XI PALM OIL 517 PALM OIL French— Huile cle palme. German— Palmoel. For tables of constants see p. 518. Palm oil is obtained from the fleshy part of the fruit of the palm trees Elmis guineensis and Elms melanococca , which form vast forests along the West Coast of Africa, extending between Cape Blanco and St. Paul de Loando. The fat is recovered in an exceedingly crude fashion by the natives, either by storing the fruits for some time in holes in the ground, when fermentation of the mass sets in and the oil rises to the surface, or by expressing the oil from the fresh fruits. The former process yields the lower but “ harder ” qualities, whereas by the latter the finer and “ softer ” palm oils are obtained. The fruit kernels remain intact in either of these processes (see “ Palm Nut Oil ”). The consistency of commercial palm oil varies, therefore, from that of butter (Lagos oil) to that of tallow (Congo oil); also the colour varies greatly, ranging, through all shades, from orange-yellow (Lagos) to dark dirty red. Palm oil has a somewhat sweetish taste, and, when fresh, a pleasant odour of violets, which also adheres to the soap made from it. Lower qualities of palm oil possess a dis¬ agreeable smell. Palm oil is characterised by the very large amount of free fatty acids it contains. Even in the fresh state the proportion of fatty acids, calculated as palmitic acid, amounts to 12 per cent, and may, in older samples, reach as much as 100 per cent—in other words, the splitting up of the glycerides may become complete. I have found in a large number of commercial palm oils from 50-70 per cent of free palmitic acid. The chief constituents of palm oil are palmitic acid, palmitin, and olein. Hazura and Griissner have found among the liquid fatty acids small quantities of linolic acid, identified by the sativic acid yielded on oxidation. The solid fatty acids consist, according to Norcllinger, 1 of 98 per cent of palmitic acid, 1 per cent of stearic, and 1 per cent of a heptadecylic acid, C l7 H ;u 0 2 (most likely identical with daturic acid, p. 47). The colouring matter of palm oil is bleached by exposure to air, or by heat, or by chemicals, such as chromic acid, etc. The two latter processes are adopted in practice for preparing bleached palm oil, which is almost colourless. By “ chemical ” bleaching the odour is destroyed, but it is not affected by heating to a high temperature. The colouring principle and the odour are not destroyed by saponi¬ fication with alkalis or lime (candle manufacture); acid saponification, however (p. 746), destroys both. 1 Jour. Soc. Ohem. Ind. 1892, 445. XI PALM OIL 519 The colouring principle of palm oil belongs to the class of lipo- chromes. The colour reactions for palm oil given by older writers are due to this substance. These colour reactions are useless, and in any case unnecessary, since palm oil cannot easily be confounded with other fats or oils. It may, however, be stated that some specimens of palm oil—Lagos oil and Old Calabar oil—give with sulphuric acid a colour reaction similar to that obtained with cod liver oil in chloro- formic solution, although the blue is much fainter ; other specimens do not give this blue colour, but turn red at once. Palm oil is, as a rule, not adulterated with other fats, and the commercial valuation embraces, therefore, the determination of water, of usual impurities (mostly sand, added fraudulently by negroes), and of the solidifying point. The proportion of water and sand together should not exceed 2 per cent; for any excess allowance has usually to be made by the seller. The following table, due to Y. de Schepper and Geitel, 1 gives the proportion of water, impurities, neutral fat, and the solidifying points of the mixed fatty acids of a number of commercial brands of palm oil:— Kind of Oil. Water. Impurities. Solidifying Point of Fatty Acids. Neutral Fat. Per cent. Per cent. °C. Per cent. Congo 078-0-95 0-35-07 45-90 16-23-0 Saltpond 2 . 3-5-12-5 0-9-17 46-20 15-25 Addah 4-21 0-35 44-15 18-0 Appam 3-60 0-596 45-0 25-0 Winnebah . 6-73 1-375 45-6 20-0 Fernando Po 2-68 0-85 45-90 28 Brass 3-05 2-00 45-1 35-5 New Calabar 3-82 0-86 45-0 40-0 Niger 3-0 0-70 45-0 40-0-47-0 Accra 2-2-5-3 0-60 44-0 53-76 Benin 2-03 0-20 45-0 59-74 Bonny 3-0-6-5 1-2-3-1 44-5 44-0-88-5 Gr. Bassa . 2-4-13-1 0-6-3 44-6 41-70-0 Cameroons 1-8-2-5 0-2-07 44-6 67-83 Cape Labon 3-6-6-5 0-7-1-5 41-0 55-69 Cape Palmas 9-7 2-70 42-10 67 Half Jack-Jack . 1-9-4-2 07-1-24 39-41-3 55-77-0 Lagos 0-5-1-3 0'3-0-6 45-0 58-68 Loando 1-5-3 0 1-0-1-9 44-5 68-76 Old Calabar 1-3-1-6 0-3-0-8 44-5 76-83 Gold Coast 1-98 0-50 41-0 69 Sherboro . 2-6-7-0 0-3-1-2 42-0 60-74 Gaboon 2-0-2-8 0-3-07 44-5 79-93-0 Palm oil is chiefly used in the soap and candle industries. In the latter case its “titer” is of the chief importance (cp. p. 133). On account of its non-drying qualities it is also employed in the tinplate industry, to preserve the surface of the heated iron 1 Dingl. Polyt. Jour. 245. 295. 2 This is the cheapest hard oil ; “ Drewin ” is the cheapest soft oil. 520 GLYCERIDES—VEGETABLE FATS CHAP. sheet from oxidation until the moment of dipping into the bath of melted tin. For the purposes of the tin industry “ palm oil greases ” are sold consisting of palm oil adulterated with cotton seed oil and mineral oil, spec. gray. 0 - 905. MACASSAR OIL German— Macassar Oel Physical and Chemical Constants of Macassar Oil Specific Gravity. Melting Point. Hehner Value. Saponific. Value. Iodine Value. At 15° C. Observer. °C. Observer. Per cent. Observer. Mgrms. KOH. Observer. Per cent. Observer. 0-924 Itallie 28 22 Schaedler Itallie 91 Itallie 230 213-4 221-5 Itallie Schaedler Lewko- witscli O0 CO 00 Itallie Lewko¬ witsch Physical and Chemical Constants of the Mixed Fatty Acids Solidifying Point. Melting Point. Iodine Value. °C. Observer. °C. Observer. Per cent. Observer. Titer Test. 51'6-53-2 1 Lewkowitsch I 54-55 Schaedler 49-7-50-7 Lewkowitsch Macassar oil is the fat from the seeds of Schleicheria trijuga. At the ordinary temperature it is a yellowish-white mass of buttery consistency. It consists chiefly of the glycerides of oleic, lauric, and arachidic acids, and contains also small quantities of acetic and butyric acids. A very small proportion of hydrocyanic acid seems to be characteristic of macassar oil. A sample examined in the writer’s laboratory had the acid value 35'43. XI SAWARRI FAT—MAFURA TALLOW 521 SAWARRI FAT 1 French —Iluile de noix de Souari. German— Souaributter. Physical and Chemical Constants of Sawcirri Fat Specific Gravity at 40° C. (Water at 15° = 1) Solidifying Point. °C. Melting Point. °C. Hehner Value. Per cent. Saponific. Value. Mgrms. KOH. Reichert Value. c.c. A norm. KOH. Iodine Value. Per cent. 0-8981 29-23-3 29-5-35-5 96-91 199-51 0-65 49-5 Physical and Chemical Constants of the Mixed Fatty Acids Solidifying Point. °C. Melting Point. °C. Mean Molecular Weight. Iodine Value. Per cent. 46-47 48-3-50 272-8 51-5 Sawarri fat is the fat contained in the nuts from Caryocar tomentosum, imported occasionally into this country as “ butter nuts.” The fat is colourless, and possesses a pleasant nutty taste. The free fatty acids in the specimen examined amounted to 2'4 per cent calcu¬ lated as oleic acid. The solid fatty acids consist chiefly of palmitic acid. The liquid fatty acids contain besides oleic acid—identified by its oxidation pro¬ duct, dihydroxystearic acid—some hydroxy acids that are readily converted into lactones. The acetyl value of the liquid fatty acids was 14’03, determined by the method described page 165. MAFURA TALLOW 2 French —Grciisse de Mafouraire. German— Mafuratalg. For tables of constants see p. 522. Mafura tallow is contained in the seeds of Mafureira oleifera (Trichilia emetica ), from which the fat is obtained by expression. The fat has a yellowish colour ; it is free from taste, and its odour recalls that of cacao butter. According to Villon , it consists of 55 parts of oleic and 45 parts of palmitic acid. The high melting point renders this fat especially suitable for the manufacture of soaps and candles. 1 Lewkowitsch, Jour. Soc. Chem. Ind. 1890, 844 ; Proceedings Ohem, Soc. 1889, 69. 2 De Negri and Fabris, Annalidel Ldboratoria Cthimico delle Gabelle, 1891-92, 271. XI NUTMEG BUTTER 523 NUTMEG BUTTER (MACE BUTTER) French— Beurre de muscade. German— Muscatbutter. For tables of constants see p. 525. Nutmeg butter is obtained from the seeds of Myristica officinalis (s. moschata , s. fragrans). This fat has the consistency of tallow, is of whitish colour, and possesses the strong taste and odour of nutmegs. Nutmeg butter varies considerably in its composition (see table below). It contains from 4 to 10 per cent of an ethereal oil (there¬ fore low saponification value); and about 45 per cent of a solid fat— chiefly trimyristin—the rest being a liquid fat containing free acid. Cold alcohol dissolves the liquid fat, the free acid, and the ethereal oil (unsaponifiable), leaving about 45 per cent undissolved. The undissolved portion yields on ^crystallisation from ether pure tri¬ myristin, melting point 55° C. Boiling alcohol, ether, and chloroform dissolve nutmeg butter almost completely. Corresponding to the varying composition of nutmeg butter, the constants given in the table p. 525 vary within comparatively wide limits. The following table contains a few constants for a number of samples determined by Diderich; the first five samples were pre¬ pared by that chemist himself by extracting nutmegs with ether:— No. of Sample. Specific Gravity at 15° C. Melting Point. Saponific. Value. Acid Value. Ether Value by Difference. Iodine Value. Solubility in Parts of Boiling Alcohol. 1 °c. 156-8 22-4 134-4 2 159-6 22-4 137-2 3 0-996 51 154-0 22-4 131-6 15 4 156-8 22-4 134-4 5 156-8 22-4 134-4 6 0-945 42 151-2 39-2 112-0 12 7 0-957 45 140-0 33-6 106-4 12 8 0-966 48 134-0 44-8 89-6 10 9 38-5-39 178-25 17-25 161-0 45-32 10 42 173-13 19-60 153-53 42-71 11 43 172-2 18-67 153-53 40-14 12 42-5-43 174-54 18-67 155-87 41-38 13 39 175-93 21-93 154-0 52-04 14 38-5-39 178-67 22-80 155-87 48-60 Spaeth examined a number of fats from various commercial brands; his results are given in the following table :— 524 GLYCERIDES—VEGETABLE FATS CHAP. Origin. Melting Point. °C. Saponific. Value. Iodine Valued Reichert- Meissl Value. Refractive Index. Butyro-refractometer at 40° C. Scale Divisions. Banda 25-26 170-173 77-8-80-8 4T-4-2 76-82 Bombay . 31-31-5 189-4-191-4 50-4-53-5 1-1-1 48-49 Menado . 25-5 169-1 76-9-77-3 74-74-5 Penang . 26 171-8-172-4 75-6-76-1 84-5-85 Macassar 25-25-5 171-8-172-4 75-6-76-1 78-5 Zanzibar. 25-5-26 169-9-170-5 76-2-77 77-5 Nutmeg butter must not be confounded with Ucuhubo, fat (p. 544), the fat obtained from Myristica becuhyba. 1 The iodine numbers are remarkably high. [Table Physical and Chemical Constants of Nutmeg Butter NUTMEG BUTTER 525 Observer Hiibl O d K 526 GLYCERIDES—VEGETABLE FATS CHAP. RAMBUTAN TALLOW 1 German— Rambutantalg. Rambutan tallow is obtained from the seeds of Nephelium Lappaceum. Physical and Chemical Constants of Eambutan Tallow Specific Gravity. Solidifying Point. Melting Point. Saponific. Value. Iodine Value. 0-9236 38-39 42-46 193-8 39-4 Physical and Chemical Constants of the Mixed Fatty Acids Solidifying Point. Melting Point. Saponific. Value. Mean Molec. Weight. Iodine Value. 57 58-61 186-4 300-9 41-0 The high mean molecular weight of the mixed fatty acids in¬ dicates the presence of fatty acids higher than stearic acid; indeed, arachidic acid was isolated. The proportion of oleic acid in the mixed fatty acids was found to be 45’5 per cent. A small quantity of stearic acid was obtained, but palmitic acid is stated to be absent. MKANYI FAT German— Mkanyifett. For tables of constants see p. 527. This fat forms about 67 per cent of the seeds of the East African Guttifera — Stearodendron Stuhlmanni, Engl, (called Mkanyi by the natives of Uluguru). The fat as prepared by the natives is of yellowish-white colour. The acid value of a specimen of the native product was found = 23 , 33. According to Heisef who examined this fat, Mkanyi fat consists chiefly of the mixed glyceride oleodistearin of the formula C 3 H 6 (0C 18 H 35 0) 2 (0C 18 H 33 0), melting at 44°-44-5° C. (cp., however, p. 3). 1 Baczewski, Jour. Soc. Chem. Ind. 1895, 1049. 2 Heise, Arbeiten mis dem kaiserlichen Gesundheitsamte, 1896, 540. XI CACAO BUTTER 527 Physical and Chemical Constants of Mkanyi Fat 1 Specific Gravity. Solidifying Point. Melting Point. °C. Saponific. Value. Mgrms. KOH. Hehner Value. Per Cent. Iodine Value. Reichert-Meissl Value. c.c. T V, norm. KOH. At °C. 40 98 (water 15° = 1) 0-8926 0-85606 38 40-41 190-5 95-65 38-63 1-21 Physical and Chemical Constants of the Mixed Fatty Acids 1 Solidifying Point. °C. 57-5 Melting Point. °C. 59 CACAO 1 2 BUTTER—(COCOA BUTTER) French— Beurre de Cacao. German— Cacaobutter. For tables of constants see pp. 530, 531. Cacao butter is expressed from the cacao beans, the seeds of the cacao-tree, Theobroma Cacao. The proportion of fat in the beans varies from 36*8 per cent in Caracas beans to 509 per cent in Tabasco beans. The fat has a yellowish-white colour, turning white on keeping. It possesses an agreeable taste and pleasant odour like chocolate. At the ordinary temperature it is somewhat brittle. Cacao butter consists chiefly of the glycerides of stearic, palmitic, lauric acids ( Traub , 3 however, could not detect any lauric acid), and, further, of small quantities of the glycerides of arachidic, 4 linolic, 5 formic, acetic, and butyric acids. Theobromic acid, C 64 H 12S 0 2 , stated by Kingzett 6 to occur in the fat, is, according to Graff absent, no higher acid than arachidic having been found by him. A specimen of cacao butter examined by Hehner and Mitchell 8 contained 39'9 to 40'6 per cent of stearic acid. The acid value of commercial samples of cacao butter was found by Dieterich from 1"0 to 2‘3; 1 grm. of the freshly expressed fat re¬ quired 006 to 0*25 c.c. decinormal alkali for neutralisation of the free fatty acids. The same observer contradicts the statement made by 1 Heise, Arbeiten aus dem kaiserlichen Gesundlieitsamte, 1896, 540. 2 I prefer the spelling “ cacao ” instead of “ cocoa,” in order to avoid confounding this fat with cocoa nut oil or kokum butter. 3 Wagner’s Jahresbericht, 1883, 1159. 4 Specht and Gossmann, Liebig's Annalen, 90. 126. 5 Benedikt and Hazura, Monatsliefte, 1889, 353. B Jour. Chem. Soc. 1878, 38. 7 Arch. Pharm. 1888, 830. 8 Analyst , 1896, 328. 528 GLYCERIDES—VEGETABLE FATS CHAP. several chemists that cacao butter does not readily turn rancid, cacao butter not behaving differently to any other fat in that respect. Thus a sample of cacao butter, requiring in the fresh state 0'06 c.c. of deci- normal alkali, took, after keeping for six months in bottles closed by parchment, 022 c.c. of alkali. The proportion of free acids increasing to double the amount during the customary operation of dehydrating and filtering in the hot water funnel, care should be taken that the fat is heated as little as possible. In some Dutch cacao butters Filsinger finds acid values as high as 56. Cacao butter dissolves in five parts of boiling absolute alcohol; it is, however, insoluble in 90 per cent alcohol. Cacao butter is often adulterated with tallow, almond, arachis, sesame (hazelnut) oils, cocoa nut oil, 1 “copraol,” 2 beeswax, stearic acid, and paraffin wax. For the detection of most of these adulter¬ ants the quantitative reactions will suffice. Paraffin wax and bees¬ wax lower the saponification value, and are indicated by a large amount of unsaponifiable matter. Cocoa nut oil, on the other hand, increases the saponification value considerably, and reduces the Hehner and iodine values. A high acid value would indicate stearic acid. The presence of the vegetable oils, almond, arachis, sesame (hazelnut), is easily recognised by the increased iodine value and the lowering of the melting point of the mixed fatty acids. In the case of suspected adulteration with tallow recourse must be had to the following two tests :— 1. Ether test, recommended by Bjorlclund . 3 —Place about 3 grms. of the sample in a test-tube, add twice the weight of ether, at the temperature of 18° C., close the test-tube with a cork, and effect solution, if possible, by shaking. If wax be present the solution will be turbid and refuse to become clear on warming. If, however, the fat dissolves to a clear solution, immerse the tube in water of 0° C., note the number of minutes that the liquid takes to become milky, or to deposit white flocks, and observe the temperature at which the solution becomes again clear when removed from the water. The following table gives the observations made on pure cacao butter and on samples mixed with tallow :— Turbidity at 0° C. after Minutes. Clear Solution at °C. Pure cacao butter ..... 10-15 19-20 Cacao butter + 5 per cent of beef tallow . 8 22 Cacao butter +10 per cent of beef tallow . 7 25 1 Especially the neutral cocoa nut oil: “ lactine ” (Ilamel-Roos). Some commercial cacao butters consist wholly of lactine. 2 Fancy name for a fat prepared from palm nut oil. 3 Zeit. analyt. Chemie, 3. 233. XI CACAO BUTTER 529 According to Kremel, 1 the ether solution need only remain clear for three minutes. According to the German Pharmacopoeia, a solu¬ tion of one part of cacao butter in two parts of ether should remain clear for a whole day, if kept at a temperature of 12° to 15' C. Dieterich, however, thinks that twelve hours should be deemed sufficient, genuine cacao butter having given deposits after twelve hours. It may, however, be mentioned that dika oil would pass this test. Bjorklund’s test has been modified by Filsinger , 2 who melts 2 grms. of the sample in a graduated test-tube, and agitates with 6 c.c. of a mixture consisting of four parts of ether (specific gravity 0 - 725) and one part of alcohol (specific gravity 0'810). A clear solution will result if the sample be pure, and remain so even on cooling to 0° C. 2. Aniline test, proposed by Hager? —Warm about 1 grm. of the sample with 2-8 grms. of aniline until solution ensues, and allow to stand for one hour at 15 J C., or for one and a half to two hours at 17° to 20° C. If the sample be pure cacao butter an oily layer will be found floating on the top of the aniline, not solidifying before the lapse of many hours. If, however, the cacao butter has been adulterated with tallow, stearic acid, or a small quantity of paraffin wax, granular particles will be observed in the oily layer, which, on being agitated gently, adhere to the wall. In the presence of beeswax, or of large quantities of paraffin wax, the fatty layer solidifies, whereas in the presence of large quantities of stearic acid the whole contents of the test-tube solidify to a crystalline mass without forming two layers. 1 Pliarm. Post. 1889, 5. • 2 Zeit. analyt. Cliemie, 1880, 247. 3 Ibid. 1880, 246. 2 M [Table i Forty commercial samples. There seemed to exist this proportionality between iodine value and refractive index, that the lower the iodine value the lower was the refractive index. XI CACAO BUTTER—KOKUM BUTTER 531 Physical and Chemical Constants of the Mixed Fatty Acids Solidifying Point. Melting Point. Saponific. Value. Iodine Value. Refractive Index. °0. Observer. °C. Observer. Mgrms. KOH. Observer. Per cent. Observer. At 60° C. Observer. 01 Hiibl 52 Hiibl 190 Thoemer 39 T De Negri & Fabris 1-422 Thoerner 4S-49 \ Bense- 32-6 Thoerner 51-52 / mann 49-501 Bense- 52-53 / mann 47-45 De Negri 4S-50 De Negri & Fabris & Fabris 46-47 Thoemer 49-50 Thoerner Titer Test. 48-48-27 Lewko- witsch It is evident from the description given that it is necessary to make comparative tests with a specimen of genuine cacao butter side by side with the suspected sample. For the detection of beeswax and paraffin wax preference should be given to the quantitative reactions previously described. Cacao butter is a by-product in the manufacture of chocolate, and therefore obtainable in large quantities. It is used in pharmacy and in the preparation of perfumes. KOKUM BUTTER, GOA BUTTER, MANGOSTEEN OIL French— Beurre de Cocum. German— Kokumbutter. For tables of constants see p. 532. This fat is obtained in the East Indies from the seeds of the Guttifera, Garcinia indica, Choisy (Mangosteena indica ). Heise 1 states that this fat consists chiefly of oleodistearin (like Mkanyi fat) cp. chap. i. p. 3, footnote. The fatty acids of kokum butter are oleic and stearic acids, with small quantities of (probably) lauric acid. A specimen examined by Heise contained 10'5 per cent of free fatty acids. 1 Arbeiten aus dein Jcaiserlichen Gesundheitsamte, 1896, 13. 302. [Table 1 The melting point varied according to whether the melted fat was allowed to solidify rapidly at 0° C., or kept at the ordinary tempera¬ ture ; in the former case the melting point was 32°-33° C., in the latter it rose to 40° C. after 24 hours’ standing (cp. chap. i. p. 4). XI BORNEO TALLOW—DIKA OIL 533 BORNEO TALLOW 1 2 French— Saif vegctalc de Borneo. German— Borneotalg. Borneo tallow is obtained from the fruits of a number of plants belonging to the family of Dipterocarpus, as Shorea stenoplera, Hopea aspera, etc. Borneo tallow has a light green colour, changing to yellow, then white on prolonged exposure to the air. In its consistency at ordinary temperature, and in its taste, it resembles cacao butter. It has a crystalline granular structure, and is covered with fine white needles of stearic acid, the quantity of which amounted, in the case of the sample examined by Geitel, to 9'5-10 per cent. Borneo tallow begins to melt at 35 -36" C., and is completely liquid at 42° C. The solidifying point of the free fatty acids is 53-5°-54° C.; they consist of 66 per cent of stearic and 34 per cent of oleic acids. The probable iodine value of the fat, calculated (by the writer) from the last given figure, would be about 31. I therefore place Borneo tallow next to hokum butter. DIKA OIL (OBA OIL) French— Beurre de Dika. German— Dikafett. Physical and Chemical Constants of Dika Oil Specific Gravity. Solidifying Point. Molting Point. Iodine Value. At °C. Observer. °C. Observer. °C. Observer. Per cent. Observer. 0-820 Scliaedler 30-31 Ilamel-Roos 30-9-31-3 Dietericli ? 29 Dietericli 34-8 Heckel 41-6 Heckel This fat is obtained from the seeds of Irvingia Gabonensisf a tree indigenous to the West Coast of Africa. Dika oil has an orange-yellow colour in the solid state; when melted it is yellowish - grey. It has a characteristic smell, which becomes more distinct on warming. According to Oudemans, 3 this fat consists of laurin and myristin only, to the exclusion of olein. The same statement has been re- 1 Geitel, Jour. Soc. Cliem. Ind. 1888, 391. 2 Heckel, 2° Memoire des Annales du Musee et de I’Institut Colonial de Marseille. 3 Jour, prakt. Chemie, 81. 356. 534 GLYCERIDES—VEGETABLE FATS CHAP. peated by Heckel, on the ground that he could not obtain from the. fatty acids an ether-soluble lead salt. This, however, is not definite proof (p. 192). In any case, it cannot hold good for the specimen examined by Dieterich, he having found 30-9-31 - 3 as the iodine absorp¬ tion of the fat, corresponding to about 34 per cent of olein. Dika oil easily becomes rancid; the acid value of a specimen examined by Dieterich was 19 - 6. Dika oil behaves like cacao butter in Bjorklund’s ether test for the latter. The fat from Irvingia Oliveri (indigenous to Cochin China), named Cay-Cay by the Annamites, is, according to Heckel , almost identical with Dika oil. MOCAYA OIL 1 Mocaya oil is obtained from the seeds of Acrocomia sclerocarpa {Cocos sclerocarpa), a palm-tree occurring in Paraguay and forming there vast forests. This oil is very similar to cocoa nut oil; it is white, of buttery consistency, and resembles also in its odour cocoa nut oil. It is soluble in alcohol and the ordinary solvents for fats. Physical and Chemical Constants of Mocaya Oil Solidifying Point. °C. Melting Point. °C. Saponific. Value. Reicliert-Meissl Value, c.c.~ KOH. Iodine Value. Per cent. 22 24-29 240-6 7-0 24-63 Physical and Chemical Constants of the Mixed Fatty Acids Solidifying Point. °C. Melting Point. °C. Saponific. Value. Mgrms. KOH. 22-20 23-25 254 Saponific. Value of tlie Non-volatile Acids. 244-8 1 De Negri and G. Fabris, Giorn. farmac. 1896, No. 12 ; Chem. Rev. 1897, 82. XI PALM NUT OIL 535 PALM NUT OIL French— Huile de palmiste. German— Palmkernoel, Kernoel. For tables of constants see p. 536. Palm nut oil is obtained from the kernels of the palm-tree fruit. The kernels are imported to Europe, and the fat is obtained from them either by expression or by extraction with solvents. The percentage of oil in the kernels varies a good deal with their origin. 1 The colour of the palm nut oil is white ; the darker oils, formerly met with owing to faulty manufacture, have disappeared from the market. It possesses a pleasant smell and an agreeable nutty taste. When fresh, the oil is neutral, but on keeping it easily turns rancid with liberation of free fatty acids. The following table gives the pro¬ portions found in various samples of palm nut oil:— Free Fatty Acids in Palm Nut Oil Kind of Oil. No. of Samples. Free Fatty Acids as Oleic Acid. Observer. Per cent. 2 13-26-13-39 Salkowski Expressed oil . 27 3-30-17-65 Nordlinger Extracted oil . 10 4-17-11-42 ” The chemical composition of palm nut oil is the following, accord¬ ing to Oudemans 2 :— Glyceride. Triolein Stearin \ Paliuitin - Myristin J Laurin S Caprin I Caprylin j Caproin J Per cent. 26-6 33-0 44-4 1 In the following table, due to Nbrdlinger (Jour. Soc. Chem. Ind. 1895, 585), details are given. Origin of Palm Kernels. Proportion of Fat. Per cent. Origin of Palm Kernels. Proportion of Fat. Per cent. Sierra Leone 48-6 Togo District, French 49-3 Island of Sherboro 46-7 Lagos . 50-4 Liberia .... 49-4 Benin. 49-8 Grand Bassa 50-2 Niger. 50-5 Half Jack .... 50-8 Brass. 52-5 Apollonia .... 47-2 Calabar .... 50'9 Dixcove .... 48-2 Bonny .... 51-0 Cape Coast Castle 50-2 Opobo .... 52-3 Winnebah .... 46-1 Cameroons .... 49-0 Quitta. 48-4 Congo . 47-4 Togo District, German 52-1 Loanda .... 50-9 2 Jour, pralct. Chemie, 11. 393. XI PALM NUT OIL 537 Valenta 1 has examined the fatty acids from palm nut oil. On passing a current of steam through the acids a small quantity volatilised, the distillate consisting of caproic acid and most likely also of caprylic acid. After drying the acids that remained behind and distilling them, at a pressure of 100 to 160 mm., six fractions were obtained, the examination of which led to the results recorded in the table:— Fraction No. Boiling Point. Melting Point. Saponif. Value. Iodine Value. Yield. Saturated Fatty Acids. Oleic Acid. Approximate Composition of Fatty Acids. °C. °C. Per cent. Per cent. Per cent. Caprylic, capric 1 135-190 0 4 100 0 2 190-200 31-5 310 2-6 10 97-2 2-8 Capric, oleic 3 200-205 37-5 275 3-4 \ 7'8 f 58 96-3 3-7 Lauric, capric, oleic 205-225 32-5 264 91-5 8*5 Lauric, myristic, 5 225-245 31-5 251 16-7 15 81-7 18-5 oleic 6 245-270 35-0 219 41-3 5 54-6 45-S Myristic, palmitic, oleic 7 Residue 8 The chief constituent of palm nut oil is therefore lauric acid. From the iodine value we calculate the proportion of olein as 12 to 20 per cent. Palm nut oil is very nearly related in its chemical com¬ position to cocoa nut oil. It is remarkable, like the latter, for the high saponification value, and the notable amount of glycerides of volatile fatty acids (cp. “ Cocoa Nut Oil,” p. 538). Like cocoa nut oil, it requires strong caustic soda for saponification, and yields a hard white soap, which is only thrown out in the “ salting out process by the addition of a large amount of salt.' 2 Palm nut oil is chiefly used for soap-making. For its employment in the manufacture of vegetable butter, see “ Cocoa Nut Oil (p. 541). By subjecting palm nut oil to hydraulic pressure a hard fat is obtained, and the liquid “palm nut oleine .” A sample of the latter, examined by the writer, had the titer test 16'8 to 17 C. COCOA NUT OIL French— Huile de coco, Beurre de coco. German— Cocosoel, Cocosnussoel For tables of constants see pp. 539, 540. Cocoa nut oil is the fat obtained from the kernels of the cocoa nut, especially those from the two species Cocos nucifera and Locos butyracea. In commerce three qualities of oil are distinguished : (1) Cochin oil, 1 Zeit. f. angew. Chemie, 1889, 335. 2 Qp, Lewkowitsch, Jout . Soc. Dyers ctntl Colourists , 1894 ? March , Jour. Soc. C hem. Ind. 1894, 258. 538 GLYCERIDES—VEGETABLE FATS CHAP. the finest and whitest quality, prepared in Cochin (Malabar); 1 (2) Ceylon oil, chiefly imported from Ceylon, where the fat is expressed or boiled out on a large scale; (3) Coprah oil, the fat from the coprah, i.e. the kernels, shipped in enormous quantities to Europe, where the oil is either expressed or extracted in a similar way to palm nut oil. In order to reduce its bulk the coprah is dried before shipping, hence the commercial terms “sun-dried” and “kiln-dried” coprah. By expressing the kernels in the cold an oil is obtained of the solidifying point 13°-12° C., and the melting point 20° C. This cold- pressed oil, however, is not a commercial product, being used where it is produced as a substitute for butter fat. Cocoa nut oil is, in our climate, at the ordinary temperature a solid white fat possessing a bland taste, and, when fresh, a peculiar though not unpleasant odour. It turns, however, easily rancid, acquiring at the same time a disagreeable flavour and an acrid taste. Coprah oil is richer in free fatty acids than Ceylon oil. The writer has found in a great number of samples of Coprah oil free fatty acids to the extent of 25 per cent, Ceylon oil as a rule only containing from 5 to 10 per cent of free acids calculated as oleic acid. Cocoa nut oil resembles palm nut oil in its chemical composition, containing, like the latter, large proportions of trimyristin and trilaurin, smaller quantities of tripalmitin and triolein, and also the glycerides of the volatile caproic, caprylic, and capric acids. It is practically free from hydroxy acids 2 ( Lewhowitsch ). This composition explains the very high saponification and the high Beichert values of both fats. The two constants are so charac¬ teristic of them, that both oils are easily distinguished thereby from all other fats with the exception of butter fat. Cocoa nut oil is soluble in alcohol to a considerable extent, one volume of oil dissolving in two volumes of 90 per cent alcohol at 60° C. In consequence of its abnormal chemical composition, the behaviour of cocoa nut oil is different from that of other oils and fats, excepting only palm nut oil, in that it is not easily saponified by weak caustic lyes. It requires alkaline lyes of high strength for saponification, and is so easily converted into soap by them that it is quite sufficient to stir the oil and caustic alkali well together and allow the mixture to stand. After some time saponification will take place with liberation of heat. (Soap-making by the cold process.) The soap thus formed is very hard, and combines with a very large amount of water without becoming soft. Cocoa nut oil soap has further the remarkable property of requir¬ ing very large quantities of salt to throw it out of its aqueous solution. Cocoa nut oil is chiefly used for soap-making and in the candle manufacture (night-lights); for the latter purpose the fat is subjected to hydraulic pressure, when a soft fat (“ cocoa nut oleine ”) and a 1 There are also the commercial brands: Cochin Australia, Cochin Mauritius. J Unpublished experiments. Physical and Chemical Constants of Cocoa Nut Oil XI COCOA NUT OIL 539 <32 05 a; T5 CD d’ 2 O o rO H rt o a d d o ? > Harris 1 The proportion of glycerol has been found by Allen for three samples from ll - 59 to 14 - 7 per cent. These high values—obtained by the permanganate method (p. 208)—seemed to speak in favour of Berthelofs statement that Japan wax contains dipalmitin. Benedikt, however, has been unable to detect diglycerides on boiling with acetic anhydride (p. 190). Commercial Japan wax contains from 0'02-0’08 per cent of ash. Japan wax is easily distinguished from true waxes by its yield- 1 Determined in the writer’s laboratory ; the fatty acids had been previously freed from unsaponifiable matter. The Japan wax examined contained IT per cent of the latter. 2 This requires further investigation, as Ilehner and Mitchell’s method of determining tearic acid in fats and oils breaks down, curiously enough, in the case of Japan wax. Free Fatty Acids. Per cent. 9T3 3-87 8- 96 9- 03 12-72 9T0 XI MALABAR TALLOW 549 ing glycerol. Its detection in beeswax, for the adulteration of which it is sometimes used, will be described pp. 660, 666. On account of its physical characteristics adulteration with other fats is easily detected. The presence of tallow will be indicated by the low melting point and the high iodine absorption of the sample. According to Stohmann, 1 commercial Japan wax is frequently adulterated with from 15 to 30 per cent of water. La Wall 2 found a number of commercial samples adulterated with starch to the extent of 20 to 25 per cent. On treating the adulterated wax with a solvent (p. 89) the wax only is dissolved. A more rapid method to detect starch is to moisten a freshly cut surface with iodine solution. MALABAR TALLOW (PINEY TALLOW) 3 French— Suif de Piney. German— Malabartalg, Vateriafett, Pineytalg, Pflanzentalg. Physical and Chemical Constants of Malabar Tallow Specific Gravity. Solidifying Point. Melting Point. Saponific. Value. At J 0. Observer. °C. Observer. °C. Observer. Mgrms. KOH. Observer. 9-4 0-9102 Dal Sie 30-5 Viertlialer 36-5 Viertlialer 191-9 Hohnel and and and Bottura Bottura Wolfbauer 15 0-915 Hohnel 30 Dal Sie and 42 Hohnel Wolfbauer and Wolfbauer Physical and Chemical Constants of the Mixed Fatty Acids Solidifying Point. Melting Point. °C. Observer. °C. Observer. 54-8 Hohnel and Wolfbauer 56-6 Hohner and Wolfbauer This fat is obtained from the seeds of Vateria indica. In the fresh state it has a greenish-yellow colour; on exposure to the air it is rapidly bleached. Its consistency approaches that of mutton tallow. 1 Muspratt’s Chevrie, 4th edition, vol. iii. p. 571. 2 Jour. Soc. Cliem. Ind. 1897, 247. 3 Wagner’s Jahresbericht, 1884, 1186. 550 GLYCERIDES—ANIMAL FATS CHAP. The sample of Malabar tallow examined by Hohnel and Wolfbauer consisted of 19 per cent of free fatty acids and 81 per cent of glycerides. The solid fatty acids melted at 63 - 8° C. WILD OLIVE FAT The seeds of a wild olive of the Simaruba variety (found native in San Salvador) yield a solid yellow fat, which is used for soap-making. The fat melts at 30° C.; it yields over 90 per cent of solid white fatty acids, melting at 48°-49° C. These fatty acids are stated to consist of equal parts of saturated and unsaturated fatty acids; the former melted at 54°-55° C., and were fractionated by means of the barium salts into three portions, melting at 58°-59° C., 44° C., and 38° C. 2. Animal Fats The fats here described vary in their hardness, like the vegetable fats, in inverse proportion to the amount of olein they contain, or, in other words, to the amount of iodine they absorb. Butter fat, in a similar fashion to cocoa nut and palm nut oils, occupies a singular position owing to its high proportion of volatile acids. In a system based on similarity of chemical composition butter fat would be classed with those two vegetable oils, but it is more convenient, and will remain so until our knowledge of the subject is much more extended than it is at present, to retain a subdivision into vegetable and animal fats. The liquid fatty acids were until recently considered to consist of oleic acid only, but it is proved now that some animal fats contain less saturated acids (linolic ?), notably so the American lards (cp. chap. x. p. 232). A few of the fats possess distinct drying properties (cp. chap. x. p. 232). The constants of a number of lesser known fats are collated in the following table, due to Amthor and Zink :— [Table ANIMAL FATS Remarks. / Possesses dry- \ ing properties. Iodine Value. Per cent. Fatty Acids. ^ lO 0 ^ !>. ^ ^O^HOOOOOOOitN^ CM • : 05 : OiOCOCO^OOOO^NNCOTt< 1 —i • * Fat. vO rl 0 iONCOHNCO(NNOOOOOOOH^O (MoOiOCOCOCONNN^O^DiOvO»OCOCO(M(M Reichert Value. Am- normal KOH. OO O O O O 0 00 0500 h w : : i : co w h o : io »p 05 n 05 k o o o co o 05 • o • o 05 05 O 05 • 05) Oi 05) 05) 05) 05) O M 1 —1 03 (03 rH T—1 M rH T—1 rl rl H ri rl (N Melting Point. Fatty Acids. °C. COO 310)0)BtOroOO l f''HHlOr|IBOO COnt< .COCOCO^IMrfrfH^OVIrlflOtDlOlO OO :<»OOCoA'AlOOO'i'ToOCO* 05 05 03 03 ''tf coco COCOCOCO J> CO CO VO lO vo CO Solidifying Point. Fatty Acids. °C. lp> CO H TH^03F'-OW^F^v0t^OOOC003 03 CO .COCOCOCOCOCOC003COCOCOVOVO^VO VO O : OC0HOC0l0C3(0'0(Dl0C005NH 03 co cocococoo3cocoo3^coco-^^^io CO Fat. °C. O^tHOO (OC5NN CO N CD CO H CO • 03 03 rH . . M rH C3 C3 . 03 03 03 CO Hti o ^ • VO 03 VO * * h)H rH ! rH O ^±1 05 ^ 03 H 03 H 03 rH 03 03 03 03 03 CO CO ^ Specific Gravity at 15° C. Fatty Acids. vO 03 O CO OO CD H 03 ^ co F"- CO 05) CO OO K CD O CO 03 03 H co : : : : co 03 : 03 : 03 co 01 »o cd 0 vo 05) • • • -05)05)05 -05 -0505050505)0505 o ooo o ooooooo Fat. CO O 03 CO VO ?H 05 Tfi VO 05 vO 1^ 05 03 rH 03 ^ 03 O O 03 vO H 05 03 : : : : 03 ^ 03 co 03 : oq co co co co co co 05 • • • -0505050505 -05050505050505 o ooooo ooooooo Kind of Fat. German. Auerhahn . Wildente . Hausente . Staar Taube . . Truthahn . Fuchs . . Dachs . . Edelmarder Hauslmlm . litis . . . Hund . . Wildkatze . Hauskatze . Elch. . . Reli . . . Damhirsch. Gemse . Blackcock. . Wild duck Domestic duck Starling . Pigeon . . . Turkey . . Fox . . . . Badger. . . Pine marten . Chicken . . Polecat . . Dog. . . . Wild cat . . Domestic cat . Elk .... Roebuck . Fallow buck . Chamois . . 552 GLYCERIDES—ANIMAL FATS CHAP. HORSE FAT French —Graisse de clieval. German— Pferdefett. For tables of constants see pp. 553, 554. Fresh horse fat is of a yellowish colour, and has a buttery con¬ sistency. On standing it separates into a solid and liquid portion. It is neutral when fresh ; older samples become rancid, and absorb oxygen (cp. p. 12). In a sample of kidney fat Hehner and Mitchell could not detect any stearic acid. In consequence of the increasing consumption of horse meat, horse fat has become a commercial article. It is used by the poorer classes on the Continent as an edible fat in place of lard, and serves, no doubt, as an adulterant for more expensive fats. The following constants for horse fat from various parts of the body have been published by various observers :— [Table Capillary tube method. XI HORSE MARROW FAT—HARE FAT 555 HORSE MARROW FAT 1 French— Mo'elle de cheval. German— Pferdemarkfett. Physical and Chemical Constants of Horse Marrow Fat Specific Gravity. Solidifying Point. Melting Point. Saponific. Value. Reichert Value. Iodine Value. At 15° C. °C. °C. Mgrms. KOH. c.c. norm. KOH. Per cent. 0-9204-0-9221 24-20 2 35-39 2 199-7-200 1-0 77-6-80-6 Physical and Chemical Constants of the Mixed Fatty Acids Specific Gravity. Solidifying Point. Melting Point. Saponification Value. Iodine Value. At 15° C. °C. °C. Mgrms. KOH. Per cent. 0-9182-0-9289 36-34 3 42-44 2 210-8-217-6 71-8-72-2 Horse marrow fat is pale yellow. A specimen of freshly rendered fat had the acid value I/O, and a sample three months old 0*8. HARE FAT French— Graisse de lihre. German— Hasenfett. For tables of constants see p. 556. The fat obtained from several hares is, according to Amthor and Zink, 3 pale yellow to orange - yellow, very soft, and separates on standing into a thick yellow oil and a white crystalline precipitate. Even in the fresh state it has a disagreeable rancid smell, which becomes more unpleasant on standing. Exposed in a thin layer—spread on a glass plate—hare fat dries in about 8 days to a tolerably viscid varnish, becoming solid after 4 more days. The iodine number after 38 days’ exposure was 19'4. Hare fat would thus appear to be a drying fat. Hare fat contains linolic acid (chap. ix. p. 318). The acid value of the specimen examined by Amthor and Zink was, in the fresh state, 2*73, and 8 after 6 months. 1 Zink, Forschungsberichte uber Lebensmittel, etc., 1896, 441. 2 Capillary tube method. 3 Zeit. f. analyt. Chermie , 1897, 8. Capillary tube method. XI RABBIT FAT 557 RABBIT FAT French —Graisse de lapin. German— Kaninchenfett. For tables of constants see p. 558. This fat is of a dirty yellow colour, separating on standing into a liquid and a solid portion. The fat from the wild rabbit differs very notably from that of the tame rabbit in the iodine value. On exposure to the atmosphere the fat from the wild animal dries after 7 days to a moderately solid varnish, becoming solid after 6 more days. After 50 days exposure the iodine number was only 26. The fat from the tame animal does not exhibit drying properties. The acid values of the wild rabbit fat and tame rabbit fat w ei e 7 - 2 and 6'2 respectively. [Table Physical and Chemical Constants of Rabbit Fat Zeit.f. analyt. Chemie, 1897, 9. 2 Capillary tube method. 3 Bulletin de l'Assoc. Beige, 1896 (9), 323. XI GOOSE FAT 559 As a rule, the fat of domesticated animals is richer in olein than that of wild animals, but in this case as well as in that of the wild goose the reverse obtains. GOOSE FAT French —Graisse d’oie. German— Gdnsefett. For tables of constants see pp. 560, 561. Goose fat is a semi-pellucid, pale yellow fat of granular con¬ sistency. It consists of olein, palmitin, stearin, and small quantities of caprin. The proportion of soluble fatty acids varies, according to Young , from 0'7 to 3 - 5 per cent, calculated as oleic acid. There are added in the table some constants of the fat from the wild goose; from the iodine value it would follow that the wild animal’s fat is richer in olein than that of the domesticated goose. [Table hysical and Chemical Constants of Goose Fat 560 GLYCERIDES—ANIMAL FATS CHAP. Hehner Value. Observer. Bensemann Young Rozsenyi Per cent. 95-88 92-4-95-7 94-5-95-3 Melting Point. Observer. Scliaedler Bensemann Rozsenyi Amtlior and Zink p 25-26 33-34 27-5-31-7 32-34 Solidifying Point. Observer. Scliaedler Rozsenyi Amtlior and Zink p 18 rising to 99 18-1-18-4 18-20 18-20 Specific Gravity. Observer. Young Rozsenyi Amtlior and Zink J > 0-909 0-9229-0-9300 0-9274 0-9158 d +3 ii CO < 5 > vn ■ in - lO H i-i 1 i-i 1 i-i CO 03 ?-( > 30 ,, ,, ,, >) 59 ,, ,, ,, „ 75 „ „ 0-90116 0-90209 0-90302 0-90494 0-90736 0-89246 0-89328 0-89421 0-89617 0-89850 Melting- Point.—Although the melting point of the fat is not of itself of great importance, many adulterated lards having the same melting points as pure lard, still its determination should never be neglected. In the case of unadulterated pig’s fat it is possible to ascertain from what part of the body the fat has been rendered; as will be seen by a glance at the following table :— 1 Jour. Soc. Cthem. Ind. 1896, 620. 2 Ibid. 1890, 1162. 572 GLYCERIDES—ANIMAL FATS CHAP. Melting Points of Lards from different parts of Hogs—American and European Source. Fat from Melting Point. °C. Observer.* American . Foot 35-1 Wiley >> Head Back Kidney Leaf 35-5 Leg 42-5 J > Ham 44-5 Spaeth European . Back 33-8 Kidney 43-2 ,, Leaf 44 ” Goske 2 takes the solidifying point of the lard in a manner identical with that employed in Dalican’s titer test. The following table contains his numbers :— Fat. Home-rendered lard J > 5 ) Pure steam lard y> ? j ? > ? ? j j > j >> j j Adulterated lard European J > J ) American Solidifying Point. °C. 27-10-28-62 26'64-29'34 29-10-29-95 24- 10-26-00 25- 05-25-5 26- 40-27-06 24-9 23-67-26-18 30-50 29-73-29-80 29-90-30-15 31-95-33-00 35-90-36-58 35-50-35-75 In this table account is only taken of adulteration with tallow, the presence of which is masked by addition of lard oil. The solidifying- point of the fatty acids would not be of much use in the case of adulteration with cotton seed oil; maize oil and other vegetable oils, however, if present in not too small quantities, may thus be indicated. Fresenius z believes that positive results may be obtained with the help of his “ Thermo-table.” Iodine Value.—Pure lard should not absorb more than 63 per cent, and not less than 46 per cent of iodine. A sample, the iodine value of which falls outside of this range, must be considered as adulterated or at best as inferior lard (see table, p. 573). Of course, the converse does not follow that a sample having a normal absorption must be pure, as the combinations of fats of low (tallow, cocoa nut oil) and high absorptions (cotton seed, arachis, maize oils) enable the 1 Cp. also Denustedt and Voigtlander’s table, p. 568. 2 Jour. Soc. Ghem. Ind. 1893, 470. 3 Ghem. Ztg. 1896, 130. 151. XI LARD 573 adulterator to prepare a variety of mixtures which will satisfy the limits laid down above. Therefore a normal iodine absorption cannot be considered of itself as a final test. Thus in the case of artificial lards made from steam lard, tallow stearine, and lard oil, to the exclusion of vegetable oils, the iodine value will as a rule be about correct. The following table, due to Goske, gives the iodine values of several artificial lards calculated from those of its components, assuming the following iodine numbers for the latter: beef stearine, 20 ; steam lard, 65 ; mutton tallow, 40 ; lard oil, 85. Pat No. | Beef Stearine. Steam Lard. Mutton Tallow. Lard Oil. Per cent. Per cent. Per cent. Per cent. 1 10 90 2 15 85 3 70 30 4 25 45 30 5 35 25 40 Calculated Iodine Value. Per cent. 60-5 58- 25 57‘50 59- 75 57-27 The influence of exposure on the iodine value of lard may be gathered from the table, p. 569. _ As will be seen from the following table, it is possible, if aduitei ac¬ tions with foreign fats be excluded, to ascertain by means, of the iodine value from what part of the animal the lard has been derived : Source. Pat from Iodine Value. Observer. American Head Foot Back Leaf Ham Gut lard 85-03 66-2-70-4 65- 0-66-6 63 77-28 69-5-69-6 65 63-6-66-7 61-5-65-1 61 58 53-1 52-55 60-4-66-7 59-63 677-69-0 66- 6-68-4 60 Wiley v. Raumer Dennstedt and Voigtlander Dupont Wiley v. Raumer Dupont v. Raumer Dennstedt and V oigtlander Dupont Dupont Spaeth Wiley v. Raumer Dennstedt and Voigtlander v. Raumer Dennstedt and Voigtlander Dupont European . Back Leaf Ham 53-0-58-5 61-7 50-4 55-0 v. Raumer v. Raumer Dennstedt and Voigtlander 574 GLYCERIDES—ANIMAL FATS CHAP. Steam lard, consisting as it does of the mixed fats from all or at least various parts of the animal, may therefore in some cases have a normal value, say up to 63, in other cases it may absorb more iodine. Wiley has found the iodine value of steam lards to vary from 60'34 to 66-37. Whereas, considering the very wide limits between 46 and 63, which some chemists even wish to see extended in an upward direc¬ tion, the iodine value of the fat affords but indefinite information ; by far more certain results are furnished by the determination of the iodine value of the liquid fatty acids. In the present state of our knowledge this is the only reliable method for ascertaining admixture of vegetable oils and fats with lard. From the general table given above we gather that in the case of European lards the iodine values of the liquid fatty acids vary between 90 and 96, and in the case of American lards between 97 and 106; therefore the highest limits permissible should be 96 for European lards, and 106 for American lards. If, therefore, the iodine value of the liquid fatty acids of a sample be found to lie above these limits, adulteration with a vege¬ table oil is proved ; if much below these limits, admixture with cocoa nut oil or palm kernel oil must be assumed. In order to emphasise this point, I give here the following table:— Iodine Value of Fat or Oil. Fat. Liquid Fatty Acids. Observer. Lard, “ Western Steam Lard ” . 65 "4 104-5 Wallenstein and Finck 1 ,, Berlin .... 527 96-6 ,, Vienna ..... 60-9 95-2 9 ' ,, Hungarian 60-4 96-2 ,, Roumanian 59-5 96-0 ,, Bavarian (5 samples) Beef tallow, Australian 52-2-61-2 92-8-96-6 v. Raumer 2 38-3 92-2 Wallenstein and Finck ,, Berlin .... 45-2 92-4 ,, Hungarian Cotton seed oil, American, white 38-6 927 108-0 147-5 ,, >, ,, yellow 107-8 147-3 9 9 ,, ,, Egyptian, bleached . 106-5 146-8 >, ,, >, yellow 108-0 148-2 ,, ,, Peruvian . Niger Seed oil . 106-8 147-8 133-5 147-5 Maize oil . 122-0 140-7 Arachis oil .... 98-9 128-5 Rape oil ..... 101-1 1207 Cocoa nut oil. 8-0 54-0 ) y 1 Jour. jSoc. Chem. Ind. 1894, 79. 2 Zeits.f. angew. Chemie, 1897, 210. XI LARD 575 The following table, due to v. Bawmer, 1 gives a comparison of iodine values of lards from various parts of the hog (American), and of their liquid fatty acids :— American Lards (v. Bawmer) Pat from Iodine Value of Fat. Liquid Fatty Acids. Head I. 70-0-70-4 102-4 „ II. . . . 66-2-66-4 97-8-97-6 „ III. . . . 68-2-68-4 101-2 Back I. . 64-6-64-9 101-6-101-0 „ II- • • 63 "6-63 "6 102-8-102-3 III. . 66"7-66 - 5 101-1-100-6 Leaf I. . 66-4-66-7 103-0-102-6 ,, II. ... 62-7-62-9 97-8-97-8 „ III. 60-7-60-4 96-9 Foot .... 69-5-69-6 98-6-98-3 Ham I. ... 67-9-67-9 101-6-10D0 ,, II. ... 67-9-67-7 99-9-100-2 „ HI- • • • 68-7-69-0 103-0-103-2 If, e.g., tallow were mixed with so much cotton seed oil as is re¬ quired to produce a fat of the consistency of lard—33 per cent—the iodine value of the liquid fatty acids would be 113'7-114T (v. Baumer). It must, however, be understood that if the iodine value of a sample under examination is found within the permissible limits, the lard cannot be reported yet as unadulterated. For on the one hand the proportion of any admixed vegetable oil may have been compensated by cocoa nut oil (the taste of the desired product permitting) or to some smaller extent by beef tallow. The test will, therefore, have to be supplemented in suspected cases by special tests for cocoa nut oil and tallow (see below). With regard to methods for the approximate quantitative determination of vegetable oils, see “ Edible Fats,” chap. xii. p. 683. Thermal Tests.—As a preliminary test the rise of temperature on treating with concentrated sulphuric acid or with bromine will be found to furnish useful results in a short time; this holds especially good of the second method. MaumenS Test .—The rise of temperature found on mixing the sample with sulphuric acid has been recommended for the detection and even approximate estimation of cotton seed oil in lard by Hehner, Ambilhl, Wiley , and Engler and Bupp, whereas Williams failed to obtain decisive results. The rise of temperature obtained by different experimenters has been stated so differently, that the safest plan will be to make com¬ parative tests with pure specimens of lard and cotton seed oil before examining the sample. It need hardly be said that the sample must be thoroughly dry before testing. The following table contains a few values given by the observers named:— 1 Zeits. f. angew. Chemie, 1897, 210. Acid of 100 per cent H 2 S0 4 , prepared by mixing fnming'acid with cone, commercial acid. XI LARD 577 In order to obtain more decisive results the liquid portion ob¬ tained by expression may be examined as well (Langfurth). Heat of Bromination .—The following numbers were obtained by Hehner and Mitchell ; 1 the iodine values calculated from the tempera¬ tures observed are collated with those actually found by experiments with Hiibl’s solution :— Fat. l. Heat oi' Bromi- nation. Rise of Temperature. 11. Iodine Value. Experiment. III. Iodine Value calculated from I. °C. Per cent. Per cent. Lard No. 1 ..... 10-6 57'15 58-3 ,,2. 10-4 57-13 57 "2 „ 3. 11-2 63-11 61-6 4. 11-2 61-49 61-6 „ 5. 11-8 54-69 64-9 ,, 6 . 11-8 63-96 64-9 ,, 7. 10-2 57"15 56-1 „ 8. 10-4 57’80 57-2 „ 9. 9-0 50-38 49-5 .,10. 11-0 58-84 60-5 Lard +10 per cent cotton seed oil 11-6 64-13 63-8 Refraetometrie Examination. — Amagat and Jean state that adulterations with tallow, cocoa nut oil, and cotton seed oil are easily recognised by means of the oleo-refractometer. Although not ab¬ solutely reliable, and, indeed, in some cases valueless, as in that of lard mixed with 10 per cent of beef tallow, this method may be employed in conjunction with others as a preliminary or as a corro¬ borative test in doubtful cases. The numbers recorded in the follow¬ ing table may therefore be found useful:— 1 Jout. Soc. Chem. Ind. 1897, 88. 2 P [Table 578 GLYCERIDES—ANIMAL FATS CHAP. Kind of Fat or Oil. “ Degrees" in the Oleo-refractometer. Fat. Fatty Acids. Lard, pure ....... -12-5 -30 Steam lard ....... —18 -30 Lard stearine .. - 10 to -11 Beef tallow ....... -16 ; -17 -40 ,, stearine ....... V eal ,, Cotton seed oil ...... -34 -19 + 20 + 10 ,, stearine ..... Sesame oil ...... + 25 ■+■ 20 -18 Aracliis oil ...... -15 Lard with 10 per cent of beef tallow -12 ,. ., 20 ,, ,, . . - 13 ,, „ 50 ,, ,, . . ,, ,, 5 ,, cotton seed oil . -14 -33 - 10 ,. 10 ,. ,, . - 8 ,, ,, 15 ,, ,, . - 7 ., 20 ,, ,, ,, . - 6 ., 25 ,. ,. ., . - 5 ,, ,, 30 ,, ,, „ . - 4 ., 40 ,, ,, . - 0 ,. 50 ,, ,, ,, . . - 3 .,5 ., ., stearine . - 11 ,, 10 - 7 ., 20 - 4 ,, 30 - 3 „ ,, 40 - 2 „ „ 50 Lard with 20 per cent of aracliis oil + 1 - 8 -23 ,, ,, 20 ,, sesame ,, -20 ,, 40 per cent; beef tallow 40 per cent; cotton seed oil 20 per cent .... -24 Steam lard 60 per cent ; beef tallow 15 per cent; aracliis oil 25 per cent - 8 Lard 60 per cent; mutton tallow 25 per cent ; aracliis oil 15 per cent .... -13 -22 Cocoa nut oil . -54 From the following table, due to Dupont, 1 it will be seen that the American lards show less deviation than the European lards, and if judged solely by the standard of European lards, they might be rashly condemned as containing cotton seed oil:— American Lard. Oleo-refractometer “ Degrees.” Iodine value. From leaf -11-5 58 ,, back -5 61 ,. intestines -7 62 ., head - 7 63 ,, foot -4 65 Gut lard -11 60 Rancid lard -7 63 Sour lard -6-5 64 1 Jour. Soc. Chem. Ind. 1895, 828. XI LARD 579 The difference between European and American lards is not quite so distinctly shown in the refractometric constants as in the iodine absorption. A glance at the following table proves this:— Refractive Indices determined by means of the Butyro-refractometer. ■ Kind of Pat. European. American. Scale Divisions at 40° C. Observer. Scale Divisions at 40° C. Observer. Lard from head . 52-52-6 Dennstedt & Voigtlander ,, ,, back . 50-2-50-4 Mansfeld 51-8-52-4 ,, ,, leaf ,, ,, outer part of leaf 51-2 ” 50-2-52 ” 50-7 , , ,, ,, belly. 50-4 ,, ,, ,, intestines . foot . 49-0 ” 44-8 ,, ,, ham . 51-9-53 ” Beef tallow. 49-0 Horse fat 53-7 Cocoa nut oil 35-5 Cotton seed oil . 61 The influence of rancidity on the refractometric constant is illus¬ trated by the numbers given in the following table; they are collated with the Reichert-Meissl values ( Spaeth ):— Deviation in the Butyro-refracto¬ meter calculated for 25° C. Reichert-Meissl Values. After 1 year. After 3 years. After 3 years. 59-35 62-60 60-21 62-30 4-3 60-49 62-45 9-36 57-71 58-75 1-32 60-35 62-70 61-35 63-10 58-14 63-1 3-74 "Whereas adulteration with vegetable oils and fats can be detected with certainty, the recognition of beef tallow, oleomargarine, and beef stearine, presents considerable difficulties, the more so as small quantities down to 5 per cent repay the cost entailed in the mixing. I shall indicate in the following lines special methods for the detection of the more important adulterants. 580 GLYCERIDES—ANIMAL FATS CHAP. Seed Oils. —-The phospho-molybdic acid test(p. 316) has been recom¬ mended by several observers as indicating presence of vegetable oils in lard with certainty. The writer has, however, shown 1 that, on the one hand, a slightly rancid lard also reduces the reagent, and, on the other hand, that an admixture of less than 15 per cent of cotton seed oil with pure lard cannot be thus detected. This test can therefore only be admitted as a preliminary one. The writer’s experiments have since been confirmed by Samelson and Tennille. The surest proof for the presence of seed oils is obtained by the determination of the iodine value of the liquid fatty acids (see above). If the presence of a vegetable oil has been indicated by an abnormally high iodine value, one of the following four oils should be specially looked for :—Arachis oil, sesame oil, cotton seed oil (cotton seed stearine), maize oil. Araehis Oil. —Renard’s test should give a positive result. Sesame Oil.—This would be detected readily by Baudouin’s reaction. Cotton Seed Oil.—The nitric acid test (p. 381) will afford very valuable corroboration of the results obtained by the iodine test, but it should be borne in mind that some lards undoubtedly give the brown colouration with nitric acid. Further corroboration will be given by Becchi’s test if a positive reaction has been obtained (p. 382). It should, however, be remembered that even a brown colouration is not always absolute proof of presence of cotton seed oil, since Wesson 2 has obtained a brownish deposit due to silver sulphide with a sample of fresh hog’s fat. His observation has been confirmed by Mariani, and, further, by Bevan, z who has found that lard exposed to the air for some time gave a strong reaction with silver nitrate. In the latter case, undoubtedly, a body of an aldehydic nature had been formed. The following modifications of the silver nitrate test have been proposed with a view to the examination of adulterated lards :— Pattinson i dissolves in a test-tube 40 drops of the melted lard in 10 c.c. of ether, and adds 2 c.c. of an alcoholic solution of silver nitrate (1 part of silver nitrate to 100 of alcohol). He allows the test-tube to stand for five to six hours in a place protected from light. If cotton seed oil is present, the silver is reduced, and the solution assumes a maroon colour, the depth of the colour depending on the proportion of cotton seed oil the sample contains. Hehner omits the colza oil, using the silver nitrate reagent only {No. I. p. 382). He adds one volume of the silver solution to two volumes of the oil and heats for fifteen minutes. Wesson 5 prepares his reagent by dissolving 2 grms. of silver nitrate in a mixture of 200 c.c. of 95 per cent alcohol and 40 c.c. of ether, and before using it he exposes it to sunlight for some time, and decants the clear liquid from the deposit. 5 c.c. of the reagent are shaken with 10 grms. of the melted lard in a cylindrical vessel of 60 1 Lewkowitsch, Jour. Soc. Chem. hid. 1894, 619. 2 Jour. Chem. Soc. 1894, Abstr. ii. 75. 3 Analyst, 1894, 88. 4 Jour. Soc. Chem. Ind. 1889, 30. 5 Jour. Chem. Soc. 1894, Abstr. ii. 75. XI LARD 581 c.c. capacity, and placed in a water-bath for fifteen minutes. Lard containing much cotton seed oil gives a mirror, the liquid at the same time assuming a dark greenish colour. In presence of small quantities of cotton seed oil the fat is said to become red, some metallic silver being deposited. Pure lard becomes only slightly darker and of a purple tint, with little or no separation of silver. Presence of cotton seed oil is only proved if metallic silver has separated. 1 The test becomes safer if both the sample and the liquid portion, obtained from it on expressing the fat after it has been allowed to solidify by cooling slowly to 25°-30° C., are examined ( Goske ). As has been stated already, cotton seed oil heated to 240 C. does not reduce silver nitrate. For the detection in lard of cotton seed oil which has been thus treated, Crook 2 recommends the following process :— Ten grains—0'648 grm. — of the sample are placed in a cup¬ shaped porcelain capsule of about half an ounce capacity. A small disc of white filter paper (previously soaked in hydrochloric acid, washed, and dried) is just moistened with a 12 per cent solution of silver nitrate, and placed in the concave side of a watch-glass, which is then inverted over the capsule containing the sample. The capsule is then slowly heated in an oil-bath to 115° C., when the source of heat is immediately withdrawn. In presence of even less than 1 per cent of heated cotton seed oil, a very marked colouration appears on the disc, varying from a light brown to a nearly black. If the sample be pure and fresh no colouration is observed. In the writer’s hands this method has proved to be worthless. For other colour reactions for cotton seed oil, as Hirschsohn’s and Labiche’s test, cp. p. 384. Cotton seed stearine can be detected by the increased specific gravity and the colour reactions for cotton seed oil. Allen recognises it by the adulterated lard remaining fluid for some time at a com¬ paratively low temperature after having been melted, and when allowed to cool remaining softer than the original sample. As lard gives a liquid product with sulphur chloride, soluble in carbon bisulphide, cotton seed oil may also be detected qualitatively by means of that reagent ( B. Warren , Jones 2 "). In the presence of cotton seed oil a hard mass partly insoluble in carbon bisulphide is produced. I have tried this method and found it very useful indeed. My observations are given in the following table :— 1 Schweitzer and Lungwitz (Jour. Soc. Chem. Ind. 1894, 615) recommend Milliau’s test (p. 383) as thoroughly reliable for the detection of cotton seed oil in lard, repeating Milliau’s statement that admixture with cotton seed oil down to 1 per cent is shown by the mirror-like precipitate of metallic silver. 2 Analyst , 1893, 221. 3 Ibid. 1888, 170. 582 GLYCERIDES—ANIMAL FATS CHAP. Mixtures of Lard and Cotton Seed Oil 5 grms. of fat dissolved in 2 c.c. CS 9 , added 2 c.c. S 2 C1 2 , and placed on the water-bath Lard. Per cent. Cotton Seed Oil. Per cent. Solubility of Product in Carbon Bisulphide. 100 0 No reaction Completely soluble 90 10 Thickens after 35 minutes „ 80 20 J J 5 J 30 „ 52 per cent ,, 70 30 26 ,, 39-6 60 40 Solid after 18 „ 34-8 „ „ 50 50 10 „ 37-4 40 60 J3 8 „ 30-6 30 70 7 „ 32-6 20 80 « „ 30'0 10 90 4 „ 28-4 ,, ,, 0 100 >> 5) 3 „ 24 It will be best to test the sample side by side with pure lard, or better still, with mixtures of lard and cotton seed prepared in a similar fashion to that illustrated by the table. Maize Oil. —If arachis and sesame oils are absent a too high iodine value can then be due only to cotton seed oil or maize oil. The solidifying point of the mixed fatty acids would in this case lead to a decision if only one oil be present. If both are present this method breaks down. Cocoa nut oil or palm kernel oil will be recognised by the high saponification value, and especially by the definite Reichert value of the sample. The search for cocoa nut oil may become necessary under the conditions pointed out above, i.e. if the iodine value of the lard or of the mixed fatty acids is abnormally low. The detection of tallow and beef stearine is a difficult problem, and, at the present state of our knowledge, can only be solved success¬ fully by strict comparison with samples of pure lard and of lard mixed with known proportions of the adulterant suspected. This problem is rendered all the more difficult as American steam lard behaves very differently from European home-rendered lard ( Goske ). Beef stearine, when present in quantities of at least 10 per cent, may be detected, according to Leopold Mayer, by melting a somewhat large quantity in a capacious beaker and allowing it to stand at a temperature of 31° to 32° C. for 36 hours. Pure lard crystallises homo¬ geneously from the bottom of the vessel upwards, whereas presence of beef stearine is said to be indicated by the appearance of crystals resembling cauliflower. This test will only have the value of a pre¬ liminary one. Beljield dissolves the sample in ether, and examines the crystals from the ethereal solution under the microscope. Forty drops of the XI LARD 583 melted lard are dissolved in 10 c.c. of ether in a test-tnbe and allowed to cool (Pattinson 1 ). Should no crystals form, the cork is removed from the tube and a loose plug of cotton-wool substituted, when crystals will be obtained by the spontaneous evaporation of the ether. If the crystals have been formed too rapidly it is best to redissolve them by addition of more ether. Some of the crystals are then placed on an object-glass and examined microscopically. Crystals from pure lard usually form oblong plates, occasionally radiated, and have oblique terminals, whereas those from beef tallow form curved tufts somewhat of the shape of an “/.” The difference in the shape of the crystals 2 is caused by the larger proportion of stearin in beef stearine. This has been proved experimentally by Hehner and Mitchell . 3 Goskef who uses this method, employs 1 grm. of lard, and allows the solution to crystallise at from 12°-13 C. (at 4 C. or below but rarely good crystals are obtained). Lard adulterated with beef stearine crystallises in small needles grouped in tufts radiating from centres. Lard stearine remaining in solution, plates are never observed in presence of beef stearine. GosJce stated at first that 5 per cent of beef fat, or 15 per cent of mutton fat (which does not crystallise so well), may be safely detected. But later he admits that the question becomes complicated if for beef stearine oleomargarine is substituted. Besides, German home-rendered lard does not yield the crystalline plates, crystallising as it does in needles which are not readily discernible from those yielded by beef stearine under the same conditions. Hehner, however, rejected this method, as the stearine crystals from hog’s caul-fat have the same appearance as beef stearine crystals. Wallenstein 5 considers this objection as irrelevant, since caul- fat alone is hardly brought into the market. He recommends in such cases to subject the crystals to a grinding action by pressing down the cover glass (which Stock, however, deprecates), when the oblique terminals are said to become distinctly visible. Stock 6 compares the crystals obtained from an ethereal solution with those from two standard sets of mixtures, the first consisting of pure lard melting at 34°-35° C., with 5, 10, 15, and 20 per cent of beef stearine melting at 56° C.; the second of pure lard, of melting point 39°-40° C., with 5, 10, 15, and 20 per cent of beef fat melting at 50° C. Stock proceeds as follows The melting point of the sample is determined first by the capillary tube method. Suppose the melting point be found at 34° C., 3 c.c. of the melted fat are run into a graduated stoppered cylinder of 25 c.c. capacity, 21 c.c. of ether are added, and the fat dissolved at 20 -25 C. 3 c.c. of each of the first set of mixtures are treated in exactly the same way. The five cylinders are cooled down to 13° C., and allowed to remain at that temperature—particularly during the last hours—for twenty- four hours. 1 Jour. Soc. Chem. Ind. 1888, 30. 2 For photographs of characteristic crystals refer to Lard and Lard Adulterations, etc. s Analyst, 1896, 328. 4 Jour. Soc. Chem. Ind. 1893, 469. 8 Chem. Zeit. 1894, 1189. G Analyst, 1894, 2. 584 GLYCERIDES—ANIMAL FATS CHAP. An approximate estimate as to the amount of the adulterant is arrived at by reading off the apparent volume of deposited crystals. The ether is then poured off as far as possible, and 10 c.c. of fresh ether at 13° C. are added in each case. The cylinders are again shaken, cooled as before, and the proportion of crystals read off. Finally, the contents of the cylinders are emptied into weighed shallow beakers, the ether drained off carefully, the mass allowed to dry for fifteen minutes at 10 C., and weighed. The weight obtained for the sample under examination is compared with the weight of crystals obtained from whichever of the standards comes nearest to it. The second set of mixtures is used for samples with a higher melting point. The actual presence of beef fat must then be proved by micro¬ scopical examination, using a l-inch objective and the C eyepiece. No sample of pure lard melting below 39° C. yielded more than O'Oll grm. of crystals under the above-stated conditions. A sample of the melting point 45 - 8° C. gave, however, 0T46 grm. of crystals. 1 In the present state of our knowledge, Stock’s modification of Belfield’s method must be considered the best. Unfortunately, the form of crystals obtained from softer lards differs from those obtained from harder ones. According to Helmer and Mitchell 2 the former yield nothing but broad plates with pronounced chisel-shaped ends, whereas from the latter bunches of more pointed, though still chisel- edged, needles crystallise. On being repeatedly recrystallisecl from ether they become more and more neeclle-like, approaching the form of beef stearine crystals, until they become unclistinguishable from them. It may, therefore, be hoped that the direct determination of stearic acid will lead to practical results, for lards contain (see above p. 567) from 6-16 per cent of stearic acid, whereas beef stearine gave 50T9 per cent. More decisive results still will be obtained if the determination of stearic acid be carried out with the solid acids, freed from the liquid acids, so that the combination of the stearic acid and iodine tests should lead to decisive results. 3 For the preparation of lard oil (French— Huile de graisse; German— Schmalzoel) “ prime steam lard ” is subjected to pressure in hydraulic presses. The press-cakes are lard stearine used for making “ compound lard,” and possess, therefore, a higher value than lard itself. The expressed oil, lard oil , is used as an edible oil, and also as a high-class burning and lubricating oil. According to the pressure and the temperature employed, the solidifying point of lard oil will 1 Gladding recently described his modus operandi, Jour. Soc. Chem. hid. 1896, 560. 2 Analyst, 1896, 328. 3 A curious method to detect and determine the quantity of beef fat in lard is proposed by Ballo, viz. to measure the amount of air enclosed in the melted fat ; pure lard on solidifying is stated not to enclose any air, whereas pure beef fat encloses air (100 grms. about 6 - 5 to 8 - 8 c.c.) Ballo is of the opinion that even 3 per cent of beef fat may be thus detected [Jour. Soc. Chem. Ind. 1897, 764). XI LARD 585 vary, so that some specimens will deposit stearine at the ordinary temperature, or even solidify completely at 10 -12 C., whereas other’s do not deposit any crystals unless cooled to the freezing point. The specific gravity of a sample examined by Allen was 0"915 at 15-5° C. According to the same author, the density of pure lard oil should not exceed 0'916 (0'920 according to Schweitzer and Lungwitz). If heavier, it is presumably adulterated with fish oil or a vegetable oil. Long 1 gives the following table for the specific gravity of lard oil:— c. 18 20 25 30 35 Specific Gravity. 0-9137 0-9122 0-9088 0-9053 0-9019 The iodine value of lard oil will, of course, vary considerably with the temperature and pressure employed in preparing it. Thus Sclmeitzer and Lungwitz find for several specimens from 67 to 79, whereas Dupont gives 80-82. In the elaidin test, in Maumeni’s test, and with nitric acid, lard oil behaves very much like olive oil. Pure lard oil should be free from fatty acids. Adulterants, such as mineral oils or vegetable oils, may be detected by the quantitative reactions, and possibly also by colour reactions (cp. Cotton seed oil, Sesame oil). 1 Amer, Chem. Jour. 1888. [Table 0 9300-0 9399 Zink 37'9-38 Lewkowitsch 44-46 Zink 204'5 Zink 55 '5 Lewkowitscli 40-39 Zink XI BEEF MARROW FAT—BONE FAT 587 Beef marrow fat is the fat from the marrow bones of cattle. Medullic acid, stated by Eylerts to occur in beef marrow, is, accord¬ ing to Thummel, 1 a mixture of palmitic and stearic acids. A specimen of freshly rendered marrow fat had the acid value 1*6, and a specimen eight months old l - 9 (Zink). Beef marrow fat is used in pharmacy, and for making pomades. BONE FAT French —Saif d’os. German— Knochenfett. For tables of constants see p. 588. Bone fat, if prepared from fresh bones by boiling, has a white to yellowish colour, and a faint odour and taste. Its consistency is that of butter. It does not readily turn rancid, and is for that reason a valuable lubricant. Bone fat, as found in commerce, is usually recovered from old, partially putrid bones by either boiling with water or by extracting with solvents, such as petroleum ether. The fat obtained by the latter process is dark brownish, and has a most unpleasant smell, which is very difficult to remove. It contains large quantities of free fatty acids, and the following impurities : Lime soap, 2 cholesterol, calcium lactate, calcium butyrate, hydro¬ carbons from the petroleum ether, and colouring substances. Pure bone fat prepared by boiling with water is slightly brownish, and contains, besides neutral fat and free fatty acids, but small quantities of impurities. The extracted fat is therefore far more difficult to bleach than the boiled out fat. It should be borne in mind that in small manure works, where kitchen refuse is worked up, the kitchen grease is usually added to the bone fat. Bone fat is chiefly used for candle-making and soap-making ; its valuation is made like that of tallow (p. 596). 1 Bericlite , 1890, Ref. 493. 2 Cp. p. 749. [Table 590 GLYCERIDES—ANIMAL FATS CHAP. Troicky, 1 differing from Valenta , considers that bone fat extracted with petroleum ether is superior to boiled out fat, because containing less water and ash, and more solid fatty acids. But this is an erroneous opinion, for the fat extracted with solvents has a dark colour, unpleasant smell, and is richer in oleic acid. Troicky’’s analyses are given below :— 2 a CM oo CM o CO s 1^- O p co r—1 cs co "u tO cs GO CS rt © co CO CO CO CO CO CO CM & 2 a co OS CO o p CO o CM co CM cs co O Sh OS CO Th oo CM to w CO co O fa *° to to to to ° CO . o -a fa'S to- o ^ cs C/J CO CO «.2 1-1 1-1 rH rH 'S o a o o CM o o o o < S 9 s1 p p o -5* CO >> ^ 00 CO rH pH CM CM r _l os CS oo CS cs cs cs fa • ~ i—h co o to CO CM o p to CM to o CO c ° © o CM 7—1 rH r " H 1-1 r " 4 a o 00 CO to CM a 8 T 5 O p o to o CO © o 00 o oo OS o tp rH d iS o ** ca * (5 o -4-3 ■*£ t? 2 b O O o -4-3 o o > J5 # >> * North American tallow. . . : . . 45 43-5 South American tallow, beef..... 44 - 5 >} ,, ,, mutton .... 45 Bone fat ........ 42-5 The numbers recorded in the subjoined table, due to Ik Scliepper and Geitel, give melting points of tallows and some fats used for its adulteration :— Kind. Titer Test. "C. Various kinds of tallows.40-46 Margarine ....... 38-44 Pressed tallow . . . - . . . 50 - 5 Mutton tallows . . . • . . 46'1 Beef tallows ....... 44'5 Suif d’epluchures 1 .40‘7-42'3 Bone fat 2 . . • • • • • 4:0'3 Cotton seed oil. . . . . . . 34 Cocoa nut oil ....... 23 Stearine grease.44 BEEF TALLOW French —Suif de bceuf. German —Binder talg. For tables of constants see pp. 593, 594. Beef tallow, when fresh, is almost white, free from any disagree¬ able odour, and almost tasteless. Foreign tallow is greyish-white to yellow (Russian), and marked by a more or less rancid flavour. One part of tallow dissolves in forty parts of alcohol of 0'821 specific gravity. Tallow consists nearly exclusively of the glycerides of palmitic, stearic, and oleic acids. The amount of olein may be calculated from the iodine value. Thus a tallow absorbing 40 per cent of iodine will contain 46 per cent of olein. The proportions of palmitin, stearin, and olein vary in the fats rendered from different parts of the same beast. Leopold Mayer has examined the fats obtained from different parts of the body of a Hungarian ox, three years old, with the following result:— 1 This fat has a green colour, and emits on drying the odour of sulphurous acid. It is most likely a mixture of a low class tallow and sulphocarbon (olive) oil. 2 Containing 4'5 per cent of ash, partly in the form of soap. IX BEEF TALLOW 593; 2 Q Australian. 2 Berlin town tallow. 3 American beef. 4 Home-refined. XI BEEF TALLOW 595 The ratio of stearin to palmitin in tallow is about 1:1. In oleo¬ margarine palmitin predominates, consequently the proportion of stearin in tallow stearine must be larger. According to Wallenstein 1 a sample of tallow stearine had the following composition :— Olein . . . . 21 '4 per cent. Stearin . . . . 65’4 ,, ,, Palmitin . . . 13*2 ,, ,, The ratio of stearic acid to palmitic acid is therefore 100 : 20"2. More definite information as to the amount of stearic acid and its proportion to palmitic acid is obtained by Hehner and Mitchell’s method of determining stearic acid (chap. vi. p. 198). The following table 2 contains some of their results :— Iodine Number. Stearic Acid in Fatty Acids. Beef stearine . 2-0 Per cent. 50-19-51-05 Oleomargarine 46-50 21-26-23-6 Margarine I. . 24-8 „ II. . . 41 T9 11-72 The amount of free fatty acids in tallow naturally varies con¬ siderably. Deering has stated the results of his examination in the following table :— Free Fatty Acids in Beef Tallow Kind of Tallow. No. of Sample. Acid Value. Calculated as Oleic Acid. Per cent. Remarks. Russian .... 5 5-1-24-6 0-55-12-3 Old 2 10-1-12-4 5-05- 6'2 Fresher „ P.Y.C. . 3 4-4-10-4 2-2 - 5-2 Old „ P.Y.C. . 3 4-4- 4-7 2-2 - 2-35 Fresh Australian 4 3-5-30-47 1-75-15-2 Town tallow . 2 9 0-14-2 4 5 - 7T .. 1 50 25 Six years old Examination of Tallow 1 Water and non-fatty substances are determined in the usual manner. The non-fatty substances in genuine tallow are fragments of tissue and calcium phosphate. Soft fat is sometimes hardened by addition of lime, the lime soap producing a firmer consistency. On extracting the fat with ether or 1 Jour. Soc. Chem. hid. 1893, 54. 2 Analyst, 1896, 328. 596 GLYCERIDES—ANIMAL EATS CHAP. chloroform the lime soap remains undissolved, and the lime may then be determined quantitatively. The extracted, filtered, and dried fat serves for the double purpose of estimating the commercial value of the tallow and detecting adulterants if present. Valuation of Tallow. —The value of tallow is determined by the solidifying point of its fatty acids; the higher this is the more valuable the fat. The titer test of tallow intended for candle-making should not be below 44° C. Tallows of a lower titer are employed for soap-making. A large amount of free fatty acids depreciates the value con¬ siderably, as the fatty acids obtained from such tallow in the lime saponification process turn out dark, and the soap made from it has an inferior colour (“ foxy ”). Of course, rancid tallow should not be used for lubricating purposes. The amount of free fatty acids is estimated according to the directions given above (p. 148), adopting 275 as the mean molecular weight of the tallow fatty acids (cp. also “ Candles,” p. 749). Detection of Adulteration. —Tallow is adulterated with resin, resin oil, paraffin wax, 1 palm nut oil, cocoa nut oil, distilled grease stearine, cotton seed oil, and cotton seed stearine; also goat’s tallow must, under certain conditions, be considered an adulterant. Resin, resin oil, and paraffin wax are easily detected by the methods described in chap. vii. Presence of cocoa nut or palm nut oil would be detected by a low solidifying point of the fatty acids, a high saponification value (tallow 196, cocoa nut oil 257‘3-268-4, palm nut oil 247‘6), and a low iodine value (tallow 36-40, cocoa nut oil 8-9, palm nut oil 10-17). The different solubilities of cocoa nut and palm nut soaps on the one hand, and of tallow soap on the other, in concentrated solutions of common salt or caustic alkalis, have been made use of by Lant Carpenter and by Eoediger for the detection of cocoa nut and palm nut oils in tallow. Lant Carpenter dissolved 10 grms. of the fatty acids of the sample in 39-40 c.c. of normal caustic soda, boiled, and brought the soap solution to 50 grms. by evaporation or by addition of water, as the case may be. A saturated solution of common salt was then run in from a burette until the soap was thrown up. I have tested this method, but found it very unsatisfactory, as yielding erratic results. Eoediger saponifies 150 grms. of the sample with caustic lye, and throws the soap up by a measured quantity of caustic soda of 1‘35 spec. grav. Saponification of tallow by means of aqueous alkalis requiring a good deal of practice, and therefore likely to lead to very disappointing results in the hands of an inexperienced operator, I cannot recommend Eoediger’s method. If at all necessary to use such a method, the writer proposes to combine the two methods in the following manner :—10 grms. of the 1 In Germany paraffin oil is used by the custom-house officers for “denaturing” tallow if caustic soda be objected to. XI BEEF TALLOW 597 fatty acids of the sample are dissolved in 40 c.c. of normal caustic soda, boiled, and brought up to 75 grms. by addition of water, when caustic soda of spec. gray. 1'35 is run in from a burette, with constant stirring, until the soap is thrown up. The following table gives some results I have obtained by this method :— 10 Grms. of Fatty Acids from Brought up to 75 Grms. Required Caustic Soda 1 -35. c.c. Tallow ...... Cocoa nut oil .... Palm nut oil .... 50 parts of tallow and 50 parts of cocoa nut oil . 50 parts of tallow and 50 parts of palm nut oil . 8-6; 9-9 40-4 ; 39-0 27-8 22-0 20-1 ; 197 It is evident that the quantitative reactions in conjunction with the solidifying points give far more reliable and characteristic results. Distilled grease stearine has been employed, according to L. Mayer, 1 for the adulteration of tallow. This “ stearine ” is obtained by distilling “ recovered grease,” and expressing the solid portion of it; it consists chiefly of stearic acid (p. 691), isooleic acid, and smaller quantities of cholesterol and isocholesterol. 2 Its detection is therefore easy. In the first instance, a tallow thus adulterated would have a peculiar smell and possess a high acid value. The best method, however, is to saponify the tallow, extract the soap with ether, and test the residue obtained on evaporating the solvent for cholesterol and isocholesterol (p. 84). A rapid process would be to test the sample with acetic anhydride and concentrated sulphuric acid, when a green fluorescence 3 would point to the presence of isocholesterol and, inferentially, to distilled grease stearine. The fatty acids obtained from tallow thus adulterated turn yellow after a few days, and exhibit the peculiar smell characteristic of wool fat and its derivates. A high acid value may also be due to admixture with stearic acid from cotton seed mucilage; in that case, of course, no isocholesterol reaction will be obtained. Cotton seed oil and cotton seed stearine would be indicated by a high iodine value. Their detection is, however, easily and with certainty effected, according to Mayer, by melting the sample and allowing the fat to crystallise at a temperature of 35° C. After 18 hours’ standing the liquid portion is removed by squeezing through a cloth and then examined. The determination of the “ titer test ” and of the iodine absorption will afford sufficient evidence of the adulteration. In presence of cotton seed oil or cotton seed stearine the solidifying point will be below 39° C., and the iodine value far above 55, the normal value for tallow oleine (cp. also “Detection of Cotton Seed Oil in Lard”). 1 Dingl. Polyt. Jour. 247. 305. 2 Lewkowitsch, Jour. Soc. Chem. Ind. 1892, 142. 3 Ibid. 1892, 144. 598 GLYCERIDES—ANIMAL FATS CHAP. Goat’s tallow, sold in commerce as mutton tallow, would also be considered an adulterant by a candle-maker; although it has a high melting point, and consequently a large proportion of stearin, it-is not suitable for candles, on account of its fatty acids not crystallising well, but solidifying into an amorphous mass, from which it is difficult to remove the imprisoned oleic acid. The candles prepared in the ordinary way from goat’s tallow are of low quality, not possessing the metallic ring of first-class candles, and easily becoming discoloured on account of the oleic acid they retain. The detection of goat’s tallow is difficult; the surest indication would be given by the smell of the sample (ChevreuVs “acide hircique”). A mixture of 70 parts of goat’s tallow and 30 parts of cotton seed oil has been sold, according to Mayer , as beef tallow. Neither the solidifying point of the fatty acids nor the iodine value of this fat reveal the fraud. Recourse must therefore be had to the deter¬ mination of the iodine value of the liquid fatty acids. The nitric acid and Becchi’s test given for cotton seed oil (see p. 382) (or Mayer's device of allowing the fat to crystallise at 35° C.) would not give equally certain results. MUTTON TALLOW French —Saif de Mouton. German— Ilammeltalg. For tables of constants see pp. 599, 600. Mutton tallow very much resembles beef tallow, indeed, it is frequently sold mixed with the latter. It is, however, as a rule, harder than beef tallow, and consequently its solidifying and melting points, as well as those of its fatty acids, are higher. It is also more liable to turn rancid, and cannot for this reason be used in the manufacture of superior butter-substitutes or best soaps. Deering 1 has found for four samples of Australian mutton acid values varying from 1‘7 to 14-3, corresponding to 0‘85 to 7'15 per cent of free fatty acids. The fat rendered from various parts of two sheep gave, according to Moser 2 the following results :— Fat from Fat. Fatty Acids. Solidifying Point. Melting Point. Saponific.Value. Solidifying Point. Melting Point. °C. °C. “C. °C. Kidneys 407-40-9 54-0-55-0 194-8-195-2 51-9-51-9 56-2-56-5 Caul and intes- 39-2-39-7 52-0-52-9 194-6-194-8 50-4-50-6 54-9-55-8 tines Adipose tissue . 34-1-34-9 49-5-49-6 194-2-194-4 43-7-46-2 50-7-51-1 1 Jour. Soc. Chem. Ind. 1884, 541. 2 Bericht der Thdtigkeit der Versuchsstation. Wien, 1882, 1888. Physical and Chemical Constants of Mutton Tallow XI BUTTER EAT 601 Very instructive is also the information contained in the follow¬ ing table, due to Hehner and Mitchell ; 1 the different specimens of fat were taken from a Scotch sheep eighteen months old:— Fat from Iodine Value. Melting Point of Fatty Acids. Stearic Acid. Per cent. °C. Per cent. Kidneys . 48-16 45-6 26-2-27-7 Back 61-3 41-4 24-8 Neck 48-6 42-2 16-4 Breast 58-2 33-8 About 1 Ham 50-6 40-8 No deposit after two days BUTTER FAT French —Beurre de vache German— Butterfett. For tables of constants see pp. 602, 603. Butter fat or milk fat is the fat of cow’s milk. 2 Normal cow butter, not melted and not salted, has, according to Koenig, the following composition :— Fat .... 87 "0 per cent Casein .... 0-5 Milk sugar 0-3 „ Asli .... 0-3 ,, Water .... • 1U7 „ The percentage composition of butters varies, however, to a con¬ siderable extent, the proportion of fat, on the one hand, rising in some cases to 95 per cent, whereas, on the other hand, the water may reach as high a figure as 35 per cent. 1 Analyst, 1896, 327. 2 The following constants of the milk fats from other animals have been pub¬ lished :— Milk Fat from Specific Gravity. Solidi¬ fying Point. Melt- Saponifie. Hehner Reicliert- Meissl Value. Iodine Refractive Observer. At 15° C. At 100 °c. mg Point. Value. Value. Value. Index. Goat. 0-9312 0-8G69 24-31 27-38-6 221-6 86-5-87-3 23-1-25-4 30-4-34-6 1-4596 Solberg Sheep 31 36-5 28-6 Pizzi 29-30 32-9 „ Mare. 11-2 ,, Ass . 13-1 „ Buffalo 29 38 26-2 Solberg Reindeer . 0-9428 0-8640 34-39 37-42 219-2 86-89 31-4 25-1 1-4647 Gamboose 220-4-231-7 86-9-87-5] 34-7-35 32-35 H. D. Richmond Woman 30-31 Volatile fatty acids 1-4 per cent Laves Physical and Chemical Constants of Butter Fat—continued Butter from cows fed on cotton seed cakes have a considerably (by 8° to 9° C.) higher melting point. (Lupton, Jour. Amer. Cliem. Soc. 1891, 134.) Cp. footnote p. 634. 604 GLYCERIDES—ANIMAL FATS CHAP. The composition of a good English butter is, according to Bell, the following:— Fat ..... 90"27 per cent Curd ..... 1-15 „ Salt . . . . 1-03 ,, Water .... 7 *55 ,, Vieth has published from a large number of analyses of butters the following numbers :— Origin of Butter. Fat. Curd. Salt. Water. English . French „ salted . Kiel. Danish Swedish . Per cent. 86 ‘85 84-77 84- 34 85- 24 83-41 83-89 Per cent. 0-59 1-38 1-60 1-17 1-30 1-33 Per cent. 1-02 0-09 2-01 1-35 1- 87 2- 03 Per cent. 11- 54 13-76 12- 05 12- 24 13- 42 13-75 The curd and the water in butter render it liable to become easily rancid. This occurs, according to Stockmeyer , with special facility in the case of all butters containing more than 2 per cent of curd. Butter is therefore usually preserved by mixing with it a small quantity of salt. Ihe same object is accomplished by keeping butter in a melted state for some time until it has become quite clear, and separating it from the curd and water. 1 Pure butter fat consists chiefly of triglycerides of fatty acids ; it contains besides minute quantities of a colouring principle, lecithin, 2 cholesterol, phytosterol, and a lipochrome. The following acids have been identified hitherto: Acetic, butyric, caproic, caprylic , caprice lauric, myristic, palmitic, stearic, arachidic, and oleic. The quantity of stearic acid seems to be very small ( Hehner and Mitchell). IVachtel, and also Bondzynski and Rufi, state that also hydroxy acids occur in butter fat; but this stood greatly in need of confirmation. (The great discrepancy in the values found by these observers is explained by the writer’s comments on Benedikt’s acetyl values (cp. 165).) Experiments made by the writer (unpublished) prove that butter practically contains no hydroxy acids. Wanklyn, 3 has put forward the opinion that the solid fatty acids of butter fat consist chiefly of a hypothetical acid of the composition CicH^oOg, named by him aldepalmitic acid • this opinion is absolutely unsubstantiated by experiments, and need not be referred to further. 1 The flavour of butter suffers, however, considerably, according to Vieth , by this treatment. 2 According to Wrampelmeyer, the proportion of lecithin, calculated from the phosphoric acid found, is 0'017 per cent. Schmidt, however, gives the figures 0T5-0T7 per cent. 3 j our Qhevi. hid. 1891, 212. XI BUTTER FAT 605 The extraordinarily high proportion of glycerides of soluble fatty acids in butter fat—when contrasted with other fats—is characteristic; the chief components, however, appear to be, besides small quantities of stearin : palmitin and olein. Stearin and palmitin are often com¬ prised in the name “ margarin.” J. Bell 1 is of the opinion that butter fat most likely contains mixed glycerides, i.e. glycerides in the molecule of which the glycerol is combined with three different acid radicles, forming a tri-acid com¬ pound of the composition /0.C 4 H 7 0 C 3 H 5 (-o.c 16 h 31 o X 0. C 18 H 33 0 The following facts agree with this opinion : If ordinary animal fat is melted and mixed with—say 10 per cent of—butyrin, the latter compound may be entirely removed by digestion with alcohol, the animal fat being recovered practically in its original condition. If, on the contrary, butter fat is treated with hot alcohol, from 2 to 3 per cent only of its weight passes into the alcohol. The fat thus dis¬ solved does not consist, as might be supposed, of butyrin or caproin, but of a fat which is liquid at 15-5° C., and yields, on saponification, from 13 to 14 per cent of soluble fatty acids, and from 79 to 80 per cent of insoluble fatty acids. The latter have a higher melting point than the mixed insoluble acids obtained from the original butter fat; this tends to disprove the opinion that the low melting point of the extracted fat might be due to an increased proportion of oleic acid in its molecule. These results agree closely with a compound of the above-given formula, which Bell has named oleo-palmito-butyrate of glycerol. Bell’s theory is confirmed by the experiments of A. W. Blyth and Bobertson, 2 who state that they isolated from butter fat a crystalline glyceride, to which they ascribe the formula C 3 H 5 / 0. c 4 h 7 o \0. C 16 H 31 0 \0. c 18 h 36 o The fact that Hehner and Mitchell have found but small quantities of stearic acid agrees better with Bell’s formula. The proportion of the several fatty acids in a sample of butter fat examined by Bell is stated as follows :— Butyric acid .... 6T-3 per cent Caproic, caprylic, and capric acids 2-09 ,, ,, Palmitic, stearic, and myristic acids . 49-46 ,, ,, Oleic acid .... 36-10 ,, ,, Glycerol .... 12-54 „ „ 106-32 1 The Chemistry of Foods, ii. 44. 2 Jour. Chevu Soc. 1889, Proceed. 5. 606 GLYCERIDES—ANIMAL FATS CHAP. The fatty acid soluble in water at 15‘5° C. was considered to be butyric acid. The second group—caproic, caprylic, and capric acids —comprises the acids soluble in hot water ; their mean molecular weight was calculated as 136 from the analysis of their mixed barium salts. Oleic acid was regarded as the product obtained on decom¬ posing the ether soluble lead salts of the insoluble fatty acids ; the mixed palmitic, stearic, and myristic acids were estimated by difference. According to Duclaux, 1 butter fat contains from 2 to 2'26 per cent of caproic, and from 3 - 38 to 3’65 per cent of butyric acid. From the analyses of twenty-eight butter fats, Viollette, 2 somewhat arbitrarily, assumes the proportion in which butyric acid stands to caproic in butter fat to be 1-645. Thus he is enabled to calculate severally the proportions of butyric, caproic, solid volatile, and insoluble fatty acids by proceeding in the following way : 50 grms. of butter are saponified and the volatile acids removed, as in Reichert’s distillation process. The solid volatile acids are separated by filtration, and their quantity determined after drying; the amount of the fixed (insoluble) fatty acids is arrived at in the same way. The total quantity of the soluble acids is ascertained by titration with decinormal alkali, and calculated to butyric acid. If A represents this quantity of butyric acid, then the true quantities of butyric and caproic acids B and C are found with the help of the following equations :— B = Ax 0-68469 C = A x 0-41565 In the subjoined table Viollette’s results are reproduced :— Fatty Acids. Superior Qualities of Butter. Inferior Qualities of Butter. I. II. III. IV. V. VI. VII. VIII. Butyric acid. Caproic acid. Solid volatile acids Non-volatile acids Per cent. 6-07 3-66 2-85 82-28 Per cent. 5-33 3-23 3-00 82-63 Per cent. 5-50 3-34 2-80 82-87 Per cent. 5-05 3-06 3-00 83-20 Per cent. 4-62 2-80 2-90 84-32 Per cent. 4-80 2-92 2-40 84-31 Per cent. 476 2- 89 3- 00 83-83 Per cent. 4-37 2-65 2-95 84-62 Total 94-76 94-19 94-41 94-31 94-64 94-43 94-48 94-59 By ascertaining finally the mean molecular weights of the solid volatile and of the non-volatile acids, Viollette obtained all the data necessary for calculating the percentage composition of the butter fats. This is given in the following table :— Oompt. rend. 102. 1022. 2 Jour. Soc. Chem. Ind. 1890, 1157. XI BUTTER FAT 607 Glycerides. Superior Qualities of Butter. Inferior Qualities of Butter. I. II. III. IV. V. VI. VII. VIII. Per Per Per Per Per Per Per Per cent. cent. cent. cent. cent. cent. cent. cent. Butyrin 6-94 6-09 6-28 576 5-28 5-49 5-45 5-00 Caproin 4-06 3-58 370 3-39 3-09 3-23 3-10 2-94 Glycerides of solid vola- 3-06 3-22 2-96 3-16 3-06 2-53 3-16 3-15 tile acids . Glycerides of non-vola- 85-98 86-62 86-60 86-93 88-10 88-10 87-60 88-42 tile acids . Difference . 0-04 0-49 0-46 0-76 0-47 0-65 0-69 0-49 100 100 100 100 100 100 100 100 I subjoin a table showing the composition of butter fat as calculated by me from Bell’s results, and as given by the other chemists named:— Glycerides. J. Bell. W. Blyth. Spallanzani.1 Butyrin Caproin Caprylin and caprin . Olein .... Palmitin, stearin, etc.. Per cent. 7-012 | 2-280 37730 52-978 2 Per cent. 7-7 o-i 42-2 50-0 Per cent. 5-080 f 1-020 \ 0-307 j 93-593 100 100 100 The composition of a butter fat may be calculated approximately in the following manner :— Let the Hehner value be 87‘5, and the mean molecular weight of the insoluble fatty acids 270. The molecular weight of the corre¬ sponding glycerides would then be 3 x 270 + 38 = 848, containing 3 x 270 = 810 parts of fatty acids. Hence— 810 : 848 = 87'5 : x ; a: = 91-605 per cent. The proportion of mixed palmitin, stearin, and olein (including myristin and arachin) amounts therefore to 9L605 per cent. Fui'ther, let the iodine value of the butter fat be 31 - 0 ; the corre¬ sponding amount of olein calculated by the formula 0 = 1-16011 will then be 35 - 96. Assuming that the proportion of volatile acids make up the difference, the composition of the sample would be— 1 Le Staz. Sperim. Agr. Italian, vol. iv. 417. 2 By difference. 608 GLYCERIDES—ANIMAL FATS CHAP. Palmitin and stearin . Olein Butyrin, caproin, etc. . 55 '64 per cent 35-96 ,, ,, 8-40 ,, ,, 100 A further insight into the nature of the volatile acids may be gained from the Reichert-Meissl value. Let the mean Reichert-Meissl value of butter be 2878, or, in other words, the volatile acids obtained from 5 grms. of butter fat are neutralised by 2878 c.c. of decinormal potash. The volatile acids from 100 grms. would then require 57'56 c.c. of normal potash. Since 3 x 567 grms. of KOH correspond to 92 parts of glycerol, C 3 H 8 0 3 , or 38 parts of C 3 H.„ the alkali used will correspond to ■38x57-56x^7 3x^7 = 0-729 C 3 H 2 . On subtracting the last number from 870 (the amount found above for the glycerides of the volatile acids), we obtain 7 - 673 as the percentage of volatile acids in the sample. These 7'673 grms. volatile acids require, as found by titration, 57‘56 c.c. of normal potash, hence their mean molecular weight— M= 7-673 x 1000 57-56 = 133-3. According to theory we have the following molecular weights :_ Acid. Formula. Molecular Weight. Butyric . c 4 h 8 0 2 88 Caproic . c 6 h 12 o 2 116 Caprylic . C 8 H 16 Oo 144 Capric c 10 h 20 o 2 172 We may therefore safely conclude that W. Blyth’s numbers for butyrin on the one hand, and for caproin, caprylin, and caprin, on the other hand, require a correction, allowing a larger proportion for the latter glycerides. Butter fat contains even in the fresh state small quantities of free fatty acids (cp. below, “Determination of Free Fatty Acids ”). The microscopic appearance of fresh butter shows that it consists of a mass of transparent minute globules of fat, each being distinct. In stale butter, however, crystals have been found by Hasscd / therefore the presence of crystals cannot be adduced as a proof of adulteration with other fats, as has been asserted by several chemists. The crystals are best observed, according to Mylius, 1 under the polarisation-micro- 1 Berichte, 1879, 270. XI BUTTER 609 scope with crossed nicols, the crystals alone appearing illuminated in the otherwise dark field. On exposure to air, especially to sunlight, butter loses its yellow colour, whilst acquiring the colour and also the odour of tallow. According to Duclaux, the weight of butter increases thereby, reaching an increment of 1*3 per cent. 1 Melted butter fat does not solidify homogeneously throughout its mass, a kind of crystallisation being noticeable. The portions adhering to the sides of the containing vessel, and consequently solidifying first, have a composition somewhat different from that of the innermost portions, which remain liquid for a longer period. In the case of melted butter fat the solidification takes place with separation of an oil, “butter oil.” The latter may also be prepared by melting butter, allowing to cool to 20° C., and subjecting it to pressure. According to Blyth and Robertson , butter fat consists of 45'5 per cent of butter oil and 54-5 per cent of solid fat. Adulteration of Butter The substances that are fraudulently admixed with butter are of various kinds. Gross adulterants, easily detected, however, are the following : starch, potato pulp, ground white cheese, a.o. Also borax, 2 alum, sodium silicate have been discovered in butter, added with the view of preserving it, and of allowing at the same time the fraudulent incor¬ poration of large quantities of water. Other sophistications may be looked for in the form of colouring matters, such as annatto, curcuma, saffron, azo-colours, etc. The most important and most common adulteration of butter however, is the admixture of foreign animal or vegetable fats, as lard, tallow, goose fat, cotton seed stearine, cocoa nut and palm nut oils, and, most of all, “ margarine ” or “ oleomargarine.” The frauds are being perpetrated on such extensive lines that legislation has stepped in to protect the genuine article. In this country no butter-substitute, however small the proportion of foreign fat, may be sold without bearing a distinct acknowledgment as to its true nature. 3 846. On the change in the composition of butter on long keeping, cp. Ghent. Zeit. 1895, 2 In Italy the addition of 2 grms. of borax per 1000 grms. of butter is allowed. 3 In Germany, Soxhlet has proposed the enactment of a law, that to every hundred¬ weight of a butter-substitute 0'5 grm. of phenolphthalein must be added, so as to make the detection of any admixture with genuine butter an easy operation. F. Hart, how¬ ever, has shown ( Ghem. Zeit. 1893, 1908) that phenolphthalein acts injuriously on the organism. Later on it was proposed that “margarine” be mixed with a “latent” colouring matter, viz. dimethylamidoazobenzene, so that detection of margarine or of butter adulterated with margarine should be within the reach of everybody, by testing it with dilute acid, when margarine or butter adulterated with margarine would turn red. According to the latest German Margarine Act the manufacturer of margarine is bound to admix with the fats and oils employed 10 per cent of sesame oil, the recognition of which is easy by the Baudouin colour reaction (p. 390). 610 GLYCERIDES—ANIMAL FATS CHAP. Whereas gross adulteration with substances of a non-fatty nature are easily recognised, the detection of foreign fats has caused great difficulty for a long time, until we got the excellent methods of Kottstorfer, Hehner, and Reichert. Unfortunately the adulterator has kept pace with the progress of analytical methods, and has succeeded with great ingenuity in pre¬ paring mixtures that possess the same saponification and Hehner values as genuine butter. Thus a judiciously prepared mixture of oleomargarine and cocoa nut oil could not be recognised as an artificial article if subjected to the first two tests only. The Reichert value, however, affords a very valuable means of detecting adulteration of this kind, but it should be borne in mind that an admixture of 10 per cent of “margarine” cannot be revealed with certainty. 1 The fear which the writer expressed in the first edition of this work that the artificial butter industry may succeed in providing means to prepare butter-substitutes having a correct Reichert value has been realised, since butyric acid, tributyrin, and also amyl acetate are being sold (in 40 per cent alcoholic solution) for that purpose. In order to pronounce on the genuineness of a sample of butter it will therefore be required to determine the Reichert value in the first instance, and then the saponification value and specific gravity. On account of its rapidity optical analysis will serve as a sorting test. These will as a rule suffice, and other tests are therefore rarely applied. The literature bearing on the examination of butter is an extra¬ ordinarily voluminous one, and still grows. The list of methods detailed below cannot therefore lay claim to completeness, although no important and really valuable method will be found missing. A large number of insignificant modifications of known methods and a host of valueless proposals have been deliberately omitted. For further information reference must be made to special works on butter. 2 The examination of butter divides itself naturally into two parts : the first embraces the estimation of not-fats (water, curd, etc.); the second deals with the examination of the butter fat itself. 1. Examination of Butter 1. Water is determined by drying the sample at 100°-120° C. The Society of Bavarian Analytical Chemists recommends drying the butter at a 100° C. for six hours, with occasional stirring (cp. also p. 88). 3 1 I wish to lay stress on this point, as many chemists who propose new methods entirely overlook the fact that it does not involve the slightest difficulty to distinguish pure butter from “ margarine,” or, in short, from any other fat. 2 Sell, Arbeiten aus dern Kaiserl. Reichsgesundheitamt, 1886 ; Duclos, Le Bait, fitude chirnique et microbiologique, Paris, 1887 ; Girard and Bevans, La Margarine,, Paris, 1888 ; Besana, Sui Metodi a distinguere il burro artijiciale dal burro naturale, Lodi,’l888 ;’zune, Traite general d’analyse des beurres, 2 vols., Paris et Bruxelles, 1892. s’ For Crismer’s method of determining the amount of water by the critical tempera¬ ture the reader is referred to the Bullet, de l’Assoc. Beige des Chim. 1896 (9), 359 ; Analyst, 1896, 241. XI BUTTER 611 In cases where scientific accuracy is not the chief object, as for market control and police regulation purposes, the amount of water may be determined rapidly by Birnbaum’s method as modified by iFimmel 1 in the following manner: 10 grms. of butter are shaken up with 30 c.c. of ether, saturated with water, in a tube corked at one end and provided with a stop-cock at the other, through which the separated aqueous liquid is run off into a second narrow gradu¬ ated tube, containing 5 c.c. of saturated brine and a minute quantity of acetic acid, so as to produce a distinct red colour with litmus. The increase of volume, due to the water in the butter, is then read off. The results are stated to be but slightly below those obtained by gravimetric analysis. The proportion of water in a butter should not exceed 16 per cent. J. Bell has found in the analysis of 113 genuine English butters values varying from the minimum of 4T5 to the maximum of 20 - 75 per cent, the majority of samples, however, containing from 11-14 per cent. The following table gives a few values culled from analyses by Vietli and H. D. Richmond , 2 and arranged by the writer according to their amount of water :— Kind of Butter. Number of Samples examined. Samples containing per cent of Water. Observer. From 11-14. From 10-15. Above 16. Per cent. Per cent. Per cent. English and foreign 560 83-8 94'2 0-9 Vieth English . . 143 70 7 85-4 0-7 H. D. Richmond Foreign . . 417 88-3 97-2 1-0 French . . 451 8-6 J > 48 o-o : > 2. Solids not-fat are best determined in the sample of butter previously employed for the estimation of water, by exhausting the dried butter with ether, chloroform, carbon bisulphide, or petroleum ether, and weighing the residue after drying. If a fresh quantity of butter be taken for this assay errors may easily arise from the fact that butter is not a homogeneous product, different parts containing varying amounts of butter milk. Sjoaeth 3 has shown that errors due to this cause may amount to several per cents. For the convenient estimation of water and solids not-fat he recommends the drying of the accurately weighed sample in a glass trough, filled one-third with fragments of pumice, and placed inside a weighing bottle, the lid and bottom of which are perforated with holes. After drying, the weighing bottle and contents are transferred to a Soxhlet extractor. The residue left in the glass trough is then dried and weighed. 1 Jour. Soc. Chem. Ind. 1893, 630. 2 Analyst, 1894, 17. 3 Zeitsch. angew. Chem , 1893, 513. 612 GLYCERIDES—ANIMAL FATS CHAP. In the case of pure butter the solids not-fat consist of casein, milk- sugar, and inorganic salts. By exhausting the dried residue with water, to which a trace of acetic acid has been added, milk-sugar and the bulk of the inorganic salts are removed, leaving casein behind; its weight is ascertained after drying. The minute quantity of salts retained in the casein and found on incineration is deducted. Koenig suggests to determine the proportion of nitrogen by Kjehldahl’s process and multiplying by 6‘25. The percentages of casein (curd) recorded by Koenig for 302 samples of butter vary from 0T9 to 4 - 78 per cent. The amount of inorganic salts, chiefly common salt, is found by igniting the ether-insoluble residue from 10 grms. of butter, taking care, however, not to heat the ash to too high a temperature lest sodium chloride should volatilise. The proportion of the latter is determined by titration with standard silver solution, using potassium chromate as an indicator. With greater accuracy, however, sodium chloride is determined by warming in a porcelain dish 10 grms. of butter with an equal amount of stearic acid and 50 c.c. of water, acidulated with a few drops of nitric acid, and stirring the melted mass. After cooling, the cake is taken off, rinsed well, the aqueous liquid filtered, and the chloride precipitated as silver chloride. The proportion of sodium chloride in the 113 samples examined by J. Bell was found lying between 04 and 9-20, the majority yielding from 2 to 7 per cent, in one case only 15-08 percent. The amount of salt added to butter varies, of course, in different countries and localities. An excessive amount of ash will naturally invite further examination. Milk-sugar is not determined direct, but found by difference. The proportion of fat is likewise found by difference ; it can, of course, be determined direct by evaporating the ether-extract and weighing the residue (p. 90). Fraudulently added substances of a non-fatty nature, as starch, etc., are detected as described page 88. 3. Colouring Matters.— Summer butter is yellow, winter butter is almost white 1 ; the latter is therefore, as a rule, coloured artificially before being placed on the market. The naturally yellow butter is rapidly bleached when exposed to light and air. Experiments by Soxhlet have demonstrated the fact that a layer of butter | cm. thick loses its colour in sunlight within eight hours. The butter thus becomes white, and resembles tallow in appearance. Foreign colouring matters are detected by shaking the melted 1 In this connection it may be interesting to note that in some Swiss farms having an abundant growth of Leontodon and Ranunculus , the cows gave butter of such intense yellow colour that suspicion was aroused ; the butter obtained after the second grazing was very much paler. XI BUTTER 613 butter with alcohol. In presence of foreign colouring matters the alcoholic layer becomes tinted, whereas natural butter leaves the alcohol colourless. Moore 1 and Martin 2 recommend the use of a mixture of alcohol and carbon bisulphide. According to Martin, 5 grms. of butter are shaken up with 25 c.c. of a mixture consisting of 15 parts of methyl alcohol, or ordinary alcohol, and 2 parts of carbon bisulphide. Two layers are formed, the lower one consisting of the fat dissolved in carbon bisulphide, the upper alcoholic layer containing the colouring matter. Stebbins, 3 however, has pointed out that the small quantity of fat retained by the alcoholic layer may interfere with the subsequent examination, and that carrotin, the colouring matter from carrot juice, is more easily soluble in carbon bisulphide than in alcohol. He substitutes, therefore, the following process: Melt 50 grms. of the sample in a narrow beaker on the water-bath, stir into the melted mass 5 to 10 grms. of finely-powdered fuller’s earth, agitate thoroughly for two or three minutes, and allow to settle out completely whilst warm. Drain off the bulk of the fat, add 20 c.c. of benzene, stir well, allow to deposit, and decant the solution through a filter. Repeat this process until the fat is removed entirely, and wash the precipitate on the filter with benzene. Test the filtrates for carrotin. Dry the precipitate on the water-bath, and boil out three times with about 20 c.c. of 94 per cent alcohol. Evaporate the alcoholic extracts in a tared dish, dry at 100 u C., and weigh the residue. The residue obtained by the one or the other method is then examined by means of special reactions for the colouring matter present. In the Paris Municipal Laboratory curcuma, annatto, and saffron are tested for in the manner described below. The first two colour¬ ing matters are at present chiefly used in France. A preparation for colouring butter is sold there under the name of “ jaune gras ” (fat yellow), made by digesting annatto with sesame oil. With a view" of imparting to it an orange-yellow or straw-yellow hue curcuma is added. Five drops of the filtered mixture are said to suffice for one kilo of butter. Curcuma is indicated by the appearance of a brownish yellow coloration on adding a few drops of ammonia, and a reddish brown coloration on adding hydrochloric acid. Annatto is identified by a reddish brown residue, dissolving in concentrated sulphuric acid with production of a blue colour. In the presence of saffron an orange-coloured precipitate is obtained on dropping lead acetate into the aqueous solution of the residue. • Leeds 4 dissolves 100 grms. of butter in 300 c.c. of pure petroleum ether of 0’638 specific gravity in a separating funnel, draws off the curd 2 Ibid. 12. 70. 4 Analyst , 1887, 150. 1 Analyst, 11. 163. 3 Jmr. Amer. Chem. Soc. 1887, 41. 614 GLYCERIDES—ANIMAL FATS CHAP. and water, and washes several times with water, using about 100 c.c. The solution of butter fat is then kept at 0° C. for about twelve to fifteen hours, when the bulk of the solid glycerides will crystallise out. The liquid fat is poured off and shaken with 50 c.c. of decinormal alkali, whereby the colouring matters are removed from the ethereal solution. The aqueous layer is drawn off and very carefully neutral¬ ised with hydrochloric acid, until just acid to litmus. The colouring matters, containing a minute quantity of fatty acids, are thus pre¬ cipitated ; the precipitate is transferred to a tared filter, washed with cold water, dried, and weighed. For the discrimination of the several colouring matters the precipitate is dissolved in alcohol, and two or three drops of the solution tested with an equal quantity of the reagents as given in the following table :— [Table XI BUTTER 615 Reactions of Colouring Matters Colouring Matters. Concentrated h 2 so 4 Concentrated hno 3 H 2 S0 4 +HN0 3 Concentrated HC1. Annatto indigo blue, changing to violet Blue, becoming colourless on standing Sam* No change, or only slight dirty yellow and brown Annatto+ decolourised butter Blue, becoming green, and slowly changing to violet Blue, then green and bleached Decolourised No change, or only slight dirty yellow Turmeric 1 Pure violet Violet Violet Violet, changing to original colour on evaporation of HC1 Turmeric+ decolourised butter Violet to purple Violet to reddish violet Same Very fine violet Saffron. Violet to cobalt blue, changing to reddish brown Light blue, changing to light reddish brown Same Yellow, changing to dirty yellow Saffron+ decolourised butter. Dark blue, changing quickly to reddish brown Blue, through green to brown Blue, quickly changing to purple Yellow, becoming dirty yellow Carrot. Umber brown Decolourised Do. with NOo fumes and odour of burnt sugar No change Carrot+ decolourised butter Reddish brown to purple, similar to turmeric Yellow, and decolourised Same Slightly brown Marigold Dark olive green, permanent Blue, changing instantly to dirty yellow green Green Green to yellowish green Safflower Light brown Partially decolourised Decolourised No change Aniline yellow Yellow Yellow Yellow Yellow Martius yellow Pale yellow Yellow, reddish precipitate. Magenta at margin Yellow Yellow, precipitate treated with NH 3 and ignited deflagrates Victoria yellow Partially decolour¬ ised Same Same Same, colour returns on neu¬ tralising with nh 3 According to Lejfmann , 2 methylorange is extensively used in the U.S.A., especially for oleomargarine. The colouring matter is ex- 1 Ammonia gave with turmeric reddish brown, returning to original colour on driving off NH 3 . 2 Second annual report of the Dairy and Food Commissioner of Pennsylvania. 616 GLYCERIDES—ANIMAL FATS CHAP. tracted as described above and tested with dilute acid, when the well-known red tint will appear. Butter colours are similarly treated, using, of course, smaller quantities of the samples. About 5 grms. are dissolved in 20-25 c.c. petroleum ether, and treated with 10 c.c. of a 4 per cent solution of potash. 1 4. Preservatives. — Borax will have been discovered by examining the ether-insoluble portion (see p. 89). Salicylic acid is sometimes used to preserve butter. 2 According to the directions of the Paris Municipal Laboratory it is detected by repeatedly exhausting 20 grms. of butter with a solution of sodium bicarbonate, whereby the acid is converted into easily soluble sodium salicylate. The aqueous liquid is acidulated with dilute sulphuric acid, extracted with ether and a little mercurous nitrate added to the residue left after evaporating off the ether, when a precipitate, nearly insoluble in water, is obtained. This is filtered off, washed and decomposed by dilute sulphuric acid, free salicylic acid resulting again. It is redissolved in ether, the solvent evaporated off, and the residue warmed to 80°-100° C., until nearly dry. In order to remove any other acid present, the residue is extracted with neutralised petroleum ether, the ethereal liquid diluted with an equal volume of 95 per cent alcohol, and titrated with decinormal alkali, using phenol- phthalein as an indicator. 1 c.c. of decinormal alkali corresponds to 0-0138 grm. of salicylic acid. For further identification the salicylic acid may be liberated again by a corresponding amount of standardised hydrochloric acid and tested with a drop of very dilute iron perchloride solution, when a violet coloration should be obtained. Formalin (formaldehyde) is best detected by Hehner’s method in the form given it by Richmond and Boseley: 3 Add to the aqueous liquor obtained when butter is melted a drop of milk, and pour the mixture carefully on the surface of concentrated sulphuric acid con¬ tained in a test-tube. In the presence of formalin a blue ring will appear at the zone of contact of the two liquids. A trace of ferric chloride renders the reaction far more distinct. 2. Examination of Butter Fat Free Fatty Acids. —Fresh butter contains a small quantity of free fatty (butyric) acid; according to Duclaux , from 0-005 to 0-0100 1 The following formula for butter colours have been taken by Leffmann from a Druggists’ Circular :— Extract of Annatto 10 ounces. Annatto seed, bruised 10 parts. Turmeric Logwood chips Cotton seed oil Turmeric . 3 • -i >! . 1 gallon Ammonium carbonate 1 Cotton seed oil . .75 Cotton seed oil . Lard . . 10 3 Analyst, 1895, 155 ; 1896, 92, 94, 157. 2 Jour. Soc. Chem. Ind. 1887, 670. XI BUTTER FAT 617 grm. per 1000 grms. The quantity of free acids, however, increases rapidly on keeping, due perhaps to the action of microbes on the nitrogenous matter of the butter. 1 The butter becomes thereby “ rancid.” Butter fat, however, offering no suitable nourishment to microbes, does not decompose so rapidly, although formation of free fatty acids gradually sets in. Butter containing as little as 0‘02 to 0'03 grm. of free fatty acids per 1000 grms. has a “rancid” taste; in the case of old butter the free acids may amount to T5 grms. Butter can therefore be examined for its state of freshness by titrating the amount of free fatty acids. The acidity may be expressed by its acid value (p. 148), or in terms of oleic acid, or, as is usually done in Germany, by “ degrees of acidity,” i.e. the number of c.c. of normal alkali required for 100 grms. The table given page 150 affords an easy comparison between the various modes of expressing the results of titration. The “ rancidity ” of butter is, however, not necessarily in propor¬ tion to the amount of free fatty acids, rancidity not being synonymous with acidity (cp. chap. i. p. 11). It is usually assumed that, on butter becoming rancid, the gly¬ cerides of the volatile fatty acids are split up first, decomposition gradually proceeding to the higher glycerides. Bondzynski and Rufi 2 are of the opinion that the rancidity of old butter is due to a high pro¬ portion of free insoluble acids, and not to the soluble or volatile acids. The method, however, they employed (p. 196) being open to objec¬ tions, their opinion must be accepted with due reserve, all the more as it is in conflict with the well-established fact that marked rancidity is a safe indication of genuine butter as opposed to old artificial butter (which is, of course, free from glycerides of volatile acids). Neverthe¬ less, Spaeth’s experiments on lard would seem to lend support to their statement. TESTS FOR FOREIGN FATS Preliminary Tests A reliable preliminary test for the discrimination of margarine from genuine butter is, according to Hehnerf to heat the fat with a quantity of alcoholic potash insufficient for complete saponification. The formation of etlujl butyrate, easily recognised by its pleasant smell (recalling that of pine-apples), will indicate the presence of butter. 1 The following notes, taken from the opening address of Prof. H. M. Ward at the Toronto Meeting of the Brit. Assoc. 1897, may be of interest“ Some years ago Storch found that the peculiar aroma of a good butter was due to a bacterium which he isolated, and Wiegmann has now two forms, or races, one of which develops an exquisite flavour and aroma, but the butter keeps badly, while the other develops less aroma, while the butter keeps better. According to Conn’s publication, this subject has been advanced considerably in America, for they have isolated and distributed to numerous dairies pure cultures of a particular butter-bacillus which develops the famous ‘June flavour ’ hitherto only met with in the butter of certain districts during a short season of the year.” 2 Jour. Soc. Chem. Ind. 1890, 422. 3 Analyst, 1884, 76. 618 GLYCERIDES—ANIMAL FATS CHAP. A number of margarines examined by the writer failed to give the odour of the butyrate; this appeared, however, on adding a small quantity of genuine butter. A large number of tests, based on the behaviour with solvents, have been proposed for the same pui’pose. They should, however, not be solely relied upon; at best they can only point to possible adulteration with another fat. Thus Hoorn 1 dissolves 1 grm. of the sample to be tested in 7 c.c. of petroleum ether, and allows it to stand in a closely-corked bottle at 10°-15° C. for several hours. Pure butter fat remains dis¬ solved, whereas tallow and lard are said to separate out. Miinzel 2 dissolves 1 grm. of the sample in 12*5 c.c. of absolute alcohol (spec. grav. 0‘797) in a test-tube by warming on the water-bath, and then closes it with a tightly-fitting cork provided with a thermo¬ meter reaching into the liquid. The contents of the test-tube are then allowed to cool, and the temperature is noted at which solidification takes place. The following observations are recorded by Miinzel :— Temperature at which Solidification sets in. Genuine butter °C. 34 9 9 99 +10 per cent of horse fat 37 9 9 9 9 + 20 9 9 9 9 40 9 9 9 9 + 30 9 9 9 9 44 9 9 9 9 + 10 tallow 40 „ ,, + 20 „ 9 9 • 43 9 9 9 9 + 30 9 9 46 9 9 99 + 10 lard 38 99 9 9 + 20 „ ,, 41 9 9 9 9 + 30 9 9 43 Margarine 56 Genuine butter + 25 per cent of oleomargarine 40 99 99 + 50 9 9 48 Horsely, Ballard , Husson, and Filsinger have tried to make use of the different solubilities of butter and butter-substitutes in ether or in ether-alcohol. E. Scheffer 2, employs for the same purpose a mixture of forty parts (by volume) of rectified fusel-oil and sixty parts (by volume) of ether of specific gravity 0‘725. The different solubilities of the fatty acids in alcohol and benzene suggest another analytical method (cp. Dubois and Fadd, p. 328). According to BocJcairy , 4 foreign fat in butter may be detected by the following method: 15 c.c. of the filtered fat are dissolved, in a graduated cylinder, in 15 c.c. of toluene, and 40 c.c. of alcohol of 96’7° Gay-Lussac are added. The mixture is warmed to 50° C. and agitated, when a butter substitute will give a turbidity, whereas butter, even when containing a little foreign fat, yields a clear solu¬ tion. When kept for thirty minutes at a temperature of 40° C., the 1 Zeitsch. analyt. Chem. 1872, 334. 2 Ibid. 1882, 436. 3 Jour. Soc. Chem. 1887, 148. XI BUTTER FAT 619 solution will be clear or only slightly turbid in the case of pure butter, whereas adulterated butter will cause at first turbidity and then separa¬ tion of an oily liquid. If the latter exceeds 3 c.c. the butter must be considered adulterated. Violette considers this process unreliable. Valenta’s test—behaviour with glacial acetic acid—has been em¬ ployed by Allen 1 for the examination of butter in the following manner: 3 c.c. of the melted fat are poured into a small test-tube, an exactly equal measure of glacial acetic acid is added, and the contents of the tube heated until complete solution takes place on agitation. The liquid is then allowed to cool spontaneously whilst stirred with a thermometer, and the temperature observed at which it becomes turbid. The turbidity temperatures for genuine butter were found from 56°-6T5° C., whereas those for “butterine” were 98°-100° C. Jean does not regard the turbidity as a criterion, but estimates the volume of acetic acid dissolved by the fat. For his method compare p. 273. I subjoin some of his results in the following table :— Acetic Acid dissolved. Fat - Per cent. Pure butter ..... 63 '33 2 ,, ,, with 10 per cent of cocoa nut oil . 66‘66 „ ,, ,, 15 „ „ „ • 90 „ „ „ 28 „ „ „ . 96 Carbolic acid , recommended first by Crook , 3 has been found suitable by Lenz, although his results do not completely agree with those stated by Crook. The test is made as follows : Melt O'648 grm. (10 grains) of the filtered fat in a graduated test-tube in a water-bath at a temperature of about 66° C., and agitate with T5 c.c. of liquid carbolic acid—prepared from 373 grms. of crystallised phenol and 56'7 grms. of water. Keep the mixture in the warm water until it has become transparent, and allow to stand for some time at the ordinary temperature. In the case of genuine butter a clear solution results, whereas in the presence of foreign fats, such as tallow or lard, two layers, separated by a well-defined border line, will be noticed. The following table gives the results obtained by Crook and Lenz :— Fat. Volume of the Lower Layer in per cents. Crook. Lenz. Beef tallow .... 49'7 Mutton tallow 44'0 39'1 Lard ..... 49'6 37'0 1 Commerc. Org. Analys. ii. 154. 2 Cp. also footnote p. 273. 3 Zeitsch. analyt. Chem. 19, 369. 620 GLYCERIDES—ANIMAL FATS CHAP. After somewhat prolonged cooling crystals are distinctly notice¬ able in the upper layer. According to Lenz, no separation into two layers takes place in the case of genuine butter mixed with 5 per¬ cent of lard ; after twenty-four hours, however, crystalline deposits appear, differing, though, from those yielded by genuine butter under the same conditions. Recently cumene has been suggested by ErdSlyi 1 for the detection of foreign fats. A solution of pure butter in cumene, when cooled to 0° C., remains perfectly clear for at least one hour—in most cases very much longer—whilst in presence of foreign fats a more or less pronounced turbidity is developed after 1-1 \ hours’ standing. The details given by the author, however, are, in the writer’s opinion, not such as to recommend the method as a reliable one. Physical Methods (a) Specific Gravity It has been pointed out already that, as a rule, the determination of the specific gravity, in conjunction with that of the Reichert and of the saponification values, furnish sufficient evidence of the purity or otherwise of a butter fat. The specific gravity of butter fat is higher than that of the majority of fats that might come within the scope of the adulterator. The determination of the specific gravity at the ordinary tem¬ perature, recommended by A. TV. Blyth 2 and Casamajor , 3 has been almost abandoned, and, as a rule, temperatures are preferred at which the butter fat is in a melted state. The methods that are employed have been fully explained, pages 123 et seq. The specific gravity is a very valuable criterion, for the reason that it is almost constant for genuine butters. Small deviations from the normal values appear, according to Adolf Mayer, to follow the rule that a high Reichert value conditions a high specific gravity. J. Bell, who first proposed the specific gravity as a critical test, chose the temperature of 100° F. = 37'8° C. The apparatus used was an ordinary pear-shaped specific gravity bottle. In the examina¬ tion of the large number of samples, reference to which has been made repeatedly, he has found that the experimental values vary within the very narrow limits of 0 - 911 and 0 - 913. The correspond¬ ing values obtained for other fats are recorded in the subjoined table:— 1 Jour. Soc. Chem. Ind. 1893, 184. 2 Analyst, 1880, 76. 3 Chem. Centralblatt, 1882, 252. XI BUTTER FAT 621 Kind of Fat. Genuine butter fat (113 samples) Mutton suet Beef suet Fine lard Oleomargarine . > J Specific Gravity at 100° F. = 37'8° C. J. Bell. . 0-911-0-913 0-90283 0-90372 0-90384 0-90384 0-90234 0-90315 0-90379 0-90136 Due regard, however, must be had to the fact that cocoa nut and palm nut oils, if present, could not be thus detected. Moore has pointed out that owing to the somewhat higher specific gravity of cocoa nut oil—0"9167 at 37"8 C.—a judiciously prepared mixture of the same with oleomargarine might be incorporated with butter without being detected by an abnormal number for the density. This qualifies Viollette’s 1 statement that by means of a density deter¬ mination alone butters may be rapidly sorted into three classes, viz. those undoubtedly adulterated with margarine, those doubtful, and those that may be considered practically pure. The same holds good of other vegetable oils, such as arachis, sesame , and poppy seed oils. Skalweit, having found that the differences in the specific gravities of butter and fats likely to be used as adulterants are greatest at 35 C., prefers this temperature. His observations are given in the following table :— Specific Gravities Temperature. °C. 35 50 60 70 80 90 100 Lard. 0-9019 0-8923 0-8859 0-8795 0-8731 0-8668 0-8605 Margarine. “Butterine.” Butter Fat. 0-9017 0-9019 0-9121 0-8921 0-8923 0-9017 0-8857 0-8858 0-8948 0-8793 0-8793 0-8879 0-8729 0-8728 0-8810 0-8665 0-8663 0-8741 0-8601 0-8598 0-8672 Other chemists, notably Koenigs, have taken the specific gravity at 100° C. (water of 15° C. = 1); the results recorded by the different observers agree in a satisfactory manner :— 1 Jour. Soc. Chem. Tnd. 1894, 54. 622 GLYCERIDES—ANIMAL FATS CHAP. Specific Gravities at 100° C., Water at 15° C. = 1 Fat. Koenigs. Sell. Allen. Genuine butter.... 0-866-0-868 0-866-0-868 At 99° C., water 15-5=1. 0-867-0-870 Beef tallow .... Lard ..... Oleomargarine .... 0-859-0-865 0-859-0-8605 0-860-0-8605 0-859-0-860 0-8585-0-8625 Adulterated butter . 3 parts of genuine, 1 part of artificial butter 1 part of genuine, 1 part of artificial butter 0-865 0-863-0-864 The lower limit for the specific gravity of pure butter fat should therefore be 0-866 at 100° C., compared with water of 15° C. The specific gravities at 100° C., referring to water of 100° C. as unit, are tabulated here— Specific Gravities at 100° C., Water at 100° C. = 1 Fat. J. Bell. Muter. Allen. Genuine butter fat 0-9094-0-9140 0-9105-0-9138 0-9099-0-9132 Oleomargarine . 0-4014-0-9038 0-903-0-906 0-902-0-905 Viollette 1 being of the opinion that, by means of density deter¬ mination alone, butters may be rapidly sorted into (a) undoubtedly adulterated, ( b ) doubtful, (c) practically pure butters, proposes to determine the weight in vacuo of 1 c.c., measured at 100 C. He has found that— At 100° C. weighs in vacuo. 1 c.c. of Grins. Genuine butter .... 0-86328-0 '86425 Margarine • • • • 0 "85766-0‘85865 Aclolf Mayer has drawn attention to the necessity of taking the barometric pressure into account, when hydrometers are used at 100° C. (cp. p. 127), the specific gravity differing by 0-0001 for a variation of 2 mm. in the pressure. Therefore for a difference of 40 mm. in the atmospheric pressure, which occurs frequently, a correc¬ tion of 0-002 would have to be made, which is not to be neglected, considering that the difference between genuine and artificial butter amounted to only 0-007 in his method. 1 Jour. Soc. Chem. Ind. 1894, 54. XI BUTTER FAT 623 Instead of determining the specific gravity by weighing a definite 171 volume, according to the formula d — y (where m denotes the weight, V the volume, and d the density), Zaloziecki proposes to measure the volume of the fatty acids derived from a known weight of butter. Evidently this is no new constant, as, from the formula given, it m follows that V = ^-, and no further information is gained than that afforded by the specific gravity number of the fat. The volume of the fatty acids is referred to the weight of fat, and it becomes there¬ fore simply a question whether the method proposed by Zaloziecki is more expeditious than the simple weighing of the original fat in a picnometer. There can be no doubt that Zaloziecki’s method is more cumbersome, and for this reason, and for the more cogent one that a serious source of error is introduced by the solubility of the volatile fatty acid, the method cannot be recommended. For further informa¬ tion as to the details of the method the reader is referred to the original paper, 1 the results only being given here:— Fat. Volume of Fatty Acids from 10 grms. of Fat at 80° C. c.c. Best butter A 10-70-10-75 „ „ B 10-80-10-80 Commercial butter A 10-85 „ „ B 10-80 Rancid butter .... 10-95 Cocoa nut oil ... 10-90-10-95 Beef tallow old .... 11-70 ,, ,, fresh .... 11-50 Mutton tallow .... 11-60 Lard ..... 11-50 Margarine ..... 11-60 Oleomargarine .... 11-35 Olive oil 11-25 (b) Refractometric Examination The refractometric examination proposed at first by Alexander Muller and Skalweit has received powerful assistance by the construc¬ tion of special apparatus, viz. Amagat and Jean’s oleo-refractometer and Zeiss’s butyro-refractometer. We shall consider here only the two last-mentioned apparatuses, Abbe’s refractometer, which has been made use of by Skalweit , having been superseded by them (for butter analysis at any rate) on account of their handiness and rapidity in the manipulation entailed. Thoerner’s observations obtained with Pulfrich’s refractometer have been given above (p. 263). 1 Chevi. Revue, 1897, 119. 624 GLYCERIDES—ANIMAL FATS CHAP. For the examination in the oleo-refractometer (description of the instrument p. 119) the sample is prepared, according [to Jean, 1 in the following manner : Melt from 25 to 30 grms. of butter in a porce¬ lain dish at a temperature not exceeding 50° C., stir well with a pinch or two of gypsum, and allow to settle out at about the same temperature. Then decant the supernatant fat through a hot water funnel plugged with cotton wool, and pour it whilst warm into the prism of the apparatus. Stir with the thermometer until the fat has cooled to 45° 0., and observe the deviation. [Ether must not be used for the preparation of the butter fat, as minute traces of the solvent, which is very difficult to get rid of entirely, seriously influence the result.] Genuine butter gives a deviation of 30° to the left. A large number of French and Belgian pure butters showed deviations from - 29° to - 31°. Pearmain 2 finds for 15 samples the maximum - 34 and the minimum - 25. For the sake of comparison we add some observations made by Jean and Pearmain on other fats (cp. also p. 264). No. Kind of Fat. Degrees. Observer. 1 Margarine (Mouries) -14 Jean 2 “ Creme Mouries ” .... -15 7> 3 Oleomargarine .... -17 > 5 4 Pure butter with 10 % ol No. 3 -28 5 „ „ 20% „ -26 > > 6 „ „ 30% „ -25 ,, 7 „ „ 50% „ -23 J > 8 Cotton stearine .... -20 77 9 “ Yegetaline ” (cocoa nut butter) . -59 ,, 10 Margarine ..... -13 to -18 Pearmain 11 Lard ...... - 8 to - 14 ? > 12 Tallow . -15 to -18 ? > Admixtures of vegetable oils are recognised more easily still, yielding as they do a marked deviation to the right. The value of the refractometric method is demonstrated by Jean by the following example :—A pure butter giving a deviation of - 30° showed, after having had admixed 5 per cent of arachis or linseed oil, - 20° only, thus distinctly indicating an adulteration, whereas, if Peichert’s process be resorted to, adulteration could not be pronounced upon with certainty. Lobry de Bruyn, however, has shown that in the case of Dutch butters deviations from - 25° to - 30° are frequently met with, and that even deviations of 21-26 were observed in the case of butters having the normal amount of volatile fatty acids and possessing good taste. 3 This serious objection to the employment of the oleo-refracto- meter has to some extent been deprived of its force by Jean’s explanation 1 Jean, Chimie analytique des matieres grasses, Paris, 1892, p. 465. 2 Analyst, 1895, 135. 3 The same fact, viz. that butters with abnormal refraction gave normal Reichert values, has been observed by Fischer, Chem. Zeit. 1895, 284. XI BUTTER EAT 625 that abnormal values were only found if the cows had been fed with linseed cakes, minute quantities of linseed oil passing into the milk, and consequently into the butter. In such cases, as Jean himself is forced to acknowledge, the indications of the oleo-refractometer must be supplemented by chemical methods (. Reichert’s process, etc.) The chief use of the apparatus would then consist, according to the same author, in admitting of a rapid examination for the purposes of market control, all the samples with the deviation of - 30° being allowed to pass, whereas doubtful specimens would have to be referred to the chemist for further examination. But even this restricted use of the oleo-refractometer may become illusory if we bear in mind that mixtures of margarine (deviation -11°) and of cocoa nut butter (deviation - 52°) may be prepared showing the correct deviation of -30\ For this reason the indications of the oleo - refractometer must be checked by other methods in every case. The same critical remarks apply to Zeiss's butyro-refractometer, which has been recommended by Wollny, and also by Mansfeld 1 and Hefelmann 2 on account of the great ease with which a large number of samples can be dealt with in a short time (20 samples in one hour). The instrument is shown in Fig. 44. The following notes con¬ cerning its use have been compiled from the printed directions supplied with the butyro-refractometer by its well-known maker. 3 Place the instrument upon a table, where diffuse daylight or any form of artificial light can be readily admitted for illumination. Supply through nozzle D a stream of water of a constant tempera¬ ture. Then open the prism casing by giving to pin F about half a turn to the right, until it meets with a stop, and turn the half B (held in position by H) of the casing aside. The prism surfaces must now be cleaned with the greatest care, which is best done by applying soft linen moistened with a little alcohol or ether. Now melt the sample of butter in a spoon, and pour the clear fat through a filter, allowing the first two or three drops to fall on the surface of the prism contained in casing B. For this purpose the apparatus should be raised with the left hand, so as to place the prism surface in a horizontal position. Then press B against A, and bring F back into its original position by turning it in the opposite direction. While looking into the telescope, give the mirror J such a position as to render the critical line which separates the bright left part of the field from the dark right part distinctly visible. It will be first necessary to ascertain whether the space between the prism surfaces is filled uniformly with butter, failing which the critical line will not be distinct. For this purpose examine the rectangular image of the 1 Forschungsberichte iiber Lebensmittel und ihre Beziehungen zur Hygiene, etc., Jahrgang i. Heft. 3. 2 Pharm. Oentralhalle, 1894, No. 33. 3 Carl Zeiss, Optische Werkstatte, Jena. 626 GLYCERIDES—ANIMAL FATS chap. prism surface about 1 cm. above the telescope with a lens. Finally adjust the movable part of the telescope, so that the scale becomes clearly visible. The critical line, somewhat hazy at first, approaches after about one minute a fixed position and quickly attains its greatest distinct¬ ness. This point being reached, note the appearance of the critical line ( i.e . whether colourless or coloured, and in the latter case of what colour), and then also note the position of the critical line on Fig. 44. the centesimal scale, which admits of tenths being conveniently estimated. The reading of the thermometer is then taken. The adjustment of the instrument should be tested periodically by means of a standard fluid supplied with the instrument, the critical line of which must occupy a definite position in the scale. By the aid of a watch-key inserted in G the position of the objective can be altered at will. . . The scale divisions may be converted into refractive indices by reference to the following table :— XI BUTTER FAT 627 Table of Refractive Indices Scale Division. D. Difference. 0 1-4220 10 1-4300 8-0 20 1-4377 7-7 30 1-4452 7-5 40 1-4524 7-2 50 1-4593 6-9 60 1-4659 6-6 70 1-4723 6-4 80 1-4783 6-0 90 1-4840 5-7 100 1-4895 5 "5 The results obtained by IVollny in the examination of a large number of butter and butter-substitutes are given in the subjoined table :— No. Kind of Fat. Temp. Scale Division. Refractive Index n D 1 Genuine butters . °C. 25 49-5-54-0 T4590-1-4620 2 Margarine . 25 58-6-66-4 1-4650-1-4700 3 Mixtures of 1 and 2 . 25 54-0-64-8 1-4620-1-4690 All samples giving higher values than 54-0 scale divisions for the critical line will, according to Wollny, be found adulterated when tested by chemical methods. As a practical limit 52'5 (at 25° C.) is recommended, so that all samples exceeding that number should be further examined. Besides the variability of the position of the critical line, also its appearance forms a means of comparison. This mode of differentiation is due to the peculiar construction of the double prism, which shows differences of dispersive power by different appearances of the critical line. The prisms are so constructed that the critical line of pure butter is colourless, while margarine and other artificial butters, which have greater dispersive powers than natural butter, show a blue critical line. This distinction, however, is unfortunately not applicable to each case, and the appearance of a blue fringe can only be looked upon as a useful indication in cases of suspected adulteration. In calculating the position of the critical line for other tempera¬ tures than 25° C., a correction of 0‘55 scale divisions for 1° C. should be made. The following table compiled in this manner 628 GLYCERIDES—ANIMAL FATS CHAP. gives the practical limits for pure butters at the corresponding temperatures :— Scale Division. 52-5 51-9 51-4 Temperature. °C. 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 49-8 49-2 48-6 48-1 47-5 47-0 46-4 45-9 45-3 44-8 44-2 437 431 42-6 42'0 41-5 Delaite, 1 however, has shown that calculation to the standard temperature from any other temperature does not give results identical with those observed at the standard temperature. It is therefore necessary to make the observations at a tempera¬ ture to be agreed upon. 40° C. seems to be a suitable temperature. Other physical methods have been proposed, but they are of minor importance ; although the difference in the constants for pure butter fat and other fats are distinct enough, such methods break down when applied to the detection of small quantities of foreign fats in butter. (c) Critical Temperature of Dissolution Crismer’s numbers, obtained with absolute alcohol - in the open tube, are given below. 3 Old and rancid samples of butter, or fresh butters badly prepared from sour cream, give lower figures. On neutralising, however, the free fatty acids and washing the fat, the normal critical temperature is obtained. 1 Bullet, de l’Assoc. Beige des Chimistes, 1894 (5), 145 ; Analyst , 1895, 95. 2 Ibid. 1886 (10), 312 ; Analyst , 1897, 72. 3 Cp. also Asbotli, Chem. Ztg. 1896, 686. This chemist employed alcohol of spec, grav. 0-8332 (90 per cent by volume). XI BUTTER FAT 629 Critical Temperatures With Alcohol, 0'7967 Specific Gravity (containing 0’9 per cent of water), at 15 - 5° C. in Open Tube. With Alcohol 0-8195 (8 - 85 per cent of water), at 15-5° C. in Sealed Tube. Differ¬ ence. Butter 1 Cl 54*8 b 54-8 c 54-8 d 54-6 e 54*3 / 53-8 100-5 45-7 2 54-5 54-5 54-5 54'2 100-5 46 3 57 57 57 103 46 4 54 54 100-5 46 5 50 50 105-5 45-5 6 56 102-5 46 7 56-5 52-2 102-5 46 8 52 52-4 56-5 52-4 51-2 98-2 45-7 Margarine and Mixtures 1 78 78 124 46 2 72-2 72-2 118 45-8 3 72-5 118 45"5 4 78 123-8 45-8 5 69 115 46-0 6 63-8 109 45-2 Maize oil 70'5 It is curious to note that in the case of a rancid butter the number of c.c. of — KOH required to neutralise 2 c.c. of butter fat 20 (dissolved in 20 c.c. of absolute alcohol), when added to the figure representing the critical temperature of the acid butter, gives approximately the critical temperature of the neutralised butter. 1 No. of Samples. a Mean Critical Temperature of Acid Butter. °C. b No. of — normal 20 Alkali required for 2 c.c. c.c. Critical Temperature of Neutralised Butter. °C. d Difference. c-a. 3 at 80-90° C. 88-5 7-5 96-4 7-9 14 at 90-96° C. 93-5 4-8 98-2 4-7 69 at 96-102° C. 99-12 1-2 101-7 2-6 17 at 102-106° C. 103-9 1-0 Crismer further points out that there is a certain relation between the Reichert-Meissl value of a butter and the critical temperature, the sum of the Reichert-Meissl value and the critical temperature corrected for neutralised butter being the constants : 129 for alcohol of 0'8195 spec, gravity, and 83"5 for absolute alcohol. There is also a certain relation between the critical temperature and the Hehner values, as evidenced by the following table:— 1 Bullet, cle VAssoc. Beige des Chimistes, 1897 (10), 453 ; Analyst, 1897, 158. 630 GLYCERIDES—ANIMAL FATS CHAl*. Critical Temperature for Hehner Value. Alcohol 0'S195 Absolute Alcohol. Per cent. with 9 per cent of water. °C. °C. Below 100 54 86-88 100-108 54-62 88-90-5 108-118 62-72 90-93-3 118-124 72-78 93-95-5 The variation of this constant for genuine butters is, however, too great to admit of its employment for the detection of small quantities of foreign fats. (cl) Viscosimetrical Examination This was proposed by Killing 1 and JVender, 2 but as this method is greatly inferior to others, as regards the chief problem of butter analysis, the reader must be referred to the references given below. The Calorimetrical Method (Jour. Soc. Chem. Incl. 1896, 560), the Electrical Conductivity, and the Cryoscopic Method 3 need only be mentioned in passing. Chemical Methods. Quantitative Reactions The most valuable indices in the chemical examination of butter are furnished by the Hehner value, the Reichert (Meissl ) value, and the Kbttstorfer or saponification value. The methods for their deter¬ mination have been fully described in chap. v. pp. 151 - 161. With a special view to shortening the time required for the analysis, “ new processes,” in reality, however, nothing but modifications and combinations of the well-known methods, are being continually proposed. Most of these proposals hardly deserve the name of “ method.” For the sake of completeness we describe several modifications, omitting, however, a host of others. Perkins 4 combines Hehner’s, Reichert’s , and Kbttstorfer’s processes in the following manner :— Saponify 1 to 2 grms. of butter fat, liberate the fatty acids by means of a solution of oxalic acid, saturated in the cold, taking care to avoid a large excess, and wash the fatty acids on a filter at first with cold, and finally with hot water. Concentrate the filtrate to exactly 200 c.c., distil 100 c.c. off, and examine the distillate, as in Reichert’s process. Thus the number of mgrms. of KOH required for saturating the volatile fatty acids of 1 grm. of butter fat is found. 1 Jour. Soc. Chem. Ind. 1895, 198. 2 Jour. Amer. Chem. Soc. 1895, 719. 3 Garelli and Carcano, Staz. Speriment. Agrar. 1893, 77. 4 Jour. Amer. Chem. Soc. 1889, 144. XI BUTTER FAT 631 Determine the insoluble fatty acids according to Hehner by weighing, dissolve them in 100 c.c. of alcohol, and titrate with deci- normal potash. Perkins found in this manner that the fatty acids in 1 grm. of butter fat required for the saturation of the Volatile fatty acids . . . 44-2 mgrms. of KOH Fixed fatty acids . . . 180 - 0 ,, ,, Or the total of . . 224 "2 ,, ,, The last number is, of course, the saponification value found in a somewhat roundabout fashion. Morse and Burton's 1 method is based on the fact that the ratio between the quantities of alkali requisite for the neutralisation of the soluble fatty acids on the one hand, and of the insoluble fatty acids on the other, is constant for any given fat. These relative quantities are given in the following table :— Kind of Fat. Per cent KOH required for Insoluble Acids. Soluble Acids. Butter fat. 86-57 13-17 Cocoa nut oil, not washed 91-85 8-17 ,, ., ,, washed with hot water 92-43 7'4z ,, ,, dilute COgNa., . 92-33 7-45 Cotton seed oil. 92-05 7-76 Oleomargarine. 95-40 4-57 Lard........ 95-96 3-82 Beef tallow. 96-72 3-40 The following four standard solutions are required:— 1. Hydrochloric acid, 1 c.c. of which is equivalent to 20 mgrms. KOH. 2. Hydrochloric acid, 1 c.c. of which is equivalent to 2 mgrms. KOH. 3. Alcoholic potash (prepared with 95 per cent alcohol) approxi¬ mately corresponding to acid No. 1. Before each experiment its strength must be accurately found by titrating with the acid. 4. Alcoholic potash, corresponding to acid No. 2. The analysis is carried out as follows :— Place from 1 to 2 grms. of the dry and filtered fat—the exact quantity need not be known—in an Erlenmeyer flask of 250 c.c. capacity, and saponify with that amount of the strong potash solu¬ tion which exactly equals 40 c.c. of the strong standard hydrochloric acid. Then add phenolphthalein, and titrate back the excess of alkali by the standard hydrochloric acid. This gives the saponification value. Evaporate off the alcohol on the water-bath, and exactly 1 Jout. Soc. Chem. Ind. 1888. 697. 632 GLYCERIDES—ANIMAL FATS CHAP. liberate the fatty acids by adding just enough of the weaker standard acid; this quantity is, of course, the difference between 40 c.c. and the number of c.c. used for neutralising the excess of alkali after saponification. Next fit the flask with a condensing arrangement, consisting of a glass tube about 400 mm. long and 5 mm. in diameter, having its upper end bent downwards, and attached to a small U-tube containing water. This is designed to prevent the escape of volatile acids during the heating of the flask, which is continued until its contents become clear. Then filter the solution, to which is added the liquid from the U-tube, through thick paper, well wetted, and wash the insoluble fatty acids until the filtrate measures 1000 c.c. Next dissolve the insoluble acids in 50 per cent alcohol, and titrate with the strong potash solution; finally titrate the soluble acids with the weak potash solution. The ratio only between the two amounts of alkali being required, it is neither necessary to weigh the fat nor to know the absolute strength of the standard alkalis. The Leffmann-Beam process of saponification having been adopted by several laboratories affiliated to dairies, it may be described here. 1 Mix 20 c.c. of a solution of 100 grms. of caustic soda in an equal weight of water with 180 c.c. of pure concentrated glycerin. Weigh 5 grms. of the filtered fat into an Erlenmeyer flask, add 20 c.c. of the alkali solution, and heat over a naked flame for two or three minutes until the water is driven off and the liquid becomes clear. Reichert-Meissl Value From the analyses of several thousand butters the fact has been deduced that this value is by no means so constant as Reichert's researches have led to believe, the quantity of volatile acids being influenced to a greater or smaller extent by the nature of the food, the seasons, the period of lactation, the rancidity, the method employed in melting the butter, and so on. In the following table there are collated the Reichert-Meissl values found by a number of chemists, the Reichert values (for 2‘5 grms.) having been multiplied by 2‘2 so as to admit of a comparison with the Reichert-Meissl values, although this procedure is, strictly speaking, not altogether correct. But as the limits allowed fox- variations of butters are greater than any error involved by the employment of a not strictly accurate factor, the table will be found useful for practical purposes. 1 Cp. Analyst , 1896, 251. [Table XI BUTTER FAT 633 Reichert-Meissl Values of Butter Fat Observer. Number of Samples. c.c. Decinormal Potash. Remarks. Reichert 2 f 30'S 1 Meissl Reichardt . Sendtner 2 1 2 27-0-31-5 \ 27-6-29-4 24-32-8 - Approximate deviation, ±0 - 9 German butters Thoerner . 2 l 22-32 J Nilson 797 22-9-41-0 Swedish butters Corbetta 178 26-1-31-4 Italian butters Spallanzani 2 20-63 Spallanzani and Pizzi. 2 19-8 Vigna 2 20-68 Maissen and Rossi 2 21-56 V Minima for Italian butters Besana 114 21-80 Longi 2 22-55 Sartori 2 23-59 Spallanzani and Pizzi. 2 30-14 Maximum for Italian butters Cornwall and Wallace. 2 27-36 American butters Ambiihl 2 28-10-31-10 Swiss butters Jean .... 2 29-26 French butters Muter 2 31-9 English butters Vieth 28 26-1-30-6 French butters Vieth 39 26-9-30-8 ,, ,, year following Swedish butters Vieth 22 26-9-29-4 Vieth 3 27-3-29-1 Holstein butters Vieth 3 28-8-29-9 ,, ,, year following English butters Vieth 7 27-6-29-2 Mansfeld . 88 24-42-33-15 Austrian butters These results prove that the Reichert-Meissl values of butter vary considerably in different countries. The minimum value adopted in this country, in France, and in Germany is 24, in Sweden 23, and in Italy 20. However, there are well-authenticated cases of genuine butters, prepared under direct supervision of chemical experts, proving that even these minima are sometimes too high. Thus Vieth 1 has found for butter prepared by himself from the milk of one particular English farm values ranging from 20*4-21’4. Similar cases having been stated by Morse? Falk and Bernhardt, 3 Samel son? Karschf the adopted minimum will have to be modified according to circum¬ stances. This should apply especially, according to Cornwall and Wallace, to butter fat obtained from one cow only. In butters made from the milk of a large number of cows exceptional values are naturally obliterated. As to the causes influencing the amount of volatile acids the nature of the food may tend to reduce their quantity. Thus Spallan- 1 Jour. Chem. Soc. 1891, 507. 2 Jour. Analyt. and Applied Chem. 1893, 1. 3 Zeit. anqew. Cliemie, 1890, 728. 4 Chem. Ztg. 1895, 1626. The butter gave the following constants : Reichert-Meissl value, 21 - 6, Hehner value, 89'2, saponification value, 216’0, iodine value, 42‘5. 5 19-6-22-8, Chem. Ztg. 1897, Ref. 19. 634 GLYCERIDES—ANIMAL FATS CHAP. zani and Pizzi x state (in the case of Italian butters) that when cows are out to grass butter is rich in volatile acids, and poorer in volatile acids when stall-fed and on a poor ration. It has further been shown that cows fed with cotton seed cakes yield butters of higher melting point with a corresponding decrease of about 1 per cent of volatile fatty acids. 2 It has been mentioned already that butter from cows fed with linseed cakes behaves abnormally in the refractometric examination. Schrodt and Henzolcl, however, deny the influence of the food. The variation of the Reichert-Meissl with the seasons is clearly brought out by the following numbers, due to Vietli : 3 — London-made Butter. Reichert-Meissl Value. 25-8-27 T 27-2-30-0 From July 30 to November 12, 1889 From Mai’ch 25 to June 24, 1890 . This agrees with Swaving’s experience, that in the beginning of the grazing season the volatile acids increase, remaining at a high figure until the close of that season. Greater fluctuations are caused by the periods of lactation. According to Nilson, the Reichert-Meissl value decreases from 33‘44 in the first month to 25'42 in the fourteenth month of lactation; according to Vietli, Holstein butter, made at a time when most of the cows were nearing the end of the period of lactation, gave numbers as low as 2T7; also Spallanzani and Pizzi find higher Reichert-Meissl values in the early stages of lactation than in the later ones. [ Swaving , 4 indeed, goes so far as to consider 14 as the permissible minimum. This, however, is unquestionably far too low.] Similar depressions occur during the rut-time and illness of the cows. Samples of butter sent to the chemical laboratory for examination arriving in most instances in a rancid state, the influence of rancidity on the Reichert-Meissl value has engaged the attention of several chemists. C. Virchow and Schweissinger state that highly rancid butters give lower numbers ; this has been confirmed by Corbetta and Cornwall. The decrease due to this cause is, however, comparatively small, for Corbetta found, after two and a half months, a loss of T7 c.c., and Cornwall of T6 c.c. only after eight months. The method employed in melting the butter fat may also bear on the result. Planchon states that a sample of butter containing 3'92 per cent of volatile acids (in terms of butyric acid) gave, after warm¬ ing to 50 C. for two hours, 4T7, and after fourteen hours’ Avarming 4'80 per cent. The butter fat should, therefore, be prepared by melting the butter rapidly at a lower temperature. Nor should the precaution be neglected to obtain a proper average from the sample 1 Le Staz. Speriment. Agr. Ital. 38. 257. 2 Revue internat. defalsific. 1889, 200. Stein (Jour. Chem. Soc. 1895, Abstr. ii. 299) states that the substance in cotton seed oil giving the Becchi reaction passes into milk and even butter, when cows are fed with cotton seed cake ; not so the substance giving Baudouin’s reaction, when the cows are fed on sesame cake. Cp. footnote p. 603. 3 Jour. Chem. Soc. 1891, 508. 4 Landw. Versuchsstat. 1891, 127. XI BUTTER FAT 635 supplied. Medicus and Scheerer state that they have found differences amounting to 4 c.c. between samples taken from the interior and the sides of the containing vessel (cp. p. 609). The literature contains—owing, no doubt, to the importance of butter analysis—a great number of suggestions, some of which verge on the ridiculous. There are also innumerable suggestions as to improvements of the undoubtedly excellent Reichert process; most of them, unfortunately, are the reverse of improvements. As an example of a superfluous method may be given Kreis’s modification of Reichert’s process, since it has met with greater attention than it actually deserves. Kreis employs for saponification instead of alcoholic potash concentrated sulphuric acid, but whereas on a large scale saponification is effected with 3 or 4 per cent of acid, Kreis uses no less than 10 c.c. for 5 grms. of butter fat. However, the experi¬ ence of several chemists, including the writer, has proved that invari¬ ably sulphurous acid is liberated, which, of course, must vitiate the results unless the sulphurous acid is removed or otherwise rendered innocuous. The ingenuity of several analysts has been exercised to eliminate the error due to the presence of S0. 2 ; others again have tried to exactly define the strength of the acid required so as to avoid formation of S0 2 . In short, minutiae of a most aggravating character are gone into just in order to squeeze out, as it were, results in agree¬ ment with those furnished by Reichert’s distillation process, which, after all, must be used as a standard to gauge the correctness or otherwise of the new method. Both Reichert and Meissl , being under the impression that their values were fairly constant, thought that the quantity of a foreign fat added to the butter could be calculated by their method. The following formula was supposed to give the amount of real butter fat in the sample :— 100(7i-C) 28 78-C ’ where n is the Reicliert-Meissl value of the sample, and C the cor¬ responding value for the admixed fat. 28'78 is taken as represent¬ ing the number for pure butter fat. Meissl is of opinion that, on an average, C may be assumed to equal 3, which is, no doubt, too high for the majority of fats. Since, however, the Reichert-Meissl value is by no means constant, as has been demonstrated in the table given above, a calculation of this kind is inadmissible (< Sendtner 1 ). Excellent as Reichert’s method is, a sophistication with 20 per cent of a foreign fat in the case of excellent butter, or of 10 per cent in the case of butter of ordinary quality, cannot be detected with certainty. Still, it must be considered the best method hitherto designed for the detection of frauds, no other method allowing a rapid 1 Repert. der analyt. Chemie, 3. 345. 636 GLYCERIDES—ANIMAL FATS CHAP. discrimination between genuine butter and a judiciously prepared mixture of margarine and cocoa nut oil. The following table demon¬ strates this clearly :— Eeichert-Meissl Values Kind of Fat. c.c. Decinormal Potash. Observer. Cocoa nut oil. 7-0-7-8 [ Reichert, -J Moore, Allen, “Margarine”. ‘ ‘ Oleomargarine ”. 2-6 [ Muter Muter 0-8-0-9 Jean Butter fat with 10 per cent of cocoa nut oil 26-8 „ „ 20 „ 24-13 Muter „ „ 25 „ 24 >! >) 50 ,, ,, ., 18 J? >> A ,, ,, J, 50 parts of butter fat, 22 - 5 parts of cocoa nut oil, and 27 "5 parts of oleomargarine . 12 17-4 Moore Only in those cases where solely oleomargarine is the adulterant, and it exceeds 10 per cent, the determination of the saponification value may lead to results in a shorter time; this value will then be found low. As a rule it is advisable to combine the determination of the saponification number with that of the Eeichert-Meissl value. Where butyric acid, butyrin, or amyl acetate have been added to conceal fraud, a high saponification value in conjunction with a normal Eeichert-Meissl value may reveal it. If there be reason to suspect that butter oil, containing more volatile acids than butter fat, has been added to a sample, it will be best to resolve the fat into an oily and a solid part (p. 609), or to ex¬ tract with alcohol and examine each portion separately by the Eeichert- Meissl process. In those cases where the Eeichert-Meissl value just reaches the limit of 24 the analyst is confronted with the uncertainty as to whether the butter is adulterated or not. 1 Additional assistance may be found in such cases in the determination of the specific gravity, the saponi¬ fication value, and also in the employment of the oleo-refractometer or butyro-refractometer. In the following table some of the Eeichert- Meissl values given above are tabulated side by side with the deviations in the oleo-refractometer :— 1 Muter states (Analyst, 1891, 90) that there is in the London market much cheap butter that shows exactly 26 in the Reichert-Meissl test. [Table XI BUTTER FAT 637 Oleo-refradometer No. Fat. Reichert- Meissl Value. Deviation. Observer. 1 Genuine butter ...... 29-26 -30 Jean , , , , Cocoa nut oil ...... 31-9 -34 Muter 1 2 7-8 -59 Jean Genuine butter with 10 per cent of cocoa nut oil 7-7 -54 Muter 3 26'8 -33 Jean 4 „ „ „ 15 „ -34 5 ,, ., ,, 20 .. 24T3 -36 Muter 6 ,. „ ,, 25 ,. 26-4 -39 7 „ ,, ,, 50 .. 19-8 - 44 8 ,, ,, ,, 75 ,, 13-2 -49 9 Margarine ....... 2'8 - 8-5 10 Genuine butter with 25 per cent of margarine 24 -27 11 „ „ „ 50 „ 17 T -22 12 „ „ 75 „ Margarine with 50 per cent of cocoa nut oil . 9-9 -15 13 6T -32 , , 14 50 per cent genuine butter with 25 per cent of margarine and 25 per cent of cocoa nut oil. 19-3 -33 15 25 per cent genuine butter with 50 per cent of margarine and 25 per cent of cocoa nut oil. 12-3 -27 ” Similar observations with the butyro-refractometer are recorded in the following table, due to Mansfeld :— 1 The Reichert values given by Muter have been multiplied by 2'2 for the sake of better comparison. [Table 638 GLYCERIDES—ANIMAL FATS CHAP. Butyro-refradometer No. Fat. Scale Divisions at 40° C. Reichert-Meissl Value. Remarks. 1 Butter 41-6 31-5 Genuine 2 42-3 30-8 „ 3 43-6 29-8 77 4 44'2 28-7 7 7 5 44-2 28-6 7 » 6 . 41-6 28-6 ,, 7 43-0 28-2 » 1 8 44-0 28-1 9 43-5 27-9 •n 10 44-1 27-1 7 j 11 42-5 27-0 >> 12 44-4 26-8 7 7 13 43-3 26-7 77 14 43-7 267 7 7 15 42-1 26-4 1 7 16 43-2 26-3 7 7 17 . 43-1 26'2 7 7 18 . 44-0 25-4 7 7 19 43-1 77 20 . 42-3 77 21 7 7 * * 43-0 ” 22 41-6 24-4 Suspected on account of 23 42-4 24-3 low Reichert - Meissl 24 42-5 23-9 value 25 45-1 22-6 Contains 18 % of foreign fat 26 46-1 7'2 „ 76% 27 ! 47-1 6'5 „ 78 % 28 48-6 37 „ 89 % 29 Butter substitute 49'2 3-1 „ 91 % 30 Melted butter . 49-0 3'0 „ 91-5% „ 31 Artificial butter 48-6 2-3 „ 94 % 32 Oleomargarine . 48-6 1-2 The inspection of the figures in the table headed oleo-refractometer proves that 10 to 15 per cent of cocoa nut oil—Nos. 3 and 4—cannot be detected by either method. A commercial butter thus adulterated would, in the present state of our knowledge, have to be considered genuine. 1 Even values, like those given in No. 5, would not justify the analyst in condemning a butter, although he may declare it suspicious. In the case, however, of values like No. 6 being obtained, adulteration may be taken as proved because of the abnormal devia¬ tion conjointly with a Beichert-Meissl value just reaching the limit. In all other cases the distillation process alone leads to unmistakable results. Muter suggests that there may exist a relation between Beichert- Meissl value and deviation in the oleo-refractometer, as shown in the following table :— 1 It is to be hoped that the determination of stearic acid in the insoluble acids according to Hehner and Mitchell’s method may lead to unmistakable results. XI BUTTER EAT 639 Reichert-Meissl Value. Deviation. Pure butter 32 -36 5 5 30-5 -35 ,, 29-0 -34 27-5 -33 ,, 26 -32 J > 24-5 -31 ? 23 -30 ? 21-5 -29 Saponification Value Kottstorfer 1 found that 1 grm. of butter fat required from 221’5 to 232'4 mgrms. KOH ; the mean saponification value of butter may therefore be taken as 227. There are, however, exceptions. The saponification number 216 for a genuine butter has been recorded already (p. 633, footnote 4). The following table gives the results of the examination of 185 butters (Silesian), due to Seyda and Woy :— Saponification Number. Per cent of the Samples examined. 221-223 4 223-225 7 225-226 7 226-228 15 228-230 21 230-233 28 Above 233 18 The saponification value of oleomargarine being about 195-5, it would appear that the proportion of it in a sample may be calculated from the formula 227 -n X-iOO. 22 7- 19 5- 5 — ^‘17(227- n). If, however, the usual variations in the saponification value be allowed for, errors amounting to as much as 10 per cent and even more may occur. Moreover, Moore has shown that, owing to the ex¬ ceptionally high saponification value of cocoa nut (and palm nut) oil, it would be an easy matter to prepare mixtures of this oil and margarine having exactly the saponification value of genuine butter fat. 1 Zeitsch. analyt. Chem. 1879, 199. 640 GLYCERIDES—ANIMAL FATS CHAP. Hehner Value Hehner’s 1 experiments demonstrated the fact that the proportion of insoluble acids in butters varies from 86'5 to 87"5 per cent, reaching sometimes 88 per cent; therefore 87'5 was taken by him as the mean value. • ... . . In some butters, however, containing considerable quantities of lauric acid, which can only be washed out with difficulty, too high values may be found, unless Fleischmann and Vieth’s device (p. 160) be adopted. The limits for the Hehner value obtained by other experi¬ menters are given in the subjoined table :— Hehner Values of Butter Observer. Per cent Insoluble Acids. Lower Limit. Upper Limit. J. Bell .... GO V\ zh 87-9 Fleischmann and Vieth . 8579 89-73 West-Knight . 88-08 Butter having a Hehner value exceeding 90 must, according to Fleischmann and Vieth , be considered adulterated; butters yielding 88-90 per cent are suspicious, whereas 88 or less would point to genuine butter. The same chemists state that the Helmet value is not influenced by rancidity, whereas J. Bell has demonstrated by experi¬ ments that the amount of the insoluble acids increases on keeping, as shown in the following table :— Analysis of Samples of Butter after keeping ( J . Bell). Original Butter. Time Kept. After Keeping. Specific Gravity at 37-8° C. Hehner Value. Specific Gravity at 37-8° C. Hehner Value. ( = 100° F.) (=100’ F.) 0-91228 87-30 12 weeks . 0-91074 88-97 0-91158 87-80 7 „ 0-90919 90-00 0-91389 85-50 7 „ 0-91357 85-72 0-91178 87-40 6 „ 0-91100 87-97 0-91106 87-72 8 „ 0-91061 88-40 0-91148 87-65 6 „ 0-91133 88-00 1 Zeitsch. anohyt. Chem. 1877, 145. XI BUTTER FAT—STAG FAT 641 . ^ should, however, be borne in mind that a high state of rancidity is in itself a guarantee for the purity of butter. Moore has pointed out that mixtures can be prepared from oleo- maigarine and cocoa nut oil giving the same Hehner value as pure butter. Thus a mixture consisting of 50 parts of butter fat, 2 7-5 parts of oleomargarine, and 22'5 parts of cocoa nut oil, yields 89'5 per cent of insoluble acids. It is therefore evident that the Hehner value alone cannot be considered a criterion of the purity of a sample of butter. Iodine Value The iodine absorption is of but little value in the examination of butter. This is shown in the first instance by the great variations found by different observers 1 as set out in the following table:_ Iodine Values of Butter Fat Observer. Per cent. Hiibl Moore Woll 2 . Williams :l Zenoni 4 . Minimum. 26 19-5 257 32-25 22-8 Maximum. 35-1 38 37- 9 38- 91 35-8 On the other hand mixtures may be prepared with the greatest ease from cocoa nut oil (iodine value 8*9) and animal fats, the iodine absorptions of which coincide with those tabulated above. STAG FAT 5 I i ench (rvaisse de cerf. German— Ilirschtalg. For tables of constants see p. 642. ^ The specimen examined by Amthor and Zink 6 had the acid value .3'5 in the fresh state, and 5'9 after one year. I £ hu abnormal butter referred to, p. 633, footnote 4, bad the iodine value 42‘5 - Zeitsch. analyt. Ohem. 1888, 532. 3 Analyst, 1889, 104. 4 II Selva, 1894, 28 ; 46. , * T£ e con stants of fats from animals closely related to the stag have been given above tP- ooth 8 Zeitsch. f. analyt. Chemie, 1897, 4. XX LIQUID WAXES—SPERM OIL 643 B. WAXES I. LIQUID WAXES Only two representatives of this class are known, viz. sperm oil and Arctic sperm oil. They are in many respects, as regards origin, smell, and taste, and some colour reactions, very similar to blubber oils; so much so, that some writers class them with the latter oils. On account of their different chemical composition, I have separated them from the other blubber oils, disregarding the fact that amongst the members of the blubber oil group xve notice a gi'adual transition from the nearly pure glycerides (seal oil), through some intermediate members (dolphin oil) containing considerable proportions of waxes, to the time liquid waxes. The genei-al chai’acteristics of this class have been given already (p. 277). SPERM OIL French— Huile de cachalot; Huile de spermaceti. German— Walratoel. For tables of constants see below, and p. 644. Sperm oil is the liquid portion of the blubber from the sperm whale, or cachelot, Pliyseter macrocephalus. The fresh blubber sepa¬ rates on standing in the cold into two portions, a solid (spermaceti; cp. p. 669) and a liquid one (sperm oil). The latter is sepai’ated by filtration or expression. Sperm oil is a pale yellow, thin oil, almost free from odour.. Its chemical constitution assigns to it a place amongst the waxes, con¬ sisting as it does wholly of compound ethers (esters) of fatty acids and monovalent alcohols. Contrary to Hoffstiitter’s statement, the absence of glycerides has been proved by Allen and by the writer. Possibly Hoffstiitter 1 has examined an oil mixed with porpoise oil, since he has found valeric as well as glycerol. The fatty acids of sperm oil, a few characteristic constants of which are given p. 644, appear to belong to the oleic series, as showxx by their iodine value, and by their property of yielding elaidin with nitrous acid.. The nature of the acids is as yet unknown. Hoffstdtter’s 2 earlier state¬ ment that the acid is physetoleic acid stands in need of confirmation. Physical and Chemical Constants of Alcohols {Unsaponifiable Matter) Solidifying Point. Melting Point. Iodine Value. °C. Observer. °C. Observer. Per cent. Observer. 23-23-4 Lewkowitscli 25-5-27-5 Lewkowitscli 64-6-65-8 Lewkowitscli 1 Liebig’s Annalen , 91. 177. 2 Ibid. l Calculated from bromine addition value 54 - 54 (bromine substitution value being 1‘04). XI SPERM OIL 645 The alcohols of sperm oil are also unknoAvn. The writer 1 has tried to resolve the mixed alcohols into their several constituents by fractional distillation of both the alcohols themselves and of their acetates, but hitherto these experiments have not led to any definite result—except this, that neither dodecatyl nor pentadecyl alcohol is present, and that the sperm oil alcohols belong for the most part, if not wholly, to the ethylene series, the higher members of A\drich have been hitherto unknown. This will be readily seen from the following table, giving the saponification values of the acetates of the five fractions into A\ r hich the total acetates had been resolved, and the iodine values of the corre¬ sponding alcohols themselves. For the sake of comparison the theoretical numbers are given for alcohols, the presence of which might be naturally expected. Alcoliols from Sperm Oil. Saponific. A'alue of Acetate. Iodine A'alue of Alcohol. 1st fraction 190-2 46-48 2nd ,, ... 183-8 63-30 3rd „ ... 1807 69-80 4th ,, ... 174-4 81-80 5th ,, ... 161-4 84-90 Alcohol C 16 H 3 ,0 (unknown) 199 106-6 ,, C 18 H 36 0 (unknown) 180 94-8 ,, C 20 H 40 O (unknown) 166 85 "8 On heating 2 the alcohols Avith soda lime, the bulk Avas converted into fatty acids, only 4-6 per cent of unchanged alcohol being re¬ covered ; the crude fatty acid had the acid value 181 ’7, and the melt¬ ing point 38°-40° C. The writer is still engaged on a research into the nature of the sperm oil constituents. Commercial sperm oil contains but small quantities of free fatty acids. The folloAving table records a feAv numbers :— No. Sperm Oil. Free Fatty Acids, as Oleic Acid. Per cent. Observer. i Best quality, cold bagged Second, “ hot pressed ” . 0-29 Deering 2 0-42 11 3 Intermediate quality 0-15 If 4 Oil of good quality 0-42 if 5 Oil of doubtful quality . o-ii if 6 if if f) • Oil of bad quality . 19 19 • • 0-41 if 7 0-42 a 8 2-64 Thomson and Ballantyne 1 Lewkowitsch, Jour. Soc. Chem. Ind. 1892, 134. 2 Ibid. 1896, 41. 646 LIQUID WAXES CHAP. Sperm oil is a valuable lubricating oil for spindles and light machinery, on account of its high viscosity and slight tendency to become rancid and, consequently, to gum the bearings. Its compara¬ tively high price suggests adulterations with fatty oils or hydrocarbon oils. Its characteristic properties, however, render the detection of all adulterants an easy task, with the exception of Arctic sperm oil, the physical and chemical characters of which are almost identical with those of sperm oil. The specific gravity of sperm oil being very low, a high density would point to the presence of fatty oils. Mineral oils of the same specific gravity could, of course, not be detected by the determination of this constant. However, a mixture of fatty oils with hydrocarbon oils, to meet the specific gravity test, would require oils of so low a specific gravity that the flash point of the resulting oil would be very low indeed. The low saponification value furnishes a ready means of detecting added fatty oils, such as rape oil, blubber oils, etc. As, however, a judiciously added quantity of mineral oil may compensate the increase of the saponification value due to this cause, an apparently normal oil may result in the end. In fact, Lobry cle Bruyn 1 has shown that oils occur in commerce consisting of a mixture of sperm, blubber, and mineral oils. The saponification value alone cannot, therefore, be considered as finally proving the purity of the sample. Certainty can only be attained by examining, on the one hand, the unsaponifiable matter as detailed above (pp. 224-233); and, on the other hand, by estimating the amount of glycerol (cp. p. 207). The proportion of the latter multiplied by 10 will approximately yield the percentage of fatty oils. The viscosity of sperm oil is very characteristic; it is lower than that of any other non-drying fatty oil, and it does not vary so much as that of other oils with an increase of temperature (cp. tables, p. 268). Allen recommends the observations to be made at the follow¬ ing three temperatures: lS'S 0 C., 50° C., 100° C. Colour reactions are hardly required in the examination of sperm oil. Any of the liver oils, which might have been used as an adulterant (Allen), would be detected by the sulphuric acid test in which liver oils give a violet colouration, changing to red, whereas sperm oil yields a brown colour, changing to dark brown. Besides, liver oils would be readily detected by the high iodine value, Maumene’s test, and the presence of glycerol in the sample. 1 Jour. Soc. Chem. Ind. 1894, 426. XI ARCTIC SPERM OIL 647 ARCTIC SPERM OIL (BOTTLENOSE OIL) French— Haile de Vhyperoodon. German— Doglingthran. For tables of constants see below, and p. 648. Arctic sperm oil is the oil obtained chiefly from the bottlenose whale, Hyperoodon rostratus. It is, as a rule, darker in colour than sperm oil, which it so closely simulates that, notwithstanding the slight differences to be found in the tables (solidifying points of fatty acids), they might be declared identical as far as chemical examination goes. In the elaidin test Arctic sperm oil yields a very much softer elaidin than sperm oil. According to the table of constants the refractometer would appear to furnish a ready means of distinguish¬ ing Arctic sperm oil from sperm oil, but the refractometric constants require confirmation. In commerce, however, these two oils are readily distinguished by their taste. Arctic sperm oil is lower in price on account of its more pronounced tendency to “gum.” Scharling, writing in the year 1848, states that Arctic sperm oil is the dodecatyl ether of doeglic acid. It hardly needs pointing out that this statement requires confirmation. The writer is engaged on an inquiry into the nature of the constituents of this oil. The amount of free fatty acids in two samples of Arctic sperm oil, examined by Deering, and Thomson and Ballantyne, was found 0 - 42 and 197 per cent respectively. Physical and Chemical Constants of Alcohols (Unsaponifiable Matter) Solidifying Point. Melting Point. Iodine Value. °C. Observer. ° 0 . Observer. Per cent. Observer. 217-22-0 Lewkowitsch 23-5-26-5 Lewkowitsch 64-8-65-2 Lewkowitsch [Table 1 Calculated from bromine value. XI VEGETABLE WAXES—CARNAUBA WAX 649 II. SOLID WAXES 1. VEGETABLE WAXES Vegetable waxes, the exudations of plant leaves, seem to be widely spread over the vegetable kingdom, though mostly occurring in small quantities. With the exception of carnaiiba wax (which has been exhaustively examined), the nature of these waxes (opium wax (p. 15), palm wax, ocuba wax, getah wax, ocotilla wax, cotton seed wax, etc.) has been but little studied. CARNAUBA WAX French— Cire de carnauVh. German— Carnaubawaclis, Cearawachs. For table of constants see p. 650. Carnaiiba wax is a vegetable wax exuded by the leaves of Corypha cerifera (Copernicia cerifera), a palm indigenous to tropical South America, especially to the province of Ceara, Brazil. The crude wax, as obtained from the plant, is dirty greenish, or yellowish, very hard, and so brittle that it can be readily powdered. Carnaiiba wax dissolves completely in ether and boiling alcohol; on cooling, a crystalline mass, of melting point 105° C., is deposited from the alcoholic solution. On ignition, carnaiiba wax yields 0‘43 per cent of ash. Carnaiiba wax consists chiefly of myricyl cerotate, and small quantities of free cerotic acid and myricyl alcohol; the latter is easily removable by cold ethyl alcohol. StilrcJce, 1 who has carried out a very complete research into the chemistry of carnaiiba wax, maintains that free cerotic acid is absent. The definite acid value, however, found by independent observers, undoubtedly points to its presence. According to Stiircke, the constituents of carnaiiba wax are the following:— (1) A hydrocarbon, melting point 59°-59'5 C. (2) An alcohol of the composition C 26 H 54 0 (ceryl alcohol), melt¬ ing point 76° C. (3) Myricyl alcohol, C 30 H 62 O, melting point 90° C. 2 (4) A dihvdric alcohol C 25 H 59 0 2 (cp. p. 76), melting point 103-5°-103-8° C. (5) An acid C., 4 H 4s 0 2 (carnaiibic acid), melting point 72 ‘5° C. (6) Cerotic acid, C o6 H 50 0 o . " " CH OH (7) An hydroxy acid C 21 H 42 0 2 = C 19 H 3S qqqjj > or its lactone 1 Liebig's Annalen , 223. 283. 2 Gaxcard (Jour. Soc. Chem. Ind. 1893, 955) assigns to it the formula C a iH G4 0. 1 Recently purified. 2 old specimen. 3 By saponification in the cold. XI CARNAUBA WAX—WOOL WAX 651 Carnaiiba wax is not readily saponified by alcoholic potash; this may explain the unsatisfactory agreement between the saponification numbers given above. Carnaiiba wax is employed in the manufacture of candles and of some wax varnishes. 1 Valenta has examined the melting points of the following mixtures of carnaiiba wax with stearic acid, cerasin, and paraffin wax :— Proportion of Carnaiiba Wax. Melting-Point of Mixtures of Carnaiiba Wax with Stearic Acid of Melting Point 58 - 5° C. Cerasin of Melting Point 72-7° C. Paraffin Wax of Melting Point 60-5° C. Per cent. °C. °C. °C. 5 6975 79-10 73-90 10 7375 80-56 79-20 15 74-55 81-60 81-10 20 75'20 82-53 81-50 25 75-80 82-95 81-70 The table shows that the addition of 5 per cent of carnaiiba wax to the substances named causes a considerable increase in their melting point; further additions, however, do not cause a proportional increase. Stearic acid in carnaiiba wax would be detected by the high acid value of the sample; cerasin and paraffin wax by the high percentage of unsaponifiable matter. 2. ANIMAL WAXES The animal waxes contain but small quantities of unsaturated acids and alcohols. The components of beeswax, spermaceti, and insect wax are well known; their acids and alcohols belong chiefly to the saturated (aliphatic) series. Wool wax, however, has an exceptional chemical composition ; some of its alcohols are derivatives of the aromatic series, and its fatty acids are characterised by the facility with which they become dehydrated. Wool wax is also remarkable for the great difficulty with which it is saponified even by alcoholic caustic potash. WOOL WAX 2 (WOOL GREASE) French— Suint. German— JVollfett , JVollschweissfett. For tables of constants see pp. 653, 654. The term wool wax has been proposed by the writer for the neutral portion of the raw wool fat, the fatty matter excreted by sheep, and obtained from the wool by extraction with volatile solvents, or in the process of washing the wool with dilute sodium 1 Jour. Soc. Chem. Ind. 1894, 744. 2 Lewkowitsch, ibid. 1892, 135 ; 1896, 14. 652 ANIMAL WAXES CHAP. carbonate. The raw wool fat contains besides potassium salts of volatile fatty acids, naturally free fatty acids and free alcohols; and if recovered by washing the wool it is contaminated with fatty acids derived from soap. The raw wool fat will be dealt with in chap, xii.; here, we only consider the neutral portion as obtained after removing the free fatty acids from the raw product. In this state it still contains free alcohols. The constants given pp. 653, 654 refer, therefore, to the neutral esters plus free alcohols. There is also added a table No. IY. containing a few chemical constants of the neutral esters only. Wool wax is a pale yellow, translucent substance, having a slight but not unpleasant smell (whereas the raw wool grease is characterised by its peculiar disagreeable smell, recalling that of sheep). Its con¬ sistency is that of a thin ointment. Wool wax is sparingly soluble in alcohol, but dissolves readily in chloroform and ether and ethyl acetate. Although insoluble in water, it possesses the remarkable property of absorbing large quantities of water, forming an emulsion with it that has the appear¬ ance of a perfectly homogeneous mass. Thus wool wax can be mixed with as much as 80 per cent of water. A mixture of neutral wax and water, containing about 22-25 per cent of the latter, is sold in commerce under the name “lanoline” (p. 689). Wool wax cannot be wholly saponified by aqueous caustic alkalis ; even prolonged boiling with alcoholic potash under ordinary pressure does not effect complete saponification. Sodium alcoholate (or absolute alcohol and metallic sodium) or alcoholic potash under pressure, how¬ ever, effect complete saponification (cp. chap. ii. p. 22). Glycerides do not occur in wool wax. The chemical composition of wool fat is as yet unknown. It is evidently a very complex mixture of ethers; amongst the alcohols, cholesterol and isocholesterol occur to a large extent. Lewkowitsch was the first to show that the statement previously accepted, viz. that neutral wool wax is a mixture of eholesteryl (and isocholesteryl) oleates and stearates, is erroneous. The low iodine value of both the fatty acids and the alcohols precludes this altogether. Nor is the presence of ceryl cerotate, asserted by Buisine, to be accepted without further proof, as ceryl alcohol occurs in raw wool fat in the free state. An inquiry into the nature of the components (on which the writer is still engaged) has shown that the mean molecular weight of the alcohols (239), in conjunction with the low iodine value (36), points to the presence of lower saturated alcohols, cholesterol and iso¬ cholesterol having the molec. weight 372, and the iodine absorption 68 - 3. The fatty acids, as is shown by their very low iodine absorp¬ tion, cannot consist to any great extent of oleic acid. They consist of hydroxy acids, 1 easily giving off the elements of water at temper¬ atures little above 100° C., with formation of inner anhydrides or lactones, and assimilating considerable quantities of acetic anhydride, forming acetylated acids. 1 Jour. Soc. Chem. Ind. 1892. 136: 1896, 14. . Physical and Chemical Constants of JFool JFax (i.e. Esters and Free Alcohols) 654 ANIMAL WAXES CHAP. III. Physical and Chemical Constants of the Mixed Alcohols Solidifying Point. °C. Melting Point. "O. Mean Molecular Weight. Iodine Value. Observer. 28 1 33-5 1 239 1 36 1 26 '4 2 Lewkowitscli IV. Chemical Constants of the Neutral Esters Saponification Value. Fatty Acids. Alcohols. Mgrms. KOH. Observer. jPer cent. Observer. Per cent. Observer. 96-9 Lewkowitscli 56-66 Lewkowitscli 47-55 Lewkowitscli Marclietti 3 states that he has isolated an alcohol of the formula Ci 2 H 24 0—termed lanolin alcohol. Since, however, two other alcohols described by Darmstadter and Lifschutzf and supposed to form a homologous series with lanolin alcohol, have been shown to be lactones (see above), the existence of this alcohol becomes doubtful. The following fatty acids have been isolated by Darmstadter and Lifschutz 5 from wool wax :— (1) Lanoceric acid, C 30 H 60 O 4 (p. 66). (2) Lanolpalmic acid, C 16 H 32 O 3 (p. 63). (3) Myristic acid. (4) Carnaiibic acid. (5) An oily acid. [(6) A volatile acid, presumably caproic acid. The alcohols were resolved by absolute alcohol into four fractions, in which hitherto cholesterol and the saturated alcohol carnaubyl alcohol have been identified. From the researches of G. de Sanctis 6 it would follow that cerotic and palmitic acids must be added to the wool wax fatty acids. On account of its property of forming an emulsion with water and being easily absorbed by the skin, wool wax is used as a basis fox- ointments and cosmetics. For wool fat, cp. xii. p. 686. 1 From raw wool fat. 2 From lanoline. 3 Gazz. Chimica, 1895, 22. 4 Berichte, 1895, 3133. 5 Ibid. 1896, 618 ; 2890 ; Jour. Sue. Chem. Ind. 1896, 548 ; 1897, 150 6 Chem. Ztg. 1895, 651. XI BEESWAX 655 BEESWAX 1 French— Cire des abeilles. German— Bienenwachs. For table of constants see p. 656. The wax as obtained from the honeycombs is, as a rule, of a yellow or yellowish colour. There are, however, some commercial waxes, mostly of non-European origin, having a greenish, reddish, or brown colour. Yellow wax has the pleasant smell of honey, and is almost tasteless. At low temperatures it is brittle, and of fine granular fracture. By repeated melting in water, or by exposure to sunlight, in the shape of granules, or strips, or ribbons, white wax is obtained. 2 This is of a pure white or slightly yellowish colour, odourless, and taste¬ less. It has a higher specific gravity than yellow wax, and is more brittle. It is transparent at the edges; its fracture is smooth, and no longer granular. In practice it is customary to mix with the yellow wax previous to air-bleaching 3 to 5 per cent of tallow, or a small quantity of oil of turpentine, so as to accelerate the process, and to obtain a pure white product; these additions also prevent the wax from becoming too brittle. Yellow wax may also be decolourised by treatment with animal char or with chemicals, such as potassium permanganate, potas¬ sium bichromate and sulphuric acid, and hydrogen peroxide (Buisine ). Wax is not greasy to the touch, but if dropped on paper in the melted state it causes a permanent transparent spot. A regular constituent of wax is pollen, so that wax when in admixture with other substances may be detected by microscopic examination. Considered chemically, wax 3 is chiefly a mixture of crude cerotic acid 4 (cp. p. 50) and myricin (myricyl palmitate). In smaller quantities there occur also melissic acid, C^H^O.,, or C 31 H 69 0 9 , in the free state; and, according to Schwalb, myricyl alcohol , 5 C 30 H 62 O, or C 31 H 64 0, and small quantities of ceryl alcohol and of another alcohol of unknown composition. Small quantities of unsaturated fatty acids and hydrocarbons have also been found. Schwalb has isolated the two hydrocarbons — heptacosane, C 27 H 5(i , melting point 605° C., and hentriacontane, C 31 H 64 , melting point 67° C. (cp. below, p. 665). The ratio of free (cerotic) acid to myricin has been found by Hubl and Hehner in a number of well-agreeing experiments as 14 : 86. 1 The bibliography of beeswax, arranged chronologically, and of waxes used in adulter¬ ating it, will be found Jour. Soc. Chem. Ind. 1892, 756. 2 Cp. also Ramboe, Jour. Soc. Chem. Ind. 1897, 150. 3 Brodie, Liebig’s Annalen, 67. 180 ; 71. 144. Schalfejeff, Bericlite, 9. 278 ; 1688. Nafzger, Liebig’s Annalen , 224. 225 ; Schwalb, ibid. 235. 106. Marie, Jour. Soc. Chem. Ind. 1894, 207 ; 1895, 599 ; 1896, 362. 4 Containing about 30-40 per cent of homologous acids (Marie). 3 According to Gascard (Jour. Soc. Chem. Ind. 1893, 955), the myricyl alcohol from beeswax is identical with that from carnaiiba wax, and has the formula C 31 H 64 0. Physical and Chemical Constants of Beeswax 656 ANIMAL WAXES SP H PO O O O O rH cp > > * -■# oo • • CP PQO o®§^?3 S S 2 ^ Observer. Scliaedler Lepage Payen Allen Scliaedler Barfoed Lepage Allen Allen Camilla 7? d ~ -i „ w « to O v r c5 §>§o|? s-S'g g 3*^ !S .2 3^ QWtc io q o c co co cp oo Vo ^ c C C C C C CO SO 50 CP CP CP CP CP CP CP ©P CP * , , , 5 O CO OlOCcbtNOIO^ iO^Q? 1 ? 0 CCOiOCCCOCCUpQQ CP CP CP CP CP CP CP Cp CP ^ ooooooo ooo ”N K CO Dd DQ '—i CO oo CO -GO C 6 IO CP ( m <4 X x oo 00 (M OO 1-H Ah Od X Yellow wax. 2 White wax. 3 Italian waxes not Ligurian. 4 Ligurian wax from Apis Liyustica Spinola. 5 Chemically bleached. XI BEESWAX 657 The proportion of hydrocarbons in wax is, according to Schwalb, 5 to 6 per cent. A. and P. Buisine, however, have found from 12*7 to 13*0 per cent. They further disagree with him by stating that the hydrocarbons belong partly to the ethylene series. Mangold 1 has confirmed Buisine’s results. Beeswax is almost insoluble in cold alcohol, but boiling alcohol dissolves from it the bulk of the cerotic acid and a small quantity- of myricin. The alcoholic solution reddens blue litmus paper- feebly ; a solution of phenolphthalein, made just pink by a trace of alkali, is instantly decolourised by it. On cooling, the cerotic acid separates out in the form of thin needles so completely that the alcoholic solution does not become turbid on mixing with water, a slight opalescence only appearing. Warm ether dissolves beeswax with facility ; on cooling, however, a portion separates out. Nothing is extracted by treatment with sodium carbonate or dilute alkali. By alcoholic caustic alkali wax is completely hydrolysed (saponified). By distilling beeswax with lime an oil is obtained—beeswax oil. 2 Beeswax is very frequently adulterated. Water and mineral matters (such an ochre, gypsum, etc.), also flour and starch, are easily detected. Fraudulent admixture with tallow, stearic acid, Japan wax, carnauba wax, resin, paraffin wax, and cerasin may be detected by the methods described below. Examination of Beeswax for Adulterants As a preliminary test Long 3 recommends the microscopic examina¬ tion of the wax, first dissolving the sample in chloroform, and placing a few drops on an object glass. When the solvent has evaporated partly so that a solid particle is seen, the cover is placed on the wax and the crystals examined after a little time. In the case of pure wax characteristic tufts of crystals are noticed, having the shape of dumb-bells, the spheres of which consist of curved needles. In presence of about 20 per cent of paraffin wax, tallow, or stearic acid, the microscopic appearance is changed completely, paraffin wax seemingly preventing the formation of crystals, whereas in the case of fats and fatty acids the crystals characteristic of the latter are noticeable. Robineaud 4 extracts 1 grm. of the sample with 50 c.c. of cold ether; if less than 0*5 grm. remain undissolved, the wax under ex¬ amination must be considered as adulterated with paraffin wax, tallow, Japan wax, stearic acid, or resin. Vogel, again, agitates one part of the finely divided sample with six or eight parts of chloroform; the undissolved portion should not amount to less than 75 per cent. The surest and quickest means, however, of judging of the purity 1 Jour. Soc. Ohem. Ind. 1891, 861. 2 Liebig's Annalen, 2. (1832) 255 ; Jour. Soc. Ohem. Ind. 1895, 1050. 3 Ohem. Zeit. 9. 1504. 4 Dingl. Polyp. Jour. 163. (1862) 80. 658 ANIMAL WANES CHAP. of a sample (with certain restrictions) is furnished by applying Kott- storfer’s process, in the form recommended specially for the examina¬ tion of beeswax by Hull, Hehner, and Beneclikt and Mangold. This method gives at the same time a clue to the nature of the adulterants. The melting point and the specific gravity of the sample are employed as corroborative tests. In most cases these determinations will be deemed sufficient; but in special cases it may be necessary to estimate also the iodine absorption, the volume of hydrogen obtained on heating the sample with potash-lime, and the proportion of hydrocarbons ( A. and P. Buisine ). 1 If the exact analysis of a yellow wax be required the sample should first be boiled with water and dried, otherwise it may possibly retain small quantities of honey (which, on becoming acid, will affect the acid value) or water—as a rule, from 05 to (P7 per cent. Specific Gravity. —This constant may be determined by Dieterich’s method, as described p. 129. The limits given by this chemist are for pure yellow wax (P962 to 0966 at 15° C., and for pure white wax 0964 to 0"968; Botlger, however, admits for both yellow and white wax as limits 0956 to 0‘964. On account of the difficulties attached to the correct determination of the specific gravity at 15° C., Allen prefers to take it at 100° C. The melting point of pure wax has been given in the foregoing table ; the influence of chemicals (used in bleaching) on this constant will be shown in Buisine’s table (see below). Saponification Process. — Kuttstorfer’s process was employed first for the examination of beeswax by Becker . 2 He saponified 2 grms. of the melted and filtered sample in a flask of 150 c.c. capacity with 25 c.c. of normal to half-normal potash under a pressure of 5 cm. of mercury. A glance at the numbers given by him for various wax¬ like substances shows that mixtures having the normal saponification value may be easily prepared. Substance. Beeswax . Paraffin wax, cerasin Japan wax Carnaiiba wax Spermaceti Tallow Resin Saponification Value. . 97-107 O'O 224-4 931 108-1 196-5 194-3 Consequently the saponification value alone does not prove the purity of the sample. Hubl recommends, therefore, the determination of both the acid value and the ether value of the sample. The ether value (p. 154) gives the number of mgrms. of KOH used for the saponification of myricin. The sum of the acid and the ether values is the saponification value. The following is HubVs process :— 1 Jour. Soc. Chem. Ind. 1891, 52. 2 Zeitsch.f. analyt. Chem. 19. 241. XI BEESWAX 659 Warm 3 to 4 grms. of the sample with 20 c.c. of 95 per cent alcohol in a flask until the wax is melted, distribute the wax by shaking, and titrate with half-normal alcoholic potash, using phenol- phthalein as an indicator, taking care that the wax remains in a melted state during the operation. Then add 20 c.c. of standard alkali, heat for forty-five minutes on the water-bath, and titrate back the excess of alkali with half-normal acid. Of course the saponification value can be also determined in another quantity. The ether value is then obtained by difference (p. 154). The acid value for a number of samples of yellow wax was found by Hiibl from 19 to 21, in most cases 20, and the ether value from 73 to 76, in most cases 75. The higher and lower values occur, according to Hiibl, as a rule, together, so that the ratio of acid value to ether value only varies between 3'6 and 3*8, and the mean 3'7 may be accepted as expressing that ratio. The following table, compiled from HiibVs results and supple¬ mented by those of other observers, gives the numbers for beeswax and substances that may be employed as adulterants : 1 — Substance. 1 Acid Value. 2 2 Ether Value. 3 Saponification Value. 4 Ratio of 1:2. “Ratio number” 5 Observer. Beeswax, yellow 20 75 95 3-75 Hiibl 20-6 76 *5 97-1 3-72 Henriques 3 3 3 3 3 20-4 73-9 94-3 3-58 ,, white 20-6 73-6 94-2 3-6 22-4 76T 98-5 3-41 ,, chemically 24 71 95 2-96 Allen bleached >) 3 3 28-4 76-6 105 2-71 Henriques 3 Carnaiiba wax . 4 75 79 19 Hiibl 33 33 Japan wax 4-8 76 80-84 9-5-19-5 Allen 20 200 220 10 Hiibl 3 3 3 3 * Chinese wax 20 195 215 9-75 Allen Traces 63 63 Spermaceti 33 128 128 Myrtle wax 3 205 208 68-3 Hiibl Tallow 4 191 195 48 Tallow and stearine . 10 185 195 18-5 Allen Stearic acid 195 0 195 Hiibl ,, commercial 200 0 200 Allen Eesin 110 1-6 112 0-015 Hiibl 3 3 180 10 190 0-0556 Allen ,, Austrian . 130-146 16 '4-21 -1 146 *8-167 ‘1 0-126-0-144 Schmidt ,, American. 154T-164-6 29'5-30'0 183 *6-194 0-191-0-182 and Erban Lewko- Galipot . 138 36T 174-6 0-261 witsch Paraffin wax, cerasin 4 0 0 0 1 Cp. also Jour. Soc. Chem. Ind. 1894, 745. 2 See note 2, p. 660. 3 By saponification in the cold. 4 Commercial paraffins or cerasins, however, may have a definite acid value. 660 ANIMAL WAXES CHAP. If wax consisted of cerotic acid and myricin only, the saponifica¬ tion value should be 90‘9, assuming 20 as the acid value. The fact that the number 95 and more has been found proves, in agreement with the above-mentioned researches, that wax must necessarily contain other substances. Hull has drawn from his values, recorded in the foregoing table, the following conclusions :— If the saponification value of a sample of wax be found below 92, the ratio being at the same time that of pure wax, paraffin wax or cerasin must be present. If the ratio is greater than 3‘8, an admixture with Japan wax, carnauba wax or tallow may be suspected. If the acid value is at the same time less than 20, Japan wax is absent. If, however, the ratio is less than 3‘8, stearic acid or resin is present. Hiibl’s results have been confirmed for yellow wax by Allen, Dieterich, and Rottger. Still, Mangold , 1 on examining a large number of undoubtedly genuine waxes, has found a few the ratio of which showed larger 2 deviations. Thus an Hungarian wax gave— Acid Value. 2 Saponification Value. Ratio. 23 90-6 2-89 White wax, especially chemically bleached wax, frequently exhibits greater deviations from Hiibl’s numbers. Thus Allen has found the ratio number 2 - 96, Henrigues 2*71 (see table above), and Buchner 3 3TO. A. and P. Buisine have thoroughly studied the changes yellow wax undergoes on being bleached by various methods. They find the changes in the acid and saponification values very remarkable (cp. also the last table). Thus— Melting Point. Acid Value. Saponi¬ fication Value. Iodine Value. 1 Grm. yields Hydro¬ gen. Hydro¬ carbons. Pure yellow waxes. °C. C3-64 19-21 91-95 10-11 c.c. 52*5-55 Per cent. 13-14 Air-bleaclied waxes, with 3-5 per cent of tallow added. 03-5-64 21-23 105-115 6-7 53-5-57 11-12 Pure yellow wax. 63-5 20-17 93-5 10-9 53 13-5 Same wax air-bleached, with 5 per cent of oil of turpentine added . 63-5 20-2 100-4 6-8 54-9 12-4 Same wax, bleached by hydrogen per- oxide. 63-5 19-S7 98-4 6-3 56-1 12-5 Pure yellow wax. 63 20-40 95-1 11-2 54-5 14-3 Same wax, decolourised by animal char. 63 19-71 93-2 11-4 53-6 13-3 ,, ,, permanganate 63-7 22-63 103-3 2'6 ,, ,, bichromate . 63-5 21-96 99-2 5-8 55-5 13-3 63-2 21-86 98-9 7-9 51 13-2 ” 64 23-43 107-7 1-1 53-6 11-S 1 Jour. Soc. Chert): hid. 1891, 860. 2 A lower acid value, and therefore a higher ratio number, has been given by Wein- wurm ( Chem . Zeit. 1897, 519) for a genuine Silesian wax— Acid Value. Ether Value. Saponific. Value. Ratio Number. 17-8 74-5 92-3 4‘2 Acid values of 25-26 have been observed by the same chemist, due to the artificial combs containing stearic acid. 3 Jour. Soc. Chem. Ind. 1888, 871. XI BEESWAX 661 Hehner, 1 before Hull, employed the same method, but expresses the results in a somewhat different form by calculating from the amounts of alkali used the percentages of “cerotic” acid and myricin, assuming that 1 c.c. of normal KOH neutralises 0410 grm. of free acid, and saponifies 0676 grm. of myricin. The following are his results :— Kind of Wax. Cerotic Acid. Myricin. Total. Wax from Hertfordshire . Per cent. 14-35 Per cent. 8S"55 Per cent. 102-90 3 3 3 3 • • 14-86 85-95 100-81 ,, Surrey 13-22 86-02 99-24 ,, Lincolnshire . 13-56 88-16 101-72 ,, Buckinghamshire 14-64 87-10 101-74 ,, Hertfordshire . 15-02 88-83 103-85 ,, New Forest 14-92 89-87 104-79 ,, Lincolnshire . 15-49 92-08 107-57 ,, Buckinghamshire 15-71 89-02 104-73 Commercial waxes, 8 samples . 13-12 to 15-91 86-73 to 89-58 99-85 to 105-49 Wax from America . 15-16 88-09 103-25 ,, Madagascar 13-56 88-11 101-67 ,, Mauritius 13-04 88-28 101-32 3 3 3 3 • 12-17 95-68 107-85 3 3 J 3 • ,, Jamaica . 13-72 96-02 109-74 13-49 85-12 98-61 3 3 3 3 • ,, Mogadore 14-30 85-78 100-08 13-44 89-00 102-44 ,, Melbourne 13-92 89-24 103-16 3 3 3 3 • 13-18 87-47 100-65 „ Sydney . 13-06 92-79 105-85 >3 33 • • • 13-16 88-62 101-78 The figures given in the last column mostly exceed 100, reaching almost 110; this agrees with Hilbl’s result referred to above, that wax requires more alkali for saponification than the amount found by calculation for a mixture of pure cerotic acid and myricin. Calculat¬ ing from Hehner’s results the ratio of acid and ether values, according to Hull, the number 3'59 is obtained, in satisfactory agreement with HubVs number 3*75. Benedikt and Mangold's Process . 2 —Excellent as the Hubl-Hehner method is, it has the drawback that some kinds of wax are not readily saponified by alcoholic potash. Boiling for half an hour suffices but rarely, in most cases it being necessary to heat on the water-bath until the alcohol has nearly completely evaporated off. 3 If a wax contains cerasin the saponification values obtained are nearly always too low. In fact, the method requires a great deal of practice, so much so, that Benedikt and Mangold have had repeatedly to pro¬ nounce commercial samples of wax pure which had been returned as adulterated by less experienced operators. To avoid these in¬ accuracies, Benedikt and Mangold have recommended the following modifications :— 1 Analyst, 1883, 16. 2 Jour. Soc. Ohem. Ind. 1891, 861. 3 Weinwurm {lx.) completely evaporates tlie alcohol, and states that he thereby easily effects complete saponification. 662 ANIMAL WAXES CHAP. The acid number is ascertained by titration with half-normal caustic soda ; it is, however, advisable to use for the test 7 to 10 grms. of the sample. Instead of the saponification value the “ total acid number” is deter¬ mined, i.e. the number of mgrms. of caustic potash required to neutralise the mixture of fatty acids and alcohols obtained after de¬ composing the previously saponified wax with dilute hydrochloric acid. This mixture, termed conveniently “ decomposed wax,” is obtained by adding 20 grms. of the previously melted wax to a boiling solution of 20 grms. of potassium hydrate in 15 c.c. of water contained in a porcelain dish of 350 to 500 c.c. capacity. The mixture is heated and stirred vigorously for ten minutes, then diluted with 200 c.c. of water, heated again and acidified with 40 c.c. of hydrochloric acid slightly diluted with water. It is then boiled until the fatty layer is quite clear, and allowed to cool. The cake of “ decomposed wax ” is boiled first with water containing some hydrochloric acid, and subsequently twice with water alone. It is then allowed to solidify, taken off, pressed between filter paper, melted in a drying oven, and filtered on to a watch-glass. The solidified mass is conveniently broken up into fragments. 6 to 8 grms. of the “ decomposed wax ” are then treated with neutralised alcohol, heated on the water-bath, and titrated with caustic potash, using phenolphthalein as indicator. Even in presence of large quantities of cerasin the saponification has been found to be complete. The total acid value thus obtained is, of course, a little lower than the saponification value (the “ decomposed wax ” having assimilated the elements of water in the process of saponification). Let s be the acid value, S the total acid number, and a the ether value, then a + s expresses, of course, the saponification value, and we have further 56100 (S-s) “~56100-18 S’ hence 56100 (a + s) " 56100 +18a' Thus, assuming s- 20, the saponification values (a + s) and the total acid values S will have the following corresponding values :— Calculated. Calculated Ob a+s S S a a+s 69 89 87-07 87 68-91 88-91 70 90 88-02 88 69-96 89-96 71 91 88-97 89 71-02 91-02 72 92 89-92 90 72-08 92-08 73 93 90-87 91 73-14 93-14 74 94 91-82 92 74-19 94-19 75 95 92-77 93 75-25 95-25 76 96 93-72 94 76-30 96-30 77 97 94-67 95 77-36 97-36 78 98 95-61 96 78-41 98-41 XI BEESWAX 663 Reasoning as follows, I arrive at a simpler formula for the calculation :— Let the amount of myricin in 1 grm. of wax be x grms., requiring a grms. of KOH for saponification ; in the decomposed wax these x M grms. are represented by ^—— x grms. only, or, since M, the 1V1 + 18 molecular weight of myricin, is 676, by 0*974 x grms. As these 0‘974 x grms. require S - s mgrms. of KOH, and consequently x require S-s Mii' we have S - s : 0 t 974’ hence S = 0 - 974 . The skins that are to be converted into chamois leather are first “ limed,” the hair is then removed by the aid of a blunt dressing knife, and the unhaired hides placed in a “ sour bath,” made of refuse malt and bran, in which they “swell” in consequence of an acid fermentation setting in. The skins are next stretched and well rubbed with whale or cod liver oil, and worked in a fulling machine, so as to become thoroughly saturated with oil. Then the skins are taken out and exposed to the air; and the same process of rubbing with oil and stamping in the stocks is repeated until enough oil has been absorbed, and the skins appear quite dry. In consequence of the exposure to the air, a portion of the oil has been somewhat changed, and has entered into “ combination ” with the fibre, another portion being only mechanically enclosed within the pores of the skin. The “ combined oil ” is that portion of altered fatty matter which cannot be extracted by carbon bisulphide. 1 In order to render the combination of the oil with the fibre more rapid, a fermentation attended with an elevation of temperature is brought about by placing the skins heaped together in a warm room, and covering them well with canvas so as to keep in the generated heat. Overheating, how¬ ever, must be prevented by occasional turning over the pile so as to cool the skins. The oxidation of the oil is completed when the skins have acquired the yellow colour of chamois leather. About 50 per cent of the oil is then found to be left in the uncombined state, and is removed by one of the two following methods :— 1. English (and German) Method. —The skins having been treated for such a length of time that no oil can be removed by pressing or wringing are freed from the excess of oil by scraping with a blunt knife, and then washed with potash or soda lye. The emulsion thus obtained is acidified with sulphuric acid, the fatty matter skimmed off and united with the oil scraped off. This fatty substance forms the sod oil of commerce. Characteristic of the sod oil, in contradistinction to degras, is its high proportion of ash, especially of sulphates, and also the large amount of water and hide fragments (fibres). French Method. —The skins are stocked, aired, and fermented for a shorter period than by the English or German process, so that a large proportion of the oil can be obtained from the skins by throw¬ ing them into warm water and subsequent wringing or pressing in hydraulic presses. The oil thus obtained is the moellon or dbgras of commerce. It contains less ash, less hide fibre, and also less water than the sod oil. The oil still retained by the skins is recovered by washing with alkali, as in the English and German method, and is usually added to the moellon. According to Procter , 2 many English manufacturers have adopted the French process; therefore the sod oil thus prepared should not differ from French moellon. Whereas genuine moellon consists only of expressed oil, a second 1 Cp. v. Schroeder and Paessler, Jour. Soc. Chem. Ind. 1895, 759. 2 Pocket-Book of the Leather Industries Laboratory. Xlt SOD OIL—DEGRAS 695 quality termed “ secunda degras,” or shortly “ degras,” is prepared by mixing genuine moellon with blubber oils or solid fats (such as tallow, palm nut oil, etc.) This product is still included amongst better qualities of degras. In fact, according to Procter , pure moellon is never sold as such but always mixed with tallow and untreated oils ; these admixtures cannot, therefore, be regarded as adulterants. Numerous “substitutes” of degras, or artificial d6gras (“corroine”), occur in commerce, consisting of largely adulterated degras, or of more or less judiciously prepared mixtures of cod, whale, menhaden, sardine, Japan fish oils, blown blubber oils, 1 tallow, 2 resin, oleic acid,, “recovered grease” (p. 686), etc. In order to satisfy the demand for degras, frequently skins are worked simply for its production, being oiled and pressed until not a rag is left. Degras thus prepared must still be considered genuine. Sod oil and degras contain considerable quantities of water, which must not separate out even after long standing. The property of being easily emulsified is due, according to Jean , to the presence of a “ resinous substance ” formed during the oxidation of the oil. The greater the quantity of this substance, the more easily an emulsion is obtained. Thus a sample containing 13 - 9 per cent of the resinous substance yielded with 53 per cent of water an emulsion which had, even after two months’ standing, the appearance of a homogeneous mixture. This “resinous substance” has a brown colour, and melts at 65°- 67° C. It is saponifiable, cannot be precipitated with common salt from its alkaline solutions (difference from fats), is insoluble in water, soluble in alcohol and ether, but insoluble in petroleum ether (difference from resin). According to Jean this substance does not occur in blubber oils, but is formed during the chamoising of the skins. Simand describes this substance under the name “ ddgras-former.” It possesses, according to him, a light brown colour when pure, dark brown when impure. It is easily soluble in alkali and ammonia, and can be readily precipitated from these solutions by addition of acid. It is a little soluble in hot water, especially if slightly acidified, soluble in alcohol, glacial acetic acid, aniline, almost insoluble in ether, and insoluble in petroleum ether and benzene. On heating, it melts, becoming partially decomposed. It occurs chiefly in sod oil and degras, and, according to Simand, also in varying quantities in all marine animal oils. Old and dark oils are said to contain larger quantities of this substance than fresh and pale oils. This, however, is, in the opinion of the writer, open to doubt ; it appears to be an oxidation product (cp. p. 469). 1 Schill and Seilacher have patented two methods for preparing artificial degras by blowing blubber oils with air, or by treating with oxygenated water. 2 Of course, only very low qualities of tallow or waste fats will be used for this pur¬ pose. According to Eitner (Der Gerber, 1890, 145), fish stearine obtained from whale oil or from Japan fish oil is very extensively employed, as the rank fishy odour which persistently adheres to this stearine renders it almost useless for soap-making, etc. 696 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. The “ dSgras-former ” is not found in its free state in d6gras, but is said to occur in it as part of a saponifiable substance sparingly soluble in alcohol, and readily soluble in petroleum ether, in contra¬ distinction to the “ digras-former ” itself. According to Simand the “ dSgras -former ” contains nitrogen. Fahrion, 1 however, has shewn that the “ ddgras-former ” is free from nitrogen, if the hide fragments are removed by suitable treatment. In Fahrion’s opinion the “ digras-former ” is a mixture of hydroxy (oxidised) acids and of their anhydrides. Most sod oils and degras contain unsaponifiable substances originat¬ ing from the marine animal oils used. Thus d6gras prepared from sperm oil is characterised by considerable quantities of cetyl alcohol, and degras from cod liver oil by an oily unsaponifiable mass, origin¬ ally occurring in cod liver oil. The proportion of free fatty acids in sod oils varies very much; their amount, however, does not affect the quality. Sod oil contains, according to Simand, 3-4 per cent of soap, French degras only 049-0 - 73 per cent, calculated in both cases to the anhy¬ drous substance. The large amount of soap in sod oil in conjunction with the leather fibres imparts to it a viscous consistency. The pro¬ portion of leather fibre (hide fragments) should not exceed 5 per cent. The specific gravity of dehydrated degras varies from 0 - 945 to 0‘955 ; it is higher than that of the oils from which it is prepared ; the specific gravity of hydrous degras approaches TOO. An examination of several marine animal oils, according to Livache’s method (p. 285), proved, in satisfactory agreement with practical experience, that the oils that are best suited for the pro¬ duction of d6gras absorb the greatest amount of oxygen. The numbers for the oxygen absorbed have been given p. 287. It will be seen from them that whale oil is most suitable, whereas sperm oil is almost useless. The following table, due to Fitner,' 2 is instructive, as showing the difference between oils and their corresponding sod oils :— 1 Jour. Soc. Chem. I?id. 1891, 558. 2 Der Gerber, 1893, 257. [Table 698 TECHNICAL AND COMMERCIAL ANALYSIS CHA1\- EXAMINATION OF DEGRAS 1. Determination of Water.—5 grms. of the sample are mixed with purified and ignited sand in sufficient quantity to give a solid and nearly dry mass. This is dried at 120° C. and weighed (Jean)} Simand weighs 25 grms. of the sample in a small porcelain basin tared together with a short thermometer serving as a glass rod, adds 50-100 grms. of a blubber or other fatty oil, previously dried by heating to 105 C., and heats to 105° C. with constant stirring, until no more water vapour escapes. The loss in weight, ascertained after cooling, is taken as water. French degras contains, as a rule, 15-25 per cent of water, sod oils from 20-40 per cent (cp. tables below). 2. Fat and Insoluble Matter.—20 grms. of the sample are diluted with petroleum ether, and filtered through a tube closed by a cotton plug* previously dried and weighed. The petroleum ether in the filtrate is distilled off, the residue transferred to a basin, dried at 120 C., and weighed. The insoluble portion left on the cotton wool is also dried at 120 3 C., and weighed. It is then placed in a platinum crucible and incinerated. If a very small amount of ash is left, the insoluble portion consisted of organic matter only, otherwise the residue is weighed and further examined for clay, chalk, gypsum, magnesia, 2 etc. 3. Ash.—5 grms. of the sample are taken for this test. If the ash has an alkaline reaction, it should be boiled out with water, filtered, and the filtrate titrated with standard acid. Simancl weighs off 25 grms. in a platinum dish, and heats it on an asbestos plate, constantly stirring with a glass rod until the water is driven off. The glass rod is then wiped off with filtering paper, which is thrown into the dish and made to serve as a kind of wick for burn¬ ing off the fat. The residue is finally incinerated and weighed. French degras contains but a few hundredths per cent of ash, sod oil as much as 3 per cent. The ash should be examined for iron, as iron in degras is apt to stain the leather. 3 4. Mineral Acids.—If the degras has a strongly acid reaction (mostly due to sulphuric acid), 25 grms. of the sample are boiled with 200 c.c. of water, and, after cooling, the two layers separated by means of a separating funnel. The aqueous layer is made up to a known volume; the nature of the acid is ascertained qualitatively, and an accurately measured volume of the liquor titrated with standard alkali. Schmitz-Dumont draws attention to the possible presence of soluble 1 According to Fahrion, this method gives very erratic results. According to Villon, a syrupy solution of magnesium chloride is extensively used for mixing with degras. 20 per cent of this concentrated solution may be added without being detected by the appearance of the degras or by an abnormal proportion of water. a Simand states that as little as 0'05 per cent of ferric oxide has an injurious action. Addition of 500 c.c. of one per cent oxalic acid solution to 100 kg. of degras is said to remedy this defect. XII DEGRAS 699 fatty acids. Instead of exhausting with ether, as he advises, it would be more expeditious to titrate the mineral acids, methylorange being the indicator, until neutral, then to add phenolphthalein, and to again titrate until the solution becomes pink. 5. Hide Fragments. —The sample is exhausted repeatedly with petroleum ether, and the residue, consisting of water, sand, soap, and hide fragments, washed, first with water and then with alcohol, dried, weighed, incinerated, and weighed again. The difference between the two weights gives roughly the amount of hide fragments. 6. Unsaponifiable Matter. —This is prepared and examined accord¬ ing to the methods described, chap. vii. pp. 217-233. 7. “Resinous Substance.” “Degras-former.” Oxidised Acids. —For the determination of the resinous substance Jean proceeds as fol¬ lows :—The soap solution which has been extracted with ether for the determination of unsaponifiable matter, as under 6, is heated to drive off the ether, and precipitated whilst hot with an excess of common salt. After cooling, the deeply coloured solution is filtered from the separated soap into a flask and hydrochloric acid added. The resinous substance is precipitated in the form of flocks, which unite on boiling the solution, and, on cooling, adhere to the sides of the flask, so that the aqueous liquid may be decanted. The resinous substance is then dissolved in ether, the ethereal solution transferred to a tared porce¬ lain basin, the ether evaporated off, and the residue weighed. Simand determines the amount of the degras-former in the follow¬ ing manner :— 20 to 25 grms. of the sample, according to the proportion of water in the degras, are saponified in an Erlenmeyer flask, provided with a small funnel, with 5-6 grms. of solid caustic soda, previously dissolved in 10 c.c. of water and 50-60 c.c. of alcohol, by boiling for half an hour. The alcohol is then evaporated off, the soap dissolved in water, and the fatty acids liberated by acidulation with hydrochloric acid. The solution is heated until the fatty acids form a clear supernatant layer and the degras-former has coagulated to lumps. After cooling, the acid liquid is poured off from the fatty acids, and, in order to recover a small quantity of degras-former held in solution, neutralised with ammonia, and boiled down. The mixed fatty acids and degras-former are boiled out repeatedly with water, and the washings after neutral¬ isation with ammonia added to the first aqueous liquid. The residue obtained on boiling down is dissolved in a little water, the solution acidulated with hydrochloric acid, and the small quantity of precipi¬ tated degras-former filtered off, washed, dried, and brought into the Erlenmeyer flask, the contents of which have been dried in the mean¬ while at 105° C. The fatty mass is then repeatedly shaken out with 100 to 120 c.c. of petroleum ether, which dissolves the fatty acids whilst the degras-former and small quantities of albuminoid substances remain undissolved. Next the residue is dissolved in alcohol, and the albuminoid substances separated by filtration. The filtrate is boiled down to drive off the alcohol, and the residue, consisting of the purified degras-former, weighed. The petroleum ether washings may be boiled 700 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. down and the fatty acids thus determined. They may be further examined for the melting point, etc. A sample may be considered as pure if it yields at least 12 per cent of degras-former, calculated to a degras of 20 per cent of water. Good samples contain higher proportions of degras-former. The results of Simand’s method are stated to be accurate to 0'5 per cent. 8. Free Fatty Acids. —They are determined in the usual manner (p. 182) by titrating with standard alkali, using phenolphthalein as an indicator. The free fatty acids are calculated to oleic acid. The fatty matter obtained from degras contains, as a rule, 15-19 per cent of free fatty acids. Jean gives the following analyses of samples of degras :— 1 2 3 4 5 6 7 Water . per cent 18-90 14-84 12-93 28-90 19-20 5-39 8-90 Ash . 0-25 0-13 0-55 070 0-07 0-25 1-21 Hide fragments . ,, 0-30 0-30 0-09 0-58 0-27 1-59 Oils . 69-71 74-65 80-00 66-93 75'66 84-87 72-15 Unsaponifiable . ,, 6-84 6-05 Resinous substance ,, 4-00 4-05 5-81 3-52 4-80 9-46 16-15 The folloAving tables give Simand’s analyses of samples of degras and of sod oil:— Degras- former. Melting Point of Fatty- Acids. Soap. Original Degras. Hide Frag¬ ments. Water. Per cent. °C. Per cent. Per cent. Per cent. French degras anhj r drous No. 1 19-14 18-0-28-5 0-73 0-07 16-5 ,, „ „ 2 18-43 28-5-29-0 0-49 0-12 20-5 Sod oil „ „ 3 18-10 3L0-31-5 0-68 0-18 12-0 20-57 33-5-34-0 3-95 5-7 35-0 ,, 18-63 27-5-27-0 3-45 5-9 28-0 ” „ ,, 3 17-84 28-0-28-5 3-00 4-5 30-5 The quantitative reactions, such as saponification and iodine number, have been used by several chemists in the examination of dbgras ; yet they have but little discriminative value. A large quantity of mineral oils is more readily detected by the determination of un- saponifiable matter than by the saponification value. An exhaustive examination of a number of degras, using the quantitative reactions, has been made by Euhsam. 1 His results are given in the following table :— 1 Jour. Soc. C/iem. Ind. 1892, 639. DEGRAS 15 Constant 1 Ether Value (Difference between 13 and 14). OOt^^hOO-jtlOOrH'jtl OOOOCOOtMCOCOO fOrtW COCN'tfCOlM'OCOO -C0C01C 7* 1 14 Constant Saponi¬ fication Value. COiOONC50«pH Ol 03 Ol : O - GO VO 153-2 12 d 0 1$ > An¬ hydrous Degras (Difference between S and 10). 4^- VO 1^ 05) # 05 W H : r- o ^ ^ co : h Q h : : CO CO 00 ^ WCON 70-8 rH rH £ § Original Degras (Difference between 7 and 9) 05 (N CO CO 05 :(M(Mt-hoco : oi ^ : : co zo i>» i>» co vro so 10 d & > o An¬ il yd rous Degras. ^t^CO^OO OO Ol OI (» 9 loo^t^oo I O T— I VO CO co • H H CO CO O • O ^ (M co 7— 1 r—i 1 -H 1 —1 rH t —1 t-H rH t —1 t—| 03 i — i 03 o c3 s *3 o Ch tf CO Original Degras. _I (M O ^ 05 CO *^00 50 : co n co co I co *>• co • * ■ 05 05 ri H 05 * CO H rH * * 00 Acid Value. An¬ hydrous Degras. NN51HN3) _ Oi O rH _ _ A- in o o ci ^ : 00 (N H *1 : : CON rpiO lO CO CUVOO o 1 I Original Degras. 1 J VO CO (N rH ^ # 05 ^ 03 # # o co vo in ^ ; co co i —i * i CO *50 CO ■vr' vO (N^vo co Acety- lated Fatty Acids. hn-^ooinc 5N o^9 COdOOOvOOOOl ■ CO N H 1 >» O 05 CO N N co O 'N wo lO d 15 > Insoluble Fatty Acids. i VO ^ (M VO VO 9 ^ CO CO O O CO VO O OO CO VO CO * G5> 03 CO VO N N N N 05 05 ' N ^ O co l vp oo CO Original Degras. TfiC5(»9000M(NvOVON OVONVOVONCC05NON : COvO^OOCOCOCOCOCOl^tM (N Water. ■+4 °0)«(Nl0!DHMN!Dia : ^ r-H rH t-H i— 1 i—1 rH r— 1 i—1 rH pH ; rH No. of Sample. HOIW^IOIONCOOIOHN Mean of 1-10 102 TECHNICAL AND COMMERCIAL ANALYSIS chap. The samples 1-9 are French artificial degras. No. 10 is a so-called “emulsion fat,” No. 11a moellon prepared by Ruhsam from whale oil No. 12. The acetyl values given in the original paper have been omitted here for reasons given p. 164. Schmitz-Dumont’s figures for a number of degras and commercial products giving high proportions of unsaponifiable matter are con¬ tained in the following table :— No. Dei Moellon, pure Moellon-degras Oxidised blubber oil Oxidised emul¬ sion fat f Degras tc Degras - moel¬ lon o ^ Degras “ Mutton de¬ gras ” Degras - moel¬ lon Degras Fat from sod oil Water. Ash. Insoluble in Petroleum Ether. Patty Matter. Un¬ saponi¬ fiable Matter. Oxidised Acids (Degras- former). Anhydrous Fat. Acid Value. Saponific. Value. Iodine Value. Per Per Per Per Per Per cent. cent. cent. cent. cent. cent. 13-31 0-32 0-31 86-1 3-1 11-03 10S-0 185-S 69 10-05 0-18 0-24 89-5 3-4 14-13 119-0 188-0 52-8 10-24 0-2S 0-2S 89-2 1-0 1-49 104-0 181-8 70-7 8-49 0-06 0-31 91-1 0-91 9-25 34-5 208-5 106-0 17-33 0-27 0-14 82-3 2-51 0-95 29-2 206-0 122-0 10-59 0-20 o-io 89-1 3-1 10-93 112-0 181-2 63-9 1-53 0-70 0-04 97-7 1-85 16-17 112-0 170 62-5 18-45 0-07 0-09 81-4 2-04 11-65 25-7 215-5 89-1 19-88 0-03 0-46 79-63 0-45 1-46 47-4 214-0 115-0 11-65 0-63 0-98 86-74 3-27 2-01 17-4 196-7 126-0 10-43 0-50 0-21 88-86 1-44 1-61 17-0 192-3 129-0 7-45 0-41 0-08 92-1 2-72 9-74 17-0 196-3 107-8 13-S8 0-14 0-22 86-8 40-6 4-06 35-0 99-8 52-9 14-16 0-58 0-97 84-3 18-9 3-73 32-4 137-4 80-6 25-46 0-07 1-25 73-22 14-29 5-99 33-0 206-4 101-8 18-79 0-46 0-31 80-44 23-61 5-33 31-0 135-4 72-3 15-79 0-05 0-22 83-94 28-1 1-84 40-5 113-2 721 7-59 0-26 0-38 91-S 33-12 3-39 39-7 93-0 49-9 16-49 0-31 0-74 82-5 8-5 5-51 39-4 194-0 104-5 14-29 0-29 0-38 85-04 141 4-96 38-4 iso-o 102-0 20-37 0-08 0-45 79-1 40-3 2-95 24-0 86-0 49-5 30-29 0-25 0-22 69-24 2-23 6-55 54-6 201-0 90-0 " 100-0 0-71 16-84 71-3 234-0 61-0 Similar analyses, published by Tortelli, are reproduced here [Table 704 TECHNICAL AND COMMERCIAL ANALYSIS CHAV. Artificial Degras. —Presence of foreign fatty substances in a sample of degras may be suspected, according to Jean , if the specific gravity of the separated fatty matter is lower than 0‘920, genuine samples of degras having a specific gravity of 0‘945-0‘955, and accord¬ ing to Tortelli (see table) about 1 - 0. Tallow may be detected by the high melting point of the mixed fatty acids of degras, as will readily be seen from the following table :— Melting Point. °C. above 40 Mixed Fatty Acids from Tallow Whale oil Cod liver oil Japan fish oil 24-9 18-5 30-8 Hydrocarbons and resin in a degras are detected by examining the fatty matter according to the directions given in chaps, vii. and viii. pp. 217, 234. The estimation of wool grease or distilled grease is, in the present state of our knowledge, not yet possible. Detection of cholesterol is not sufficient proof of their presence, since fish and liver oils contain notable proportions of this alcohol; but the appearance of a green fluorescence would point to the presence of isocholesterol and in- ferentially to that of wool grease or of distilled grease. Raw wool fat would most likely escape complete saponification, and part of the waxes would pass into the unsaponifiable portion. By again saponi¬ fying the latter, preferably under pressure, a definite saponification value would point to the presence of wool wax. A very rough approximation of the quantity of the adulterant may be obtained by isolating the cholesterol in the form of its acetate (see p. 231). “ Corroine,” an artificial degras, is stated to consist of a mixture of vaseline and wool fat emulsified with water. 1 Another artificial d6gras is made by heating blubber oils to 120° C. and blowing air through. D. WOOL OILS—CLOTH OILS 2 Under the trade term wool oils or cloth oils are comprised all those oils that are used by woollen manufacturers for lubricating the wool before spinning, or for oiling the rags before grinding and pulling. The wool oils may be conveniently subdivided into three classes (a) fatty oils, including fatty acids ; (b) emulsified oils; ( c) solutions of soap. The following is a list of the fatty oils used in the woollen industry, arranged in the order of their suitability and quality, com¬ mencing with olive oil, which is used for best qualities of wool, and ending with oils consisting in great part of unsaponifiable matter :— 1 Jour. Soc. Chem. Ind. 1895, 815. 2 Cp. Lewkowitsch, Jour. Soc. Dyers and Colourists , 1896, 60 ; Jour. Soc. Chem. Ind. 1896, 459. XII WOOL OILS—CLOTH OILS 705 Olive (Gallipoli) oil, lard oil, neat’s foot oil, oleine (= oleic acid) [saponification or saponified oleine, distillation or distilled oleine], dis¬ tilled grease oleine, black recovered oil, “seekoil,’’and brown [grease] oil. Emulsified oils are largely used on the Continent; they are prepared from neutral oils, oleic acid, and aqueous ammonia or a solution of sodium carbonate, or, in other words, they consist of oil and oleic acid emulsified by a soap solution. • Solutions of soap are represented by concentrated solutions of castor oil soap or a neutral alkali salt of sulpho-ricinoleic acid. The tendency for cheap wool oils has led to the production of a large number of “manufactured oils,” which represent mixtures (“blends”) of the above-named wool oils with mineral oils. Before discussing the several wool oils we may broadly lay down the principles upon which the analysis and valuation of wool oils has to be based. Wool oils should be easily removable in the scouring , they should therefore be free from drying-oils (or their fatty acids) and reunify¬ ing substances (resin acids), as these offer great resistance to their removal in the scouring process, become sticky, leave an unpleasant odour on the fabric, and cause stains in the finished cloth. Even small quantities of hydrocarbons in the oils for finer goods are objectionable. Although the mineral oils readily form emulsions with soap solutions, practical experience shows that they are not so easily removable as one might anticipate. Therefore, for best goods wholly saponifiable wool oils should be used. The low class oils contain large proportions of hydrocarbons, but they can be removed with comparative ease, as in the manufacture of the goods for which these oils are employed strongly alkaline soaps are used. 1 2 Wool oils should develop as little heat as possible both in the stored raw material and during the working of the oiled material. Drying and even semi-drying oils may easily give rise to a development of heat sufficient to cause spontaneous combustion. Heat may be also produced in the scribbling and carding process, and the action of free fatty acids on the metal of the scribblers must be taken into account. Therefore the flash point and in general the liability of an oil to cause a fire , or to favour the spreading of it, is of the greatest commercial importance. This point will have to be considered especially by the analyst, as the fire insurance offices put great strictures on the users of wool oils, assessing as they do the insurance premium according to the quality of the oil. It may therefore be found useful in this connection to quote the order in which the schedules of the fire insurance companies in this country arrange the oils :— Free from any extra charge are —Olive (Gallipoli) oil, lard oil, oleine (“saponified” or “distilled”) not containing more than 10 per cent of unsaponifiable matter, fish oil, or a manufactured oil (“purified 1 Cp. Lewkowitsch, Jour. Soc. Dyers and Colourists, 1894, March ; Jour. Soc. Chem. Ind. 1894, 258 ; Jour. Soc. Dyers and Colourists , 1896, 60 ; Jour. Soc. Chem. Ind. 1896 459 ; and Spennrath and Walther, Jour. Soc. Chem. Ind. 1895, 362. * 2 z 706 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. by distillation or saponification,” whatever this may mean) containing not more than 30 per cent of unsaponifiable matter, 1 and having a flash point of not under 340° F. (167'8° 0.) A higher rate is charged for —Manufactured oils containing more than 30 per cent, but not more than 50 per cent, of unsaponifiable matter. A still higher rate is charged for —Black (recovered) oil (p. 693), containing not more than 50 per cent of unsaponifiable matter. The highest rate is charged for —Manufactured oils containing more than 50 per cent of unsaponifiable matter, or mineral oil, oil of pine, linseed oil, rape oil, cotton seed oil, or any other seed oil. Neat’s foot oil and tallow oil are not mentioned in these schedules, although they are very useful wool oils and quite harmless, whereas, curiously enough, fish oil is permitted free of extra charge; yet cotton seed oil, which is equally dangerous, is placed amongst the oils charged at the highest rate. Nor has regard been taken of the fact that the permission to use fish oil offers an opportunity for adding cotton seed oil with impunity. Although mineral oils in themselves are not liable to spontaneous combustion, still experience has shown that once a fire has broken out, they cause a rapid spreading of it; it is for this reason that strictures are laid on extensive use of mineral oils. Therefore the determination of the unsaponifiable matter and of the flash point are of the greatest importance in the analysis of wool oils. The methods for the determination of the unsaponifiable matter have been detailed above (p. 218). Some analysts ascertain the “ saponifiable ” 2 by boiling with alcoholic potash (p. 151), and calculating the amount of KOH used to oleic acid, then obtaining the “unsaponifiable matter” by differ¬ ence. 3 This method should be rejected as leading to erroneous results in many cases, and the unsaponifiable matter should be deter¬ mined direct by extraction. Another error committed by some analysts is to return the “ un¬ saponifiable matter ” as mineral oil, a misnomer which may lead to great inconvenience to the user of the oil. If neutral oil be required besides free fatty acid, it is determined as described p. 752. The flash point is determined by heating 50 c.c. of the oil under examination in a porcelain basin (“ open test ”), constantly stirring with a thermometer, and from time to time bringing a small flame towards the surface of the oil. That temperature is noted as flash point when there is a slight explosion or “ flash.” Of course, any other apparatus may also be used (cp. “Lubricating Oils,” p. 716). The flash point should not be below 170° C. (340° F.) A rapid method for the determination of the liability of wool oils to spontaneous combustion is afforded by using Mackey’s “Cloth Oil Tester.” 4 1 The Austrian fire insurance companies allow only 15 per cent of unsaponifiable matter. 2 J.e. the sum of the neutral fat and free fatty acids. 3 Cp. Lewkowitsch, Jour. Soc. Cliem. Ind. 1892, 142. 4 Supplied by Reynolds and Branson, Leeds. XII WOOL OILS—CLOTH OILS 707 This apparatus is illustrated by Fig. 45, and consists essentially of a cylindrical metal water-bath, provided with a lid having a nozzle for inserting a thermometer, and fitted with two tubes A and B for air currents in the directions of the arrows. Inside the apparatus is placed a cylinder C of wire gauze, containing a ball of cotton wool oiled with the sample under examination. In testing proceed as follows :— Weigh out 14 grms. of the sample into a shallow dish containing 7 grms. of pure cotton wool. Tease out carefully the cotton wool by hand, so that the oil is thoroughly distributed throughout the mass. This teasing and incorporation of the oil with the cotton cannot be I A Fig. 45. done too carefully, as much of the success of the experiment depends on the even distribution of the oil. Transfer the oiled cotton wool to the cylindrical cage C, holding the thermometer in its place, while the cotton wool is packed around it. Bring the water in the jacket to vigorous boiling, place the cage in the bath, slip the lid down over the stem of the thermometer, and fix it in its place 1 by means of the clamp D. Keep the water in the bath boiling, and note the tempera¬ ture after the lapse of one hour. Care must be taken that no moisture enters the bath. 1 The thermometer provided with the apparatus bears a red mark on the stem ; it should be so fixed that the red mark is just visible. 708 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. If the thermometer registers over 100° C. at the end of the first hour, the oil under examination must be considered as dangerous. In the case of very dangerous oils the temperature will run up to 200" C. within one hour and a half. If the temperature rises very rapidly above 150° C. it is best to withdraw the thermometer, as the oiled cotton wool may fire. The following table gives a number of tests i 1 — No. Oil Used. Tempera¬ ture in 1 hr. Tempera¬ ture in 1 hr. 15 m. Tempera¬ ture in 1 hr. 30 m. Tempera¬ ture in 2 hrs. Maximum. 1 Cotton seed. °C. = °F 125 = 257 °C. = °F. 242 = 46S °C. = °F. ”C. = °F. °C. = °F. H. M. 242 = 468 1 15 2 . 121 = 250 242 = 468 2S2 = 540 284 = 543 1 35 3 128 = 262 212 = 414 225 = 437 225 = 437 1 30 4 ,, ,, ...... 124 = 255 210 = 410 24S = 478 1 35 5 116 = 241 192 = 378 200 = 392 200 = 392 1 30 6 . 118 = 244 191 = 376 202 = 396 202 = 396 1 30 7 . 117 = 243 190 = 374 194 = 381 194 = 381 1 30 S Olive fatty acids. 112 = 234 177 = 351 204 = 399 211 = 412 1 45 9 114 = 237 177 = 351 196 = 385 1 25 10 ,, ,, . 105 = 221 165 = 329 293 = 559 1 55 11 White Australian olein . 102 = 216 135 = 275 208=406 226 = 439 1 45 12 103 = 217 115 = 239 191 = 376 230 = 446 1 45 13 Olive (containing 1% free fatty acids) . 98 = 208 102 = 216 104 = 219 241 = 466 3 25 14 Oleine . 98 = 208 101 = 214 102 = 216 110 = 230 2 8 15 97% oleine . 98 = 208 100 = 212 102 = 216 172 = 342 3 15 16 Belgian oleine . 98 = 208 99 = 210 100 = 212 173 = 343 3 16 17 Olive (neutral) . 98 = 208 100 = 212 101 = 214 235 = 455 5 15 IS ,, ,, ...... 97 = 207 100 = 212 101 = 214 228 = 442 4 30 19 Cotton . 97 = 207 101 = 214 235 = 455 4 55 20 139 = 282 200 = 392 1 4 21 Olive . 99 = 210 101 = 214 102 = 2i6 103 = 217 113 = 235 4 30 22 Mixture of 50% of No. 20 and 50% of No. 21 . 102 = 216 117=243 200 = 392 1 29 23 ,, 25 ,, „ 75 ,, 99 = 210 105 = 221 R2 = 234 200 = 392 1 52 24 ,, 10 „ „ 90 „ 99 = 210 102 = 216 305 = 221 127 = 261 200 = 392 2 9 The method described being a comparative one, the directions given must be strictly adhered to if comparable results are to be expected. It will be found useful before examining the sample to test, say, olive oil and cotton seed oil, as representing a safe oil and a dangerous oil respectively. The writer has worked with this “Cloth Oil Tester,” and can recommend it as a very useful instrument, much simpler than the apparatus described by Richards . 2 The latter consists of an outer shell formed by a six-inch wrought iron tube, which can be closed at each end by discs of wood. Into this tube is inserted an inner four-inch tube of sheet-iron, with overlapping metal covers at each end. Thus there is left an air space of one inch around the inner tube and of three inches at each end. The whole apparatus is conveniently placed on a tripod, and heated by a Bunsen burner. Three thermometers, which are inserted into the inner shell through the outer one, allow the temperature to be read. To test an oil, 50 grms. are evenly distributed over, say, 50 grms. of cotton waste, and the waste carefully pushed into one end of the 1 Mackey, Jour. Soc. Chem. Ind. 1896, 90. Similar but very rough experiments were made before him by Gellatly (1874) to test the liability to spontaneous combustion of lubricating oils. Cp. also Kissling, Jour. Soc. Chem. Ind. 1895, 479. 2 Jour. Soc. Chem. Ind. 1892, 547. XII WOOL OILS—CLOTH OILS 709 inner tube, and a thermometer inserted into the middle of the ball. A second ball of unoiled waste is placed similarly at the other end of the tube. On heating, the thermometer inserted into this blank waste should not rise above 100°-101°C.; this can be easily con¬ trolled by the readings of the middle thermometer. The latter should be kept at about 125° C. The results obtained by means of this apparatus are stated to have been of the greatest use for determining the cause of fires and for gauging the degree of safety of oils. For instance, the percentage of fatty oil which may be safely mixed with mineral oil was easily determined. The experiments showed that neat’s foot oil and best lard oil may be mixed with mineral oil to the extent of 50-60 per cent, while in the case of cotton seed oil the limit of safety is reached at 25 per cent. Olive oil and lard oil may be examined as detailed in the pre¬ ceding chapter (pp. 451, 584), especially with a view to detecting admixture with seed oils and mineral oils. The examination of oleic acid will be described p. 765. It should be tested chiefly for unsaponifiable matter and linseed oil fatty acids. Distilled grease oleine (p. 691), as also all the other manufactured oils—black (recovered) oil (p. 693), “seek oil” (p. 693), brown (grease) oil (p. 686), are tested for unsaponifiable matter. 4 he unsaponifiable matter should not be returned as mineral oil, without the detailed examination warranting such a statement. Even if the unsaponifiable matter be liquid and fluorescent, it may consist of hydrocarbons formed by destructive distillation of wool fat. 1 In the latter case, the unsaponifiable matter will show the isocholesterol reaction (p. 86), and the molecular weight of the fatty acids will be found considerably higher than 282, the molecular weight of oleic acid. As the fire insurance companies charge according to the amount of unsaponifiable matter, resin is now added fraudulently. This is detected and determined in the saponifiable part ( i.e . soap solution) as described chap. viii. p. 235. Emulsion wool oils are tested for soda or ammonia (cp. “ Turkey- red Oil, p. 726); the oily substance is separated by a mineral acid, and examined for “ saponifiable ” and “ unsaponifiable.” In order to produce a more complete emulsion, occasionally gum or gelatin-like substances have been added. They are detected by adding alcohol, which precipitates these adulterants. The following table (p. 710) contains the analysis of several emulsified oils. A number of analyses of lower class wool oils are given in the following table (p. 711); it has not been considered necessary to add any analyses of olive and lard oils. The oleines given below (p. 767) are, of course, also suitable for oiling wool. Cp. Lewkowitsch, Jour. Soc. Chem. Ind. 1892, .142. The importance of this question with regard to insurance risk has been clearly stated in a paper by Mackey, read before the Insurance Institute of Yorkshire. Cp. The Textile Manufacturer, 1894, 18. J Analyses of Wool Oils 712 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. E. LUBRICATING OILS A good lubricating oil should fulfil the following conditions :— 1. It should diminish friction. 2. It should not lose its lubricating power on exposure to the atmosphere. 3. It should have no deleterious chemical action on the metal surfaces. 4. It should possess a sufficient degree of viscosity, so that it is neither squeezed out between the moving surfaces, nor wasted by rapid motion of the running machinery. In other words, the lubricant should have just sufficient viscosity to keep the moving surfaces apart under the maximum pressure. 1 5. It should not give off combustible gases or vapours at the temperature it is heated to in practical use. 6. It should be free from grit and suspended matter. The following are used as lubricants :—Fats and oils (as tallow, lard oil, tallow oil, sperm oil, olive oil, rape oil), mineral oils, and mixtures of fatty and mineral oils. Resin oils are unsuitable on account of their liability to “ gum,” and their presence in lubricating oils must, therefore, be considered as an adulteration. Solid lubricants are mixtures of fats, fatty oils, and mineral oils, solidified by sodium carbonate, lime resinate, soaps, etc. For very heavy work pitches (pp. 692, 755) are employed as the most suitable lubricant. “Dead” tar oils were used formerly for adulterating lubricating oils ; but owing to the cheapness of mineral oils they are now but rarely met with in lubricating oils. For purposes of valuation it is necessary to determine the follow¬ ing physical constants of a lubricating oil: (1) the specific gravity (p. 123), (2) the viscosity 2 (p. 103), (3) the freezing point (p. 135), 1 Cp. B. Redwood, Jour. Soc. Chem.Ind. 1886, 121 ; Lew, ibid. 1891, 777 ; Kiinkler. ibid. 1891, 1014. 2 Petroff ( Grossmann Die Schmiermittel, pp. 42-49) determines the internal friction of oils, i.e. the absolute viscosity. The following table shows the co-efficients of internal friction at different temperatures for some lubricating oils :— Tempera¬ ture. Sperm Oil. Olive Oil. Palm Oil. Mineral Oil (Ro- gosine). Mineral Oil. Mineral Oil. Mixed Cylinder Oil. 0-884 at 0-955 at 0-903 at 0-885 at •900 at 9-918 at 0'922 at °c. 19° C. 18° C. 17° C. 18° C. 18° C. 18° C. 1S° C. •20 0-00300 0-00845 0-09900 0-00237 0-03034 0-08360 0-28500 0-000103 30 0-00246 0-00541 0-04636 0-00152 0-01530 0-03800 0-08930 0-000082 40 0-00177 0-00361 0-02331 0-00102 0-00844 0-02070 0-04240 0-000066 50 0-00132 0-00257 0-01306 0-00069 0-00504 0-01180 0-02250 0-000051 60 0-00107 0-00190 0-00777 The conclusion Petroff draws from his observations are the following :— At a given temperature the order of the oils regarding their internal frictions is the same as their lubricating power and their viscosity, as ascertained in the usual manner. The absolute viscosity of oils diminishes rapidly with increase of temperature. XII LUBRICATING OILS 713 “ cold-test, t i.e. liability to thicken in the cold, if the lubricant should be used at low temperatures. With regard to test (1) it may be pointed out again, that the specific gravity has little or no value in relation to the lubricating value of an oil, and serves, therefore, chiefly to direct attention to adulteration. The freezing point or “ cold-test ” may be determined by the methods given above (chap. v. p. 135.) The “ cold-test ” is not of such great importance in this country as in the United States and on the Continent, where the danger exists of damage to machinery being done by oil becoming solid in the lubricators. In these countries the specifications of the railway companies fix, therefore, the temperature at which the lubricating oil must remain fluid. According to the directions of the New York Produce Exchange the sample to be tested is poured into a beaker 4 in. deep by 3 in. in diameter until nearly filled. The beaker is immersed in a freezing mixture, the temperature of which is controlled ,by a fixed thermometer; and a second thermometer is immersed in the oil, reaching half way down the beaker. When both thermometers register the same temperature (viz. the specified cold-test), the oil must still flow on inclining the beaker. It should be noted that the oil is not stirred, and that thus the conditions obtaining in practice are simulated although the factor of the length of time is neglected. More complicated than the American test is the cold-test prescribed by the Prussian State Railway Direc¬ tion. According to their rules winter oil must remain fluid at - 15° C. This is considered to be the case if the oil, cooled to - 15° C., and subjected to the constant pressure of a water column of 50 mm., will rise in a glass tube of 6 mm. internal diameter at a minimum rate of 10 mm. per minute. The apparatus adopted for this test (made by G. A. Schultze, Berlin), is far too complicated for so simple a determination. Railway companies and other large consumers of lubricants test the lubricating value by means of specially designed apparatus, simu¬ lating as nearly as possible the conditions obtaining in practice. As to the value of these tests, and a description of the apparatus, the reader must be referred to the sources given in the footnote. 1 Chemical tests have for their object the determination of the liability to “ gum ” or resinify and to spontaneous combustion, the flash point, ignition point, loss by evaporation, origin, and purity. Liability to “ gum.” —A good lubricant should neither dry on exposure nor “gum” (causing, in the first instance, more fuel to be consumed in consequence of the drag upon machinery), nor have a tendency to become acid. A practical test for ascertaining the liability of a lubricating oil to gum may be made in the manner 1 Redwood, Jour. Soc. Cthem. Ind. 1886, 121; Cameron - Leask, Soaps and Candles, pp. 258-313 ; Thorpe’s Dictionary of Applied Chemistry, vol. ii. p.474 ; Thurston, Treatise on Friction and Lubrication, pp. 248-263 ; B. Redwood, Petroleum, p. 634 ; Goodman, Recent Researches in Friction; Proc. Inst. Civil Engineers, vol. 85. 714 TECHNICAL AND COMMERCIAL ANALYSIS CHA1>. proposed by Nasmith and Albrecht, by placing at the same time equal quantities of oils to be compared on an inclined plane. 1 The oil flowing for the longest time will be the best ; bad oils cease to flow after a few days, becoming thick or “ gummy.” A table containing a few results obtained in that fashion, given in Appleton’s Dictionary of Mechanics, is reproduced here :— Lubricant. Run of Oil in Inches after Days. 1 2 3 4 5 6 7 8 9 Sperm oil, best 32 50 53'5 54 54 54 54 54 Sperm oil, com. 19 45 55 59 62 64 67 67-5 68 Olive oil, Gal- 1 lipoli . / Lard oil 10 14 18 18'5 19-5 20-5 21 21-25 21-5 10-25 10'5 1075 1075 11-75 still Rape oil 14 18 19 19 19-25 19-25 1975 still Linseed oil 17'5 18 18 18'25 18-5 still 0. Bach, 2 adopting a method originally proposed by Fox, estimates the capacity for absorbing oxygen as a measure of the liability to gumming or becoming acid. A known quantity of oil is heated for ten hours with oxygen in a sealed tube, of about 100-125 c.c. capacity, in an air-bath at a temperature of 110''’ C. The point of the tube is then broken under a measured volume of water, and the absorbed oxygen found from the difference in volume. The presence of excess of oxygen after the experiment must be ascertained in the usual manner with a glowing splinter of wood. The following are Bach's results :— 1 Grm. of Absorbed Oxygen, c.c. “Valve’’oil . . . . . 0T0 “ Valvoline ” oil ...... 0"45 “ Refined cylinder ” oil . . . . . 0’34 Mineral oil, Russian . . . . .074 “Lubricating oil,” sp. gr. 0'877 .... 070 „ ,, ,, 0-865 .... 4-80 90 parts “lubricating oil,” with 10 parts of “cod oil” 3 . 9'40 90 ,, “ oleonaphtha ” ,, ,, ., ,, . 8'60 “ Cod oil,” 3 sp. gr. 0'963 ..... 76'30 Resin oil ....... 181'00 Olive oil . . . . . • 144'00 Rape oil . . . . . . 166'00 Cotton seed oil . . . . . . Ill'00 More convenient comparative tests for the drying power are un¬ questionably afforded by the determination of the iodine value 1 Cp. Daw. Chem. News, 1894 [70], 42. 2 Jour. Soc. Chem. Ind. 1889, 990. 3 This is a trade term for redistilled resin oil. XII LUBRICATING OILS 715 (p. 170), the rise of temperature in Mailmen# s test (p. 291), and the oxygen absorption determined by placing a weighed quantity in a watch glass and ascertaining the increase in weight after exposing to, say, 100° C. for twelve to twenty-four hours. Of course, it is necessary to work with perfectly dry oils. The oxygen absorption may also be determined by Livache’s method. As the oils exhibiting a pronounced tendency to gum are those liable to spontaneous combustion, the value of a lubricating oil under this head may be determined by means of the “ Cloth Oil Tester ” (see p. 707). The flash point is determined by the “open test,” as already described for wool oils (p. 706). This method is sufficiently accurate for practical purposes, it being only necessary to ascertain whether the oil is dangerous or not. Oils containing even small quantities of water give, according to Holde, 1 very irregular values for their flash points. The presence of moisture may be recognised by heating the sample in an oil - bath to 140 C., when at about 120° C. frothing or even bumping will be noticed. In such a case Holde dehydrates the oil by shaking with calcium chloride and allows to stand for twenty-four hours. The lowest value for the flash point by the “ open test ” should be about 175° C. (350° F.) for lubricating oils, and about 260° C. (500° F.) for cylinder oils. The following table gives Hunkier’s 2 observations on a few lubricating oils, comprising mineral and fatty oils :— Oils. Spec. Grav. at 17-5° C. Flash Point °C. Viscosity (Engler) At 50° C. At 100° C. Russian cylinder oils 0-911-0-923 183-238 10-2-16-2 2-0-2-8 ,, machine oils 0'893-0-920 138-197 5-8-6-3 1-5-1-8 ,, spindle oils 0-893-0-895 163-167 3-1-3-4 l'4-l-5 American cylinder oils 0-886-0-899 280-283 4-1-4-8 ,, machine ,, 0-884-0-920 187-260 4-2 1-6 ,, spindle ,, 0-908-0-911 187-200 3T-3-3 1-4-1-6 Rape oil, crude 0-920 265 4-0 1-7 ,, ., refined 0-911 305 4-9 2-0 Olive oil ... 0914 305 3-7 1-8 Castor oil 0-963 275 16-4 3-0 Linseed oil 0-930 285 3-2 1-7 Tallow .... 0-951 265 5-2 2-5 It will be seen from this table that mineral oils suffer a greater loss in viscosity with increase of temperature than fatty oils. When greater accuracy is required than is furnished by the “ open test,” the adoption of “ close test ” apparatus is necessary. In this country Gray’s flash-point apparatus is used for this purpose. Gray’s apparatus 3 is illustrated by Fig. 46. It consists of a 1 Jour. Soc. Cliem. Ind. 1889, 735. 2 Ibid. 1890, 197. 3 Supplied by Baird and Tatlock, 14 Cross Street, London, E.C. 716 TECHNICAL AND COMMERCIAL ANALYSIS chap. brass oil cup, A, of 2 in. diameter by 2 T 2 Tr in. in depth, and has, there¬ fore, the same dimensions as the Abel Petroleum Tester. The height to which the cup is to be filled is indicated by a line cut round the inside; it runs 1| in. from the bottom. The cup is closed by a tightly fitting lid, through the centre of which a steel shaft passes to the bottom, carrying two sets of stirrers, one above and the other below the surface of the oil. On the top of the steel shaft there is fixed a small bevelled wheel, H, with milled edge, and geared with a vertical bevelled wheel, G, actuated by a small handle, B. Thus the stirrers are set in motion. The lid is provided with four openings, one of which serves for the insertion of a ..g thermometer, whereas the other three provide means for producing the flash. These three orifices are, as a rule, closed by a loose flat cover, S, provided with openings which, when the cover is turned one quarter round, coincide with the ports in the fixed lid. One of the latter is immediately in front of the test-lamp, D, which can be tilted whenever required, whereas the other two ports, one on each side, admit air to produce the explosive mixture. To perform the test, fill the cup to the mark with the sample, light the test- lamp and adjust the flame to about -| in. in size. Then heat the oil cup by means of a Bunsen burner or a sand-bath, whilst rotating the stirrers, so that the temperature of the oil rises about 5° C. per minute at first, but less when the point is reached at which the oil is expected to flash. Whilst the bevelled wheels are in gear the sliding cover is held in its normal position by the spring P. Then draw the horizontal shaft, which has a little lateral play in its bearings, slightly to the right, whereby the stirrers are thrown out of gear. Turn the handle a quarter of a round, when the loose cover is rotated, the ports opened, and at the same time the test-lamp tilted into the opening. Reverse the handle immediately, whereby the ports are closed automatically. If a slight explosion was pro¬ duced, note the temperature; this is the flash point of the oil. If no flash was produced, continue the heating ; throw the stirrers into gear, and proceed as before. The following table gives a number of flash points, 1 together with some other constants :— 1 Cameron-Leask, pp. 263-291. XII LUBRICATING OILS 717 Flash Specific Viscosity at Point. Close Cold Test. Gravity Test. Remarks. at 60° F. 70° F. 120° F. 180° F. °F. °F. Refined Mineral Oils — Standard for Viscosity. Sperm Oil at 70° C. = 100 Scotch .... 0-890-0-895 100-130 40-50 320-350 32 0-885-0-890 75-100 35-40 300-325 32 0-ST5-0-880 50-60 25-30 300-325 32 American .... 0915-0-920 400-425 90-100 35-40 375-425 32 0-905-0-910 200-225 55-65 350-400 32 0-885-0-890 75-100 35-40 325-350 32 0-875-0-880 65-75 30-35 325-350 32 Russian .... 0-910-0-915 1200-1500 200-250 50-70 400-425 25 0-905-0-912 700-800 125-150 45-50 350-375 25 0-895-0-900 220-250 60-65 325-350 15 0-895-0-900 125-175 300-325 10 Natural (dark) Mineral Oils— Standard for Viscosity. Tallow at 180° C.=100. American summer, dark . 0-890-0-895 250-300 70-75 400-425 40-50 ,, medium 0-880-0-885 550-700 110-125 40-50 350-400 25-30 ,. winter 0-880-0-885 350-400 90-100 35-40 325-375 25-30 Russian residuum 0-910-0-915 750-1000 150-200 45-60 250-300 25-30 Natural and Filtered Mineral Oils — American heavy dark 0-900-0-905 1750-2000 350-400 500-550 40-45 ,, extra dark. 0-900-0-905 2000-2500 400-450 525-575 35-40 ,, medium dark . 0-895-0-900 1200-1400 300-350 500-525 40-45 ,, heavy filtered . 0-890-0-895 1400-1500 300-350 500-550 60-70 ,, medium filtered 0-890-0-S95 1000-1200 250-300 500-525 65-70 „ light filtered 0-8S5-0-890 885-1000 200-250 450-500 75-80 ,, fluid filtered 0-885-0-890 1200-1400 300-350 500-550 40-45 » 0-8S5-0-890 900-1000 225-275 450-500 45-50 No. of Flash Samples Points Southern sperm oil 0-8807 100-1 45-4 457-5* 41-7 34 420-485 Arctic sperm oil 0-8S04 105-3 47-2 446-2* 39-2 59 390-485 White whale oil 0-9207 1S7-7 71-3 476-0* 27-2 35 430-530 Neat’s foot oil. 0-9170 247 82-4 470-3* 34-4 17 410-540 Lard oil. 0-9172 223-2 79-4 493-9* 39-6 18 425-545 Olive oil. 0-9167 213-2 75-0 437-5* 27 24 410-465 Rape oil, East India, refined. 0-916 250-4 88-1 478-6* 26-4 89 410-510 ,, Black Sea, refined . 0-9209 226-9 78-8 465-4* 27 25 430-490 Cotton seed oil, refined . 0-9235 190-4 69-S 523 * 30 22 500-540 Castor oil .... 0-963 2500 390 487 * 0 * Mean values. In Germany the Abel-Pensky-Martens apparatus is used, 1 as also the Treumann open cup. 2 The ignition point is determined, according to Martens, by filling a crucible of about 40 mm. diameter, and 40 mm. high, within 5 mm. of its brim, and embedding it to half its height in a sand-bath. The crucible is heated at first rapidly until the flash point has been reached, then the gas-burner is turned low and the temperature allowed to gradually rise 10°-15° C. above the flash point; after every rise of 2° C. a small flame is approached to the surface until the oil burns 1 Jour. Soc. Ghem. Ind. 1889, 736. 2 Ibid. 1895, 284. 718 TECHNICAL AND COMMERCIAL ANALYSIS chap. calmly. The crucible must be protected from draught by a convenient arrangement. As we subdivide here for the sake of convenience the lubricating oils into (1) Fatty oils and liquid waxes, (2) Mineral oils, (3) Mix¬ tures of (1) and (2), (4) Solid lubricants, other tests will be mentioned under the separate heads. 1. Fatty Oils and Liquid Waxes The most important fatty oils used for lubricating are tallow oil, lard oil, neat s foot oil, olive oil, rape oil, castor oil; less important are whale and seal oils, latterly also porpoise and blackfish oils are being employed. Ihe liquid waxes are excellent lubricants, and are almost exclusively used as such. Apart from the conditions laid down above, the suitability of these oils is determined by their action on metals when in contact with them under approximately the same conditions as obtain in practice. Experiments made by I. J. Redwood 1 have established the following facts :—Iron is acted on by tallow oil the most, and by seal oil the least. Bronze was not attacked at all by rape oil, and but very slightly by olive oil; it was, on the other hand, vigorously corroded by cotton seed oil. Copper was not attacked by any of the mineral oils j sperm oil had the least and tallow oil the most action on it. In the case of lead, the most deleterious lubricant was whale oil \ the best, olive oil. Whale, lard, and sperm oils were about equally corrosive. For zinc the best oil was lard oil, and the worst sperm oil. The experiments were carried out in the following manner :_The metals were first thoroughly cleaned by means of ether and then dried. Next they were weighed accurately and placed in closed vessels filled with oil, and kept for a year at a uniform temperature, in summer at 80° F., and in winter at about 50° F. It would, however, not be permissible to draw from these experi¬ ments the conclusion that the oils would behave in the same manner if used for lubricating bearings, etc., the conditions being essentially different. Therefore similar experiments instituted by Donath, 2 Aisin- mann, a. o., need not be detailed here, as being of little practical use. The larger the proportion of free acids in an oil, the greater is the liability to corrode metal. The determination of free fatty acids in lubricating oils is, therefore, very important. It is carried out by titrating with caustic alkali, using phenolphthalein as an indicator (p. 182). It should be borne in mind that fatty oils undergo hydrolysis in high-pressure steam cylinders, and that the fatty acids thus set free will corrode the iron cylinder. The acidity is expressed in various ways, as shown in the table, p. 150. In this country it is customary to calculate the alkali used 1 Jour. Soc. Glum. Ind. 1886, 362. 2 Ibid. 1895, 283. XII LUBRICATING OILS 719 to oleic acid, and return it as per cents of free fatty acids. It should, however, be remembered that acidity of an oil may be due to mineral acid used in refining, as in the case of rape oil. Therefore the test for mineral acids should not he omitted. The examination of the various oils for adulterants has been dealt with exhaustively in the preceding chapter. It should be remembered that if liquid waxes are present the proportion of unsaponifiable matter will be high. 2. Mineral Oils The mineral oils used for lubricating are derived from crude petroleum or from shale. The oils from the latter are mostly dis¬ tilled products, the oils derived from the former are either distilled oils or the still residues refined by treatment with animal char. Besides applying the tests mentioned above, the following points deserve attention :— Loss by Evaporation. —In the case of fatty oils the point at which evaporation commences almost coincides with the temperature at which decomposition takes place, whereas in the case of mineral oils, consisting as they do of oils of different boiling points, evapora¬ tion—and consequently loss to the user of the oil—may begin below the temperature at which the bulk of the mineral oil volatilises. The method ordinarily adopted to determine the loss by evapora¬ tion was to heat for several hours an accurately weighed quantity on a watch glass and to weigh the residue. Oils intended for the lubri¬ cation of machinery at normal temperatures would be heated for, say, five hours at 100° C., and in the case of cylinder oils the tests should be made in the drying oven at a temperature of say 180° C. 1 Archbutt 2 recommends as a safer method to heat the oil in a current of air or superheated steam. 0'5 grm. of the sample are placed in a platinum tray, which for convenience of manipulation is brought into a glass tube, and so introduced into a copper tube f in. internal diameter, and 2 ft. long. Round the copper tube is coiled a tube f in. diameter, and about 10 ft. long, one end of which enters the wider copper tube and serves to heat the current of air or steam which is passed over the oil. The coiled tube is fixed in an air-bath and heated by a row of small gas jets to the desired temperature, con¬ trolled by a thermometer. A measured quantity of air is passed over the oil at the rate of 2 litres per minute for exactly one hour; the oil is then withdrawn and reweighed. Good locomotive cylinder oils should not lose more than 05 per cent at a temperature of 370° F. (188° C.) under the conditions described above. Presence of water is recognised by frothing or bumping, on heat¬ ing in a test-tube. Oils containing notable proportions of water have a turbid appearance. Turbidity due to separated paraffin wax or impurities, etc., may disappear on heating, but will reappear in the cooled oil after standing. 1 Cameron-Leask, p. 295. 2 Jour. Soc. Chem. Ind. 1896, 326. 720 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. Acidity.—In their pure state mineral oils should be practically free from acids, and therefore have but slight action on metals when compared with fatty lubricating oils. Small quantities of mineral acids left in the oil in consequence of faulty washing after refining are detected by shaking the sample with water, to which a drop of methylorange solution has been previously added. The so-called petroleum acids are not removed by washing with water. Their proportion is determined, according to Zaloziecki, 1 by shaking 100 grms. of oil Avith 50 c.c. decinormal alkali, consisting of equal volumes of aqueous and alcoholic solutions, and titrating back the free alkali. Allen 2 heats in special cases 50 grms. of the oil for six to eight hours with an equal volume of water in a closed vessel immersed in boiling water, shaking the contents of the bottle from time to time. When the two layers have separated the aqueous liquid is titrated with decinormal alkali, using phenolphthalein as indicator. The acidity will be due in most cases to sulphuric acid, produced by the decomposition of sulphonates in the oil; if a notable amount has been found, the oil must be rejected. In the case of cylinder oils the vessel should be immersed in a boiling calcium chloride solution. Ash.—The ash is determined by igniting an accurately weighed quantity in a platinum dish and weighing the residue. This should be nil. In case a soda or potash soap was added, the residue treated with water will give a strongly alkaline reaction when tested with litmus paper. An alkaline reaction may be also due to lime. If the ash is considerable it should be examined. In case an “ oil thickener ” has been added, say aluminium oleate, notable proportions of alumina will be found. Schweitzer and Lungwitz z recommend as a reagent for the detec¬ tion of soaps in lubricating oils a saturated solution of metaphosphoric acid in absolute alcohol. The determination of paraffin—paraffin wax —will but rarely be required. Lubricating oils containing too much paraffin would not prove satisfactory in the cold-test, and would therefore be rejected at the outset. Holde has examined the processes proposed by Pawlewski and Filemonewicz, Zaloziecki, and Roland for the estimation of small quantities of paraffin; 4 he rejects them as not admitting of general application, and recommends the following method, being a modifica¬ tion of the one originally proposed by Fngler and Boehm, as yielding satisfactory results:— 10 to 20 c.c. of oils poor in paraffin (such as Eussian distilled oils, solidifying below - 5° C.), or 5 grms. of oils rich in paraffin (such as American, Scotch, Galician, solidifying at or above 0° C.) are dissolved in an equal number of c.c. of a mixture of equal parts of absolute alcohol (98’5 per cent) and ether in an Erlenmeyer flask of 150-200 c.c. capacity at the ordinary temperature. The flask is then immersed in a freezing mixture registering from - 18° to - 20° 1 Chem. Revue, 1897, 37. 2 Comm. Org. Anal. ii. 205. 3 Jour. Soc. Chem. Ind. 1894, 1178. 4 Cp. Eisenlohr, ibid. 1897, 701. XII LUBRICATING OILS 721 C., and whilst the solution is vigorously agitated, so much of the alcohol-ether mixture is added until oily drops just disappear and thp liquid exhibits only crystals or flocks of paraffin wax. The crystals are filtered off at the same low temperature and washed with the alcohol-ether mixture previously cooled down to - 18° to - 20° C. until 5 to 10 c.c. of the filtrate no longer give an oily residue. Prolonged washing beyond this point will lead to loss. The paraffin wax retained on the filter is washed with benzene into a capsule, the solvent is evaporated off, and the residue dried at 105° C., prolonged heating in the air-bath being avoided. Impurities due to incomplete purification of the oils may be tested for by one of the following methods. In some cases these impurities are left purposely in the oils, as a complete removal of the asphalt¬ like and mucilaginous substances, naturally occurring in the crude oils, tends to reduce the viscosity and consequently the apparent lubricating value. On the other hand badly refined oils have a tendency to resinify easily. Schaedler, and also Martens , shake equal measures of the sample and of sulphuric acid, specific gravity P53 ; in the case of a pure oil the acid should separate as a colourless or, at most, slightly yellow layer; there should be no separation of black flocks in the oil, nor should it be coloured brown. If the acid remains colourless, or is but slightly coloured, the experiment should be repeated, the cylinder containing the mixture being heated this time to 100° C.; pure oils should not turn brown even under these conditions. It has been attempted to convert this test into a quanti¬ tative one by operating as follows :— 20 c.c. of the sample are well shaken in a graduated stoppered cylinder with 10 c.c. of concentrated sulphuric acid and 20 c.c. of petroleum ether; the increase in volume of the acid is then read off after settling out. Oils of good quality should yield to the acid no more than T2 to 2'4 c.c., i.e. 6 to 12 per cent. But it should be under¬ stood that these results are a rough approximation only, as the “ naph¬ thenes ” are soluble in concentrated sulphuric acid. 1 Holde 2 showed that by treating lubricating oils with a mixture of alcohol and ether (3 : 4) resinous or asphaltic bodies containing oxygen are precipitated, but no reliable quantitative method has been worked out hitherto. 3 Fatty oils in mineral oils are present, if the sample has yielded a definite saponification value; very small quantities of glycerides are detected according to Lux’s method (p. 223). Resin oil, as also tar oils , are detected by the methods given above (p. 225). Resin oil is determined quantitatively, according to Storch , 4 as follows :— 10 to 15 grms. of the mineral oil, which must be free from fatty oils, are gently warmed in a flask with five times their weight of 96 per cent alcohol, the mixture being occasionally shaken and allowed to 1 In the presence of fatty oils the sulphuric acid treatment leads to altogether unreliable results. 2 Jour. Soc. Chem. Ind. 1895, 894. 3 Cp. also Aisinmann, ibid. 1895, 282 ; Singer, Chem. Revue, 1897, 93. 4 Jour. Soc. Chem. Ind. 1891, 276. 722 TECHNICAL AND COMMERCIAL ANALYSIS chai>. cool. The alcoholic solution, containing all the resin oil present, is then transferred to a tared Erlenmeyer flask, about 7 cm. high; the mineral oil is again washed, without agitating, with a few c.c. of 96 per cent alcohol, which are added to the main washing. The Erlenmeyer flask is now gently heated, surrounded by a beaker so as to prevent too rapid condensation, on the water-bath until the residue in the flask is free from bubbles. It is then cooled and weighed. The weight of this residue (A) will be that of the resin oil plus a portion of mineral oil dissolved by the alcohol. To remove the greatest part of the mineral oil, the residue (A) is treated next with ten times its weight of alcohol, and the solution boiled down as before, when a second residue (B) is obtained, which still contains a small quantity of mineral oil. The correction necessary for this is found in the following manner :—Suppose 1T2 grms. of the sample have been treated with 50 grms., and subsequently residue A with 15'5 grms. of alcohol. Let the weight of A be T51 grms., and that of B IT5 grms., then 50 - 15-5 = 34-5 grms. of alcohol had dissolved 1*51 - 1T5 = 0‘36 grms., hence 15’5 grms. had dissolved 0T62 grms. of mineral oil. There are therefore present in the sample IT5 - 0T62 = 0‘988 grms., or 8’8 per cent of resin oil. The true quantity lies between the two weights of the second residue, viz. between B and its corrected value. Nitrobenzene is readily detected in debloomed oils by its smell, especially on warming. For the detection of nitronaphthalene in mineral oils, Leonard 1 gives the following method based on the reduction of nitronaphtha¬ lene to naphthylamine :—A small quantity of the oil is gently warmed with zinc-dust and dilute hydrochloric acid, and the mixture agitated from time to time. During this process the faecal odour characteristic of a-naphthylamine will be perceived. After the reduction is com¬ plete the acid aqueous liquid is drawn off by the aid of a separator. A portion of this liquid, when neutralised with ammonia, gives with ferric chloride a blue precipitate which rapidly becomes purple. The remainder of the solution may be rendered alkaline with soda and extracted with ether. The latter is then evaporated, and the residue dissolved in a little alcohol. On the addition of a drop of a sodium nitrite solution, acidified with acetic acid, a yellow colour is produced, which is changed to crimson by hydrochloric acid. 3. Mixtures of Fatty and Mineral Oils Mineral oils are miscible with all fatty oils, castor oil excepted (p. 421). 2 Extensive use is made of this miscibility in practice, and by far the greatest number of commercial lubricating oils consist of such mixtures. Latterly also “blown oils” (p. 733) are largely mixed with mineral oils, or with mixtures thereof and of fatty oils, 1 Jour. Soc. Chem. Ind. 1894, 69 ; cp. also Holde, ibid. 1894, 906. 2 Castor oil can, however, be made miscible with mineral oils by mixing it first with a fatty oil, say tallow oil. XII LUBRICATING OILS 723 their high viscosity and specific gravity rendering them especially suitable for this purpose. Also soap and “ oil thickeners ” are added fraudulently to give the oil more “body,” and the fluores¬ cence of mineral oils is concealed by “ deblooming ” the oil by means of nitronaphthalene, nitronaphthol, or nitrobenzene. Such mixtures are examined and their constituents determined quantitatively by means of the “ quantitative reactions ” described in chaps, vii., viii. (cp. also “Soaps,” p. 785). Fig. 47. The nature of the fatty oils may be ascertained by separating the unsaponifiable matter from the soap solution, which contains also any resin acids present, liberating the free fatty acids, and examining them systematically. A definite acetyl value will point to the presence of “ blown oils,” if castor oil be absent. The unsaponifiable matter is tested for resin oil as already described. According to Kiinkler, 1 the viscosity of the mineral oil (unsaponi¬ fiable portion) should also be determined. The quantity required for 1 Jour. Soc. Chem. hid. 1894 , 543 . 724 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. this test being somewhat large when the existing viscosimeters are used, Kurikler has designed a new apparatus requiring only 30 c.c. This apparatus (Fig. 47) consists of a sheet brass (oil- or) water- bath, w, provided with a copper bottom, the contents of which may be heated by a gas burner ; the temperature of the heating liquid is read off a thermometer held by x; w contains the removable stand d placed firmly on four legs, and supported by two brackets h. In this stand fits the viscosimeter, made of strong glass and consisting of the charging-funnel k, the bulb e bearing the mark /, the capillary tube c, the lower bulb a, and the ascending tube b; the whole apparatus is held in position by the spring-clamp i. The temperature of the contents of the viscosimeter is controlled by thermometer k. The ascending tube b is supported by l; it is fitted with a tap m, and connected by means of india-rubber tubing with the suction apparatus r, in which the mercury used for aspirating the oil is allowed to rise up to the mark p. Bulb t serves as a receptacle for the mercury; can y is used for warming the oil to the desired temperature. The apparatus must be gauged with a dilute glycerin solution of 1T10 specific gravity at 20° C., and the time required for its outflow at 20° 0. is taken as unity. For temperatures up to 100° C. mercury is used as the aspirating liquid, for higher temperatures water is preferred. In the heating vessel w water is used for temperatures up to 100° C., and above 100° C. an oil of high boiling point. The test is carried out in the following manner : Fill r up to the mark p with the aspirating liquid and heat the bath. In the meantime warm the oil to be tested in can y a few degrees above the required temperature. Take the viscosimeter for a short time—say half a minute—out of the bath so that the air in a may be cooled a little, and then put it back, filling at the same time vessel e with the oil up to mark /. The air in a will then expand so that no oil can enter it. Allow the oil in e to assume the temperature of the bath, connect the viscosimeter with the aspirator, and open tap o. Then open tap m and observe accurately the time required by the oil to rise in the ascending tube b up to the mark g. For the accurate dimensions of the various parts of the apparatus (which may be had from C. Desaga of Heidelberg), the original paper must be consulted. The following table contains a few viscosimetric constants as determined with the new apparatus, contrasted with the numbers obtained by means of Dngler’s viscosimeter :— [Table LUBRICATING OILS O O VO CON SO ^ ^ o „ m o o vo vo vO O CO NOCO O (M VO CO CO h CO (M (M O O vO IN 0 O (N N- Oi to f—t a o g ^ T5 c3 O .h I ° S 726 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. 4. Solid Lubricants—Greases Under this head fall the solidified oils and the solid lubricants (greases). The former are mostly mineral oils gelatinised by soda or lime soap, the latter consist of mixtures of solid fats, fatty oils, mineral oils, resin oils, and lime and aluminium soaps (of fatty acids or resin acids). These lubricants contain a certain proportion of water. “ Weighting substances ” are added fraudulently or, as in the case of talcum or plumbago, with a view to increase the lubricat¬ ing power of the “ grease.” Galena oils (plumbago oils) consist of lead soaps dissolved in mineral oils. The analysis of these solid lubricants offers no difficulty. The lubricant is first dried and then extracted with a suitable volatile solvent when the mineral matters and soaps remain undissolved, the mixed fatty and mineral (and resin) oils passing into solution. Small quantities of dissolved soaps may be removed from the latter by washing the mixed oils after evaporating off the solvent with water or with dilute mineral acid. The mixed oils are examined as described already (p. 722); the insoluble part is examined in a similar way to soaps (p. 785). But it should be borne in mind that in these cases, as also in the case of locomotive or waggon greases, the chemical analysis gives no clue as to the lubricating value. Hot neck grease (p. 692). F. TURKEY-RED OILS 1 Turkey-red oil is a fatty substance used in the preparation of the cotton fibre for dyeing and printing Turkey-red. The part which the Turkey-red oil plays is not fully understood yet; it is explained as a physical or as a chemical action. In the light of the former explanation it is assumed that the oil protects the lake formed on the fibre, much as linseed oil may be looked upon in painting. In the latter case the oil is said to combine with alumina and finally with the colouring matter, forming a compound lake. In these cases, however, where chemical combination with formation of a lake is excluded on account of the chemical constitution of the colouring matter, the physical theory appears to commend itself. Thus the oil is not a mordant proper, but acts as a fixing agent in so far as it 1 Fremy, Ann. de Phys. et de Chim. 65. 121 ; Annalen, 19. 296 ; 20. 50. Miiller- Jacobs, Jour. Soc. Chem. Ind. 1884, 257 ; 412. 1885, 18 ; 21 ; 115. Liechti and Suida, Jour. Soc. Chem. Ind. 1886, 662. H. Schmid, Dingl. Polyt. Jour. 254. 346. Sabanejeff, Berichte, 19, Ref. 239. M. and A. Saytzelf, Berichte, 19, Ref. 541. Bene- dikt and Ulzer, Jour. Soc. Chem. Ind. 1887, 543 ; 1888, 328. Scheurer-Kestner, Jour. Soc. Chem. Ind. 1891, 471, 555. Juillard, Jour. Soc. Chem. Ind. 1892, 355 ; 1893, 528. Wilson, Jour. Soc. Chem. Ind. 1891, 26 ; 1892, 495. Lochtin, Jour. Soc. Chem. Ind. 1890, 498, Juillard, Jour. Soc. Chem. Ind. 1894, 820. Wolff, Chem. Revue, 1897, 103. XII TURKEY-RED OILS 727 imparts to the dyed fabric a better and superior lustre, which does not belong to the unoiled fibre. Turkey-red oil is usually prepared by the action of concentrated sulphuric acid on castor oil, the acid being allowed to run into the oil slowly with constant stirring, so that the temperature of 35° C. is not exceeded. If necessary, the mass must be cooled, as at a higher temperature secondary reactions take place with liberation of sul¬ phurous acid. The product is next mixed with water and allowed to settle out. The lower layer is then drawn off and washed with brine, or, better still, with a solution of Glauber salt, until the washings are only slightly acid. Finally ammonia is added, until a sample gives a complete emulsion with water. Instead of ammonia some manu¬ facturers use soda, or a mixture of ammonia and soda. The resulting product is not completely neutralised by the alkali, and consequently still possesses a strong acid reaction. The crude product as obtained before the partial neutralisation can be easily resolved into tw T o portions, one being readily soluble, the other in¬ soluble in water. The separation is effected as follows : The product obtained after mixing castor oil with sulphuric acid is dissolved in ether, washed with brine until free from sulphuric acid, and then repeatedly shaken out with water. Ihe aqueous solutions are united and treated with sodium chloride, when the water-soluble portion separates as an oily layer. On evaporating off the ether from the ethereal solution the water-insoluble portion is obtained. Benedikt and Ulzer have shown that the water-soluble portion of castor Turkey-red oil consists of ricinoleo-sulphuric acid, an acid sulphonic acid ether of ricinoleic acid, formed according to the following equation:— ^ 18 -^ 33^2 • OH + SO4H2 = . 0 . SO3H + H.iO. Ricinoleic acid. Ricinoleo-sulpliuric acid. This ricinoleo-sulphuric acid is miscible with water in all pro¬ portions ) the aqueous solutions give a lather like soap solutions. Brine, moderately dilute sulphuric acid, and hydrochloric acid precipi¬ tate it from its aqueous solution, the ricinoleo-sulphuric acid forming a heavy oily layer on the bottom of the containing vessel. On shaking with ether three layers are formed ; the middle layer consists of the acid mixed with large quantities of ether, whereas the uppermost ethereal layer contains smaller quantities of the acid. Lead, copper, calcium, and barium salts added to the solution of the acid produce viscous precipitates. Ricinoleo-sulphuric acid is not decomposed on boiling its aqueous or alkaline solutions ; but boiling with dilute hydrochloric or sulphuric acid decomposes it readily into ricinoleic and sulphuric acids. The water-insoluble portion of castor Turkey-red oil consists chiefly of free ricinoleic acid mixed with small quantities of neutral (unacted on) fat, and perhaps also of anhydrides of ricinoleic acid. 728 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. Scheurer-Kestner is of the opinion that castor Turkey-red oil con¬ sists of ricinoleo-sulphuric acid (as stated by Benedikt and Ulzer) and of monoricinoleic and diricinoleic acids, polymerisation of the free ricinoleic acid having taken place. According to Juillard, polymerisation proceeds further, giving rise to the formation of di-, tri-, tetra-, and penta-ricinoleic acids, an opinion at variance with Scheurer-Kestner’s views, who maintains that polymerisation extending beyond the formation of the di-acid is due to a secondary action of hydrochloric acid liberated on washing the pro¬ duct with brine instead of Glauber salt. In Juillard’s opinion castor Turkey-red oil is a mixture of varying proportions of poly-ricinoleic acids of alkali salts of mono- and poly-ricinoleo-sulphuric acids, of anhydrides of the latter acids, and of their products of decomposition. 1 Besides castor oil also other fatty oils, such as olive oil, arachis oil, and cotton seed oil, are used in practice for the production of Turkey- red oils. According to Benedikt , castor Turkey-red oil cannot be replaced by these oils for the reason that by treatment with sulphuric acid saturated hydroxy acids and their sulphuric acid ethers are formed, thus (taking oleic acid as an example)— C 18 H 34 0 2 + S0 4 H 2 = C 18 H, 5 (0. SO : ,H)Oo. . Oleic Hydroxystearo- acid. sulphuric acid. The latter acid is then decomposed for the most part according to the following equation— C 18 H 35 (0. S0 3 H)0 2 + H 2 0 = C I8 H 35 (0H)0 2 + S0 4 H 2 . Ilydroxystearo- Hydroxystearic sulphuric acid. acid. Whereas, therefore, Turkey-red oil from olive, arachis, and cotton seed oils, and consequently also from oleic acid, contains saturated acids, castor Turkey-red oil consists solely of unsaturated fatty acids; hence the superior effect of the latter may be due to the oxidisability of the castor Turkey-red oil fatty acids. This last statement of Benedikt may require some qualification, since Schmitz and Tonges 2 have prepared a Turkey-red oil by mixing oleic acid with sulphuric acid and heating the product to 105°-120° C., whereby hydroxy acids are supposed to be formed with loss of sul¬ phurous acid, and since JVvrner 3 has stated that this Turkey-red oil is, in certain cases, superior to castor Turkey-red oil. The chemistry of Turkey-red oils requires, therefore, further elucidation; it may be added that G-eitel (p. 69) has proved the presence of stearolactone and of the anhydride of the ordinary hydroxystearic acid in Turkey-red oil prepared from oleic acid. The commercial Turkey-red oils are more or less thickish fluids, appearing yellow in thin and brown in thick layers. 1 Jour. Soc. Chem. Ind. 1894, 820. 2 jjy u i 1392 327 3 Ibid. 1893, 40. XII TURKEY-REI) OILS 729 Since their composition depends on the mode of manufacture and on the raw material used, the Turkey-red oils have no constant composition. The commercial examination of Turkey-red oil divides itself into two parts, viz. (1) the preliminary examination, the most important part of which consists in dyeing samples prepared with the oil, and (2) the chemical tests. Preliminary Examination The sample should give a complete emulsion with water; separa¬ tion of oily drops may take place after long standing only. This test is performed by mixing, in a graduated cylinder, one measure of oil, at first with a little warm water, gradually increasing the quantity until ten measures have been added, and comparing the appearance of the sample with an emulsion prepared side by side in exactly the same way with a standard sample of known purity. Both emulsions should act in a like manner on litmus paper, showing a slightly acid reaction. In case the reaction should be neutral or alkaline, acetic acid must be added, drop by drop, until the intensity of the reaction and of the turbidity in both samples is alike. Good oils should give a clear solution with ammonia, and exhibit no turbidity even if large quantities of ammonia are added. The alcoholic solution of a Turkey-red oil is the more turbid the larger the amount of unchanged oil (neutral fat) in the sample. The sample dyeing is carried out in the following manner:—Two pieces of cotton of equal size are prepared with the sample and with a standard oil respectively by allowing them to soak in an emulsion made from 1 part of oil and 15-20 parts of water (some experimenters add ammonia until the emulsion just becomes clear). After drying, the fabric is mordanted with alum and dyed in alizarin (blue shade), or, as the case may be, steam red is printed on. The samples are then brightened by soaping and finished in the usual manner. It is evident that this mode of comparison will be only resorted to in a works laboratory, or by an analyst who has special experience in that branch of work. Chemical Examination The value of a Turkey-red oil depends, in the first instance, on the proportion of total fatty matter in the sample, comprising under the latter term the sum of the water-insoluble portion obtained after acidifying the oil (viz. fatty acids, hydroxy acids, and neutral fat) and of the hydroxy acids obtained on decomposing the soluble sulphuric ethers of the fatty acids. Next, the proportion of neutral fat, sulphuric ethers of fatty acids, ammonia or soda, and sulphuric acid, may be estimated. 730 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. Indications as to the nature of the raw material used are obtained from the iodine and the acetyl values of the total fatty matter 1. Total Fatty Matter. —The older processes, proposed by Briilil and Stein, do not yield accurate results, and are therefore omitted here. The best method is that recommended by Benedikt. 1 About 4 grms. of the sample are weighed off accurately in a half¬ circular porcelain basin of about 125 c.c. capacity, previously tared together with a glass rod. The oil is mixed with 20 c.c. of water, added gradually; should the liquid be turbid, a drop of phenol- phthalein is added and then ammonia run in, until slightly alkaline, when a clear solution will be obtained, or, at any rate, only a few flocks will remain undissolved. If the addition of ammonia is omitted the results will be too high. 15 c.c. of sulphuric acid, consisting of equal measures of concentrated acid and water, are then run in with stirring, and an accurately weighed quantity of stearic acid, say 6 to 8 grms., added. The mixture is then heated until a clear fatty layer has separated on the top. This is allowed to solidify by cooling; the cake is then lifted up by means of the glass rod, rinsed off with a little water, and placed meanwhile on filter paper. The contents of the dish are warmed on the water-bath, so that the particles of fatty matter adhering to the sides and floating- in the water collect into one drop, which is conveniently made to adhere to the sides of the vessel on cooling. The liquid is then poured off, the basin rinsed out, and the cake of fatty matter placed in t it. Now the basin is heated over a very small flame, which must not touch its bottom, and the melted fat continually stirred with the glass rod, until the crackling noise has ceased and white vapours are just beginning to escape. The fat is then allowed to cool and weighed. Of course, the separated fatty matter may be collected and dried by any other convenient method, such as that described by Hehner for the determination of the percentage of fatty acids in a fat (p. 160), or as is the practice in the analysis of soaps, or according to the method proposed by Guthrie . 2 For the purposes of a rapid determination the following process, due to Finsler, has been recommended by Breindl. 3 This process is largely employed in practice, and yields approximately the same results as Benedikt’s method. A flask of about 200 c.c. capacity provided with a long neck, which is graduated to i or y 1 ^ c.c., is used for this test; the lowest graduation represents a capacity of 150 c.c., the uppermost 200 c.c. 30 grms. of the sample are weighed off accur¬ ately, washed into the flask with hot water, the volume made up to about 100 c.c., then 25 c.c. of sulphuric acid of spec. grav. 1‘563 (52° B6.) are added, and the mixture heated to boiling with frequent 1 Zeitsch. f. angew. Chem. 1887, 325. 2 The process recommended by Guthrie [Chem. News, 1890, 52) is stated by R. Williams [Chem. News, 1890, 76) to yield erroneous results. If, however, the above- given definition of total fatty matter be accepted, his criticism falls to the ground. 3 Jour. Soc. Chem. Ind. 1889, 573. XII TURKEY-RED OILS 731 shaking until the fatty matter forms a clear and transparent layer. A hot concentrated solution of common salt or Glauber salt is next added in small portions, until the separated layer of fat rises into the neck of the flask. After half an hour’s standing the volume of fat is read off; the number of c.c. multiplied by 3'33 corresponds to per cents of total fatty matter. • 2. Neutral Fat. —About 30 grms. of the sample are dissolved in 50 c.c. of water, 20 c.c. of ammonia and 30 c.c. of glycerin are added, and the mixture exhausted with ether twice, using 100 c.c. each time. The ethereal solution is freed from small quantities of dissolved soap by washing with water, and the ether evaporated off. The residue is transferred to a tared beaker of about 150 c.c. capacity, dried at first on the water-bath, then in an air-bath at 100 J C., and weighed. 3. Soluble Fatty Acids (Sulphonated Fatty Acids). —5 to 10 grms. of the oil under examination are dissolved in a strong-walled flask in 25 c.c. of water, 25 c.c. of fuming hydrochloric acid are added, and the contents of the closed flask heated in an oil-bath to 130°-150° C. for one hour. Water is added next, the mixture trans¬ ferred to a beaker and the fatty layer filtered off, most conveniently after some stearic acid has been melted with it. The sulphuric acid in the filtrate is then determined by precipitation with barium chloride. From the amount thus found the quantity of sulphuric acid, as determined under 5 (see below), is subtracted and the differ¬ ence calculated to ricinoleic acid, 80 parts of S0 3 corresponding to 378 parts of ricinoleo-sulphuric acid, C 18 H 33 0. 2 . O . S0 3 H. Even in the case of the Turkey-red oil under examination not having been prepared from castor oil, this calculation will be correct, as the molecu¬ lar weight of hydroxystearo-sulphuric acid—380—almost coincides with that of ricinoleo-sulphuric acid. 4. Ammonia and Caustic Soda.—7 to 10 grms. of the sample are dissolved in a little ether, and shaken four times with dilute sulphuric acid (1 : 6), using 5 c.c. each time. For the determination of ammonia, the acid liquors are distilled with caustic potash in the well-known manner, and the ammonia received in an accurately measured quantity of standard acid; after titrating back the excess of acid the amount of ammonia is calculated. For the estimation of caustic soda the acid liquors are concen¬ trated in a platinum dish on the water-bath, and the excess of sulphuric acid driven off by heating on the sand-bath; the residue is ignited after mixing with ammonium sulphate and the formed sodium sulphate weighed. 5. Sulphuric Acid. —The quantity of sulphuric acid present in the form of ammonium or sodium sulphate is found by dissolving a weighed quantity of the sample in ether, and shaking it several times with a few c.c. of concentrated brine free from sulphates. The several washings are united, diluted, filtered, and the filtrate precipitated with barium chloride. Another method would be to determine the total sulphur in the 732 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. sample by Liebig’s method (p. 95), when the amount of sulphuric acid (or of sulphonated fatty acids) may be found by difference. The method for the detection of iron in Turkey-red oils has been described p. 99. The examination of a sample of Turkey-red oil, with a view to determining the nature of the raw material used—whether pure castor oil, or another fatty substance—is best based on the iodine and acetyl values of the total fatty matter. This is prepared as described above under 1, with the only difference that no stearic acid is added. If the iodine value is not much below 80, pure castor oil has been used; otherwise an adulterated castor oil may have been employed, or olive oil, arachis oil, cotton seed oil, oleic acid, etc. It should be remembered that these substances yield saturated acids; consequently, a very low iodine value will point to the absence of castor oil. An acetyl value of 140 or above will point to pure castor oil; in the case of other oils lower values will be obtained. The following is the percentage composition of a very good sample of Turkey-red oil:— Water-soluble fatty matter Per cent. . 9-5 Water-insoluble fatty matter - Neutral fat 1-3 .Fatty acids . 47'2 Total fatty matter . 58-0 Ammonia 1-8 Total sulphuric acid . . 4-6 A sample of genuine castor oil examined in the writer’s laboratory gave the following result:— Total fatty matter . . 40 T per cent. Unsaponifiable. . . . 0T5 ,, The following constants were ascertained for the fatty acids obtained by saponification :— Specific gravity at 15° C. . . . 0'9449 Iodine value . . . . 82 T Acid value. . . . 174‘3 Saponification value . . 189‘3 Acetyl value .... 126'9 It may be mentioned here that latterly Schemer 1 has proposed metallic sulpholeates—sulpholeate of aluminium—as mordants for steam colours. 1 Jour. Soc. Chem. Ind. 1893, 1025. XII OXIDISED OILS—BLOWN OILS 733 G. OXIDISED OILS 1 . Blown Oils Under the terms “ blown oils,” “ base oils,” “ thickened oils,” “soluble castor oil,” a number of oils are brought into commerce, prepared by treating fixed oils with air at a somewhat elevated temperature. The oils are heated in a jacketed pan by steam to 70° C., in some cases to 110°-115° C., and air is blown through. The temperature rises beyond that of the steam used for heating, and in some cases it is necessary to cool the blown oil by a cooling worm. The oils increase under this treatment in density and also in viscosity. They approach in these respects castor oil, but differ from it in that they are miscible with mineral oils, and are but sparingly soluble in alcohol. They are, however, more soluble in alcohol than the original oils, as shown in the following table, due to Benedikt and Ulzer : 1 — 1 Part of Cotton seed oil Blown cotton seed oil, laboratory sample ,, ,, commercial sample Dissolved in parts of Absolute Alcohol at 18° C. 357 22-9 14-9 The nature of the chemical change taking place is not fully known. Benedikt and Ulzer have obtained high acetyl values on examining the two blown oils mentioned in the table, and are there¬ fore of opinion that the fatty acids are partially converted into hydroxy acids; at the same time the iodine absorptions decreased considerably. No glycerol appears to be destroyed by the blowing (cp. “Boiled Oil”). Thomson and Ballantyne 2 have examined a number of “ blown oils,” confirming a few earlier experiments made by Fox and Baynes . 3 The changes which a sample of rape oil and of sperm oil underwent on blowing are shown in the following table, to which are added a few analyses of commercial blown oils :— 1 Zeitsch. angew. Chemie, 1887, 245. 2 Jour. Soc. Chem. Ind. 1892, 506. 3 Analyst , 1887, 33. [Table Page 295. 2 Chem. News, 1894 [70], 2. XII BLOWN OILS—BOILED OIL 735 “ Blown oils ” are said to be very suitable for lubricating purposes on account of their high specific and viscosity \ but opinions conflict as to their suitability, the principal objection appearing to be that they are liable to gum. Nevertheless, they are extensively used, mixed with mineral oil, and even with resin oil. The examination of blown oils chiefly consists in the determina¬ tion of the unsaponifiable matter and detection of resin oil. 2. Boiled Oil French— Huile cuite. German— Gekochtes Leinoel, Leinoelfirniss. Boiled oil is prepared by “ boiling,” i.e. heating linseed oil to a temperature from 210° to 260° C., whereby it acquires the property of more rapidly drying into a varnish, when exposed to the air, than raw linseed oil. This property of absorbing oxygen is further increased if “ driers ” (such as manganese dioxide, manganese borate, manganese oxalate, litharge, etc.) are added to the oil whilst being heated. These “ driers ” seem to act as oxygen carriers; 1 at any rate it is proved that the lead salts of unsaturatecl fatty acids dry better than the fatty acids themselves. 2 The suitability of a raw linseed oil for making “ boiled oil ” is chiefly determined by its age. Fresh oils give a scum on boiling, and effervesce very strongly ; therefore only old “ tanked ” oil, from which solid glycerides, as also water, have separated out as “ muci¬ lage,” can bemused. Chemical tests, apart from tests for purity, are of little use for the valuation of raw oil. The higher the specific gravity the better it will be. According to it should not be less than 0935 at 15-5° C. The Livache and the MaumenS tests may also furnish useful indications. 3 What action takes place during the process of boiling is not known yet. A slight decomposition of the linseed oil undoubtedly does take place, as proved by the evolution of acrolein vapours. This decomposition, however, is a limited one, as boiled oil still yields 8-9 per cent of glycerol. Oxidation seems also to take place to some extent, but cannot go very far, as the boiling oil comes in contact with but a limited quantity of air. The lower iodine value of the boiled oil may either point to oxidation or, as l 1 cchrion 4 assumes, to polymerisation. The “ driers ” appear to form linolates, which dissolve in the remainder of the oil and increase its oxygen absorption power. 2 Boiled oil has a darker colour than raw oil, being more of a red- brown shade. The higher the oil has been heated, the darker as a 1 The comparative action of various driers has been studied by Thorpe (Jour. Soc. Chem. Ind. 1890, 628). Recent researches have shown that only lead and manganese driers are useful. 2 Cp. Eng. Pat. 1891, 7251, and Eng. Pat. 1893, 9315. 3 According to Lippert, linseed oil for boiling should not give flocks on heating to about 300° C. 4 Jour. Soc. Chem. Ind. 1892, 696. 736 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. rule will be the colour of the product. Boiled oil is more viscous than raw linseed oil; it has a higher specific gravity, ranging from 0'9389 to 0 - 9433, according as it was boiled with a manganese- or a lead-drier. The iodine value of boiled oil is lower than that of raw oil (see belotv). A sample of boiled oil examined in the writer’s laboratory had the iodine value 127 (cp. also below). 1 It is very likely that boiled oil will show a higher acetyl value than raw oil. Boiled oil is adulterated in the same manner as linseed oil; the adulterants most frequently used are resin, and mineral and resin oils. 2 They are detected as described under the heading “Linseed Oil” (p. 343). The so-called “ patent boiled oils ” are, as a rule, adulterated oils. A rapid method, 3 suitable as a preliminary test, to detect unsaponijiable matter is to add water after saponification with alcoholic potash, when a strong turbidity will indicate presence of adulterants. 2 Resin could, of course, not be thus detected ; if its presence be sus¬ pected, the writer recommends to determine the acid value of the sample, using phenolphthalein as indicator, and to calculate the number of c.c. used to resin, molecular weight 346. The small pro¬ portion of free fatty acids, if any, is neglected. For the Liebermann- Storch reaction an alcoholic extract of the oil, but not the oil itself, should be used. The employment of the butyro-refractometer 4 has been proposed, but it would be easy to prepare mixtures having correct deviations. The distinction between linseed oil and boiled oil may be based on the iodine and specific gravity tests. A practical test is to allow the sample to dry on a watch-glass side by side with a sample of raw linseed oil. Boiled oil dries within twenty-four hours, whereas raw linseed oil at most becomes more viscous. This practical test would also indicate adulteration with fatty oils, such as rape oil and cotton seed oil. Boiled oil is, as a rule, mixed with raw linseed oil, as, used alone, it would give a somewhat “ hard ” coat, liable to crack, whereas the addition of raw linseed oil renders the coat more elastic and durable. The detection of small quantities of raw linseed oil in boiled oil has therefore little practical importance. For the rapid distinction of linseed oil from boiled oil Finkener recommends for custom-house purposes the following test, by which 25 per cent of boiled oil can be detected in raw oil. The following reagents are required :—A 20 per cent ammonia solution, and a solu- 1 R. Williams (Analyst, 1895, 277) gives the following iodine values for boiled oils at different stages of boiling :— Thin. Thin. Stout. Very Stout. Iodine value . 111’3 112 - 4 65.6 59’9 It should be noted that these numbers are very likely too high, as the Hiibl solution was allowed to act on the oil for 18 to 20 hours. 2 Cp. paint oils, p. 686. 3 Amsel (Jour. Soc. Chem. Ind. 1895, 605 ; 1896, 222) unnecessarily proposes for this well-known phenomenon the term “ water-reaction.” It should be noted that oils prepared with liquid driers (see p, 737) may legitimately contain small proportions of oil of turpentine. 4 Hefelman and Mann, ibid. 1896, 475. XII BOILED OIL 737 tion containing 100 grms. of lead acetate and 32 grms. of glycerin in 120 c.c. of water. One operates as follows:—1 c.c. of the ammonia solution is mixed with 5 c.c. of the lead solution, 12 c.c. of the sus¬ pected sample are added, and the whole is vigorously shaken together and then heated for three minutes to 100° C. On standing, if the sample be pure linseed oil, it will form two layers, the lower one being as clear as water, while if the sample contain boiled oil it will set to a soft viscous mass. Boiled oil may be readily differentiated from raw linseed oil by the presence of metals (“ driers ”), which are absent from the latter. The nature of the metal in the “ drier ” is ascertained by boiling, say, 30 grms. of the sample with dilute hydrochloric acid, and allow¬ ing to separate into two layers. The acid layer is syphoned off, and tested for metals (lead, manganese), or acids (boric, oxalic, etc.), in the usual manner. The solid “ driers ” (siccatives) are of late being replaced by “ soluble ” driers, which offer the advantage that they can be incor¬ porated with linseed oil not onlv at a comparatively low temperature —120° C.—but even in the cold, if they have been dissolved pre¬ viously in oil of turpentine. The “boiled oils” 1 prepared by either method possess equally high drying properties, provided the same amount of metal has been added. According to JFeger, 2 commercial soluble driers are either “ fused ” or “precipitated” driers, consisting of linoleates (salts of the mixed fatty acids from linseed oil) or resinates; it should be noted that the metals are exclusively, lead and manganese, other metals, such as copper, zinc, etc., yielding useless products. Lead salts alone are not used, as not imparting such drying properties as are yielded by manganese salts. In practice either manganese salts are used, or mixtures of manganese and lead salts. The following are the commercial products used as soluble driers : —Manganese resinate, mangano-lead resinate, manganese linoleate, and mangano-lead linoleate. “ Fused ” manganese resinate but rarely contains more than 3'2 per cent of soluble manganese, whereas the “ precipitated ” salt may contain as much as 6 to 7 per cent Mn.; “ fused ” manganese lino¬ leate contains 9-9’5, sometimes even 11 per cent Mn. “Precipitated” manganese linoleate is not a commercial product. In thf manufacture of boiled oil 2 to 3 per cent of “ fused ” man¬ ganese resinate, or mangano-lead resinate are used, or in their place 1 per cent of “fused” manganese linoleate, or 1 to 1*5 per cent of “ precipitated ” manganese resinate. The best proportion of lead salts to manganese salts appears to be 5 : 1, and the best commercial products contain 8 to 9 per cent of soluble lead and P5 to 2 per cent of soluble manganese. The valuation of a “ soluble ” drier cannot be based on the pro¬ portion of the metal as determined by incineration, inasmuch as oxide 1 The oils thus prepared are still termed by the trade “ boiled oils.” 2 Jour. Soc. Chem. Ind. 1896, 728. 738 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. held in suspension, and therefore not chemically combined with the linseed oil fatty acids or resin fatty acid, is useless as a drier. A good soluble drier must therefore be soluble in ether and (in the case of lead resinate) chloroform. In the analytical examination burn off the organic matter and determine the lead and manganese in the ash ; as the driers often contain sand, etc., the weighing of the ash would be useless. If calcium be present in any quantity, after separating the lead, estimate the manganese and calcium together as carbonates, and titrate the manganese; the calcium is then found by difference. Then ex-tract a fresh portion of the sample with ether or chloroform (in the case of a lead resinate), filter, wash, incinerate, and determine the manganese in the ash. The difference between the two amounts of manganese corresponds to the manganese present as soluble drier; the result may be checked by determination of the soluble manganese in an aliquot part of the ethereal extract. The soluble lead must be determined by difference, since the chloroform is only driven off com¬ pletely from the resinate solution at a red heat, tvhen the greater part of the lead also volatilises as chloride. The chemical change that takes place when boiled oil (or any drying oil) “dries” is very imperfectly understood. According to Bauer and Ilazura 1 the glyceride of linolenic acid (and perhaps in a higher degree the glycerides of linolenic acids) is at first converted into the glyceride of hydroxylinolic (resp. hydroxylinolenic acid); then anhydrides are formed. Mulder’s older statement that, in the first instance, all the glycerol is oxidised, is incorrect, as boiled oil contains considerable proportions of glycerol. (It has been pointed out already (p. 211) that the glycerol cannot be estimated by Benedild and Zsigmondy’s, or by Hehner’s method, as boiled oil contains, besides glycerol, other soluble substances that yield oxalic acid and are easily oxidised by chromic acid.) The last product of oxidation was hitherto assumed to be Mulder’s linoxyn, a neutral substance, insoluble in ether and possessed of somewhat elastic properties. Feid 2 how¬ ever, has shown that in course of time the “ linoxyn ” in its turn is converted into a viscous liquid heavier than water, and soluble in the latter to a considerable extent. This liquid is termed^ by Beid “ superoxidised linseed oil.” Fahrion is of the opinion 3 that, on drying, hydroxy acids are formed, basing his view on the fact that fatty acids insoluble in petroleum ether are obtained from boiled oil and linseed oil varnish (cp. D6gras-former, p. 699). Whether these acids are really hydroxy .acids, or have a more complex constitution, is open to doubt (cp. p. 204). Fahrion gives the following analyses of three samples of boiled oil; the oxidised acids 4 (hydroxy acids 1) have been determined by the method described page 204 :— 1 Jour . Soc. Chem. Ind. 1888, 680. 2 Ibid. 1894, 1020. 3 Ibid. 1894, 404. 4 I prefer this term to hydroxy acids, as the constitution of these acids is not known yet. XII BOILED OIL—LITHOGRAPHIC VARNISH 739 Boiled Oil. Consistency. Iodine Value. Acid Value. Oxidised Acids. Oxidised Acids in Oried Oil. No. 1 Somewhat thin and 101 -3 13'4 Pei' cent. 0-5 Per cent. 30-6 No. 2 fluid Very viscid 77 '3 24-9 4-1 20-8 No. 3 Tacky ; yielding “ strings ” 73-7 32-6 7-6 16-4 The “ dried oil ” was obtained by spreading the boiled oil on a glass plate in a very thin film, and exposing it to the air for ten days at a temperature slightly higher than the ordinary. Fahrion draws from these figures the conclusion that a boiled oil dries the better, and consequently is the more valuable, the less oxidised acids it contains. This opinion is confirmed by some statements of Leeds 1 on various qualities of linseed oil varnishes (lithographic varnishes), showing that the drying power of linseed oil varnishes diminishes as the boiling of the raw oil progresses. Thus, whereas “ thin ” litho¬ graphic varnishes dry about as well as raw linseed oil, the “ extra strong ” varnish can hardly be said to dry at all (cp. below). Boiled oil is extensively used in the manufacture of fatty (fixed) oil varnishes, made from linseed oil, various gum-resins, and oil of turpentine. The latter would be determined approximately, accord¬ ing to M c Ilhiney , 2 by distilling 25 grms. of the varnish with 100 c.c. of water in a distilling flask, Avhen the whole of the ethereal oil is stated to come over with the first 90 to 95 c.c. of distillate. The residue would, in the writer’s opinion, be best treated with alcohol in order to separate the gum-resin from the boiled oil. No test experiments having been made yet, this must be accepted with due reserve. 3. Lithographic Varnish Lithographic varnish is a perfectly clear, transparent substance ; if of the best quality it is but slightly darker than raw linseed oil. It often has a faintly reddish tint, and when prepared by boiling over fire (see below) it exhibits a more or less strongly marked green fluorescence. Lithographic varnish is obtained by boiling linseed oil at a higher temperature (say 260° to 300° C.) than that at which “boiled oil” is prepared. It further differs from the latter in that it is free from metals, no “ drier ” being added to the oil whilst boiling. According to the degree of consistency of the product several varieties are discerned in commerce. They are given in the following table (p. 740). “Burnt oil ” is a fairly quick drying varnish, which will form a strong skin in twenty-four to forty-eight hours at the ordinary 1 Jour. Soc. Chera. Ind. 1894, 203. 2 Ibid. 1895, 78. 740 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. temperature. It is obtained by heating raw linseed oil up to its flash point, and allowing it then to burn quietly, with constant stirring, until the required consistency is reached. I subjoin the result of an examination of several lithographic varnishes, to which, for the sake of comparison, is added that of raw linseed oil. The oxidised acids, termed “ Fahrion’s acids ” by Leeds, have been determined as described page 204. Lithographic Varnishes prepared by Boiling over Fire. Specific Gravity at 15° C. Free Acids calculated as Oleic Acid. Saponifica¬ tion Value. Mgrms. KOH. Unsaponi¬ fiable Matter. Oxidised Acids. Iodine Value. Raw linseed oil . 0-9321 Per cent. 0-85 194-8 Per cent. Per cent. 0-30 169-0 “ Tint ” varnish 0-9584 1-46 197-5 1-50 113-2 “ Thin ” varnish 0-9661 1-76 196-9 0-62 2-50 ioo-o “Middle” varnish 0-9721 1-71 197-5 0-85 4-20 91-6 “ Strong ” varnish 0-9741 2-16 190-9 0-79 6 "50 86-7 “Extra strong” varnish “Burnt” thin varnish 0-9780 2-51 188-9 0-91 7-50 83 -5 0"9675 6-93 195"5 1-35 0-85 92-7 The mixed fatty acids, derived from the raw linseed oil and the varnishes, and freed from the unsaponifiable matter, gave the following results :— Mixed Fatty Acids from Lithographic Varnishes. Specific Gravity at 15-5° C. Melting Point. °C. Solidify¬ ing Point. °C. Mean Combining Weight. Saponifica¬ tion Value. Mgrms. KOH. Iodine Value. Raw linseed oil . 0-923 24-26-5 286-5 195-8 145-5 “ Tint ” varnish . 0-941 20-5 15 118-3 “ Thin ” varnish 0-949 22 18 108-8 “ Middle ” varnish 0-950 24 22 272-6 205-8 97-7 “ Strong ” varnish 0-953 25-5 24 270-1 207-7 87-3 “Extra strong” varnish 0-955 27 23 269-8 207-9 90-8 “ Burnt ” thin varnish ... 23 19 99-3 Another method of preparing linseed oil varnish consists in treat¬ ing linseed oil with oxygen in jacketed pans heated by steam. The oil gains thereby in weight, and the product obtained is a pale oil, not darker than the raw oil, and free from the fluorescence character¬ istic of the oils obtained by boiling over fire. The following table gives the physical and chemical characteristics of these oxidised oils and of their mixed fatty acids, in juxtaposition with those of a sample of a dried oil, obtained from a raw linseed oil by exposure in a flat dish to a moderate current of air at 45' C. for about five weeks, the skin formed being daily broken up and mixed XII LITHOGRAPHIC VARNISH—LINOLEUM 741 with the bulk. This dried linseed oil had a jelly-like consistency, lumps of comparatively hard material and skin alternating with a small quantity of oil of the consistency of “ middle ” varnish :— Varnishes prepared by Treatment with Oxygen Oils. Specific Gravity at 15° 0. Free Acid calculated as Oleic Acid. Saponifica¬ tion Value. Mgrms. KOH. Unsaponi- fiable Matter. Oxidised Acids. Iodine Value. Oxidised oil, weak 1-03 Per cent. 18 - 28-4 1 221 Per cent. 0-89 Per cent. 42-82 58-8 „ „ strong Dried linseed oil . 1-05 18-49-28'9 1 223-5 0-97 44-19 53-5 12-67 171-6 0-81 31-58 93-9 Mixed Fatty Acids. Melting Point. Solidifying Point. Mean Combining Weight. Saponifica¬ tion Value. Iodine Value. °C. °C. Oxidised oil, weak . 28 26 241-4 232-4 63-2 „ „ strong . Dried linseed oil 27 25 242-5 231 -3 60-6 26 22 268-8 20S-7 100-3 The oxidised oils are much more readily soluble in alcohol, and, especially the sample “ oxidised oil, weak,” possessed more strongly marked drying poivers than the ordinary varnishes. They are satu¬ rated with gas which causes them to effervesce on heating. Linoleum J Linseed oil intended for the manufacture of linoleum is exposed to air or treated with oxygen until the maximum amount of oxygen has been absorbed. The product thus obtained forms a yellow gelatinous mass, which can be drawn into “ strings.” It is heavier than water, and insoluble in alcohol, ether, chloroform, and carbon bisulphide. This mass, mixed with resin, rasped cork, and “fillers,” serves as the raw material for linoleum. Linoleum is, as a rule, valued by so-called “ practical ” tests. 3 Still, chemical analysis will reveal an excessive amount of ash, and extraction of linoleum with ether will show whether the oil used had been dried completely. The larger the amount of extract the less valuable is the linoleum. 1 The first of these figures was found when the pink colour of the phenolphthalein remained after a vigorous shaking ; but it disappeared after a short time, and more alkali was run in until the pink colour remained constant for two or three minutes ; thus the second figure was obtained (cp., however, Jour. Soc. Chem. Ind. 1890, 847). 2 Cp. W. F. Reid, Jour. Soc. Chem. Ind. 1896, 75. 3 Cp. also Buchartz, ibid. 1895, 587. 742 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. The following three analyses of linoleum are due to Pinette ; 1 it may be added that this observer erroneously considers the sample No. 3, yielding the largest amount of ether-soluble oil, the best:— Samples of Linoleum No. 1. No. 2. No. 3. Water .... 3-39 3-01 3-41 Linseed oil (ether-soluble). 10-43 10-60 19-58 Cork (by difference) . 77-24 73-63 54-16 fSilica .... 2-94 3-99 4-31 _ Alumina 1-91 4-94 0-61 -J Ferric oxide . 1-78 1-79 8-86 Lime .... 6-17 lAlkalis, etc. . 1-31 2-04 2-90 ioo-o ioo-o ioo-o H. VULCANISED OILS Rubber Substitutes French —Gomme fadice. German— Faktis. Vulcanised oils are prepared from fatty oils either by heating with sulphur, or by treatment with sulphur chloride in the cold. 2 According to the process used they are distinguished in the trade as “ brown ” (black) and “ white substitutes ” respectively. The “ white substitutes ” contain, therefore, a considerable proportion of chlorine, which is, of course, absent in the “ brown (black) substitutes ” ; thus it is possible to easily distinguish the two classes of substitutes by chemical means. The substitutes are india-rubber like substances, and serve, as their name indicates, to replace india-rubber. The white substitutes form a yellowish, elastic, crumbly substance of oily smell and neutral reaction; the brown (black) substitutes occur in commerce either as sticky lumps or in a ground state. Being derivatives of fatty oils, the quantitative reactions naturally lend themselves as suitable methods for their examination, supple¬ mented, of course, by such tests as the nature of the substance requires. 3 Thus the sulphur is determined by treating the substitute with fuming nitric acid in the presence of silver nitrate and subsequent fusing with caustic potash and potassium nitrate, the insoluble silver compounds retaining the chlorine. The following table contains a number of analyses of india-rubber substitutes by Henriques 3 :— 1 Jour. Soc. (Jhern. Ind. 1892, 550. 2 Cp. p. 282. 3 Jour. Soc. Cliem. Ind. 1894, 47, 70. VULCANISED OILS WfMOOOOMiC^J^HCO CO . C u H 29 - CH = CH - CHo - COOH Oleic acid. yields so'h oh and (2) C 14 H 29 - CH - CH - CH., - COOH /3-Sulphostearic acid. As there is no reason why one acid should be formed in prefer¬ ence to the other, it may be assumed that both acids are formed in equal proportions. These acids are not very stable, and by merely allowing the crude product to stand, enough moisture is absorbed to produce a partial splitting up into S0 4 H 2 and hydroxy acids, thus— 7 P P (1) C J4 H 29 - CH - CH - CH, - COOH + H.,0 = C 14 H 29 - CH 2 - CH - CH 2 - COOH + S0 4 H 2 SO :3 H OH OH (3-Hydroxystearic acid. 7 P 7 (2) C 14 H 29 - CH - CH - CH 2 - COOH + H.,0 = C ]4 H 29 - CH - CH 2 - CH 2 - COOH + S0 4 H 2 OH SO :i H OH y-Hydroxystearic acid. The latter acid — y - hydroxystearic acid — immediately undergoes dehydration with formation of y-stearolactone (p. 69). Another portion of the sulphostearic acid remains unchanged, but on boiling the crude mass with water the undecomposed portion is also converted into f3 -hydroxystearic acid and stearolactone, as shown. In the subsequent distillation of the washed product the stearo¬ lactone already formed passes over unchanged, as also part of the ^-hydroxystearic acid, whereas another part is converted by dehydra¬ tion into oleic and isooleic acids, thus— (1) C 14 H 29 -CH 2 -CH- CH, -COOH - H 2 0 = C 14 H 29 - CH = CH - CH 2 - COOH OH (2) C 14 H 29 -CH.,-CH-CH 2 -COOH Oleic acid. I OH - HoO = C 14 H 29 - CH 2 - CH = CH - COOH It is evident that unless distillation can be avoided, a complete conversion of oleic acid into solid products cannot be thus obtained. In the “acid saponification” process the interaction takes place at a high temperature, and it is therefore readily intelligible that, the chemical changes involved being of a reversible nature, a limit is reached beyond which the proportion of oleic acid cannot be reduced. XII RAW MATERIAL FOR CANDLES 749 David’s 1 statement that 18-20 per cent of stearolactone are formed in tehe cold by washing the product of interaction of oleic and sul- phuiric acids with an equal volume of water, removing the acid layer, dissolving the oily layer in an equal volume of water, and allowing to stand for twelve hours, has been controverted by Lewkowitsch , 2 who has shown that the separated crystals are practically nothing but /?-h ydroxystearic acid. Examination of the Raw Material of the Candle Industry The raw material of the candle industry is valued on the solidify- ing point of the fatty acids ; the higher this is, the greater will be the yield of solid fatty acids. The proportion of water and of non-fatty substances is also taken into account. In the following lines the methods employed for the valuation are shortly summarised. The sample is drawn carefully in the manner described page 87. Waiter may be determined, according to II. Norman Tate , 3 by heating- 50 grms. in a porcelain crucible, or better in a silver crucible, to 130 C., and keeping it thereat until bubbles cease to be given off, and the melted fat is in a condition of calm fusion without giving off vapour. The fat is then allowed to cool, and is weighed. The loss indicates the moisture (cp. also p. 88). Impurities—not-fats—are determined as described p. 88. It should, however, be mentioned that in the case of bone fat containing glue and lime soaps, different results are obtained according as the fat is extracted after previous drying, or is extracted undried. The method employed should, therefore, be stated distinctly when return¬ ing the results of the analysis. According to the “French method” the undried fat is extracted. Solidifying Point of the Fatty Acids. Tallow Titer The “titer test” has been fully described p. 134. It is necessary to pay the greatest attention to this determination, the practical yield of candle material depending in a great measure on its accuracy. Dalican weighs off 50 grms. of fat, and employs the mixed fatty acids obtained from it for the “ titer test.” The following is an empirical table compiled by Dalican, giving the percentages of stearic and oleic acids for the solidifying points of tallow stated. The total yield of fatty acids is taken as 95 per cent, and that of the (9'68 per cent glycerol-yielding) radicle C 3 H 2 as 4 per cent, 1 per cent being allowed for water and impurities. 1 Jour. Sue. Chew,, hid. 1897, 339. “ Ibid. 1897, 390. 3 The Examination of Tallow, Liverpool, 1888. 750 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. Solidifying Point. Stearic Acid. Oleic Acid. C. Per cent. Per cent. 35 25-20 69-80 35 - 5 26 -40 68-60 36 27-30 67-70 36 - 5 28-75 66 -25 37 29-80 65-20 37-5 30-60 64-40 38 31-25 63"75 38 - 5 32-15 62-85 39 33-44 61 "55 39-5 34-30 60-80 40 35-15 59-85 40-5 36-10 58-90 41 38-00 57-00 41-5 38-95 56 '05 42 39-90 55-10 42-5 42-75 52-27 43 43-70 51-30 43'5 44-65 50-35 44 47-50 47 "50 44'5 49-40 45-60 45 51-30 43-70 45 ‘5 52-25 42-75 46 53-20 41-SO 46-5 55'10 39-90 47 57-95 37 "05 47-5 58-90 36-10 48 61 '75 33-25 48’5 66 "50 28-50 49 71-25 23 - 75 49 - 5 72-20 22-SO 50 75’05 19-95 50-5 77-10 17-90 51 79-50 15-50 51-5 81-90 13-10 52 84-00 11-00 52 *5 88-30 6 "70 53 92-10 2-90 Be Schepper and Geitel 1 recommend each candle-works chemist to construct an empirical table for his own use, from which the yield of candle material may be found at once. It goes, of course, without saying that a table of this kind holds good only for the particular works for which it is constructed, as the solidifying points of the mixed fatty acids and the yields of candle material naturally vary considerably according as lime saponification or sulphuric acid saponi¬ fication is employed. Such an empirical table is made by mixing “ stearine ” and oleic acid, prepared in the works, in known proportions, and determining the solidifying points of these mixtures. Of course, for each kind of fat a separate table must be constructed. As an example we give the following table of Y. de Schepper and Geitel , used in the candle- works of Gouda (Holland) for tallow and palm oil. The process em¬ ployed is sulphuric acid saponification. The yields of “ stearines ” of 1 Dingl. Polyt. Jour. 245. 295. XII RAW MATERIAL FOR CANDLES 751 different solidifying points are recorded as obtained from the saponified mass by expressing it at different temperatures. The “ stearines ” solidifying at 48° C., 50° C., and 52 C. differ from those having a higher solidifying point most likely by a higher proportion of isooleic acid. Solidifying. Point. Percentage of “ Stearine ” of Solidifying Point stated. Palm Oil. Tallow. 'C. 48° 50° 52° 55'4° 48° 50° 52° 54-S° 5 10 4'2 3-6 3 -3 2-6 3 *2 2 "7 2-3 2-1 15 10-2 9-8 7-8 6-6 7-5 6‘6 5-7 4-8 20 17-4 15-0 14-4 11-0 13-0 11-4 9-7 8-2 25 26-2 22-4 19-3 16-2 19-2 17-0 14-8 12-6 30 34-0 30-5 26-6 22-3 27-9 23-2 21-4 18-3 35 45’6 40-S 35-8 29-8 39-5 34-5 30-2 25-8 36 48‘5 43-2 38-0 31-8 42-5 36 9 32-5 27"6 37 5L8 45‘5 40-3 33-6 46-0 40-0 34-9 29-6 38 55-5 48-8 42-6 35-8 49-5 42-6 37"5 32-0 39 59-2 51-8 45 "6 38-2 53-2 45-8 40-3 34-3 40 63-0 55"2 48-6 40-6 57-8 49-6 43-5 37-0 41 66 - 6 58-7 52-0 43-0 62-2 53-5 47-0 40-0 42 70"5 62-2 55"2 45 "5 66"6 57-6 50-5 42-9 43 74-8 66-0 58-8 48-5 71-8 62-0 54-0 46-0 44 79-2 70-2 62-0 51-4 77-0 66"2 58-4 49-8 45 84'0 74 - 5 66-0 54 -3 81-8 71-0 62-6 53-0 46 89-4 78-8 69-8 57-8 87-5 75-8 67-0 56-8 47 94-3 83-0 74-0 61-0 93-3 80-9 71-5 60-S 48 100-0 88-0 78-6 65-0 100-0 87-2 76-6 65-0 49 94-2 83-5 89-1 ... 93-0 84-7 69-5 50 ... 100-0 89-0 73-4 ... 100-0 87-0 74’5 51 ... 94-5 78-0 93-5 79-8 52 ... 100-0 82-8 ... 100-0 84-8 53 87-6 ... 90-1 54 92-2 95-3 55 97-5 (54-8) 100-0 55-4 ... 100-0 The actual proportion of true stearie acid in the mixed fatty acids is ascertained by Hehner and Mitchell's method (chap. viii. p. 198). As a measure of the proportion of oleic acid or “ oleine,” the iodine value may be determined; the lower this is, the more valuable tie material will be for candle-making. It should, however, be borne in mind that also isooleie acid, absorbing as much iodine as ordinary oleic acid, is suitable for the candlemaker’s purposes on account of its high melting point, 45° C. The amount of glycerol obtainable in the saponification process is ■calculated from the ether value (p. 208), if neutral fats be used. Adulterants in the raw material of candle-works are detected according to the methods detailed above under tallow (p. 596). 752 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. Control of the Saponification Process in Candle-Works and Examination of the Intermediate Products In order to ascertain how far saponification of the fats has pro¬ ceeded in the autoclaves, a sample is drawn from time to time, and the ratio of neutral fat to free fatty acids determined. The sample is boiled with water in the case of products from the acid process, and in the case of lime saponification with dilute sulphuric acid, so as to isolate the fatty substance. Then the acid value, A, and the saponifi¬ cation value,- K, of the sample are determined. Adopting 95 per cent of fatty acids as the yield from neutral fats, the ratio in which the free fatty acids, F, stand to the undecomposed neutral fat, N, at the time the sample was taken is given by the following proportion F:N = A : 1’053(K — A). A shorter method, naturally commending itself in those cases where palm oil (containing large proportions of free fatty acids) is mixed with neutral fats, is to determine K once for all at the outset, or, to save calculation, the number of c.c. of a potash solution, which need not he standardised, and then to ascertain the number of c.c., required for neutralising the free acids of the sample with the same potash solution. The quotient then gives the percentage of free fatty acids in the sample. The following table illustrates the sampling of tallow saponified in an autoclave, 3 per cent of lime being used :— The Sample taken after Free Fatty Acids. Per cent. The 1st hour contained . . . . 38 - 55 ,, 2nd ,, ,, .... 77'40 ,, 3rd ,, ,, • • • • 83 '9 „ 4th ,, .... 87-5 „ 5th ,, .... 88-6 ,, 6th ,, .... 89-3 ,, 7th ,, ,, .... 93‘0 ,, 8th ,, ,, • • • • 97'5 ,, 9th ,, „ .... 98 Y ,, 10th ,, . • . • 98-6 The proportion of oleie acid in the press-cakes and in the “ red oil ” is determined in the case of products from the lime saponification process by HubVs iodine absorption method. In the case of products from the sulphuric acid saponification separation of the lead salts by means of ether must be resorted to (p. 192). Y. cle Scheppel and Geitel use also for press-cakes the table given p. 751. They find the “ stearine ” in “ red oils ” from the following table after saponifying the sample in order to hydrolyse any undecomposed neutral fat, and determining the solidifying point of the liberated fatty acids. The table has been compiled empirically by mixing together “ oleine ” of XII OLEIC ACID IN PRESS-CAKES 753 solidifying point 5'4° C. and “ stearine ” of solidifying point 48° C. in the proportions stated, and subsequently determining the solidifying points of the mixtures. Solidifying Point of the Mixture. Stearine of Solidifying Point 48° 0. Solidifying Point of the Mixture. Stearine of Solidifying Point 48° C. Solidifying Point of the Mixture. Stearine of Solidifying Point 48° C. °C. Per cent. °C. Per cent. °C. Per cent. 5*4 20 12-1 35 39-5 6 0-3 21 13-2 36 43-0 7 0-8 22 14-5 37 46-9 8 1-2 23 157 38 50-5 9 17 24 17-0 39 54-5 10 2-5 25 18-5 40 58'9 11 3-2 26 20-0 41 63*6 12 3'8 27 217 42 68-5 13 4-7 28 23-3 43 73-5 14 5-6 29 25-2 44 78-9 15 6-6 30 27'2 45 83-5 16 7-7 31 29'2 46 89-0 17 8-8 32 31-5 47 94-1 18 9'8 33 33-8 48 100-0 19 11-1 34 36-6 ... I The following table, calculated by Mangold , 1 gives the proportions of “ stearine ” and oleic acid for the iodine values found. It refers to the products obtained from tallow and palm oil by means of lime saponification :— 1 Marazza-Mangold, Die Stearinindustrie, p. 168. 3 C [Table 754 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. Iodine Value. Product contains Iodine Value. Product contains Iodine Value. Product contains Oleic acid. Per cent. “ Stearine.” Per cent. Oleic acid. Per cent. “Stearine.” Per cent. Oleic acid. Per cent. “Stearine.” Per cent. 0 0 100 31 34-41 65-59 62 68-83 31-17 1 1-11 98-89 32 35-52 64-48 63 69-94 30-06 2 2-22 97-78 33 36-63 63-37 64 71-05 28-95 3 3-33 96-67 34 37-74 62-26 65 72-16 27-84 4 4-44 95-56 35 38-85 61-15 66 73-27 26-73 5 5-55 94-45 36 39-96 60-04 67 74-38 25-62 6 6-66 93-34 37 41-07 58-93 68 75-49 24-51 7 777 92-23 38 42-18 57-82 69 76-60 23-40 8 8-88 91-12 39 43-29 56-71 70 77-71 22-29 9 9-99 90-01 40 44-40 55-60 71 78-82 21-18 10 11-10 88-90 41 45-51 54-49 72 79-93 20-07 11 12-21 87-79 42 46-62 53-38 73 81-04 18-96 12 13-32 86-68 43 47-73 52-27 74 82-15 17-85 13 14-43 85-57 44 48-84 51-16 75 83-26 16-74 14 15-54 84-46 45 49-95 50-05 76 84-37 15-63 15 16-65 83-35 46 51-06 48-94 77 85-48 14-52 16 17-76 82-24 47 52-17 47-83 78 86-59 13-41 17 18-87 81T3 48 53-28 46-72 79 87-70 12-30 18 19-98 80-02 49 54-39 45-61 80 88-82 11-18 19 21-09 78-91 50 55-50 44-49 81 89-93 10-07 20 22-20 77-80 51 56-62 43-38 82 91-04 8-96 21 23-31 76-69 52 57-73 42-27 83 92-15 7-85 22 24-42 75-58 53 58-84 41-16 84 93-26 6-74 23 25-53 74-47 54 59-95 40-05 85 94-37 5-63 24 26-64 73-36 55 61-06 38-94 86 95-48 4-52 25 2775 72-25 56 62-17 37-83 87 96-59 3-41 26 28-86 71-14 57 63-28 36-72 88 97-70 2-30 27 29-97 70-03 58 64-39 35-61 89 98-81 1-19 28 31-08 68-92 59 65-50 34-50 90-07 100 0 29 32-19 67-81 60 66-61 33-39 30 33-30 66-70 61 67-72 32-28 Candle Material—Candles The commercial examination of the candle material, or of the finished stearine candles, embraces the determination of the melting and solidifying points of the fatty substance, the determination of any unsaponified fat, and the detection of carnaiiba wax, paraffin wax, cerasin, and cholesterol. Neutral fat and hydrocarbons are detected qualitatively as de¬ scribed p. 100. Neutral fat may be due either to incomplete saponification or to intentional admixture, as in the case of “ composite candles ” (night lights), consisting of a mixture of “ stearine ” and cocoa nut stearine. If the quantity of neutral fat is but small, the determination of the ether value does not lead to accurate results. In such cases it is safer to saponify 20 to 50 grms. of the sample and to determine the glycerol (p. 207). The amount of glycerol multiplied by ten gives the proportion of neutral fat. XXI CANDLE MATERIAL 755 Hydrocarbons in candle material may be either due to destruction of the fatty acids having taken place in the distillation process to some extent or to admixture with paraffin wax or cerasin. Cholesterol may be due to presence of “ distilled grease stearine.” These substances are detected as described p. 224. Carnaiiba wax may have been added to increase the solidifying point of the candle material (chap. xi. p. 651). It is easily detected by employing the methods given in chaps, vii. and viii. Colouring 1 matter will but rarely engage the attention of the analyst. At present aniline colours are used chiefly for fancy candles, and poisonous colours containing arsenic and copper have almost dis¬ appeared from candle-works. It is also possible to decide by which process a given candle material has been prepared if the following points are borne in mind. Saponification stearine (“saponified stearine”) consists of stearic and palmitic acids, with but insignificant amounts of oleic acid. Distillation stearine (“distilled stearine”) contains considerable amounts of isooleic acid (the candle material obtained by the zinc chloride process consists chiefly of stearolactone and oleic acid). Distilled grease stearine contains notable quantities of cholesterol (cp. also p. 691). The determination of each of these substances has been described in chap, vii., and it may therefore suffice to state that “ distillation stearine” has a considerable iodine number, say up to 15, due to presence of isooleic acid, and that stearolactone is detected by its constant ether value (p. 206). The proportion of stearic aeid is estimated by Iieliner and Mitchell’s method described p. 198, the amount of oleie aeid is deter¬ mined as described p. 197, and the proportion of palmitic acid is taken by difference. By-PRODUCTS of the technical saponification processes are glycerin (cp. p. 786), oleic acid (cp. Wool Oils, p. 704, Textile Soaps, p. 784), and stearine pitch, the residue left in the stills after the fatty acids have been distilled off. Stearine pitch 1 —candle tar ( Goudron) —contains small quantities of free fatty acids and neutral fat—together about 10 per cent—and chiefly hydrocarbons due to destructive distillation. It is used for making oil gas, as a lubricant for hot neck rollers, and as insulating material for electric cables 2 by mixing with sulphur and heating from 120° to 175° C. 3. Wax Candles The examination of wax candles is identical with that of bees¬ wax : the reader is therefore referred to the section on “ Beeswax ”' 1 Jour. Soc. Chem. Ind. 1894, 380. 2 Eng. Pat. No. 3045, 1894. 756 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. (p. 655). As wax candles are not moulded, but “drawn,” it may be advisable in some cases to peel off the several concentric layers and examine each layer separately, or at least the innermost and outer¬ most layers. Under the name “ wax candles ” a material is sometimes sold not containing any beeswax whatever; the following analysis gives the composition of a candle of this kind :— Carnaiiba wax . . . .60 per cent. “Stearine” . . . . 25 ,, ,, Cerasin . . . . . 15 ,, ,, 4. Sperm Candles Sperm candles, i.e. candles made from “ spermaceti,” are at present almost exclusively used as the standard for photometrical measure¬ ments by gas examiners in this country. Pure spermaceti cannot be employed very well for candles, the material being too brittle ; beeswax, tallow, stearine, paraffin wax, and cerasin are therefore admixed with it. These admixtures are detected according to the directions given pp. 664-669. The rules for the preparation of standard sperm candles for photo- metrical purposes, published by the Metropolitan Gas Referees, 1 prescribe that for the purpose of rendering spermaceti less brittle, best air-bleached beeswax, melting at or about 144° F. (62° C.), shall be used (and no other material), and that the proportion of beeswax to spermaceti shall be not less than 3 per cent, nor more than 4‘5 per cent. The spermaceti itself shall be so refined as to have a melting point lying between 112° F. and 115° F. (45°-46° C.) The melting point is to be determined as follows :— “ A small portion of the spermaceti is melted by being placed in a short test-tube, the lower end of which is then plunged in hot water. A glass tube drawn out at one end into a capillary tube about 1 mm. in diameter is dipped, narrow end downwards, into the liquid sperma¬ ceti, so that when the tube is withdrawn 2 or 3 mm. of its length are filled with spermaceti, which immediately solidifies. The corre¬ sponding part of the exterior of the tube is also coated with sperma¬ ceti, which must be removed. The narrow part of the tube is then immersed in a large vessel of water of a temperature not exceeding 100° F. (37'8° C.) The lower end of the tube, which contains the spermaceti, should be three or four inches below the surface, and close to the bulb of a thermometer. The upper end of the tube must be above the surface, and the interior of the tube must contain no water. The water is then slowly heated, being at the same time briskly stirred, so that the temperature of the whole mass is as uniform as possible. When the plug of spermaceti in the tube melts, it will be forced up the tube by the pressure of the water. The temperature at the moment when this movement is observed is the melting point.” 1 Jour. Soc. Chem. Ind. 1894, 65. XII PARAFFIN WAX CANDLES 757 5. Paraffin Wax Candles Piaraffin wax consists principally of a mixture of hydrocarbons, being the higher members of the ethane series, C ft H 2 ., l+2 . Pairaffin wax is white, translucent, crystalline, and free from taste and odour; it can be distilled unchanged. Tlhe melting and solidifying points, as also the specific gravities of various qualities of paraffin, vary very much, according as hydro¬ carbons of lower or higher melting points preponderate. In commerce two brands are recognised: hard paraffin wax and soft paraffin wax. The subjoined table, due to Tervet, 1 gives the melting points of each of twenty successive fractions into which three paraffin waxes of the melting points given below had been resolved. The temperatures- are deigrees Fahrenheit. Melting Points of Fractions obtained from Paraffin Waxes No. of Fraction. Of Melting Point 126° F. Of Melting Point 111° F. Of Melting Point 102° F. 1 119-0 103-0 94-0 2 120-0 104-0 94-0 3 120-5 104-5 95-0 4 121-0 105-0 96-0 5 121-0 106-0 96-0 6 121-0 107-0 97-5 7 121-5 107-5 98-0 8 122-0 108-0 98-5 9 122-5 108-5 99-0 10 123-0 109-0 99-0 11 124-0 110-5 100-0 12 125-0 112-0 102-0 13 126-0 113-0 103-5 14 127-0 113-5 105-0 15 128-0 114-5 106-5 16 129-0 116-0 108-0 17 130-0 117-0 109-0 18 132-0 119-0 1100 19 134-0 123-0 112-5 20 138-0 125-0 113-0 The melting and solidifying points of paraffin waxes almost coincide. The relation between the solidifying point of paraffin wax and its density in the solid and liquid state is shown in the following table :— 1 Jour. Soc.'Chem. Ind. 1887, 356. 758 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. Specific Gravity of Paraffin Waxes (Allen ) 1 No. Origin of Sample. Specific Gravity. Solidifying Point. Solid, at 15° C. Liquid, at 99° C. °C. 1 Shale oil . 0-8666 0-7481 44-0 2 ?) J) * 0-8961 0-7494 47-0 3 0-9000 07517 52-0 4 American petroleum. 0-9111 0-7572 58-5 5 0-9083 0-7535 53-8 6 Ozokerit . 0-7531 61-5 7 Rangoon tar 0-8831 0-7571 49-0 The following table gives the specific gravities of refined American paraffin waxes, determined in the melted state at the temperatures stated:— Specific Gravities of Melted Paraffin Waxes (I. I. Redwood ) 2 °P. at which determined. Melting Point 108° F. Melting Point 114° F. Melting Point 120-5° F. Melting Point 122-25° F. Melting Point 122-75° F. Melting Point 12S'25° F. Melting Point 133-25° F. 160 0-77069 0-77193 0-77391 0-77079 0-77023 0-77573 0-77723 155 0-77119 0-77330 0-77531 0-77149 0-77163 0-77653 0-77853 150 0-77309 0-77473 0-77657 0-77319 0-77283 0-77803 0-78003 145 0-77509 0-77620 0-77777 0-77519 0-77463 0-77973 0-78153 140 0-77679 0-77763 0-77847 0-77689 0-77633 0-78133 0-78333 135 0-77899 0-77953 0-78147 0-77869 0-77843 0-78303 130 0-78049 0-78113 0-78267 0-78029 0-77973 125 0-78199 0-78343 0-78441 120 0-78359 0-78473 115 0-78529 • Specific Gravities of Solid Paraffin Waxes at 60° F. (I. I. Redwood) Melting Point 106° F. Melting Point 111-5° F. Melting Point 120-5° F. Melting Point 122-25° F. Melting Point 125-75° F. Melting | Point 131° F. 0-87525 0-88230 0-89895 0-90105 0-90350 0-90865 The behaviour of paraffin wax with solvents has been studied by Pawlewski and Filemonewicz. 3 The following table gives the solubility at 20° C. of ozokerit paraffin, of spec. grav. 0-9170 at 20° C., melting at 64°-65° C., and solidifying at 61°-63° 0. :— 1 Comm. Org. Anal. vol. ii. 411. 2 Jour. Soc. Chem. Ind. 1889, 163. 3 Jour. Chem. Soc. 1889, Abstr. 82. XII PARAFFIN WAX 759 Solvent. Grins, of Ozokerit Paraffin Wax dissolved by Weight of Solvent required to dissolve completely 100 grms. 100 c.c. I Part of Paraffin Wax. Carbon bisulphide .... 12-99 7-6 Petroleum ether, boiling up to 75° C.; spec. grav. = 0"7233 11-73 8-48 8-5 Oil of turpentine ; spec. grav. =0'857, boiling point 158°-166° C. 6-06 5-21 16-1 Cumene comm, up to 160° C. ; spec, grav. = 0'867. .... 4-28 3-72 23-4 Cumene fraction., 150°-160° C.; spec, grav. = 0 ‘847 ..... 3-99 3-39 25-0 Xylene comm. B.P., 135°-143°C.; spec, grav. =0’866. .... 3-95 3-43 25-1 Xylene fract., 136°-138° C. ; spec, grav. =0'864 . .... 4-39 3-77 22-7 Toluene comm., 108°-110° C.; spec, grav. =0 - 866 .... 3-83 3-34 26-1 Toluene fract., 108'5-109'5° C. ; spec, grav. =0 - 866. .... 3-92 3-41 25 "5 Chloroform ..... 2-42 3-61 41-3 Benzene ...... 1-99 1-75 50-3 Ethyl ether ..... 1-95 50-8 Isobutyl alcohol, spec. grav. = 0 - 804 . 0-285 0-228 352-9 Acetone, 55 - 5°-56'5° C. ; spec. grav. = 0797 . 0-262 0-209 378-7 Ethyl acetate ..... 0-238 419-0 Ethyl alcohol, 99 5° Tr. 0-219 453-6 Amyl alcohol, 127°-129° C.; spec. grav. = 0-813. 0-202 0-164 495-3 Propionic acid ..... 0-165 595-3 Propyl alcohol. 0-141 709-4 Methyl alcohol, 65-5 0 -G6"5° C. ; spec. grav. = 0"798 ..... 0-071 0-056 1447-5 Methyl formate. 0-060 1648-7 Glacial acetic acid .... 0-060 0-063 1668-6 Ethyl alcohol, 64'3° Tr. 0-046 2149-5 Acetic anhydride .... 0-025 3856-2 Formic acid (cryst.) .... 0-013 0-015 7689-2 Ethyl alcohol, 75° Tr..... 0-0003 330000-0 Holde 1 records the following data :— 100 c.c. of 95-5 per cent alcohol dissolve (P031 grm. 100 „ of 98-5 „ „ 0-029 grm. of paraffin wax, melting point 55°-56° (origin not stated). EXAMINATION OF THE RAW MATERIAL In crude paraffin wax, or “ scale,” as the term runs, there are present varying quantities of impurities or “ dirt,” water, and hydro¬ carbons of lower melting point, consisting mostly of “ soft ” paraffin. The latter, being valueless to the candlemaker, is termed “ oil.” There 1 Chem. Revue, 1897, 6. 760 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. is no sharp line of demarcation between the solid hydrocarbons and the “oil,” these passing gradually through “soft” or low melting point paraffins into each other. The amount of “ oil ” pressed out in practical working depends naturally on various circumstances, such as temperature, pressure, length of time during which pressure is applied, and it will thus be readily understood that a laboratory test for “ oil ” must be an arbitrary one. In commerce, methods of testing must, therefore, be arranged by buyer and seller. A method of this kind agreed upon by the Scottish Mineral Oil Association and certain Representative Purchasers for the sampling and testing of scale is the following : 1 — Sampling 1 of Seale. —The sample is taken by means of a metal tube, slightly conical, so that a cylindrical core of paraffin is obtained. Immediately after the sample has been drawn it is thoroughly mixed, placed in suitable wide-mouthed bottles, which may be closed either with glass stoppers or good corks ; if the latter are used, they should be covered with paraffin paper or soaked in melted paraffin wax before being inserted. The scale should be tightly packed into and completely fill the bottles, as otherwise partial evaporation may occur, and moisture may condense in the upper portion. The bottles are then finally sealed in the usual manner. Determination of Dirt in Seale. —The amount of dirt (fibres of press cloths, sand, etc.) in scale is determined by melting a weighed quantity—not less than 7000 grains (453-58 grms.)—and, after sub¬ sidence, pouring off the clear paraffin. The residue is then mixed with naphtha or petroleum ether, thrown on a weighed dry filter paper, washed with naphtha or petroleum ether, dried, and weighed. Determination of Water in Seale. —The amount of water present in scale may be determined by either of the following processes, the determination by “ subsidence ” 2 having been abandoned as leading to erroneous results :— (a) Distillation from a Copper Flask. —From 1 to 2 lbs. of the scale are heated in a copper flask connected to an ordinary Liebig con¬ denser. The flask should be about 11" high, 8" in diameter at the bottom, and 1J" at the mouth. By means of a powerful Bunsen burner the water is volatilised and then condensed, a small quantity of light oil passing over at the same time. The distillate is received in a narrow graduated measure, so that the volume of water can be readily ascertained. As a little water usually adheres to the sides of the condenser tube, this must be washed off with petroleum ether or naphtha, previously saturated with water, and added to the principal quantity. (b) Price’s Company’s Method. —500 grains (32-4 grms.) of the scale to be tested are weighed in a porcelain basin, and heated with con¬ stant stirring to 230° F. (110° C.), until bubbles cease to be given off; the loss is then determined. 500 grains (32'4 grms.) of the same scale, which has been freed of 1 Jour. Soc. Chem. Ind. 1891, 346. 2 Sutherland, ibid. 1887, 123. xrr PARAFFIN WAX 761 its water and dirt by melting at a gentle heat and by subsidence, are heated in the same way to the same temperature for the same length of time, and the loss is determined. The loss in the second instance is now deducted from the loss in the first experiment, and the differ¬ ence is taken as the quantity of water present. Determination of Oil in Seale. —A quantity of the scale, after having been freed from water and dirt by melting and subsidence, is allowed to cool over night to a temperature of 60" F. (15‘5 C.) The solid mass is then ground to a fine powder, a portion of which is used in the determination of the oil. 250 grains (16*2 grms.) of the scale, or 150 grains (9'6 grms.) in the case of the scale containing much oil, say over 7 per cent, are then wrapped in fine linen pressing cloths and a number of layers of filter paper, sufficient to absorb all the oil. The oil is then removed by pressure in a press, 1 which must have some arrangement for indi¬ cating the pressure applied. The cup in which the scale is placed during the application of pressure must have an area of 20 square inches; the maximum pressure is to be 10 cwts. per square inch, and the working pressure 9 cwts. per square inch. The scale is to remain under pressure for fifteen minutes; the temperature of the scale and of the press is to be 60° F. As the oil is determined on scale which has been freed from water and dirt, the result must be calculated to the original scale containing water and dirt. Determination of the Melting (Setting) Point of Solid Paraffin. —This is determined by what is known as the “ English test ” :—A test-tube, about 1 inch in diameter, is filled to the depth of about 2 inches with the melted paraffin, a small thermometer is inserted, and the whole steadily stirred, while the test-tube and its contents are allowed to cool slowly. The temperature at which the ther¬ mometer remains stationary for a short time is the melting (setting) point. It should be noted that paraffin wax does not exhibit the peculiarity of mixed fatty acids, viz. to remain stationary at the melting point and then to rise for a short time. With paraffin wax the mercury remains stationary at the melting point for about half a minute; but no rise takes place and the mercury then steadily falls. The, American method is as follows:—Compress 500 grains (32A grms.) of the untreated scale under a pressure of 9 tons over the whole surface of the circular press-cake, 2 five and five-eighth inches in diameter. This pressure is maintained for five minutes at the tem¬ perature of 60° F. The melting point is determined as follows :—A sufficient quantity of the scale is melted to fill three parts of a half- round dish, three and three-fourth inches in diameter. A ther¬ mometer with a round bulb is suspended in the melted mass so that 1 No one special form of press is recommended for general adoption. A description of several forms of press is given Jour. Soc. Chem. lnd. 1891, 346. Cp. also Cameron- Leask, Soap, Candles, etc., p. 324. 2 This is the same pressure as that employed in the “ Scotch test.” 762 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. the bulb is only three-fourths immersed. The melted paraffin is then allowed to cool slowly, and the temperature at which the first indica¬ tion of “ filming,” extending from the sides of the vessel to the ther¬ mometer, occurs, is taken as the melting point. 1 The German method for testing paraffin wax (obtained from lignite), known as the “ Hallenser Vorsclirift,” is the following :— A small beaker, 7 cm. high, and 4 cm. in diameter, is filled with water and warmed to about 70° C. A small piece of the sample of paraffin wax is then thrown on the water so as to form, after melting, a bubble of about 6 mm. diameter. A centigrade thermometer, 2 made according to the directions of the “Halle Association,” is then immersed in the water so that the bulb is entirely covered by water, and the mass allowed to cool slowly. The temperature at which a film is noticed on the paraffin is read off as the solidifying point. 3 It is evident that the method of determining the solidifying point according to the American and German methods must lead to very uncertain results. The best plan would be to adopt one of the methods described above (chap. iv. p. 130). L. Weinstein 3 has ascertained that the results obtained by the capillary tube method are very concordant indeed. CANDLE MATERIAL In the Scottish Paraffin Industry scale setting below 48° C. (118° F.) is classed as soft scale. As a rule, the setting point is stipulated for. In the Saxo-Thuringian industry the candle material has, as a rule, the melting point 53°-56° C.; material of lower melting point (50 -52 C.) or higher melting point (60 J C.) being but rarely em¬ ployed. 4 Paraffin wax must be mixed with a small proportion of stearic acid, from 2 to 15 per cent, to prevent the softening and bending of the candle. The stearic acid is determined by titrating an accurately weighed quantity with normal potash, using phenolphthalein as an indicator. Lach c.c. of normal potash corresponds to 0'284 grm. of stearic acid. The melting point of a mixture of paraffin and stearic acid lies, of course, below the calculated means of the melting points of the components, just like in the case of other mixtures. The following table, due to Scheithauerf gives the melting points of a number of mixtures of paraffin wax and stearic acid of known melting points :— 1 Garrigues {Jour. Soc. Chem. Ind. 1895, 281) proposes to take this point by melting 30 to 50 grms. of the sample in a beaker, inserting the thermometer so that the bulb is completely immersed, and twirling the beaker continuously in one direction until the mer¬ cury ceases to fall or rise. At first it falls rapidly and regularly, but then more steadily at the rate of O'l to 0’2 C. per minute after it has reached the highest point, at which it remains stationary for about half a minute. This highest point is taken as the melting point. 2 This thermometer is supplied by Ferd. Dehne, or J. H. Schmidt, Halle a/S. 3 Jour. Soc. Chem. Ind. 1887, 567. 4 Scheithauer, Die labrikation der Braunschweig, 1895. XII PARAFFIN WAX CANDLES 763 Paraffin Wax. Of Melting Stearic Acid of Melting Point Point. Melting Point 54° C. of Mixture. Per cent. °C. Per cent. ■c. 90-0 36-5 io-o 36-5 66-6 5 5 33-3 39-0 33-3 66-6 45-75 io-o 5 5 90-0 51-75 90-0 37-5 io-o 36-5 66*6 55 33-3 35-5 33-3 66-6 47-0 io-o 5 5 90-0 52-0 90-0 40-75 io-o 39-75 66-6 55 33-3 40-50 33-3 66-6 47-50 io-o 5 5 90-0 52-0 90-0 45-0 io-o 44-0 66-6 33-3 4075 33-3 66-6 48-0 io-o 55 90-0 52-5 90-0 48-5 io-o 47-5 66-6 - 33-3 45-0 33-3 66-6 4775 io-o 55 90-0 52-50 90'0 50-0 io-o 49-0 66-6 33-3 47-0 33-3 66-6 47-5 io-o 5 5 90-0 52-5 90-0 54-0 io-o 53-0 66-6 33-3 49-0 33-3 66-6 47-0 io-o ” 90-0 52-5 90-0 56-5 io-o 55-5 66-6 33-3 52-0 33-3 66 - 6 47-5 io-o ” 90-0 52-5 6. Cerasin Candles Raw Material. —The raw material used for the manufacture of cerasin is ozokerit, a natural bituminous product occurring in many parts of the globe in the vicinity of petroleum springs. The ozokerit 764 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. known best is found in Galicia. Formerly the ozokerit was distilled with a view to obtaining paraffin wax ; at present, at any rate on the Continent, it is exclusively worked up for the preparation of cerasin. The colour of ozokerit varies from a pure yellow to dark brown, depending on the admixed oxygenated resinous products. A rough test for specimens of great purity is that they can be kneaded between the fingers. The specific gravity varies from 0*91 to 0’97. The melting point is conditioned by the proportion of liquid hydrocarbons ; therefore it is difficult to fix the lower limit of the melting point. The upper limit of about 100° C. is reached by the so-called “ marble-wax.” The ordinary commercial cerasins melt at 60°-75° C. ; some very hard specimens (“ Sprungwachs ”) at 75°-80° C. 1 Pure ozokerit, i.e. the substance freed from water and mineral matter, varies much in its composition ; it consists chiefly of hydro¬ carbons, but contains also oxygenated and wax-like bodies; in case the liquating process has been faulty, asphalt-like substances are also present. Impurities naturally occurring in ozokerit are chiefly water, liquid hydrocarbons, and clay. The longer ozokerit has been kept at a temperature above 70 C., and the more carefully the liquation process has been conducted, the purer the cerasin will be. Fraudu¬ lently added impurities are : asphaltum (mineral pitch), and residues from paraffin oil distilleries. The examination of ozokerit consists in the determination of the loss on heating to 150° C. (which should not exceed 5 per cent), of its melting and solidifying points, and of the proportion of mineral matters. For the estimation of the latter small pieces are cut from the bottom of the blocks of ozokerit and treated with petroleum ether. Ozokerit can, therefore, only be properly valued by closely following the process of refining adopted on the large scale. Lack 2 proceeds as follows :—100 grms. of ozokerit are treated in a tared porcelain basin with 20 grms. of fuming sulphuric acid at a temperature of 170 -180 C. with constant stirring, until no more sulphur dioxide escapes. On re-weighing, the difference gives the volatile substances, viz. water and hydrocarbons. Into the melted substance 10 grms. of animal char, previously dried at 140° C., are stirred, and the mass is allowed to cool. A tenth part of the mixture is then weighed off and put in a weighed small cylindrical filter, closed at the bottom, and extracted in a Soxhlet apparatus with petroleum ether, boiling from 60 J to 80 C. The filter is dried at 130 C. and re-weighed; from the loss the percentage of wax is calcu¬ lated. By evaporating the petroleum ether solution and drying the residue at 180 C. this result may be verified; the melting point of the isolated cerasin may then be ascertained. The proportion of fuming sulphuric acid may be varied, according as the colour of the refined product is desired to be yellow or white. The refined product is termed Cerasin. 1 Berlinerblau, Das Erdwachs. Braunschweig, 1897. 2 Jour. Soc. Chem. Ind. 1885, 488. XII CERASIN—OLEINE 765 Cerasin (French, Cosine; German, Ceresin, Erdwachs) resembles in its physical characters beeswax; it is yellow or white, and odour¬ less. It melts between 61° and 78° C., sometimes also at a higher temperature; its specific gravity is O918-0-922. Commercial cerasin is frequently coloured with turmeric and other colouring matters. On shaking the melted sample with alcohol the colouring matters pass into the alcoholic solution. Cerasin is adulterated with “soft” paraffin and bleached colo¬ phony. An acid value of the sample may point to the presence of resin. In order to raise its melting point it is also mixed with carnauba wax (p. 651). Paraffin Wax is detected in cerasin by heating the sample with absolute alcohol, allowing to cool, and placing a few drops of the alcoholic solution on an object glass, when the residue will appear crystalline under the microscope. The following table, due to BerlinerUau, 1 may prove of use for practical purposes :— Cerasin. Per cent. Paraffin. Per cent. Melting Point. ° C. Solidifying Point. •c. Specific Gravity at 15° C. S3°-8D° C. 95° c. 100 0 70-73 69-5 0-921 0-7835 0-774 95 5 69-73 68-5 0-919 90 10 68-72 66-5 0-9175 0-7800 80 20 66-71-5 65-0 0-914 0-7775 70 30 64-5-70 63-0 0-910 0-7750 60 40 62-69 62-0 0-907 50 50 58-5-67 60-0 0-904 0-7705 40 60 56-5-65 59-0 0-900 30 70 54-5-62 57-0 0-897 20 80 52-5-58-5 54-0 0-894 10 90 49-5-54-5 49-0 0-892 0 100 47-52 47-0 0-889 0-7655 0-756 Other adulterants are detected by proceeding according to the pro¬ cesses given for the examination of beeswax (p. 664). For a thorough examination of the unsaponifiable matter the methods described in chap. vii. (p. 229) must be used. K. COMMERCIAL OLEIC ACID. OLEINE, ELAINE Commercial oleic acid (p. 745) is in its purest state transparent, and of a yellow or light brown colour; if turbid it has a dark brown colour. The former quality is termed “pale oleine” (French, 1 Loc. cit. 766 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. OUine blonde; German, Blondes Main); the latter “ red oil.” Com¬ mercial oleic acid contains notable quantities of solid fatty acids, viz. palmitic and stearic; if the oleic acid has been obtained by acid saponification (p. 746) there may be present, besides these acids, isooleic acid, and also hydrocarbons to the extent of 3 to 7 per cent. These hydrocarbons are produced by partial decomposition of the crude fatty acids during distillation; it is, therefore, possible to infer from their presence and their amount the mode of manufacture and the care exercised in distilling. But the converse, that a com¬ mercial oleic acid, if free from hydrocarbons, is a “ saponified oleine,” does not hold good, there being in commerce carefully prepared “ distilled oleines ” that are practically free from unsaponifiable matter. Commercial oleic acid contains varying proportions of unsaponified (neutral) fat, solid fatty acids, and hydrocarbons. The neutral fat is determined as described for commercial stearic acid ; the hydrocarbons are estimated by the methods given in chap, vii., and the solid fatty acids as described p. 192. The following table contains a few analyses of typical “ oleines,” as obtained in the saponification of neutral fats:— [Table COMMERCIAL OLEIC ACID ta o' s § ; \o 10 1 cn w . P P : cn i>- . P P : cn oo : co i co > cp (N . . Oi Oi CO o: o !hn : : Eu ¥ gcoco(Mcocoj^o3iO^ gO O co 10 05 10 05 O CO 05 d a a £ £ > d d £ £ p Jo c3 c3 ^ o3 c3 Ph fiQP PhPh o o^ oo T3 j3 p Ph o d ~Jp r a PP d3 2 >5 a s s d a • ~ 2 o d o ; •'a ph^ 1 pd _. =$ _, ^ 'o o fld d c3 d 1 ^ o ~ d cc ^ c3 d 768 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. Other oleines obtained from waste products of the fat industries, and containing large proportions of unsaponifiable matter, have been described under the headings: “Wool Fat” (p. 691), “Cotton Seed Foots” (p. 692), and “Wool Oils” (p. 704). If the oleine be intended for the manufacture of soap the unsaponifiable matter only need be determined, a certain proportion of solid fatty acids or of neutral fat being rather desirable than otherwise. For rapid valuation of oleine intended for soap-making it is therefore sufficient to saponify with alcoholic potash, and divide the saponification value found into 200 x 100, 1 when the percentage of saponifiable fat is obtained in sufficient approximation. If it be required to ascertain whether a sample of oleine has been obtained from tallow only, or from a mixture of tallow with a vegetable fat, the methods described chap. ix. p. 317, may be employed. High-class oleines for the wool industry have been stated to occasionally contain linseed oil acids, due according to Granval and Valser , 2 to admixture of linseed oil with tallow stearine in order to induce the press-cakes to part more readily with the liquid fatty acids. A somewhat considerable proportion of linseed oil fatty acids is detected by a high iodine value of the sample. Hazura 3 proceeds as follows :—50 grms. of the sample are saponi¬ fied on the water-bath Avith dilute alcoholic potash. The alcohol is driven off by boiling down, and the residuary soap is dissolved in 1000 c.c. of water. Into this strong alkaline solution 1000 c.c. of a 5 per cent solution of potassium permanganate are gradually run in Avith constant shaking. After ^ to 1 hour the hydrated manganese peroxide is filtered off, the filtrate acidified with sulphuric acid, and again filtered. The filtrate thus obtained is neutralised with caustic potash, concentrated to about 300 c.c., and again acidified with sulphuric acid, whereby a precipitate is obtained. The acid liquid and the precipitate are then shaken out Avith ether. If the precipitate dissolves in ether, it consisted of pure azelaic acid, C 9 H 1(i 0 4 , and the sample of oleine is free from linseed oil acids; but if the precipitate does not dissolve in ether, this may be owing to the presence of these acids. The precipitate is filtered, recrystal¬ lised several times from Avater or alcohol, and decolourised by animal charcoal; after drying in a desiccator its melting point is determined. If the latter be above 160° 0., linseed oil acids are undoubtedly present. If a somewhat large quantity of this oxidation product be avail¬ able, its acid value may be also determined ; this should not exceed 150, the acid value of hexahydroxystearic acid being 147'3. Amagat and Jean 4 detect the presence of linseed oil fatty acids in oleine with the aid of the oleo-refractometer. The following are their results :— 1 Taking 200 as the saponification value of oleic acid. 2 Jour. Pliarm. Chem. 1889, 232 ; Jour. Soc. Chem. Ind. 1889, 425. 3 Jour. Soc. Chem. Ind. 1889, 641. 4 Monit. Scient. 1890, 346. XII OLEINE—SOAPS 769 Degrees. Oleine from tallow or from mixed tallow and palm oil Oleine with 10 per cent of mixed linseed oil fatty acids >> )> 20 ,, ,, ,, ,, » » 35 „ » » 40 „ Mixed fatty acids from linseed oil . The detection of “ distilled grease oleine ” in commercial oleic acid may be also effected by means of the oleo-refractometer :— -29 -24 -23 -ll Oleic acid from tallow or from mixed tallow and palm oil ,, ,, with 10 per cent of distilled grease oleine >> >> j> 20 . >> >> >> 80 j >> >> >j 40 , >j >> >) 50 , Distilled grease oleine >> )> >) >> >> >> >> >> >> >> >) >> Degrees. . -34 . -28 . -23 . -17 . -11 . - 5 . +25 Presence of “ distilled grease oleine ” is, however, detected with greater certainty by means of the cholesterol or isocholesterol reaction (p. 84). The metallic salts of oleic acid will be mentioned under the heading “ Insoluble Soaps.” L. SOAPS It has been pointed out already (p. 33) that the metallic salts of higher fatty acids are termed soaps; hence we speak of potash soap, lime soap, lead soap, etc. In particular, the term “soap” is applied to the salts of the alkali metals, and as the resinates of these metals have also the property of lathering and acting as good detergents, they are included under this generic term. I.—Soaps of the Alkali Metals. Soaps The commercial soaps are either hard or soft soaps, according as. the base combined with the fatty acids is soda or potash. Soaps are manufactured by boiling glycerides with caustic alkalis. In the event of the raw material being fatty acids (oleic acid, p. 768) or resin, soap-making consists, chemically speaking, in neutralising an acid by a base. If potash be used as base, the resulting potash soap retains all the glycerol contained originally in the glycerides, and, on account of the chemical properties of the potash salts of the fatty acids, also 3 D 770 TECHNICAL AND COMMERCIAL ANALYSIS CHA1‘. a large amount of water. Potash soaps made with the greatest care will be devoid of free alkali; as a rule, however, the commercial potash soaps contain an excess of alkali. Besides, the commercial soaps will naturally retain any impurities occurring in the fats and in the alkali used—notably sulphates, carbonates, chlorides, etc. 100 parts of neutral glycerides yield, when saponified on the large scale, 240 parts of commercial potash soap. Soda soaps are made by saponifying glycerides with caustic soda. The older process of preparing the potash soap first, and sub- sequentlv converting it by means of common salt into soda soap, is at present only practised where cheap supplies of wood ashes admit of the economical working of this method. In practice we discern chiefly two processes for making hard soap—(1) by the “ cold process, and (2) by boiling. In the former process cocoa and palm nut oils are chiefly used, having the property of being easily saponified by strong caustic lyes in the cold (p. 538). The resulting hard soap, like potash soap, con¬ tains the entire mass of fat and alkali brought together ; consequently all the glycerol formed during saponification is found in the soap. In the second process the fats are boiled with the caustic soda lye, the resulting soap paste is “cut” by addition of salt, and by suitable treatment is brought into the form of the familiar cake or bar. The glycerol is in this case separated; and as an excess of free alkali can be easily avoided, the final product should be the pure sodium salt of fatty acids (with only small quantities of mineral salts) combined with so much water as is necessary to form commercial soap. This soap is termed “ curd soap” “genuine soap .” 100 parts of neutral glycerides yield about 150 parts of finished soda soap. The data given for the yields of soaps enable us to calculate the theoretical composition of pure commercial soaps. Suppose a fat has been saponified, the saponification value of which is 195, or, in other words, which requires 19‘5 per cent of KOH = 16-42 per cent of K 2 0 for saponification. The 240 parts of potash soap obtained from 100 parts of this fat contain, of course, 16-42 parts of K 2 0; therefore we have in the soap 6"843 per cent of K 2 0 [240 : 16'42 : : 100 : x\ Let the mean molecular weight of the fatty acids be 275 ; hence the corresponding amount of the fatty anhydride 275 — 9 = 266. As 47-1 parts of K 9 0 combine with 266 parts of fatty anhydride, we have in the soap 38‘7 per cent of fatty anhydride [47'1 : 266 : : 6'843 : x\ The remainder consists of glycerol and water. The composition of a pure potash soap should therefore be— Fatty anhydride K 2 0 . Glycerol and water . Per cent. 38700 6-843 54-457 100-000 XII SOAPS OF THE ALKALI METALS 771 As in the course of analysis (see below) the fatty acids are isolated in their hydrated state, we should find on analysing a pure commercial potash soap 40 per cent of fatty acids [266 : 275 : : 38-7 : x]. Similarly, the composition of a pure commercial soda soap may be calculated. 100 parts of the same fat require 10-81 parts of Na„0 [47T : 31 : : K 2 0 Na 2 0 16'42 : x]; consequently the finished soap contains 7*21 per cent of Na 2 0 [150 : 10‘81 : : 100 : x\, with which are combined 61*8 per cent of fatty anhydrides [31 : 266 : : 7*21 \x\ corresponding to 63*9 per cent of fatty acids [266 : 275 : : 6T8 : x]. The percentage composition of a pure “ curd soap ” is therefore— Per cent. Fatty anhydride 61-80 Na 2 0 .... 7-21 Water .... 30-99 100-00 If the mean molecular weight of the fatty acids be different from 275, as in the case of, say, rape or castor oil, the result will be some¬ what different. In the case of cocoa nut oil soap, made by the cold process, the soap would have the following composition, for the saponification value of a cocoa nut oil 240, and the mean molecular weight of the fatty acids 200 :— Per cent. Fatty anhydride 54-50 Na 2 0 .... 8-86 Glycerol and water 36-64 100-00 Pure commercial soda soaps made by the processes mentioned contain the proportion of water given above—which might be called their water of constitution, inasmuch as a soap cannot be made with less water—when freshly prepared. On exposure to the air, how¬ ever, they lose water, and naturally the proportion of fatty acids will be found higher. In the manufacture of good toilet soaps— milled soaps —the dry¬ ing is carried out intentionally, and the soaps thus produced may contain as little or even less than 10 per cent of water, with a corresponding increase in the proportions of fatty anhydride and soda, which of course remain in the same ratio. More frequently, as in low class household soaps, the proportion of water is increased with the aid of caustic alkalis or carbonates, etc. Cocoa nut oil soaps (marine soaps) in particular are able to combine with such enormous quantities of water that those soaps may contain as little as 16 to 20 per cent of true soap. Although the nature of the fatty material plays a very important part indeed in the manufacture of soap, different fats of varying 772 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. degrees of purity being employed for soaps intended for special purposes (toilet soaps, household soaps, textile soaps, etc.), it does not frequently come within the scope of a commercial analysis to give an exhaustive report as to the nature of the fatty raw material. In commercial analysis it is usually sufficient to estimate the total fatty matter, or, in short, fatty matter, perhaps with a further discrimination into fatty acids, neutral fat, and unsaponifiable matter. As a rule, the fatty matter is returned as fatty acids, if no further examination be instituted, and in the case of pure soaps, such as good household soaps, this will meet all that is required for a rapid valuation of the soap. Any resin acids present in the fatty matter are in that event looked upon as so much fatty acids, and conse¬ quently included in the fatty acids, unless a separate determination of the resin acids be desired. The more fatty acids a sample contains the more actual soap is present. A comparison of the result of the analysis with the theoretical composition of soaps given above will render the valuation an easy matter. Any hard soap containing more than 64 per cent of fatty acids has either dried spontaneously on keeping, or has been dried artificially, as in the case of milled toilet soaps. Hard soaps containing less than that amount have been reduced inten¬ tionally, and may contain an excess of water or alkali, or any of that well-nigh endless number of adulterants that are incorporated with soap. Almost equally important is the estimation of the quantity of the base, especially with a view to determining whether any alkali is present other than is requisite to combine with the fatty acids. Any excess of alkali beyond that quantity is objectionable in toilet and household soaps. In special cases, however, an excess of alkali is demanded, as in scouring soaps (see Textile Soaps, p. 784). In the case of PURE (“ genuine ”) SOAPS the estimation of fatty matter and alkali in its various forms will suffice for all practical purposes, and the water in the soap may be found by difference. In the present condition of the soap trade, and in view of the demands made by the public taste, it is difficult to say what con¬ stitutes adulteration. Resin is a legitimate substitute of fatty matter, the resinates of sodium possessing valuable detergent properties. Sodium silicate and borate also possess detergent properties, but these substances must be considered as standing on the border-line between legitimate constituents and adulterants. Colouring’ matters in soaps cannot be considered as illegitimate, as coloured soaps are demanded in commerce. If the colouring matter be harmless no objection can therefore be raised, and the analyst will, at most, only be desired to state whether certain colouring matters contain poisonous metals or not. Ethereal oils in soaps have almost become a necessity, even as regards better class household soaps. Their quantity will naturally XII SOAPS 773 be very small, and need not, as a rule, occupy the attention of the analyst. Medicated soaps contain ingredients which, if sold under their proper names, cannot be objected to, soap being made in those cases the most convenient vehicle for the application of medicaments to the skin. Carbolic soap falls under this head, as also those “ super¬ fatted ” soaps which contain iodine, iodoform, etc. Where the line has to be drawn between a true and a spurious medicated soap must be left to special examination that falls outside the scope of this work. It may, however, be added, that a great many soaps stated to contain valuable medicaments are entirely devoid of them. In transparent SOAPS a small quantity of alcohol may be present, left in consequence of incomplete evaporation of the alcohol used in the process. If the transparency is due to presence of sugar, this substance must be considered an adulterant. The number of substances that are acknowledgedly incorporated with soaps in order to impart to them some valuable properties, real or supposed, is almost legion. It must be left to the analyst to decide in each individual case whether petroleum, paraffin wax, tar oils, sulphur, etc., are to be classed amongst adulterants or not. There can, however, be no doubt as to adulteration in the case of “ fillers ” or “ weighting substances ” having been found in soaps, these substances being added solely for the purposes of substituting a worthless material for soap. Starch, clay, talcum, chalk, barytes, fall under this category. If sand in a soap be stated or sold as such, it can, of course, not be considered a fraudulently added material. In the following lines I describe the best methods (leaving out a number of more or less valueless processes and methods) used for the detection and estimation of the several constituents of soaps and various foreign substances, in the order of their importance as regards the purposes of commercial analysis. No attempt is made to indicate a scheme of procedure that would include the examination for all substances that may possibly be present, as such a course would be of little practical use. Sampling of the Soap Great care must be exercised in sampling if gross errors are to be avoided. As pointed out already, soap exposed to the air dries on the surface, the outer portions of a cake protecting the inner portions to some extent. The sample of hard soap should therefore be taken from the centre of the cake by cutting away all the outer portions ; to what extent this must be done will be seen in most cases by 774 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. inspecting the sample, a transverse section showing to what depth drying to any serious extent has taken place. Such devices as taking a sample by means of a cork borer, or by cutting a transverse slice out of the cake in order to obtain an “ average ” sample, lead to erroneous results. If the soap under examination be freshly made (with 30 per cent of water) the sample should be fairly large and weighed off rapidly, as it is apt to give up perceptible quantities of moisture to the dry atmosphere of the balance case, if the weighing is done slowly. For the same reason the sample should not be sliced before weighing, except perhaps in cases of a milled toilet soap or of a very dry soap. The well-known contrivances for preventing loss of moisture during weighing are therefore best resorted to. Similar precautions must be taken in the case of soft soap. If a barrel of potash soap has to be sampled, the soap must be taken from the centre. Quantitative Analysis of Soap (a) Determination of Fatty Matter A rapid, and for the purposes of commercial analysis sufficiently accurate process is the following:— Weigh off accurately 5 to 10 grms. of the sample (or a larger quantity, say 30 to 50 grms., on a balance sensitive to centigrammes), and dissolve in hot water in a beaker or porcelain basin by heating gently; stir continually with a glass rod so as to prevent the soap from caking on to the bottom of the vessel. When the solution is gently boiling add a few drops of methylorange, and run in gradually hydrochloric, or dilute sulphuric (or nitric acid if chlorides and sul¬ phates are to be determined), until there is an excess of mineral acid. Heat with constant stirring until the separated fatty acids have melted into oily drops, add about 5 grms. of dry beeswax (or stearic acid) weighed accurately on a tared watch-glass (to be used again afterwards), and heat again until the mixture of fatty acid and wax has collected on the top of the liquid as a clear, transparent oily layer free from any white specks. Rinse off the glass rod, boil until the fatty matter has again collected into one mass, remove the vessel from the source of heat, and allow to solidify by cooling. A white precipitate on the bottom of the beaker will indicate the presence of silicate or “ fillings ” insoluble in mineral acids. The solidified cake is then detached from the vessel by means of a platinum spatula, lifted out of the liquid, rinsed off with cold water, and placed on filter paper. Any small quantity of fatty substance adhering to the sides of the vessel is carefully scraped off and added to the cake. Dry the cake carefully with filter paper, place it on the watch-glass used before with its bottom side upwards, allow to dry in a desiccator, and weigh (or—with less accuracy—weigh XII SOAPS 775 immediately after drying with filter paper, taking care that no moisture remains in any cavities of the cake). If the cake should contain any cavities (which occurs only when the fatty matter has not been boiled sufficiently), enclosing water and perhaps also, acid, the cake may be remelted in a basin over water, lifted off and dried again, and heated in a tared porcelain dish over a very small flame until the crackling noise has ceased, which indicates that all moisture has been driven off*. From the weight thus found the weight of the beeswax is deducted, and the difference returned as fatty matter. As a rule, it is returned as fatty acids if no closer examination is made. This would, however, be only correct if the absence of neutral fat, wax, and unsaponifidble matter has been proved, resin acids being looked upon as so much fatty acids, unless determined separately. The addition of beeswax may, of course, be omitted if the fatty matter will set to a solid cake on cooling. Unless this be ascertained by a preliminary experiment it will be best to add beeswax at the outset. The determination of the total alkali in the soap can be con¬ veniently combined with this process if an accurately measured volume of standard acid is used for the decomposition of the soap. The acid liquid is then filtered to separate traces of fatty acids adhering to the vessel, and the excess of acid titrated back by standard alkali (see below). If the process given here should not be considered accurate enough, the fatty matter may be collected on a filter, as in Hehner s process, and further treated as has been described page 160. If the aqueous liquid contains any suspended matter, or if a precipi¬ tate has been formed, it is best to use a separating funnel, drawing off the liquid from the fatty layer, and then throwing the latter on a filter. If any foreign matter, say fibres, be noticed in the fatty matter, it is best to dissolve it in alcohol, or petroleum ether, etc., and to filter. Any soluble fatty acids present will have passed partly into the acid liquid; as a rule, they may be altogether neglected, except perhaps in the case of soaps from cocoa nut and palm nut oils. In that event it is best to work with concentrated solutions, or, if con¬ venient, to add brine or common salt, which will throw out the bulk of the soluble acids, so that the remainder may be disregarded. If the greatest accuracy be required the acid liquor is titrated with standard alkali until it is neutral to methylorange. Phenolphthalein is then added, and decinormal or half-normal alkali run in until pink. The quantity of alkali used in the second titration is calculated to, say, caprylic acid, C 8 H 16 0 2 , molec. weight 144, and its amount added to the chief quantity found before. A large number of processes have been recommended by various observers purporting to introduce greater accuracy, but in my opinion these unnecessarily complicate the analysis without anything being gained. Thus it has been proposed to decompose the soap in a 776 TECHNICAL AND COMMERCIAL ANALYSIS CHAl’. separating funnel, shake out with ether, and evaporate the ethereal solution containing the fatty matter, etc. If by subsequent examination the soap has been found free from neutral fat, wax, and unsaponifiable matter (cp. 780), as is mostly the case, the fatty matter is returned as fatty acids. If a complete analysis of the soap is desired they must be calculated to fatty anhy¬ drides. Since 100 parts of stearic acid, C 18 H 36 0 2 , correspond to 96'83 parts of stearic anhydride, (C 18 H 35 0) 2 0, and similarly 100 parts of palmitic acid, C 16 H 32 0 2 , to 96'48 parts of palmitic anhydride, (C 16 H 31 0) 2 0, and 100 parts of oleic acid, C ls H 34 0 2 , to 9 6‘81 parts of oleic anhydride, (C 18 H 33 0) 2 0, no appreciable error is committed if 3’25 per cent are deducted, or, what amounts to the same, the percentage of fatty acids be multiplied by 0-9675, and the result returned as fatty anhydride. ( b) Total Alkali Total alkali is the sum of the several amounts of alkali present in the soap as (1) alkali combined with fatty (and resin) acids, (2) free caustic alkali, (3) alkali in the form of carbonate, silicate, or borate. The total alkali is found by titration with standard acid, and is conveniently combined with the determination of the fatty matter, the indicator used being methylorange (see above (a)). The alkali is calculated in the case of soft soaps as caustic potash, K 2 0, and in the case of hard soaps as caustic soda, Na 2 0. There may be present in hard soaps small quantities of potash, but this is, as a rule, disregarded. More frequently soft soaps contain notable proportions of soda. If a separate determination of soda and potash be required, a weighed quantity of soap is decomposed with hydro¬ chloric acid, the acid liquor separated from the fatty acids by filtra¬ tion, and the potash estimated as potassium platinic chloride in the usual way. From the amount of potash, and from the quantity of acid required to saturate the total alkali, the caustic soda is easily calculated. Of course, any other method used in mineral analysis may be employed. (c) Free Caustic Alkali and Alkaline Salts A preliminary test is made by dropping an alcoholic solution of phenolphthalein on a freshly cut surface of the soap. Pink coloura¬ tion indicates presence of free caustic soda, and, if the soap is not too dry, also of carbonate, silicate, and borate. If the soap is very dry the last-mentioned salts cannot be thus detected. If a colouration has been obtained, any free caustic alkali is separated from the alka¬ line salts by dissolving a portion of the sample in absolute alcohol, and filtering. The alkaline salts remain on the filter, and the alcoholic filtrate may now be tested with phenolphthalein. Free caustic alkali should be absent from well-made soaps, especi¬ ally from toilet soaps. The “ fitting ” of a soap without an excess XII SOAPS 777 of free alkali requiring a great deal of circumspection, most of the ordinary commercial soaps contain an excess of alkali. If this be small the free caustic soda will be converted on exposure to the atmo¬ sphere into carbonate, so that no free alkali will be found in many cases, especially if the outer portions of a cake be tested. If, however, the excess of free caustic soda in the soap be large, as notably in scouring soaps and cheap toilet soaps made by the cold process, the detection of free alkali will offer no difficulty. It should be borne in mind that under the term free alkali frequently all that alkali is understood which is not combined with fatty acids to form true soap, so that carbonate, silicate, and borate is included in “free alkali.” We understand here under free alkali free caustic alkali, thus distinguishing it from the alkaline salts. Free caustic alkali is determined quantitatively, according to Hope j 1 by dissolving 30 grms. of the sample in hot alcohol, as free as possible from water. For very moist soaps absolute alcohol should be used. Highly watered soaps are best dehydrated first to some extent. The hot solution is filtered rapidly, lest any soap-jelly should separate on the filter ; if the operation is carried out judiciously, a hot water funnel may be dispensed with. 2 The filter is well washed, and the filtrate received in a narrow-mouthed flask so as to prevent as much as possible contact with air. Phenolphthalein is then added to the solution, and decinormal hydrochloric acid dropped in until the colour is discharged. If no preliminary test has been made it may happen that the alcoholic solution exhibits an acid reaction to phenol¬ phthalein at this stage. This acidity is due to the soap containing, in consequence of faulty “ fitting,” an acid stearate (palmitate or oleate, cp. p. 34), or to free fatty acid having been added to “kill” an excess of alkali. In either case the analytical report will state that the soap contains free fatty acids. The precipitate left on the filter contains carbonate, silicate, and borate, possibly mixed with sodium chloride and sulphate, 3 and other insoluble substances, added as “fillers,” such as starch, sand, clay, etc., or colouring matters, etc. For the complete examination of this precipitate see below. For the determination of the alkaline salts only the precipitate on the filter is washed with cold (see (/) 1) water, and the alkalinity of the filtrate determined by titration with standardised acid, using methylorange as indicator. The acid required is calculated to Na 2 0. We have thus determined— (1) Total alkali. (2) Free caustic alkali. (3) Alkali present as carbonate, silicate, borate. 1 Chem. News, 43 (1881), 219. 2 Spaeth recommends to use Soxhlet’s extractor (cp. Jour. Soc. Chem. Ind. 1896, 139), but in the writer’s opinion his process only complicates matters. 3 Horn, Jour. Soc. Chem. Ind. 1887, 681, recommends in the case of highly watered soaps to remove the greatest part of the water by preliminary drying of the sample, as otherwise carbonate (and also chloride and sulphate) passes into the filtrate. l7b TECHNICAL AND COMMERCIAL ANALYSIS chap. The alkali combined with fatty (and resin ) acids may now be found by difference, i.e. by subtracting the sum of the amounts of alkali obtained for (2) and (3) from the total alkali (1). It can, however, be found direct by titrating the alcoholic solution of the soap, after neutrality has been established to phenolphthalein, with normal acid, using methylorange as indicator. This may be done to check the results of the analysis, or in order to dispense with the determination of the alkali present as carbonate, silicate, and borate, which obviously can then be found by difference. (d) Determination of Water Highly watered soaps must not be dried at once at 100° C., as they melt at this temperature, and become coated with a dry skin which prevents the escape of water from the inner portions. For this reason and those mentioned under “ Sampling,” the method of reducing, the soap to shavings, and drying on a watch-glass at first from 60 -70 C., and then to 100 C., should be abandoned in favour of one of the following processes :— (1) Tare accurately a beaker of 100 c.c. capacity, the bottom of which is covered with recently ignited sand about half an inch high, together with a small glass rod, then weigh off in a beaker about o grms. of the sample, add 25 c.c. of alcohol, dissolve the soap on the water-bath with occasional stirring, evaporate the alcohol, and finally dry in an oven at 110 J C. until the weight remains constant [Gladding)} (2) A rapid, and for technical purposes sufficiently accurate process is that proposed by Watson Smith . 2 Heat 5-10 grms. of the sample in a large porcelain crucible on the sand-bath, stirring con¬ stantly with a glass rod (weighed with the crucible), having a roughed and jagged end, whereby the lumps formed towards the end of the operation are conveniently broken up. The drying is usually com¬ plete after twenty to thirty minutes; all the water is expelled, when a cold watch-glass held over the crucible, after removal of the flame, is no longer bedewed with moisture. The crucible should be heated by a small flame, and care must be taken not to burn the soap \ this would be recognised by the characteristic smell. T he loss found is calculated as water, but it should be remembered that ethereal oils present in toilet soaps (and also in household soaps) volatilise with the water \ so also would alcohol (present in small quantities in some kinds of transparent soaps), and appreciable amounts of glycerol if present in notable quantities, as in some toilet soaps. Besides, if the soap contains considerable proportions of free caustic soda, part of the loss will be compensated by the absorption of carbonic dioxide. As the sample of soap when it reaches the analyst’s laboratory, as Cliem. Zeit. 7. 568. 2 Jour. Soc. Dyers and Colourists, i. 31. XII SOAPS 779 a rule, has lost more or less water by drying, I am of the opinion that, excepting milled toilet soaps and potash soaps and special cases, the direct determination of water in soaps is of little use, and that it is preferable to find the water by difference. For ordinary purposes of valuation of a sample of soap the determinations described under (a) to ( d) will suffice. Further tests will embrace the examination of the fatty matter, and detection and determination of other constituents of the soap, legitimate and fraudulent. (e) Examination of the Fatty Matter (“ Soap Stock”) If no wax has been employed in the separation of the fatty matter, the latter may be used direct for the following tests. Other¬ wise a fresh quantity of fatty matter must be prepared, for which purpose most conveniently the cuttings are used up. The fatty matter may contain, besides fatty acids, (1) resin acids, (2) neutral fat, (3) unsaponifiable matter. (1) Resin Acids. —Resin acids are detected qualitatively by the Liebermann-Storch reaction (p. 226). For their quantitative estimation TwitchelVs method should be used (p. 244). (2) Neutral Fat. —A well-made soap will but rarely contain any unsaponified fat. Sometimes, however, neutral fatty substances are added purposely to the finished soap, as in the case of the “ super¬ fatted ” soaps for medicinal purposes (admixture with olive oil), or in the case of certain toilet soaps (wool wax). The neutral fat is ob¬ tained together with any unsaponifiable matter present, and must be separated from it subsequently. The neutral fat plus unsaponifiable may be isolated direct from the sample of soap by dissolving a weighed quantity in water or alcohol, adding caustic potash to neutralise any free fatty acids present, using phenolphthalein as indicator, and exhausting the soap solution as directed chapter vii. p. 218; or the dried soap may be exhausted with solvents. About 10 grms. of the sample are weighed off, dissolved in a beaker in alcohol, and mixed with five to seven times its weight of sand, previously washed with acid and ignited. The alcohol is then evaporated off, and the dried mass transferred to a Soxhlet extractor and exhausted. The extract contains, besides neutral fat and unsaponifiable matter, also free fatty acids, if present. Their quantity may be determined at this stage (see above) by titration with alkali, using phenolphthalein as indicator. If the soap contains at the same time neutral fat and free caustic soda, which may occur to a notable extent in a badly made cocoa nut oil soap by the “ cold process,” obviously saponifica¬ tion will take place in the alcoholic solution, and the method becomes valueless. Considering that the weighing off of a fresh sample may, in view of the difficulty of obtaining several samples of exactly the same amount of moisture, cause considerable errors, I prefer, although 780 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. it entails a little more calculation and one more operation, to deter¬ mine the neutral fat in the isolated fatty matter. To this effect the fatty matter is dissolved in alcohol, neutralised exactly, using phenolphthalein as indicator, and the solution then shaken out with ether. The residue from the ethereal solution consists of neutral fat plus unsaponifiable. Their separation is effected by saponification and extraction of the saponified substance (p. 218). If unsaponifiable matter be absent the total ether residue consists of neutral fat, otherwise the neutral fat is found by difference after saponification and estimation of the unsaponifiable matter. A complication arises if the soap contains wool wax also. If wool wax be suspected, and confirmation has been obtained by a qualitative test for cholesterol or isocholesterol, it will be best to boil the ether residue with dilute alcoholic potash on the water-bath so as to obtain part of the wool wax as unsaponifiable matter. (3) Unsaponifiable Matter. — This is isolated and estimated together with neutral fat. If no neutral fat has been found the total ether residue consists of unsaponifiable matter. In the case of certain toilet soaps this may be wool wax ; it will be identified by its physical characters, and chiefly by its qualitative reactions (cholesterol or isocholesterol reactions). Other unsaponifiable substances present may be paraffin wax, vaseline, paraffin oil, oil of turpentine, tar oils, naphthalene, hydro¬ carbons from “distilled grease” (p. 690) and from other sources, all of which substances have been and are being mixed with soaps. Methods for their identification have been described in chapter viii. Waxes will hardly be added to soaps, on account of the difference of price. Carnaiiba wax, stated in some text-books as being usually admixed with soaps in order to render incorporation of large propor¬ tions of paraffin oil possible, is not used, as the same object may be attained by cheaper methods. The examination of the FATTY acids themselves, after separation from resin acids, neutral fat, and unsaponifiable matter, with a view to determining the nature of the “ stock ” the soap has been made from, is a complicated problem, which will hardly come within the scope of a commercial analysis. Still, if such a research be required, the methods detailed in chapters ix. and x. must be applied system¬ atically, and they will, as a rule, lead, if not to strictly accurate, at any rate to approximately accurate results. (/) Substances insoluble in Alcohol The estimation of the total amount of substances insoluble in alcohol is conveniently combined with the determination of the free caustic alkali described under (c), the insoluble being collected on a tared filter previously dried at 100° C. The filter, together with the precipitate, is then dried again at 100° C., and weighed. XII SOAPS 781 Good soaps will yield but insignificant traces of residue. Only those soaps which have been rendered transparent by the “ alcohol process” will be absolutely free from insoluble matter. The residue obtained on the filter may consist of— 1. Water-soluble salts, such as chloride, sulphate, carbonate, silicate, and borate of the alkalis. 2. Mineral substances insoluble in water, viz. colouring matters and “ filling ” and “ weighting ” substances, such as clay, chalk, sand, etc. 3. Organic substances, especially starch, dextrin, gelatin (car¬ rageen mucilage). 1. Water-soluble Substances. —The estimation of alkali present in the form of carbonate, silicate, and borate, has been already described under (c). Cold water is used so as not to dissolve any gelatin, if present. If silicate is present this will have been noticed when de¬ composing the soap by acid (see above under (a)). The silicate may be estimated simultaneously with the fatty matter, if no other water-insoluble substance is present, or it can be determined at this stage by acidifying the neutralised (titrated) filtrate with hydrochloric acid and evaporating to dryness in the usual way. The filtrate from the separated silica may be tested for boric acid. If boric acid is absent, it is easy to calculate from the alkali and the silica found the amounts of carbonate and silicate. If boric acid be present and the proportion of borate be also required, the water- soluble portion is best divided into three parts. In one portion the carbon dioxide is determined, in a second the silica, and the third is titrated for alkali and tested qualitatively for boric acid. 1 Chlorides and sulphates are best determined in aliquot portions of the acid liquor, obtained as in (a) after separation of the fatty matter in the usual manner. It should be remembered that in that case, of course, nitric acid must be used to decompose the soap. 2. The water-insoluble portion is ignited, so as to get rid of any organic substances, and the residue weighed. The ash may be examined qualitatively and quantitatively in the usual manner. 3. Organic Substances. —The microscopical examination of the total residue insoluble in alcohol may furnish' useful hints. Starch will be detected in this manner; a corroborative test may then be made with iodine. It is determined quantitatively by conversion into glucose. The residue, insoluble in alcohol, is washed with cold water to remove the water-soluble substances and dextrin, and boiled with dilute sulphuric acid, replacing the water as it boils away. The liquid is then neutralised with barium carbonate, filtered, and the glucose estimated by titration with Fehling’s solution in the usual way. Dextrin will have been washed out simultaneously with the soluble salts by cold water. The proportion of dextrin is estimated by precipitating it from the aqueous solution by means of alcohol. This is done best in a beaker, tared with a glass rod, so that the 1 Waltke and Co.’s method, see Jour. Soc. Chem. Ind. 1896. 782 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. liquid may be agitated vigorously, when all the dextrin will adhere to the sides of the vessel. The aqueous liquid is then poured off, the dextrin washed with alcohol, and determined by re-weighing the beaker after drying at 100° C. Gelatin will be dissolved by washing the alcohol-insoluble residue with hot water. The filtrate is tested for it with tannic acid. (g) Other Substances occurring in Soaps 1. Glycerol. —The minute quantity of glycerol left in hard soaps, made by the boiling process, can only be determined with accuracy if a large quantity of soap be employed. It is contained in the aqueous liquid from the separated fatty matter, and may be deter¬ mined as described under estimation of glycerol in spent soap-lyes (p. 809), but as a rule its determination is not required. In special cases, however, it may indicate by its amount that a hard soap has been made by the cold process, when about 5 per cent of glycerol and more will be found; its absence in soft soaps will prove that oleic acid has been used as “ stock.” Considerable quantities of glycerol occur in certain toilet soaps, being intermixed with them in special machines; on account of its cosmetic properties, the glycerol must be considered a valuable ingredient of such soaps. In the last-mentioned cases the glycerol is determined by dis¬ solving the soap in water, separating the fatty matter by an acid, and filtering off. The filtrate is neutralised with barium carbonate, and boiled down to the consistency of a syrup. The residue is then extracted with a mixture of three parts of 95 per cent alcohol and of one part of ether, the alcoholic solution filtered and evaporated on the water-bath to a small bulk, and finally dried under a desiccator. The glycerol in the crude glycerin thus obtained is determined by the acetin process 1 (p. 213). The estimation of the glycerol in the solution by the perman¬ ganate process (p. 208) may also be resorted to, but there is always the possibility that some other organic substances may be present yielding oxalic acid on oxidation. If sugar be present at the same time, as in cheap transparent soaps, these methods are obviously useless unless the sugar be first removed (cp. 3. below). 2. Aleohol.—Alcohol, if present at all, is found, as a rule, in such minute quantities that it is unnecessary to determine it. If larger amounts be suspected, 50 to 60 grms. of the soap are mixed with pumice, according to Valenta , 2 and the alcohol distilled off by immersing the flask in a paraffin bath, heated at first to 110° C., and afterwards to 120° C. The distillate is tested for alcohol by the iodoform test, carried out, according to Hager , in the following manner: Add to the liquid 5-6 c.c. of a 10 per cent caustic potash 1 Lewkowitsch, Chem. Zeit. 1889, 659. 2 Jacobsen’s Repertorium, 1884, i. 244. XII SOAPS 783 solution, warm to 40°-50° C., and add a 16-20 per cent solution of potassium iodide, saturated with iodine till the liquid appears yellowish-brown. If the colour should not disappear on shaking, introduce caustic potash by means of a glass rod till discolouration just ensues. If alcohol be present yellow crystals of iodoform separate either at once or after some time; examined under the microscope they appear as hexagonal plates. 3. Sugar is present to a considerable extent (25 per cent) in some transparent soaps, hence its determination may be required. This is best effected by boiling the filtrate (or a measured portion of it) obtained in (a) with dilute sulphuric acid to invert the sugar, making alkaline, and boiling after previous dilution so as to prevent oxida¬ tion of glycerol by Fehling’s solution. The separated Cu 2 0 is esti¬ mated in the usual way and calculated to sugar. If glycerol and sugar be present conjointly, and both substances are to be estimated, separation is effected, according to Donath and Mayrhofer, 1 by adding to the solution a quantity of slaked lime sufficient to combine with the sugar present, and an equal quantity of washed and ignited sand, then boiling down to the consistency of a syrup, pulverising the residue after cooling, and exhausting it in a corked flask with 80-100 c.c. of a mixture of equal volumes of alcohol and ether. The solution will then contain all the glycerol, free from sugar, and it may be estimated as described under (g) 1. 4. Carbolic Acid. —As the use of carbolic soap in this country is somewhat extensive, the estimation of phenols (carbolic acid, cresylic acid) may be sometimes required. Allen 2 proposes the following method:— 5 grms. of the sample are dissolved in warm water, and a sufficient quantity of a 10 per cent caustic soda solution added to neutralise the phenols. The soap solution is then shaken out with ether to remove any coal-tar hydrocarbons, introduced into the soap with impure cresylic acid (their amount may be determined by evaporating the ether and weighing the residue). The alkaline liquid separated from the ether is next treated in a separating funnel with excess of strong brine, which throws out the dissolved soap as a granular mass, the sodium phenates remaining in solution. If the soap refuses to coagulate (as in presence of much resin), addition of a small quantity of dissolved tallow or palm curd will remedy the defect. The solu¬ tion is separated from the soap by filtering, the soap washed on the filter with brine, and the filtrate made up to 1000 c.c. A portion of this liquid, say 100 c.c., is tested first for complete removal of soap by shaking in a separating funnel with dilute sulphuric acid, when no turbidity should appear. Standard bromine water is then run in gradually with occasional shaking, until the yellowish colouration of the liquid indicates a slight excess of bromine. The bromine solution is standardised by means of pure crystallised phenol or by cresylic acid, according as phenol or cresol is contained in the soap. In the former case the precipitated tribromophenol forms snow-white crystal- 1 Zeitsch. analyt. Chem. 20. 383. 2 The Analyst , 1886, 103. 784 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. line flocks, whereas, in the latter case, the precipitate is milky and does not separate well from the liquid. The remaining portion of the 1000 c.c. may be boiled down to a small bulk, acidulated with sulphuric acid, and treated with a slight excess of bromine. The liquid is then shaken out repeatedly with small quantities of carbon bisulphide—5 c.c. each time—until the solvent no longer acquires a red or yellow coloui’, and the carbon bisulphide evaporated off, when the bromo-derivatives of the phenols remain behind. If pure crystal¬ lised phenol has been mixed with the soap, fine, long, almost colour¬ less needles are obtained. By multiplying their weight by 0 - 281 the proportion of phenol is found approximately. If cresylic acid has been used the residue will be deep yellow, orange, or red, with little or no tendency to crystallise; in that case its weight need not be determined, as it would not furnish even a rough approximation to the actual quantity of cresylic acid present. 1 In practice the writer considers the following method sufficiently accurate:—Weigh off a somewhat large amount of the sample, say 100 grms., treat as described to separate the soap, boil down the solution of the phenate to a small bulk, transfer to a stoppered measuring cylinder of 50 or 100 c.c. capacity, add sufficient salt so that some remains undissolved, and acidify with sulphuric acid. The volume of the separated phenols is then read off and the number of c.c. taken as so many grams. Textile soaps 2 are often submitted to the analyst to obtain an opinion as to their suitability. Soap intended for scouring raw wool should be devoid of free caustic alkali, as the free alkali has an injurious action on the wool, destroying its surface by pitting the scales and taking away its lustre. Potash soap is preferable to soda soap, cwteris 'paribus . A small amount of alkaline carbonate may be permissible if the raw wool is of inferior quality. Unsaponified fat, unsaponifiable matter, resin, silicate, and “ fillers ” should be absent. A good many “ secret powders ” consist of sodium carbonate and inert substances with a minimum of palm oil soap. Soaps for scouring the woven woollen fabric should fulfil the same conditions, if they are intended for best class goods. A potash soap would also be preferable to a soda soap, cseteris paribus. For the scouring of low class goods, such as union goods for which mungo and shoddy are used, strongly alkaline soaps are demanded by manufacturers, and a certain amount of free caustic alkali and carbonates may be permissible under these circumstances, although it would be preferable to use a pure soap and add such 1 Fresenius and Makin {Jour. Soc. Chem. Ind. 1896) modify Allen’s method by dis¬ tilling the “ carbolic ” acid off in a current of steam and estimating the phenol by Kop- peschaar’s method. Obviously this elaborate method will not give greater accuracy. 2 Lewkowitsch, Jour. Soc. Byers and Colourists , 1894, 42 ; Jour. Soc. Chem. Ind. 1894. 258. XII METALLIC SOAPS 785 quantities of alkali as are considered necessary in the special case. Silicate and resin should, however, not occur in soaps of that kind, nor should the soap contain any unsaponified fat or unsaponifiable substances. Calico printers require a neutral soap, as any free alkali will act injuriously on the colour of the printed calico. Soap powders, dry soaps, washing- powders are mixtures of sodium carbonate with anhydrous soap reduced to a powder. They are largely adulterated with sand, sodium sulphate, and other inert substances. II.—Insoluble Soaps (Metallic Soaps) The metallic soaps are used for various purposes in the arts. Thus aluminium soaps, especially aluminium oleate, are employed as “ thickeners.” They are dissolved, with the aid of heat, in mineral oils, in order to impart to them a greater consistency with a view to producing oils of higher viscosity, or, as the term runs, having more “ body.” Lead and manganese soaps are used as “ driers ” in the manufac¬ ture of varnish from linseed oil (cp. p. 737 ); zinc, iron, nickel, cobalt, and chromium soaps are employed in the manufacture of coloured varnishes, or for water-proofing leather and canvas. 1 LeoA soaps, in their pure state, are principally used in the preparation of lead plaster. In this class of soaps must be also included the metallic resinates. Manganese resinate and lead resinate are soluble in warm linseed oil; these two salts are therefore used as liquid driers (cp. p. 737). Copper resinate is used as a rust preventive and for painting ships. Lime resinate is largely employed in the manufacture of solid lubricants (p. 726). All these soaps are prepared by double decomposition of the alkali soaps with aqueous solutions of the metallic salts. For analytical purposes the metallic soaps are decomposed by means of a suitable mineral acid (hydrochloric, nitric, sulphuric), when the fatty acids are obtained as an oily layer, and the metal passes into the acid solution. Both the fatty acids and the acid liquor are then examined in the usual way. (Cp. also “ Boiled Oil,” p. 735.) In the examination of lead plaster ether is the reagent employed to ascertain the origin of the fatty material. Lead plaster prepared from oleic acid is completely soluble, whereas plasters made from olive oil or lard leave, according to Kremel, 2 an ether residue of 17-20 and 40-50 per cent respectively. 1 Cp. Villon, Jour. Soc. Ghem. hid. 1S95, 802. 3 E 2 Pham. Post , 20. 190, 786 TECHNICAL AND COMMERCIAL ANALYSIS CHAl’. M. GLYCERIN Under the term “ glycerin ” we understand all those commercial products consisting of more or less pure “ glycerol,” C 3 H 8 0 :3 . Glycerin is the waste product of the candle and soap industries. It is obtained originally in dilute aqueous solutions, which contain various impurities depending on the process of saponification (cp. p. 745) employed. The purest raw material results from saponifica¬ tion by means of lime (magnesia), or water, the most impure in the soap manufactory, notably so if the fats and oils have been saponified by means of black ash lyes. Modern processes have, however, over¬ come the difficulties caused by the various impurities in such a manner that, e.g., chemically pure glycerins from soap-lyes and lime saponification cannot be distinguished. The glycerins obtained by the sulphuric acid saponification process retain some organic impuri¬ ties which seem to have hitherto defied all attempts to remove them, as the writer has ascertained in the case of a number of “ chemically pure ” glycerins originating from that process. The weak solutions of glycerol are concentrated after suitable purification, and refined by distillation in a current of superheated steam. Ranged according to purity, the following kinds of glycerin are distinguished in commerce :— 1. Chemically pure glycerin. 2. Dynamite glycerin. Distilled glycerin. 3. Crude glycerin. A fourth kind, refined glycerin , occupying an intermediate position between 2 and 3, was formerly manufactured from crude candle glycerins by treating with charcoal. It has, however, all but dis¬ appeared from the market during the last few years. 1. Chemically Pure Glycerin Chemically pure glycerin, in its most concentrated form, should approach as nearly as possible the chemical substance “ glycerol,” the properties of which have been described p. 77. Crystallised glycerin has been manufactured for some time, but its production has been abandoned latterly, owing to the high cost, the best brands of chemically pure glycerin fully equalling it, if not even surpassing it, since crystals are apt to enclose impurities. Chemically pure glycerin is prepared by repeated distillation of a carefully refined crude material. It is manufactured in varying con centrations, discerned according to their specific gravities as chemically pure glycerin D260, chemically pure glycerin D250, etc. These glycerins should be colourless, odourless, and of a pure sweet taste, and as free XII CHEMICALLY PURE GLYCERIN 787 from impurities as it is possible to make a chemically pure substance on a large scale. They should, therefore, consist of glycerol and water, with only infinitesimal quantities of impurities. The pre¬ paration demanded by the Pharmacopoeia is the purest commercial article. Qualitative Tests The following impurities should be tested for:— (a) Lime .—A few c.c. of the sample are mixed with twice the volume of distilled water, and a few drops of a solution of ammonium oxalate added. No turbidity must appear even after violent agita¬ tion and standing for some time. A precipitate would point to the admixture with badly distilled or even with “ refined glycerin.” (b) Lead .—Dilute the sample and add a solution of freshly pre¬ pared sulphuretted hydrogen, and afterwards some acetic acid. Ammonium sulphide, if used instead of sulphuretted hydrogen, would also indicate iron, insignificant traces of which cannot be objected to. (c) Arsenic .—This metal should be wholly absent. It should be borne in mind that, once arsenic has found its way into glycerin, it cannot be removed by the usual processes of refining, 1 as glycyl arsenite, As0 3 (C 3 H 5 ), the substance formed when arsenious acid is dissolved in glycerin, distils over with the latter. Hence many com¬ mercial brands are contaminated with arsenic, some to such an extent that they are decidedly harmful when used for medicinal preparations, or are otherwise taken inwardly. Marsh’s well-known test for arsenic is not sensitive enough, and it is better to substitute for it Gutzeit’s test, which combines with greater accuracy the advantage of rapidity. Place 1 c.c. of the sample in a high test-tube, add some zinc, free from arsenic, and a few c.c. of pure dilute sulphuric acid. The test- tube is then covered with a tightly fitting cap of filtering paper, two or three layers thick, the innermost layer having been previously moistened, by the aid of a glass rod, with a 50 per cent solution of silver nitrate. In presence of arsenic arseniuretted hydrogen is given off. After ten minutes’ standing the paper cap is taken off and examined. No deep yellow stain must be noticeable on the inner fold, a slight yellowish colouration only being permissible. This test is so extremely sensitive, that it is absolutely necessary to make side by side with it a blank test, using the same reagents. The silver nitrate test is almost too delicate (although there are com¬ mercial glycerins which will not show any colouration after ten minutes), and has therefore been replaced by less rigorous tests. A glycerin may be considered as free from arsenic if no yellow coloura¬ tion appears after ten minutes, if in Gutzeit’s test a concentrated solu¬ tion of mercury bichloride is substituted for silver nitrate. In case 1 Lewkowitsch, Year-Book of Pharmacy, 1890, 380. 788 TECHNICAL AND COMMERCIAL ANALYSIS chap. the latter reagent be used, hydrochloric acid may be employed instead of sulphuric acid. With silver nitrate hydrochloric acid is objection¬ able, as hydrochloric acid gas may possibly be given off if the liquid becomes too hot. Nagelwoort has stated recently 1 that coal gas, or even the quality of filter paper, may affect the test, and recommends therefore to con¬ duct the current of hydrogen and arseniuretted hydrogen over powdered silver nitrate placed in a U tube between two plugs of slag wool. This is an unnecessary complication of a simple test. It should, however, be noted that sulphuretted hydrogen, evolved if sulphides be present, also produces a yellow stain. In order to exclude errors sulphides must be oxidised to sulphates. I test for presence of sulphides by proceeding, as in Gutzeit’s test, but substi¬ tuting a paper cap moistened with lead acetate instead of silver nitrate; a black stain points to sulphides. (d) Chlorine. —Mix a few c.c. of the sample with twice the volume of pure water, acidify with nitric acid, and add a solution of silver nitrate ; no turbidity must then appear. (e) Iron. —Tested with a solution of tannic acid no bluish coloura¬ tion must appear. (/) Ash. —The last traces of metals (iron, copper) cannot be removed from a product manufactured on a large scale. The deter¬ mination of the ash in a sample will prove whether the permissible minimum has been exceeded. The table given p. 790 shows the amounts of ash found in chemi¬ cally pure glycerins of commerce. ( g ) Organic impurities . 2 —These impurities are due to faulty manu¬ facture, and may either consist of acrolein and volatile fatty acids, as butyric acid , or of substances having a higher boiling point than glycerol itself. The latter substances may be comprised under the name poly glycerols. A rapid “ practical ” test for volatile fatty acids is to spread a few drops of the sample on the back of the hand, and rub it gently into the skin. No smell of acrolein or butyric acid should be then noticeable. A better method is to mix the sample with alcohol and concentrated sulphuric acid, when in presence of butyric acid the characteristic smell of pine apples, due to ethyl butyrate, will be noticed at once. Acrolein , as also other reducing substances, is best detected by adding a few drops of a silver nitrate solution to the aqueous solution of glycerin. No blackening or browning should appear after stand¬ ing for twenty-four hours at the ordinary temperature. The German Pharmacopoeia, edit, iii., prescribes the silver test in the following form :—Heat 1 c.c. of glycerin with 1 c.c. of ammonia to boiling and add three drops of silver nitrate solution. No dis¬ colouration should be noticeable within five minutes. This test was originally intended to detect presence of arsenic, but 1 Pharm. Rvnd. 1894, 109. 2 Lewkowitsch, Year-Book of Pharmacy. 1890, 382. XII CHEMICALLY PURE GLYCERIN 789 is absolutely unreliable for this purpose. It is also worthless for the detection of other impurities, as it depends so much on the mode of operating, that on the one hand an impure glycerin, one even that has not been distilled, may conform to the test, whereas on the other hand a pure glycerin may have to be rejected. At the temperature of boiling water a mixture of glycerol and silver nitrate does become reduced at once on addition of ammonia (p. 82). If the enormous excess of ammonia is mixed with glycerol, according to the directions of the Pharmacopceia, ebullition of the liquid may take place before the temperature of 100 C. is reached, and in that case silver nitrate subsequently added will not be reduced. This method should therefore be abandoned, 1 or, at any rate, used with great caution. From these remarks it will be understood that the silver nitrate test described, viz. addition of silver nitrate in the cold, can be made far more sensitive if, instead of neutral silver nitrate, an ammoniacal silver nitrate solution be used in the cold. Even the minutest traces of organic impurities, such as acrolein, may be thus detected. Acrolein may be also detected by means of Schiff’s reagent. This is prepared by dissolving 1 grm. of magenta crystals in a 1000 c.c. flask in about 700 c.c. of water, adding 10 grms. of sodium bisulphite previously dissolved in 100 c.c. of water and 15 c.c. of strong hydro¬ chloric acid, and finally making up to 1000 c.c. The test is made by placing a few c.c. of the sample in a test-tube, and carefully pouring on to it, so that no mixing takes place, a few c.c. of the reagent. No violet-coloured zone should appear between the two layers. (h) Sugar .—Adulteration of glycerin with sugar (cane sugar or glucose) does occur when glycerin is high in price. The presence of sugars is detected by the polarimeter. Quantitative Tests The polyglycerols are tested for 2 by allowing an accurately weighed quantity of the sample to evaporate gently at 160" C. Care should be taken not to heat too rapidly, otherwise even the purest glycerin may become polymerised with the production of that very substance that is to be detected. From the weight of the residue the weight of ash, subsequently found on incineration, must be deducted. The difference (the “ organic residue ”) gives a fair indication as to the care with which the glycerin has been manufactured, The following table gives the “organic residue” and ash of a number of “chemically pure glycerins” examined in the writer’s laboratory, 2 and arranged according to the amount of organic residue :— 1 It may be added here that the Pharmacopceia test has met with a strenuous objec¬ tion on the part of a number of German glycerin manufacturers, who declared in a circular that they could not supply an article satisfying the Pharmacopoeia test. 2 Cp. Lewkowitsch, Year-Book of Pharmacy, 1890, 382. 790 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. No. Residue at 160’ C. Ash. Organic Residue. Per cent. Per cent. Per cent. i 0-03033 0-00603 0-0243 2 0-0276 0-00300 0-0246 3 0-0377 0-005 0-0327 4 0-0498 0-0138 0-0360 5 0-0452 0-0081 0-0371 6 0-0509 0-0066 0-0443 7 0-0656 0-0139 0-0517 8 0-0748 0-0140 0-0738 9 0-0905 0-0154 0-0751 10 0-1047 0-0190 0-0857 11 0-1236 0-0305 0-0931 12 0-1621 0-0183 0T438 13 0-8060 0-2090 0-5970 Rules for the valuation of commercial chemically pure glycerins may be derived from this table. The first seven samples certainly deserve the name of chemically pure glycerin, the following four samples represent lower qualities unfit for pharmaceutical purposes, whereas the last two samples are simply glycerins refined by dis¬ tillation ; the last sample would be rejected as unsuitable even by dynamite makers. Sample No. 2 represents chemically pure glycerin manufactured by the writer on a large scale from soap-lye glycerin. The percentage of glycerol in a sample may be determined either by physical or chemical methods. A. Physical Methods (a) Specific Gravity. —Tables for the specific gravities of aqueous solutions of glycerin have been given by Fabian, Metz, Schweikert, a.o. The most accurate numbers are those published by Lenz, 1 Strohmer , 2 Gerlach , 3 Skalweitf and Nicol . 5 The following tables contain the numbers of Lenz, Strohmer, Ger¬ lach, and Nicol; those given by Skalweit will be found on p. 796. 1 Zeitscli. analyt. Chem. 19. 302. ‘ 2 Monatshefte fiir Chemie, 5. 61. 3 Chemische Industrie, 7. 281. 4 Repert. omalyt. Chem. 5. 18. 5 Pharm. Jour, and Transact. 1887, 297. [Table CHEMICALLY PURE GLYCERIN 791 Specific Gravities of Aqueous Solutions of Glycerin Lenz. Stboiimer. Gerlach. Nicol. Glycerol. Spec. Grav. at 12“-14“ C. Spec. Grav. Spec. Grav. Spec. Grav. Spec. Grav. Per cent. at 17-5° C. at 15“ C. at 20“ C. at 20“ C. Water at Water at Water at Water at Water at 12“ C. =1. 17-5° C.=l. 15° C. =1. 20° C. =1. 20“ C. =1. 100 1-2691 1-262 1-2653 1-2620 1-26348 99 1-2664 1-259 1 -2628 1-2594 1-26091 98 1-2637 1-257 1-2602 1-2568 1 -25832 97 1-2610 1-254 1-2577 1-2542 1 -25572 96 1-2584 1-252 1-2552 1-2516 1-25312 95 1-2557 1-249 1 "2526 1-2490 1-25052 94 1-2531 1-246 1-2501 1-2464 1-24790 93 1 -2504 1-244 1-2476 1-2438 1-24526 92 1-2478 1-241 1-2451 1-2412 1-24259 91 1-2451 1-239 1-2425 1-2386 1-23990 90 1-2425 1-236 1-2400 1-2360 1-23720 89 1-2398 1 -233 1-2373 1 -2333 1-23449 88 1-2372 1-231 1-2346 1 -2306 1-23178 87 1-2345 1-228 1-2319 1-2279 1-22907 86 1-2318 1-226 1 -2292 1-2252 1-22636 85 1 -2292 1-223 1 -2265 1 "2225 1-22365 84 1-2265 1-220 1-2238 1-2198 1-22094 83 1-2238 1-218 1-2211 1-2171 1-21823 82 1-2212 1-215 1-2184 1-2144 1-21552 81 1-2185 1-213 1-2157 1-2117 1-21281 80 1-2159 1-210 1-2130 1 -2090 1-21010 79 1-2122 1-207 1-2102 1-2063 1-20739 78 1-2106 1-204 1-2074 1 -2036 1-20468 77 1-2079 1-202 1-2046 1-2009 1-20197 76 1-2042 1-199 1-2018 1-1982 1-19925 75 1-2016 1-196 1-1990 1 -1955 1-19653 74 1-1999 1-193 1-1962 1-1928 1-19381 73 1-1973 1-190 1-1934 1-1901 1-19109 72 1-1945 1-188 1-1906 1-1874 1-18837 71 1-1918 1-185 ] -1878 1-1847 1-18565 70 1-1889 1-182 1-1850 1-1820 1-18293 69 1-1858 1-179 1-18020 68 1-1826 1-176 1-17747 67 1-1795 1-173 1-17474 66 1-1764 1-170 1-17201 65 1-1733 1-167 1-1711 1 "1685 1-16928 64 1-1702 1-163 * 1-16654 63 1-1671 1-160 1-16380 62 1-1640 1157 1-16107 61 1-1610 1-154 1-15834 60 1-1582 1-151 1-1570 1-1550 1-15561 59 1-1556 1-149 1-15288 58 1-1530 1-146 1-15015 57 1-1505 1-144 1-14742 56 1-1480 1-142 1-14469 55 1-1455 1-140 1-1430 1-1415 1-14196 54 1-1430 1-137 1-13923 53 1-1403 1 -135 1-13650 52 1-1375 1-133 1-13377 51 1-1348 1-130 1-13104 50 1 -1320 1-128 1-1290 l-i - 280 1-12831 45 1-1183 1-1155 1-1145 1-11469 40 1-1045 1-1020 1-1010 1-10118 35 1-0907 1-0885 1-0875 1-08786 30 1-0771 1-0750 1-0740 1-07469 25 1-0635 1-0620 1-0610 1-06166 20 1-0498 1-0490 1-0480 1-04884 15 1-0374 1-03622 10 1-0245 1-0245 1-0235 1 02391 5 1-0123 1-01184 0 1-0000 1 -o’ooo 1-0000 1-00000 792 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. Lenz has made his determinations with a sample of chemically pure glycerin, the glycerol in which had been estimated by ultimate analysis. Strohmer employed crystallised glycerin freed from water by pressing repeatedly between folds of filter paper. Gerlach, again, prepared his most concentrated glycerin by boiling down chemically pure glycerin 1 ’220, until its boiling point remained constant at 290° C. The specific gravities of aqueous solutions for each degree below 50 per cent are given in the tables pp. 795, 796. Specific gravities found at temperatures other than those men¬ tioned in the table may be corrected by reference to the following table, due to Gerlach .-— Expansion of Aqueous Solutions of Glycerin. Volume at 0° C. = 10,000 Glycerol Volume at 0° C. Volume at 10° C. Volume at 20° C. Volume at 30° C. Per cent. 0 10 20 30 40 50 60 70 80 90 100 10,000 10,000 10,000 10,000 10,000 10,000 10,000 10,000 10,000 10,000 10,000 10,001-3 10,010 10,020 10,025 10,030 10,034 10,038 10,042 10,043 10,045 10,045 10,016-0 10,030 10,045 10,058 10,067 10,076 10,084 10,091 10,092 10,095 10,090 10,041-5 10,059 10,078 10,097 10 , in 10,124 10,133 10.143 10.144 10,148 10,150 The numbers for intermediate temperatures are found by inter¬ polation. For temperatures lying between 15° and 20° C. the specific gravity can be calculated from the numbers given in Gerlach's table (p. 791) by means of the following formula :— *-15. ^ S( = S 1 + ~— (Sg-Si), where s, is the specific gravity of the glycerin at 15° C. Water at 15° C. =1. *2 „ „ „ 20° C. ,, 20° C. =1. St „ „ „ f C. ,, <°C.=1. A few of the numbers contained in the table p. 791 have been controlled by Morawski 1 by means of ultimate analysis. His results show that Lenz’s figures are, as a rule, a little too low, those of Strohmer a little too high, whereas Gerlach's and Skalweit’s values agree both amongst themselves arid with the results of elementary analysis. 1 Jmr. Soc. Chem. Ind. 1889, 424. XII CHEMICALLY PURE GLYCERIN 793 The specific gravity of the sample is taken in the usual manner, using one of the methods described page 124. In the case of the most concentrated glycerin a slight complication arises, inasmuch as air bubbles easily become entangled, which rise only very slowly in the viscous liquid at the ordinary temperature. Thus if the hydrostatic balance be used, as is stipulated in many contracts (especially for dynamite glycerin, p. 802), the determination may take hours, if the glycerin has not been poured into the cylinder carefully, allowing the substance to flow along the side of the vessel. Iiehner 1 recommends to fill a Sprengel tube with the glycerin at a higher temperature than the ordinary with the aid of the filter-pump, and then to immerse the tube in water of the normal temperature; for any other temperature a correction of 0‘00058 for each degree centigrade must be made. By means of this factor Richmond has calculated Lenz’s table to 15‘5° C.— Glycerol. Specific Gravity at 15-5° C. Glycerol. '1 Specific Gravity at 15 "5° C. Per cent. 100 1-2674 Per cent. 87 1 -2327 99 1-2647 86 1-2301 98 1-2620 85 1 -2274 97 1-2594 84 1-2248 96 1-2567 83 1-2222 95 1-2540 82 1-2196 94 1-2513 81 1-2169 93 1-2486 80 1-2143 92 1-2460 79 1-2117 91 1 -2433 78 1-2090 90 1-2406 77 1-2064 89 1-2380 76 1-2037 88 1-2353 75 1-2011 The writer prefers the following method :—The sample is warmed in a closed bottle by immersing in warm water until all air bubbles have risen to the top. The glycerin is then allowed to cool in the closed bottle, preferably to the normal temperature, and then carefully filled into the ordinary specific bottle provided with a perforated stopper. If this has been pushed home, after the last filling up, the very small drop of glycerin squeezed out is wiped off with a linen cloth, and the bottle taken out of the water-bath. A number of com¬ parative experiments, those made with the Sprengel tube being used as the standard, has proved that the specific gravities are correct to the fourth decimal if the weights are reduced to vacuum. Any com¬ plicated calculation is avoided by determining once for all the necessary corrections for the picnometer when filled with water. Suppose the weight p has been found in air, then the corrected weight P, will be P =p +^R. 1 Jour. Soc. Chem. Ind. 1889, 8. 794 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. If brass weights are used, the correction, R, for the specific gravities likely to occur is found in the following table : 1 — Correction for Weights in Vacuo Specific Gravity. R. l'OO . . . 0-00106 1-02 . . . 0-00103 1-04 .... 0-00101 1-06 . . 0-00099 1-08 . . 0-00097 1-10 . . . 0-00095 1-15 . . . 0-00090 1-20 . . . 0-00086 1-25 . . . 0-00082 1-30 . . . 0-00078 (b) Refractive Index. —If a refractometer be available, the glycerol in the sample can be determined very rapidly and with very great accuracy. The refractometric constant is found in a shorter time than that at which a specific gravity determination can be made. It has the further advantage that only one drop is required. The values given in the following tables, due to Lenz, Strohmer , and SJcalweit, have been determined with Abbe's refractometer. Of course, the butyro-refractometer (p. 116) may also be used. According to Lenz, the several observations agree amongst each other to a few units of the fourth decimal, whilst the difference in the refractive indices corresponding to 1 per cent of glycerin amounts to 13 - 5 units of the fourth decimal. By reference to the tables, the percentage of glycerol in a sample can therefore be determined accurately to about 0'5 per cent. 1 Landolt, Optisches Drehungsvermogen , p. 131. [Table XII CHEMICALLY PURE GLYCERIN 795 Specific Gravities and Refractive Indices of Aqueous Solutions of Glycerin (Lenz) Glycerol. Sp. Gr. at 12°-14° C. Ref. Ind. at 12-5°- 12-8° C. Glycerol. Sp. Gr. at 12°-14° C. Ref. Ind. at 12-5°- 12-8° C. Glycerol. Sp. Gr. at 12°-14° C. Ref. Ind. at 12-o°- 12 8° C. Per cent. Per cent. Per cent. 100 1-2691 1-4758 66 1-1764 1-4249 32 1-0825 1-3745 99 1-2664 1-4744 65 1-1733 1-4231 31 1-0798 1-3732 98 1-2637 1-4729 64 1-1702 1-4213 30 1-0771 1-3719 97 1-2610 1-4715 63 1-1671 1-4195 29 1-0744 1-3706 96 1-2584 1 -4700 62 1-1640 1-4176 28 1-0716 1-3692 95 1 "2557 1-4686 61 1-1610 1-4158 27 1-0689 1-3679 94 1-2531 1-4671 60 1-1582 1-4140 26 1-0663 1-3666 93 1-2504 1-4657 59 1-1556 1-4126 25 1-0635 1 -3652 92 1-2478 1-4642 58 1-1530 1-4114 24 1-0608 1 -3639 91 1-2451 1-4628 57 1-1505 1-4102 23 1-0580 1-3626 90 1-2425 1-4613 56 1-1480 1-4091 22 1 -0553 1-3612 89 1 -2398 1-4598 55 1-1455 1 -4079 21 1-0525 1-3599 88 1 -2372 1-4584 54 1-1430 1-4065 20 1-049S 1-3585 87 1 -2345 1-4569 53 1-1403 1-4051 19 1-0471 1 -3572 86 1-2318 1-4555 52 1-1375 1-4036 18 1-0446 1-3559 85 1-2292 1-4540 51 1-1348 1-4022 17 1-0422 1-3546 84 1 -2265 1-4525 50 1-1320 1-4007 16 1-0398 1 "3533 83 1 -2238 1-4511 49 1-1293 1-3993 15 1-0374 1-3520 82 1-2212 1-4496 48 1-1265 1-3979 14 1 -0349 1 -3507 81 1-2185 1-4482 47 1-1238 1-3964 13 1-0332 1 -3491 80 1-2159 1 -4467 46 1-1210 1-3950 12 1-0297 1-3480 79 1-2122 1-4453 45 1-1183 1-3935 11 1-0271 1 -3467 78 1-2106 1-4438 44 1-1155 1-3921 10 1-0245 1-3454 77 1 -2079 1-4424 43 1-1127 1 -3906 9 1-0221 1-3442 76 1-2042 1-4409 42 1-1100 1-3890 8 1-0196 1-3430 75 1-2016 1-4395 41 1-1072 1-3875 7 1-0172 1-3417 74 1-1999 1 -4380 40 1-1045 1-3860 6 1-0147 1-3405 73 1-1973 1 -4366 39 1-1017 1 -3844 5 1-0123 1-3392 72 1-1945 1-4352 38 1-0989 1-3829 4 1-0098 1-3380 71 1-1918 1-4337 37 1-0962 1-3813 3 1-0074 1-3367 70 1-1889 1-4321 36 1-0934 1-3798 2 1-0049 1-3355 69 1-1858 1-4304 35 1-0907 1-3785 1 1-0025 1-3342 68 1-1826 1-4286 34 1-0880 1-3772 67 1-1795 1-4267 33 1*0852 1 -3758 [Table 796 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. Specific Gravities and Refractive Indices of Aqueous Solutions of Glycerin ( Strohmer) Glycerol. Per cent. Sp. Gr. at 17-o° C. Ref. Ind. at 17-5°C. Glycerol. Per cent. Sp. Gr. at 17-5° C. Ref. Ind. at 17-5° C. Glycerol. Per cent. Sp. Gr. at 17-5° C. Ref. Ind. at 17-5° C. 100 1-262 1-4727 83 1-218 1-447S 66 1-170 1 -4206 99 1-259 1-4710 82 1-215 1-4461 65 1-167 1-4189 98 1-257 1-4698 81 1 "213 1-4449 64 1-163 1-4167 97 1-254 1-4681 80 1-210 1-4432 63 1-160 1-4150 96 1-252 1-4670 79 1-207 1-4415 62 1-157 1-4133 95 1 "249 1-4653 78 1-204 1-4398 61 1T54 1-4116 94 1-246 1-4636 77 1-202 1-4387 60 1-151 1-4099 93 1-244 1 -4625 76 1-199 1-4370 59 1T49 1-4087 92 1-241 1-4608 /o 1-196 1-4353 58 1-146 1-4070 91 1-239 1-4596 74 1-193 1-4336 57 1-144 1-4059 90 1-236 1-4579 73 1-190 1-4319 56 1-142 1-4048 89 1 -233 1-4563 72 1-188 1-4308 55 1-140 1-4036 88 1-231 1-4551 71 1-185 1-4291 54 1-137 1-4019 87 1-228 1-4534 70 1-182 1-4274 53 1-135 1-4008 86 1-226 1-4523 69 1-179 1-4257 52 1-133 1-3997 85 1-223 1-4506 68 1-176 1-4240 51 1-130 1-3980 84 1-220 1-4489 67 1-173 1-4223 50 1-128 1-3969 Specific Gravities and Refractive Indices of Aqueous Solutions of Glycerin ( Skalweit) Glycerol. Per cent. Sp. Gr. at 15° C. , 1 [d] 1 at 15° C. Glycerol. Per cent. Sp. Gr. at 15° C. »[„] at 15° C. Glycerol. Per cent. Sp. Gr. at 15° C. *Td] at 15° C. 0 1-0000 1-3330 34 1-0858 1-3771 68 1-1799 1-4265 1 1-0024 1-3342 35 1-0885 1-3785 69 1T827 1-4280 2 1-0048 1-3354 36 1-0912 1-3799 70 1-1855 1-4295 3 1-0072 1-3366 37 1-0939 1-3813 71 1-1882 1-4309 4 1-0096 1-3378 38 1-0966 1-3827 72 1-1909 1-4324 5 1-0120 1-3390 39 1-0993 1-3840 73 1-1936 1-4339 6 1-0144 1-3402 40 1-1020 1-3854 74 1-1963 1-4354 7 1-0168 1-3414 41 1-1047 1-3868 75 1-1990 1-4369 8 1-0192 1-3426 42 1-1074 1 -3882 76 1-2017 1-4384 9 1-0216 1-3439 43 1-1101 1-3896 77 1-2044 1-4399 10 1-0240 1-3452 44 1-1128 1-3910 78 1-2071 1-4414 11 1-0265 1-3464 45 1-1155 1-3924 79 1-2098 1-4429 12 1-0290 1-3477 46 1-1182 1 -3938 80 1-2125 1-4444 13 1-0315 1 -3490 47 1-1209 1-3952 81 1-2152 1-4460 14 1-0340 1-3503 48 1-1236 1-3966 82 1-2179 1-4475 15 1-0365 1-3516 49 1-1263 1 -3981 83 1-2206 1-4490 16 1-0390 1 -3529 50 1-1290 1-3996 84 1-2233 1-4505 17 1-0415 1-3542 51 1-1318 1-4010 85 1-2260 1-4520 18 1-0440 1-3555 52 1-1346 1-4024 86 1-2287 1-4535 19 1-0465 1-3568 53 1-1374 1-4039 87 1-2314 1-4550 20 1-0490 1-3581 54 1-1402 1-4054 88 1-2341 1-4565 21 1-0516 1 -3594 55 1-1430 1-4069 89 1-2368 1-4580 22 1-0542 1-3607 56 1-1458 1-4084 90 1-2395 1-4595 23 1-0568 1 -3620 57 1-1486 1-4099 91 1-2421 1-4610 24 1-0594 1-3633 58 1-1514 1-4104 92 1-2447 1-4625 25 1-0620 1-3647 59 1T542 1-4129 93 1-2473 1-4640 26 1-0646 1 -3660 60 1-1570 1-4144 94 1-2499 1-4655 27 1-0672 1-3674 61 1-1599 1-4160 95 1 -2525 1-4670 28 1-0698 1-3687 62 1-1628 1-4175 96 1-2550 1-4684 29 1 -0724 1-3701 63 1-1657 1-4190 97 1 -2575 1-4698 30 1-0750 1-3715 64 1-1686 1-4205 98 1-2600 1-4712 31 1-0777 1-3729 65 1-1715 1 -4220 99 1 -2625 1-4728 32 1-0804 1-3743 66 1-1743 1-4235 100 1-2650 1-4742 33 1-0831 1-3757 67 1-1771 1-4250 1 is the refractive index for the sodium line D. XII CHEMICALLY PURE GLYCERIN 797 It must be distinctly understood that the refractive indices are accurate only for the temperatures stated, the indices varying with the temperature, as may be gathered from the following table:— Specific Gravity. Variation of Refractive Index for 1° C. Observer. 1-25350 0-00032 Listing 1-24049 0-00025 Van der Willigen 1-19286 0-00023 1-16270 0-00022 1-11463 0-00021 > > The variation in the case of pure water is (P00008 for 1 C. With a view to eliminating slight errors due to the adjustment of the instrument, and to reduce the influence of temperature, Lenz re¬ commends to take, immediately after the sample has been examined, the refractive index of water, having, of course, the same temperature. Thus the numbers of the following table have been obtained :— Difference between Refractive Indices of Aqueous Solutions of Glycerin and Pure Water {Lenz) Glycerol "[»] Glycerol Water. Glycerol n W Glycerol " Vi Water. Glycerol > l [D] Glycerol _n fD] Water. Glycerol "M Glycerol ->1 Water. Per cent. Per cent. Per cent. Per cent. 100 0-1424 74 0-1046 48 0-0645 22 0-0288 99 0-1410 73 0-1032 47 0-0630 21 0-0275 98 0-1395 72 0-1018 46 0-0616 20 0-0261 97 0-1381 71 0-1003 45 0-0601 19 0-0238 96 0-1366 70 0-0987 44 0-0587 18 0-0225 95 0-1352 69 0-0970 43 0-0572 17 0-0212 94 0-1337 68 0-0952 42 0-0556 16 0-0199 93 0-1323 67 0-0933 41 0-0541 15 0-0186 92 0-1308 66 0-0915 40 0-0526 14 0-0173 91 0-1294 65 0-0897 39 0-0510 13 0-0160 90 0-1279 64 0-0889 38 0-0495 12 0-0146 89 0-1264 63 0-0861 37 0-0479 11 0-0133 88 0-1250 62 0-0842 36 0-0464 10 0-0120 87 0-1235 61 0-0824 35 0-0451 9 0-0108 86 0-1221 60 0-0806 34 0-0438 8 0-0096 85 0-1206 59 0-0792 33 0-0424 7 0-0083 84 0-1191 58 0-0780 32 0-0411 6 0-0071 83 0-1177 57 0-0768 ■ 31 0-0398 5 0-0058 82 0-1162 56 0-0757 30 0-0385 4 0-0046 81 0-1148 55 0-0745 29 0-037.2 3 0-0033 80 0-1133 54 0-0731 28 0-0358 2 0-0021 79 0-1119 53 0-0717 27 0-0345 1 0-0008 78 0-1104 52 0-0702 26 0-0332 0 o-oooo 77 0-1090 51 0-0688 25 0-0318 76 0-1075 50 0-0663 24 0-0315 75 0-1061 49 0*0659 23 0-0302 798 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. (c) Vapour Tension.—The percentage of glycerol in aqueous solutions may be also estimated by the tension of the vapour given off. Gerlach has designed for this purpose the vaporimeter 1 shown in Fig. 48. It consists of the hollow cylinder A, made of copper or Fig. 48. German silver, braized on to the metal dish B. The glass cylinder G is fastened to A by means of stout india-rubber tubing, tied on with wire, and then secured by the conical clamp H. Nozzle C is fitted 1 Made by F. Muller, Dr. Geissler’s Nachfolger, Bonn a/Rli. XII CHEMICALLY PURE GLYCERIN 799 with an india-rubber stopper, through which passes one end of the gauge (manometer) D' D". To use the instrument, the glass cylinder G and bottle F are detached, the plug taken out of the tap, and the instrument hung up by the hook fastened to its bottom. F is then rinsed out with the sample of glycerin, and filled with mercury up to a mark on the neck, and then completely with glycerin. After allowing to stand until all air-bubbles have escaped the bottle is attached to the end of D', which is well ground so as to fit into the neck of F. When the glycerin has ceased to drain out, the plug is put in its place, G is attached to A, and filled with water. This is then heated to boiling, when the sample will emit vapour which drives mercury into the gauge D' D". A short thread of glycerin precedes the mercury; by suitable adjustment, effected by taking out the plug for a moment, the thread is made equally long in all experiments. If the bottle F has been charged in a blank experiment with water, the mercury will rise so high in D" that its level is the same as the mercury in the bottle, since the vapour tension of water, at its boiling point, equals the atmospheric pressure. This point is marked on the scale as the zero point, its position being, of course, the same for all pressures of the atmosphere, since a change in the latter influences both the boiling point of the water in G and the vapour tension in F in the same manner. From the zero point downwards (and also upwards) the scale is divided into millimetres. On examining glycerin in the vaporimeter, the zero point will, of course, not be reached. The number read off the scale requires, however, a correction, the level of the mercury in the bottle F being now higher than in the blank test. This increase in height must be added to the reading. Each instrument is provided by the maker with a table, stating this correction for the interval from 0 to 500 mm., from which the correction for each experiment can be cal¬ culated. Example .—Let the correction for an interval from 0-500 mm. be given as 21 mm., and in an actual experiment with glycerin 492 mm. be read off the scale of the vaporimeter as the level of the mercury. The correction is then calculated by means of the proportion 500 : 21 = 492 : x, hence x= 20 - 6. Consequently, the actual decrease of the vapour tension of the sample of glycerin equals 492 + 20 , 6 = 512'6. From the table given p. 800 we find that the sample contains 70 per cent of glycerol. [Table 800 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. Specific Gravities, Boiling Points, and Vapour Tensions of Aqueous Solutions of Glycerin ( Gerlach ) Parts of Glycerol Specific Gravity. Boiling [ Vapour Tension at 100° O. Glycerol. compared with 100 parts of Water. At 15° C. Water 15° C. = 1. At 20° C. Water 20° C. = 1. Point. At 760 mm. Pressure. Per cent. 100 Glycerin 1-2653 1-2620 °C. 290 mm. 64 99 9900 1-2628 1-2594 239 87 98 4900 1-2602 1-2568 208 107 97 3233-333 1-2577 1-2542 188 126 96 2400 1-2552 1-2516 175 144 95 1900 1-2526 1 -2490 164 162 94 1566'666 1-2501 1-2464 156 180 93 1328-571 1-2476 1-2438 150 198 92 1150 1-2451 1-2412 145 215 91 1011-111 1-2425 1-2386 141 231 90 900 1-2400 1-2360 138 247 89 809-090 1 -2373 1-2333 135 263 88 733 -333 1-2346 1-2306 132-5 279 87 669-231 1-2319 1-2279 130-5 295 86 614-286 1 -2292 1-2252 129 311 85 566-666 1-2265 1-2225 127-5 326 84 525 1-2238 1-2198 126 340 83 488-235 1-2211 1-2171 124-5 355 82 455-555 1-2184 1-2144 123 370 81 426-316 1-2157 1-2117 122 384 80 400 1-2130 1-2090 121 396 79 376-190 1-2102 1-2063 120 408 78 354-500 1-2074 1-2036 119 419 77 334-782 1-2046 1-2009 118-2 430 76 316-666 1-2018 1-1982 117-4 440 75 300 1-1990 1-1955 116-7 450 74 284-615 1-1962 1-1928 116 460 73 270-370 1-1934 1-1901 115-4 470 72 257-143 1-1906 1-1874 114-8 480 71 244-828 1-1878 1-1847 114-2 489 70 233-333 1-1850 1-1820 113-6 496 65 185-714 1-1710 1-1685 111-3 553 60 150 1-1570 1-1550 109 565 55 122-222 1-1430 1-1415 107-5 593 50 100 1-1290 1-1280 106 618 45 81-818 1-1155 1-1145 105 639 40 66-666 1-1020 1-1010 104 657 35 53-846 1-0885 1 -0875 103-4 675 30 42-857 1-0750 1-0740 102-8 690 25 33-333 1-0620 1-0610 102-3 704 20 25 1-0490 1-0480 101-8 717 10 11-111 1-0245 1-0235 100-9 740 _ 0 0 1-0000 1*0000 100 _j 760 In the case of samples containing more than 70 per cent of glycerol an india-rubber tubing should be attached to limb D", and suction applied, so as to expedite vaporising. But in the case of anhydrous glycerin even this device fails. XII CHEMICALLY PURE GLYCERIN 801 It is evident that for practical purposes this method of ascertaining the percentage of glycerol in a sample will but rarely be resorted to, the other processes yielding more accurate results in a shorter time. B. Chemical Methods If very dilute solutions of chemically pure glycerin have to be examined the physical methods lose in accuracy, and it is preferable to resort to chemical methods. Oxidation of Glycerol.—The methods falling under this heading have been fully described p. 207. As only the minutest traces of organic impurities are present in a chemically pure glycerin, all those processes will yield accurate results. Of concentrated glycerins, 0 - 2 to 0'4 grms. are weighed off; of dilute solutions, of course, more is taken. Benedikt and Zsigmondy state that, when employing their process (p. 208), the proportion of glycerol in a solution containing but 0'03 per cent can be estimated with accuracy to 00003 per cent. Moraivski 1 bases a method of determining glycerol on its property of combining with lead oxide to form monoplumbo-glyceroxide (p. 79). 50-60 grms. of litharge are weighed into a large crucible together with a short glass rod, then about 2 grms. of the sample are added, and enough alcohol to facilitate the thorough mixing of the glycerin with the litharge. The crucible is heated at first in a vacuum water- oven, and then to 120°-130° C. in an air-bath, being covered with a watch-glass having an aperture for the glass rod, until the weight becomes constant. The increase in weight multiplied by T2432 no : CyigO = 92:74; — = T2432) gives the amount of glycerol in the sample. This process cannot be considered satisfactory when compared with the oxidation method. Lewkowitsch 2 has shown that errors up to 10 per cent may occur. If the litharge contains “red lead,” or has had an opportunity of absorbing carbonic dioxide from the atmosphere, the results become inaccurate, Even Morawski’s own results show a mean difference of 0'6 per cent, in maximo 1'5 per cent. The necessity of preventing contact with the atmosphere during the drying, which takes three to four hours, renders this method inconvenient. Also Muteds 3 process, based on the solubility of copper oxide in glycerol; Biez’s^ method, based on the conversion of the glycerol in the sample into its benzoate; and Boulez’s process, based on the con¬ version of glycerol into calcium glycero-phosphate,—are not accurate enough to deserve further notice here. 1 Jour. Soc. Ohem. Ind. 1889, 424. 2 Chem. Zeit. 1889, 94. a Analyst, 1881, 41. 4 Jour Soc. Chem. Ind. 1887, 609. 3 F 802 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. 2. Dynamite Glycerin—Distilled Glycerin. Dynamite glycerin is a distilled glycerin, chiefly used in the manu¬ facture of high explosives having nitroglycerin as a basis or contain¬ ing it as an ingredient. Being a product obtained by distillation, it contains a very small amount of ash only, and is hereby easily distinguished from crude glycerin. It is further differentiated from it by not giving a pre¬ cipitate with lead acetate. The best brands of dynamite glycerin approach in purity chemically pure glycerin; they differ from it in colour, being yellowish to straw coloured, and also in the somewhat larger amount of ash and organic impurities which is permissible. The conditions dynamite glycerin should fulfil are, in consequence of the risks to which the manufacturer of dynamite is exposed if the glycerin be impure, usually laid down in contracts between buyer and seller. Thus the following points are stipulated :— Specific Gravity. —This should be not less than T261 at lS’S 0 C. For its determination see p. 793. This is a very important test, as high percentage of gtycerol found by the bichromate method may be caused by presence of trimethylene-glycol, detected in a sample of commercial glycerin by Noyes and Watkin. 1 Presence of trimethylene- glycol may be suspected if low specific gravity is combined with apparently high percentage of glycerin. 2 Lime, Magnesia, and Alumina should be absent. Chlorine. —Only traces are permissible; the glycerin must not become milky by silver nitrate. Arsenic. —Only minute traces are tolerated. The test is made by making the glycerin just alkaline with a minute quantity of ammonia, and adding silver nitrate. No yellow precipitate must appear. This precipitate being soluble in ammonia, an excess of this reagent must be avoided. Of course, Gutzeit’s reaction (see p. 787), using mercuric chloride, may also be employed. Organic Impurities. —Tested with silver nitrate, the glycerin must not become brown or black within ten minutes. Total Residue. —This is determined as described p. 789. It must not exceed 025 per cent. Free Acids. —The glycerin should not be acid to litmus, nor should it contain fatty acid; cp. Test for Volatile Fatty Acids, p. 788. On passing nitrous acid fumes through it, it should not curdle ; it is supposed that oleic acid would thus be detected. 1 Jour. Soc. Chem. Ind. 1896, 207. 2 Barton, ibid. 1895, 516, proposes to heat the glycerin to 225°-230° C. for 2 hours, and then again to take the specific gravity, which he terms “permanent specific gravity.” Barton assumes that hydrocarbons are volatilised, hut their occurrence is more than doubtful except in glycerins from bone fat. The “permanent specific gravity” will always he higher than the specific gravity of the sample, as the last traces of water volatilise ; also trimetliylene-glycol (boiling point 214°-217°) will most likely be driven off. XII DYNAMITE GLYCERIN 803 Nitration and Separation Test .—A sample of glycerin may prove good in all preceding tests, and yet be totally unfit for the manu¬ facture of nitroglycerin. The suitability of a sample of dynamite glycerin must therefore be determined by the following process, simulating the operations on a manufacturing scale :— 375 grms. of a mixture, consisting • of one part (by weight) of nitric acid, specific gravity 1-5, and two parts (by weight) of sulphuric acid, specific gravity 1*845, previously cooled down to the ordinary temperature in a closed vessel, are weighed off in a beaker of about 500 c.c. capacity. A thermometer, used during the nitration as a stin ei, is then introduced into the acid, and the beaker immersed in a capacious vessel filled with cold water, or, if necessary, with ice. A stream of cold water is kept running through the vessel by means of a stout india-rubber tubing, say f" diameter, coiled at the bottom of the vessel. It is very important that the india-rubber tubing should be securely fastened to the water-tap, if the latter be near the operator, as it may easily happen that the tube is thrown off the tap by the pressure of the water in the pipe, when any water accidentally coming into contact with the acid may raise the temperature to such a point that explosion will ensue. The writer uses, therefore, thin-walled beakers, so that they may be rapidly broken in case the temperature rises to a point of danger; the rapid discharge of the mixed acids and nitroglycerin into the large mass of water will then effectively prevent an explosion. When the temperature of the acids has fallen to about 12° to 15° C. 50 grms. of the sample of glycerin, weighed off in a beaker having a spout, are allowed to fall into the acids, drop by drop, constantly stirring with the thermometer, and observing the temperature after the addition of every single drop of glycerin. Considering the danger attending this operation, the inexperienced analyst had perhaps best be shown the test by an experienced operator. If this be not feasible, the safest plan will be to proceed in the manner described, i.e. add cautiously drop by drop, stirring all the while, so that no overheating may take place locally , and never allowing the temperature to exceed 30 C. No addition of another drop of glycerin must be made until the temperature has fallen below 25° C. (An experienced operator will, of course, proceed a little more rapidly.) If all the glycerin has been dropped in in this manner, the mixture is stirred for a short period, until the temperature has fallen to about 15° C., and transferred to a separating funnel, which must be absolutely dry. The safest plan is to have the funnel rinsed out beforehand with concentrated sulphuric acid. If the dynamite glycerin is good, the nitroglycerin will rapidly i ise to the top and separate in a few minutes as an oily, somewhat turbid layer on the top of the spent acids. The quicker the separation into two well-defined layers takes place the better is the glycerin. If flocculent matter is noticeable in the nitroglycerin layer, if the separa¬ tion is slow, and an intermediate layer of this flocculent substance renders the line of separation indistinct, the sample is unsuitable for 804 TECHNICAL AND COMMERCIAL ANALYSIS chap. dynamite making. In some cases the time of separation cannot be stated, owing to the nitroglycerin being honeycombed with this fiocculent substance, requiring hours for separation. Such a sample must of course be rejected. The quantitative determination of the yield of nitroglycerin is con¬ veniently combined with this nitration test. In that case the accurate quantity of glycerin used is either determined by re-weighing the beaker containing the glycerin, or the beaker is rinsed out with the mixture of acids and nitroglycerin. The former method is the better. After separation of the nitroglycerin the acid layer is carefully drawn off, and the nitroglycerin slightly agitated without shaking, so that any drops of acid adhering to the vessel are brought into one mass. This is carefully drawn off, and the nitroglycerin washed with water of 35°-40° C. once, then once or twice with a 20 per cent solution of sodium carbonate, and then again with water. The nitroglycerin is then transferred to a suitable burette, in which the adhering water rises to the top. The volume is read off, and the quantity determined by multiplying the number of c.c. by T6, the specific gravity of nitroglycerin (the specific gravity of the product may be determined, if desired), or by weighing the product after separation from water by filtering over salt. It is evident that this process yields only approximate results, especially so as nitroglycerol is slightly soluble in Avater. The method is, however, satisfactory for the commercial valuation of dynamite glycerin. The yield of nitroglycerin should be at least from 207-210 per cent of the glycerin weighed off, the more the better. The quantity of nitroglycerin contained in the washings (recovered on the large scale by the so-called after-separation) is disregarded. The theoretical yield of nitroglycerol from glycerol is 246'7 per cent. It is, of course, necessary to destroy the nitroglycerin. This is done best by spreading out a sufficient quantity of dry sawdust in not too thick a layer in an open space (say in the yard and not too near the wall of buildings), and running the nitroglycerin out of a separating funnel on to it whilst the operator carries it along the saw¬ dust, so as to distribute the nitroglycerin in a slender continuous trail, taking care that no pool is formed. By applying a lighted match to one end of the trail the nitroglycerin will burn away quietly. - The waste acids should be destroyed in a similar manner; when they are brought into contact Avith saAvdust a violent reaction sets in, but there is no danger if the nitroglycerin has been separated off carefully. The glycerol in the sample of dynamite glycerin may also be determined by oxidation, see p. 208. The results are, of course, not so accurate as in the case of chemically pure glycerin. Distilled glycerin is used for various purposes in the arts. The proportion of glycerin in a sample is usually determined with sufficient accuracy by taking its specific gravity and referring to the tables pp. 791, 795, 796. XII CRUDE GLYCERIN 805 3. Crude Glycerin The composition of commercial crude glycerins varies considerably with, the process of saponification from which it originates. In commerce the following three qualities are discerned:— 1. Crude Saponification Glycerin. —This is prepared by concentrating the “ sweet water ” obtained in the saponification by lime (p. 745) or water (p. 746). This crude glycerin usually contains about 0‘5 per cent of ash and small quantities of organic impurities. Its colour varies from yellow to dark brown ; its taste is sweet. Tested with basic lead acetate it gives but a slight precipitate; on addition of hydrochloric acid to good samples no turbidity appears. It is usually concentrated in the candle-works to T240-T242 specific gravity, and sold as “saponification glycerin,” 28° Be.; it contains about 90 per cent of glycerol. By refining with charcoal the “ refined ” glycerin is obtained. If the lime has been precipitated by oxalic acid, the excess of the latter will be found in the glycerin. 2. Distillation Glycerin. —This glycerin is recovered from the acid waters of the sulphuric acid saponification process (p. 746). The amount of ash is higher than that of saponification glycerin, some¬ times as much as 3 '5 per cent, and the organic impurities also reach several per cents. Its colour is usually pale yellow; its taste is sharp and astringent, and it emits an unpleasant smell when rubbed between the hands. Tested with basic lead acetate a voluminous precipitate is obtained; on addition of hydrochloric acid a turbidity, due to fatty acids, appears. The specific gravity is the same as that of the saponification glycerin ; it contains, as a rule, from 84 to 86 per cent of glycerol. It is sold as distillation glycerin, 28° B6. 3. Soap-lye Glycerin. —This glycerin is obtained on purifying the soap-maker’s spent lyes, and concentrating to the specific gravity of 1*3. It contains about 10 per cent of ash, chiefly common salt, if pure; if impure, sodium carbonate, caustic soda, sodium sulphide, sodium thiocyanate, and sodium thiosulphate are also present. The proportion of organic impurities in soap-lye glycerin varies consider¬ ably, depending on the process of purification used, etc. Some com¬ mercial glycerins contain less than 2 per cent of organic impurities, thus representing a crude glycerin of better quality than distillation glycerin; others, again, contain large quantities of impurities, con¬ sisting of fatty acids, resin acids, and albuminoid substances, gelatin, and hydrocarbons (from bone fat). Its colour is pale yellow to brown or almost black, according to the purity. The taste of good samples is sweet, qualified, of course, by the proportion of salt in the sample ; impure samples have a most unpleasant, garlic-like taste, although sulphides may be absent. Good soap-lye glycerin should have a specific gravity T3, and contain 80-82 per cent of glycerol and 10 per cent of ash. It should not become turbid on addition of hydrochloric acid. 806 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. Soap-lye glycerin can, therefore, be rapidly distinguished from saponification and distillation glycerin by the large proportion of common salt (heavy precipitate with silver nitrate), and by its high specific gravity ; saponification and distillation glycerins are differ¬ entiated by the lead acetate, the hydrochloric acid, and the organic residue tests. COMMERCIAL ANALYSIS OF CRUDE GLYCERIN (a) Estimation of Glycerol. — The crude glycerin is valued on the proportion of glycerol in the sample, allowance having been made for the difference in quality due to the different origin of the sample. The best methods for the quantitative estimation are Benedikt and Cantor's 1 “ Acetin method” and Hehner's 2 “Bichromate method.” Benedikt and Zsigmondy's permanganate process (p. 208) does not yield reliable results in this case owing, no doubt, to the presence of organic impurities yielding oxalic acid on oxidation, even if the bulk of the organic impurities be first removed by diluting the sample and precipitating with lead acetate. Morawski's method (p. 801) is in this case useless, as also are the other methods men¬ tioned, p. 801. Acetin Method. —This process is based on the quantitative con¬ version of glycerol into triacetin (p. 3), when concentrated glycerin is heated with acetic anhydride. If the product of this reaction is then dissolved in water, and the free acetic acid has been carefully neutralised with alkali, the dissolved triacetin can be easily estimated by saponifying with a known volume of standard alkali and titrating back the excess. The solutions required are— 1. Half-normal or normal hydrochloric acid ( accurately standard¬ ised). 2. Dilute caustic soda, containing about 20 grms. of NaOH in 1000 c.c. Its strength need not be known accurately. 3. A 10 per cent solution of caustic soda. Solutions 2 and 3 are best kept in large bottles connected by means of syphon tubes with burettes, so that the filling of the latter may take place auto¬ matically. To prevent absorption of carbon dioxide from the air the bottles are provided with soda-lime tubes through which the air has to pass. The estimation of the glycerol is carried out as follows :— About 1‘5 grms. of the crude glycerin weighed off accurately are heated with 7-8 c.c. of acetic anhydride and 3 grms. of anhydrous sodium acetate (dried previously in an oven) for 1-| hours in a round- bottomed flask, of about 100 c.c. capacity, connected with an inverted condenser. The mixture is then allowed to cool a little, 50 c.c. of 1 Jour. Soc. Chem. Ind. 1888, 696 ; cp. also Lewkowitsch, ibid. 1889, 574 ; Chem. Zeit. 1889, 13, 93, 191, 659. 2 Jour. Soc. Chem. Ind. 1889, 6 ; cp. also Bordas and Raczkowski, ibid. 1897, 167. XII CRUDE GLYCERIN 807 warm water are poured down through the tube of the condenser, and the acetin made to dissolve by shaking the flask; if necessary, the contents of the flask may be slightly warmed, but must not be boiled. 1 These operations must be done with the condenser, as triacetin is volatile with water vapours. The solution is next filtered from a flocculent precipitate, containing most of the impurities of the sample, into a wide-mouthed flask of about 500-600 c.c. capacity, and the filtrate allowed to cool down to the ordinary temperature. Phenol- phthalein is then added, and the free acetic acid neutralised with the dilute caustic soda solution. Whilst running in the soda the solution must be agitated continually, so that the alkali may not be in excess locally longer than is unavoidable. The point of neutrality is reached when the slightly yellowish colour of the solution just changes into reddish-yellow. If the solution is allowed to become pink, the point of neutrality has been exceeded, and the test must be started afresh ; the excess of soda cannot be titrated back, as partial saponification of the acetin takes place in presence of the slightest excess of alkali. The change of colour is very characteristic, and is easily noticed after some little practice. 25 c.c. of the strong soda solution are now run in and the solution boiled for a quarter of an hour. The excess of soda is then titrated back with the standard acid. Side by side with it, operating in the same manner, 25 c.c. of the caustic soda are boiled and titrated with acid. The difference between the two titrations corresponds to the amount of alkali required for the saponification of the triacetin. From this the quantity of glycerol in the sample can be calculated, as shown in the following example :—Suppose L324 grms. of the sample have been treated as described above. Let 25 c.c. of the strong alkali require 60"5 c.c. of normal hydrochloric acid, and let the number of c.c. required for titrating back the excess of soda in the sample be 2L5 c.c., then 60-5 - 2L5 = 39-0 c.c. have been used. 1 c.c. of normal acid corresponds to 0-092 3 0-03067 grms. of glycerol. Hence the sample contained 0-03067 x 39 = 1-1960 grms. or 90 - 3 per cent of glycerol. Bichromate Method. —About 1 *5 grms. of crude glycerin are weighed off in a 100 c.c. flask, and silver oxide added to precipitate any chlorine (present in the sample as sodium chloride), and to oxidise aldehydes. A little water is then run in and the mixture allowed to stand for ten minutes. Basic lead acetate is added next in slight excess, and the volume made up to 100 c.c. A portion of the solution is filtered through a dry filter, and 25 c.c. of it placed in a beaker previously cleaned with concentrated sulphuric acid and bichromate solution, so as to remove traces of adhering fat. Then proceed as described page 212. As the bichromate solution is necessarily a strong one, the measuring must be done with the greatest care. Attention must also be paid to the temperature of the solution at the time of measuring. 1 Hehner, Jour. Soc. Chem. Ind. 1889, 6. 808 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. Hehner states that the strong bichromate solution expands 0 - 05 per cent for each degree C. The writer obviates corrections by bringing the standard solutions to the normal temperature in a large water- bath, and keeping thereat until the titration is finished. Hehner has shown by a number of comparative experiments, using both the acetin and the bichromate processes, that the results agree very well. This has been borne out by a large number of experiments made by the writer. Hehner advises to use both methods in the examination of a sample, and to take the mean of the two results. This, however, entails too much unnecessary work in com¬ mercial analysis, and it will therefore be preferable to make two tests by the acetin method. (b) Specific Gravity. —This is taken as described page 793. Saponification and distillation glycerin should have a density of T240-T242 ; soap-lye glycerin of T3. (c) Ash. —3-5 grms. of the sample are weighed off accurately in a platinum dish, and the glycerol burnt away. This determination may be combined with that of the organic impurities, except, per¬ haps, in the case of soap-lye glycerin, when it will be found preferable to make two separate determinations. The platinum dish is placed over a small burner, which must not touch its bottom, and the glycerol allowed to evaporate off slowly. More heat should only be applied after the bulk of the glycerol has been driven off. In the case of soap-lye glycerin a bulky carbon¬ aceous residue is obtained, which is heated high enough to just destroy the organic matter. After cooling, the charred mass is ex¬ hausted with water and transferred to a filter, the filtrate boiled down in the platinum dish on the water-bath, the residue, which must be white, heated (not above 400° C. to avoid loss by volatilisation of sodium chloride), and weighed. The carbon on the filter may as a rule be disregarded. Vizern 1 recommends to ignite also the carbon; this may be necessary if the sample contains large proportions of lime. H. D. Richmond 2 estimates the ash by carbonising, as described above, adding a little concentrated sulphuric acid, and heating over a good Bunsen flame until the ash is burnt white. The “ sulphated ” ash is then multiplied by 0'8. This method is less accurate, and cannot be recommended. (d) Organic Impurities. —They are determined as described page 789. In the case of soap-lye glycerin, the drying at 160° C., until constant weight is obtained, requires a somewhat long time. The process is shortened by adding to the residue occasionally a few drops of water. (e) Fatty acids are detected by acidifying the sample, after diluting with three measures of water, with hydrochloric acid. (/) Arsenic is tested for as described pages 787, 802. If a soap-lye glycerin contains considerable quantities of sulphides, thiosulphates, or sulphites, it is almost valueless to the refiner. The 1 Jour. Chem. Soc. 1890, Abstr. 835. 2 Jour. Soc. Chem. Ind. 1889, 7. XII CRUDE GLYCERIN 809 detection of these impurities is, therefore, of great importance for purposes of valuation. According to Ferrier, 1 50 grms. of the sample are conveniently made up to 500 c.c., and the solution tested for sulphides with paper saturated with alkaline lead nitrate solution. To detect traces of sulphides down to T ooooo th part, a few c.c. of the solution are placed in a small flask, four or five drops of hydro¬ chloric acid added, as well as a pinch of sodium bicarbonate, the liquid heated carefully to boiling, and a paper moistened with alka¬ line lead nitrate held over the flask. Hyposulphites and sulphites are detected by treating a sample of the solution with a few c.c. of a solution of barium chloride, and filtering off the precipitate containing carbonate, sulphate, and sul¬ phite. As soon as the filtrate has been obtained clear, if necessary by repeated filtrations, two or three drops of hydrochloric acid and a few drops of a potassium permanganate solution are added. If the glycerin contains even less than P ar f °f thiosulphate, a dis¬ tinct turbidity is produced. The detection of the sulphites is effected by washing the precipitate on the filter with boiling water, stirring it up with a little water, and adding to this mixture a little starch solution and a few drops of iodine solution. In the presence of sulphites the blue colouration disappears with more or less rapidity, whilst in their absence the blue colour is permanent. The process given by Ferrier for the quantitative determination is not accurate, and need therefore not be referred to here. 2 The residues from the distillation of glycerin are used in the manufacture of shoe-blacking. They contain large proportions of ash and polyglycerols. The proportion of glycerol is best determined by the acetin method. 3 The valuation of soap-maker’s spent lyes is made on the basis of the proportion of glycerol they contain, provided sulphur com¬ pounds are absent. For the estimation of glycerol 1000 c.c. are heated to boiling and acidified with hydrochloric acid, when any fatty acids, etc., separate as an oily liquid on the top. This is filtered off, the filtrate made neutral, and lead acetate added. The precipitate is filtered oft and the clear solution boiled down. The salt separating out is fished out and sucked dry by means of a filter-pump. When a few c.c. of solution are left finally, this is added to the salt, and the latter exhausted with a mixture of three measures of methylated spirit and one measure of ether. The alcoholic filtrate is evaporated down on 1 Jour. Soc. Chem. Ind. 1893, 471. 2 Cp. Richardson and Aykroyd, Jour. Soc. Chem. Ind. 1896, 171. 3 Lewkowitsch, Jour. Soc. Chem. Ind. 1890, 479. 810 TECHNICAL AND COMMERCIAL ANALYSIS CHAP. XII the water-bath, and the crude glycerin thus obtained examined by the acetin method. If but small quantities of soap-lye are available, so many grams are weighed off in a 100 c.c. flask as will approximately correspond to 1*2 grms. of pure glycerol, and the glycerol is then determined by Helmer’s bichromate method (p. 807). CHAPTER XIII EXAMPLES 1 The manner in which the methods described in the preceding chap¬ ters can be employed in the examination of technical products may be illustrated by the following examples:— 1. Tournant Oil (Turkey-red Oil) An oil sold as Tournant Turkey-red oil gave on examination the following results :— Specific gravity at 17"5° C. . . . 0’933 Acid value . . . . . 54 "9 Saponification value . . . . 186 - 4 Iodine value . . . . 90‘5 Acetyl value . . . . 54-9 The high acetyl value, the high specific gravity, the high iodine value, and the low saponification value, point unmistakably to the presence of castor oil. Taking the acetyl value of castor oil as 153, the oil contains approximately an amount of „ 54-9x100 Castor oil =-—— = 36 per cent. The nitric acid test revealed the presence of cotton seed oil. Assum¬ ing that the sample contained, besides castor oil, some true Turkey- red oil, or a mixture of olive oil and oleic acid, all of which absorb about 83 per cent of iodine, then the proportion of cotton seed oil may be calculated according to the formula given p. 311, the iodine value of cotton seed oil being taken as 108. n .. , ., 100 (J-») 100 (90-5-83) Cotton seed oil=- -= ————- = 30 per cent. m-n 108-83 r 1 Cp. also the examples given pp. 149, 152, 165. 812 EXAMPLES CHAP. As the acid value of oleic acid is 199 (p. 150), the acid value of the sample, 54 - 9, will correspond to about 27‘6 per cent of free oleic acid. Consequently the oil cannot contain more than about 6‘4 per cent [100 - (36 + 30 + 27*6)] of neutral fat due to true Tournant oil. Tournant oil contains, however, about 26 per cent of free fatty acids (p. 464); therefore about 1‘6 per cent of free fatty acids must be added to the amount of neutral oil, and, of course, deducted from the amount of free oleic acid. Accordingly, an oil exactly similar to the sample could be prepared by mixing the following fatty substances in the proportions stated :— Per cent. Castor oil ... 36 Cotton seed oil . 30 Tournant oil 8 Commercial oleic acid . 26 100 2. Commercial Acetine See p. 677. 3. Composition of Butter Fat See p. 607. 4. Product obtained by the action of Zinc Chloride on Oleic Acid Oleic acid may be converted by v. Schmidt’s process (p. 747) into a solid substance. A sample 1 was prepared in the laboratory by heating 500 grms. of oleic acid with 50 grms. of zinc chloride to exactly 185° C. in an oil-bath, until a drop of the mixture, after boiling with hydrochloric acid, solidified on cooling. The contents of the flask were then decomposed with hydrochloric acid, and the fatty substance purified by repeatedly boiling out with water. (a) Crude Product The fatty substance thus prepared had the consistency of lard; on examination it gave the following constants :— Acid value ...... 124'9 Saponification value .... 179‘7 Ether value . . . . . . 54‘8 Constant acid value ..... 125'7 1 Benedikt, Monatshefte /. Chemie, 1890, 71 ; Jour. Soc. Chem. Ind. 1890, 658. XIII ACTION OF ZINC CHLORIDE ON OLEIC ACID 813 Constant saponification value . . . 180'8 Constant ether value . . . 55 *1 Acetyl acid value . . . . . 114 ■ 9 Acetyl saponification value . . . 201 '0 Acetyl value . . . . 86 T Iodine value . . . . 36‘0 From these numbers the following conclusions may be drawn ;— The acid value of the sample is considerably lower than that of the original oleic acid (198'6); therefore a portion of the oleic acid has either been polymerised or has been converted into anhydrides. The definite ether value, found by the difference of the saponifica¬ tion and acid values, points to the presence of saponifiable anhydrides. Still, the saponification value, 179*7, is too low for a mixture of monobasic fatty acids, containing no more than 18 atoms of carbon in the molecule, and of anhydrides of the same order. We must, therefore, conclude that either polymerisation has taken place or that unsaponifiable anhydrides have been formed. For the determination of unsaponifiable anhydrides 100 grms. of the sample were dissolved in alcohol and boiled with 40 grms. of caustic soda previously dissolved in a little water. The soap solution was then shaken out with petroleum ether, the ethereal solution washed with water, the solvent distilled off, and the residue dried, at first on the water-bath, being repeatedly moistened with alcohol, and finally at 105° C. in a drying oven. Thus 8 grms. of substance, equal to 8 per cent, were obtained. This anhydride could only be saponified by alcoholic potash at 150° C., and may, therefore, for practical pur¬ poses be considered as unsaponifiable. It is a yellow viscous liquid insoluble in alcohol. It absorbs no iodine, and has neither an acid nor a saponification value. The constant ether value (p. 206) points distinctly to the presence of that class of anhydrides which are converted by alkalis into the potassium salts of the corresponding acids, but are re-formed when¬ ever-the salts are decomposed by an acid. This easily saponifiable anhydride was isolated from the soap solution after extracting the unsaponifiable liquid anhydride with petroleum ether in the following manner :—The solution was diluted with hot water, acidulated with hydrochloric acid, and boiled down on the water-bath until the alcohol was evaporated off. The oily layer floating on the top (corresponding to 100 grms. of the sample) was separated from the aqueous layer and neutralised most carefully with caustic soda in the manner described (p. 207), as the slightest excess of alkali was liable to saponify a portion of the anhydride, and thus vitiate its quantitative determination. By extraction with petroleum ether 28 grms. of a white crystalline substance were obtained, forming curved needles (from dilute alcohol), melting point 5T2° C. The substance absorbed no iodine, its acid value was nil, and its saponification value was 199. The crystals were therefore identical with the stearoladone described by Geitel (p. 69), a conclusion 814 EXAMPLES CHAP. which was further confirmed by the numbers furnished by ultimate analysis. The quantitative composition of the product of the interaction of zinc chloride and oleic acid can now be calculated in the following manner :— The constant ether value being identical with the ordinary ether value , anhydrides of the type of acetic anhydride ( i.e . anhydrides saponifiable by alkalis and not re-formed on acidifying) are absent. Since the ether value of pure stearolactone (according to theory) is 198*9, the amount of stearolactone in the sample can be calculated from the constant ether value of the sample, viz. 55T, using the pro¬ portion 198 - 9 : 100 :: 55T : x; hence x — 27'7 per cent, or rot. 28 per cent. This number agrees perfectly with that found by direct deter¬ mination (comp, above). From the iodine value of the sample the proportion of oleic acid— oleic plus isooleic acid—is found. Pure oleic acids absorb, according to theory, 90'07 per cent of iodine; consequently the iodine value, 36, of the sample corresponds to 40 per cent of oleic acids. The true acetyl value of the sample is found by subtracting the constant ether value, 55T, from the above given acetyl value, 86T ; it equals 86T-55T = 31’0. From this acetyl value the proportion of /3-hydroxystearic acid, molecular weight =300, can be found by substituting in the equation (p. 205)— 100. c. M. (M + 42) 56100(M - 42) for c and M, 31 and 300 respectively. Hence cc = 21*97, or about 22. The product of the interaction of zinc chloride and oleic acid has, therefore, the following composition :— Liquid anhydride Per cent. 8 Stearolactone .... . 28 Oleic acids .... 40 /3-Hydroxy stearic acid . 22 Saturated fatty acids (by difference) 2 100 That there is a small amount of saturated fatty acids (other than hydroxy acids) present may be proved by means of the saponification values in the following manner :— 40 per cent of oleic acid correspond to the acid value 79'6 22 ,, „ /3-hydroxystearic acid ,, ,, 41’1 1207 The acid value of the sample having been found = 124'9, the differ¬ ence, 124-9 - 120-7 = 4-2, must be accounted for by the presence of saturated acids. This conclusion is further supported by the behaviour of oleic acid when heated with zinc chloride to 200° C. XIII ACTION OF ZINC CHLORIDE ON OLEIC ACID 815 (b) Crude distilled Product The crude product (a) was distilled under diminished pressure, and the distillate, after washing with water, examined, when the following numbers were obtained :— Acid value ...... 126'3 Saponification value. .... 188T Ether value . . . . . 61'8 Acetyl acid value . . . . . 127'0 Acetyl saponification value . . . . 189 - 0 Acetyl value . . . . . 62 - 0 Iodine value. . . . . . 47T Unsaponifiable ..... 13-6 per cent. The proportion of “ unsaponifiable ” was determined, on the one hand, in a direct way, by extracting the alcoholic solution of the soap with petroleum ether and weighing the residue, and, on the other hand, by difference, the extracted soap having been decomposed with acid and the separated fatty mass weighed. The unsaponifiable portion forms a mobile, light yellow oil, consist¬ ing chiefly of hydrocarbons, with which small quantities of oxygenated substances are admixed, as proved by ultimate analysis :—C = 84TO per cent; H= 13T0 per cent; 0 = 2-20 per cent. The iodine value of the unsaponifiable matter was 74 T. The composition of the crude distillate may now be inferred as follows :— The ether value, 61-8, corresponds to 31 per cent of stearoladone. The ether value being identical with the acetyl value, hydroxy acids must be absent. Iodine is absorbed both by the “ unsaponifiable ” and the oleic acids. The 13'6 per cent of unsaponifiable—iodine value 74T—require 10'08 per cent of iodine. Consequently there are left for the oleic acids 47*1 - 10-08 = 37‘02 per cent of iodine. This corresponds to 41T3 per cent of oleic acids. Hence we find the crude distilled product to have the following percentage composition:— Per cent. Unsaponifiable 13-6 Stearolactone .... 31-0 Oleic and isooleic acids 41-1 Saturated acids (by difference) 14-3 ioo-o Also in this case presence of saturated acids is indicated by the saponification value of the distillate, the number 126-3 being con¬ siderably higher than that required for 41-1 per cent of oleic acids, viz. about 82. 816 EXAMPLES CHAP. The changes the crude product (a) has undergone on being dis¬ tilled consist, therefore, in the decomposition of the liquid anhydride, and in the conversion of /Miydroxystearic acid into isooleic and oleic acids. (c) Solid Portion of the Distillate (Candle Material) The candle material obtained from the crude distillate (on the large scale by cold and hot pressing, in the laboratory by the use of unglazed porcelain) is a hard, crystalline mass, melting point 41°-42° C. It caused no grease-spot on paper, and contained only traces of liquid oleic acid. On examination the following numbers were obtained:— Acid value . . . . . 53 - 3 Saponification value ..... 204 '3 Ether value ...... 151'0 Acetyl saponification value .... 205 - 0 Iodine value . . . . . 14 - 0 From these data the following composition is calculated:— Per cent. Stearolactone .... 75-8 Isooleic acid .... 157 Saturated fatty acids. 8-5 100-0 5. “Recovered Grease” 1 (l Crude Wool Fat) In technical analysis the determination of the following constitu¬ ents of recovered grease would be required (cp. p. 687):— (a) Free fatty acids. ( b) Neutral fat. ( c ) Unsaponifiable matter. (a) Free Fatty Acids The amount of alkali required to saturate the free fatty acids in 1 grm. of the “recovered grease” was 0'71 c.c. normal KOH (acid value = 39'8). A larged weighed quantity of “recovered grease” was then nearly neutralised with the greater part of the alkali required, as calculated from the acid value, and then carefully titrated with half-normal alkali, until the solution became pink to phenolphthalein. A large proportion of neutral fat and unsaponifiable matter rose to the top as an oily layer, and was separated from the soap solution, 1 Lewkowitscli, Jour. Soc. Chem. Ind. 1892, 134 ; cp. also ibid. 1896, 14. XIII RECOVERED GREASE 817 after having been dissolved in ether. The remainder of the neutral fat and unsaponifiable matter was removed from the soap solution by- shaking out with ether. The ethereal solutions were united, freed from adhering soap by washing with water, and the solvent was then distilled off. Thus the neutral fat (b) and the unsaponifiable matter (c) were obtained together. Between the aqueous and the ethereal layers there appeared a flocculent stratum, which was found to consist of an insoluble soap. It was isolated by filtering off from the soap solution. The fatty acids of both the soap solution and the insoluble soap were separated in the usual manner by decomposing with a mineral acid. Thus the free fatty acids of the “recovered grease” were obtained in two fractions, viz. (1) acids, forming soluble soaps; (2) acids, forming in¬ soluble soaps. Both kinds of acids were found to contain inner anhydrides or lactones (increase of weight on boiling with acetic anhydride, cp. p. 206); for the determination of the molecular weight the acids had therefore to be boiled with standardised alcoholic potash. The molecular weights were found to be respectively 326 and 520. The proportion of the acids (1) to the acids (2) being 9:1, the mean molecular weight of all free fatty acids may be taken as— 9 x326 + 520 -To-= 345 ' The Reichert-Meissl value of the recovered grease was 6*2, or, in other words, 1 grm. required 0T24 c.c. normal KOH for saturation of the volatile fatty acids. Assuming as their mean molecular weight 102 (C 5 H 10 O 2 ), the “recovered grease” contains 10'2 x 0T24= l - 26 per cent of volatile acids. The insoluble free fatty acids in 1 grm. were saturated by 0-71-0T24 c.c. = 0-586 c.c. normal KOH. Their mean molecular weight being 345, we find 34'5 x 0-586 = 20-22 per cent of insoluble free fatty acids. (, b and c) Neutral Fat and Unsaponifiable Matter A somewhat large quantity of the substance (b) and (c), prepared as already described, was saponified, and the soap solution tested for glycerol. The negative result proved absence of glycerides. The neutral fat had, therefore, to be considered a wax. The ether residue obtained by extracting the saponified mass with ether, and evaporating off the latter, was completely dissolved by acetic anhydride, no oily layer separating on cooling (p. 230). There¬ fore, hydrocarbons were absent, and the unsaponifiable matter ( c ) could only consist of alcohols. The wax (b) was separated from the unsaponifiable matter (c) by judicious boiling out with alcohol, 1 in which the wax is almost in 1 Preferably acetic anhydride, cp. p. 230. 3 Cx 818 EXAMPLES CHAP. soluble. The latter was thus obtained as a viscous wax-like sub¬ stance, melting into a thick liquid at about 40° C. On saponification with double normal alcoholic potash under pressure (p. 23), 1 grm. of the wax was found to require T825 c.c. of normal KOH, or, in other words, its saponification value was 102-4. The alcohols (unsaponifiable) were determined in the usual manner by extracting the saponified mass with ether; the fatty acids were then estimated in the soap solution by Hehner’s method. Thus the composition of the wax was found in two analyses as follows:— i. II. Per cent. Per cent. Fatty acids 56-3 54-1 Alcohols 43-2 44-0 99-5 98-1 The sum of the constituents of the wax should have been higher than 100, several per cents of water being assimilated on saponifica¬ tion. The deficiency must be looked for in the number obtained for the fatty acids, this having been found too low, owing to the property of these acids of easily losing water on drying, with forma¬ tion of inner anhydrides or lactones. The molecular weight of these fatty acids was found to be 327'5 when using alcoholic potash for the determination, wherefrom the percentage composition of the wax may be calculated as follows :— Per cent. Fatty acids, 1'825 x 32‘75= . . . 5977 Alcohols (mean of values in Analyses I. and II.) . 43-60 103-37 The mean molecular weight of the alcohols calculated from the equa¬ tion „ 43-6x327-5 M= 59'77 was found to be 239. The fatty acids absorbed only 17 per cent of iodine; they consist, therefore, for the most part of saturated acids. (c) Unsaponifiable Matter The proportion of unsaponifiable matter was found approximately by analysing the mixture of ( b) and (c) in the same manner as (b), and comparing the numbers obtained as follows :— 1 grm. of the mixture of ( b ) and (c) required T73 c.c. of normal KOH on saponification. Its percentage composition was found as follows :— XIII RECOVERED GREASE 819 Fatty acids . . . . Alcohols . I. Per cent. 507 47-5 II. Per cent. 49-8 47-6 98-2 97-4 From these numbers we calculate— Fatty acids, 1-73 x32‘75 Alcohols .... Per cent. 56-66 47-55 104-21 The 56-66 parts of fatty acids require 41 -34 per cent of alcohols, mean molecular weight 239, to form wax. Consequently there are present in the “recovered grease” 47‘55 - 4D34 = 6*21 per cent of unsaponifiable matter. The composition of the “ recovered grease ” is therefore— Per cent. Volatile fatty acids . 1-26 Insoluble free fatty acids . 20-22 Unsaponifiable matter (uncombined alcohols) 6-21 Wax (wool fat) by difference . . 72-31 100-00 To check the result the sum of the alcohols and of the wax could have been determined direct. The number 72-31 for wax can be resolved, with the help of its above-given percentage composition (fatty acids, 59'77 per cent; alcohols, 43'60 per cent), into two numbers expressing its component parts, viz. 72-31 x 0-5977 = 41-81 per cent of fatty acids, and 72*31 x 0-436 = 30-5 per cent of alcohols. The total unsaponifiable matter obtainable from the “ recovered grease ” on complete saponifi¬ cation is, therefore, 30"5 + 6*21 = 36*71 per cent. Hence we express the analytical result as follows :— Per cent. Volatile fatty acids . . . . l - 26 Insoluble free fatty acids . . . 20‘22 Unsaponifiable matter (uncombined alcohols) 6 - 21 \ Wax / Combined alcohols . . . 30-50 f \Combined fatty acids . . . 41-81 Total unsaponifi- able matter. 36-71 The percentage of the total unsaponifiable matter —36*71—can, of course, be verified by direct determination, which can be suitably combined with that of the saponification value. Direct experiment gave the number 36*47 (see below). A more rapid, and for technical purposes sufficiently accurate, method would be to determine the acid value, the saponification value 820 EXAMPLES CHAP. (the ether value by difference), the proportion of total unsaponifiable matter, the mean molecular weight of the total insoluble acidsf and, if required, the Reichert-Meissl value. The following numbers were thus obtained :— 1 grm. required for the saturation of the volatile acids . 0T24 c.c.ofnormalKOH 1 ,, ,, ,, ,, ,, free insoluble acids 0*586 c.c. ,, ,, 1 ,, ,, ,, ,, ,, total insoluble acids . . 2*19 c.c. ,, ,, 1 ,, ,, ,, ,, ,, combined insoluble acids (by difference) 1*48 c.c. ,, ,, Mean molecular weight of the total insoluble acids . . 332 2 Unsaponifiable matter .... . 36'47 per cent. From these analytical data we obtain :—The percentage of the free insoluble acids, 0*586 x 33*2 = 19*45 ; the percentage of the combined fatty acids, as hydrated acids, 1*48 x 33*2 = 49*13; and the per¬ centage of volatile acids, 0*124 x 10*2 = 1*26 as before. In the following table these numbers are collated:— Per cent. Volatile fatty acids . . . . .1*26 Insoluble free fatty acids . . . .19*45 Combined fatty acids (as hydrated acids) . . 49*13 Total unsaponifiable matter . . . .36*47 106*31 Part of the surplus over 100 is due to the proportion of water assimilated on saponification; the remainder is due to an error in the number found for the molecular weight of the total insoluble fatty acids, caused by the difficulty of titrating accurately the dark alcoholic solutions. It would not have been permissible to determine the proportion of the total fatty acids by Hehner’s method, the result obviously coming out too low owing to the formation of inner anhydrides. 6. Distilled Grease 3 (Liquid Portion) The liquid portion of the distillate obtained on a large scale by subjecting the “recovered grease” to distillation gave on examination the following results :— 1 This must be determined with alcoholic potash (cp. above). 2 This number is somewhat too high, owing to the dark colour of the alcoholic solution of the fatty acids. 3 Lewkowitsch, Jour. Soc. Chan. Ind. 1892, 141. XIII DISTILLED GREASE 821 (a) 1 grm. required for the saturation of the free fatty acids . 1 , 92c.c. of normal KOH (&) 1 ,, ,, ,, ,, ,, total fatty acids on saponification . . . . . 2 TO c.c. ,, ,, (c) 1 grm. required therefore for the saturation of the com¬ bined fatty acids . . . . . 0T8 c.c. ,, ,, ( d ) Mean molecular weight of the total fatty acids 1 . 300 ’5 (e) Total unsaponifiable matter . . . . 38 - 8 per cent. From the numbers recorded under (c) and ( d) and ( e) the composi¬ tion of the distilled grease may be expressed thus:— 'Per cent. Fatty acids (as hydrated acids), 2T x30"05 . . 63T Total unsaponifiable matter . . . 38'8 101-9 The low number obtained for the combined fatty acids shows that the greater portion of the wax had been decomposed during distilla¬ tion. The free fatty acids were isolated as described p. 816; their mean molecular weight was 286 ; they may, therefore, be considered as consisting of a mixture of oleic, stearic, and palmitic acids, with a small proportion of higher fatty acids. The proportion of free fatty acids in the “distilled grease” was, therefore, l - 02 x 28"6 = 54‘91 per cent. The wax plus the unsaponifiable matter was isolated in the same manner as described p. 817. The separation of these two constituents was, however, impossible, the unsaponifiable matter being also in¬ soluble in alcohol. The mixture of the two substances was there¬ fore saponified, so as to isolate the fatty acids contained in the wax. They possessed the molecular weight 394, as determined by means of alcoholic potash. The proportion of combined fatty acids in the “ dis¬ tilled grease” was therefore (2T0 - 1‘92) x 3 9-4 = 7'09 per cent. The alcohol combined with the latter acids was contained in the total unsaponifiable matter. Its presence was proved, on the one hand, by boiling an accurately weighed portion with acetic anhydride, and ascertaining that an increase in weight had taken place; and, on the other hand, by isolating the alcohol from the total unsaponifiable matter by means of alcohol. Adopting the molecular weight for the alcohols that had been found (p. 818) for the combined alcohols in the “recovered grease,” we can calculate the proportion of alcohols from the equation 7-09x239 - 394 — = a:; hence x = 4*3. The amount of undecomposed wax in the “distilled grease” is, therefore, neglecting the small amount of water assimilated on saponi¬ fication, 7 - 09 + 4-3 = 11-39 per cent. 1 Determined with alcoholic potash. 822 EXAMPLES CHAP. XIII The remainder of the unsaponifiable matter, 38 - 8 - 4-3 = 34-5 per cent, consists of hydrocarbons formed in consequence of the free fatty acids and of the wax of the “ recovered grease ” having been decom¬ posed during distillation. The composition of the “distilled grease” is expressed by the following numbers:— Free fatty acids . Per cent. . 54-91 Combined fatty acids 7-09\ Undecomposed Combined alcohols 4-30J Wax. 11-39 Unsaponifiable matter (hydrocarbons) . 34-50 100-80 INDEX Abietic acid, 235, 236 Absolute iodine value, 195, 312 Absorption spectra, 113 Acetic acid, 42 Acetin, 3, 26 Acetine, 677 Acetyl value, 162 acid value, 163 saponification value, 163 Acid, acetic, 42 acrylic, 52 aldepalmitic, 24, 604 angelic, 53 arachidic, 49 asellic, 54, 279, 479 azelaic, 73 belienic, 49 behenolic, 60 brassidic, 59 butyric, 42 capric, 44 caproic, 43 caprylic, 44 carnaiibic, 50 cerotic, 50 cocceric, 64 crotonic, 176 crotonoleic, 26, 414 daturic, 47 dihydroxyasellic, 170 dihydroxybehenic, 71 p-diliydroxybehenic, 71 dihydroxyheptadecylic, 7 0 dihydroxyjecoleic, 70 dihydroxypalmitic, 70 dihydroxystearic, 66, 67, 70 p-dihydroxystearic, 70 dihydroxystearidic, 70 dihydroxystearo-sulphuric, 65 dihydroxytiglic, 69 diricinoleic, 65 doeglic, 59 elaeomargaric, 60 elseostearic, 60 elaidic, 57 erucic, 59 formic, 527 gaidic, 53 hexahydroxystearic, 72 hysenic, 50 Acid, hydroxyoleic, 55 hydroxystearic, 68 hypogseic, 53 isanic, 63 isobutylacetic, 43 isocetic, 45 isodihydroxybehenic, 71 isoerucic, 60 isolinolenic, 62 isolinusic, 72 isooleic, 57 isoricinoleic, 65 isotrihydroxystearic, 71 isovaleric, 43 jecoleic, 59, 279 jecoric, 62, 279 lanoceric, 66 lanopalmic, 63 lauric, 44 lignoceric, 49 linolenic, 62 linolic, 60, 144, 202 linusic, 72 lycopodic, 54 margaric, 47 medullic, 587 melissic, 50 millet oil, 61 moringic, 26 morrhuic, 481 myristic, 45 oleic, 54, 197, 201, 202, 765 p-oleic, 57 oxyoleic, 61 palmitic, 46, 199, 201 palmitolic, 60 pentadecylic, 76 pentaricinoleic, 728 physetoleic, 53 pimaric, 235 rapic, 58 ricinelaidic, 65 ricinic, 66 ricinisoleic, 64 ricinoleic, 64 rieinoleo-sulphuric, 725 salicylic, 616 sativic, 72, 142 stearic, 47, 198, 201 stearolic, 60 824 OILS, FATS, AND WAXES Acid, suberic, 73 sylvie, 235 tariric, 61 tetraliydroxystearic, 72 theobromic, 26, 527 therapic, 63, 279 tiglic, 53 tigliceric, 67 trihydroxystearic, 71 triricinoleic, 728 umbellulic, 27, 44, 508 Acid saponification, 746 Acid value, 148 Acids, acetic series, 42 acrylic series, 52 dibasic, 72 diliydroxylated, 66, 69 hexahydroxystearic, 72 hydroxylated, 63, 64, 68 linolenic series, 62 linolic series, 60 monohydroxylated, 68 oleic series, 52 ricinoleic series, 64 tetrahydroxylated, 72 trihydroxystearic, 71 Acorn oil, 434 Acrolein, 80 detection in glycerin, 788 Acrylic series, 52 Adeps lan8e, 689 Agnine, 689 Alcohol, carnaubyl, 74 ceryl, 75 cetyl, 74 cocceryl, 76 isoceryl, 75 lanolin, 76 melissyl, 75 myricyl, 75 octodecyl, 74 psyllostearyl, 76 Alcohol, detection in soap, 782 methylated, 20 purification of, 19 Alcohols, 73-86 aliphatic, 213 ally lie series, 75 aromatic series, 83 detection of, in unsaponifiable matter, 230 ethane series, 73 free, in waxes, 16 Aide-acids, 53 Aldepalmitic acid, 24, 604 Aliphatic alcohols, 73-82 alcohols, detection of, in unsaponifiable matter, 230 alcohols, determination of, 213 Allylic series of alcohols, 75 Almond oil, 435 Amyl stearate, 4 Angelic acid, 53 Anhydrides, inner, 206 Animal fats, 550 Animal oils, 468 distinction between, and vegetable oils, 317 waxes, 651 Aunatto, 614 Apricot kernel oil, 428 Arachidic acid, 49 Arachin, 5 Arachis oil, 441 Arctic sperm oil, 278, 647 Aromatic series of alcohols, 83 Asellic acid, 54, 279, 479 Aselline, 481 Azelaic acid, 73 Badger fat, 551 Baryta value, 159 Base oils, 13, 733 Basswood oil, 393 Baudouin’s test for sesame oil, 390 Becchi’s test for cotton seed oil, 382 Beechnut oil, 393 Beef marrow fat, 586 Beef tallow, 592 stearine in lard, 584 Beeswax, 655 Beeswax oil, 657 Behenic acid, 49 Behenolic acid, 60 Ben oil, 467 Bieber’s reagent, 439 Blackcock fat, 551 Black fish oil, 495 Black mustard oil, 407 Black oil, 693 Blown oils, 13, 733 Blubber oils, 278, 469, 490 Boiled (linseed) oil, 735 Boiling points of fatty acids, 30 Bone fat, 587 lime soaps in, 749 Borneo tallow, 533 Bottlenose oil, 647 Brassidic acid, 59 Brassidin, 5 Brazil nut oil, 395 Bromine, action on fats, 14 addition number, 169 substitution number, 169 thermal test, 300 value, 167 value of oils and liquid waxes, 307 value of solid fats, 329 Brown grease, 686 Brown substitutes, 742 Burning oils, 685 Butter, 604 adulteration of, 609 cacao (cocoa), 527 fat, 601 galam, 513 goa, 531 kokum, 531 mace, 523 mahwah, 511 INDEX 825 Butter, nutmeg, 523 oil, 609 phulwara, 511 shea, 513 substitutes, 679 vegetable, 541, 682 Butterine, 621, 678 Butyric acid, 42 Butyrin, 3 Butyro-refractometer, 116 in analysis of butter, 626 Cacao butter, 527 Californian nutmeg oil, 441 Cameline oil, 367 Candle material, 754 Candle nut oil, 362 Candles, 745 cerasin, 763 paraffin wax, 757 sperm, 756 stearine, 745 tallow, 745 wax, 755 Candle tar, 755 Capric acid, 44 Caprin, 44 Caproic acid, 43 Caproin, 607 Caprylic acid, 44 Caprylin, 607 Carapa oil, 509 Carbolic acid as solvent in the examination of oils, 274 Carbolic acid in soap, 783 Carnauba wax, 649 Carnatibic acid, 50 Carnaiibyl alcohol, 74 Castor oil, 420 oil group, 413 oil rubber substitute, 743 oil, soluble, 733 Celosia oil, 365 Cerasin, 765 candles, 763 detection in unsaponifiable matter, 230 Cerotic acid, 50 Cerotin, 5 Ceryl acetate, 75 alcohol, 75 cerotate, 15 palmitate, 15 Cetin, 15, 669 Cetyl acetate, 74 alcohol, 74 alcohol, quantitative determination, 230 benzoate, 74 palmitate, 15 stearate, 15 Ceylon oil, 538 Chamois fat, 551 Chaulmoogra oil, 508 Chemical constitution of fats, 2 constitution of waxes, 14 Chemical methods of examining fats and waxes, 137-216 methods of examining fatty oils and liquid waxes, 253, 277-318 methods of examining solid fats and waxes, 328 Cherry kernel oil, 426 laurel oil, 428 Chicken fat, 551 Chinese wax, 672 Chloride of sulphur, see Sulphur chloride Chlorine, action of, on fats, 13 colour reactions, 316 estimation of, in fats, 97 Cholesterol, 83 determination of, in unsaponifiable matter, 231 in animal oils, 317 in cod liver oil, 487 Cholesterones, 233 Cholesteryl acetate, 84, 232 benzoate, 84, 231 oleate, 16 palmitate, 16 stearate, 16 Cliolestol reaction, 85 Choline, 7 Cloth oils, 704 Coast cod oil, 476 Cocceric acid, 64 Coccerin, 15 Cocceryl alcohol, 76 Cocceryl coccerate, 15 Cochineal wax, 15, 45, 76 Cochin oil, 538 Cocoa butter, 527 Cocoa nut oil, 537 nut oleine, 541 nut stearine, 541 Cod liver oil, 475 liver oil degras, 702 Cod oil, 475 Coffee berry oil, 465 Cohesion figures, 274 Cold test, 136, 713 Colophony, 234 Colouring matters in butter, 614 matters in soap, 772 Colour of fats, 319 Colour reactions, 313 Colza oil, 399 Congealing points of oils, 259 Consistency, 102 Constant acid value, 206 ether value, 206 saponification value, 206 Constituents of fat and waxes, 24-86 Copper, detection of, in fats, 98 Coprah oil, 537 Copraol, 528 Corn oil, 372 Corroine, 695, 704 Cotton seed foots, 692 seed oil, 375 seed oil, blown, 734 826 OILS, FATS, AND WAXES Cotton seed oil, detection in lard, 580 seed oil, detection in tallow, 597 seed oil group, 366 seed oil rubber substitute, 743 seed stearine (acid), 692 seed stearine (fat), 506 seed wax, 649 Coula oil, 5 Crab wood oil, 509 Cresylic acid in soap, 783 Critical temperature of dissolution, 122, 276 Crotonic acid, 176 Croton oil, 414 Crotonoleic acid, 26, 414 Cryoscopic method of testing butter, 630 Curcas oil, 416 Curcuma, detection of, in butter, 614 Dame’s violet oil, 363 Daturic acid, 47 Degras, 693 former, 699 Diacetylglycid, 678 Diagometer, 121 Dibasic acids, 72 Dieerotin, 3 Dierucin, 2, 191 Diglycerides, 2, 190 determination of, 190 Dihydroxyasellic acid, 70 Dihydroxybehenic acid, 71 p-Dihydroxybehenic acid, 71 Dihydroxyheptadecylic acid, 70 Dihydroxyjecoleic acid, 70 Dihydroxylated acids, 69 Dihydroxypalmitic acid, 70 Dihydroxystearic acid, 66, 70, 141 Dihydroxystearidic acid, 70 Dihydroxystearo-sulphuric acid, 65 Dihydroxytiglic acid, 69 Dika oil, 533 Dimelissin, 3 Diricinoleic acid, 65 Distearin, 3 Distillation glycerin, 805 stearine, 755 Distilled glycerin, 786, 802 grease, 691 grease, analysis of, 820 grease oleine, 691 grease stearine, 691, 755 grease stearine in tallow, 597 oleine, 746 stearine, 196, 755 Doeglic acid, 58 Doegling oil, 278 Dog fat, 551 Dolphin oil, 278, 495 Domestic cat fat, 551 duck fat, 551 Driers, 737 Drying of fatty acids, 180 oils, 10 oils, description of, 336-366 Drying oils, general characters, 279 Dutch butter, 678 Dynamite glycerin, 802 Earthnut oil, 441 Edible fats, 678 oils, 684 Egg oil, 503 Elseomargaric acid, 60 Elaeostearic acid, 60 Elaiclic acid, 57 Elaidin, 5 test, 280 Elaine, 765 Electrical conductivity, 121, 275 Elk fat, 551 Emulsion wool oils, 709 Erucic acid, 59 Erucin, 5 Ethal, 74 Ethane series of alcohols, 73 Ethereal oils in fats, 90 oils in soap, 772 Ether value, 154 Examples, 811 Extraction apparatus, 66 Fallow buck fat, 551 Fat, definition of, 1 determination of, 90 estimation of water in, 88 nature of, 1, 2 preparation of, for analysis, 92 Fat, badger, 551 beef marrow, 586 blackcock, 551 bone, 587 butter, 601 chamois, 551 chicken, 551 dog, 551 domestic cat, 332, 551 domestic duck, 332, 551 elk, 551 fallow buck, 551 fox, 551 goose, 559 hare, 555 horse, 552 horse marrow, 555 human, 562 milk, 601 pigeon, 551 pine marten, 551 polecat, 551 rabbit, 557 roebuck, 551 sawarri, 521 stag, 641 starling, 551 turkey, 551 ucuhuba, 544 wild boar, 332, 564 wild cat, 332, 551 wild duck, 332, 551 INDEX 827 Fat, wild goose, 332, 561 wild olive, 550 wild rabbit, 332, 558 wool, 686 Fats, animal, 550 edible, 678 properties of, 8 saponification of, 18 solid, 506 synthetical, 676 unsaponifiable matter in, 6 vegetable, 506 waste, 687 Fatty acids (see Acids), 26-72 acids, acetyl values of, 164 acids, acid values of, 150 acids, action on indicators, 31 acids, boiling points of, 30 acids, determination of, 182 acids, drying of, 180 acids, free, determination of, 182, 183 acids, free, in fats, 7 acids, free, in waxes, 16 acids, insoluble, 31 acids, insoluble, determination of, 180, 191 acids, insoluble, preparation of, 100 acids, liquid, 108, 149 acids, melting points of, 27 acids, non-volatile, 30 acids, non-volatile, examination of, 196 acids, properties of, 27 acids, salts of, 33 acids, saturated, 149 acids, solid, 192 acids, solidifying point of (titer test), 133 acids, solubility of, 30 acids, soluble, 30, 31 acids, viscosity of, 33 acids, volatile, 30, 154 Fatty oils, 1, 718 oils, as lubricants, 718 oils, properties of, 8 Fin-back oil, 492 Fir seed oil, 358 Fish oils, 278, 469 Fish stearine, 475 Fish tallow, 472, 475 Flash point, 715 point of mineral oils,^7l7 Fluorescence, 226, 722 Formalin, 616 Formic acid, 527 Fox fat, 551 Fractional crystallisation, 140 distillation, 144 Free fatty acids, see Fatty acids Freezing point of oils, 135 Freezing mixtures, 135 Fuller’s grease, 693 Gaduine, 481 Gaidic acid, 53 Galam butter, 513 Galena oils, 726 Galipot, 235 Garden cress oil, 397 rocket oil, 363 German sesame oil, 367 Getah wax, 649 Gingili oil, 385 Glycerides, 1, 2, 336-642 Glycerin, chemically pure, 786 commercial, 786 crude, 805 crude, distillation, 805 crude, saponification, 805 crude, soap lye, 805 crystallised, 786 distilled, 802 dynamite, 802 in soap, 782 in spent lyes, 809 refined, 786 Glycerol, 77 determination of, by oxidation processes, 208 determination of, by the acetin process, 213, 806 determination of, by titration with caustic potash, 208 determination of, in chemically pure glycerin, 790 determination of, in crude glycerin, 806 determination of, in dynamite glycerin, 802 Glycerolphosphoric acid, 7 Glyceroxides, 79 Glyceryl stearate, 2 Glycolic series of alcohols, 76 Glycyl ethers, 2, 80 arsenite, 80 trinitrate, 80 Goa butter, 531 Goat’s tallow, 598 Gold chloride test for cotton seed oil, 384 Goose fat, 559 Grape seed oil, 418 Grease, brown, 686 distilled, 690, 820 fuller’s 693 lubricating, 726 recovered, 686, 816 wool, 686 Yorkshire, 687, 816 Gutzeit’s test, 789 Haddock liver oil, 485, 489 Hake liver oil, 485 Hare fat, 555 Hazelnut oil, 449 Heat of bromination test, 300 Hedge mustard oil, 399 Hehner value, 160 value of fatty oils, 306 value of solid fats, 328 Hemp seed oil, 348 Henbane seed oil, 365 Herring oil, 485 Hexahydroxystearic acid, 72 828 OILS, FATS, AND WAXES Hirschsohn’s test for cotton seed oil, 384 Horse fat, 552 Horse marrow fat, 555 Horses’ foot oil, 501 Hiibl iodine value, 170 Human fat, 562 Humpback oil, 492 Hysenic acid, 50 Hydrocarbons, 217 Hydrolysis of fats, 18 of soap, 35 of waxes, 22 Hydrostatic balance, 125 Hydroxy(lated) acids, 63, 64, 68 acids, determination of, 204 Hydroxyoleic acid, 55 Hydroxystearic acid, 68 Hypogaeic acid, 53 Ignition point, 717 Illipe oil, 8, 511 Indian laurel oil, 365 Indicators in fat analysis, 31 Inner anhydrides, 206 Inner iodine value, 195, 312 Insect wax,[,672 Insoluble fatty acids, 31, 191 Iodine, action on fats, 14 in cod liver oil, 487 value, 167, 170 value of liquid fatty acids, 312 value of oils and liquid waxes, 307 value of solid fats, 329 Iron in fats, 99 Isanic acid, 63 Isano oil, 362 Isobutylacetic acid, 43 Isoceryl alcohol, 75 Isocetic acid, 45 Isocholesterol, 85 detection of, in unsaponifiable matter, 231 Isocholesteryl acetate, 85 benzoate, 85 stearate, 16 Isodihydroxybehenic acid, 71 Isoerucic acid, 60 Isoglycerol, 83 Isolinolenic acid, 62 Isolinusic acid, 72, 141 Isooleic acid, 57 Isoricinoleic acid, 65 Isotrihydroxystearic acid, 71 Isovaleric acid, 43 Jambo oil, 413 Japanese wood oil, 345 Japan fish oil, 472 Japan wax, 546 wax, detection in beeswax, 659, 666 Jaw oils, 496, 498 Jecoleic acid, 59 Jecoric acid, 62, Kapok oil, 375 Kitchen grease, 686 Kokum butter, 531 Kottstorfer value, 151 Labiche test for cotton seed oil, 384 Laemoid, 33 Lactine, 528, 541, 682 Lactones, 206 Lallemantia oil, 347 Lanoceric acid, 67 Lanolin alcohol, 76 Lanoline, 689 Lanopalmic acid, 63 Lard. 563 oil, 584 stearine, 584 substitutes, 682 Laurel oil, 509 nut oil, 509 Laureol, 541 Laurie acid, 44 Laurin, 4 Laurostearin, 4 Lead acetate test for cotton seed oil, 384 Lead, detection of, in fats, 98 estimation of, in fats, 98 plaster, 785 powder, 231 Lecithin, 7, 97 in butter, 604 Liebermann-Storch reaction, 226 Lignoceric acid, 49 Lime, in fats, 97 saponification, 745 soaps in bone fat, 749 Linolenic acid, 62 Linoleum, 741 Linolic acid, 60, 144, 202 Linoxyn, 61, 288, 337 Linseed cake, 675 oil, 336 oil, adulteration of, 343 oil, boiled, 735 oil rubber substitutes, 743 oil varnishes, 739 Linusic acid, 72, 141 Lipochromes, 85, 315 Liquid fatty acids, 141, 192 determination of, 202 Liquid waxes, 277, 643 Lithographic varnishes, 739 Litmus, 33 Livache test, 285 Liver oils, 278, 469, 474 Lubricating oils, 712 Lycopodic acid, 54 Macassar oil, 520 Mace butter, 523 Madia oil, 360 Mafura tallow, 521 Magma, 693 Mahwah butter, 511 Maize oil, 372 Malabar tallow, 549 INDEX 829 Mangosteen oil, 531 Margaric acid, 47 Margarine, 591, 678 Margarine oil, 591 Marine animal oils, 468, 469 Marine soaps, 45 Maumene test, 291 Medullic acid, 587 Melissic acid, 50 Melissin, 5 Melissyl alcohol, 75 Melting point, determination of, 130 point of fats and waxes, 323 point of fatty acids, 27 point of mixed fatty acids from oils and liquid waxes, 260 point of mixed fatty acids from solid fats and waxes, 325 Menhaden oil, 470 Metallic soaps, 41, 785 Methylated spirit, 19 purification of, 20 Methylorange, 31 Microscopic examination, 121 Milk fat, 601 Millet oil acid, 61 Milliau test for cotton seed oil, 383 Mineral oil, 224 Mineral oils as lubricants, 719 Mkanyi fat, 526 Mocaya oil, 534 Moellon, 694 Mohamba oil, 363 Molecular weight of fatty acids, 184, 188 Monocerotin, 3 Monoglycerides, 2 Monohydroxylated acids, 68 Monomelissin, 3 Monostearin, 2 Moringic acid, 26 Morrhuic acid, 481 Morrhuine, 481 Mowrah seed oil, 511 Mucilage, 692 Mutton tallow, 598 Myricin, 15, 661 Myricyl alcohol, 75 palmitate, 15 Myristic acid, 45 Myristin, 4 Myrtle wax, 542 Neat’s foot oil, 504 Neoline, 710 Neutral fat, determination of, 182 fat in soaps, 779 Neutral fats, 2 Niger seed oil, 354 Nitric acid, action on fats, 13 Nitric acid test for cotton seed oil, 381 Nitroglycerin, 80, 803 Nitrous acid, action on fat, 13 acid in elai'din test, 280 Non-drying oils, 279, 426 Non-saturated fatty acids, 192 Nucoline, 541 Nutmeg butter, 523 Nut oil, 350 Oba oil, 533 Occurrence of fatty acids, 26 Ocotilla wax, 649 Octodecyl acetate, 74 alcohol, 74 palmitate, 15 Ocuba wax, 649 Oil, acorn, 434 almond, 435 apricot kernel, 428 arachis, 441 arctic sperm, 278, 647 basswood, 393 beechnut, 393 beeswax, 657 ben, 467 black, 693 black fish, 495 black mustard, 407 bottlenose, 278, 647 Brazil nut, 395 cabbage seed, 265 Californian nutmeg, 441 cameline, 367 candle nut, 362 carapa, 509 castor, 420 celosia, 365 Ceylon, 538 chaulmoogra, 508 cherry kernel, 426 cherry laurel, 428 coast cod, 475 Cochin, 538 cocoa nut, 537 cod, 475 cod liver, 475 coffee berry, 465 colza, 399 coprah, 537 corn, 372 cotton seed, 375 coula, 5 crab wood, 509 croton, 414 curcas, 416 dame’s violet, 365 dika, 533 doegling, 278 dolphin, 278, 492 earthnut, 441 egg, 503 fin-back, 492 fir seed, 358 garden cress, 397 garden rocket, 363 German sesame, 367 gingili, 385 grape seed, 418 haddock liver, 485, 489 hake liver, 485 830 OILS, FATS, AND WAXES Oil, hazelnut, 449 hedge mustard, 399 hemp seed, 348 henbane seed, 365 herring, 485 horses’ foot, 501 humpback, 492 illipe, 8, 511 Indian laurel, 365 isano, 362 jambo, 413 Japanese wood, 345 Japan fish, 472 kapok, 375 lallemantia, 347 lard, 584 laurel, 509 laurel nut, 509 linseed, 336 macassar, 520 madia, 360 maize, 372 mangosteen, 531 margarine, 591 menhaden, 470 mocaya, 534 mohamba, 363 mowrah seed, 511 neat’s foot, 504 niger seed, 354 nut, 350 oba, 533 olive, 451 olive kernel, 464 palm, 517 palm nut, 535 peach kernel, 432 peanut, 441 pine nut, 358 pistachio, 449 plum kernel, 430 poonseed, 509 poppy seed, 352 porpoise, 497 pumpkin seed, 371 purging nut, 416 radish seed, 411 rape, 399 ravison, 273, 336, 401 ray liver, 485 rice, 447 salmon, 470 sanguinella, 440 sardine, 472 seal, 490 secale, 468 seek, 693 sesame, 385 shark liver, 485, 487, 489 sheep’s foot, 499 skate liver, 485, 489 sod, 693 soja bean, 369 sperm, 278, 643 sprat, 485 Oil, strophantus seed, 467 sunflower, 356 tallow, 591 tea seed, 447 teel, 385 tobacco seed, 366 ungnadia, 466 ungueko, 362 walnut, 350 wax, 352 weld seed, 366 whale, 492 wheat meal, 434 white mustard, 409 Oil cakes, 673 nuts, 544 thickener, 56, 720, 785 thickener in lubricating oils, 720 Oils, animal, 468-505 base, 13, 733 blown, 13, 733 blubber, 277, 490 burning, 685 cloth, 704 drying, 10, 277, 336-366 drying properties of, 277, 279 edible, 684 fatty, 718 fish, 277, 278, 470 galena, 726 liver, 277, 474 lubricating, 712 marine animal, 469 mineral, 225, 719 nature of, 1 non-drying, 426 non-drying, properties of, 10, 277 oxidised, 13, 733 paint, 685 plumbago, 726 resin, 225, 721 salad, 684 semi-drying, 366 tar, 225 terrestrial animal, 499 thickened, 733 turkey-red, 726 vegetable, 336-468 vulcanised, 742 wool, 704 Oleaginous seeds, 673 Oleic acid, 54 acid, commercial, 765 acid, conversion into candle material, 747 acid, determination of, 192, 197, 201 acid, determination of, in press cakes, 753 Olein, 5 Oleine, 745 cotton foots, 692 distilled, 746 distilled grease, 691 saponification, 746 saponified, 746 wool fat, 691 INDEX 831 Oleine wool oil, 704 Oelodi stearin, 3 Oleomargarine, 591, 681 Oleo-palmito-butyrate, 3 Oleo-refractometer, 119 in analysis of butter, 623 in analysis of lard, 578 in analysis of oleine, 769 in analysis of olive oil, 459 Oleostearine, 576 Olive oil, 451 kernel oil, 464 oil grease, 451 Opium wax, 15, 649 Optical methods of examination, 261 Organoleptic methods, 252 Oxidation of unsaturated fatty acids, 68 Oxidised oils, 13, 733 Oxygen absorption test, 285 Oxyoelic acid, 61 Ozokerit, 763 Paint oils, 685 Palmitic acid, 46 acid, determination of, 199, 201 acid, separation from oleic acid, 196 Palmitin, 4 Palmitolic acid, 60 Palm oil, 517 nut oil, 535 nut oleine, 537 oil grease, 520 wax, 649 Paraffin scale, 759 wax, 757 wax candles, 757 wax, detection in unsaponifiable matter, 232 Para-oleic acid, 57 Pattern test, 275 Peach kernel oil, 432 Peanut oil, 441 Pentadecylic acid, 76 Pentaricinoleic acid, 728 Phenolphthalein, 32 Phospho-molybdic acid, 316 Phosphoric acid as reagent, 278, 316 Phosphorus in fats, 7, 97 Phulwara butter, 511 Pliysetoleic acid, 53 Physical methods of examining fatty oils and liquid waxes, 253, 254-276 Physical methods of examining solid fats and waxes, 320 Physical properties of oils, fats, and waxes, 102-136 Phytosterol, 86 detection of, in oils, 317 in palm oil, 319 in unsaponifiable matter, 231 Picnometer, 125 Pigeon fat, 551 Pimaric acid, 235 Pinates, 237 Pine marten fat, 551 Pine nut oil, 358 Piney tallow, 549 Pistachio oil, 449 Pitch, from distilled grease, 692 from stearine, 755 from wool fat, 692 Plumbago oils, 726 Plum kernel oil, 430 Polarimetric examination, 120 examination of oils, 267 examination of resin oils, 228 Polarisation microscope, 121 Polecat fat, 551 Poly glycerols, 788, 809 Polyricinoleic acids, 65 Poonseed oil, 509 Poppy seed oil, 352 seed oil rubber substitute, 743 Porpoise oil, 497 Potash soaps, 769 Poutet’s test, 280 Premier jus, 591 Psyllostearyl alcohol, 76 Pumpkin seed oil, 371 Purging nut oil, 416 Qualitative examination of fats, 138 Qualitative reactions, 313 Quantitative analysis of fats, 147 Quantitative reactions, 147 Rabbit fat, 557 Radish seed oil, 411 Rambutan tallow, 49, 526 Rancidity, 11 Rape oil, 399 oil, blown, 734 oil group, 397 oil rubber substitute, 743 oil stearine, 190 Rapic acid, 58 Ravison oil, 273, 336, 401 Ray liver oil, 485 Recovered black oil, 693 grease, 686 Red oil, 766 Refractive indices of fats, 262 indices of oils, 333 Refractive power of fats, 113 Refractometer, 114-119 Refractometric examination of oils, 261-267 Reichert’s distillation process, 155 Reichert value, 154 Reichert-Meissl value, 154 values of oils and liquid fats, 306 values of solid fats, 329 Renard’s test for arachis oil, 445 test for resin oil, 227 Residues from distillation of glycerin, 809 Resin, 234 detection of, 238 determination of, 239 oil in lubricating oils, 721 oils, 225-228 soaps, 237, 779 832 OILS, FATS, AND WAXES Resin spirit, 225 Resinates, 237, 785 Rice oil, 447 Ricinelaidic acid, 65 Ricinic acid, 66 Ricinisoleic acid, 64 Ricinoleic acid, 64 Ricinolein, 5 Ricinoleo-sulpliuric acid, 65 Roebuck fat, 551 Rotation of polarised light, 120 Rubber substitutes, 742 Saffron in butter, 615 Salad oils, 684 Salicylic acid in butter, 616 Salmon oil, 470 Salts of fatty acids, 33 Sampling of fats, 87 Sanguinella oil, 440 Saponification, 18-23 equivalent, 152, 306 glycerin, 805 oleine, 746 stearine, 755 technical, 745 technical, by means of acids, 746 technical, by means of lime, 745 technical, by means of water, 746 value, 151 values of ethers, 154 values of fatty oils, 303, 304 values of glycerides, 153 values of liquid waxes, 303 values of solid fats, 329 values of waxes, 154, 329 Saponified oleine, 7 45 stearine, 755 Sardine oil, 472 Sativic acid, 72, 141 Saturated acids, 42 acids, determination of, 192 acids, examination of, 140 Sawarri fat, 521 Scale, see Paraffin scale Seal oil, 490 oil, blown, 743 oil degras, 702 Seeds, oleaginous, 673 Seek oil, 693 Semi-drying oils, 366 Sesame oil, 385 Sesamin, 389 Shark liver oil, 485, 487, 489 liver oil degras, 702 Shea butter, 513 Sheep’s foot oil, 499 Ship’s fat, 686 Skate liver oil, 485, 489 Skin grease, 686 Soap, carbolic, 783 curd, 770 dry, 785 hard, 39, 769 hydrolysis of, 35 Soap, insoluble, 785 medicated, 773 metallic, 41, 785 milled, 771 potash, 39 soda, 39 soft, 39, 769 superfatted, 779 textile, 784 toilet, 771 transparent, 773 Soap powders, 785 Soaps, 33, 769 Sod oil, 693 Soja bean oil, 369 Solid fats, 506 lubricants, 726 oleic acid, 57 saturated acids, 140 unsaponifiable substances, 229 waxes, 649 Solidifying points, determination of, 130 points of fats and waxes, 323 points of fatty acids from fats and waxes, 325 points of mixed fatty acids, 260 points of oils, 259 Solubility of fatty acids, 30 of oils as a means of identification, 269 of solid fats, 328 Soluble castor oil, 13, 733 Soluble fatty acids, 31, 191 neoline, 710 Soxhlet’s extractor, 90 Specific gravities of fats and waxes, 320 gravities of oils, 254-258 Specific gravity, determination of, 123 Specific temperature reaction, 296 Spectroscopic examination, 113, 261 Spermaceti, 669 candles, 756 Sperm candles, 756 oil, 278, 647 oil, blown, 734 Sprat oil, 485 Stag fat, 641 Stannic chloride as reagent, 227 Starch, detection of, 89 Starling fat, 551 Stearate, amyl, 4 giycyl, 2 Stearates, 48 Stearic acid, 47 acid, commercial, 745 acid, determination of, 198, 201 acid, separation from oleic acid, 192, 196 Stearin, 4 Stearine, 745 candles, 745 distilled, 691, 755 distilled grease, 691, 755 from cotton seed foots, 692 pitch, 755 Stearolactone, 69 determination of, 206 INDEX 833 Stearolactone in candle material, 747 Stearolic acid, 60 Strophantus seed oil, 467 Suberic acid, 73 Sugar in soaps, 783 Sulphocarbon oils, 451, 463 Sulplioleates, 732 Sulphostearic acid, 747 Sulphur, action on fats, 14 detection of, in fats, 95 determination of, in fats, 93 Sulphur chloride test, 282 chloride in examination of lard, 582 chloride thermal test, 298 Sulphuric acid, action on fats, 13 acid colour test, 315 acid Maumene test, 291 acid saponification, 746 Sunflower oil, 356 Sweet oils, 684 Sylvie acid, 236 Tallow, 591 beef, 592 Borneo, 533 Chinese, 515 goat’s, 598 mafura, 521 Malabar, 549 mutton, 598 piney, 549 rambutan, 49, 526 veal, see Veal tallow vegetable, 515 Tallow candles, 745 oil, 591 stearine, 591 titer, 749 Tangkallah fat, 44 Tariric acid, 61 Tar oils, 225-229 Tea seed oil, 447 Teel oil, 385 Temperature reaction, 291 Terebenthene number, 228 Terrestrial animal oils, 468, 499 'fetrahydroxystearic acid, 72 Textile soaps, 784 Theobromic acid, 527 Therapic acid, 63 Thermal tests, 291, 333 tests with bromine, 300 tests with sulphuric acid, 291 tests with sulphur chloride, 298 Thermekeometer, 294 Thermo-regulator, 93 Thermostat, 93 Thickened oils, 733 Tiglic acid, 53 Tigliceric acid, 67 Titer test, 133 test of mixed fatty acids, 327 Tobacco seed oil, 366 Tournant oil, 451, 464 oil, analysis of, 811 Train oil, 277, 469, 492 Triacetin, 3, 26, 677 Triacetyldiglycerol, 678 Triarachin, 5 Tribrassidin, 5 Tributyrin, 3 Tricerotin, 5 Trielaklin, 5 Trierucin, 5 Triglycerides, 3 Trihydroxystearic acid, 71 Triisovalerin, 4 Trilaurin, 4 Trimelissin, 5 Trimyristin, 4 Triolein, 5 Tripalmitin, 4 Triricinolein, 5 Tristearin, 3 Turkey-red oil, 464 Turkey-red oils, 726, 727 oils, detection of iron in, 99 Ucuhuba fat, 544 Ultimate analysis of fats, 137 Uinbellulic acid, 27, 44, 508 Ungnadia oil, 466 Ungueko oil, 362 Unsaponifiable, definition of, 217 detection of, 217 determination of, 146, 218, 222 examination of, 224 in fats, 6 in waxes, 17 substances, liquid, 224 substances, solid, 229 Valenta’s test for resin oils, 228 test for fatty oils, 270 Valerin, 4 Varnishes, lithographic, 739 wax, 651 Veal tallow, 273, 328, 578 Vegaline, 682 Vegetable butter, 541, 6S2 fats, 506 oils, 336-468 oils, distinction between, and animal’oils 317 tallow, 515 waxes, 649 Vegetaline, 541 Viscosimeter, 105-112 Viscosimetric examination, 268 Viscosity, 103 of fatty acids, 33 Volatile fatty acids, 30, 191 fatty acids, examination of, 139 Vulcanised oils, 742 Walnut oil, 350 Washing powders, 785 Waste fats, 687 Water—estimation in fats, 88 Wax, candles, 755 834 OILS, FATS, AND WAXES Wax, definition of, 1 oil, 352 quantitative examination of, 147 saponification value of, 154 solidifying points of, 323 Wax, bees, 655 carnatiba, 649 Chinese, 672 cochineal, 15, 45, 76 cotton seed, 649 getah, 649 insect, 672 Japan, 546 myrtle, 542 ocotilla, 649 ocuba, 649 opium, 15, 649 palm, 649 varnishes, 651 wool, 651 Waxes, animal, 651 chemical constitution of, 14 liquid, 277, 643 properties of, 17 saponification of, 22 Waxes, solid, 649 vegetable, 649 Weld seed oil, 366 Whale oil, 492 oil degras, 702 Wheat-meal oil, 434 White mustard oil, 409 White substitutes, 742 Wild boar fat, 564 cat fat, 551 duck fat, 551 goose fat, 561 olive fat, 550 rabbit fat, 558 Wool fat, 651, 687 grease, 651, 687 grease in soaps, 779 oils, 704 wax, 651 Yorkshire grease, 687 Zinc chloride, product of action of, on oleic acid, 812 THE END Printed by R. & R. Clark, Limited, Edinburgh. JOHN M‘NEIL AND CO. (Formerly AITKEN, M NEIL AND CO.) Engineers. GLASGOW .—Colonial Iron Works, Govan. Telegrams.—“ Colonial,” Glasgow. LONDON .—35 Queen Victoria Street, E.C. Telegrams.— 1 Idustria,” London. Sugar and Rice Machinery. JOHN J. GRIFFIN & SONS, Ltd. MANUFACTURERS OF CHEMICAL AND PHILOSOPHICAL APPARATUS. All requirements for the investigation of the properties of Oils, Fats, etc. Viscometers. Oil Testers. BALANCES AND WEIGHTS. MILK TESTERS AND MILK TUBES. S - CATALOGUES upon Application. 22 Garrick Street, London, W.C. CHEMICAL APPARATUS. For General Work. APPARATUS FOR COMMERCIAL ANALYSIS ' OF OILS, FATS, ETC. FOR VISCOSITY— Viscosity Apparatus, as figured, complete with burner, or spirit lamp if preferred, and two thermo¬ meters, £1:7 : 6. Simpler form, with one thermometer, and without arrangement for heating, 10s. 6d. Redwood’s Viscosity Apparatus, standardised for the determination of the viscosity of lubricating oils, £4: 10s. 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