fo f ’ bo 7,6 <2 f ‘J ; ae / pe er Saar dee Aaa ait > me” & q F Anes ro té “The Wicked Borroweth,and Returneth Not Again: Ee rn etnies eenas- ey FRANKLIN INSTITUTE LIBRARY PHILADELPHIA, PA. Clanfe Les) 3 Portes Book Ae. Aeneas 3 S ad, 8 iG Accession) BO 4 5G = ' Given by Rinswanger | t . ST de> ES al == : 4 i al a a ra Mg Nee oy Cp Mgr m "AS .s a Whpsical and Chemical Examination of Waints, Varnishes, and Colors By HENRY A. GARDNER Director Scientific Section, Educational Bureau Paint Manufacturers’ Association of the United States; National Varnish Manufacturers’ Assocta- tion, Co-operating SECOND EDITION Institute of Paint and Warnish Researeh Washington, BD. C. at me Pi ‘ Es COPYRIGHT — BY H. A, GARD : all .: / ie A el E Roy war: r™,! i] Pog + DEDICATION. To the HON. HERBERT HOOVER , U.S. Secretary of Commerce Under whose helpful engineering guidance and en- couragement, many problems have been solved by workers in the industry, this volume is respectfully dedicated. Chapter No. I II III IV Vv VI VII VIII IX xX >. XII XIII XIV XV XVI XVII XVIII XIX XX XXI XXII XXIII XXIV XXV XXVI XXVII XXVIII XXIX XXX XXXI XXXII XXXII XXXIV XXXV XXXVI XXXVII XXX VITI XXXIX XL XLI XLII XLIII CONTENTS Page Physical Examination of Paint Materials... 9 Pfund Paint Testing Instruménts| 273.0 19 A. Study of Color Systems...<.. i 34 Plasticity and Yield Value......0.5.. ee ee 48 An: Experimental Drying Time Meter gee 56 A Color Change Cabinet... jesse 61 Use of the Microscope in Examining Paint Films... 64 Hardnesa of Films... 00002 68 Accelerated Testing Cabinets..ci0 205 = ves Determining the Specific Gravity of Pigments... 81 Determining the Fineness of Paint Pigments... 91 Oil “Absofptioh: of Pigments....40 a) 107 Texture of Pigments......:2.) 5 118 Testing the Light Resistance of Lithopone. 123 Viscosity of Varnishes.................. sncnsur nts stop aay gic a ee le 149 Surface Tension and Interfacial Tension of Varnishes and Parimt Ligue cccace cesscc sss en etre 54 Color Standards. for Varnishes..2.22.0)00. 2 163 Testing the Speed of Evaporation of Thinners for Paint and Varnish. Films... 072s 169 Examination of Turpentine and Mineral Spirits....................... 175 Testing Aluminum. Stearate... 181 Suggestions for Making Exposure Tests .e.cccccccccccccccccewseccseseueee 193 Testing Colors for Tone and Strength. 206 Routine Testing Methods for Physical Properties of White I 2441-54 H-NET oe 210 Analysis of Paints and Paint Vehiclesi... eee 213 Analysis of Paint Oils.uuoc 2s ee 218 Examination of Flaxseedic..2 2 237 Tentative Specifications for Raw Tung Oil 2, 239 Analysis of Varnish......U0 2 BERNE A Sips PANY Sea 246 Analysis of Mixed Driers...) 255 Examination and Analysis of Varnish Resins... 0.0... 258 Tentative Method. of Testing Shellac 267 Testing Insulating Varnishes....3 cee 276 Analysis of Pyroxylin Lacquer’ Coatings eee 283 Bituminous Paints, Varnishes, Cements, and Similar Ma- 23 SE (ARTO 2938 Analysis of White Paint Pigments... eee 304 Analysis of Lead Oxides.....2) gee 333 Analysis of Vermilions).....00 000 eae 347 Analysis of Indian Reds and Red’ Oxides... 351 Analysis of Ochers.2. i i.-cjccivesstoiecn cea eee eer: 355 Analysis of Yellow and Orange Pigments.......ueee 358 Analysis of Blue Pigments...) ee 362 Analysis of Green Pigments... 368 Analysis of Black Pigments........... es 370 PREFACE. The character and suitability of varnishes can best be judged from physical tests. The properties of many pigments and oils are learned through similar means, and in this manner informa- tion may be gleaned that is often far more useful than that af- forded by chemical analysis. In a similar manner, physical tests of paint are rapidly being developed that may ultimately make it possible to predict the serviceability of various products. In this volume, therefore, an attempt has been made to outline or at least refer to the more important physical tests that every paint and varnish laboratory should be familiar with. Physical tests previously published in Scientific Section Circulars have also been abstracted for presentation. Methods are given for the analysis of paints, pigments, oils and similar products. The more important methods adopted by the American Society for Testing Materials (see reports of Committee D-1, A. S. T. M., 1916-1923), as_ well as_ several methods privately communicated, are also contained in the present volume. A large amount of important material here- tofore unpublished is also added. This includes methods for the analysis of organic red colors; bituminous enamels, varnishes and cements; examination of lacquers; analysis of mixed driers; physical and chemical assay of colors; optical examination of . white pigments with tables giving their spectral composition and relative hiding power, etc. 7 Due to the great dissimilarity of specifications for paints and varnishes previously used by the various departments of the United States Government, a member of the War Service Com- mittee of the Paint Industry suggested early in 1918 that steps be taken to inaugurate a plan for correlating all the specifica- tions of the various departments into a series of specifications that would be acceptable to all. This idea undoubtedly led to the formation of the Federal Specifications Board, of which the writer is a member, whose labors have resulted in specifications, which have been bound into this volume. To the following the writer is indebted for material or sugges- tions in the preparation of this book: P. H. Walker, L. L. Steele, F’. W. Smither, E. F. Hickson, E. H. Berger, and I. M. Jacobson, all of the U. S. Bureau of Standards; J. A. Schaeffer, A. H. Pfund, L. E. Barton, F. G. Breyer, P. R. Croll, Harley A. Nelson, me erown, P. H. Butler, R. E. Coleman, P. C. Holdt, H. C. Parks, and other associates. HENRY A. GARDNER. Washington, D. C., January, 1925. ti CHAPTER I. PHYSICAL EXAMINATION OF PAINT MATERIALS. There is given below a series of physical methods by which the character of various pigments, colors, oils and similar prod- ucts may be judged. For the chemist who desires to become familiar with the work of other investigators of the physical properties of these materials, the following references are given. Abstracts of some of these articles are, however, included in this volume. Optical Properties and Theory of Color of Pigments and Paints—H. E. Merwin. Proc. Amer. Soc. Test. Mater. XVII—Part II, 494. Determination of Absolute Viscosity by the Saybolt Universal and Engler Viscosimeters—Winslow H. Herschel. Jbid., 551. The Standard Saybolt Universal Viscosimeter—Winslow H. Herschel. Ibid... X VIII—Part II, 363. The Variable Pressure Method for the Measurement of: Viscosity—E. C. Bingham. Ibid., 378. Paint, a Plastic Material and not a Viscous Liquid: the Measurement of its Mobility and Yield Value—E. C. Bingham and Henry Green. Ibid., XIX—Part II, 640. An Instrument for Measuring the Hiding Power of Paints—R. L. Hallett. Ibid., XX—Part II, 426. A New Colorimeter for White Pigments and Some Results Obtained by Its Use—A. H. Pfund. JIbid., 440. Further Development of the Plastometer and its Practical Application to Research and Routine Problems—H. Green. Ibid., 451. Stress-Strain Measurements on Films of Drying Oils, Paints and Var- nishes—H. A. Nelson. Jbid., XXI, 1111. The Use of Secondary Reference Standards in Process Problems of Color Measurement—H. S. Busby. Jbid., 1139. Relation of Yield Value and Mobility of Paints to Their so-called Paint- ing Consistency—J. E. Booge, E. C. Bingham, and H. D. Bruce. Ibid., XXII. Some Physical Properties of Paints—P. H. Walker and J. G. Thompson. Ibid., XXII. Accelerated Weathering of Paints on Wood and Metal Surfaces—Harley A. Nelson. Jbid., XXII. An Analysis and Comparison of Systems of Color Measurement and Some Notes on Interchangeability in Color Measurement—H. S. Busby. Pot... X AIT. An Application of the Pfund Colorimeter to the Determination of Tinting Strength—J. A. Calbeck. Jbid., XXII. Hiding Power of Paints—R. L. Hallett. Jbid., XXII. Physical Character of Films.—Laboratory methods for de- termining the physical properties of paint and varnish films are very much to be desired. The field is of great importance on account of the growing tendency of specification writers to set requirements for varnishes almost wholly on physical properties, 9 = 10 EXAMINATION OF PAINTS, VARNISHES AND COLORS allowing the varnish maker to use whatever material he finds best suited to produce products that will meet the requirements. Certain physical properties, however, are difficult to define. For instance, requirements for such characteristics as hardness, elasticity, and gloss should be made definite, so that the manu- facturer may check up his products as closely as he might by a chemical analysis of an oil paint. The field opened up by such work is a wide one, and so far but little explored. Excellent work, however, has been done during the last few years by Breyer, Pfund, Bingham, Green, and Hallett, and it is under- stood that these investigators are now making further progress along similar lines.* In 1908 probably one of the first efforts to devise and definitely define physical tests on paint films was made in the old labora- tories of the Scientific Section and published in the First Annual Report of the Section (1908). In this report, methods of pre- paring paint films were outlined and apparatus for determining the tensile strength (Perry filmometer), as well as methods for determining opacity, permeability, effect of weathering, etc., were described. Difficulty was had, however, in some cases with the preparation of films of suitable size and in preserving them for experimentation. While open to criticism from many angles, this early work was productive of much information. With a view to resuming this work and of making a further study of the possibilities along this line, the writer has recently completed a series of tests which indicate that films may be made on a standardized form of bond paper and tested with much less difficulty than when formed on gelatinized or mer- curized metal and stripped therefrom, as in the early experi- ments. In the new tests a series of paints and varnishes were applied in two coat work to a bond paper showing a fairly constant Mullen bursting test. After drying, a series of the painted sheets were tested for thickness, bursting strength, and tensile strength, with a direct reading spring micrometer, Mullen tester, and Scott apparatus, respectively. Duplicate sections about * Hiding Power of White Pigments and Paints. A. F. Pfund—Jour. Franklin Inst., 1919. The Colorimetry of Nearly White Surfaces. A. F. Pfund—Jour. Franklin Inst., 1920. An Instrument for Measuring the Hiding Power of Paints. R. L. Hallett, Proc. A. S. T. M., 1920. A New Colorimeter. ee en PHYSICAL EXAMINATION 11 18” square of the coated paper were then lightly fastened at the ends to wooden decks, and exposed on the laboratory roof, facing south, at an angle of 45 degrees to the vertical. At the end of two months, the spetimens were retested. The results are recorded in the charts. When first approaching the problem, it was thought ad- visable, if possible, to devise an apparatus that would ap- ply a coating of uniform thickness of any kind of paint product to be tested. Much experimental work was carried out, and several mar- keted gummed-paper wrap- ping tape machines were ex- perimented with. The re- sults, however, due to difficul- ties in exerting uniform ten- sion upon the rolled paper, were not encouraging. Ap- paratus with steel and with glass coating blades, similar to those used in the mechan- ical coating of oilcloth with white enamel, was also con- structed and experimented with, but ultimately found to be mechanically deficient. On es 5 full size apparatus in oilcloth IGURE . Testing Paint Film on Paper for Sie SU ss Dae saat coated Tensile Strength. with films of practically uni- form thickness, but such a machine would not be applicable to or available for routine test- ing work. Pending the devolpment of a mechanically perfect coating machine for laboratory use, the writer resorted to the old-fashioned hand-brush method of paint application. It ap- pears, as shown by the several measurements in the charts, that most films applied by this method do not vary in thickness to any marked extent at various sections on one coated sheet. 12, EXAMINATION OF PAINTS, VARNISHES AND COLORS It was noted on the day following the drying of the last coat of paint or varnish that the paper sheets coated with interior short oil varnish would upon even slight bending, show a large number of cracks and checks, while all long oil varnish products were very flexible. In fact, much information regarding the physical nature of the various coatings was obtainable by han- dling the coated sheets. When coating the specimens, it was noted that some of the liquids, such as raw linseed oil and raw linseed oil paints, rapidly penetrate the paper and thus waterproof the back as well as the front. Other coatings, such as rapid drying var- nishes or heavy bodied oils, showed very much less penetration. FIGURE 2 Samples After Exposure on Paper. Top—Long Oil Spar. Top—High Gum. Lower—High Gum Rubbing. Lower—A Cellulose Dope. PHYSICAL EXAMINATION 13 From this result it is recognized that the tests may not be strictly comparative, as in some instances the films would stand out from the paper to a greater extent than in others. On ac- count of this condition, it was suggested that the paper to be used for further tests be coated with a preparation that would be unacted upon by the paint or varnish liquids. Gelatin was proposed for this work. Due to its hygroscopicity and its pos- sible effect upon film separation, it was found the paper might FIGURE 3 Experimental Coating Arrangement. better be treated two or three days before testing, with a uni- form coating of boiled oil, which acts as an insulating medium for the various types of material under test. The first coating waterproofs the back of the paper, and renders it better suited for exposure. In some more recent tests the writer has secured the bond paper to small frames and then applied the coating to be tested. In an effort to set a more exact requirement for “bending test” than that usually prescribed for varnishes, some of the coated papers were tested in the Schopper folding machine, so widely used for testing paper. The results were not satisfac- 14 Material. HaBondPapercnkad. 22: Blank Test aie die ees sb cet samy 9 ay whe. -te a7 weet make aris) Sle, mites PU iar ie eee ee a en ee, cow eww eee ee eo PREPARED PAINT OIL Boiled and Bodied Tung and Menhaden Type ahr ee eRe eyes Me ane Cn e Ol os 1H aL ONietel kee) Ue © SYNTHETIC GARDOL Unsaturated EL Vdracs pons eae leew ot Jan. 3 ieee ‘ew 608 16 Le ew Sle Cee ee ae ee ee i Te ACETATE DopE Navy Standard C. and R. Specification SAN Oe ire ca yee ae oe: Bea Seon AS else Nitrate Dorr Navy Standard C. and R. Specification JAC Os a ee 6 ecw 6 Ve Se we see 2 D. BaLttoon DopE Navy Standard C. and R. Specification gTLDs coe wie eee 6 a 6 eee ie Ee ce BUSES one Time in minutes FIGURE 19 Curves from Results on 1, Raw Linseed Oil 3, Zine Oxide in Raw Linseed Oil 2, Spar Varnish 4, Zine Oxide in Spar Varnish In Table XII the results of tests on a series of lithopones are tabulated. These were of different grades and batches. It will be noted that the flow varied to a considerable extent. Repeat determinations on these after two days’ standing showed some slight differences in flow. Tests after standing for some time might show even greater differences. Judging by the results shown in the different charts, it ap- 52 EXAMINATION OF PAINTS, VARNISHES AND COLORS pears that the flow of paints is very largely determined by the vehicle. Of the liquids tried, the spar varnish and the slightly thinned Litho Oil produced the most “flowy” paints, although these vehicles were of much greater viscosity than the others. Since linseed oil itself shows both a greater initial and final flow than either spar varnish or thinned Litho Oil, the great changes exhibited following the addition of pigments must be due to certain inter-relations between pigment and oil. The differences might be ascribed to various causes, such, for example, as sur- face tension effects, variations in degree of dispersion, with resulting differences in yield value, etc. There does not appear to be any very marked differences between the type of flow of different pigments in the same oil or varnish. For instance, all the spar varnish paints (except those which liver) continue to flow for a considerable length of time, usually more than ten minutes, while the linseed oil paints in general show but very little flow after the first quarter minute. There may, however, be some difference in the extent of flow of different pigments in the same vehicle, but this is not conclusively shown by the results described. Had the differ- ent pigments been used in each oil on a standard volume basis, © much more reliable information might have been gained on this point. Table XII, however, indicates that there may even be differences between different samples of the same pigment in a given oil. The above results indicate why an exterior paint may some- times “run” and “sag.” For instance, if a pigment in linseed oil is applied to a vertical surface, it may look very smooth and in place at first, because of its yield value or resistance to flow. As the oil starts to oxidize, the yield value immediately de- creases because of the oxidized oil formed. The paint may then start to flow out and in time may “sag” and present a streaked appearance. The rates of flow of turpentine and mineral spirits solutions of rosin were measured. Results are given in Table XIII. Such solutions probably have no yield value, the rate of flow being determined by their viscosity and the rate of evaporation of the solvent. A few tests made on varnishes indicate that their rate of flow may to some extent be proportional to the same factors. Some varnishes, however, may actually show slight yield values : : j if the polymerized particles of oil and gum are in an emulsoid — form. 4 PLASTICITY AND YIELD 53 SS —— In a most interesting article entitled “Some Factors which Affect the Plasticity of a Paint,’* E. C. Bingham and A. G. Yates describe the results obtained in grinding certain pigments in various proportions in oil for different periods of time in a ball mill. The measurements for yield value and mobility were made on a plastometer. Rather startling results were obtained, many of which explain some of the phenomena observed in our own work, such as the yield value being independent of the effect of the fluidity of the oil; the mobility of certain mixtures being but little affected by the size of pigment particles, ete. Some of the important conclusions made by Bingham and Yates are as follows: 1—As the grinding ,of a pigment in oil progresses, the yield value at first decreases, but after 30 hours becomes constant. The mobility under the same conditions at first increases, passes through a maximum, and then decreases more and more rapidly. The maximum occurs after about 30 hours in these experiments. 3—Silica and lithopone have very different plasticity at the same weight concentration. When ‘they are compared at equival- ent volume percentages, however, the mobilities are nearly the same and the yield values are not very different. This fact is the more striking since the particle size in the two pigments is so different. 4—Comparing blown oil with acid-refined linseed oil at the same concentration of pigment, the effect of the fluidity of the medium is shown. The mobility falls off in presumably the same ratio as the fluidities of the oil, but the yield value is independent of the fluidity of the oil. 5—Polar colloids—as, for example, aluminum stearate—have very slight influence on the mobility, but they have an extraordi- nary effect in raising the yield value. 7—Moisture exerts a prodigious effect on the plasticity of paint, 0.5 per cent of moisture raising the yield value from 90 to 3450, and at the same time reducing the mobility to one-fourth of its former value. 8—Ovxidation and polymerization affect the fluidity of an oil, so we should expect the mobility to be affected. It was thought that the fall in the mobility on long grinding. might be attribut- able to one of these causes, but grinding in an atmosphere of mtrogen only prevented it, partially. A paint ground | im an atmosphere of carbon dioxide has a yield value three times as high as when ground in the air. | * J. Ind. & Engr. Chem., Oct., 1923, p. 1033. +, 54 EXAMINATION OF PAINTS, VARNISHES AND COLORS The time of the instrument maker and materials for the con- struction of the apparatus averaged about $22.00 per set, not allowing for patterns. Several sets have been made at this laboratory for the industry. TABLE XI—Commercial Paints and Enamels—Diameter of Flow im Inches White Enamels Time in Minutes YY 4 34 1 1% 2 3 4 5 7 10 No. lossssssss.[ 43 | 49 | 456+| 4%—| 54 | 534+| 5+] 5+] 5'4 | 5Y44| 54+ No.2......[4 | 4« | 436+] 4564| 494/44] 5+ | 536-4] 536-4] 54 —| 54 — No. 8............| B%+| 356-4| 334+| 3% | 3%+| 8%+| 8%t|4— |4 | 44 | 4m No.4............| 894+] 8%—| 44 | 436+| 43+| 496+| 4144+| 4564] 404 | 494-4] 404 No5....f4 [434 | 46+4| 49—| 40+] 5 | 5¥6+| 5M —| 5M —| 5M 4+] 54— No.6............4¢@ [4%-|4% [4% [5 | 5% | 5%—| 5m | 5% | B+] 5%— Time in Minutes A \% 34 1 1% 2 3 4 5 7 10 Not............|3% [3% [38% | 3% | 3%+| 3+| 84+| 84+] 8K%+| 84+] 3% No. 2.....1......| 24+] 24+] 234—| 254—| 2364] 2944| 236-4] 296+4| 286+] 296+] 2+ No.0... 19 | 19% | 194-4] 1390-4] 1394-4] 19¢-+| 194-4] 1944] 1%4—| 1%—| 16— No.4...) 196 [156 | 156-4] 154-4] 1944] 1564] 19¢—| 19¢—| 134—| 194 | 194 No.5............)2% | 2%+| 2%-+| 2%-+| 2%-+| 2+] 24—| 24—| 24—| 24—| 24— No.6.ccc:n/2. [2 (2 | 840) 24 1G 0) Sess eee Time in Minutes Y% YY 34 1 1% 2 3 4 5 % 10 Flat Wall Paint...| 244+] 24% 244+] 25+] 234 234+| 2% | 2%+| 2%+]| 2K%4+| 3 | | —— | | | | | | ———<—_ | —_—_—_ Flat White (int.)..| 234 234+] 23+) 2% 24+) 24+) 2%+| 24+) 24+) 2K%+| 3- Egg Shell White Gunterion anuetce 3 38Y%—| 3%+!] 3%4+| 3% 3% 3%+| 34%4+] 3%—-| 3% 334+ ee | Undercoat (int.)...| 33%+] 344+] 3%+ ea 334+| 3%+)| 334+] 3%+4+]| 3%—-—| 3K-| 3K- | Pigmented Varnishes Pigmented Black Varnish. 3). /sis 3% 4% 44+) 444+| 436+] 44+4+| 4% 444+) 494—| 484@—| 44 — *Pigmented Black |_| | ]|—_—_ Varnish 2.5.4 ws 4144+| 43% Bo BM | 8+) BM eee eee 5% | 6— se *Green Baking —_—__|__—_ Hnameleinuc css 3+ 3% 3% 35+] 3%+| 3%+| 4%—-| 4%+] 4% 4% iz ee ee PLASTICITY AND YIELD 55 TABLE XII—Dry Lithopones Ground in Linseed Oil*—Diameter of Flow an Inches Time in Minutes Y% % 34 1 1% 2 3 | 4 5 a 10 MewinGrades 7... 3%+| 3% | 3% | 334+] 344] 34] 3344] 3244] 3144| 336-41 3x64 No. 2Grade....., 254 | 254+] 254+] 214+] 256+| 256+| 25¢+| 25¢+| 25641 25641 2564 No. 3 Grade... 23, | 2% | 23% | 2% | 234 | 23g | 234+] 29241 29441 2944] 29¢+ Bio itGhadast ee es 8 Se Sealer et lee lok lan Noi Grades cos. ea Se 3a) 34a) 3%—| gyalsie—lan ba. No. 6 Grade......| 244—| 24 | 2% | 2% | 214 | 21% | 214 | 236 | 21 | au law No.7 Grade....... 3%—-|3% |3% |3% |3% | 3% | 3% | 3%+1 3%+| 81% +| BK > No. 8 Grade...... 34%4+| 3% | 3% | 3% | 34+] 3%+| 3%+1 3%4+| 3%4-+4| a%4| a%+ No. 9 Grade......| 3%—| 3% | 3% | 3% | 336+] 33+) 334+] 336+| 3344] 3344| 3%+ No. 10 Grade.....| 33% | 334+] 336+] 33+] 3346+| 3%4+| 33¢+| 334+] 3364| 334+] 396+ * All paints were made up in the proportion of 100 grams pigment to 100 grams raw linseed ol.i In this proportion some samples yielded products of much heavier body than others. TABLE XIII—Rosin Solutions Time in Minutes A 4% 34 1 1% 2 3 4 5 C 10 Rosin and Turpentine.........|434 |54 |5%1+/534+/5%—-|5%—-|5K%—-|5K%+\|6-— (6% [6u%- 634 lex+|l7+ (73% |73¢—-|8% |85¢ [836 |93% lowe+ * Rosin and Mineral Spirits... .|6 * Goes beyond largest circle (914 inches) on plate in about 84% minutes. Still flowing after. 10 minutes. These solutions were made by dissolving 100 grams of rosin in 100 grams of the liquid. In both eases fairly smooth circles were formed out to the limit of flow. Turpentine solution was of much higher viscosity. Rubbing Varnish* No. 1 thinned with Turpentine../37% |4 ewe EN al aR 5% |5% 15% [53% |6% 16% No. 2 thinned with 67% Tur- tine and 33 % Mineral Spirits. |4 Ao mh a ee De eel cases ee 534 «|6 64% |6% Z 7% * Two varnishes used contained sufficient thinners to give about same viscosity. CHAPTER V. AN EXPERIMENTAL DRYING TIME METER There have been disputes among producers and consumers as as to the drying time of paints, enamels, oils, and various varnish products. Many of these have been due to the fact that — the method of determining the dryness of a film (touching every hour with the finger) has not been well defined, and especially ———— —_ Fama —o. = —< 2 = mes - —— —_ . PPD I | GZ y | ] ] j ; j j ] st |Z |Z "|= | IZ eal ieee nd NZ Z IA vo WW Caw SSN WN FIGURE 20 Diagram of drying time meter with section of stand for film. Later models of drum on clock are supported by a lace effect circle of metal rather than with wire. I We SI) 18, vi ‘ to the fact that observations could not be made with regularity over the drying period which often occurred late at night. In an attempt to overcome these two factors, the writer has ex- perimented for several months to develop an automatic drying time meter. Several types were designed and constructed before one that would give satisfactory results was developed. It will be noted in the illustration (Fig. 20) that the apparatus consists of an alarm clock device fastened on an upright base. 56 ee ee a a DRYING TIME METER D7 Attached to the hour hand of the clock is a very lightly con- structed wire wheel covered with a circular drum formed of light tin plate or of aluminum. The drum is slotted to receive the test piece upon which the coating is applied. This winds under the mandrel rod at the top of the drum and is pressed in contact at that junction with a sheet of soft, light tissue paper of the same width as the test piece. Both of these are auto- matically pulled from an adjoining double shelf stand, by the action of the clock. Just so long as the coating is wet, it will Stain the tissue paper at the point of junction, the paper adher- ing quite tenaciously to the tacky film. Just at the point of firm setting of the coating, the paper will no longer be stained when it comes in contact with the test piece and will not adhere thereto during its subsequent journey around the drum. The test piece developed for this work after a trial of many materials, consists of a roll of celluloid moving picture film (waste short ends of undeveloped raw stock) that has been light struck but not developed. This material was selected because of its opacity (white silver coated surface) upon which, applied, clear coatings are quite evident. Because of its great smooth- ness of surface, paint and varnish coatings do not penetrate it, but dry upon the surface somewhat as they would upon glass. Moreover, the solvents usually present in paint and varnish ap- parently do not affect the film, and they seem to evaporate in the same time as they would from tin or glass. Solvents of the ester type, or acetone-containing solvents, such as may be used in lacquers, could not be used. Moreover, such film is of a standard size and character of finish and is obtainable in practically any part of the country at a low cost from moving picture firms. After the apparatus is set up, it should be standardized by applying a coating of paint or varnish to the film and allowing it to run for a period of twelve hours. The clock is set at the figure 12, at which’ point the slot for the film will be about 1, inch beyond the mandrel rod. The length of film pulled through over that period is then measured and plotted off into twelve Sections with sub-divisions if desired. Each section will be sub- stantially 114 inches in length, representing one hour’s time. For an apparatus that has thus been standardized, the supply of film to be used therein may then be stamped or printed with Such divisions as are desired. If the drying time of a product is to be determined, which re- 58 EXAMINATION OF PAINTS, VARNISHES AND COLORS quires a 24-hour drying period, a length of film not exceeding 40 inches will generally be found sufficient. It is usual to attach the film late in the afternoon and to make the reading for drying time in the morning, the apparatus running automatically over night. If the tissue paper at the mandrel rod is still being stained, the test is continued. If no stain is shown, the film and tissue are both removed and examined to determine point of drying as indicated above. In an earlier attempt to construct such an apparatus, one with a series of pegs upon a revolving wire wheel, into which the slotted moving picture film would be drawn, was designed. FIGURE 21 Electrically Controlled Moist Cabinet With Recording Gauges for Drying Painted Panels. The pegs were so arranged as to cause an apparatus to drop sand upon the drying film every hour. The sand would re- main adherent to the soft, sticky film. When the coating had become dry, the sand would not adhere and would fall off as the film continued its downward journey. A fairly sharp line of de- marcation indicating the drying time was obtained. This ap- paratus, however, offered certain mechanical difficulties that were not overcome. Atmospheric conditions such as humidity and temperature will have a profound influence on the drying time of any DRYING TIME METER a9 product. The results obtained one day may not, for instance, be thoroughly in accord with those shown another day. It is the writer’s idea, therefore, that the main application of this appar- atus will be for comparative purposes in determining the com- parative drying time of two products. This could be done by using two sets of the apparatus (one constructed with a double drum wide enough to accommodate two films would probably cause a Slowing down of the clock). Another method would be FIGURE 22 Ventilated Moist Cabinet for Studying Drying Time of Oils and Varnishes. to use two small films of approximately one-half inch width upon the present size type of drum and apparatus. Tests have, how- ever, been made thus far with two sets of apparatus. A varnish or oil having a known drying time is used upon one, and the test coating upon the other. When check tests upon the same coat- ings applied to glass were run at the same time, the drying time of the latter as determined by touching with the finger, corres- ponded very closely with the results obtained on the apparatus. The writer offers this development to the industry for com- ment and suggestions for further development. Complete sets 60 EXAMINATION OF PAINTS, VARNISHES AND COLORS can be constructed at a comparatively low cost ($24.00) by ‘a mechanic. For those who cannot arrange to have the apparatus made, sets may be ordered from the writer’s laboratory. Since this work was completed a far superior instrument to determine drying time has been developed by J. A. Sanderson. A description of the new instrument, which is also based upon the retention by the drying varnish, of sand dropped from a fun- nel, will probably appear in the 1925 report of the Varnish Committee of the A. S. T. M. CHAPTER VI. A COLOR CHANGE CABINET For Determining the Discoloration of Interior Whites.—The simple form of cabinet shown in the illustration was designed for use in testing the “yellowing” of interior paints and enamels. It is made of galvanized iron with a double walled air Space in \ LEZ LIS: = ae ae \ Lots LTE Mmm NLT HUNT 1H aa Ge ( LEAH a ot RNS ha N EN FIGURE 23 Dark Chamber. Light Chamber. Gardner Color Change Cabinet. the center. The sides and tops are provided with air ducts and holes for thermometric readings. At the bottom of each chamber, a shallow pan containing several sheets of blotting ‘paper is placed. An ounce and a half of water is added to each pan and readily absorbed by the paper. This amount is usually sufficient to provide high humidity of the atmosphere in the white chamber for a period of 12 hours and in the dark chamber 61 62 EXAMINATION. OF PAINTS, VARNISHES AND COLORS for 30 hours. The entire inner surface of one chamber is coated with flat black and the other chamber with flat white. The white chamber is furnished with electrical connections and a 75- watt blue Daylo Mazda lamp which simulates ordinary noon day- light. A 10-foot length, of insulated wire is provided for plug- ging into any convenient electric light socket. When the lamp is lighted, the temperature in the white chamber will run from 48° C. (118° F.) to 56° C. (132° F.), at various points, whereas the black chamber will show approximately 28° C. (82° F.). Application of Black Cabinet.—A series of metal, wood or other types of slats are coated with white paint, dried, and then exposed in the black cabinet. The warm, humid atmos- phere will quickly develop differences in the colors. In two days’ time a loss of reflection of about 6 per cent has been noticed in one type of paint, due to yellowing of the oil content. Marked differences in such a short period have also been noticed in various types of marketed industrial paints and enamels. In a longer period much more discernible results may be noticed. It is believed that these results may be comparable to what would occur to paints in a very much longer time when exposed on factory walls. The addition of a small amount (5 per cent) of ammonia water to the water used in the pan in this cabinet will greatly ac- — | celerate the yellowing of the paints. Application of White Cabinet.—Paints containing pigments that are easily fogged by strong sunlight may, after proper ex- q posure to the bombardment of transmitted and reflected light rays, be affected to some slight extent in the white cabinet. The paints may be applied to panels and exposed in the cabinet, or the pigment under examination can be rubbed up with a normal quantity of the liquid in which it is to be used in paint. This may then be spread upon a panel and dried. Half of the surface may then be covered with black paper. Daily examination of the panels, until a difference is noted in the covered and un- covered portions, will be instructive. Similar tests nay be made on organic colors that may be easily affected by light. It should be remembered, however, that the light from a Daylo Mazda — lamp is exteremely mild as compared to that from an ultra- violet arc; the latter giving effects in a few minutes that are not obtainable over a long period of time by other means. The white . ee re ee ree ee COLOR CHANGE CABINET 63 cabinet described above may, therefore, be of but little use when a quick test for fogging is desired. The writer is, however, en- deavoring to arrange a cabinet with an extra compartment pro- vided with an iron arc rich in ultra-violet rays. Corrosion.—Hither cabinet may find some application in de- termining the comparative corrosion resistance of meta] panels. The temperature and high humidity should give noticeable re- sults. Similiarly it may be used for determining the rust-in- hibitive properties of pigments. In the latter case the pigment is mixed to a thin paste with water and applied to a small area on a brightly polished steel surface. After exposure for forty- eight hours, the test plates are removed, the pigment washed off, and the area formerly covered by the pigment examined for Signs of rusting or etching. Drying of Paints and Varnishes.—The drying of paints or varnishes in moist atmospheres at definite temperatures might be determined in either cabinet, under light or dark conditions. Other applications of the cabinet may be developed. It is easily constructed and can be made by any local tinsmith. Those who do not care to have them made locally can secure them from the writer at cost. Cabinets in which the drying of paints and varnishes may be determined under set conditions of temperature and humidity have also been designed by the writer. These are shown in Figures 21 and 22. They have been described in early publica- tions of the Scientific Section. CHAPTER VII. USE OF THE MICROSCOPE IN EXAMINING DRIED PAINT AND VARNISH FILMS The microscope has become practically a standard instrument in the equipment of paint and varnish laboratories for the ex- amination of paint pigments. It is believed that its usefulness may be greatly extended by applying it for the examination of all finished paints, enamels or varnishes when Spread out and dried. The elasticity, hardness, porosity, resistance to water, and other physical properties are indicated by examination at low magnifications. Some of the illustrations shown herewith, which are fully described in the titles, demonstrate this point. When new materials are proposed as constituents of existing formule, test batches may be made, brushed out, dried and ex- amined for the characteristics noted above. | Further work has recently been conducted by the writer on dried films that have been scratched with a device under stand- ard conditions and then examined under a microscope. The paper presenting the results is on “hardness” of films and will be issued as a Scientific Section circular in February, 1925. 64 MICROSCOPE 65 ee FIGURE 24 Photomicrograph of surface of an interior rubbing varnish. Sur- face was scratched with a needle. Note clean cut effect due to hard film. FIGURE 25 Photomicrograph of surface of xterior spar varnish. Surface was cratched with a needle. Elastic ind comparatively soft nature of ilm indicated. Also note dark pots due to particles of poly- nerized oil that have become in- Oluble. These particles are often he cause of a “sandy” surface. FIGURE 26 Photomicrograph of surface of an exterior spar varnish. White, Cloudy effect caused by immersion in cold water. Water has not abraded or injured film but has possibly formed an emulsion with the outer layer. FIGURE } yt Photomicrograph of surface of an exterior oil coating showing effect of boiling water which has caused the film to “creep” or pull away from the surface, leaving crater-like bare spots. To the naked eye a white and rough sur- face is indicated. 66 EXAMINATION OF PAINTS, VARNISHES AND COLORS FIGURE 28 Photomicrograph of surface of an oil coating that has shown peculiar crinkling, probably due to surface tension effects. Photomicrograph of a drawn metal article. Note abraded effect of metal. Rapid corrosion would follow unless protected with paint or varnish. FIGURE 30 Photomicrograph of a _ paint coating. Thinner used in the paint was too volatile. Upon evapora- tion from film, it caused formation of small craters. FIGURE 31 _ Photomicrograph of a paint coat- ing. Paint was not _ properly ground in mill. Note rough, gran- ular surface of unground pigment particles. MICROSCOPE 67 FIGURE 32 Photomicrograph of a wall coat- ing. Drying in a dusty room caused adherence of dust particles. These gave surface a darkened appearance. FIGURE 34 FIGURE 338 Photomicrograph of an experi- mental flat coating. Paint con- tained too much volatile matter. Scratch made with a metal point shows dry nature of film. Photomicrograph of a cross-sec- tion of an enamel coating on oil- cloth. Note warp and _ filling threads of cotton fabric, filled sur- face, and enamel film. smooth outer white CHAPTER VIII. HARDNESS OF FILMS Testing the Hardness of Varnish Films.—A method com- municated by William H. Wilkinson, together with some photo- micrographs, is given below. Improvements on this method are being made at the present time, and it is hoped that some more definite recommendation for this very important test will be made. The two prominent methods for determining the hardness of varnishes met with in the literature are those of A. P. Laurie, F. G. Baily, and Jahn. The method of Laurie and Baily consists in obtaining the pressure, applied to a one mm. blunt, hardened steel point, necessary to produce a white Scratch on the film, when the film is drawn beneath the point. This method really measures toughness rather than hardness, since the blunt point when placed on an elastic film will have little effect up to a certain point due to the yielding | nature of the surface over which it is drawn. Jahn’s method determines the pressure necessary to be applied to a cylinder, on which are fastened two blunt, ring- shaped knife edges, to produce track-like impressions on the film. This scheme also has the drawback in that it measures the toughness, elasticity, and adherence of the film to the surface on which it is placed rather than hardness. : Because of the fact that both of these methods use a constant point in varying pressure, it was thought that more reliable information could be obtained by keeping the pressure more or less constant and varying the hardness of the point. Such a method is used in the testing of the hardness of minerals with Mohr’s scale. The problem, therefore, was to find a series of sub- stances of varying hardnesses which would cover a long range from a very soft up to a very hard varnish. Just such a series of substances is put out by the Dixon Crucible Co. in the form of seventeen drawing pencils. The pencils were arranged in the order of their hard- ness, the softest being numbered one and the hardest seventeen. It was decided, after careful] experimenta- tion, to use a sharpened chiseled point rather than a rounded point in that it gives (1) a more definite end point, (2) a more uniform cut. — i ee 68 : f ” 4 q & iH HARDNESS OF FILMS 69 No. 5—Pencil, heavy pressure. No. 6—Pencil, medium pressure. No. 6—Pencil, heavy pressure. No. 7—Pencil, medium pressure. FIGURE 35 Effect of Pressure on End Point. No. 1—Pencil No. 2—Pencil. FIGURE 36 Gloss Oil Drying Time, 20 hrs. No. 3—Pencil. No. 4—Pencil FIGURE 37 Gloss Oil Drying Time, 98 hrs. 70 EXAMINATION OF PAINTS, VARNISHES AND COLORS The varnish films were first produced by flowing the varnish on clean glass plates, but recently we have adopted the method of P. H. Walker and J. G. Thompson for preparing films of uni- form thickness by whirling the varnish on a circular, ground- glass plate at 300 r. p. m. for three minutes. The method of testing consists in ruling off lines on the varn- ish film, using the pencils in sequence with medium pressure until the point is reached which will cut the film. It has been our experience in the last three years that the pressure, provid- ing, of course, it is not too light, has very little effect on the end point; that is, a point which is softer than the varnish film will not cut it, no matter how heavy the pressure, point wearing away instead. This is clearly shown in Figure 35. Not only will this method give the comparative hardness of the film, but will also give information as to the rate of hardening of the film. This may be seen by comparing Figure 36 with Figure 37. While this method has been particularly used by us in test- ing shipments against a standard of the same material, we can See no reason why different varnishes could not be compared if run under identical conditions; e. g., temperature, humidity, thickness of film, etc. Also the method should be applicable to testing the hardness of other films, such as paint, lacquers, etc. For later work on Hardness of Varnish Films, see Scientific Section circulars on this subject to be issued in February, 1925. It is hoped that these circulars will include an article by PrH. Walker and L. L. Steele, who have developed a very satisfactory apparatus for determining hardness. CHAPTER IX. ACCELERATED TESTING CABINETS Accelerated tests on paint and varnish films, through the use of ultra-violet light, artificial rainstorms, and low and high tem- peratures, have received much attention during the past three years. The importance of securing in three weeks’ time infor- mation that might require a year in ordinary roof exposure tests can readily be appreciated. Even though the results of such accelerated tests may not follow exactly those obtained by ex- terior tests, they do, however, guide the investigator in de- termining the comparative life of certain coatings. Probably the first cabinet built to make tests on panels of fair size and to afford means of a real study of the problem was that designed by H. A. Nelson,* who has kindly prepared the following highly instructive resume of his important work. Other later investi- gators have designed types of apparatus along similar lines, Mougey? having constructed one consisting of a series of panels mounted upon a revolving wheel passing through a tank of water. As the panels emerged from the water, they were sub- jected to a mercury are. The writer has also seen other sets of apparatus at the laboratories of the du Pont Experimental Sta- tion, the du Pont Chemical Co., and, the Pittsburgh Plate Glass Co., all of which depend upon cycles of ultra-violet light and water. Two new types of cabinets are also being constructed by the present writer and will be described at a later date. Mr. Nelson’s article is presented below. Development and Present Status of Accelerated Weathering Tests. By H. A. Nelson.—Both manufacturers and consumers of paint and varnish products have undoubtedly long felt the need of information that might lead to the development of a compre- hensive system of accelerated testing for weather resistance. Valuable beginnings of experimental work along this line were made by Gardnert and by Muckenfuss§. The latter developed an * Harley A. Nelson, Chemist in Charge of Paint Section, Research Divi- sion, New Jersey Zinc Company. + H. C. Mougey, General Motors Research Laboratory, Dayton, Ohic. tH. A. Gardner—Paint Technology and Tests—1911, also Physical Test- ing of Paint and Varnish, Circular No. 122, Ed. Bureau, Paint Manufac- turers’ Association of U. S. § A. M. Muckenfuss—Preliminary Report upon a Practical Accelerated Test for Paints and Varnishes—Journal Industrial and Engineering Chem- istry, Vol. 5, No. 7, July, 1918. 71 {eA EXAMINATION OF PAINTS, VARNISHES AND COLORS exposure scheme which was designed to take advantage of the changes in permeability of paint and varnish films, applied on fine mesh screen or hardened paper, to moisture as a measure of deterioration under artificial exposure conditions. The exposure involved light (mercury are and tungsten), moisture (revolving spray) and cool weather (outdoor night exposures). Unfortunately, no investigator has directly followed up this work. Possibly the extensive equipment necessary for accur- ately following the changes in permeability has discouraged any attempt to make routine application of the method. Unfor- tunately, too, the great acceleration possibilities in utilizing a high concentration of ultra-violet radiations were not then en- Atomizing Spray nozzles. . f f ) pinches. FIGURE 38 Type of apparatus that has been successfully used in accelerated weathering experiments. (Nelson.) tirely recognized, so that the real possibilities of the scheme probably were not brought out. Other, more recent, investigationst were directed toward a possible simplification of the application of the idea of acceler- tH. A. Nelson—Accelerated Weathering of Paints on Wood and Metal Surfaces—Proc. A. S. T. M. Vol. 22, Part II, 1922. E 5K ACCELERATED TESTING CABINETS 713 ated weathering. The ideal would, of course, be artificial ac- celerated reproduction on painted wood and metal surfaces of the normal failures that are observed under outdoor exposure conditions. The first laboratory evidence that this might be pos- sible was the fact that an ordinary 100% B. C. W. L.—linseed oil paint film could be made to chalk heavily by exposure for about 13 hours under an ordinary 220-volt mercury arc lamp. The par- ticular importance of the radiations from the ultra-violet portion of the spectrum (below \ = 3800 A. U.) was then demonstrated by the fact that only some loss of gloss could be obtained by ex- posing similar films for about 300 hours at a short distance from an ordinary glass blue-printing lamp. For further experiments, a special vertical quartz burner, 30” long, was developed so that panels in large numbers and of appre- ciable surface area (6” x 12’) might be used. The type of light exposure tank that has been successfully used is illustrated by Fig. 38. The general flexibility of the apparatus originally de- scribed has since been improved by providing a separate water exposure chamber where panels are subjected to the action of a revolving water spray. Only light and moisture were extensively used in the first ex- periments and the following results were obtained with paints and varnishes on wood and metal panels: (1) Loss of gloss and subsequent chalking were easily repro- duced by exposure to ultra-violet radiations in and below the region \ = 3600 A. U. (2) Loss of gloss and chalking were hastened by periodic saturation of the paint film, or by maintaining a saturated at- mosphere in the apparatus during the period of ultra-violet ex- posure. (3) Paints made with pigments which chalk readily upon normal outdoor exposure were the ones which chalked readily under the ultra-violet light. Those pigments which normally re- tard loss of gloss and chalking under outdoor exposure conditions were found to act similarly under the accelerated conditions. (4) Comparisons made with results from outdoor exposures showed a ratio of approximately one day to one month for loss of gloss and initial chalking. For this the accelerated exposure scheme was 24 hours light-cool-24 hours water spray. This ap- proximate ratio was then found to exist for a number of paint combinations representing both chalking and non-chalking pig- 74 EXAMINATION OF PAINTS, VARNISHES AND COLORS ments. (It should be noted, however, that low temperature ex- posures were not generally included in these experiments, and that the conditions of the exposure were what are now known to be very severe for producing a chalking failure.) Ww While Lead 30 4-OuU/t Oor meee see wes ew _—— o— — < “=~ e@— — .. — 6 & S v N a Basic Lead\St/fate Q © - Ou Fe (oJ) eo * -Acce/e. 3 U30 | x : KR 3 j oe eee Outdoor Exp (rs) Accelerated + (hrs) Lighta 64% Water | 24% Prefriga /2% Acceleraled ha a eee FIGURE 39 Comparison of gloss depreciation curves on typical single pig- ment paints under outdoor and accelerated weathering condi- tions. (Nelson.) ~ (5) Chalking once started by exposure to light, was ac- : celerated by exposure to low (freezing) temperatures, especi- é ally when the film had been previously saturated with moisture. é ACCELERATED TESTING CABINETS 15 (6) Cracking was then reproduced to a limited extent on cer- tain paints and varnishes, but only with marked success when some variations of temperature were introduced (outdoor ex- posures in winter were used). The above results went far toward proving the practicability of the method, and the experiments were continued after the installation of a refrigerating equipment which made low tem: peratures available down to about —16° C. Effect of Variations in Exposure Cycle-—The possible effec- tive variables which could then be introduced with the equip- ment at hand were: (1) Light and heat (50° C. to 60° C.) at comparatively low humidities. (Air taken in at outdoor temperatures.) (2) Light and heat with saturated atmospheres. (3) Water spray (washing action of rains). (4) Low temperatures (down to —16° C.). Early in the work it was evident that the ratios between out- door and accelerated weathering would vary with the nature of the exposure cycle used. That great variations in the rates of outdoor deterioration are introduced by climatic differences is also common knowledge. Obviously, then, the next important step was to begin a study of the relative deteriorating effective- ness of each weathering factor (alone and in combinations) as it might be used in an accelerated weathering’ cycle. A comprehensive series of tests with this object in view was made on a group of representative. varnishes, of which the de- tailed results can be found in the literature.* It is important to note that very great variations are observed in the degree and type of deterioration, depending what factors are included in the exposure cycle and the frequency of change from one kind of exposure to another. Briefly, the following conciusions were arrived at as to the apparent relative deteriorating effectiveness of the exposure factors. (1) Most effective (especially in deadening or reducing the distensibility of the film). was a water exposure followed by light. (2) Second and almost as effective was water exposure fol- lowed by refrigeration. This apparently not only helped take the elastic life out of the film, but also acted as a factor in re- * Nelson and Schmutz—Further Study of Accelerated Weathering— Proc. A. o.:1.°M., Vol. 24, 1924; 76 EXAMINATION OF PAINTS, VARNISHES AND COLORS vealing the deterioration brought about under light and water, etc. (3) Next in effectiveness was light (warm and dry) followed by refrigeration. This combination apparently served largely as a factor which brought out, or revealed weaknesses in the film which might be inherent with the original material or intro- duced by other exposures. (4) Considerably lower in effectiveness was the action of light alone. (This refers to the “deadening” action of light after the excess absorbed water has passed off and the film is fairly dry. The lower the moisture in the film the slower is the action of light.) (5) Next was water alone which, in itself, appeared to have a deteriorating effect. i (6) Continued refrigeration, after the film had attained equilibrium at the low temperature, had no appreciable de- teriorating effect. Exposure cycles involving moisture and light were most ef- fective when changes were made frequently. Thus the film was practically always in a saturated state and the light did most damage. Light-refrigeration cycles brought about cracking most quickly with frequent changes, but the final deterioration was greatest under longer periods of exposure when the light de- terioration became proportionately greater. Water-refrigera- tion was most effective with moderately frequent changes. Wolff* in his recently reported work on this subject concludes that cooling a film below the dew point in moist air and the sub- sequent freezing of the moisture in the film, are the most effec- tive deteriorating factors. It is very interesting to note that in the above classification such a combination is ranked a close second in deteriorating effectiveness to water exposure (satur- ated film) followed by light. Wolff does not state under what conditions exposures to light were made in his tests, but if these were made at low atmospheric humidities (on dry films) his conclusions can probably be accounted for. Comparison With Outdoor Exposure Results.—As previously stated in the early experiments, an approximate relation was established between outdoor and accelerated weathering results *Hans Wolff—Testing of Varnishes and Paints, Particularly for Re- sistance to Weather—Farben Zeitung, Vol. 26, pp. 704-705, February 9, 19238. ACCELERATED TESTING CABINETS wht with moisture and light as the major factors involved. It was also subsequently pointed out that this ratio did not hold when the exposure cycle was modified to any appreciable extent (for example, by adding low temperatures to the exposure). This complicates the problem of establishing an exact ratio and it is also possible that on account of variations in weather conditions, except when averages are made to cover a considerable number of years, the accuracy with which such a ratio can be established will never be very close. Neither is it probable that any one ratio will be strictly applicable except to the particular sections of the country for which it is worked out. That is, the acceler- ated cycle will have to be modified to suit the climatic or ex- posure conditions that are to be simulated. The results in Fig. 39 illustrate how deterioration, as meas- ured by loss of gloss and chalking tendencies on outdoor ex- posures, compares with an arbitrarily selected accelerated ex- posure cycle. Gloss determinations were made with the Inger- soll ‘“Glarimeter.” The exposure cycle, indicated along the abscissa, was selected to give the same average ratio of light, moisture and refrigeration prevailing at Palmerton, Pa., over the period of one year. The curves given are plotted on a 1:7 ratio, which appears to fit quite closely for the paints that were put out at this time. (Exposure from March to August, 1924.) But experiments show that this 1:7 ratio will not hold if the outdoor exposure is begun at another season nor have we any reason to expect that it would. Essentially, then, all that these curves tell is that the reactions of the films to the sum total of the weathering agents (artificial and natural) as used in these experiments are very similar, even, with pigments that differ so radically in their known properties. But this, in itself, is very important as further proof of the practicability of acceler- ated weathering. The degree of chalking produced by prolonged exposure has been observed to follow the results from outdoor exposures. All results indicate that quite accurate estimates can be made of the final chalking characteristics of a paint; that is, whether heavy or light, and whether adhering or easily rubbed or washed off. Cracking types of failure are reproduced, but up to the pres- ent time no such definite time ratios can be reported for paints. There is evidence, however, that these will approximate the ob- served time ratios for loss of gloss and chalking. As for ex- 78 EXAMINATION OF PAINTS, VARNISHES AND COLORS ample, the observed ratio for cracking on a set of several var- nishes was observed to be between 1:6 and 1:7. It is interesting to note that this ratio fits the curves in Fig. 39. Other observa- tions have been given ratios of approximately 1:10. One dif- ficulty is that failures of this type are so often directly affected by slight variations in the application and differences in the conditions of the undercoats on several panels, that a very great number of observations will have to be made in order to arrive at reliable conclusions. Sources of Ultra-Violet Energy.—Practically all of the work so far reported on accelerated weathering of paint and varnish products. has' been done with the mercury arc as a light source. Convenience in handling and the important fact that the long tubes permit equal exposure over larger areas have undoubtedly been the reasons for this. But essentially, there is no reason why other sources of ultra-violet energy should not be success- fully used. For those who are satisfied to work with smaller samples on a moderate scale, the iron or modified carbon arc types will undoubtedly prove as satisfactory. The mercury arc does have a weakness in the fact that the ultra-violet transmission of the quartz tube drops as the burner is used. Flynn* reports an interesting way to compensate for this. He found it desirable to mellow the burners for about 500 hours. This was accomplished with a 220-volt burner by start- ing it at 160 volts drop in the are proper and increasing the voltage drop at the rate of 2 volts for every 100 hours of opera- tion for the first 500 hours. After this, he claims, no change is necessary during the remaining several thousand hours of the life of the burner for dye testing. It is not yet definitely known whether the radiate in ake ultra-violet have a selective action on linseed oil and other or- ganic paint and varnish materials, or if the deteriorating effect merely increases directly as the wave lengths of the ultra-violet radiations are decreased. Experiments designed to determine this are under way and more information on the subject should be available shortly. The experience of the dye industry, as shown by Harrison+ and Flynnt is that for certain dyes, which * Oscar R. Flynn—How the Mercury Are Was Made to Imitat —American Dyestuffs Reporter, Vol. XII, pp. 837-43, Nee ae ate one a ie kee ho eee Society of Dyers and Colorists, July, a en R. Flynn—Am. Dyestuffs Reporter, Vol. XII, pp. 837- 43, Nov. ACCELERATED TESTING CABINETS 19 are faded by reducing reactions, the radiations below about X = 2900 A. U. must be filtered out to obtain results comparable with sunlight exposures. This is especially true on cotton which, Flynn concludes, becomes very actively reducing under the ac- tion of radiations much below A = 2900 A. U. Accordingly, for such dyes, the arc was tempered by interposing thin sheets of crown glass. It is possible that such side-reactions might also take place in paint and varnish films, but the indications are that under the experimental conditions these are not an import- ant factor, if they take place at all. For example, preliminary experiments (28 inches from a 220-volt D. C. 30” tube, operated at 9 amperes) on paints with a series of special glass filters, which cut out the ultra-violet step by step, show that all of the gloss reduction curves under the different filters are quite similar in form, the main difference being in the rate at which the gloss falls off and surface chalking takes place. That is, filtering out the shorter wave lengths of ultra-violet light merely lowers the rate at which the deteriorating reactions progress. It should be noted that the results shown in Fig. 39 are from panels exposed without interposing any light filter. Properly speaking, however, this light exposure is already partly temp- ered, when we consider the distance from the are (28 inches) and the fact that the quartz used in the burners is not of the highly transparent grade. Possibly this choice of light exposure conditions has been a very fortunate one and partially accounts for the very gratifying agreement with outdoor exposures. But our conclusion must be that we do not yet know just how far we can go in accelerating the light exposure and still maintain a proper balance with the other factors that must enter into a complete accelerated weathering scheme. In closing, it will also be worth while to point out that the work so far recorded has not taken into account the influence of many other important, but less universal, deteriorating factors. We may mention, especially, industrial gases in combinations with light, moisture, etc. These will, of course, have to be studied and assigned to their proper places in the final testing scheme. 80 EXAMINATION OF PAINTS, VARNISHES AND COLORS Coefficients of Diffuse Reflection for Pigments at Different Wave Lengths in the Near Ultra-Violet’ Wave Lengths Measured in Angstrom Units 2c eiee. oc. 4047 3655 3131 3024 2968 Basic Carbonate of White Lead 83 78 69 65 62 Basic ‘Lead! Sulfate. 2.54..2.5: 82 60 58 57 56 A Cheating yoo. ere eh es 75 68 63 62 64 TSTHOVONG Mss ee ee eh ee 83 66 2 0 0 Titanium: Pigment..07 25a 82 24 2 0 0 Lamp: Black 22.2 es a ok 3.8 4.2 4.2 4.3 4.5 Iron Oxide (69% Fe20s) «0-2... 6 6 6.5 6.5 6.8 Chrome ) eA kee eo eee eee 745 6.206 .1611 Solvent Naphtha -(160") 0 cay es os . 902 7.514 . 1331 Grain Aloohol7: 74 hee ve ee 185 6.539 . 1529 Wood Alcoholii..4 neo s: eee ee 791 6.589 .1518 ACOLONE Ds o's OG tes, hele 2 Op Ee Teel OE 6.639 . 1506 Carbon: Petrachloride 2.4. a eee 1.60 13.328 .07502 Amy Acetate oie ef ie sate eer .874 7.280 . 13874 Ethyl Acetate: .. wah $4 oi eacce eee . 902 7.514 . 1331 ** These liquids will vary greatly in specific gravity. Grinders should determine the figure for the products they use. It should be pointed out, however, that the specific gravity of even such colors as are termed chemically pure, such for in- stance as chrome green, may vary to a great extent. This is due to the fact that these greens may contain a small or a large per- centage of blue, and in some instances varying amounts of lead sulphate. This variance in composition, therefore, of even chemically pure colors, is sufficient to warn the paint grinder that serious mistakes may occur in calculations made on average specific gravity figures of certain colored pigments. A chart is also presented showing the specific gravity and bulking values of many liquids that are used in paint and enamel manufacture. SPECIFIC GRAVITY OF PIGMENTS 89 TABLE XV—Table of Bulking Averages—Specific Gravity of Some Dry Pigments Weight One Pound Specific per solid bulks gravity. gallon. gallons. Basic Carbonate White Lead........... 6.81 56.73 0.01763 Basic Sulphate White Lead............ 6.41 53.40 .01873 Ve LAS re Cae Wins A sea eae 5.66 47.15 .02121 Zine Oxine, Leaded, 809%). ees. es 5.95 49 .56 .02018 OT OMG tre ee aes ee ee 4.30 35.82 02792 Bt ae ee ee hie i wc a 4.30 35.82 .02792 AGN Sn Sie ee See ee 2.85 23.74 .04212 Pee le Rs nee ee eee 4.45 Syem Urs .02698 CRETE ONG a ere ass Us on 2.02 21.82 .04583 Re TRS aw Lo Ring ee Oe 2.65 22,07 .04531 REY Sy eg Lg eee ee 2.84 23.66 .04227 VU ORs ee ee tees Sa Kang nk fe Dave ee Aaa 04431 *Venetian Red, (20% Fe.O3).........+- 3.05 25.41 .03935 Red Oxide, (40% Fe:Os)..........--+-- 3.45 28.74. .03479 Red Oxide, (95% Fe:Os)..........-.--- 4.95 41.23 .02425 Indian Red, (90% Fe2O3)...........--- 4.92 40.98 02440 Ferric Oxide, (98% Fe2O3)...........-- BeLD 42.90 .02331 Pelee ee ee tas, aa cs be We 3.95 32.90 .03040 STE. ON A a cae ee ea a 2.80 23.02 .04288 Sienna eta Woe ie sta ee. o's 3.27 27 .24 .03671 Pee GRt Mrs Gee ets. Sein aie 3.957 32.90 .03040 Met yl kaa or Sess ee te ne a 2.68 22200 .04480 ete AE ee ss Skee he oes 3.80 31.65 .03160 Brown Oxide, (50% Fe2O3)..... ae a 3.35 ZL LOl .03583 Mineral Brown, (45% Fe:O3).......... 3.34 27.82 .03595 yori S10 te to eek pee Ses 4.95 41.23 .02425 VETTING, °c, Bice Rae ioe re a ee en a 9.40 78.30 .01277 (rane Wierda Gees agi ee nee Ss 8.80 73.30 .01364 ee eae) ye in si eae Be 8.80 73.30 .01364 Pere BE Oe ONet Serta tae 8 ae a Ek gs ae 1250 12.50 .0800 Para Red 10% (on Lime and Barium Base) 2.65 22.07 .04531 Pure Toluidine Red Toner............. a 49 12.41 .08058 Tel orien a 5 1a Coe an ee ar { as hel oCa( VINE iS oie uh payee eee BETS 22.91 .04365 PCPTO CI GTORIG iss. o's ok eet Ve 2.80 23 .32 .04288 PC Go ree. ee ns 2 ie os lela ke 1.85 15.41 .06489 it eramarine WIG cans Fe oc se ee ews 8 2.35 19.58 .05107 BU brome Velow Get 3. 5. eee et *6 00 VERA SURO, eo G GU es cue ee pe ee {278 14.83 .06743 OP y sient oil Se on a ces 1.81 15.08 .06631 Ps cr Ga hia he ve ee eal 2.64 21.99 .04548 eee ere re ek os ee G's ay ie 2.36 19.66 .05086 Weewetoueebaletas. 6. ob occ ct oe dy eS 2.701 PAE .04431 Pane ce ee os ad ep oO 7.06 58.81 .01700 PAT ORITITID UI sae cs ce wl ee Ew 2.64 21.99 .04548 ORL UIs Pele ec) oo ioe snes V vind de a ae 11.09 92.38 .01082 * These will vary widely according to composition required for shade or tone and character of base. — SS = Ty, -;” CL EXAMINATION OF PAINTS, VARNISHES AND COLORS 90 - ‘uOT[es 10d 4YZIoM OY} WoIJ pouTeyqo oq uvo osepunod 9y}4 ‘spmbry jo asepunod uvy} Joyyel eseuoles uo soyoyeq Il0y} eseq [[I4s SIOPULIZ IOq “A]PYSI[S ArvA syuouoduroo pmbiy oy} 4eVyy ydaoxe ‘suorjeuItyse A[Nq 10j s1epulid sNolwA 04 yno 4uas AT}UI00I B[NUIIO} B OF IBIS SIT] o]durexy f “poppe eq plnoys se[eg uo 4yyoIg JON SeinSy oAoqge oy} OT, ‘90}}TUIUIOD BuUNODDW 4so_g ‘poppe eq pjnoys ysoD Ar0yO¥y I9AO dd1Ig SUITJeg Sainsy sAoqe oy} OT, jo y10dey 909 “‘peppe oq plnoys sysop Sulinjyovjnuvy soinsy saoqe oy} OT, EME eR Pea ne ace “*"**pappe oq plhoys seseg pue suByD jo 4s00 samnZy 9Ao0qe ay} OJ, ‘OpBul oq p[NoYs sso] SUIpULIyH pue 9[14BIOA IO} UOIJONped seinsy sAoqe oy} WOL oF i'n were wena BF Ce wg Ca Wee his, 4 gta, Welw wy a Sieh eo “uoT[ea iod 4soo [el10}8Ul MOY ‘Sql l . 9I PCa OWES) WEN WS) ole Oth) OA Pe. e We e ee, a Re ee Sad 6 BUG wl oe ew . “uo][Bs riod AY BIO PLGQ ots A pn eR seit a banc ene payyng suojyey ‘S|¥3 FL°68 "SqI 6641 Te, Oia eee ee ear Sr TG Te ee ke peek ame pil ene ree UOINOS 1x8 CT 98° I 6FCT ‘ CL X Swi tig ee MC ee et ee ee gee ek Wee ee syiidg [eloulyy ral Cuz LOFT Z0'°8 De Sen aa te ak & rac] CT 06°F CZZI oe [IO peosury parpog OF £6°9¢ S8ZI ZOCR sy Pea: hee ties es intial des [lO poosur] AVY SEF 3 ay: LEFtO Te ra WA SES se 8 Side CNet es eee 8 ab ew i te eee ee SUIVIUM CZ CF LECkO a Ce a ea BOTS OOT 9¢°9 IZ1Z0° yo a apixO ourlz OOF Clues €Z810° ET A LO Teg de oc, = PBT OFT M e7BYdIng oiseg ¢1z% C3 PF €9Z10'0 UOC Ewe Toe Lee ee caat ae oe PeeyT SYM esBuodrey vise G21z ‘pes() spaunog 4so0g punog Jeg 4s09 suoT[ey syrng “‘suO[[ey) ‘[BILI4ZB]AY JO “‘spunog QIOAUT [BLIO4BIY QDIOAUT [RII0}VI pos esvpunog sy[ng punog 9uQ AYIABIDH ogwedg II ajduvrg “poppe oq pynoys seyeg uo yWorg YeN saimsy saoqe ay} OT, ‘poppe eq prnoys yso— A10}0¥q IOAO DOIG BUI[JEG sainsy vaoqe ay} OF, ‘907}TWIWIOD SurUNoIDW 4SOD “poppe oq pinoys sysoDM BZulmMyoejnuvy Ssoinsy vaoqe oy4 OT, Jo y10dax 909 ‘poppe oq plnoys sesey pu suey jo 4so_D soinSy a9aAoqe vy} OF, {| ‘opeul oq plNoYs ssoT Surpulsy pues a[yvlOA 10} uoTonpaq seinsy saoqe ay} Wo Svea de yURss Te ive oe he 6 Vacs, eRe Io dae lew ee heh uo][ed lod 4so0 [B110} BUL MEY “Sq c . OT oS) Oe ag (8S 66a we 8) 60s ig) Oe A, BS ON (Ol OSes 6 ONES: 6 ow lee” De See uo][es iod FU SIO MA QCO'Q ttn eee ene eee es peyyng suoypes S[es 9¢0'9 "SQT OOT 6FF LOFT ZOS,tC * BR A y& 2 “thet @ es; * i ee ae S Pa F - 2 & “: jo rd v2, y¥? “ 4 i erst een oo Tee ee Plies Ie? ¥ 2 8 mu oe w os Py: ~~ of | ee Me x as es ra ¢ vt cy FIGURE 53 FIGURE 55 American process zine oxide Basic carbonate of white lead, taken at 1,500 diameters, showing 1,500 diameters, showing the char- the characteristic crystalline out- acteristic hexagonal outlines of lines. these crystals. bois es ee * Cee FIGURE 54 FIGURE 56 French process zine oxide, 1,500 Basic sulphate of white lead diameters. There is less tendency (sublimed white lead), 1,500 here to form needles and twins diameters. There is a slight ten- than in the American process zinc dency, not well shown in the oxide. photograph, for this pigment to form cubes. FINENESS OF PAINT PIGMENTS 105 FIGURE 57 FIGURE 58 Gas Black, 1,500 diameters. Barytes, 800 diameters. Taken with 1.7 mm. quartz mona- chromat and ultra-violet light. THE MAGNIFICATION Generally, in photomicrographic work, definition of structure is the one essential quality most desired. However, as the struc- ture of a pigment particle will give us no information in regard to its size, the factor, definition, may be neglected here to a certain limited extent.* On account of this fact it has been found an advantage to employ a magnification which otherwise would be too high if the best definition is to be obtained. Never- theless, care must be taken that the photographic image of the particle gives edges sharply enough defined so as to make a satis- factory measurement possible. With a 2 mm. apochromatic objective a magnification of 1,500 diameters will be most convenient for pigments such as zinc oxide, lithopone, red oxide of iron, sublimed white lead, corroded white lead, Mathewson white lead, etc. Lower magnifications are used, naturally, with coarser materials. * But to no greater extent than is shown in the photomicrographs. 106 EXAMINATION OF PAINTS, VARNISHES AND COLORS FIGURE 59 Gardner Photomicrographic camera used for making low magnification photomicrographs of exposed test panels on racks or fences. Tripod and film pack used. CHAPTER XII. OIL ABSORPTION OF PIGMENTS In mixing a pigment and a liquid a point is reached where independent of such mechanical forces as could be developed by actual grinding, the surface of each pigment particle is thor- oughly wet by the liquid and the pigment mass becomes thor- oughly saturated. This point represents the oil absorption property of the pigment, and is expressed by a factor termed the oil absorption factor. This factor is therefore a measure of the quantity of a given oil or liquid, required to thoroughly wet all the absolute particle surface of the pigment mass. The factor is ascertained by determining the number of cubic centi- meters of liquid required to saturate 20 grams of pigment. It is then expressed as the amount required for 100 grams of pig- ment. The factor obtained by this method should not be confused with that obtained by the older method of rubbing and mulling 10 grams of dry pigment on a plate with oil gradually dropping from a burette until the point is reached when a workable paste is formed. The latter method gives an entirely different figure, more representative to the amount of oil required to grind a pig- ment to stiff paste form. The method given in this chapter gives figures more representative of the amount of oil required in what might be termed a stiff paint. Lithopone and other pig- ment makers have had difficulty in getting inspectors to use a common method that could be run in a specified manner, so that results will be reported uniformly. The method below is for that reason coming into wide use. The oil absorption of a pigment is particularly important to the manufacturer who wishes to maintain a product of uniform quality and to the user who desires such a product. For instance a user of lithopone might require for a certain paint, a pigment of a certain well defined oil absorption, in order that his product would remain uniform. If a shipment of markedly higher or lower oil absorption should be sent to him, he could discover this fact by the oil absorption test, previous to storing or using the pigment. In designing a paint the oil absorption factor is especially 107 108 EXAMINATION OF PAINTS, VARNISHES AND COLORS valuable for determining the amount of oil required to grind each pigment to paste form or the quantity of each pigment re- quired to produce a certain desired consistency. In improving al Ht sine gontecomcimoereiar Nabe tlm scrineta ss trtmtrnnemnassheen-torantemeitnech teint tliat in is f FIGURE 60 Apparatus Required for Determining Oil Absorption of Pigments. the properties of an existing paint, a consideration of the oil absorption factor is also important. Thus if it is desired to increase the consistency of a paint without increasing the per- centuge of pigment, high oil absorbing pigments may be used. OIL ABSORPTION OF PIGMENTS 109 The opposite may be accomplished by the use of low oil absorb- ing pigments. In using high oil absorbing opaque pigments, inert pigments of low oil absorption may be added in order to lessen the amount of oil required to suspend the other pigments. When it is desired to secure maximum opacity, regardless of other qualities, a low oil absorption opaque pigment may be used. If a glossy enamel-like finish is desired, a pigment of high oil absorption is indicated. The amount of oil required for pigment saturation or wetting is directly proportional to the specific surface* of the pigment mass, existing at the point of saturation. As the specific surface of the mass is relative to its degree of particle sub-division or fineness, it also measures to a great extent the fineness of the pigment. The oil absorption factor being relative to the surface conditions of the pigment is independent of its chemical com- position or specific gravity. The practical advantages of know- ing the oil absorption factor lie in the information it gives con- cerning the following physical conditions of the pigment: (a) Relative amount of surface in the pigment mass. (b) State of sub-division of the pigment particles. (c) Comparative specific surface of various pigments. (d) Variation in fineness or particle sub-division of various lots of the same pigment. The property of absorbing a given quantity of oil is relative to the specific surface of the pigment mass. Thus the difference in oil absorption and body imparting property shown by various pigments is due to the difference in specific surface or particle sub-division. From, this it follows that the variation or differ- ence in pigments in this respect exists up to the saturation point only. Beyond this point they all become uniform in the amount of oil required to bring the mixtures to a certain consistency. This fact is improtant in the comparative testing of pigments in liquid paints. The following is illustrative of its application. If a series of pigments are ground into pastes on the basis of the individual oil absorptions of each, and the same amount of thinning mixture is then added to the same weight of each * It is believed that the oil absorption of a pigment may be reduced by compacting. The small particles would then form aggregates and the specific surface would be reduced, thus reducing the oil absorption. Sim- ilarly, by effecting electrical changes in the particles to cause a coalescence or by effecting a change in the surface tension of the particles, a reduc- tion in oil absorption might be accomplished. 110 EXAMINATION OF PAINTS, VARNISHES AND COLORS TABLE X VI—Oil Absorption Factors on Some Pigments Low-Oil High-Oil Average Pigment. _ Absorption | Absorption Type. | Type. Type. Basic Carbonate White Lead........... 15 22°09 “= 1a Basic Sulfate White Lead.............. 26 32 30 PIO ORGS aria ene eh ahem Ae array ee 47.6 54.1 52 Titangx.. tee wae kase SUR eae ots 22 28 26 token Reeth eles rhs LOR goa AO eee | Gea | 31.3 36.5 32 LAthOpones Pier noe ae A es) Gee 22.75 38.5 33 Aslestine wa. coh; fa 'ae eect ea keer. neem 32 50 50 Bargies. 607 oi a is ae ee cae ee . 13 15 13.5 Blavie Vixens. ee ee ae eee | 23 36 30 CBiria clay bre it oes ae ee ce ase ee | 41.5 53 51 CY DRUIN ace acetal ear es ae | 26 35 33.9 Pilied. (Crveta line ss coc mae at reas . 20 28 “eo SBS silice LAmorphousjied..-0. 04 28 be awa . 30 38 32 Trade passa clones! Oi a ee ew Gate eae 40 65 60 Wihitino cn ik + eee ee ee eee . 28 35 32 dry pigment in its paste form (pigment plus oil required to saturate), the resulting mixed paints, barring thickening due to any chemical action, will be of practically the same con- sistency. 7 Considerable information is also obtained by studying the condition of the pastes at the oil absorption point. A very considerable difference will be noted in the characteristics of the pastes produced by various pigments. Some pastes will be short and tough. Others will be long, stringy and soft. Some will have a high gloss. Others will present a dull appearance. Some of the pastes will be dense, requiring heavy pressure to flatten them out. Others will be soft and easily spread. The amount of oil absorbed does not entirely control these factors. In other words, two pigments of practically the same oil absorp- tion may yield entirely different types of pastes. For example, one may be dense and the other soft. These physical charac- teristics all indicate certain pigment qualities. The oil absorption point varies with different pigments and is influenced by certain conditions. A pigment in its dry state consists of individual particles and agglomerates of particles. | The particle surface and the mass particle surface combine to make the absolute surface existing in a given volume of the pigment. As the amount of oil required to saturate a certain amount of pigment is the amount required to wet the absolute OIL ABSORPTION OF PIGMENTS Tit particle surface, any influence which tends to change the sur- face content (by changing the specific surface) varies the oil absorption point. Two common influences accomplishing such change are found in the dispersion effect of certain vehicles, and the effect of mixing and grinding pressure. While these influences are always present to some degree in all paint mak- TABLE XVII Raw Linseed Oil Soya Bean Oil Colloidal Condition Oil Pigment. Oil Ab- | Character | Oil Ab- | Character | Oil Ab- | Character sorption of Paste. | sorption! of Paste. | sorption of Paste. Factor. Factor. Factor. Zine Oxide....... 54 Smo. = 9a Same as | 56.5 | Glossy. Glossy. with Smeary. Quite Linseed Quite long. Oil. rubbery. Leaded Zinc 30.0. |) solt, 35:5 | Same as 39 Quite Oxide (35%). with glossy. Linseed Smeary. Oil. Rubbery. Slightly granular. Lithopone (High | 37.5 | Short. ot Same as 38 Fairly Oil Absorption). Chalky. with glossy. Smooth. Linseed Long but Oil. not tough. Slightly granular In appear ance. 3 Lithopone (Low | 25.5 | Soft and 23.5 | Sameas , 26 Very soft. Oil Absorption). Long. with Runny Fair gloss. Linseed and Contains Oil. smeary. large Good lumps. gloss. Lumpy. ing procedure, the basis of the oil absorption factor should be the condition of the pigment in its dry form with the elimina- tion of these influences to as great an extent as may be pos- sible. The oil absorption factor of all pigments is changed to the same relative degree by the introduction of these influences to an equal extent. Certain oils and liquids, due to surface tension phenomena 112 EXAMINATION OF PAINTS, VARNISHES AND COLORS or to such colloidal conditions as effect adsorption or develop- ment of great surface, tend to cause either a coalescence of the pigment particles into particle agglomerates or by their dis- persion effect, to break down the existing agglomerates and dis- perse the particles into an extremely fine state of sub-division. Either of these conditions change the specific surface of the mass and accordingly change the oil absorption point. This variation in oil absorption with different oils is illustrated by the follow- ing table, which gives the oil absorption factor of several pig- ments in linseed oil, in soya bean oil, and in a liquid having a relatively high colloidal viscosity but with an apparent viscosity approximately the same as the other two. Selection of Test Liquid.—In view of the results shown in the above chart it is important that the oil used for determin- ing the oil absorption factor be one that will have the minimum effects in causing either a dispersion or coalescence of the pig- ment particles. In such a vehicle the pigment tends to form a mechanical suspension or mixture only. Thus the degree of particle sub-division or agglomeration existing in the dry pig- ment is retained to the greatest extent. Of the common and available oils, raw linseed oil is the best suited for the pur- pose. With most pigments it has but little dispersing or coalesce: — ing effect. It is therefore used as the standard vehicle for de- termining the oil absorbing property of a pigment. If, however, it is desired to determine the oil absorption factor with certain other liquids, the results will be relative to the dispersing effect of the liquid used. In following the standard procedure a well settled Raw Linseed; Oil, clear and free from foots and having an acid value of from one to three should be used. An oil of this kind is readily obtainable and easily kept. A, variation in the acid value of the oil affects the oil absorption point; the amount of oil required increasing with an increase of the acid number. This difference is due either to a greater particle dis- persion or to a thickening caused by the formation of soaps. It is important, therefore, that in making determinations where very accurate results or close checks are desired, that the oil used be always of the same acid value. ; Effect of Moisture on Test.—The moisture contained in the pigment, between certain limits, seems to play no important part in the determination, since check results may be obtained on portions of the same sample of pigment whether air dried, oven OIL ABSORPTION OF PIGMENTS 118 dried or even slightly moist. Therefore, the ordinary air dried sample of commerce is in a satisfactory condition if it does not contain sufficient moisture to cause it to mat together or cake. The temperature of the relatively small amount of oil used during the operation is not important, because the oil is im- mediately cooled by coming in contact with the much larger mass of pigment. This statement is made with the assumption that the oil is of the temperature prevailing in the ordinary laboratory. When, however, the pigment is quite warm, the oil absorption is slightly decreased. This is due to the fact that the viscosity of the oil is decreased by rise in temperature and con- - sequently the thickness of the film with which it wets the particles would be decreased. However, the difference between 70° and 100° Fahrenheit, which is the average range of a laboratory, is very slight so that the temperature need not be taken into consideration except during extremes in either way. Principles to be Observed in Test.—The principle of this test is that of effecting the wetting of all the “particle surface” or “narticle agglomerate surface” of the pigment mass without the application of mixing or grinding pressure. This is accom- plished by certain oil addition and stirring procedure as de- scribed herewith. In all stirring operations, care must be taken not to cause mixing of the pigment and oil by applying pressure, as this factor will tend to vary the results. All stirring and mixing should be done very carefully and lightly. A finger and wrist motion is all that should be used, allowing the forearm to rest quietly. When the oil first comes in contact with the pigment, a cor- responding amount of particle surface is wetted. The particles thus wetted then coalesce or cling together and form agglo- merates or lumps of paste consisting of oil and pigment. These small lumps of paste should be kept distributed through the mass by stirring. As the absorption of oil by the mass increases these lumps will mat together, forming larger lumps or. balls of paste. With further absorption of oil by the mass, these larger lumps or agglomerates of oil and pigment paste will coalesce ‘and with most pigments will form one large ball. (With a certain few pigments this large ball is not formed; the separate smaller lumps remaining separated.) After this point is reached a small amount of dry pigment may still be left around the bot- tom and Jower parts of the container. This pigment is wet by 114 EXAMINATION OF PAINTS, VARNISHES AND COLORS bringing it in contact with the free oil existing on the surface of the large ball or lumps of paste. The end point of the de- termination is reached when all of this dry pigment has been taken up and wet. This point is indicated by the following con- dition. While any dry unsaturated pigment still remains, the paste will not smear on the glass. At the point, however, where all of the pigment particles are wet, the paste becomes soft and will smear on the sides and bottom of the container.* The balls of paste may then lose their rigidity and tend to flatten out or lose their spherical form. This point, which is very sharp, oc- curs within narrow limits and is the end point. The apparatus required and method of test are given below. Burette.—A standardized burette should preferably be used. If not standardized, the determinations should always be made by starting with the same burette filled to the zero point. In this way possible differences due to variations in the burette graduation are largely eliminated. Container for Mixing Pigment and Oil.—For this purpose a smooth, round bottom jelly glass is very well suited. Those having dimensions of approximately 214 inches diameter at top, and 314 inches deep are easily obtainable. Flat bottom glasses or those having fluted sides or bottom should not be used, as the pigment and paste tend to collect in the crevices, making ac- curate determinations difficult. Spatula.—A blunt end, 4 inch, stiff blade spatula should be used. If the blade is too limber, excessive stirring is required and the results are liable to vary. Preparation of Sample.—The sample to be tested should first be placed in a suitable container (a small wide-mouth bottle is adaptable) and well shaken so as to assure the elimination of any packed particles or lumps. This is especially important if the pigment has been packed in barrels or otherwise kept in a manner that is liable to cause it to pack together. If excessively moist, the sample should then be air dried at room temperature. Procedure.—Twenty grams of the pigment are placed in the glass. The oil is then run in from the burette, either drop by drop or with successive small additions. Either of these methods will give check results. If the drop method is used the rate of flow at the start should be about one drop per second. If the * See Fig. 61. OIL ABSORPTION OF PIGMENTS 115 small addition method is used, quantities of 1% cc. should be added. As the absorption of the oil increases, the rate of flow or quantity of the additions is decreased. This is fully ex- plained later. The oil is run in so as to strike the dry pigment in the center. As the oil comes in contact with the pigment, the dry pigment that has not been wet should be lifted from the outer edge and placed over the oil so as to bring all the oil sur- face in contact with the pigment. This is best accomplished either by lifting it up on the spatula and dumping it off on the oil, or very lightly throwing it over the oil. When the pigment particles become wet with the oil they tend to coalesce and form small lumps of paste. These lumps should be kept distributed throughout the mass. This is done by lightly stirring the mixture of these paste lumps and dry pigment in the manner of stirring described above, being careful not to use pressure in the mixing. If the drop method of oil addition is used this stirring should be carried on continuously with the operation of bringing the dry pigment in contact with the oil surface. If the successive addition method is used this stirring should be done after each addition. As the absorption of oil progresses these lumps of paste, by taking up more pigment and matting together, form larger lumps which when stirred around form balls. When this point is reached the rate and quantity of the oil addition should be very much decreased and only a few drops added at a time. In adding the oil at this point it should be allowed to strike on these lumps and not on the re- maining dry pigment. After each oil addition these lumps are lightly stirred around so as to bring the oily surface into con- tact with the remaining dry pigment. With further oil addition and stirring, these balls will with most pigments join together and form one large lump, with but little dry pigment remaining. With certain pigments, however, the lumps or balls of paste do not join together but remain separate and continue to collect more pigment. At this point, which is close to the end point, the oil is added very carefully, one or two drops at a time. With many pigments one drop is sll that is necessary to establish the end point. At this stage, the oil should be allowed to strike on the surface of the lump or lumps. They should then be worked around so as to pick up more of the pigment. When all of the remaining dry pigment has been picked up and wet, the end point is reached. This is 116 EXAMINATION OF PAINTS, VARNISHES AND COLORS indicated as above explained by the paste lump becoming much softer and easily spread with the spatula. When stirred around it smears on the sides and bottom of the glass. This end point is very sharp and occurs within narrow limits. With most pig- ments only one or two drops of oil is required to change the relatively hard dry lumps which do not smear the walls of the container into a fairly soft paste which will smear when stirred around. If, when the end point is reached, the paste lumps are broken down or spread with the spatula, it will be noted that the oil is uniformly distributed throughout the mass and no dry pig- ment remains. Different pigments have certain individual characteristics in absorbing oil. These must be given consideration, and it is sometimes necessary to slightly modify the procedure in order to conform with these peculiarities. For example, some pig- ments absorb the oil readily and in a uniform manner, while others take up the oil slowly. The paste lumps of some are smooth and free from hard agglomerates and are easily kept uniformly mixed. Others tend to form hard lumps. With such it is difficult to keep the mass uniform. When the end point is reached with certain pigments, the paste lumps will be quite firm. Other pigments will be firm up to the end point and then suddenly become very soft; in some instances of semi-paste con- sistency. These differences are largely due to certain surface tension relations of the pigment and oil, a discussion of which is outside the scope of this paper. A little experience with the various pigments will enable the operator to effect such modifica- tions as will be necessary to conform with these conditions. Close checks can be obtained on the test made in accordance with the procedure explained above. Experienced operators rarely vary more than 0.1 cc. in check tests or in tests conducted by different operators on the same sample. For ordinary pur- poses a variation of 0.2 cc. is sufficiently close. A variation of more than this amount on check tests can only be considered as an error in the operation. In testing new pigments or where a close determination is desired, two or more check tests should be made. A little experience and a consideration of the follow- ing previously stated precautions is sufficient to insure accurate results: (a) The pigment must not be moist. OIL ABSORPTION OF PIGMENTS key (b) It should be well shaken before making the test. (c) It should not be of a temperature lower than 70° or higher than 100° F. (d) The oil should be well settled and of a standard acid value. (e) The oil should not be added too fast, nor should it be added slower than is necessary. : (f) The mixture should only be stirred enough to keep the mass uniform and bring the pigments in contact with the oil. (g) Excessive stirring tends to lower the result. _ (h) The stirring should be done lightly and care taken not to use pressure or endeavor to mix the pigment and oil by this means. (i) When nearing the end point, the oil should be added slowly and in small amounts (one or two drops at a time). FIGURE 61 Pigment Mass Just Before Pigment Mass at Point of Satura- Point of Saturation. Mass is tion. Mass Loses Its Spherical Form Spherical and Does Not Mark and Smears Glass. Glass. ; CHAPTER XIII. TEXTURE OF PIGMENTS The property of many pigments to readily disperse and be- come finely divided when mixed with a liquid, even without grinding, is due to a quality termed “texture.” This term is used to designate the structure of the pigment, and bears no relation to its fineness. As there has been some confusion among paint manufacturers regarding the application of the terms of “texture” and “fine- ness,” the following definitions and discussion are given. A comparison of them will serve to show their proper application and import. Fineness.—“Fine. Consisting of minute. particles, grains, drops, flakes, ete.” (Century Dictionary.) And its opposite characteristic, “Coarse. Coarse-grained, consisting of large particles, fibres or constituent elements.” (Century Diction- ary.) From the above definitions it is apparent that the terms “eoarse” and “fine” refer to the extent of the subdivision of the — particles constituting a mass. They are quantity terms and are subject to the determination ‘of degree of either property by measurement of the size of the particles. The terms “hard” and “soft? (which are the attributes of texture) are quality terms and relate to the character of the mass or of the particles of which it consists. They are in this sense relative terms and as such are determined in degree by comparison and by such means as will indicate differences sharply. Fineness, then, relates to the degree to which the particles - have been subdivided, and texture to the character of the par- Texture—“Texture. By extension, the peculiar disposition of the con- stituent parts of any body—its make, consistency, etc.; structure in gen- eral, as the texture of rocks, the mode of aggregation of the mineral sub- stances of which rocks are composed. It relates to the arrangement of their parts viewed on a smaller scale than that of their structure. The texture of rocks may be compact, earthy, granular, scaly, slaty, etc.” (Century Dictionary.) And the attributes of texture: “Hard. Solid and firm to the touch; firm in substance and texture, so as not to be readily altered in shape, penetrated, or divided; so constituted as to resist com- pression, penetrating, dividing or abrading action; opposed to soft.” 118 TEXTURE OF PIGMENTS P19 ticles, independent of their size. As applied to pigments, the important properties and the most desirable from a general paint-making standpoint are maximum fineness and soft texture, although there are certain exceptions to this, such as the use of hard pigments in wood fillers and in small amounts in certain mixed paints. From this it will be seen that pigments of equal fineness may differ greatly in texture or of similar texture may vary in their degree of fineness. Closely related to the texture of a pigment are, ease of grinding, character of finish, settling and hardening in the package, and to some extent flowing and spreading of the paint. A pigment of soft texture disperses more readily, grinds more easily, produces a smoother finish, has less tendency to settle and harden, and makes a better flowing and spreading paint, than one of hard texture. The test described herewith for determining the comparative texture of pigments has been widely used by certain manufac- turers and found valuable as a method for setting standards and in investigation work. It is based on the extent to which pig- ments under certain conditions will disperse in a liquid having good dispersing properties. The liquid used is a mixture of equal parts by volume of blown linseed oil of a specific gravity of approximately .945 to .950 and pure turpentine. This mix- ture should be of slightly higher viscosity than raw linseed oil. If on account of age or storage in open tanks the blown oil has become heavy, a further addition of turpentine should be made so as to bring the mixture to the proper consistency. It should be strained through silk or very fine cloth before use. Apparatus Required.—Ground or frosted glass plate about one foot square. Several clear glass plates 4” x AUT OYGA x: 6, Three-inch glass muller. Artist’s spatula (4” blade). Small spatula. 50 cc. beaker. It is important that the small glass plates be thoroughly washed with soap and water, and then with aleohol so as to remove all dirt and grease from the surface. If a soft cloth is used for drying the washed glass, it should be first washed in alcohol, and dried, so as to free all loose particles of lint. Method of Making Determination.—12 cc. of the liquid de- eee ee (Century Dictionary.) “Soft. Yielding readily to pressure, easily pene- trated; impressible; yielding; opposed to hard; easily susceptible of change of form.” (Century Dictionary.) 120 EXAMINATION OF PAINTS. VARNISHES AND COLORS scribed are used with from one to two grams of pigment. The amount of any pigment used depends on its oil absorption. With high oil absorbing pigments such as zinc oxide, high oil absorp- tion lithopone, asbestine, china clay, and similar pigments, one gram is sufficient. With medium oil absorption pigments, such as low oil absorption lithopone, whiting, silica, etc., one and one- half grams are used. For pigments of low oil-absorption, such as basic carbonate or basic sulphate white lead, barytes, etc., two grams are used. As the test is only qualitative and largely comparative, a closer calculation than the above, based on oil absorption, is not important. The pigment is mixed to a thin semi-paste on the ground glass plate with about 1 cc. of the liquid. This paste is then well rub- bed out with the muller in three mulling operations for one minute each. This is done by mulling the paste continually for one minute, then scraping it up to a pile on the plate. This operation is carried out for the third time. The purpose of this mulling is to break down the particle agglomerates of the pig- ment and to cause each particle to become wet with the liquid. A light pressure in mulling, sufficient to thoroughly rub out the paste, is preferable to a heavy grinding pressure. It has been found that mulling to the extent stated is sufficient to practically eliminate any variation in results, although further mulling, even with more pressure, does not materially affect the results. Between each mulling operation, a few drops of the liquid should be added in order to compensate for evaporation or thickening condition. After the mulling is completed, thin the paste with a further amount of the liquid and transfer to the beaker. Add the bal- ance of the liquid, and stir thoroughly. Let stand for one or two minutes to eliminate the air. Then pour the mixture on a clean glass plate, holding the plate in an almost vertical position and pouring the paint across the upper portion so that it will flow down. Place the plate in a vertical position so that the excess will drain off. It should be left in this position until the film is dry. In this test the pigment particles of soft texture will become so finely divided that they are either colloidally dispersed or so finely dispersed as not to be visible to the eye. The harder particles which have not been finely dispersed show up. As the TEXTURE OF PIGMENTS IRA: FIGURE 62 Photomicrograph of paint of good texture flowed on glass. Note fine particles. segs oat Pte Sot eres FIGURE 638 Photomicrograph of paint of poor texture flowed on glass. Note coarse particles. 122 EXAMINATION OF PAINTS, VARNISHES AND COLORS mixture flows down the plate, the smaller particles remain at the top in the thinner part of the film while the larger particles as well as pieces of lint and dirt flow down to the lower part of the plate and can be easily observed in this portion of the film. Interpretation of Results—Some pigments disperse easily and to a great extent, while others contain many small and a few large particles which do not readily disperse. Others contain a majority of large particles. A comparison of different pigments or different lots of the same pigment will serve to show their character in this respect. Liquids also vary in their dispersing property. Some will disperse pigments to a greater extent than others. Certain liquids may with certain pigments have the opposite effect—that of causing some pigment to agglomerate and form large, hard particles. This test may therefore be used to determine the relative dispersing properties of paint liquids. For this purpose any one pigment may be tested with several liquids in the man- ner described, and comparisons made. CHAPTER XIV. TESTING THE LIGHT-RESISTANCE OF LITHOPONE EFFECT OF ACIDITY OF VARNISH AND OIL The darkening and discoloration of lithopone, due to the ac- tion of ultra-violet rays in sunlight, have in the past constituted a serious drawback to the use of this pigment in paints and enamels. During recent years, however, continued research on the part of lithopone manufacturers has resulted in the develop- ment of much more light-resistant products, as well as great improvement in other qualities. at A ra The light-resistance of lithopones has been the subject of numerous investigations. There.is much difference of opinion among the investigators regarding the nature of the change and the causes of it. The present chapter, however, is limited to a discussion of methods for testing light-resistance. Other physi- cal properties of the samples tested, such as oil absorption, fine- ness, livering, etc., are treated elsewhere. The comparative light-resistance of different samples is readily determined on clear days by exposing them in a suitable liquid, on properly mounted panels, to the. sun’s -rays. _Fre- quently, however, atmospheric conditions are such that sun tests cannot be carried out. Moreover, the intensity of the active rays and the relative humidity of the atmosphere varies greatly at different times and in different localities. It is therefore high- ly desirable to have.an artificial light source from which the ultra-violet-radiation can be maintained constant and which has actinic effects similar to sunlight. Humidity, temperature, and other variable factors should be under COMPO 2) =: i: The quartz mercury vapor arc has been ‘extensively used for testing the light resistance of paints, pigments, and dyes; and is a standardized piece of apparatus.. As a means of making eontrol tests in lithopone manufacture, it has been found: very practical. More recently the iron are has been’ adapted for this purpose. It is believed that the iron arc, when properly con- structed and fitted with the necessary devices for regulating and controlling the current, will also prove satisfactory in paint and varnish plant laboratories for certain types of work. It can be readily constructed at a very reasonable cost and produces a 123 124 EXAMINATION OF PAINTS, VARNISHES AND COLORS light practically constant in the intensity of the ultra-violet radi- ation. The chief advantage of the mercury vapor lamp is the large area of the light source which permits of the testing of large samples or a number of small samples at the same time. However, the proportion of ultra-violet rays transmitted through the quartz tube of the mercury lamp decreases continuously with age (see Scientific Paper No. 330, U. S. Bureau of Standards). Before describing the results obtained in our investigation with the iron arc, there is presented herewith a paper on the testing of lithopone, submitted to the writer by Messrs. Breyer, Nelson, and Farber. They point out the usefulness of the quartz mercury vapor lamp as against the iron arc, and refer exten- sively to the testing of all samples of lithopone in the paint liquids in which they are to be applied in the form of paints. The information they transmit regarding the effect of high versus low acid oils upon the darkening of. lithopone is of ex- ceptional importance. Inight Resistance Test for Lithopone-—A sample of three grams of the lithopone is rubbed down to a stiff paste in one part of China wood oil vehicle (a common type of China wood oil—rosin combination vehicle con- taining lead dryer) and one part naphtha. (Always make the test in the vehicle in which the lithopone is to be used, or at least in a vehicle of the same type and properties as the vehicle to be used.) The mixture of oil with thinner is freshly prepared for each set of tests. The paste is spread on a porcelain plate or pal- ette in a smooth, even layer, at least one inch by three inches in area. A standard, or standards, should be run with each set of samples, all being prepared in the Same manner. Care should be taken that the pastes of all samples are approximately of the some consist- ency. If paints are tested use the paint as it comes from the can. The palette is put in a warm place and the pastes dried until the glossy surface disappears. (In case the testing is done in a vehicle yielding a gloss surface. such as a gloss white paint, dry until the surface will stand being submerged in water.) A strip of opaque black paper or a rule is laid across and above the samples to shadow a portion, and the samples are then exposed to the ultra-violet light under a thin layer of. water 1/32” to 14” deep. (Exposure under water in- sures a uniform relative humidity.) A desirable LIGHT RESISTANCE OF LITHOPONE length of exposure to bring out significant differences in lithopones is five minutes at a distance of twelve inches from the light, when the current is 4 amperes at 180 volts across the line. Description of Light Used for Testing.—The light source found to be most satisfactory for laboratory testing is the Standard Uviare Laboratory Outfit, manu- factured by the Cooper Hewitt Electric Company, shown in Fig. 64. This equipment is furnished for either 220 volts direct current or 110 volts alternating current. So far it has been considered superior to 4 a. BN d ee | aA Detail showing : burner holder with Uviare Laboratory Outfit. Composite horizontal type showing two positions of hood. burner in position. FIGURE 64 125 126 EXAMINATION OF PAINTS, VARNISHES AND COLORS other forms of equipment for routine tests on account of its simplicity of operation, being practically self- regulating. . The details of the burner and holder are also shown. The burner holder is universally adjustable in all planes and will take either the vertical or the horizontal type of burner. The useful life of a quartz burner has been fctina by experience to be from 1,000 to 1,500 hours of steady operation, and a new burner can easily be substituted. In practical laboratory test work this provides an amply uniform source of light. A burner in use at the time this is written has been used for testing dozens of | Ultra Violet Light. — FIGURE 65 (A) Uviare light test on seven Lithopones. Time, 5 minutes. LIGHT RESISTANCE OF LITHOPONE samples daily for 114 years and is still considered useful. Also, since in any case all tests are run against a standard, the behavior of the standard quickly indicates any falling off in the effectiveness of the quartz burner. Uviarc Tests Comparable with Sunlight Tests.— Experience has already proven that tests carried out in the above manner are comparable with sunlight tests, and are a true indication of light resistance. This is also demonstrated by the photographs in Figs. 65 and 66. In these tests seven different lithopones of varying light resistances have been submitted (a) to ultra-violet FIGURE 66 (B) Sunlight test on seven Lithopones. Time, 2% hours. 127 128 EXAMINATION OF PAINTS, VARNISHES AND COLORS ds A wah ae fi t %) ai a i ae} Vay) was a % 5 a at hs : P. iE . 7 co ones * a, ei Cy as a a) tak Cece 43 5 | Mole > ae A? oo t light, as described above for five minutes, and (b) to bright sunlight for 214 hours (sample under water). It will be seen that in each case there is perfect agree- ment in the relative light resistance of the lithopones. Humidity Must be Controlled During the Test Period. —It is a well-known fact, as indicated by the literature on actinic effects, that the presence of moisture in- creases the rate at which chemical changes are pro- moted by ultra-violet radiations. This is true of the darkening of lithopones. It is, therefore, very im- portant that all comparative tests of this nature be con- ducted under known and reproducible humidity condi- tions. Since any condition short of complete saturation is not easily maintained constant or reproduced with- out special equipment, the simple expedient of im- mersing the samples in water is the most reliable means for eliminating the humidity variable from the test. We would also point out that testing under saturated moisture conditions has the further advantage that the lithopone is being tested under the most trying condi- tions it can ever be required to meet in practise. Effect of Vehicle on Results of Light Resistance Tests.—Under the foregoing description of the test method it was also suggested that the vehicle is an im- portant factor in the results of light resistance tests and that tests on lithopones intended for paint purposes should be made in a practical paint vehicle. A number of lithopone users have insisted that water or glycerol pastes should be used in testing for light resistance. From every standpoint this is wrong, unless the lithopone is actually to be used in water or glycerol vehicles. That such a method is fundamentally wrong and misleading is amply demonstrated by the tests in Fig. 67. In Fig. 67 the original lithopone is rubbed down in (1) regular flatting oil test vehicle (2) water and (3) glycerol. There is no agreement in the results and, obviously, only the test in the oil vehicle can be accepted as a criterion for lithopones to be used in oil paints. Further, the use of water and glycerol pastes may lead to extremely erroneous conclusions about improve- ments in the quality of lithopones. Lithopones can easily be “doped” so as to vary their light-resisting properties. In Fig. 67 the same lithopone has been so “doped” and tested in (4) flatting oil vehicle (same as above), (5) water and (6) glycerol. It is important to note that while this lithopone now shows perfect light resistance, in both water and glycerol pastes, 5 et Sr nan LO eS ee i 2 mar iin > ne ee aed eer. Se PRE TS ala BR es nt F Vey a. a9 > os t LIGHT RESISTANCE OF LITHOPONE TLignt Resistance test. Exposeca to Ultra Violet Light for five(5)minutes, Orignal _ -Rubbed in oi] 4F Treated Rubbed in oil. Treated Rubbed in Water, FIGURE 67 Comparison of light resistance tests on the same Litho- pone in (1 and 4) oil vehicle (2 and 5), water, and (3 and 6) glycerol. there has been no improvement with the flatting oil vehicle. Therefore, it would be a mistake to say that the quality of the lithopone had been improved. Preferable to Test in Same Oil Vehicle as Used in Practise.—The light-resistance properties of lithopones are also affected by variations in the properties of the 129 130 EXAMINATION OF PAINTS, VARNISHES AND COLORS oil vehicles themselves. Fig 68 illustrates how very important this factor may be. A single lithopone was tested in a series of vehicles typical of the principal oil products on. the market. (In these tests the oils have FIGURE 68 Acid Acid No. No. 1. Raw Linseed Oil. .................... 8. Standard Acid Refined 2. Improved Raw L. Oil............ 5—7 Linséed O1tl..... 2 eeee 4—6 3. Alkaline Refined Varnish 9. White Acid Refined Oil... 6.5 0 5 | MAR ESS git ON eee 12 Pa 3.0 10. Pale Grinding 4. Alkaline Refined Oil............... 0.5 “11. Boiled On =a 5. Alkaline Refined Oil Re- 12. Kettle. Bodied friverated ico. eee 0.5 13. Blown Bodied Oil .................. 7-10 6 Alkaline Refined. Oil.............. 3.0 14. Boiled. Oil 22222 5-7 7. Acid Ref. Oil Refriger- 15. Treated China Wood Oil... 5-6 po MR ae caeiechiineoat: Ree oe 10 | Light Resistance test on a Lithopone in various oil vehicles. LIGHT RESISTANCE OF LITHOPONE been thinned with volatile so as to dry to a semi-flat surface.) Very few of the results check one another. If we consider the results further, we find that, gen- erally, the important determining factors appear to be the acid number of the vehicle, and whether the oils are acid or alkaline refined. The presence of acid ma- terials apparently increases the light-resisting prop- erties. FIGURE 69 Test further illustrating effect of vehicle treatment on the light resisting properties of a Lithopone. Fig. 69 presents still further evidence that effects of changes in the properties of oils, which are brought about in the process of manufacturing, must be serious- ly considered as factors in choosing the vehicle in which to conduct light-resistance tests. This effect of increased acidity is also illustrated in Figs. 70A and 71B (A) and (B). (A) shows the ef- fect of increasing acid numbers from 1.0 to 20.0 in an 131 a Mes 0 EXAMINATION OF PAINTS, VARNISHES AND COLORS Acid Number 1,0 Acid Number 5,9 Acid Number 10,0 cine. ee Acid Number L5.0 Acid Number 20,0 . FIGURE 70 A 70 (A) Alkaline Refined Linseed Oil. alkaline refined linseed oil. The acidity was increased adding linseed fatty acids. (B) compares a treated China wood oil vehicle with a series consisting of in- creasingly acid raw China wood oils. Fatty acids of China wood oil were added to increase the acidity of this vehicle. That commercially used flatting vehicles might differ very widely in their influence on the light-resistance properties of a lithopone, follows as a natural deduc- tion, from what has just been said. But this is more forcefully demonstrated as an actual fact by the tests with two flat wall vehicles illustrated in Fig. 72. In this case:vehicle (A) probably is a combination of linseed oil with some China wood oil. The acid number of this vehicle averages about 13. Vehicle (B) is a straight treated China wood oil vehicle having an aver- age acid number 5-6. All of the tests just presented suggest that certain precautions must be accepted as essential in making re- liable comparative light-resistance tests on lithopones, WAZ: (1) Always run the test lithopone sample against a standard or standards. — LIGHT RESISTANCE OF LITHOPONE 33 PE: pave. Sale | Added Fatty Acids to Raw Ch “Wt Leds Reset the, ingrense i Ww the light resistance... cules 1 Treated China Wood 1 Raw China Wood Oil, A.N.4.0 G oy 10, is Acid Number 15.8 5 Acid Number 20.0 #1 #2 FIGURE 71 B 71 (B) China Wood Oil Vehicle Effect of increased acidity of vehicle on light resistance of a Lithopone. (2) The humidity conditions must be maintained constant if different tests are to be considered at all comparable. (3) The test vehicle must be of the same type and similar in properties to the vehicle used in practise. (4) Watch the test vehicle for any variation in properties. This refers to variations in acidity, especially. The results given in the following pages were obtained with an iron arc which was designed, in its original form, by Dr. A. H. Pfund.* The intensity of the ultra-violet radiation varies with the current passing through the arc. It is therefore neces- sary that the amount of current be properly adjusted by insert- ing a variable resistance in the line. The length of the arc must be readily adjustable so that the proper potential across it may be maintained. It has been found that the arc constructed as * Astro-physical Journal, Vol. 27, p. 296 (1908). 134 EXAMINATION OF PAINTS. VARNISHES AND COLORS “S/li/er, FIGURE 72 Difference in the light resistance of a Lithopone in two commercial flat wall vehicles. (A) Probably a combination Linseed Oil-China Wood Oil vehicle. Acid Number 13. (B) A treated China Wood Oil vehicle. Acid Number 5-6. described herein burns best at a current of five amperes with a potential of 40 volts between the electrodes. H. E. Eastlack and J. E. Booge have done much toward the development of a standard light-resistance test. An apparatus similar to that constructed by them was used in the present work. LIGHT-RESISTANCE—IRON-ARC TEST Submitted by H. E. Eastlack and J. E. Booge a. Principle of Method.—The sample of lithopone in the form of a water paste is exposed under a quartz cover glass to the action of a standard iron arc, at a distance of 10 cm. A portion of the sample is covered with opaque material. The time required to produce the first appearance of daikening, as indicated by a LIGHT RESISTANCE OF LITHOPONE 135 FIGURE 73 Diagram of iron arc equipment used in our work. faint but definite line of demarkation between the ex- posed and unexposed portions of the sample, is taken as a measure of the light-resistance of the sample. b. Apparatus and Materials Required: Iron arc with voltmeter, ammeter and rheostats. Sample holder with an optically clear disc of native quartz crystal (30 mm. dia. x 1.56 mm. thick) .f Comparative tests by three different laboratories (see below) indicates that exact adherence to the specifications for the quartz disc is important. 136 EXAMINATION OF PAINTS, VARNISHES AND COLORS Spatula—hard rubber, small. Beaker, 50 cc., or glass plate for mixing paste. Distilled water. c. Procedure: 1. Preparation of Sample—Put 3-5 g. of the litho- pone into a 50 cc. beaker (or on a glass plate), and about 2 ec. of distilled water, and with a small rubber spatula mix the water and lithopone in such proportion that a smooth, moderately thin paste is obtained. Place a portion of the paste on the back of the quartz dise and press a small piece of glass down over the paste to prevent its drying out during the test. The surface viewed through the quartz disc should be uniform and free from air bubbles. Place the plate carrying the disc in the sample holder at a distance such that the surface of the sample is 10 cm. from the center of the arc. Cover a portion of the sample with a strip of thin brass or other opaque material. 2. Starting and Operating the Arc.—Before starting the arc see that the upper electrode is fairly free from ferric oxide and is adjusted to extend 14” to 32” below the radiator and is centered directly above the lower electrode. Now close the main switch, bring the elec- trodes into contact with each other and quickly separate them—thus starting the arc. The shallow cup on top of the lower electrode should be completely filled with a bead of magnetic oxide. If this is not the case, raise the current to about 10 amperes until the top of the upper electrode is in a thoroughly molten condition. By quickly bringing the electrodes into contact and then separating them again, the drop is transferred to the lower electrode. The 10- amp. current is then maintained until the top of the upper electrode is again molten, so as to obtain a symmetrical bead on the upper electrode also. Now cut in resistance until the current is adjusted to exactly 5 amperes, using the large rheostat for coarse adjustments and the small rheostat for fine ad- justments; also adjust the distance between the elec- ar cee until the potential between them is exactly 40 volts. 3. Exposure of Sample and Interpretation of Re- sults——When the arc is operating smoothly at 5 *In a private communication Pfund and Eastlack state that a somewhat steadier arc may be obtained by using a current of 35 volts and 6 amperes. This gives about the same wattage and therefore the same intensity of light as a current of 40 volts and 5 amperes. LIGHT RESISTANCE OF LITHOPONE od amperes and 40 volts, open the shutter, exposing the sample to the arc, and close it again at the end of 30 seconds. Examine the sample carefully in a good light to see if the exposed portion has been darkened (as in- dicated by a line of demarkation between the exposed and unexposed portions). If not, another portion of the sample is exposed for 60 seconds, or, if the sample was appreciably affected in 30 seconds, the next trial is made at 15 seconds. For each exposure the position of the strip of brass protecting part of the sample must be changed. Repeat the exposure of the sample to the are (using fresh portions of the paste, if necessary) until the time required to produce the first appearance of dark- ening has been satisfactorily determined. The pre- cision which is regarded as satisfactory for exposures of different lengths is indicated below: Total time for 1st “Eyd-Point” should be darkening. located within— Ee LON eS eae geese eR eres eer 1 sec. SE Nara taeeetnieebbestgereete eee contre EE: Sh i TS I Ste pe Neen ee en Pee oer heres! Ie eigen se necnctb at itrvenagtencnereatceernatbecesoane Ee eee WC PLAT RTNS Shi ee Aa IR na Nee a neces a 20 oe NG T OUTING) os 0 2s Sse ae vee eeeunneen aime eee a The number of seconds required to produce first darkening is recorded as a measure of the light-resist- ance of the sample. Samples which show no darkening in 300 seconds (5 minutes) may be regarded as “light- stable,” although for all practical purposes samples which show no darkening in 60 seconds will not be appreciably affected by sunlight when used as a pig- ment in oil paints. Lithopone Samples Examined.—In the work carried out by the present writer, four series of samples were tested. They are designated as follows: Series A: Laboratory samples. A-l, A-2, and A-3 were originally obtained for specific-gravity work and were about four years old. The other samples of this series were from two to three years old. None were obtained for light-sensitiveness tests. Series B: Set of five samples of varying degrees of light-sensitiveness obtained from the Bureau of Stand- ards which had been sent to the Bureau by Dr. Booge. Series C: Standard samples of varying degrees of light-sensitiveness sent by Dr. Booge. 138 EXAMINATION OF PAINTS, VARNISHES AND COLORS Series D: Samples from factory batches obtained direct from the manufacturers. These represented current commercial lots. Tests on Water Pastes of Lithopones.—As pointed out in Kastlack and Booge’s communication, lithopone is far more sen- sitive in water paste than in any other vehicle. When exposed to the sun’s rays some samples darken perceptibly in a few minutes, while all except one of those examined were more or less discolored at the end of one hour under prevailing atmos- pheric conditions. Darkening under the influence of the iron are is sometimes a question of seconds only, while very few samples will stand exposure for ten minutes without discolora- tion. | Results obtained with the iron are on water pastes of the twenty-five samples examined are given in Table XVIII. In Table XIX are given the results of tests on series C and se- ries D upon exposure to the iron are and to sunlight. The sam- ples are arranged according to increasing light resistance. The table indicates that for water pastes the order of darkening, in general, is the same by the two tests. TABIE XVIII Iron Arce Tests—Water Pastes Sample Time for No. darkening. |. a) NMC 6 seconds |.) La aA Pe 20 seconds AH Bo aioe icsssvsvstschncntsnstnsegivnasstencentloactndtsbsncansicas ugar ppicekoociees de se et rrr 5 seconds |: a ne An TNE EM CMa Se 60-70 seconds DoD oaaccincee i sisbasosiveencnsincearncitin spuawuchdeeqpanesdbaecpebeetuladlesee sc baa nee ae ene 4 seconds |. | nn COMA RMN ennORGt we 650-700 seconds BAT dicncicesccseiesscsscenocasnonustesiossicscosbusei yes syedenedeclencousscsopet sual sult aaa 6 seconds BB es cessicconinsscsconeee i lade cele Disa Battal te ee ena alae ee 250-300 seconds Lt i) eee emcee: tee Ur MR a unaffected in 1,200 seconds BZ ae, eee fosesigsithnonelaael siponenactic ais oacen ete seed ats baile an 150 seconds |S an canis Mean ht ll 30 seconds Bak sci seeecscsssdlen alent cifbeoothlanng Deca ele otc er rr 16 seconds Ba B ccssssncscevssnsonidnss liad san cncopstopsunsaghia bie Seeaspctapuabieic ates isc get i er 4 seconds Ons Seen tmenn reac Meaneirar Incr A Taye unaffected in 1,200 seconds 95, A ie aE RE US eM SE 135 seconds 0: NINE CHM EAM ee 40 seconds CMA cose cdscctcecosesesectscinonls Heats emabls sda cn does hacen cele cll 18 seconds On | eer EI Se iON ee 4 seconds Do cosets ncasscen.epeecaesonmssive nnessubedueniniossassdlprassistsd Dabo buaestsstactes Riese = err 95 seconds | by EE a Pee ere R ce RE 240 seconds DB a Ea A aE Se 85 seconds | 5 RM SrA IM ta R AP eee AEN 1,200 seconds hn ee Onn EINE CROTOMEIOeCME 950 seconds o> een CECE COMM eM COTM ere 30 seconds | Ey Ape A MIRE EEN Traian TUR EP OMT eS 600 seconds LIGHT RESISTANCE OF LITHOPONE 139 TABLE XI1X—Order of Darkening—Water Pastes of Lithopone Slides for Sunlight Tests Prepared According to the Method of Eastlack and Booge Sunlight tests. Iron arc tests ge a a oan Re eee, Color after one hour Sample. exposure to sunlight. Time for darkening. eS ie: Ue e 0 egeee aera Almost black 4 seconds OE 8 Goat A ee aa Very dark gray 18 seconds 1 Tvtey col Saeki: nica er lee en Dark gray 30. seconds Ro Dae ae Dark gray 40 seconds {Ue Oe eee Yellowish gray 85 seconds 10 eee Gray 95 seconds SRE Soa. le ee sta Yellowish gray 135 seconds Poe i ae eee Gray 240 seconds sis Beet Gray 600 seconds {Ps Ue Pee ee eee Slightly gray 950 seconds ye ee ee os Very slightly yellow 1.200 seconds CS a ea ae Very slightly yellow Unaffected in 1,200 seconds The day on which the sun exposures were made was very hot and the sky somewhat hazy but not cloudy at any time dur- ing the exposure. | The discoloration of samples D-7, D-4, and C-1 in the sun tests faded completely in a few hours. The rest remained per- manently darkened although D-2, D-6, and C-3 faded out to a considerable extent. Tests on Glycerine Pastes of Lithopones.—Lithopone will also darken when glycerine is used in place of water in making the paste. The time required for darkening 1s somewhat greater than for water pastes. Table XX gives the resuits obtained on the samples of Series C. TABLE XX—Iron Arc Tests on Glycerine Pastes Sg A ae rr Unaffected in 1,800 seconds gn egies Darkened in 720 seconds ie i ene ne Darkened in 120 seconds (Od VSS a SENN nO ee Darkened in 45 seconds Te ee EI ae crs ee eee oe a Darkened in 12 seconds Tests on Varnish Vehicle Pastes of Lithopones.—Some manu- facturers and users of lithopone rightly prefer to make the test in oil or varnish vehicles in order to more nearly approximate actual service conditions. Tests were made by us to determine whether the results ob- tained in water pastes would run parallel with the results of 140 EXAMINATION OF PAINTS, VARNISHES AND COLORS sun tests on pastes in oil or varnish vehicles. For this purpose Dammar Varnish and also a commercial flat wall paint liquid were used. The tests were made on eight representative samples which darkened when exposed to the iron are, in varying periods of time. The results of these tests are given in Table XXI. It will be observed that the order of light stability shown in this table agrees well with that of Table XIX. Since there is no sharp point or narrow limit of time in which darkening can be said to occur in the sun tests, and moreover, the color of the discoloration varies considerably with different samples, slight discrepancies are to be expected. Iifforts were made to check the sun tests on Dammar varnish and' flat wall paint liquid pastes with iron are tests. The time required for darkening in these liquids is, however, so great as to make the iron are rather impractical for these pastes. The results obtained are given in Table XXIII. TABLE XXI—Sun Tests on Dammar Varnish Pastes | ee a Sample. 2 Hours. 5 Hours. 12 Hours. 20 Hours. Data. D-1 Unaffected | Unaffected | Very slightly; Bluish gray C-5 darkened darkest bluish gray D-2 Unaffected | Unaffected | Unaffected Apparently || C-4 unaffected D-3 Unaffected | Unaffected | Very faintly | Gray D-6 darkened D-6 Unaffected | Slightly Somewhat Quite gray C-3 affected darkened C-2 Unaffected | Unaffected | Faintly Slightly D-1 darkened bluish gray _Binish gray | C-3 Very slight | Slightly Somewhat | Quite gray D-3 indication darkened darkened C-4 Very slightly; Somewhat | Dark gray Vee dark C-2 darkened darkened gray G-5 Slightly Very dark Bluish black} Bluish black|} D-2 | eet darkened gray lightest LIGHT RESISTANCE OF LITHOPONE 141 TABLE XXII—Sun Tests on Flat Wall Paint Liquid Pastes Final Order Sample. 2 Hours. 5 Hours. 12 Hours. 20 Hours. of darkening. D-1 Unaffected | Unaffected | Very faintly | Somewhat C-5 darkened darkened | darkest yellowish | gray D-2 Unaffected | Unaffected | Unaffected | Apparently C-4 unaffected D-3 Unaffected | Unaffected | Slightly Slightly D-6 . yellow D-6 Unaffected | Unaffected | Faintly Quite yellow; D-1 darkened C—2 Unaffected | Unaffected | Faintly Slightly C-2 darkened yellow C-3 Unaffected | Unaffected | Apparently | Very light D-3 unaffected | gray C-4 Unaffected |Unaffected |Very slightly | Yellow C-2 darkened | C-5 Very slightly; Very dark | Very dark | Almost black) D-2 darkened brown brown lightest TaBLE XXIII—Ivron Arc Tests on Paint Liquid Pastes Time required for darkening Time required for darkening in Sample. in Dammar varnish paste. flat wall paint liquid paste. Gio P eee oe Unaffected in 3,600 seconds Unaffected in 3,600 seconds Ce oa etl Darkened in 500 seconds Darkened in 1,400 seconds 11 oS a See Unaffected in 3,600 seconds Unaffected in 3,600 seconds 1B Seon eee ee Darkened in 3,600 seconds Unaffected in 3,600 seconds Comparison of results obtained in different laboratories.— Light stability tests were made on the samples of series B and series C in water paste. Similar tests were also made by East- lack and Booge, and at the Bureau of Standards. Results ob- tained in the three laboratories are given in Table XXIV for the sake of comparison. The apparatus used by the writer and by Eastlack and Booge are described above. The following description of the apparatus used at the Bureau of Standards was submitted by Dr. J. G. Thompson, who made the tests, the results of which are given in Table XXIV. EXAMINATION OF PAINTS, VARNISHES AND COLORS 142 Spuodes ¢E UI SUdyIeC Spuodes © UI SUdyIVG SpUuodes (QT Ul SUDyIVG spuodves QZ UT SUdyIBC Spuodes GF UI SUByIVC, Spuodes (9 UI SUDYIVC SpuodeS QNE UI UsyIVp JOU Se0q Spuodes OYOE UI UsyIVp yOu S90q ‘as00G WD Youpysey SpUOd9S (KT UI SUDyIBG SpUuodeS GT UI sudyIVCd spuodes 90%‘, Ul UeyIep you se0q Spuodes F UI SUDyIVC Spuodes F UI SUdyIVG spuodes G—F Ul SUdyIEC Spuodes F Ui SUdyIeG Spuodes ET UI SUZyIRG SpU0deS QT UI SUdyIBG Spuodes (OF UI SUDHIR spuooes QZ UI SUdyIVd Spuodes GE-NE UI SUSyIBC - Spuodes OE UI sUdyIVG Spuoodes GET Ul SUDyIVCG spuooes QZ UI SUdyIeG Spuodes (G-O8 UI SuUDyIVC Spuodes YOYT—-06 Ul SUSyIVG Spuodes (GT Ul SUdyIeCG Spuooes 90Z‘T UI UsyIBp Jou Sood Spuodses 00Z‘T UI UayIep you se0q spuodes 00Z‘T UI UsyIvp you se0q ‘YoIvasoyY YSUIVA 3 YUIVG JO 94Nz4SUT ‘sprepuryg jo nveing o) a@) od T-D Ca ‘ON odureg SA1L0JDLOQD'T 9aLY ], 1D ajsvgq ayn 4, Ur auodoyjvT fo szsaz fo uoswmdwoj—AIXX ATEVL LIGHT RESISTANCE OF LITHOPONE 143 The source of ultra-violet light was a small iron are operating at 5 amperes and 40 volts. The electrodes were ordinary soft-iron rods. The dry samples were rubbed up to moderately thick pastes with water, using a rubber spatula. The paste was spread on one side of a plate of crystalline quartz approximately 1 inch x 214 inches x 1/4, inch thick. The quartz plate was mounted in a holder so that the ultra-violet light must pass through the quartz to reach the paste, the quartz-paste surface being 10 cm. distant from the center of the arc. The remote surface of the paste was coverd with a glass microscope slide to prevent too rapid evaporation of the water. The results reported are average values based on more than one determination. The cause for the discrepancies is not yet apparent, but is probably due partly to errors of observation in judging the time required for first darkening. Some operators can detect fainter shades of darkening than others. EHastlack and Booge have found that the composition of different types of iron rods form- ing the elctrodes has only a slight influence on the results. Probably the greatest source of error arises from the fact that different pieces of quartz used vary in their transparency to ultra-violet light. : According to Luckiesh* crystalline and fused quartz differ considerably, the crystalline variety usually being transparent further into the ultra-violet region than the fused. Different crystals also vary considerably in transparency. The writers used a disc of fused quartz one inch in diameter and one-eighth inch thick. In order to determine whether the particular piece of quartz used would affect the results to an appreciable extent, the writers borrowed the piece which had been used at the Bureau, using it in connection with their arc. The results checked those of Thompson’s quite closely as shown in Table XXV. The lower values obtained by Eastlack and Booge are no doubt due to their use of an optically clear quartz disc of only 1.5 mm. thickness. * Jltra-violet Radiation, page 73 (1922). 144 EXAMINATION OF PAINTS, VARNISHES AND COLORS TABLE XX V—Results Obtained at Two Laboratories Using the Same Quartz Glass Institute of Paint and Var- Sample. Bureau of Standards. nish Reteeees No. 2 Darkens in 80-90 seconds Darkens in 85 seconds No. 3 Darkens in 30-85" Saree | Darkens in 30 seconds No. 4 Darkens in 16 seconds Darkens in 14 seconds No. 5 Darkens in 4 seconds Darkens in 4 seconds The following comments were made by one observer to whom this paper was submitted: 7 Apparently temperature plays an important part in the color changes that take place when lithopone is ex- posed to sunlight or to ultra-violet light from labora- tory lamps. It is considered that with rise of tempera- ture to a certain extent, lithopone becomes less sensi- tive to change. Undoubtedly the condition of the at- mosphere in which the tests are made has something to do with the effects. It has been found, for instance, that darkening is much more rapid in a hydrogen at- mosphere than in ordinary air. Tests, however, in- dicate that darkening will not take place in an atmos- phere of ozone, and in most cases will not take place in oxygen. One investigator some time ago rubbed up a sample of lithopone in water on a glass slide, and placed it in a Uviol tube having a 2-hole rubber stopper, through which moist hydrogen was bubbled. The slide was exposed to the light of a Macbeth printing lamp, specially cored carbon rods being used. It was found, for instance, that even zine oxide would darken under these conditions, as well as certain copper salts, and the result was attributed to a reducing action. It has been known for a long time that lithopone may be made sunproof when ground in water paste, by the addition of small amounts of salts, such, for in- stance, aS ammonium, phosphate. However, when the same mixture is dried and mixed with oils and exposed, it is apt to darken very rapidly. In commenting upon the tests outlined in this paper, another well-known investigator gave the following information: LIGHT RESISTANCE OF LITHOPONE 145 Sunlight Test—We keep the samples moist by put- ting the glass slides on a piece of common blotting paper, kept moist by a small glass jar filled with water, and a cotton wick leads from the glass jar and is laid upon top of the blotter. In this way we have found we could keep samples moist for two or three hours, which is sufficient to get a good sun test. We have found that glass once used will absorb energy from the sunlight, and if this same glass is used for a second test the lithopone, if it is very sensi- tive to light, will turn without being exposed to the sun- light. We therefore make it a point to use new glasses for sun tests all the time. Using a glass which has al- ready been exposed might make a lithophone turn in 15 minutes as bad as it otherwise would in 30 minutes, and thereby give you a wrong test. Comparison with Paint-Out Tests.—We have found the humidity is the main factor in making lithopone paints turn in sunlight. We have made hundreds of ex- periments with flat wall paints and gloss paints, and find the flat paints to turn much quicker than gloss, and if the humidity is below 60 per cent the modern lithopones will not turn at all, while the old lithopones will turn as black as coal. These tests are made on pine boards painted with regular flat or gloss paint, one-half covered with paper, the other half exposed to the sunlight on the south side of our laboratory. Conclusion.—We agree with you, the sunlight test and the ultra-violet light test give concordant results, and we also agree with you that the ultra-violet test will make a quicker test than the sun test. We have found, as you did, water to be the best liquid for sun test exposure. Whenever a long exposure test 1S wanted, the quartz test apparently is the best, as it can be used continuously for three or four hours. We have noticed, as you have, that the action decreases as the tube gets old, and we therefore always carry an extra quartz tube in our laboratory for emergency, and check tests. As soon as we find the tube in use going off, we send it back and have it pumped out, and in that way we have had no difficulty in getting ac- curate and quick results. Conclusions.—The light resistance of lithopone may be tested by exposure either to sunlight or to an artificial source of ultra- violet light. Tests made on a number of samples indicate that the two methods yield concordant results. While the order of darkening of a series of pigments is the same by the two 146 EXAMINATION OF PAINTS, VARNISHES AND COLORS methods, a considerably longer time is required for the sun tests. For research work where there is trained personnel, the iron are could be a supplementary part of the laboratory equipment, since the intensity of the ultra-violet radiation can be main- tained most constant over a long period of time. For this rea- son, the iron are could be used to occasionally check up the in- tensity of the quartz tube mercury vapor lamp. In other words, it could be used as a standardization instrument. For ordinary paint factory use, it is suggested that lithopone be tested in the liquid in which it is to be used in practice. For this purpose, a quartz tube, mercury vapor lamp is most use- ful, because several samples of lithopone in different paint liquids can be exposed at the same time. In five minutes re- sults may be obtained and a photographic record made. ADDENDA EFFECT OF ULTRA-VIOLET LIGHT ON PIGMENTS OTHER THAN LITHOPONE The property of darkening when exposed to ultra-violet light is shown to some slight extent by other pigments than litho- pone; in fact, even by some inert pigments. While several pig- ments examined, notably antimony oxide, showed a change, the effect is usually only a slight graying which is not greatly ac- centuated by continued exposure to the light. While lithopone darkens most quickly in water paste, all other white pigments examined, if they changed at all, were most readily affected in glycerin paste. Results of tests on white pigments other than lithopone are given in Table XXVI. It was indicated by study of several samples that the presence of small quantities of water soluble salts or the effect of certain methods of heat treatment were accelerators of darkening. TABLE XXVI—Iron Arc Tests on White Pigments Other Than Lithopone The term “darkening” refers to a slight “graying.” Sample. Water paste. Glycerin paste. Zine: Oxide: ic ee aes Unaffected Darkened Basic Carbonate White Lead............... Unaffected Darkened Basic Sulphat White Lead No. 1..... Unaffected Unaffected Basic Sulphate White Lead No. 2...... Darkened Darkened TitanOR is ee ee ote Darkened Darkened Antimony) Oxide 220.0 Unaffected Darkened Bary tess n.cnduaeuhena a eae eee Unaffected Unaffected Siena ist oe a eee Unaffected Unaffected Zirconium Oxide (Hydrated).............. Unaffected Unaffected Ghine) Clay: :i.4.cb- ce seas Unaffected Darkened LIGHT RESISTANCE OF LITHOPONE 147 Results on some colored pigments are given in Table XXVII. It is interesting to note that pigments high in lead oxide are ap- parently more subject to ultra-violet light effects than some others. For instance, dry litharge, even when placed in a glass bottle, will show on the surface some color change when exposed to diffused daylight in a laboratory over a long period of time. TABLE XXVII—Iron Arc Tests on Colored Pigments Sample. Water pastes. QRPSV ET ETE ey EGS SYST: 9 od Ly Pa a eceneeaneenrereED Unaffected in 1,800 seconds Iron Oxide........... I Ee ee ener Unaffected in 1,800 seconds CP eC LOW (CED ASIG ) oes ntsstinthnecseccenteenne Darkened in 1,500 seconds jee FS ke SS et OG eee een Darkened in 45 seconds Light Chrome Yellow (Neutral)................. Unaffected in 1,800 seconds 2g al SEES WESSON Te SOeE ere ne ee ce Unaffected in 1,800 seconds (ey CECI TS eee etc De pe a eee rem Unaffected in 1,800 seconds PRES eT aff cee cot Sig te ee 22 ea nano nee aceon Unaffected in 1,800 seconds BriiantiOranees ake te ceeteettiee Darkened in 1,800 seconds Cirameny CllOw Cran ee oi eee Darkened in 1,800 seconds es Speen palo Oe maton) 8 yy Se, See se laren ene Faded somewhat in 1,800 seconds PEGE a re LENSE 1 oa ee ere Unaffected in 1,800 seconds Vie CURE ARS cs oe Sie Oe OR ea ce a errr Unaffected in 1,800 seconds OPACITY OF PIGMENTS TO ULTRAVIOLET LIGHT Considerable work has been done by P. R. Croll and J. D. Jenkins, on the relative transparent nature of films to ultraviolet rays. The writer submitted to them early in 1924 a sample of a special glass that had been ground to a pigment, with the request that determination be made of its opaqueness to ultraviolet rays. Their photographs were made through a thin layer of metallic silver which is transparent only in a narrow band of the ultra- violet, around 3100A’s. Subsequently they received a Corning filter quite opaque to visible rays but very transparent to the ul- traviolet down to about 3000A’s. In their subsequent work on the glass pigment forwarded to them, they used as a light source an iron arc with 5 amperes and 40 volts. Exposure was made in back of a screen, at a distance of about fifteen inches from the arc, the screen being interposed between the are and the paper. The pigments were illuminated by the light from the iron arc, the light passing through the screen. They were then photographed by means of a pin-hole camera from above. A sketch of the ap- paratus used, together with the results obtained with zinc oxide, the special powdered glass, silica, and white lead, are shown below. As was expected, the zinc oxide appeared black in ultraviolet light, because such light is absorbed by this pigment. The pig- ments that did not absorb the ultraviolet light appeared white. 148 EXAMINATION OF PAINTS, VARNISHES AND COLORS Cartehocmclemevtenonesevan.onen pontacnsenansoneah as Sad amas Cee we cee tooneres FIGURE 74 Diagram showing method of photographing pigments by re- flected ultraviolet light. (Croll.) FIGURE AD Photographs of pigments taken by reflected ultra- violet light (Croll \ CHAPTER XV. VISCOSITY OF VARNISHES GARDNER-HOLDT APPARATUS In making routine consistency determinations where great accuracy is not a prime consideration, the simplest and most rapid method is preferable. The widely used air-bubble test, if used with certain precautions, gives a comparative measure of consistency and is sufficiently accurate for most routine work. It is common practice, for instance, to compare a sample of varnish drawn from each individual batch with a _ standard sample of the same varnish which has previously been found in actual use to have the desired consistency. To make such a test, a small tube or vial is filled with the varnish! and an air space is left between: the surface and the cork. When the tube is in- verted, the air bubble rises through the liquid at a definite rate, depending upon its consistency. The size of the bubble and the diameter of the tube are factors which also affect the rate of vise. The speed with which the bubble rises through the liquid is compared with the rate of rise in a standard sample. This test as usually made, however, is only comparative and does not give a definite numerical value that may be preserved for future reference. The writer and P. C. Holdt have recently devised a simple type of apparatus that will probably be of service to the varnish superintendent and chemist. This apparatus, which is shown in the illustration below, consists of a case which holds twenty viscosity tubes filled with a series of mineral oils that will not show any change of viscosity with time. The tubes are placed in alphabetical order. The case also contains a card showing the approximate absolute viscosity of the liquid contained in each tube. Thus a varnish matching tube E would have a vis- cosity of 1.25 poises. It may be preferable, however, for the varnish maker always to refer to consistency E or consistency H, and so on. With the above type of apparatus available for comparison of varnishes, the use of such terms could be re- ferred to in correspondence and be specifically understood by the operating heads of varnish departments in plants located at widely separated points. | 149 FIGURE 76 Gardner-Holdt Viscometer. VISCOSITY OF VARNISHES 151 In this set of viscosity tubes, the difference between any two adjacent tubes is equal to about 1% bubble. It may be found convenient to reduce the number of tubes to 10, making a dif- ference of a whole bubble between adjacent tubes. Following are the approximate absolute viscosities of the 20-tube set: TABLE XXVIII—Approximate Absolute Viscosity in Poises at 25° C. eee Le ae CODE = tp 7 a aE ee 1.40 Ke Pease IP eaeenedee 4.00 Tee ee CD ote Cece th et 1.65 Lie eee 3.00 Le aoa ities 4.35 ele hee hon! ABLE) ot 32 Bytes 2.00 Nigsse. 3.20 Ae So eae 4.70 1a Me eee TULL ho) areas 2.20 IN staat 3.40 Rees 5.00 | eke dee oho Vga 4 ea eee Det Con sete 3.70 J RES Ta tree 5.50 A similar set of viscosity tubes could be made up by anyone without reference to absolute viscosity. By blending two min- eral oils, one of high and one of low viscosity, in various pro- portions, a set of standards covering the range of consistencies found in any manufacturer’s products is readily made. The different tubes could be lettered or numbered or designated in any other convenient way. Three factors were considered in making up the apparatus described above (1) Tubes, (2) Standard liquids, and (8) Con- ditions influencing the test. These factors are discussed be- low. . Tubes.—Various kinds of tubes are now in use for the air- bubble test. These tubes vary from the ordinary small homeo- pathic vial to specially made tubes, including carbon tubes with marks for fixing the size of the bubble. The proper length of such tubes is generally determined by the convenience of handling. It is important, however, ‘that the diameters of the tubes containing the liquids to be compared are practically equal. Every tube selected for a case is first carefully calibrated and tested in comparison with a standard set of tubes which have the desired dimensions. | Since the allowable variation in the diameter of tubes is very small (not more than 0.1 millimeter), they must be accurately measured if direct measurement is resorted to in selection. The writer has been unable to secure a gauge suit- able for measuring the inside diameter. It has been found, however, that if tubes having the same outside diameter as measured with a micrometer caliper were used for the bubble test with the same liquid they would be suitable for further examination and checking with liquids. In several gross of a baz EXAMINATION OF PAINTS, VARNISHES AND COLORS particular type of tube examined the outside diameter of a con- siderable number was found to be 13.35 mm. (+0.1 mm.). All were 110 mm. long. This size was tentatively selected as the standard size. These are made up at a glass factory from speci- ally selected tubing. Out of a gross, not over 20 are usually found that may be used as standards. Standard Liquids——Since all varnishes change more or less with time, liquids which do not change should be selected as standards. Glycerin-water mixtures and sugar solutions have often been suggested as standards. In both of these there may be in certain ranges of concentration very great differences in viscosity for slight differences in composition. This result necessitates an absolute viscosity measurement for each stand- ard liquid. There is, furthermore, in the case of sugar solutions the probability of considerable viscosity changes with time, due to changes in composition (inversion, fermentation, etc.). The requirements of a standard viscosity liquid are, therefore, non- change with time and availability over the desired range of viscosities. After experimentation, it has been found that satis- factory liquids may be made from lubricating oils of known types. Compounded lubricating oils, however, cannot be used, since they contain vegetable oils, and the free fatty acids con- tained in such oils would cause considerable change in the viscos- ity of the standards. On the other hand, pure mineral oils can be blended to secure any viscosity met with in varnishes, and can be kept indefinitely without change. Moreover, they have the further advantage that the viscosity of certain intermediate blends can be calculated with considerable accuracy. Hence it is only necessary to measure the viscosity of a few of the liquids in any series of blends. Conditions.—The air-bubble test is very susceptible to tem- perature. Merely holding a tube of varnish in the hand a few moments is sufficient to cause a very appreciable change in the viscosity of the varnish. Precautions must, therefore, be taken to insure a uniform temperature in the standards and the test sample during observation. Lubricating oils and varnishes may undergo very different changes in viscosity with equal changes in temperature; hence it is necessary to use approximately the same temperature in all tests, allowing a variation of not more than 2 or 3 degrees either way. The size of the bubble slightly VISCOSITY OF VARNISHES 153 affects the speed with which it rises, and it should be approxi- mately the same as that of; the air bubble in the standard tubes. Results—In a large number of samples of all types of com- mercial varnishes recently examined, viscosities ranging from 0.6 to 5.5 poises at 25° C. were found when working with the Bingham plastometer.* To cover the complete range of viscos- ities noted above, about fifty tubes would be necessary to include differences of 0.1 poise, which is the limit of difference the air bubble test will show. It was found, however, that twenty tubes are sufficient for all practical purposes, one tube being used to represent about each one-fourth poise. For routine factory work, ten tubes showing a difference of one bubble be- tween adjacent tubes, will probably be satisfactory. In the tubes referred to above, the viscosity of the straight oils and of five blends were determined experimentally, the absolute viscosities of the other blends being calculated. With these, however, the approximate absolute viscosity of any varnish can be very quickly noted and recorded as a definite numerical value. In Scientific Section Circular No. 127, in which a description of all types of viscometers in presented, are given the absolute viscosities of a number of varnishes as measured in the plasto- meter. The absolute viscosities of the standard viscosity liquids herein described were measured in the same instrument. If the approximate estimation of absolute viscosity by this test is justi- fiable, the above varnishes should check with the standard. tube which has been assigned the same viscosity. This has been found true. The above sets of bubble tubes as made and stand- ardized at the writer’s laboratory are now in wide use through- out the American varnish industry, being used in place of the cumbersome and time-consuming apparatus formerly applied for such work. * See Circular No. 127 of the Scientific Section. CHAPTER XVI. SURFACE TENSION AND INTERFACIAL TENSION OF VARNISHES AND PAINT LIQUIDS While viscosity probably exerts a predominant influence on the working and spreading characteristics of a varnish or paint liquid, the appearance of the film after application will also depend to a certain extent upon the surface tension relations existing between the liquid film and the solid underface. Phe- nomena such as the tendency of oils to draw together in drops, the ease of wetting and grinding of various pigments with different oils, etc., have been conceived of as surface tension effects. The pitting of varnishes and baking japans or paints may also be at least partly due to this cause. Surface tension as usually discussed refers to a tension or strain at the surface of a liquid in contact with air which causes the surface to act as though it were an elastic membrane. In a mass of liquid each molecule exerts an attractive force upon other molecules within a definite radius. As each molecule with- in the mass of the liquid is surrounded by other molecules, the attractive forces exerted upon it by surrounding molecules is equal in all directions. The molecules immediately upon the surface, however, are exposed to molecular attraction only from the interior of the mass of liquid and there is consequently a molecular pull toward the interior of the liquid. The inward molecular pull results in a tendency to contract, drawing the surface molecules inward. While the measurement of this contractile tension at the air- liquid surface is of great theoretical interest and has numerous important applications (as for example, the determination of molecular weights, structure of compounds, arrangement of molecules in the mass, etc.) it has so far been of little assistance in solving the problems confronting the paint and varnish chem- ist. It does not serve to distinguish between liquids of the same class or to explain phenomena frequently observed. Difference in the density of the phases on opposite sides of the surface are so large as to obscure small differences in the tension of different liquids. Conditions existing at liquid-solid or liquid-liquid sur- faces, are, however, of great importance in the present con- 154 SURFACE TENSION 155 ee OS nection. At such a surface where the density on each side is approximately the same, differences in the intensity of the ten- sion of different liquids against another immiscible liquid or a solid may be detected, since here the combined effects of both liquids are measured. The tension existing at other than air- liquid surfaces is usually distinguished as interfacial tension and will be so designated in this chapter. In varnishes (colloidal solutions) and paints (suspensions) where the surfaces between solid and liquid are extraordinarily great, the magnitude of the interfacial tension between the phases becomes a very important factor in determining the char- acteristics of the liquid. There are, therefore, several kinds of surfaces to consider and it is desirable to ascertain whether there is any relation existing between the tensions at these surfaces in different liquids, and the characteristics of the liquid film. From a prac- tical point of view, the most important of these various tensions is that at a liquid-solid surface. Very little is known concern- ing this tension, and it appears at present impossible to measure it. Relative values for the interfacial tension between im- miscible liquids can be easily obtained. The absolute methods of precision which are at present. available, however, apply to only one of the tensions—namely, that in the surface of the liquid against air, or its own vapor. AIR-LIQUID TENSION Three methods are commonly used for measuring the con- tractile tendency existing at the surface of a liquid in contact with air. Capillary tube method.—Surface tension is measured by the height to which the liquid will rise in a capillary tube of known diameter. The liquid rises until the tendency of the film to con- tract is balanced by the weight of the column of liquid. Drop weight method.—Surface tension 1s measured by the weight of a drop forming at an orifice of known diameter. The weight of the drop increases until it overcomes the surface ten- sion of the liquid. . Air bubble method.—Surface tension ig measured by the size of an air bubble forced through the liquid, the size being propor- tional to the surface tension of the liquid. These methods yield accurate results but require considerable 156 EXAMINATION OF PAINTS, VARNISHES AND COLORS time and manipulative skill. The apparatus illustrated and de- scribed herein is easily and quickly operated and yields results that check fairly close with the above methods. It was used for obtaining the figures given in Table XXINX. As indicated in Table X XIX, surface tensions of liquids of dif- ferent types, such as oils and volatile thinners, vary somewhat, but in different liquids of the same type the difference is too small to explain great differences in behavior. It also appears that liquids of different types may show the same surface tension when they would be expected to have widely varying values. The measurement of surface tension, is, therefore, of little as- FIGURE 77 This apparatus, designed by Dr. P. L. DuNouy of the Rockefeller Medical Institute, is manufactured by Central Scientific Company, Chicago, Nl. For a description of the instrument and details of operation see Bulletin No. 82, Central Scientific Company, and the Journal of General Physiology, May 20, 1910, Vol. 1, No. 5. SURFACE TENSION 157 sistance in studying the physical pecularities and variations in properties so frequently encountered in paints and oils. TaBLE XXIX—Measurement of Surface Tension Against Air by DuNouy Apparatus Orls— Dynes per cm. DT a i a hate atten hecerceneetnttenttnneenennencnae 88.5 heated to 250° C. for 10 mins... eee nent 88.5 heated to 250° C. for 20 miMS...... ee : 38.5 heated to 250° C. for 380 Mims... ee 38.5 heated to 250° C. for 60 MINS... 39.0 heated to 305° C. for 30 MIMS... ee te 39.0 Bh AT se sa anaes escent stncnncncnnreteceecnnntntnn a Say bs: ara cancectecee nr eneecanh sp cgemsteecenetene ne tneasdecertnetiatmnresertenente 39.0 Thinners— i 6 CSu aC BE a Nera 31.5 Orthodichlorbenzol SE SN ie ae ameter eer 40.5 Mineral Spirts— Panes aa ee cect eecnenmentedentenegrerenpeonencnenstntnnnenie 29.0 TN ey sch icles cc cepa een cot eee Ges ee teen, ete 29.0 Fe aa acl cent ee tbe nencecngePesentennctebennencenntorernnncncnenesons 29.5 Fe pest cenatenceesenqncnecereceeentttermeneceeeectuneernemnenneneemereagin 29.5 Br a ecg lnesttR cemececehagreeeeensnatentennecetenenerteesnnnctics 30.0 ee ae ccd cnet che con danndetenteevonsentennpenndcap metennennnnnnrcnensy 30.5 Fe accra nel at cen tecne ete tteeneeetbntnnncteentgeenanncetcs 31.0 Fa accesses epeemepcenersteceprntpesercenttcenepengeeesncnciet 31.5 Since no way of measuring the tension at a liquid-solid sur- face is known, it is desirable that means be found for determin- ing values which will explain differences observed in different liquids. Wells and Southcombe* have observed a definite relation be- tween the interfacial (oil-water) tension of lubricating oils and their power to wet metallic surfaces. They find that the lower this constant is, the greater will be the wetting power or “oiliness” of the oil. The ability of various oils to wet a given pigment is probably governed by the same relation. If the ten- sion is low the oil should spread easily and be readily made to cover every facet of the pigment particles. INTERFACIAL TENSION Relative values for the interfacial tension between liquids were obtained by the use of the apparatus shown ato in tig: 78. This apparatus as prepared by the writer consists of a 5 ec. pipette bent upward at the lower end and drawn to a point having an orifice of about .8 mm. It is supplied with a rubber * Soc, Chem. Ind., pp. 51-60 T. (1920). 158 EXAMINATION OF PAINTS, VARNISHES AND COLORS tube and clamp to facilitate filling and to regulate the influx of air during the determination. The volume between upper and lower marks equal about 4 cc. The figures given in Table XXX were obtained with this instrument. The pipette is filled to the mark and maintained at this level by closing the clamp. The lower end is immersed in a beaker containing water or some other immiscible liquid at the desired temperature. Enough air is admitted by loosening the clamp to cause a slow efflux of oil in a Series of distinct drops from the capillary tip. As the drops break loose and rise to the surface one at a time they are counted. From 5 to 10 minutes are required for a determina- tion. The instrument shown at A has been designed by the writers to secure greater convenience in operation and greater accuracy, and will be used in future work. The size of the capillary to be FIGURE 78 SURFACE TENSION 159 used will depend upon the viscosity of the liquids tested. It may be advisable to have two instruments fitted with different-sized capillaries to take care of extremes of viscosity.* If a capillary tube as shown at A is used it is essential that, in each determination, the top of the tube be perfectly clean and free from the liquid the interfacial tension of which is to be measured. If it is not kept clean the liquid in emerging will spread over the top of the tube, producing drops of non-uniform size and render the determination worthless. The number of drops formed by a definite volume of liquid is inversely proportional to the interfacial tension. In comparing two liquids specific gravity must be taken into consideration. The number is also influenced by both temperature and the depth of immersion of the capillary tip. Since observations are made at or near room temperature, it will be sufficient to maintain the water at the desired point, as the liquid in passing through the submerged part. of the tube to the capillary tip will come to the temperature of the water. If the beaker is always filled to the same height and the instrument rests on the bottom the de- gree of immersion will, of course, be the same. While the re- sults thus obtained are only relative, the values for different liquids of the same class vary greatly and the differences are such as might be expected from their properties. In Table XXX a difference in drying oils and thinning liquids not shown by the usual surface tension methods is indicated. For instance, perilla and chia oils are seen to have a much higher interfacial tension against water than has linseed oil. If the same relation holds at solid-liquid surfaces (which exists in applying the oil to a solid surface) it appears that this higher interfacial tension would account for the “crawling” of these oils. The low value found for extracted linseed indicates that the interfacial tension was reduced by the large percentage of free acid. Accordingly it was found that when different per- nentages of linseed oil acids were added to a linseed oil of low acid value, the interfacial tension was greatly decreased. The addition of linseed oil to perilla oil lowers the interfacial tension of the latter against water. In the mixture of oils given the crawling effect was found to be entirely overcome. While * The writers have turned their design over to the A. H. Thomas Com- pany, of Philadelphia. This firm has satisfactorily produced the apparatus in accordance with the design for $6.89. 160 EXAMINATION OF PAINTS, VARNISHES AND COLORS heating for a few minutes at a high temperature appears to lower the interfacial tension, if the heat is continued longer the tension again increases. The increase in viscosity, due to pro- longed heating, apparently overcomes the surface tension effects in the case of perilla oil. TABLE XXX—Measurement of the Tension at the Liquid-Liquid Surface . Against Water All measurments made at 20° C. Number Liquids of drops Bear w Lit See aasecccsccstecnase cnc hes daccyecvucseevessnSbveceneschenntecGlndebdeylsee sce age aaa 55 Linseed extracted (acid valve 22) oe. ceensceceeeeeseeessssseessemmmnntenceeeesmnmnsseeseeenenaaaunestes 82 95% Linseed U 70 5% Linseed acids § webedaceuccecccencccdccwewwnbevecvoaseesusens: acuntoscvetsrs=ssseecedsene= Sees ebeNesSs0necE Bn hones Sse lela Sanaa 90% Linseed U 90 10% Linseed acids § chacevenecevececconavnesaaqeccns##®@seunesudecnscuedssugmcontes ou asemereasesnr~nuaeets = —aUnen sae sme. Ges aes eame cme 80% Linseed l 295 20% Linseed acids (oe Pevil le coecccceccccsscsecececcccesveoncnstcbenusibincntessodteseeceessttetenteceestacendneet hen tncher Set ahenet ete eta oF CYL, cecceescssescsascossneeveceeseesvntcsetsteneegnesensnasgnterstesuneinnshnnteanertantaconeroetncr=ot sae eee oF Perilla (heated at 230° C. for 10 minutes ) ccc ee 42 Perilla heated 20 mins. at 2EO0° Coc ccrcccceccceecersssenesesnnneceennenecesmereeemnnnranantessaseats 33 Perilla (heated at 260° for 2 HOULs) .ecccccccccccsecssneretensmeesanssmnnmernmnaatesentie 30 Alkali refined Linseed Py RM AGid refined Limseed Oil ecccescccccccssoccsesssocsssssssmununseesececeesuseeteetsSuesuaneeseesasesunaunnnaneeteaamesatriaataata 44 Limsced fatty ACids..eacccceccmeesssecseesseesteessnceseemneesnresnttnsetussunttnneranemnnesersntennesessietaatsaeesee 300 66 2-3% Linseed | 52 33 1-3% Perilla § veeecenuecercserscccsuapecasacsuesnsccasenseses sucnsdeacceancancesnee#easscaneueussbasnansuce"ene=tavarenssapsasar=ssenns=aNsc===n8rss Varnish makers’ Linseed oil heated at 500° for 2 hours... 36 Perilla heated to 300° C. rerpric) ya. nnan- ana ecteecccceeecstenns ra eaeens aaa ere eee ~ 35 Cold pressed Liar 09 natn cee enn ets cc erp terrae nen tee 41 AA oil (causes pitting Of japars) occ ece estes sensceneeneennennencenneesnmmnannunntnaceae 33 Wray an cececziccscecccscedesececec,chcsseepcsthtesontcts>neasstlsenasasasbhlp eerancestres ted gedaan 40 PUY POM ta’ oneceecesneseccseeenetnevneeerstennentuenctntnsensennnenetnebaneuneeesnessnaentes eterna 115 Mimeral Spirits cceccccssssssecseneesesseseteseenseensornneennnsantttetnetteotanetnueateaiesanerunreseenneeneantcaeeaaaea ge Against Salt Solution Turpentine ci si-chcekiciete ean pear ee sachisceeseentomsesiablusee este ea 135 Mimerall Spirits ccc sccccccteeeccsncectecteeseetetrt cancer erfeseee nerd te 89 Turpentine and mineral spirts which show the same surface tension exhibit a very different interfacial tension against water. This result indicates that the selection of suitable thinners for various types of. paint and varnish liquids is a matter of great importance. “ All solid surfaces are believed to hold an adsorbed film of moisture. Although this film may only be of molecular thick- ness, it may yet form a continuous layer between the solid sur- face and the applied coat. If such is the case it is conceivable that the surface is really liquid-liquid instead of liquid-solid, and that the conditions obtaining in the measurement of the inter- SURFACE TENSION 161 De ee facial tension against water as described herein closely approxi- mate actual working conditions. If this tension is in any way related or proportional to the tension which actually exists at a solid-liquid surface it should hold for all immiscible liquids. If a definite relation holds for the liquid to be tested against any immiscible liquid it could more justifiably be used as indicating solid-liquid tensions. When determinations were made using salt solutions the ratio between the number of drops of tur- pentine to mineral spirits was approximately the same as when pure water was used. | | An explanation for the existence of equal surface tensions in liquids of the same kind is advanced by I. Langmuir, who refers. it to the arrangement of molecules in the surface layer. He states that: , The group molecules of organic liquids arrange them- selves in such a way that their active portions are drawn inward, leaving the least active portions to form the surface layer, the active portion of the molecule be- ing that part of the field characterized by a strong stray . field (residual valence). Surface energy is thus a meas- : ure of the stray field which extends out from the sur- face layer of atoms. The molecules in the surface layer arrange themselves so that this stray field is a minimum. The surface energy of a liquid is thus nota property of the group molecules, but depends only on the least ac- tive portions of the molecules and on the manner in which they are able to arrange themselves in the sur- face layer. In liquid hydrocarbons of the paraffin series, the molecules arrange themselves so that the methyl groups (CH:) at the ends of the hydrocarbon chains form the surface layer. The surface layer is thus the same, no matter how long the hydrocarbon chain may be. Asa matter of fact all these many different substances from hexane to molten paraffin have substantially the same surface energy, namely A6 to 48 ergs per square centimeter, although the mole- cular weights differ greatly. If now we consider the alcohols such as CH:OH, C.H:OH, etc., we find that their surface energies are practically identical with those of the hydrocarbons. The reason for this is that the surface layer in both cases consists of CH: groups. Accepting the above statement as true, the measurement of the surface tension of liquids against air would yield important 162 EXAMINATION OF PAINTS, VARNISHES AND COLORS information in regard to substances of different molecular groupings. It will not, however, serve to differentiate in any way between liquids which have the same atoms or groups in the surface layer. While it is possible that the so-called active portions of molecules may be drawn inward at any surface, whether air-liquid, liquid-liquid, or liquid-solid, it is probable as already pointed out, that the tension in the latter cases has a very different value from the former. Different vegetable oils may therefore show the same tension against air due to the fact that they all present the same group or portion of the mole- cule at the air surface, but it is conceivable that in contact with another liquid or a solid (pigment) different oils may have different groups in the surface layers, particularly if the ac- tive groups possess an affinity for the surfaces with which they are in contact. We have, therefore, different manifestations of the same force depending upon whether we are considering the tension between the liquid surface and air or the tension be- tween the liquid and another liquid or a solid. CHAPTER XVII. COLOR STANDARDS FOR VARNISHES GARDNER-HOLDT APPARATUS Some plant managers consider it of importance to gauge the color of certain varnishes so that batches made up will closely approximate those produced at previous periods. The usual means of accomplishing this is to keep samples for comparison. It has been found, however, that varnish samples kept in glass and exposed to light, may show a substantial change in color. Another method that has been used to some extent is to make up a solution of 3 grams of potassium bichromate in 100 cc. of pure sulfuric acid, limiting the darkness of varnishes to the depth of color shown by such a solution. This solution, how- ever, has the disadvantage of being quickly reduced, the yellow soon being replaced by a green tint. This change is sometimes noticeable on a few hours’ standing. The use of such a standard would, therefore, require the making up of fresh solutions from day to day. A suggestion has been made that a varnish slightly lighter in color than the standard solution of bichromate re- ferred to above, be prepared and preserved as the standard for comparison. This, however, is not always satisfactory, owing to the actual color changes which take place even in varnish and to the limitation of having only one standard rather than a number of graded colors. The writer and P. C. Holdt have found a number of other substances that fairly match varnishes in color but which unfor- tunately are not permanent. For instance, iodine solutions fade in the light, metallic salt solutions such as ferric chloride are affected by the alkalinity of glass containers, ultimately throw- ing down precipitates and becoming lighter in color. Organic dyestuffs experimented with have proved either deficient in red or yellow, or subject to rather rapid loss of color upon standing in the light. In the experimental work that has been conducted an attempt was made to use a set of cube rosin standards ranging from G. to WW. These were first melted and poured into perfectly dry, clear glass tubes such as are used for making the bubble viscosity test on varnishes. It was found, however, that upon 163 164 EXAMINATION OF PAINTS, VARNISHES AND COLORS cooling the rosin would crystallize in the tubes, sometimes de- posting long crystalline needles against the glass, causing an opacity which would obscure the color. Moreover the grada- tions of color shown by the rosin standards were entirely un- satisfactory. As a result of a series of extended experiments, it was found that the substance known as caramel (burnt sugar), when diluted with water, produced clear solutions which exactly match the yellow amber and red ruby colors produced by various types of varnishes. In fact, the color effects produced by different strengths of aqueous solutions of caramel more closely approxi- mate the colors of varnishes than any other substance experi- mented with. After considerable preliminary work, a series of TABLE XXXI ce. of caramel Solution No. | ce. of water. ney FE FS Te) bo ron TOR NORM NWN HO On obo ROOM HRA io i bo = ° on ot for) APN HH 12 caramel solutions varying in color from almost water white to that of the darkish varnish, was prepared from a strong solution made by dissolving 15 grams of liquid caramel syrup in 450 cc. of water.* This concentrated solution was diluted with various proportions of water to secure the desired range of colors met with, and ranging from standard turpentine to the darkest grades of oleo-resinous varnish. The concentra- tion of each solution is given in Table XX XI. In making the dilu- tions, both water and caramel solutions were accurately meas- ured from a burette. * Commercial caramel varies greatly in concentration. Several sam- ples were purchased by the writer from various drug stores. The strength, however, may easily be adjusted, using as a standard for one sample, 3 grams of potassium bichromate dissolved in 100 cc. pure sulfuric acid (spec. grav. 1.84). COLOR STANDARDS FOR VARNISHES 165 The solutions prepared as above were sterilizezd to prevent fermentation and consequent change in color. In determzning the best method of sterilization, one set of samples was sterilized by heating a weighed amount of solution to boiling for a few minutes in an Erlenmeyer flask fitted with an air condenser. After boiling, the flask was again weighed and a small amount of sterile water added to replace that driven off by the heat. In making up another set of samples, one-half of one per cent of sodium benzoate was added to each solution. This sample was not boiled. A. third set of solutions was made up but was not sterilized. These three sets of samples were examined at the end of three months. In the set that had not been sterilized, there were large masses of fuzzy agglomerates, indicating that considerable fermentation had taken place. In the set sterilized by heat, there were small amounts of fuzzy masses (possibly caused by some contamination in transferring the solutions to the sterilizezd tubes). The set of samples which had been ster- ilized with sodium benzoate showed absolutely no evidence of fermentation. It was decided, therefore, that this method of sterilization is the best. Later it was found advisable to use 25 per cent of alcohol in the solutions. To test the permanency of the suggested color standards, the color strength of each solution was determined by means of the Lovibond tintometer in terms of both red and yellow. These readings were then repeated at intervals of from two to three weeks to determine whether any change was taking place. The same set of tubes was used throughout, being tightly corked after each reading. They were kept in the laboratory upon a table in the light so as to afford every opportunity for color changes. The results on a series of four readings are given in Table XXXII. It will be noted that there was practically no change in the color of these standards between the first and the final readings. Any minor changes indicated were so slight as to be attributable to experimental error in observation rather than to change in the color of the solution. As a check on the results, there was made up on Oct. 12th another set of the standard solutions, by using the same lot of caramel diluted to the same concentration and sterilized by the same process. When these solutions were compared with those made up three months be- fore, upon which the readings had been made, no change was shown. 166 EXAMINATION OF PAINTS, VARNISHES AND COLORS From a strictly scientific point of view, it would be more accurate to measure color strength of varnishes in terms of wave length and to look for color changes with the aid of a colorimeter. However, a variation in color that cannot be de- termined by the unaided eye is of no importance in the pres- ent connection, as approximations only are desired. Moreover, because of the high cost of accurately standardized colori- meters, such apparatus would not be available in most varnish factories. It is the writer’s belief however, that a simple form of apparatus such as is suggested in this paper, might be pro- duced by anyone interested and quite satisfactorily serve the purpose for commercial work. TABLE XX XII—Color Strength of Caramel Solutions (Lovibond Tintometer) Ist Reading 2nd Reading 3rd Reading 4th Reading Sam- | Size July 7th. July 15th. July 28th. Aug. 22nd. ple Cell. | eee No. Yellow. | Red. | Yellow. | Red. | Yellow. | Red. | Yellow. Red. Ostet os yy" 2.0 0 2.0 0 230) OT 2a .0 eee yy" 5c ae a.0 > 3.0 ue 3.0 he Yat gee ly" boo) “2 5.0 2 5.0 Lg 5.0. se ete, yy” 8.5 2 8.5 3 8.5 3 8.5 72 a ee 1" 16.0 eT 16.0 oni 16.0 he 16.0 8 Y peer Meng Ss 26.0 9 26.0 Pot 26.0 1.35) 26.0 1.35 Pe ae yy” 36.0 2 36.0 26 36.0 3:0 36.0 3.0 DO eae 30.0 1:75) 30.0 1 7514308 7a Oe ees 0) 1475 HG eres yr 42.0 4.0 42.0 4.5 42.0 4.7 42.0 4.5 Liccie yy" 51.0 ica HzO 8.0 51.0 8.0 51.0 ee Lee yy" 61.0 12-5 61.0 5 ra 61.0 1256 61.0 12.5 Nore: Because of the very light color (match for turpentine) of Sample No. 1 this was not included in the readings. . In order to test the permanency of the color of varnishes, samples of exterior varnish, floor varnish, and rubbing varnish of well known commercial brands were selected. These were placed in tubes in the original undiluted condition, and also diluted with 25 per cent and with 50 per cent of pure spirits of turpentine. Five sets of tubes thus prepared were sealed air- tight in viscosity bubble varnish tubes. Two sets of these sealed samples were wrapped separately in heavy paper, placed in a box so as to completely exclude all light, and so prutected until the time of making a reading for color value. Two other sets were exposed to ordinary daylight in the laboratory but not to the direct rays of the sun. Readings were taken on one set of —R—— ie ee COLOR STANDARDS FOR VARNISHES 167 the sealed tubes kept in the dark and one set kept in the light, at the end of periods of one month. On the sets kept in the dark, no appreciable change was observed at the second reading. The sets kept in the light, however, showed considerable change. Readings on the latter are given in Table XX XIII. The change in some of these was sufficiently great to be easily detected by the eye without the use of an instrument. It is very interesting, however, to note that the change is not always a lightening of color. For instance, some samples had become very much darker in color. TABLE XXXIII—Readings on Varnishes Exposed to Light, Showing Changes in Color Values ; 1st Reading 2nd Reading 3rd Reading Aug. 22, 1921.| Sept. 13, 1921.] Oct. 11, 1921. Sample. (2) be PRS Tel ree pty Bae Se Seis a OC & Yellow. | Red. | Yellow. | Red. | Yellow. | Red. Exterior Varnish....... yy" 42 1.1 36 123 ‘33 Vege: Ext. Varnish 25% Turp..| 1” 32 0.8 30 0.5 28 OSD Ext. Varnish 50% Turp..| 1%” 28 0.5 23 OS ve 0.4 Floor Varnish.......... yy” 65 320 62 305 61 3.0 Floor Varn. +25% Turp.| 4%” 52 11 50 i loge) 45 1.1 Floor Varn.+50% Turp.| %” 36 0.1 34 0.1 ee 0.1 Rubbing Varnish....... yr 42 5.6 43 6.2 46 6.2 Rubbing Varn. 25%Turp| 14” ol 4.3 36 4.2 38 4.0 Rubbing Varn. 50%Turp| 14” 42 5.0 48 6.0 50 6.0 The same combination of glasses was used in successive readings to deter- mine whether there had been any change in color. This vrocedure is nec- essary because the combined thickness of the glasses affects the reading. For instance, a sample may match glasses 16 + 14 +8 but be lighter than than a combination of glasses 16+ 14+672. In the second and third readings, the same combinations of glasses as were found to match the sample in the first readings were tried. Changes were then made until the glasses matched the samples. In Tables XXXII and XXXIII only total readings are given. In considering the set of 12 solutions reported on in Table XXXI, it was found possible to omit samples 3 and 5. This lefta series of 10 standards. Standard No. 1 is the equivalent to “Standard” for turpentine, in accordance with the Interdepart- mental specifications of the U. 8. Government for this material. Standard No. 9 in this new set is the equivalent of the bichomate solution used as a standard for gauging varnishes in accordance with the Interdepartmental specifications for spar varnish. These 10 new standards, made up as outlined above and now 168 EXAMINATION OF PAINTS, VARNISHES AND COLORS containing 25 per cent alcohol to further guard against fermen- tation are sealed in glass tubes with corks and viscose tops. These are placed in a special carrying case similar to that used for the bubble viscosity test standards. The upper part of the case bears a label giving the color strength in red and yellow of each sample in accordance with Table XXXIV _ shown below. These tubes as made and standardized at the writer’s laboratory are widely used throughout the industry. TABLE XXXIV Stats Ce. of Ce. of Size Combination of Glasses in ON, <— W : i Caramel of ; Lovibond Tintometer to on ater | Solution! | Cell match sample 1 99.8 0.2 VY" Yellow Red 2 99.6 0.4 VAG 2.0 0.0 5 97.6 2.4 1" 5.0 0.2 4 92.6 7.4 4" | 16.0 0.8 5 88.9 1h 4" -* 16+10=26 Pele sh 6 81.5 18.5 1" 16-+-14:-6 = bee Wiese se. Sees te 7 72.2 27.8 1" 16-+14—30 S78, 8 55.6 44.4 yr 164+14412=42 | 4.5 9 40.8 59.2 yr 164+14412+49=51 7.5 10 22.2 | 77.8 yw" | 164144124104+9=61 [°12.5 | ee ren) 1 Solution made of 15 grams commercial caramel syrup in 450 ce. water. No. 1 equivalent to limit of color for turpentine, U. S. interdepartmental Comm. on Paint Specifications, Recommended Standards for Turpentine. — No. 9 equivalent to limit of color for Spar Varnish, U. S. Interdepart- mental Comm. on Paint Specifications, Recommended Standards for Spar ae 3 grams potassium bichromate to 100 cc. Sulphuric Acid (Sp. 108 x e 2 tt ; : . } CHAPTER XVIII. TESTING THE SPEED OF EVAPORATION OF THINNERS FROM PAINT AND VARNISH FILMS WITH A DISCUSSION OF THE VISCOSITY EFFECTS INDUCED BY VARIOUS HYDROCARBONS Oleo-resinous varnishes usually contain from 40 to 60% of “thinners” such as turpentine, mineral spirits or similar organic volatile liquids having quite wide variations in boiling points. The rate of drying of such varnishes has been considered as de- pendent to some extent upon the character and amount of thin- ners present. That mineral spirits will evaporate more slowly than turpen- tine from a varnish film is well known. The effect of the type of hydrocarbon upon the rate of evaporation has heretofore ap- parently lacked investigation. The proportion of the various fractions of widely different boiling points which make up the hydrocarbon thinning liquids is also a matter of considerable importance. In addition to the influence of the above factors upon the drying of a varnish may be mentioned the effect of the thinner upon the viscosity of the thinned varnish. The ex- periments described herein were conducted for the purpose of securing information along the above lines. In order to secure exact data on the subject a series of thinners of widely varying boiling points—namely, turpentine, mineral spirits, solvent naphtha, benzine and benzol—were ex- perimented with. The varnish bases were prepared in a varnish plant in 100-gallon kettles. One was a short oil interior rubbing varnish containing about 7 gallons of varnish makers’ linseed oil to 100 pounds Kauri gum; the other a long oil spar varnish containing about 24 gallons of Tung oil and 12 gallons of alkali-refined linseed oil to 100 pounds of combined varnish resins. These varnish bases were sent to the laboratory without added thinner. The varnish solutions were prepared by warming the base until it became liquid enough to incorporate the thinner, care being taken to avoid excessive heating. Both base and thinner were very carefully weighed* before mixing. All samples were * Results throughout are based on percentage of volatile by weight. 169 170 EXAMINATION OF PAINTS, VARNISHES AND COLORS rewelghed after mixing to insure that there had been no appre- ciable loss of volatile during the mixing. In no case, except with certain of the lower individual fractions, was the loss suf- ficient to require further addition of thinner to secure the de- sired percentage of ingredients. The amount of thinner did not vary in any case by more than a fraction of 1% from that shown in the tables. In Table XX XV is presented a distillation chart of the various thinners used. The mineral spirits were of a high grade com- mercial type meeting the specifications of the U. S. Interdepart- FIGURE 79 Weighing Bottle Used in Tests mental Committee on Paint Specifications. Benzine, benzol, and solvent naphtha were average commercial samples of good qual- ity. The turpentine was a few months old and left a rather high viscous residue, but was satisfactory otherwise. Small bottles were tightly fitted with corks into which were fastened small brushes. (See Fig. 79.) A few grams of varnish were poured into one of the bottles, and the cork set tightly in place so as to prevent evaporation. The bottle, with its brush tal SPEED OF EVAPORATION *pIostA puv uMOIQ YIep oNnpIsey % OOT % OOT % OOT % OOT % OOT % 0° OOT G ol 61 3V G ol 61 FV tS oL0G 3V G ol GI FV g 0006 3V GaG o9 LG FV 86 ol 6L 4V 86 ol 61 IV 26 oL0G 3V 86 olGI 4V $6 0006 IV ¢° 16 o9 1G IV 8 T6I-921 8 L6T-921 L LOG—06T 8 TGI-1Ol g 00c-9LT Gee 9TS—GOG OL 9LI—-69T Ol 9LT—-OLT Ol 061-691 Ol TOT—-¥6 OL 9Z1-F9T Ol 60G-F61 Or 69I-S9T Or OLT-L9T Or 691-9ST OL ¥6 —06 Ol VOI-1L9T Or F6I-L81 OL S9OT—-E9T OL ZOT-S9T Ol 9SI—-FPFI OL 06 —88 Or T9I—O9T Or L81-Z81 Or €9T-e91 Or COlseoT OT PVI-VEL OL 88 —L8 OL O9T—O9T OL o8I-6LT OL c9I-19T OL S9I-—c9l OL FET-ZET Or 28 —98 OL O9T—6ST OL 6Z1-GLT OL T9T—691 Or c9T—O9T OL 6GI-6IT OT 98 —S8 Or 6ST-8ST Or GLI-TZT OL 6S1—-6ST OL O9T—-6¢1 Or cII-ZOl OL G8 —G8 OL 8SI-LST Or TZT-891 OL 6ST-9ST Or 6ST-8ST Or GOI—06 Or c8 -¥8 OL LST—9ST Or 89I—-S9T Or 9ST—-FST OL SSI-GGI OL 06 —-T9 OT ¥8 —08 OL OSi=cuT Or SOlL-EST P29 stp Oo PeTTHstp ‘Do PeTsip ‘Oo PeTssitp ‘Do P2Tstp ‘Oo Pon PIP Hai 938 jUI0IOg ‘duiay, || osezuI010g ‘duraj, || osequo010g ‘duiay, || esvquoo10g duiaj, || odeque010g ‘duleay, || ssejuoo1eg ‘dwio J, }! «Wy, Spads [BIBUIUL payeVUOlPRIT eyydeu-JuaA[og eulzueg (06) 1OzGeq oulyuedin J, Syd [BIOUTT\L YlOM 24) UL pas suauumy yz fo uoynusiq of abungy ainzosadwayz HbumoyS—AXXX ATAVL "* -onpiseyy ese 1890, UOTPOBAT sy[nsey jo ydeay SALNNIW NI SWIL Sol sl Sc! 4 a Ol 06 GZ 09 14 HSINUVA Yds SLIUIdS WWYSNIW « 10ZN3qg > INIZN3Q + INILN3dYNY © FIGURE 80 EXAMINATION OF PAINTS, VARNISHES AND COLORS 172 NOILVYOdVAQ SOVLNS0Y43d 173 SPEED OF EVAPORATION s}nsey jo ydeary SILANIW NI SWI sol OSI Gs 021 Coles ees $2 09 cy o¢ SI - Ol HSINYVA YOIMSLNI SLIUIGS TVYSNIN 2 10ZN3g > SNIZN3Q + JNILNadYNL® NOLLVYOd YAW AVLNAD Yad FIGURE 81 174 EXAMINATION OF PAINTS, VARNISHES AND COLORS and contents, was then weighed. The cork was then removed with its contained brush and the varnish thereon quickly applied to a weighed glass plate. The bottle was immediately corked and reweighed. The difference in the weight of bottle and con- tents before and after applying the film gave the weight of the film. Approximate Viscosity of Spar Varnish Thinned with Various Thinners in the Proportion of 50 Parts of Varnish Base to 50 Parts of Thinner Paraffin Petroleum Thinners Poises | >1-5 (V4 (ene CS 1.65 150-160° C. Fraction... 2.00 Fractionated Mineral Spirits “A”..02 3 2.35 Mineral Spirits cccccsccospc a kscectatncstcetsleunpeekele sae 8.20 175-181° C. Fyre cti orn icc cecil 3.20 200-215° Co. Fraction cio tees os 4.00 Equal Mixture of Fractions (175-181° C. and 225-235° C.)...... 6.00 225-235° Cx react miosis scescnsssaictove-oseetsseesonens enna eee 7.00 ZBOO-265° CC. Bret race ecc ss cdsssnossosonsonsgecoope cadezads cokes cepa 9.00 Cyclic Hydrocarbons Benzol 90°" 2 ee ee ee seoensposnseisthisisste pee ee 4.00 Solvent Naphthea. cosscicoccic3-teccccsc susie enced en 2) 800 TVAYPemtae on sacesseectcpctentaretbbvanitlsneeryseinestsnteaes oc 10.00 Similar work has just been conducted by the writer on volatile solvents used in making Pyroxylin Lacquer Coatings (see Fig. 102, page 290). CHAPTER XIX. EXAMINATION OF TURPENTINE AND MINERAL SPIRITS Methods for distillation range, polymerization values and simi- lar requirements for thinners are given in the specifications for turpentine and mineral spirits in the back of this volume. Further methods of examination are given in this chapter. Evaporative Value.—Physical and chemical methods for the examination of turpentine and mineral spirits are given in the specifications of the Interdepartmental Committee that are bound in the back of this volume. With mineral spirits, less uniform grading is found in commercial practice than with tur- pentine. For this reason manufacturers of paint and varnish often experience considerable difficulty in securing uniform and standard types of mineral spirits for their work. Therefore, in addition to the tests prescribed in the specifications referred to, it is well for the chemist to make a study of the evaporative value of various grades of mineral spirits submitted. For this purpose a good exterior and a good interior varnish base may be selected, heated, and thinned with about an equal quantity by weight of mineral spirits of the grades being tested. The varnishes may then be applied to weighed glass plates which should be re-weighed every fifteen minutes for a period of two hours. The loss in volatile is then reported. (See Circular No. 141 of the Scientific Section.) Mineral spirits having large quantities of heavy, non-volatile ends will readily be noticed. The body of the varnishes and the brushing, flowing and level- ing properties should also be ascertained by further tests. Solvent Properties.—It is also advisable to make a test to de- termine the solvent properties of the mineral spirits, and for this purpose it is customary to use varnish bases as referred to above, thinning down with equal parts by weight of the mineral spirits being tested. The reduced samples are generally placed in 4 oz. oil bottles and inspected for a period of 10 to 12 days to watch for the development of suspended matter, turbidity or other precipitated products due to lack of solvent properties of the thinner. Distillation of a sample of the mineral spirits and examination of the various fractions for solvent properties often gives much information of value. One of the most useful materials to include in a test for the 175 176 EXAMINATION OF PAINTS, VARNISHES AND COLORS solvent character of mineral spirits is extremely heavy-bodied linseed oil. Apparent solution takes place when such an oil is thinned with mineral spirits, but after standing, the oil is often thrown out, showing that the preliminary solution was only of a suspension colloid type. The continued addition of increments of mineral spirits to a volume of heavy-bodied oil, until the precipitation point is reached, will give relative data of almost quantitative character. Since such oils are often used in flat fin- ishes which sometimes contain in the liquid portion as high as 75 Begins to cloud Separation occurs | Thinner TT Oil Thinner Oil Thinner DS a a a 1 2 1 3 Oe oka oe eee 1 8 1 8 Boh CaP ee ae No cloudiness or separation at any dilution. reer eS eae 10, |e rm | OND a tee ee Mp manee Py essen A te, 7: No cloudiness or separation at any dilution. J 5 peeled (ha co wey Riccar 1 ck aa eae 1 3 | 1 4 Ke oth as ee ae 1 3 1 4 Vos ws 6G aie ak ee ee 1 8 1 10 per cent of mineral spirits, the throwing out of the oil would be a very objectionable feature. There appears to be a great difference in the action of the various brands of mineral spirits with bodied oils, especially blown oils. Turpentine usually mixes well in all proportions with such oils. When equal portions of the same oil and min- eral spirits are mixed, some samples show a turbid and milky appearance. As the quantity of thinner is increased the tur- bidity increases until separation occurs. While in some grades cloudiness occurs even at low dilution, other samples may not become turbid until much greater dilutions have been reached. — Some may remain clear when mixed in practically any propor- tion. Where there is only a slight turbidity at first, complete separation may occur on standing. The accompanying chart shows the dilutions at which cloudiness and oil separation first TURPENTINE AND MINERAL SPIRITS 177 occurred when thinning a very heavy grade of blown and heat- treated linseed oil with several commercial grades of mineral spirits. Figures indicate parts by weight. In making these dilution tests a tall narrow beaker may be conveniently used. A fair idea of the miscibility of the thinner may be obtained in the following manner: Weigh out a small quantity of bodied oil, say 5 or 10 grams, in the beaker. Then add an equal quantity of the mineral spirits to be tested. Stir with a glass rod, noting the readiness with which the two layers mix. Some samples will show a cloudiness at once, which may, however, disappear as the two mix. Others may mix per- fectly clear. Add successive portions of the thinner, stirring after each addition and noting carefully the appearance, readi- ness of mixing, etc. Determine the point at which a permanent milkiness results. After the addition of one or two more por- tions, part or all of the oil will usually separate on standing a short time. | While the quantity of thinner required to throw out the oil may in many cases be far in excess of the proportion ordinarily used, yet in consideration of the fact that the products which exhibit the greatest tendency to become turbid are most likely to separate on standing, it seems advisable to employ only those which stand up best under the dilution test. Run Kauri Test.—Another test of importance can be made with standardized run Kauri gum such as is used for testing the elasticity of varnish. The preparation of this is outlined in the specifications for spar varnish in the back of this book. The Run Kauri is dissolved in an equal quantity by weight of re- distilled turpentine. To 50 cc. of the mixture, mineral spirits is gradually added with occasional shaking until a cloud forms. An improvement in the test is to use a mixture of 100 cc. of the Run Kauri solution and 100 cc. of heavy bodied oil, subsequently thinning down a determined volume of this mixture with the mineral spirits under examination. For this purpose however a standard grade of heavy bodied oil should be used in every lab- oratory, otherwise different results would be obtained. Whether the thinner is derived from an asphaltum base or paraffin base petroleum is of little importance so long as it con- forms to other requirements. The asphaltum base petroleums are said to possess, in general, greater solvent power due to the presence of a larger proportion of cyclic hydrocarbons. If de- 1) J D Ten gram samples of heavy bodied linseed oil placed in each bottle. A different grade of mineral spirits added to each. When cloudiness was shown, addition of mineral spirits discontinued. Only small quantity required to cloud and throw out oil in test D. Considerable required to cloud test J. Test F shows no cloudiness and is miscible with oil at all dilutions. Flat paint liquid thinned _ with grade of thin- ner that has caused separa- tion of the bodied oil. FIGURE 82 Two samples of the same varnish thinned with different grades of mineral spirits. Note dark color of one caused by reaction between the sul- phur content of the mineral spirits and the dis- solved lead drier in the varnish. TURPENTINE AND MINERAL SPIRITS E79 sired, the proportion of the latter may be estimated compara- tively by the Formolit Reaction (Nastjukoff Test).* But prac- tical tests, such as those described herein must remain the de- ciding ones in determining the value of a given thinner. Sulphur Content.—Another very important observation to be made on mineral spirits is the effect of the sulphur content upon the color of paints or varnishes in which they are used. The white lead test that has in the past been used for this purpose will not very often disclose the presence of objectionable sulphur compounds. The Doctor test is not sensitive and is rather dif- ficult to perform. Varnishes, however, which contain metallic driers, such as lead, in organic solution, will rapidly become darkened when thinned with mineral spirits containing certain objectionable sulphur compounds. Some grades of mineral spirits, for instance, may contain as high as 114 per cent of sulphur. If this sulphur is in a certain fixed form, it may not darken with lead compounds in solution. Other grades of mineral spirits, which contain even very small traces of sulphur in readily available form, will quickly darken organic lead solu- tions. One test which the writer has used is as follows: Make up a varnish base by fusing 100 grams of rosin with five-tenths of a gram of lead oxide. If desired, co- balt, manganese, copper and other oxides that are liable to be present in a cooked varnish, may also be included in small amounts. This is then used as the base for test. 100 grams of the product is heated and thinned down with 100 grams of the mineral spirits to be tested, and held at a temperature of about 350° F. for 30 minutes, preferably in a reflux condenser. Darkening will occur with those grades of mineral spirits having reactionable sulphur content. Probably the most graphic test for sulphur in mineral spirits is the copper strip test. This is made by placing in a carbon tube about 15” long and 14” in width, a strip of copper 14” wide and 2” long. Sufficient mineral spirits is added to completely cover the copper. The tube is then immersed in an oil bath which is run up to 350° F. or to such temperature as will cause the mineral spirits to boil. The test should be run for a period * See Holde-Mueller, Examination of Hydrocarbon Oils and Saponifiable Fats, John Wiley & Sons, p. 38. 180 EXAMINATION OF PAINTS, VARNISHES AND COLORS of 30 minutes, and the effect on the copper strip observed. If only a slight bloom or fluorescence is shown, the mineral spirits should be acceptable. If blackening of the strip is shown, the mineral spirits should be looked upon as unsatisfactory for certain varnishes. This test will show a blackened condition of copper if the mineral spirits contains even .04 per cent of re- active sulphur. It has been proposed to run the copper strip test at a higher temperature, keeping the strip in a flask of boiling mineral spirits, connected with a reflux for ten minutes and then dis- tilling off about 96% of the mineral spirits. Such a test would appear rather severe. Distillation Range.—Better control of boiling range by the re- finer will enable him to deliver a more satisfactory product to the consumer. Mineral spirits conforming to Federal Specifications (see back part of this volume) while generally satisfactory for thinning paste paints, would be of much greater value for thin- ning varnishes if of a narrower range in distillation. The Philadelphia Paint Production Men’s Club suggest the following range: : Distillate below 150° C. not over 5%. . Distillate below 180° C. not less than 50%. Distillate below 220° C. not less than 97%. CHAPTER XX. TESTING ALUMINUM STEARATE ITS CHEMICAL AND PHYSICAL PROPERTIES AND USE IN THE PAINT AND VARNISH INDUSTRIES Aluminum stearate has been used in considerable quantities during recent years, in, the paint and varnish industries. It is used for producing certain physical conditions, such as body and non-settling in prepared paints; waterproofing and flatting prop- erties in interior wall paints, and to induce a rubbed-finish ap- pearance in some furniture varnishes. The extent to which these conditions are obtained in a product appear to depend upon or be related to the degree of viscosity which the stearate will im- part to the liquid, which, in turn, is influenced by the purity, texture, etc., of the stearate. Several manufacturers using aluminum stearate have experl- enced difficulties due to non-uniformity of different lots re- ceived.* In the present investigation it has been found that different brands vary greatly in both chemical composition and physical properties. In view of the variation of the different brands, it would seem desirable to have specifications, com- pliance with which would insure the suitability of the material. Visual Examination.—For the present investigation, a num- ber of samples were obtained from producers and users of aluminum stearate. It was found that much could be learned concerning their suitability by visual examination. For in- stance, those samples which are readily soluble and which 1m- part the higher viscosities to solutions are almost invariably the ones that are finely divided. When stirred up in a liquid, color- less paraffin oil, for instance, the more finely divided stearates yield milky liquids in which no coarse particles are visible. Other samples (coarse) contain lumps or agglomerates which do not break up on stirring and settle very quickly. When examined under the microscope some samples are seen to be of fine texture, and the particles, although apparently not crystalline, are clearly defined and fairly uniform in size. In other samples the material is seen to be more or less agglomerated and presents a *The investigation to date has been facilitated by the suggestions of Dr. P. S. Kennedy and Mr. H. M. Johnson, of the Murphy Varnish Co. 181 i ph 182 EXAMINATION OF PAINTS, VARNISHES AND COLORS very non-uniform appearance. In those samples examined, which were found to contain free stearic acid, the particles of the acid could readily be detected under the microscope by their semi-transparent appearance. Solubility—Aluminum stearate does not appear to dissolve appreciably in any solvent in the cold. It goes into solution in a number of solvents quite readily, however, when heated. When a mixture is heated, the stearate apparently softens and then melts as the temperature is raised, subsequently being dispersed through the liquid.. The character of the solution formed by the various stearates differs greatly. For instance, in certain concentrations in a given solvent, one stearate will yield only a thin liquid while another will yield a solid gel. With certain samples precipitation occurs upon standing, and the appear- ance of the solution changes, while in other cases no change is observable. Solutions of samples Nos. 1 to 7 in turpentine, mineral spirits, and benzol were made. In each case 10 grams of dry stearate and 200 c. c. of solvent were used. The stearate was dissolved by heating the mixture under a reflux condenser. In Table XXXVI observations made during the test are tabulated. It is realized that, in actual practice, stearates would probably not be used in this manner, but the test, nevertheless, throws some light on the possible behavior of different samples when used in the ordinary way. Remarks.—As stated above, a definite temperature is neces- sary for bringing a given sample of stearate into solution in any solvent. The boiling points of both turpentine and mineral spirits are considerably above the melting point of any sample of stearate. As a result the stearate melts and is dispersed through the liquid, forming a colloidal solution or gel. It is be- lieved that the nature of the colloidal body formed determines to a large extent the value of a given sample as an ingredient of paint and enamel. It should be noted, however, that the turpen- tine solution of some samples differs markedly from the mineral spirits solution of the samples. | Benzol, on the other hand, boils at a temperature considerably below the melting point of aluminum stearate. Since dispersion of the stearate does not occur to any considerable extent much below its melting point, only a small quantity of it is taken up 183 ALUMINUM STEARATE “MOT[OA oie G pue fF ‘g ‘Z ‘“SSeTLO[OO 91B ), pues 9 ‘I ‘pInbiT snosuesouoy ‘UuIyy ®B 0} Ajiseo pue Ajeqye[durod sATOSSIp ), pue g So]dwieg ‘anpiset sIy} JO o910UL sAlOS “u10930q -SIp 0} 1vedde jou seop oom 10 1noYy ; =) I uo uoljeredes yuetnovoy [eus ‘AypA APYSTs ‘ury ATOA “9 “ON papa lal a ae saa ‘Apnojo ATJYSS pue Moped ATJYSITS ‘uryy ATeA G pus fF “E “Z “SON 08 ‘yous & SuLAvey ‘Ayoye[duoout pur ‘uUOI}NjOS ony Ajjueredde ‘avalo pue sseptojoo ‘uryz ATOA *T “ON A [MOTs DATOSSIP G pue 7 ‘2 ‘ZT So] dures a ee SS ee SO “MOT[OA SS8T IO BLOUL 918 Szey}0 9Y} a[IyM ‘ssep1ojoo AT[eoryoeid ale 2 pue 9 ‘T ‘SON ‘[od Ys B pue °G 0} [ sofdures se AoueJSIsuOD oes VY} JNoqe Jo sieM ‘padjossip Aley,e;dutoo ysnoyye ‘2, pue g setdueg “padafossip 90}v1ve4s oy} Jo uorlz1od [[euis @ A[UO esnvdeq UIY} e1e G 0} T Se[duIes Jo SUOT}{NIOg : ALON “AY[IU yeyMoutos ‘uIyy ATOA *L ‘ON jozueq ‘WAY SOU YYMEUIOS SUTEq 9 pinbiy uty} Area @ ‘saseyd 4OUTISIP OA\4 ‘ON ‘qnoySnoiy} Adud}sTsUoD WIOJTUN Jo sjes jos ee L, puke 9 “SON | jo ystsuoo g pue F ‘gE ‘Z ‘SON ‘TOs YUS f ‘pinbi uly} pue jes A$iaA @ SI T ‘ON ‘AOUAYSTSUOD UITOFTIUN tee way ‘sosvyd OM} JO SUIYSTSUOD ‘TETTUIIS ATOA oe G pue 7 ‘E ‘Z “SON | AypeooeId Jo s[od snoosIA or J, pu g ‘qnoysnoryy ULosIuN ‘Jad oyTyM-AN[IU “PI[OS “TON | ‘son ‘poqou st souvavedde ul soue1e; -JIp 9[qeiepisuod SInOoYy MeF e SuUIpUeysS IajyyV ‘Sseynurut Moy ev surjiog uo ATeyeTd -ui0d pues ATIpvet sA[OSSIP sofdures [[V "9 “ON YPIM [BOTQUSPT “L “ON *TITABOY ‘Moped yno peyeredes yonut AIaA O18 G 0} T ‘UIYY AOA [eltoyeuL JueTNo00H ‘doy uo pInbi[ 1ve[o puw ssejtofoo “UIT, 9 ON | oze » pue g Jo suornjog ‘moras sso] VON UTA Teoruopul °S (ON | zo arow ore sieyjO {sseftojoo AT[eoT} a “MOTEq Uol}eIedes yusNo0p fpinbry ystmorjes ‘UIUL “Py “ON | _5y7d are J, pue 9 ‘T ‘Sutjooo uo doue suljuedin J, ‘doy uo pinby] uly} Fo JuNowe [TBUIS YITM ynq "Z ‘ON 0} TUTMWIS "€ “ON | _iyodde ul snosueSouloy ore suoryNios please IV ‘*seynuru maz ev BurfIoq uo Ayoyord -jek pue Apnojo ‘snoasta Area ‘Aoueystsuoo ultofiun ‘peTfes “Z “ON | _iyo9 pue Ajrpeet oajossip sojdures [Ty ‘ Sa a SUOI}NIOS SuUIyVUl 1018] YJUOW T SUOTZVATESGO Jo ouIr} ye suoTyeAresqO JUBATOS ES jozuag pun spudg jovaurpy ‘auyuaduny, us sazv.1n07G fo wo17zNjoS—TAXXX ATaVL 184 EXAMINATION OF PAINTS, VARNISHES AND COLORS by this liquid even after prolonged heating. In the solution made as indicated above, the liquid, when poured from the un- dissolved portion, was more nearly a true solution than is pos- sible to make in even dilute solutions in turpentine and mineral spirits. By the use of the higher homologues of benzol, how- ever, it is possible to make much more concentrated and more viscous solutions. VISCOSITY AND CONSISTENCY TESTS Jelly Test.—One manufacturer* of sterates uses as a control test a so-called jelly test. This test presumably indicates rela- tively the degree of viscosity that different samples will impart to a liquid. It is carried out as described below using the ap- paratus shown in Fig. 83: Heat 10 grams of aluminum stearate with 90 c¢. c. crude paraffin oil in a beaker of 200 c. c. capacity to a temperature of 150° C. Stir the mixture constantly while being heated. When solution is complete, cool to about 10° C. By this treatment a jelly is formed, which varies with different samples from a soft, oily mass to a hard, solid gel. The firmness of the gel thus made is tested by means of the apparatus shown in Fig. 88. The beaker con- taining the gel is placed under the plunger. On the small scale pan on top of the plunger another beaker is placed, and into this mercury or shot is poured until the gel yields under the pressure. The weight taken is the total weight of mercury, beaker, and plunger. As stated in a communication from the above concern, this is a rather crude test, being intended only for comparisons. It should be made on the various products under consideration at the same time and under the same conditions. - It is further | stated that when carried out as directed above, results will not check closer than 15 or 25 grams. An apparatus was assembled and this test was applied to the samples under investigation. It was carried out as described above, the gels being held at 10° C. for two hours to insure a uniform temperature. In check determinations the results differed considerably, sometimes varying as much as 20 per cent. The difference between different samples is so great, however, *Mallinckrodt Chemical Works. 185 ALUMINUM STEARATE oy 9,8 ( es aati sS FIGURE 83 Apparatus for determining strength of gel made of Aluminum Stearate. 186 EXAMINATION OF PAINTS, VARNISHES AND COLORS that even with this great variation the test may be of value. In making gels of different samples for a comparative test the same oil should be used for all samples as the firmness of the gel is slightly influenced by the viscosity of the oil. Considerable information is obtained by observing the be- havior of the material during the process of heating and the ap- pearance of the gel after cooling. In the opinion of the writer, these observations are more important than the firmness test. Solutions of stearates in turpentine and mineral spirits are FIGURE 84 Two Samples of Aluminum Stearate in Mineral Spirits After Standing One Month— Sample on right (No. Sample on left (No. 1) uniform consistency, mass is a solid gel. 4), shows a thin liquid phase and a fairly firm gel that has slumped down. ALUMINUM STEARATE 187 not suitable for consistency measurements because of their non- homogeneous nature. Solutions in paraffin oil may gel to a certain extent,-even at low concentrations. Benzol solutions of definite concentration are not readily made, as a portion of the sample usually remains undissolved. A further difficulty arises from the fact that the consistency of the above solutions may change materially with the slightest agitation, due to a breaking down of the gel structure. For instance, when attempts were made to measure the viscosity of paraffin solutions by the tube test, it was found that the inversion of the tube alone was suf- ficient to cause a considerable change in consistency. The ‘‘viscosity induction” of a given stearate may, however, be measured by the tube method, using a xylol solution. Xylol gives the same type of solution as benzol, and on account of the high boiling point of xylol, the stearate can be heated sufficiently high to obtain the desired concentration. This method, while not en- tirely satisfactory, yields good results if definite conditions are maintained. Below a certain concentration, aluminum stearate dissolves on boiling in xylol to a colloidal solution fairly free from suspended matter. The consistency does not appear to be greatly affected by agitation due to handling the container, and remains constant over a short period of time. It changes, how- ever, with age, usually becoming thinner. It is, therefore, neces- sary to make consistency determinations at a fixed time after preparing the solutions in.order to get concordant results. The exact procedure was as follows: bas . Three and a. half grams of stearate were weighed into — a 250 cc. Erlenmeyer flask and 100 cc. xylol added. The liquid was boiled for a few moments under a reflux con- denser. The solution was allowed to cool under the reflux and then removed and stood aside for two hours, taking care that none of the solvent was lost through - evaporation. The viscosity of this solution was de- termined in the usual way by the tube test, making the test at about 25° C. Johnson uses the following method for measuring the viscosity of paraffin oil-stearate solutions : | Dissolve 5 grams of stearate in 100 cc. paraffin oil by heating to 150° C. - Dip a marked spatula into the solu- tion to the mark, and allow to drain until definite drops come off. Allow a drop to fall on a glass plate inclined 188 EXAMINATION OF PAINTS, VARNISHES AND COLORS at an angle. The drop will flow down to a greater or less distance, depending upon the viscosity of the solu- tion. The distance of flow gives a relative measure of the viscosity of different solutions. CHEMICAL EXAMINATION Moisture.—Different lots of stearate vary in the amount of moisture which they contain. It may be determined in the usual manner—that is, by heat- ing about 1 gram of the sample in an oven for 3 hours at about 105° C. A method used by Johnson gives somewhat more con- cordant results, and is probably more accurate in the case of low melting point stearates. The latter method is carried out as follows: Carefully desiccate a quantity of oleic acid by drying in a moisture oven for several hours. Weigh into a small portion of the desiccated acid about one gram of the sample. Heat at 105° C. for 3 hours and determine the loss in weight. While the percentage of moisture is usually relatively small, it appears to influence the gelling properties of the sample, or to be related to it in some way. Several users -specify a low moisture content stearate, and at least one manufacturer at- tempts to keep the percentage in his product at 0.5 per cent or less. Upon the suggestion of E. J. Cole, several experiments were made to detremine the effect on the gelling property of water soluble compounds that may be present.. Small quantities of water, sodium sulphate solution, and sodium hydroxide solu- tion were added to separate 10 gram portions of No. 1 stearate. To each, 90 ¢. c. paraffin oil was added and the mixtures gelled as described in the jelly test. The samples to which pure water and sodium sulphate solution were added yielded gels apparently as firm as when nothing was added. The sample to which sodium hydroxide (a fraction of one per cent) was added, re- mained very thin throughout the entire heating, and when cold was very soft, similar to Nos. 6 and 7. The appearance was that of a highly refined Petrolatum Jelly (vaseline), for which it might serve in some arts. Apparently caustic alkalies have a very marked effect upon the jelling of Aluminum Stearate. In Table XX XVII are given the moisture content and water soluble in the samples examined. In general the samples of ALUMINUM STEARATE 189 en —————— FIGURE 85 Appearance of Three Gels Made of Alumi- num Stearates in Paraffin Oil—Upper sample (No. 12) is very white and crumbly. Middle sample (No. 1) fairly white and crumbly like polymerized Tung Oil. Sample (No. 6) at bot- tom is soft and smeary like vasseline. Note how it flows. 190 EXAMINATION OF PAINTS, VARNISHES AND COLORS lowest moisture content have the smallest proportion of water soluble. Table XX XVII, studied in connection with the experi- ments described in the previous paragraph, indicates that while the percentage of moisture may not in itself necessarily influence the viscosity of stearate solutions, yet it suggests the presence of compounds which do have this effect. Total Ash, Aluminum Oxide, and Water Soluble.—The de- termination of these constituents is an important part of the chemical examination. They are easily and quickly determined, and are valuable indications of quality. Of the samples under investigation, those which have the lowest viscosity induction values have a high percentage of water soluble, while in those yielding the most viscous solutions, the water soluble content is very low. These determinations were carried out as follows: About five grams of the sample was weighed into a silica crucible and carefully ignited over a Bunsen flame. The residue was reported as total ash. The crucible was then placed in a 400 ec. c. beaker and treated with boiling water to dissolve the water soluble portion. The solution was filtered through a quanti- tative paper and the paper burned in the same crucible. The second ashing represents Al: O: with the traces of iron and other impurities that may be present and the difference between the two weighings represents the water soluble. Iron.—The presence of iron is readily detected by the - yellowish red color which it imparts to the stearate solutions. The proportion is usually very low, less than .1 per cent. In such small amounts it would have no effect on quality, except in so far as color is concerned. Traces were found in both good and poor samples, hence it is believed that a quantitative determination is unnecessary except possibly when the material is to be used in a white or very light-colored product. Even in the latter case observations of the color of solution alone would probably be sufficient. | Conclusions.—The viscosity or “body” of solutions of alumi- num stearate in a given solvent varies enormously for different samples of stearate. Comparing the results of the firmness test with the viscosity of xylol solutions (Table XXXVII), it ap- pears that the viscosity also varies with the solvent used. For instance, Sample No. 8, which showed a rather high yield ar SBh ALUMINUM STEARATE LL EE) OL OTL ET OTEN ‘IVI “SS9TIOTOD % 9S L % 8° % 918 % LS 0 all ad ‘Tea[ “MOTTOA AOA | = =%98'8 %¥9' I YG OT B'S II Vue fee ABO L)ereee late) %6'S YS v %es Ot %8'T OL 9) ‘APNOP) YVYMOUIOG —“SS9TIOTOK) %90'9 %0'F¥ % 90° OT %6 1 6 V ueyy ssorT ‘IVat) “MOTPOA ATOA | %1B'6 % SBE" %9'6 %6'T 8 Wy EHD eee) ‘ApNopo ATS “SSoP1OTO) Yo LS %o8° Me 6 %E9'S L ‘Ivapo AT[BOIJORIg V uvy} ssoT “sousoserony ysingg Apyureq | Gh F Zoi’ S Gs 6 %e0 I 9 © PONS e0lS %o& 6 Yl % Yov Ul % 86° g = ‘19}} BUI papusedsns jo JuNOUIB 9 [[eUg “Lee]O ysoulTy “Moro Bfeq | %HVE'6S Lob obs U1 ZoL& 1 v Al ‘% ON SB ouIvg | = %6Z'6 %o9 1 %8 Ol % 89° ¢ L ‘Apnop Area “AXIAL %0'6 %ov" Yov 6 %vs" af ‘[Bl1lo}eul popuodsns Jo yuNOUIG ; f eae rae ae Be at) YS L % SE" %S8' L Yoo" J sprepueys IP[OH JO[AX Jo ‘SUIS &G %aT aTqnyjos onpIsad -laupier ‘“suOryNyOS OG Ul 94vIB9}S JO SUIBIS pure “O Vv I0}8 MA UOT}IUST dINYSTOT ‘ON JOJAX JO AYISOOSTA Z jo Uorynjos jo souvirveddy | adv L aypunayg wnuwuny fo sajdwng fo uoynuwpey fo 877nseay—TIAXXX 192 EXAMINATION OF PAINTS, VARNISHES AND COLORS point in the firmness test, produced a solution of very low vis- cosity when dissolved in xylol. The chemical examination has not proceeded far enough to draw any very definite conclusions. It appears, however, that the percentage of water soluble matter is important since those samples having the highest percentage, in general yield the least viscous solutions. The proportion of unneutralized stearic acid and of aluminum oleate probably modify to a certain extent the physical properties. | SUGGESTED TENTATIVE SPECIFICATIONS FOR ALUMINUM STEARATE The aluminum stearate must be finely divided and satisfactory for use in the paint and varnish industry. It must be white in color, and contain not over 0.1% iron as FeOs. | Moisture.—It shall contain not more than 1.5% of moisture. Water Soluble.—It shall contain not more than 2. 0% of water soluble material. Water Insoluble Ash.—The ash from the water oes ma- terial shall be not less than 6.0%. Appearance of Solution.—When 2 grams of aluminum stearate is dissolved in 50 grams of xylol, a practically colorless and fairly clear solution shall be obtained. CHAPTER XXII. SUGGESTIONS FOR MAKING EXPOSURE TESTS ON PAINTS AND VARNISHES (EXPOSURE TESTS ON PAINTS) (a) Select a soft wood such as white pine or poplar, unless it is desired to get special information as to the durability of paints on such woods as red cedar, yellow pine, or cypress. The FIGURE 86 Old panel exposure tests back of laboratory. latter woods are used where the penetrating properties of SVEN primers are being studied. (b) The panels used in previous tests made on a large scale were constructed to be 36” « 18” of three widths of siding, with a weather strip at the top. They were braced at the back. (See reports on the Atlantic City and Pittsburgh tests in early cir- culars of Scientific Section.) _ (c) When space for such panels is not available, boards 15” x 6” X 1” of dressed lumber are used. Allow the finished panels at least a week’s exposure to sun and weather previous to painting. Then air-dry in laboratory for a week, if they are to be painted inside. (d) Always make tests in duplicate. (e) If panels are to be painted inside on account of bad weather, allow each coat to dry indoors for 24 hours and then place out-of-doors for a period of at least three days’ drying be- 193 194 EXAMINATION OF PAINTS, VARNISHES AND COLORS tween coats. If possible, allow 10 days time between the coats for drying. The durability of any paint depends largely upon the period allowed for the drying of the successive coats. (f) If a white paint of a new formula is being tested, apply the paint in light tints as well as in white. Chalking of the white paint is not easily noticed. Chalking of light tints of the same paint will often be noticed by the flooding of the chalked FIGURE 87 _ Type of construction used in Atlantic City, Pittsburgh, North Da- kota and similar test fences. Modern tests should have panels at 45° to aie vertical to accelerate exposure. oitie pigment, which is often termed “fading.” Rich cream, pea green, and sky blue tints are suggested. (g) If possible, make exposures under two or more FAtmAtic conditions in various parts of the country. (h) Expose panels facing south. If panels are (ica at an angle of 45° to the vertical, the tests will be accelerated about 50%. (i) For metal paints, the selection of sand-blasted panels: i is preferred, since test panels free of loose mill scale are not easily obtainable. Cleaning of the surface of metal panels with benzol to remove grease is advisable previous to test. Metal panels 15” < 6” and of 18 to 22 gauge are of sufficient size for a test if made in duplicate or triplicate. Where space is available, panels 24” « 36” are preferable. (j) Examine the tests at least every six months and record EXPOSURE TESTS 195 the results on a blank form, in accordance with the standards of the American Society for Testing Materials, as given below. A. S. T. M. Method for Reporting Condition of Exposure Tests.—It is important that uniform, precise and relatively ac- curate methods for describing or measuring the character and amount of disintegration of paint coats be adopted. Unless such standards are evolved, reports made on the wearing values of paints by different investigators or observers cannot be intelli- gently or accurately compared. In considering the adoption of definitions for terms generally used in reporting condition of painted surfaces, descriptive « FIGURE 88 Member of Educational Bureau and Inspection Committee at At- lantic City Panel Tests during spring of 1910. words now in common use have been adhered to. In addition, an effort has been made to assign numerical values to these descriptive terms with the idea of ultimately working out some scheme whereby paint tests may be given a definite rating. A great deal of study is still required in order to assign values to the descriptive terms, so that the final rating may not only be 196 EXAMINATION OF PAINTS, VARNISHES AND COLORS an accurate one, but that it may really represent some well- balanced and understandable relative measure of service value. Checking.—Checking describes slight breaks in the paint coat which do not extend through to the surface painted. This is reported and rated as: Absent... ow Re Ae a 10 Very. ‘slightest 9 Slight) ie le ei ls eerie eee ee {f Considerable... a ee 1 Alligatoring.—Alligatoring describes an aggravated form of checking. The breaks in the paint coat are wider than in check- ing and usually extend almost through to the surface painted. While the condition is seldom observed, it is advisable to include the term “Alligatoring’ in the list of definitions. This condi- tion is reported and rated same as for “checking.” Cracking.—Cracking describes a break which extends down to the surface painted. It may be a break which immediately extends down to the surface painted or it may be the develop- ment of what was first checking or alligatoring. ‘On wood, cracking is usually parallel with the grain, although sometimes it is at right angles to the grain. This condition is reported and rated same as for “checking.” Flaking—Flaking describes the falling away of small pieces of the paint coat. This type of disintegration is generally the result of checking which gradually develops into cracking, end- ing in the crumbling of the paint coat. This condition is re- ported and rated same as for “checking.” Scaling.—Scaling describes the breaking away of pieces of paint of considerable size. This condition is generally the result of long cracks, on wood, usually parallel with the grain. This condition is reported and rated same as for “checking.” Blistering.—Blistering describes a condition where the paint coat is detached and raised from the surface over which it is applied, due to the formation of gases beneath the coating, in- fluenced generally by moisture behind the coating. The breaking of the blister results in peeling of the paint coat. Peeling.—Peeling describes the pulling away or falling away of large pieces of the paint coat from the surface to which it was applied. Peeling of paint is not the result of natural wear, but is due EXPOSURE TESTS 197 to improper application or to adverse conditions at the time of painting, such as moisture behind the paint coat or a faulty application of the priming coat. Gloss.—Although much depends upon the nature of the coat, it is not.advisable to report condition of gloss after a paint has FIGURE 89 Roof tests of paints and varnishes on writer’s laboratory, showing panels 45° to the vertical, which nearly doubles the speed of disintegra- tion. Also note apparatus for daily spraying panels with water, which also greatly increases speed of failure, thus making such tests ac-_ celerated roof exposure tests. . weathered for more than a year. The gloss which a paint had shortly after its application disappears in proportion to the chalking of the paint, and while it is possible to restore a gloss to a surface in some cases, by rubbing, the gloss restored is the result of abnormal treatment. Gloss may be reported as: | ree COU ee gs Oy tee 6 tC Me 10.0 VEAP rig fC Sn SS RAG Ne a a oy Pa Sere a 9.9 to 8.0 IBIACT AD Gm gn es. en ee es 7.9 to 6.0 vol) Eo a I eile RNS, os Sentie Aae OS aye ane ne 5.9 to 4.0 UI EL EME cgay 3.9. to. 2.0 ESC TESA Ta ae ie RR ore? RT ah) END, AOR Oe 1.9 to 0.0 198 EXAMINATION OF PAINTS, VARNISHES AND COLORS Chalking.—Chalking describes the reduction of the outer sur- face of the paint coat to a powdery substance, which may be re- moved by rubbing the coating with the dry finger, or a piece of soft, dark colored cloth, preferably black velvet. This condition is reported as follows: Absent Considerable Very Slight Heavy Slight Very Heavy It is a difficult matter to assign uniformly satisfactory ratings to the qualifying terms and, therefore, while the report should include the item of “chalking,” it is considered advisable to eliminate ratings. Hiding.—Hiding is judged entirely by the degree of conceal- ment of the surface painted. This property is frequently re- ferred to as “covering” which more correcly applies to the area over which a given amount of paint will spread. Hiding is re- ported as follows: NOG indie ches See ee Color.—Paints are divided into three classes, whites, tints, and colors. The degree of whiteness determines the character of report for the first class. Two things generally influence color; first, the hiding power, and second, chalking. Invariably a paint that chalks presents a better color than one that does not. The impression gained through the eye serves as the basis for report regarding the color of paint. The original appearance need not be considered. While all colors show a natural fading out, some retain a pleasing tone while others appear distinctly muddy or lack the brilliance shown when first applied. The terms used for reporting color are: Very Good Poor Good Very Poor Medium It is not considered advisable to assign rating to the descriptive terms. General Appearance.—The general appearance of painted sur- faces can really be determined only by viewing them from a distance of twenty or thirty feet, with the idea of forming an EXPOSURE TESTS 199 opinion as to whether the appearance is good, which will be influenced by such conditions as cracking, sealing, chalking, and other conditions usually found in paint wear. Exposure Tests on Varnishes.—For making exposure tests on varnishes, the following suggestions will be of value. (a) Use a series of unfilled panels of dressed maple wood 15” x 6” x %”. Apply three coats of the varnish to be tested, allowing three days for the drying of each coat. Always test at the same time a varnish of similar type, the durability of which has previously been determined by exposure. (b) After the first coat has been applied and dried indoors for three days, it should be lightly sandpapered with No. 00 sandpaper before applying the second coat. The second and third coats, however, should be applied without sandpapering or rubbing. The backs and edges of the panels should be varnished with three coats of the sample but for these surfaces the details of application need not be adhered to, as the effects of exposure on these surfaces are not considered. (c) Three days after application of the third coat, the panels should be exposed out-of-doors, 45° to the vertical, facing south. Inspection of the varnished panels should be made every two weeks, and the following reported. I. When first cracks appear. II. When cracks appear on every square inch of surface. III. When varnish may be said to have perished. Differentiate between surface cracking and cracks that go clear to wood. Make inspection based on careful visual examination, not micro- scopic examination. If panels are in a smoky community, wash lightly with water and sponge previous to examination. (d) In the same manner, panels that have been coated with black, red, yellow, green or similar colored paints may be used for exposure of the varnish. For instance some varnishes used on agricultural implements that are painted in gaudy colors, may wear well over certain colors but not over others. Infor- mation of value may be secured in this manner. If such a test is made, it is highly important that the color should be ground in one standard liquid, either japan, varnish, or oil. It should be pointed out, however, that the effect of the color upon the varnish should not be stressed unless the varnish was going to be used over some of these colors, as for instance upon agricultural implements or similar articles. , VARNISHES AND COLORS EXAMINATION OF PAINTS 200 ‘Q0BJANS JO UOI}VAS9JUISIP 10 SULYDeYO OU Ayeoyoeig ‘ystuy Jo Jeyereyo 01 onp ‘ydeagoro1uojyoyd UI UMOYS WY Jo surpeatrys Juereddy 4eoor1epun uedel MOT[EA TBAO YSTUIVA [IO Suny Surzi{jeysA1o Jo yevoo suc 16 gun ‘sulyooyo ALvuIpio Worf vouvivedde ur 4ue -loyip ‘s[eued pepunos ‘deep sejquieser yey M YALA pooe[toey UL sdVjANS sItyUy “yeoorepun uedef MoTeA TeAO0 Jonboey] Sulysiuy sson{jesorjiu Azroryse[d MOT Teed Jo syvoo OAK, 06 HANOI 201 EXPOSURE TESTS ‘lap1O su JO SuTYIIYO odVFans s[qeiepisuog yeodtepuN uvdel oJIYM T9AO YSIU I@A IedS 1O11e}yxo JO £4800 OMI, 66 Gand ‘WI YystureA SulIpunoiins Jo 10[09 1eq -We YIM poyseijU0D oie pesodxe Jueuldid Jo svete oy M ‘SyIeuUL YSNId SUIMOT[OFZ SBuUIyVYO s[qetepIsuog *}eO0d -repun uedel o41YM JIAO YSIUIVA IOLI9}xX9 JO 7e0d 9UC 66 GIN , VARNISHES AND COLORS WXAMINATION OF PAINTS 202 ‘ole SuIpUuNno.INs Jo MoOT[AA TOyTep 03 poredutod sv MOT[eA JYSI[ 918 S.104B10 aso], ‘SOUL, OYI[-IIey oyeuVUle YOIYM UWOIF S1o}e1O punos [jews puv Suryleyo sovjans peounouoid 04M “yvoo1epun uedel moyjeA 10A0 YstureA Teds JOI1e}x9 JO S}eod OMY, G6 TANS . ‘poAvoop sey ystureA Jo wiy oteym quoredde sjods on[q yysIIgq *ye00 -lepun uedel onjq-1oAoO YSIUIvA IOIIo}x9 JO S}VOD OMI, © - —6 TANS EXPOSURE TESTS 203 (e) Unless exposure tests are made in comparison with a standard sample of known previous exposure, or one that has been chosen to act as a standard in the test, then the informa- tion obtained is difficult to interpret. For this. reason, a stand- ard sample should always be included in the tests, and it should be taken from a container that has not been previously opened. Moreover, varnish exposure tests should be made on varnishes of like nature or which are intended for like exposure. For in- stance, interior varnishes which have given satisfaction for many years on interior surfaces would in most cases break down on exterior exposure in less than a month’s time. Such break- down would, of course, be no indication of their usefulness as an interior varnish. In the same way, some grades of exterior spar varnishes which would stand many months’ exposure out- side might be unsatisfactory for certain purposes inside. (f) Insofar as possible, exposure tests should be made with the varnish and the undercoats which are actually going to be used in practice. The use of three coats of a varnish which is not intended for use over itself, is, of course, incorrect. For instance, three eoats of an automobile finishing varnish on a piece of bare wood would constitute the wrong method of in- terpreting the real value of such varnish which is always used over built-up undercoats. Exposure Tests on Antifouling Pants.—For testing the com- parative resistance of compositions to the attachment of barn- acles, the writer has employed steel plates 18 by 24 inches and of about 16 gauge, provided with half-inch holes at the top. These plates are usually given one coat of anticorrosive and then one or two coats of antifouling paint. The drying time of the compositions is usually such that the three coats of paint can be applied inside of two hours’ time and the plates immediately immersed in salt water. The depth of immersion should be such that at low tide the plates will be at least two feet below the sur- face. They can be suspended with sister hooks attached to wires suspended from girders, as shown in the illustration below. The piling for supporting the girders should be preferably of un- dressed timber, as the bark on the piling resists the attacks of marine borers of the teredo or limnoria type for a considerable period of time. Examination of the plates should: be made every month by 204 EXAMINATION OF PAINTS, VARNISHES AND COLORS FIGURE 96 Test racks on seacoast for submarine exposure. The writer and R. S. Perry, Jr., have exposed nearly a thousand plates coated with proposed antifouling compositions. FIGURE 97 Patch test of antifouling paints on vessel. EXPOSURE TESTS 205 pulling them up and studying them at the surface. The inspec- tion should be for barnacles of the various species, such as bala- nus eberneus, etc., and for the presence of worm tubes, ascidians, and bryozoa. The amount of corrosion on the film and the amount of slime-forming constituents should also be noted. As a rule, paints which show a slimey deposit on the surface resist barnacle attachment better than others. For exposure tests to determine the value of copper paints for wooden bottoms, the writer has used slats of yellow pine three by one inch and about fifteen feet in length. These are nailed to a dock extending out under the water so that the major por- tion of the coated area will be below water even at ebb tide. They are pulled up every three months and a small section sawed off at the bottom to determine whether any wood-boring organisms (teredo, limnoria, etc.) have entered through the paint or through abraded surfaces. A Sub-Committee of the A. S. T. M. on varnish exposure tests expects to carry on extensive tests on metal, jananned metal, glass and wood during 1925. A report with recommendations on method of test and best type of panels to use may result from this work. CHAPTER XXII. TESTING COLORS FOR TONE AND STRENGTH Generally speaking pigment colors are bought on physical tests rather than chemical analysis. While it is true that the knowledge of the exact chemical composition of a color may be desirable for certain uses nevertheless the value and suitability of colors for most purposes can be quickly determined by physi- cal tests for overtone and strength, and while making these tests, the relative oil absorption, texture, etc., can be noted. Sugges- tions made by A. F. Brown are included below. In testing for overtone and strength it is absolutely essential that certain fundamental principles be observed, otherwise, the tests of two given samples will be misleading. The common practice of weighing roughly a given amount of color, then adding a certain number of drops of oil and rubbing an indefi- nite length of time with a spatula is apt to result in errroneous conclusions. Not only is it necessary that the dry color be accurately weighed, but the vehicle should also be weighed. Two colors ground in different vehicles should never be compared, as different vehicles produce different effects with the same color. Sufficient vehicle should always be used so that when the color has been rubbed and applied to a strip of glass, or tin, the sur- face has a high gloss. In comparing the overtones of two colors, if it so happens that one sample has higher oil absorption than the other, sufficient additional oil should be used with the color having the higher oil absorption to produce a paste of about the same consistency, otherwise the comparison will be misleading. The amount of dry color used’in making tests depends upon the type of color and the oil absorption. For C. P. Blues and C. P. Para and Toluidine Toners 0.5 grams of color is sufficient, while for C. P. Chrome Greens, C. P. Chrome Yellows, C. P. Oranges and all reduced colors, one gram of dry color is not too much. The proper amount of vehicle is dependent upon the oil absorption and the type of vehicle used. Experience has shown that where colors are to be used for certain purposes such as enamels, tests are more comparable to factory practice if rubbed in a viscous non-volatile medium such as a polymerized linseed oil about the consistency of 00 litho varnish, instead of raw or 206 TESTING COLORS ; 207 refined linseed oil. In a general way the proper proportion of dry color to vehicle is as follows: TABLE XXXVIII : - Polymerized Linseed Oil Raw Linseed Oil (00 litho varnish) Gram color | Gram oil | Gram color | Gram oil Oe sro DUCE. oa eee as 5 eS me 6 febebara LONCYs,. ol... 3) 8 a5 8 CP; Toluidine Toner......... 5 6 ee 8 C. P. Chrome Green Light.... 1.0 Pri 1.0 3 C.P. Chrome Green Medium. . 1.0 6 1.0 4 C.P. Chrome Green Deep..... 1.0 ih 1.0 5 C.P. Chrome Yellow......... 1.0 A 1.0 4 C.P. Chrome Orange......... 1.0 43 1.0 3 Reduced Chrome Greens...... 120 135 1.0 3 In weighing, it is desirable to use balanced watch glasses counterbalancing the sample against the standard with which it is to be compared; the dry colors being first weighed and then the vehicle which is placed slightly away from the color. With a little care, no trouble will be had in transferring the mass to the rubbing slab. Some operators prefer to add the oil from a burette, each drop of raw oil being assigned a definite weight. Bodied oils, however, could not be accurately weighed by such a method. The materials should be very carefully transferred to the rub- bing slab. Plate glass about 24” x 24” that has been lightly sandblasted (such as can now be obtained from any chemical glassware supply house) serves very well as a rubbing slab, and a glass muller with a 214” face is about the right size. The color and vehicle are first mixed with a spatula until there are no dry particles of color, then the resultant paste rubbed with the glass muller a definite number of times, care being taken to exert the same pressure on both samples so that the relative development will be exactly the same. The number of times a color should be rubbed depends upon the type of color and the actual factory practice as regards development. In some factories colors are well ground, but in many ostensibly efficient plants it is surprising how little atten- tion is given to securing the maximum money value by complete 208 EXAMINATION OF PAINTS, VARNISHES AND COLORS development. In a general way the number of “rubs” necessary to secure development equivalent to average factory practice is as follows: C, Poaron: Blues. oo eee 300 times G, .P.* Para-Toners24 oo eee 300 times C.F. ‘Toluidine Toners... 3... 3 See 300 times C..P. Chrome’ Greens. 2. a ee eee 150 times C. P; Chrome “¥ ellowsic (2003.4 eee 50 times Reduced Colors,.all kindss.4.. 3.2 eee 50 times Lakes. 36g ee a a 200 times In rubbing, the muller should traverse a space about three inches wide and twelve inches long, the operator pushing the muller up one side and down the other side of this strip so that all the color particles receive the same amount of attrition every rub. By one rub is meant one complete movement up and down. In testing a color which requires twenty-five rubs the color should be scraped up after fifteen rubs and then rubbed another ten times; when testing a color requiring more than twenty-five rubs the color should be scraped up with a spatula after each twenty-five rubs. After the rubbing is completed the compari- son for overtone should be made by applying liberal portions of each color to glass or tin in juxtaposition. The larger daub of color the better, but in any event each daub should not be smaller than a half-dollar and they should be placed in juxta- position, care being taken that the edges just touch but do not overlap and that there is a well defined line of demarcation. After being so placed and before comparing, a wide spatula should be lightly drawn over both at the same time to produce a color surface that will be smooth and free from ridges. In comparing for overtone, the colors should not be examined through the glass. For this reason strips of tin are preferable to glass as it effectively prevents this practice. If the colors are to be used for inks, this test may be made upon bond paper. Observation of the stained paper when held to the light will show whether the color is clear, bright or muddy. For making strength tests, it is well to have a stock paste of zinc oxide in oil. Such a paste can be made by vrinding 185 parts of zine oxide and 115 parts of OO litho oil several times through a roller mill. A strength test can then be quickly made by taking a small amount of the paste color made as outlined above for comparing the overtone and adding the proper amount of zinc oxide paste. TESTING COLORS 209 ‘For reduced colors a reduction of 20 to 1, 7. e., 20 parts zinc oxide paste to 1 part paste color, is usually sufficient but for C. P. colors a 100 to 1 reduction is necessary to get the proper idea of relative strengths. Very often two C. P. colors which apparently are about the same strength on a 20 to 1 reduction are very far apart on a 100 to 1 reduction. In making the re- duction test the best way is to counterbalance 100 milligrams of the two paste colors to be tested and then add to each, two grams of the paste zinc oxide. Before removing from the counter- balanced watch glasses mix the color with the zinc oxide, using a small spatula thus minimizing the loss on transferring, then remove from watch glass to a smooth piece of glass and mix with a, spatula until the color no longer streaks, which indicates that it is thoroughly incorporated. Never make a strength test on a rough glass and do not rub with a muller, as this develops strength that is not secured in factory practice. In the event that a 100 to 1 reduction is desired, take 500 milligrams of the first reduction, add 2 grams of zinc oxide paste and proceed as before. If it is desired to express quantitatively the tinting strength of the color, consider the standard color as having a tinting strength of 100, and then vary the amount of the standard color until the tints are matched. For example, let the amount of standard color for 100 strength test be 0.02 g. (=A). Vary this amounts in units of 5 per cent, thus 0.019 or 0.021. Let the amount taken to match a given strength— 8B, then ee. 100 B equals the tinting strength of the sample to be tested. If the tone varies it may be difficult to make this measurement. The comparison for overtone should be made as soon as the colors have been applied to the strip of glass or tin, otherwise “flooding” may result in one or both samples and there will be no basis for comparison. Generally speaking, it is good practice to have separate rub- bing glasses for each of the four general classes of color—greens, yellows, blues and reds to avoid contamination of one ‘color with another. If one glass is used for all colors, great care must be exercised to insure absolute cleanliness. It is surprising, for instance, how little chrome green is required to off-shade a prim- rose yellow. Benzol 90° is probably the best liquid for cleaning the rubbing glasses. © CHAPTER XXIII. ROUTINE TESTING METHODS FOR SOME PHYSICAL PROP- ERTIES OF WHITE PIGMENTS SUCH AS ZINC OXIDE, LEADED ZINC AND LITHOPONE The following routine tests for color, brightness, smoothness, tinting strength and settling are contributed by the Research Laboratory of the New Jersey Zinc Co. Color—Approximately 5 grams of the sample shall be thor- oughly mixed with the smallest quantity of bleached linseed oil that will produce a smooth paste. This paste shall be spread on a palette of colorless plate-glass in a smooth and even layer, that will not transmit light and is at least 1 inch by 3 inches in area. An equal amount of the standard (or each of the standards) shall be prepared in the same way, care being taken to bring the paste to the same consistency as the sample being tested. This paste shall be spread in a similar manner on the palette beside the sample, touching it, and the two compared in diffused day- light. In doing so, the palette shall be tilted so that the light will strike the surface of the pastes at different angles and the under surfaces shall also be observed through the glass. In doubtful cases, only the sample and one standard may be spread on the palette at the same time, and their edges must touch. To be on-grade, the sample must be as white as the standard. Brightness.—Five grams of the sample and 1.20 grams of bleached linseed oil shall be mixed to a smooth, uniform paste. The oil used may be determined by dropping from a point which has been standardized by counting the number of drops neces- sary to weigh 1.20 grams. The dropping shall be at a rate not greater than 70 drops per minute. All the sample and all the oil must be thoroughly incorporated. This paste shall be spread on a palette of colorless paste-glass in a smooth and even layer that will not transmit light and is at least 1 inch by 3 inches in area. When the nature of the pigment requires more oil than above ~ noted, more shall be used but comparisons shall be made. only between samples which have a like oil-vehicle ratio. An equal amount of the standard shall be prepared in the 210 ROUTINE TESTING METHODS FOR WHITE PIGMENTS Zk same way. This paste shall be spread in a similar manner on the palette beside the sample, touching it, and the two compared by observing in diffused daylight the two samples by looking through the glass. In doubtful cases, only the sample and one standard may be spread on the palette at the same time, and their edges must touch. - To be on-grade, the sample must be equal to or better than the standard in brightness or brilliancy. Smoothness and Freedom from Specks.—Approximately 5 grams of the sample shall be thoroughly mixed with the smallest quantity of bleached linseed oil that will produce a smooth paste. This paste shall be spread on a palette of colorless plate-glass in a smooth and even layer that will not transmit light and is at least 1 inch by 3 inches in area. An equal amount of the standard shall be prepared in the same way, care being taken to bring the paste to the same con- sistency as the sample being tested. This paste shall be spread in a similar manner on the palette beside the sample, touching it, and the two compared in diffused daylight. In doing so, the palette shall be tilted so that the light will strike the surface of the pastes at different angles. . In doubtful cases, only the sample and one standard may be spread on the palette at the same time, and their edges must touch. To be on-grade, the sample must contain no more granular or foreign matter than the standard. This is to be determined by the feel under the knife and the amount of noise made in rubbing down and by observation of the surfaces after the pastes have been spread on the palette. Tinting Strength—Five grams of the sample, 0.5 grams of ultramarine blue and 1.20 grams of bleached linseed oil shall be mixed to a smooth, uniform paste of uniform color throughout. The oil used may be determined by dropping from a point which has been standardized by counting the number of drops neces- sary to weigh 1.20 grams. The dropping shall be at a rate not greater than 70 drops per minute. The mixing shall be done by rubbing lightly with a spatula whose blade is not over 5 . inches long. All the sample, blue and oil must be thoroughly incorporated. This paste shall be spread on a palette of color- less plate-glass in a layer that will not transmit light. 212 EXAMINATION OF PAINTS, VARNISHES AND COLORS The standard shall be prepared in the same way and spread in a similar manner on the palette beside the sample, touching it. Another standard paste shall be prepared by mixing 5.5 grams of the standard, 0.5 grams of ultramarine blue and 1.32 grams of bleached linseed oil in the same way and spread in a similar manner on the palette beside the sample, touching it. In doubtful cases, only the sample and the two standards may be spread on the palette at the same time and the sample must be in contact with both standards at the edges. To be on-grade, the sample must not be darker than the first standard and not lighter than the second standard when ob- served through the glass. Settling in Water.—This test shall be made in a flat-bottomed glass tube of 11/16 inch diameter, 6 inches height and uniform bore. Twenty-seven cc. of water should fill it to a height of 43/4, inches with an allowable plus or minus variation of 1/16 inch. Five grams of the sample shall be put into the tube after the latter is half filled with water. The product and water shall be well mixed with a piece of wire about 14 or 12 gauge and the tube filled with water to a height of 434, inches. The wire is to be removed and washed off in the process of adding this water. The tube shall then be shaken vigorously 80 times, the thumb being held over the opening in the top. After shaking, it shall be placed in a rack so that it stands vertically and the height of the column of the product measured at the end of 1, 2, 3 and 24 hours. An equal amount of the standard shall be treated in the same way. To be on-grade, the height of column of the sample must be within 10 per cent plus or minus of the height of column of the standard at the end of 24 hours. CHAPTER XXIV. ANALYSIS OF PAINTS AND PAINT VEHICLES When examining a sample of mixed paint, it is customary to weigh the paint and container, subsequently deducting the weight of the cleaned container to determine the weight per gal- lon. About an ounce or two of the clear liquid above the settled pigment can b poured off to use for analytical purposes. The balance of the liquid can then be poured into a large container and the condition of the settled pigment determined by exam- ining with a large spatula. The presence of granular matter, metallic soaps, etc., is determined. The presence of soaps precipi- tated out of the liquid upon the sides of the can above the set- tled pigment should also be looked for. The settled pigment should then be broken up carefully by pouring back the liquid and the mixture stirred to a uniform mass. For this purpose, it is necessary to “‘box” the paint back and forth from one large can to another in order to get a thoroughly uniform mixture for analysis. Otherwise, low results might be shown in the per- centage of pigment present. A small amount of the uniform sample of paint thus obtained, together with the small sample of the clear liquid originally obtained previous to boxing, can be used for the analytical tests. The amount of clear liquid taken should be figured in calculating the percentage of pigment in the paint. Composition of Liquid Part.—The vehicle or liquid portion of paints may contain various fixed animal, vegetable or mineral oils, oleo-resinous varnishes, turpentine, mineral distillates, ben- zol and driers. Percentage of Liquid by Ignition Method.—The percentage of vehicle in the uniform sample of paint previously obtained may be found by placing a weighed portion in a porcelain cru- cible and slowly igniting it to burn off the organic constituents. By carefully regulating the heat, the oil and volatile thinners will be slowly burned off, leaving the pigment behind, which may then, be weighed, calculating the vehicle by difference. This method is a rapid one and works well with some pigments. When pigments are present which show an appreciable loss on igni- tion, or blacks or blues, this method is not to be relied upon. 213 214 EXAMINATION OF PAINTS, VARNISHES AND COLORS Percentage of Liquid by Extraction Methods.—Another good method of separating the vehicle from a paint is to place a por- tion in a large tube, adding a considerable quantity of benzol, petroleum ether, or that portion of gasoline distilling below 120° C., subsequently centrifuging. Pigments which settle slowly are thrown down very rapidly by this method. The process is repeated three or four times in order thoroughly to free the pig- ment from oil. After drying, the pigment is weighed and the percentage of vehicle determined by difference. In case a cen- trifuge is not available, the vehicle of many paints may be sepa- rated by simply shaking a portion of the paint in a long test- tube with benzol, allowing the pigment to settle, repeating the extraction until the oil is thoroughly removed. Some operators have from time to time used Soxhlet extractor for the determination of the vehicle of a paint. This method is rather slow and does not always give satisfactory results. It must be remembered that no method of extraction of the oil from a paint will give absolute results. The last traces of oil cannot be removed from the pigment which is probably due to the fact that many pigments such as lead and zinc react with the oil, producing small quantities of insoluble soaps which are not completely dissolved by the solvent. | In the extraction of paints, the choice of a solvent is impor- tant. When benzol (90°) is not available, it may be replaced by gasoline that has been redistilled, using the light fraction coming over below 120° C. This cannot be used, however, when varnish resins other than rosin are present, as they are insoluble therein. A good solvent often used by the writer may be made of Ethyl Ether 10 Volumes, Benzol 6 Volumes, Methyl Alcohol 4 Volumes and Acetone 1 Volume. There are some pigments which by reason of their low specific gravity, colloidal nature or partial solubility can never be com- pletely separated from oil, either by settling, centrifuging or extraction. Of these the most commonly met with are lamp- black and other forms of carbon, zinc oxide and Prussian blue. Colloidal pigments such as zine oxide are very troublesome in this respect. When these pigments, however, are present in a paint in considerable percentage, the difficulty of their sepa- ration may be avoided by adding to the paint three or four times its volume of fuller’s earth, diluting the mixture in a large test-tube with gasoline or petroleum ether and either centrifug- ANALYSIS OF PAINT VEHICLES 215 ing or placing in a rack to settle. The fuller’s earth carries down the colloidal pigments and the separation is sharp and easy. This method, of course, is simply used to extract the vehicle present. The pigment resulting from the separation cannot be used for analysis on account of admixture with the fuller’s earth. | In some cases the pigments in paste colors made of lamp- black and Prussian blue cannot be separated from the vehicle portion. The amount of Prussian blue present, however, may be determined by making a Kjeldahl-Gunning determination on a portion of the entire paint, multiplying the nitrogen found by 4.4. For the determination of the lampblack present, a portion of the entire paint may be boiled with an excess of alcoholic potash until all of the oil is saponified. The mixture is then decanted through a filter and washed, first with hot alcohol and then with hot water. This affords a very good separation of the vehicle from the pigment of such paints. By this method, the Prussian blue which may be present is partially destroyed, the iron content remaining admixed with the black pigment on the filter. Separation of Vehicle Components.—When possible, it is ad- visable to determine the constituents of the vehicle upon that sample that has been removed from the top of the settled can of paint. A weighed portion of this vehicle may be placed in a tared flask and attached to a Liebig condenser. Heating to 180° C. or lower will drive off nearly all the volatile constitu- ents. The composition of the distillate may be determined by the methods given under the Examination of Turpentine. (See specifications in back of volume.) A portion of the residue in the flask, which consists of oils, driers, gums, etc., may be transferred to a crucible and ignited. The residue may then be weighed and calculated to ash. The ash should be analyzed for lead, manganese and other driers. Another portion of the original vehicle may be evaporated in an atmosphere of CO, (prevents oxidation) to remove the volatile constituents. A portion of the oil residue may then be ex- amined for iodine number and other constants. In some in- stances it would be advisable to make a saponification and ex- traction of the fatty acids from this residue, determining the iodine number on the fatty acids. Water.—For a direct determination of the percentage of 216 EXAMINATION OF PAINTS, VARNISHES AND COLORS water in a paint, the analyst may place a weighed quantity (ap- proximately 100 grams) of the paint in a metal still, mixing it with an equal quantity of sand. Distillation will drive off the water and other volatile constituents which will separate into two layers in the graduate, or if no metal still is available, a direct distillation with Toluol (water saturated) may be re- sorted to. Direct Distillation for Volatiles—For a direct determination of the volatile constituents in a paint, a.sample may be distilled in vacuo. This is-easily managed wherever a vacuum pump is available and avoids the necessity of overheating the oil. When distilling by this method, a sample of the clear vehicle should not be heated above 150° C. and neither should the solvent be volatilized in such a way as to allow the oil to be in contact with air, as it will oxidize rapidly while warm and its iodine number be very much lowered. The following standard method for volatile, which is Aer convenient and accurate, may be used in any case and particu- larly where it is difficult to secure sufficient clear vehicle for distillation. Approximately 1.5 grams varnish or 3 to 5 grams of jaint are weighed by difference from a stoppered vial into a weighed shallow flat-bottom metal dish (ordinary friction top lid) 8 c.m. in diameter. The dish is heated in a well ventilated air oven at 105° to 110° C. until no further loss occurs, generally 3 hours. Loss is considered volatile thinner. In paints, any water present, as separately determined, must be allowed for. Detection of Resinates—To determine whether the drier in a paint is of the resinate type or linoleate type, a few drops of the oil vehicle may be mixed on a porcelain plate with one or two drops of acetic anhydride, subsequently adding a drop of sulphuric acid. Upon the addition of the sulphuric acid, a flash of purple color, turning to dark brown, will be shown where rosin is present. If rosin should be present in the vehicle to a considerable extent, the oil will have a very high acid num- ber. The approximate percentage of rosin present may be de- termined by shaking a portion of the vehicle with 95 per cent alcohol in a separatory funnel, subsequently separating the al- coholic extract, evaporating and weighing the residue. Detection of Various Oils —Chinese wood oil may be detected in the vehicle by mixing the oil with an equal volume of a satu- a) a ANALYSIS OF PAINT VEHICLES 217 rated solution of iodine in petroleum ether, allowing the mix- ture to stand in direct sunlight. Under these conditions, a peculiar, insoluble, spongy polymer of one of the fatty acids of Chinese wood oil is shown. Fish oil can usually be detected by its odor and the dark red color during saponification. The pres- ence of soya bean and other vegetable oils is in some cases diffi- cult to detect. The iodine numbers of these oils, however, are all lower than that of linseed oil. It must be remembered, how- ever, that the iodine number of boiled linseed oil is lower than that of raw oil and that the iodine number of oils extracted from many paints is usually lower than shown by the original oil. In the presence of considerable quantities of drier, it is always advisable to extract the fatty acids from oil and make the iodine determination upon them. Determination of hexa- bromides gives best information as to type of oil present. The distillate from the paint vehicle may consist of turpen- tine, mineral distillates, benzol and similar solvents. The pres- ence of benzol is readily detected by adding a few drops of the distillate to a small quantity of a mixture of concentrated nitric and sulphuric acids. Upon heating this mixture, the character- istic odor of nitro-benzol will be recognized if benzol is pres- ent. Mineral distillates from petroleum are easily detected by the polymerization method given under Turpentine Specifica- tions. CHAPTER XXV. ANALYSIS OF PAINT OILS Although linseed oil is used to the greatest extent in paints, some other oils occasionally find application in the manufacture of special paints. The following have been used for this pur- pose: soya bean oil, perilla oil, corn oil, cottonseed oil, sun- fiower oil, lumbang oil and similar vegetable oils; menhaden oil, whale oil, herring: oil, and similar marine animal oils of rela- tively high iodine number. Constants found on oils examined in the writer’s laboratory are given in Table XX XIX. There are given below methods for the analysis of linseed oil, in accordance with the latest practice developed by the U. S. Government Interdepartmental Committee on standardi- zation of paint specifications and the American Society for Test- ing Materials. These methods may be followed in examining any of the other oils mentioned above, except for iodine value on those of the aleurites genus. ANALYSIS OF LINSEED AND SIMILAR OILS Solutions Required.—The following reagents will be required: Acetone that will pass the specification of the United States Pharmacopeeia. Acid Calcium Chloride Solution.—Saturate with calcium chloride a mixture of 90 parts water and 10 parts HCl (sp. gr. — 15185 Standard Sodium Thiosulfate Solution.—Dissolve pure sodium thiosulfate in distilled water that has been well boiled to free it from carbon dioxide in the proportion so that 24.83 g. crystallized sodium thiosulphate will be present in 1000 cc. of the solution. It is best to let this solution stand for about two weeks before standardizing. Standardize with pure resublimed lodine. (See Treadwell-Hall, Analytical Chemistry, Vol. II, third edition, p. 646.) This solution will be approximately N/10 and it is best to leave it as it is after determining its ex- act iodine value, rather than to attempt to adjust it to exactly N/10 strength. Preserve in a stock bottle with a guard tube filled with soda lime. Starch Solution.—Stir up 2 or 3 g. of potato starch or 5 218 ANALYSIS OF PAINT OILS 219 TaBLE XXXIX—Oils Examined in Writer’s Laboratory se S e ep | ae Oil. Species. & co iag Orcs “s o Sone eet ne & se es eee ‘S Se Bio D Zi les ON R A Grandifolia A. Palo Maria...... Calophyllum.... 193. |46. 1.4743 -) Inophyllum TD Bendis ta. 3. Periilay. oy 0s 5: 188. | 2.0 | 1.4874| & Ocimoides . s Poppyseed....... Papaver ...... - A Le Vl ee he aed one neg es O Somniterrum = Raisinseed (Grape-|.....-.--+-+++-- 198-2 |-475-| 1.471041 seed). es ORIEL OTL 9 alae PIS ee ws ees SBA Osada tor Palustris Rubberseed...... le Vetin eae 5 ou: 10380 (50 20M Seen ae Brasiliensis SeOESAMO- gels. +: Sesamum....... LOO Vel ere he Orientale & In- dicum Soya Bean....... SO) ok eee Oe ne 189. | 2. 1.4813 ‘Hispida Sunflower..... Helianthus..... 189.3] 7 1.4796 Annus umbang:..../:5 Aleurites....... 192.0) 1. 1.4770 (Candlenut). Moluccana Lumbang (Soft). .| Aleurites....... 194.0) 4. 1.4929 Trisperma ~ Peanit va... s- « Nera OPUS no tagtte bate ee 193.0} 2. 1.4790 Z, Hypogaea = Tung (American) .| Aleurites....... 194.6 1.5170 Fordii o Tung (Chinese)...| Aleurites....... 192.0} 4 1.5170 te Fordiu ce POM EATAIE Gide jes ol eae: Juglans Panes 19g 0L ee 1.4770 Regia Wood (Japanese) .| Aleurites....... 193.2 1.5080 Cordata — ee | 220 EXAMINATION OF PAINTS, VARNISHES AND COLORS TABLE XXXIX—Continued—Oils Examined in Writer's Laboratory is 5 é ay 2 r=| P rs > 2 iS) oO < © z ees 2 = Oil. Species. e) Zt g3 5 ev = os | | Z, ay MOO) os 6 > 20 Sisie| Ba | 24 | Z Hie Pidiis| SO] & at, coe Na|a 2 Channel Cathsiix. is ve) .923 | 123.0) 192.0/10.9 | 1.4741 Pur Beak oe AF PROCGL Ae oe .926 |-132.4) 182.4) 90 eae Vitulina Ete. Grayish iy, ces ee eee ee .916 | 185.7; 180.1) 2.0 | 1.47038 | — Menhaden....... Alosa Menhaden | .932 | 158.0] 187.0) 3.9 | 1.4850 = (Brevoortia Tyr- me ranis) _ Salmoty.cc eee Salmo. citi .927 | 159.0} 183.0] 9.8 | 1.4788 | 4 Salar & Sarilines (4. 0 wie Co OoMIpen ste ee .919 | 134.6) 177.3]10.4 | 1.4800 | = Sardinus 4 SUEELT Rewie “eee ke cane ee Bs a Be vas oe ee .910 | 132-8} 158.9] 5.2 | 1.4815 z Shark Liver...... Borealis #2 .922 | 135.9] 62.2) 1.3 | 1.4708 > Scymnus es Th Skate Liver...... PUUAtNE es .932 | 151.6) 179.9) 1.8 1 bavi2 aS Vulvaris = Une Ah oP ens Uh keer ie .9383 | 184:0) 190.0) > [at ee 2) Whale, =... os...) Go Baloenas. =... 924) 14s 7 ee 9.2.1 | 48200) = Yellow Tailfish...| Seriola......... .932 | 180°0; 190.0) eee Dorsalis —VWvVUuHRuRHexexeyeoooo>> qq eee g. soluble starch with 100 ce. of 1 per cent salicylic acid solution, add 300 to 400 cc. boiling water, and boil the mixture until the Starch is practically dissolved. Dilute to 1 liter. Potassium Iodide Solution—Dissolve 150. g. of potassium iodide free from iodate in distilled water and dilute to 1000 cc. Hanus Solution.—Dissolve 13.2 g. of iodine in 1000 cc. of glacial acetic acid (99.5 per cent) that will not reduce chromic acid. Add enough bromine to double the halogen content, de- termined by titration (3 cc. of bromine is about the proper amount). The iodine may be dissolved by the aid of heat, but the solution should be cold when the bromine is added. Standard Sodium Hydroxide Solution.—Prepare a stock con- centrated solution of sodium hydroxide by dissolving NaOH in water in the proportion of 200 g. NaOH to 200 cc. water. Allow this solution to cool and settle in a stoppered bottle for several days. Decant the clear liquid from the precipitate of sodium carbonate into another clean bottle. Add clear barium hydroxide solution until no further precipitate forms. Again allow to settle until clear. Draw off about 175 cc. and dilute to Tee ar a ey ANALYSIS OF PAINT OILS 221 10 liters with freshly boiled distilled water. Preserve in a stock bottle provided with'a large guard tube filled with soda lime. Determine the exact strength by titrating against pure benzoic acid (C,H.COOH) using phenolphthalein as indicator. (See Bureau of Standards Scientific Paper No. 183.) This solution will be approximately N/4, but do not attempt to adjust it to any exact value. Determine its exact strength and make proper corrections in using it. ie Alcoholic Sodium Hydroxide Solution—Dissolve pure NaOH in 95 per cent ethyl alcohol in the proportion of about 22 g. per 1000 ce. Let stand in a stoppered bottle. Decant the clear liquid into another bottle, and keep well stoppered. This solu- tion should be colorless or only slightly yellow when used; it will keep colorless longer if the alcohol is previously treated with NaOH (about 80 g. to 1000 cc.), kept at about 50° C. for 15 days, and then distilled. For an alternate method see Jour- nal, American Chemical Society, 1906, p. 395. Half Normal Sulfuric Acid Solution.—Add about 15 ce. H.SO, (sp. gr. 1.84) to distilled water, cool and dilute to 1000 ec. Determine the exact strength by titrating against freshly standardized NaOH or by any other accurate method. Hither adjust to exactly N/2 strength or leave as originally made, ap- plying appropriate correction. Methods.—The oil shall be tested in accordance with the fol- ‘lowing methods: General.—The laboratory sample shall be thoroughly mixed ‘by shaking, stirring, or pouring from one vessel to another and the samples for the individual tests taken from this thoroughly mixed sample. Loss on Heating at 105 to 110° C.—Place 10 g. of the oil in an accurately weighed 200 cc. Erlenmeyer flask; weigh. Heat in an oven at a temperature between 105 and 110° C. for 30 minutes; cool and weigh. Calculate the percentage loss. This determination shall be made in a current of dry carbon diox- ide gas. Foots.—With all materials at a temperature between 20 and 27° C., mix, by shaking in a stoppered flask for exactly one minute, 25 cc. of the well-shaken sample of oil, 25 ec. of acetone and 10 cc. of the acid calcium chloride solution. Transfer the mixture to a burette where settling can take place for 24 hours. The temperature during this period should be between 20 and ete O 222 EXAMINATION OF PAINTS, VARNISHES AND COLORS The volume of the stratum lying between the clear calcium chloride solution and the clear acetone and oil mixture is read in tenths of a cubic centimeter or a fraction thereof. This reading multiplied by four expresses the amount of foots present as percentage by volume of the oil taken. Specific Gravity—Use a pyknometer accurately standardized and having a capacity of at least 25 cc., or any other equally accurate method, making the test 15.5° C., water being 1 at T5.baG, Acid Number.—Weigh from 5 to 10 g. of the oil. Transfer to a 300 cc. Erlenmeyer flask. Add 50 cc. of neutral 95 per cent ethyl alcohol. Put a condenser loop inside the neck of the flask. Heat on a steam bath for 30 minutes. Cool and add phenophthalein indicator. Titrate to a faint permanent pink color with the standard sodium hydroxide solution. Calculate the acid number (milligrams KOH per gram of oil). Saponification Number.—Weigh about 2 g. of the oil in a 300 ec. Erlenmeyer flask. Add 25 cc. alcoholic sodium hydroxide solution. Put a condenser loop inside the neck of the flask and heat on the steam bath for one hour. Cool, add phenolph- thalein as indicator, and titrate with N/2 H;SO,. Run two blanks with the alcoholic sodium hydroxide solution. These should check within 0.1 cc. N/2 H,SO,. From the difference between the number of cubic centimeters of N/2 H,SO, required for the blank and for the determination, calculate the saponifi- cation number (milligrams KOH required for 1 g. of the oil). ~ Unsaponifiable Matter.—Weigh 8 to 10 g. of the oil. Trans- fer to a 250-cc. long-neck flask. Add 5 ec. of strong solution of sodium hydroxide (equal weights of NaOH and H,O), and 50 ce. 95 per cent ethyl alcohol. Put a condenser loop inside the neck of the flask and boil for two hours. Occasionally agi- tate the flask to break up the liquid but do not project the liquid onto the sides of the flask. At the end of two hours remove the condenser and allow the liquid to boil down to about 25 cc. Transfer to a 500-cc. glass-stoppered separatory funnel, rins- ing with water. Dilute with water to 250 cc., and add 100 cc. redistilled ether. Stopper and shake for one minute. Let stand until the two layers separate sharp and clear. Draw all but one or two drops of the aqueous layer into a second 500-cc. separa- tory funnel and repeat the process using 60 cc. of ether. After thorough separation draw off the aqueous solution into a 400-ce. ANALYSIS OF PAINT OILS 223 beaker, then the ether solution into the first separatory funnel, rinsing down with a little water. Return the aqueous solution to the second separatory funnel and shake out again with 60 cc. of ether in a similar manner, finally drawing the aqueous solu- tion into the beaker and rinsing the ether into the first separa- tory funnel. Shake the combined ether solution with the accumulated water rinsings and let the layers separate sharp and clear. Draw off the water and add it to the main aqueous solution. Shake the ether solution with two portions of water (about 25 cc. each). Add these to the main water solution. Swirl the separatory funnel so as to bring the last drops of water down to the stopcock, and draw off until the ether solu- tion just fills the bore of the stopcock. Wipe out the stem of the separatory funnel with a bit of cotton on a wire. Draw the ether solution (portionwise if necessary) into a 250-cc. flask and distill off. While still hot, drain the flask into a small weighed beaker, rinsing with a little ether. Evaporate this ether, cool and weigh. Hanus Iodine Number.—Place a small quantity of the sample in a small weighing burette or beaker. Weigh accurately. Transfer by dropping about 0.15 g. (0.10 to 0.20 g.) to a 500-cc. bottle having a well-ground glass stopper, or an Erlenmeyer flask having a specially flanged neck for the iodine test. Re- weigh the burette or beaker and determine the amount of sam- ple used. Add 10 cc. of chloroform. Whirl the bottle to dis- solve the sample. Add 10 cc. of chloroform to each of two empty bottles like that used for the sample. Add to each bot- tle 25 cc. of the Hanus solution and let stand with occasional _ shaking for one-half hour. Add 10 cc. of the 15 per cent potas- sium iodide solution and 100 cc. of water, and titrate with standard sodium thiosulfate using starch as indicator. The titrations on the two blank tests should agree within 0.1 cc. From the difference between the average of the blank titration and the titration on the samples and the iodine value of the thiosulfate solution, calculate the iodine number of the sam- ples tested. (Iodine number is centigrams of iodine to 1 g. of sample.) Note.—The unsaponifiable oil from adulterated drying oils is volatile and will evaporate on long heating. Therefore heat the beaker on a warm plate, occasionally blowing out with a current of dry air. Discontinue heating as soon as the odor of ether is gone. 224 EXAMINATION OF PAINTS, VARNISHES AND COLORS Color.—Use Gardner-Holdt Color Meter or prepare a fresh solution of pure potassium bichromate in pure colorless H,SO, (sp. gr. 1.84). This solution should be in the proportion of 1.0 g. potassium bichromate to 100 cc. (184.0 g.) H:sSO: Place the oil and ‘colored solution in separate thin-walled, clear glass tubes of the same diameter (1 to 2 ecm.) to a depth of not less than 2.5 em. and compare the depths of color by looking trans- versely through the columns of liquid by transmitted light. HEXABROMIDE TEST FOR DETERMINING PURITY OF LINSEED OIL The determination of the hexabromide value of linseed oil is probably the only method whereby adulteration with small amounts (5 per cent or greater) of soya bean or some similar oil can be detected. This test shows the percentage of ether- insoluble bromides which can be formed from the mixed fatty acids of a given sample of linseed oil. It has been found that the Steele-Washburn method for hexa- bromides yields a fairly constant figure of 46% for unadulter- ated commercial oils. Soya bean oil has been found to yield not over 6% of hexa- bromides, while cottonseed oil shows a zero yield. The calculation given below will indicate how an addition of 10% soya bean oil to linseed oil will not lower the iodine value Folow the allowable minimum but will lower the hexabromide value to a marked degree: Assume a linseed oil with iodine number of 185 tu be adulter- ated with 10% of soya bean oil, iodine value of 130. : Then: 90 X 185 = 166.5 10 130 = 30 Iodine number of mixture = 179.5 Assume that the same linseed oil has a hexabromide yield of 46% while the soya bean oil yields 6% of hexabromides. Then: 90 xk 46 = 41.4 10X 6= 6 Hexabromide yield of mixture = 42.0 A hexabromide yield of 42.0% would be much lower than any normal linseed oil and would indicate adulteration, while an iodine number of 179.5 would not indicate adulteration. The two methods (Steele and Washburn or Bailey’s modifica- tion thereof) by which the hexabromide test may be made, are ANALYSIS OF PAINT OILS 225 given below. The Bailey modification differs from the Steele and Washburn method in that an acetic acid-bromide solution is used instead of a chloroform-bromide solution. The Bailey modification also entirely eliminates the use of chloroform from the reaction mixture and does not require “amylene” or other reagent for removing the excess of bromide after the bromina- tion of the fatty acids. The Bailey modification, however, re- quires the precipitated hexabromides to first stand over night in an ice chest instead of immediate washing. STEELE AND WASHBURN METHOD A. Preparation of Reagents. The following reagents are necessary: 1. Chloroform.—Shake ordinary U. S. P. chloroform with Several portions of water to wash out all the alcohol. Dry the product with granulated anhydrous calcium chloride over night in order to remove all traces of water. Decant from the cal- cium chloride and distil. Add to the distillate 3 cc. of absolute ethyl alcohol for every 100 cc. of chloroform. Keep in a stop- pered brown bottle. 2. Bromide Solution.—Mix one part ne volume of C. P. bro- mine* with two parts by volume of chloroform, prepared as above. This solution must be made up fresh each day because it deteriorates upon standing. 3. Wash Ether.—Shake ordinary ethyl ether with ten per cent of its volume of ice cold distilled water. Separate and re- peat the washing three times. Dry the washed ether with fused calcium chloride overnight. Decant the ether through a folded filter into another flask and add thin slices of sodium. Warm gently on a steam bath under a reflux condenser until the evolu- tion of gas by action of the sodium has practically ceased and bits of freshly cut sodium remain bright in the ether. Distil the ether into a dry bottle and add an excess (at least three grams per liter) of finely powdered hexabromide of the fatty acids of linseed oil previously prepared. If no hexabromide is on hand from previous determinations it may be easily prepared as follows: In a centrifuge tube dissolve about 5 grams of the fatty acids of linseed oil in 15 to 20 ce. of chloroform. Place * The authors have observed that samples of bromine marked “C. P.” often contain considerable amounts of non-volatile material. All bromine which is used must be redistilled unless it is found that 5 gms. leave no weighable residue upon evaporation. 226 EXAMINATION OF PAINTS, VARNISHES AND COLORS the tube in a freezing mixture and add slowly with shaking, bromine solution until a slight red color is permanent. Add a few drops of amylene to take up excess of bromine. Whirl in a centrifuge until the precipitate has settled and then pour off the chloroform. Rub up the precipitate with 20 cc. of cold absolute ether, whirl in a centrifuge and pour off the wash ether. Repeat the washing with 3 more 20 cc. portions of ether. After drying, the hexabromide is pure enough for the prepara- tion of wash ether. Shake at intervals for two or three hours or allow the mixture to stand over night. Then place the bottle in ice water so that the ether solution will be at zero or not about 2° C. for three hours. Decant the ether solution rapidly through a folded filter into a dry bottle and keep tightly corked in order to prevent loss of ether by evaporation. 4. Amylene.—This material may be purchased from the East- man Kodak Company. It is one of the organic chemicals pre- pared in the laboratory of the University of Illinois. It may be prepared in small quantities from amyl alcohol by the method of Adams, Jour. Am. Chem. Soc., 1918, page 1950. B. Preparation of the Fatty Acids. Weigh approximately 50 grams of linseed oil into a 114 liter Florence flask, and add 40 cc. NaOH solution (sp. gr. 1.4) and AQ ec. of alcohol. Place the mixture on a steam bath and heat for about 14 hour. Add 1 liter of hot distilled water and insert into the neck of the flask a 2-hole rubber stopper carrying a tube which projects into the flask so that its end is slightly above the liquid, and pass a stream of CO, through the tube - into the flask. The soap mixture may then be heated, to re- move the alcohol, either over a free flame or on the steam bath. If the free flame is used, a capillary “boiler” must be placed in the liquid, since otherwise the soap solution will bump badly. If excessive foaming takes place the current of CO, should be increased until it is strong enough to break up the foam. If the solution is heated on the steam bath, usually about 2 or 3 hours is required to remove the alcohol, while if it is boiled over a free flame, one-half hour is usually sufficient. After the alcohol has been removed, cool the soap solution and acidify with dilute HCl (1-1). Insert a 3-hole rubber stopper, carry- ing two glass tubes arranged as for a wash bottle, leaving the third hole in the stopper open for an outlet for the CO,. The inlet tube should extend to just above the layer of fatty acids, ANALYSIS OF PAINT OILS 227 and the outlet tube should extend to the bottom of the flask. It is essential that the outlet tube should not extend down more than an inch or two outside of the flask, as otherwise siphoning would take place, causing the liquid to boil inside the tube. Pass a stream of CO, through the system, and boil gently, uSing a capillary boiler to prevent bumping, until the layer of fatty acids is clear. Plug the hole in the stopper which acts as an outlet for the CO,. The lower layer will be forced out through the outlet tube by the pressure of the CO,. In this manner remove as much water as possible without losing any of the fatty acids, then remove the stopper and add about 500 cc. of hot distilled water, shake thoroughly so that the fatty acids are well washed, allow the fatty acids to separate and siphon off the wash water as before. Repeat the washing until the wash water does not give an acid reaction with methyl orange. Be- fore removing the last washing, insert a capillary boiler and boil gently until the fatty acid layer is clear. After the last washing, remove the stopper and suck up with a pipette the last few globules of water. Filter the hot fatty acids through a folded filter under an evacuated bell jar and keep in a well stoppered bottle. C. Preparation of Hexabromides. Weigh accurately in a weighed centrifuge tube (approxi- mately 614 inches long by 1 inch in diameter) 1.00 gram (pius or minus 0.05 gram) of linseed fatty acids, prepared as given above. Dissolve in 10 ec. of chloroform and place the tube in a freezing mixture kept as near—5° C. as possible, made by adding a little dilute hydrochloric acid to finely cracked ice. Add bro- mine solution from a burette at the rate of one or two drops per second, shaking the tube well during the addition. At first the bromine color will be rapidly discharged, but later the mixture will assume a permanent orange color indicating a slight excess of bromine. For most fatty acids of linseed oil about 1 cc. of the bromine solution will be found necessary to give the orange color. At this point run in rapidly 0.5 ce. more of the bromine solution, shake well, and allow the tube to stand in the ice mix- ture for ten minutes. Remove the tube from the freezing bath and add amylene drop by drop with shaking until the bromine color has entirely disappeared. Usually five to six drops of amylene are sufficient, but a slight excess does no harm. The addition of bromine solution must never be done in direct sun- light. 998 EXAMINATION OF PAINTS, VARNISHES AND COLORS Attach the tube to a good water vacuum pump (one which will indicate a pressure not greater than 40 mm. of mercury) by means of a new one-hole rubber stopper. Evaporate the chloroform in a vacuum, warming the tube in water at 50 to 60° C. to hasten evaporation. The tube must be constantly shaken to prevent bumping of the chloroform. Towards the end of the evaporation, when the contents of the tube become more viscous, rotate and tilt the tube so that the oil will flow about half way up the sides and thus present more surface for evap- oration. When practically all the chloroform has been evap- orated, place the tube in a bath at 55 to 60° C. for fifteen min- utes, keeping the suction on. Detach from the pump and place the tube in a bath of finely cracked ice and water. When the tube is cold pour down its sides 20 cc. of cold wash ether, as prepared above. The wash ether should have been previously placed in four corked test tubes graduated at 20 cc. by a file mark and kept at 0° C. in an ice bath. Thoroughly stir and rub up the bromide mixture with a rod, breaking up all the lumps. Return the tube to the ice bath for two minutes and then whirl in a centrifuge until the precipitate has settled into a hard cake and the supernatant liquid is clear. Return the tube to the ice bath for two min- utes and then pour off the wash ether, making sure that no solid material is lost. Repeat the washing of the hexabromide pre- cipitate three times in exactly the same way, using three 20 cc. portions of ice-cold wash ether and rubbing up the precipitate thoroughly each time. Use a weighed stirring rod and wash the precipitate adhering to the rod into the tube with the wash ether at each washing of the hexabromide. Afterwards ary and weigh the rod plus the slight coating of precipitate and add the weight of material on the rod to the weight of the main portion of hexabromide. After the fourth ether washing has been poured off, carefully incline and tap the tube and spread the hexabromide precipitate part way up the sides. Warm the tube in water at 50 to 60° C. until most of the ether has evap- orated. Attach to the suction pump and place the tube in a bath at 60 to 70° C. for fifteen minutes. Detach the tube from the pump, cool in cold water to room temperature, wipe dry with a towel and weigh at once. Dry the tube to constant weight in an oven at 100-110° C. The total weight of the pre- cipitate times 100 divided by the weight of fatty acids taken, ANALYSIS OF PAINT OILS 229 gives the hexabromide percentage. The hexabromide should dry pure white. Special Precautions: 1. Have the chloroform dry and adjust its alcohol content to three per cent. 2. Make sure that all the chloroform is evaporated from the impure hexabromide before adding wash ether. This will be accomplished if the water pump indicates a pressure not greater than 30-40 mm. and the tube is heated in the bath at 60° C. for two-thirds of its length. 3. Make sure that the wash ether is anhydrous and free from alcohol and that it is saturated with hexabromide at 0° C. Un- less the wash ether is allowed to stand at 0° C. for a sufficient length of time before filtering off excess hexabromide, it will be super-saturated at 0° C. and will give high results. Care Should be taken to prevent appreciable loss of ether by evap- oration; it is well to cool the stock bottle of wash ether on hot days before uncorking. 4. Make sure that the centrifuge tube containing hexabro- mide and the wash ether are kept as near 0° C. as possible dur- ing the process of washing. The finely cracked ice should be re- plenished at intervals. 5. It has been found that low and non-concordant hexabro- mide results on pure linseed oil by the new method can nearly always be traced to the use of a faulty vacuum pump or to faulty rubber connections. Therefore, the operator should convince himself by test with a mercury manometer immediately before making the determination that his pump, as used, will give a vacuum of not greater than 30 mm. mercury. Heavy walled pressure tubing should always be used for connections. A faulty pump or faulty rubber connections usually means that the chloroform is not all evaporated from the impure hexabro- mide and will exert a solvent action on the hexabromide later on, thus giving low yields. 6. If a Nelson rotary oil pump is available, it is an excellent plan to remove the last traces of chloroform by attaching the centrifuge tube to this type of pump for 15 minutes. The bulk of the solvent should be removed first by means of the water pump. 7. With either pump the tube should be heated in a bath of 60-65° C., during the evaporation of the last traces of chloro- form. 230 EXAMINATION OF PAINTS, VARNISHES AND COLORS BAILEY’S MODIFICATION OF STEELE AND WASHBURN METHOD Hexabromide Number References: The literature on the determination of hexabromide numbers is not very extensive. The following are the recent references of value: Chem. Tech. and Anal. of Oils, Fats & Waxes, by Lewkowitsch, 5th Ed., Vol. I, p. 568. Farben Zeitung (1912) No. 3 ff. Muggenthaler, Inaug. Dissert. 1912, Augsburg. Bailey and Johnson, J. I. E. C. 10, 999. Principle: The unsaturated fatty acids when treated under proper con- ditions with bromine absorb at each unsaturated linkage two or more atoms of bromine depending on the degree of unsaturation. Thus at a double bond—C=C—there is obtained a saturated bromo product—C—C—and at a triple bond—C=C—four bro- Br Br mine atoms are absorbed to give a saturated compound i a —C—C—. The solubility in ether of the bromo derivaties de- ee Br creases rapidly with increase of bromine content. Thus the di and tetra bromo compounds are easily soluble, whereas the hexa (and octo) compounds are only very sparingly soluble. This fact is made use of to separate the hexa (and octo) bromo de- rivatives in carrying out the analytical determination. Status: The following method is applicable to the determination of the hexabromide number of saponifiable oils. It must be re- membered thatthe hexabromide number depends upon the method employed in making the determination. It is, there- fore, important that in reporting results, the particular method must be specified. Reagents and Apparatus: (a) Reagents: (1) C. P. sodium hydroxide solution of 1.4 sp. gr. (2) 95% alcohol. (3) Distilled water. ANALYSIS OF PAINT OILS 231 (4) C. P. hydrochloric acid. (5) CO, or nitrogen. (6) C. P. bromine containing no non-volatile matter. (7) Glacial acetic acid showing no reduction with dichromate or permanganate in the usual test. (8) Wash ether. Shake ordinary ethyl ether with 10% of its volume of ice- cold distilled water. Separate the water and repeat the wash- ing three times. Dry the washed ether with fused calcium chloride over night. Decant the ether through a folder filter into another flask and add thin slices of sodium. Warm gently on a steam bath under a reflux condenser until the evolution of gas by action of the sodium has practically ceased and bits of freshly cut sodium remain bright in the ether. Distill the ether into a dry bottle and add an excess (at least 3 grams per liter) of finely powdered hexabromide of the fatty acids of linseed oil previously prepared. (If no hexabromide is on hand from previous determinations, it may be prepared as follows: In a centrifuge tube dissolve about five grams of the fatty acids of linseed oil in 25 cubic centimeters of ether. Place the tube in a freezing mixture and add slowly with shaking bromine solu- tion until a red color is permanent. Let stand for at least fifteen minutes and then whirl the tube in a centrifuge until the precipitate has settled and then pour off the ether. Rub up the precipitate with 20 cc. of cold absolute ether, whirl in a centrifuge and pour off the wash ether. Repeat the washing with 3 more 20 cubic centimeter portions of ether. After drying the hexabromide so obtained is ‘pure enough for the preparation of the wash ether.) Shake at intervals for two or three hours or allow the mixture to stand overnight. Then place the bottle in ice water so that the ether solution will be at zero or not above 2° C. for at least three hours. Decant the ether solution rapidly through a folded filter into a dry bottle and keep tighly corked in order to prevent the loss of ether by evaporation. (b) Apparatus: (1) Steam bath. (2) Gas burner. (3) Iron tripod, ring stand and wire gauze. (4) Round bottom flask of 2 liters capacity. (5) Separatory funnel, 500 cc. (6) Bell jar. 232 EXAMINATION OF PAINTS, VARNISHES AND COLORS (7) Well annealed test tubes 5” x 1”. (8) 50 ce. burette. (9) Glass stirring rods 6” x 3/16”. (10) Glass battery jars. ) Graduated cylinders 10 and 50 cc. capacity for weighing out samples. (13) Centrifuge giving about 3,000 R. P. M. (14) A vacuum showing no higher than 40 mm. pres- sure. Determination: (a) Preparation of fatty acids——Weigh approximately 50 grams of oil into a 2 liter round-bottom flask and add 40 cc. of NaOH solution (sp. gr. 1.4—36.50% sol.) and 40 cc. of alco- hol. Place the mixture on a steam bath and insert a 2-hole rub- ber stopper into the neck of the flask carrying a tube which projects into the flask so that its end is just above the liquid. Heat for about one-half hour, passing a stream of CO, through the apparatus all the while. Add one liter of hot distilled water and boil the soap solution to remove the alcohol, either over a free flame or on a steam bath. If a free flame is used about one-half hour’s boiling will be sufficient, but it may be neces- sary to insert capillary tubes to prevent bumping of the liquid. If the solution is heated on the steam bath, usually 2 to 3 hours are required. After removing the alcohol, the solution is cooled somewhat and then acidified with dilute HCl (1:1). Warm the mixture until the fatty acids form a clear layer, continuing to pass CO, through the system all the time. The fatty acids are separated from the aqueous layer by means of a 500 cc. Sep- aratory funnel. The funnel is filled with the mixture, and the fatty acids will float on top, and the aqueous portion is run off. The remainder of the mixture in the flask is added to the fun- nel and the aqueous portion again run off. A brisk stream of CO, is passed into the funnel to replace the air. 300 cc. of hot distilled water is added and the mixture is vigorously shaken. After the fatty acids collect on top the aqueous por- tion is run off. This washing is repeated until the water is neutral to methyl orange, three washings usually being suffi- cient. The warm fatty acids are run into a centrifuge tube (1” x 5”) and whirled for about one minute to collect any re- maining water at the bottom. They are then filtered by de- cantation on to a folded filter under an evacuated bell jar and kept in a well-stoppered bottle. ANALYSIS OF PAINT OILS 233 (0) Preparation of the hexabromides—wWeigh accurately in a weighed contrifuge tube (1” diam. x 5” long) as nearly as possible one gram of fatty acids. It was found that in the case of linseed oil better results are obtained by keeping the weight of the sample as near to one gram as possible, so the deviations from this should not be more than plus or minus 0.02 gram. Dissolve the fatty acids in 25 cc. of the specially prepared ether and place the tube in a freezing mixture kept at about —5° C. made by adding a little HCl to finely cracked ice. Add bromine solution* from a burette at the rate of about one or two drops per second, shaking the tube well during the addition until a deep red color is produced. This should not be done in direct sunlight. The tube is then allowed to stand in an ice chest over- night (about 14 hrs.), the proper precautions being taken to prevent the loss of solvent by evaporation by inserting a stopper. It is necessary to let the tube stand for this period of time be- cause in the case of oils which contain only a small amount of linolenic acid (soya bean oil is a good example) the precipita- tion of the hexabromide proceeds more slowly than in the case of an oil with a larger content of linolenic acid (linseed for example). Next morning cool the tube by immersion in a bath of cracked ice and rub up the precipitate by means of a weighed glass rod, being sure to loosen any material adhering to the side of the tube. Whirl the tube in a centrifuge till the precipitate forms a hard cake on the bottom, cool in the ice bath, and decant the ether. Add 20 cc. of the wash ether previously prepared and cooled to 0° C. and rub up the precipitate with the glass rod. Re- turn the tube to the ice bath and when cold whirl it in the centrifuge. Return the tube to the ice bath and then remove the ether by decantation. Repeat this washing twice more. After the last washing incline the tube and carefully tap it to spread the hexabromide precipitate part of the way up the sides. Warm the tube in water at 60° C. until most of the ether has evaporated, then attach it for 15 minutes to a vacuum line showing a pressure of 30-40 mm. keeping the temperature around 60° C. Wipe the tube dry and allow it to stand in the balance at least 15 minutes before weighing. To the weight of the precipitate in the tube add the weight of the slight amount adhering to the glass rod. This total weight of precipitate mul- *5 ec. bromine, 25 cc. glacial acetic acid made up just before use. 234 EXAMINATION OF PAINTS, VARNISHES AND COLORS tiplied by 100 and divided by the weight of fatty acids taken, gives the hexabromide percentage. Notes: (1) The fatty acids are used instead of the glyceryl esters because the latter give inconcordant results. (2) In the case of linseed oil, the weight of the sample should be kept as near one gram as possible. (3) Care should be exercised in preparing the wash ether for if it is unsaturated with hexabromides according to directions, the results will be low. CO-OPERATIVE WORK ON HEXABROMIDE METHODS AS CONDUCTED BY SUB-COMMITTEE III OF COMMITTEE D-1, A. S. T. M. Comments made by the various observers are abstracted here- with: S. and P. Waldstein state that when a large percent- age of soya bean oil is present in an oil there is formed a large percentage of tetrabromide which may not be completely washed out. They recommend in such in- stances to increase the portions of ether to 25 or 30 cc. or to increase the number of washings to 5 or 6 in order to overcome high results. The chairman of the sub-comneeaee has done some experimental work with the idea of developing a method of determining the hexabromide value of oils volu- metrically. It was found that the bromine absorption number of the fatty acids of linseed oil were higher than for soya bean oil in some preliminary volumetric work. It is known that the bromine substitution num- TABLE XL.—The Results of Various Observers Working on the Two Methods Are Given in the Table Below—Hexabromide Values Steele-Washburn Method Bailey hikes Modifica- tion of Steele- Oil z Washburn ils I Ze acl € 5 : Method 58) 2| 2/28 Blas) g)8)5| 2) Bleg a.0| 2 a | 20! 3 Fed Sa AS M1 a{/aiss On| am | O | E |e Olmi-a 100 per cent Pure Raw Linseed Oil. . .|45.9/46.4/46 .6/45.4/46.0 46.2146, 6/45.4/46.1/40.5/42.7/41.6 85 per cent Pure Raw Linseed Oil... 39.3)... ./41.8/39.1/41.9/39.8/41.9/39_ 1/40, 4/34.9137.5136.2 15 per cent Soya Bean Oil......... : 75 per cent Pure Raw Linseed Oil. . 36 .4|/38.4/38. 2/36 .0/37.2/36. 1/38 .4/36.0137.0/31.5134.5/133.0 25 per cent Soya Bean Oil......... 65 per cent Pure Raw Linseed Oil. . ! 30. 8/33 .4/34.8/30.5)/33.8/33.5/34.8/30.5/32.8/26.7/31.4|29.6 _35 per cent Soya Bean Oil; .* 3.2%.. ANALYSIS OF PAINT OILS 235 ber of linseed oil fatty acids is low while the fatty acids of soya bean oil have a low addition number. Considerable further work, however, will be necessary in order to develop a method that will be satisfactory. TABLE XLI—Jodine and hexabromide numbers of raw and treated linseed oil B PRE WOINDHRON NON OL Iodine H : exabromide No. No. Substance ee Siacla. Method anus By A By 553 | Linseed oil from North American seed..... 176.2 a Boo : Pay ‘ . Se Seas, cole pegs we FR : 553 _ . : " - ine A AME: Ng ad SC ee 46.3 553 : ae : : ee Go 46.5 a een ee bees 46.3 553 “ oe ae + = eran Nairgl2 a Mamie Ata 43.6 553 xe pera 3 s ue Se Suey ight Regs pans a 39.2 oe : i Con : gE aan ce 39.1 565 | Linseed oil, commercial refined............ Le # fs < 563 «“ 4 Petite tan SE a, Bo é s “ Ch od ah RN ee a Re es 43.8 a : i . UES 6a rag ana ser ec aes St Aa 40.5 574 | Linseed oil (Bu. Hieoide. sample). 26: sasses 183.0 nae 574 a Ra ge ee We No iad ace Ga St Pt ieee ed iG a 0. CARED LM co? A7.1 Meee o ) oN ia tant, Raa oe Ie Rig Pees ASR Sep OE eR 46.2 Me 45.7 535 | Lins’d oil Ext’d from Argentine seed....... 189.8 50.0 49 535 = c - ‘ is Cae mates fy NE Dna ie MB (pean MuckoO 535 L es : : Ie aot al tater ig Seetiame nae A eS 50 641 | OL 553 + 5% (1) tung oil Grier sass 6 22. LG GAS il ae bere a 641 are st us : eR ere eter A eed a mT hate Sh rig TDS ey ee Sete er A LG LE Sit ee ae 44 ee “4 643 ee eet 20) Reis) Set eet eh Ca a 1D2c5 we ee: 41 643 erat = Wel aE A ED RR os ARO be 42 644 eerie eo erinding japan. 2......... 164806 es 39 644 pee s s IS Ne eo, SAR RGR Ne h Rrde yar A caRy Tai 39 CN 0 . Bia athe ek cae: AGS OC See ee 42 a ee 41 646 Oo i Beebe 2 ESR! eR To 7a ah eee 40 646 | « « : a bE OP aa aN ae Meat Nima aCe acre ee das 39 588 « « 4+ 10% (1) linoleate drier de RUBE 165.6 ae 588 ~ me i APOE NE PR ter he S. epn ea ree: ; 589 Cet 20%," (1) “ aig! A epee 169.3 45.3 589 ag: 2 NRE A ris ot We ater eee Bee ty AQT 589 aS e * So a Pg OR Saad See 43.6 583 “« « + 0.2% manganese drier* ROR RL: oh 168.6 Bee 583 ak we: . a yd M ames diated Sales ae eons ay : 2 + 0.057% a ; he ee 171.0 a 561 | Linseed oil, commercial...........-..-+-- 173.8 41.8 561 = TLE Fake AR ee aan GS Src a amas ete 359 M «heavy bOCIGd “+ Si ou sabes G iee ak 80.8 11.8 (1) Added without treating oil. (*) Manganese linoleate boiled in at 250° C. 236 EXAMINATION OF PAINTS, VARNISHES AND COLORS Conclusions.—The Steele-Washburn method of determining hexabromides has given closely concordant results in the hands of several different operators, and is apparently well adapted for determining the purity of raw linseed oil. It is recom- mended that further work be carried on with the object of shortening the method. HENRY A. GARDNER, Chairman. Through the kindness of Mr. Herbert S. Bailey and Mr. Baldsiefen of the -Experimental Station, E. I. du Pont de Nemours & Co., there are presented herewith two tables (LI and LII) showing the iodine and hexabromide numbers of raw and treated linseed oils, and of soya bean oil, tung oil, and various mixtures thereof. It is believed that the data presented in these tables will be of great service to the paint chemist who intends to carry on hexabromide work. TABLE XLII—Iodine and hexabroimide numbers of soya bean, tung and lin- seed-soya bean mixtures Ow os Zo = i os Hep sam S ei ele A 3 Ooo OF vs b 8 eae a No. Substance ies Re ea ~ a co By A. | By B. | By B. 310 Soya bean os raw 5.) eee eee 123.2 a 6.5 4.2 310 . OUR SS a a 0 a 6; 1 See 4.9 310 4 Fe hee ee ek at aes De 6.3) 5 ee 3.6 565 Soya bean oil, raw commercial. .... 133.2 1.6 565 . eS * BS ee 5.0 658 i “©” eold pressed. = 3.02.51 4.2 ee 8.41 Peer 658 . rape te pi Oem newer 9.388 | 7.54 659 Soya bean oil, cold. pressed... ... .:.W.o5 joe 5.95 5.35 659 , oo sues Ree OT Og wae aels She al oe 5.76 5.65 670. | Soya bean oil, extracted, 0). .:.2.. 21, Ve 3.9 622 Tung oil. ee ae is ee 2 0.0 0.0 572 £0% OL 563: 50% OL 310. 954 oe 26.0 23.0 572 Re cata meee ey 23.6 572 50% OL.553 + 50% OL 670. 0.1. a 24.3 23.3 572 Fi ane Be eS er 24.6 24.3 CHAPTER XXVI. EXAMINATION OF FLAXSEED* Sample is quartered until 500 grams are obtained. In quar- tering, seed must be poured at center of pile to evenly distribute seed and impurities. All of the dirt which settles to the bottom must be carefully brushed up and added to the pile. Screen the 500 gram sample through 10 mesh until about 50 grams remains on the screen. The residue is hand picked and everything other than linseed is set aside and weighed with the dust. The clean seed obtained at this picking is added to what has passed through the 10 mesh screen. The seed is then passed through a 20-mesh screen, rubbing the seed around in the screen so as to remove any seed attached to it. The under size is collected and weighed after the coarse pickings have been added to it. This constitutes the first dust. The partially cleaned linseed is then reduced to 50 grams in a rifflesampler. This is divided into two 25-gram portions which are hand picked separately and the 1m- purities weighed separately. All linseed portion, whether dried seed or broken seed, is to be put with the linseed. After cor- rected calculation, the total impurities are obtained. The im- purities found in the second picking should agree within 60 milligrams. 7 Oil in Flaxseed.—A 3-gram sample of the clean seed is weighed out and is ground in an agate mortar with an equal part of fine sea-sand which has been washed with hydrochloric acid. The ground sample is placed in a Soxlet thimble and extracted with redistilled ether for three hours. The distillate is placed in a weighing dish and the ether is removed by evaporation. The residue is then dried for one-half hour at 103° C., and the oil is weighed. | Oil in Oil Cake—A 10-gram sample of undried oil cake is placed in a Soxlet thimble and extracted in the same way as described under Oil in Flaxseed. Water in Oil Cake-—Weigh 5 grams of oil cake and place in flask fitted with clean cork. Weigh flask, cork and contents; connect with hydrogen generator, and start flow of hydrogen at the rate of 2 bubbles per second. Place flask in paraffin bath *Contributed by R. L. Hallett. 237 238 EXAMINATION OF PAINTS, VARNISHES AND COLORS at a temperature of 110° C., and heat in current of hydrogen for two hours. Disconnect tubing, and wipe clean of paraffin while hot, with absorbent paper. Cool and draw dry air through flask to remove hydrogen. Disconnect, replace original cork, and weigh. Loss of weight reported as moisture. Protein in Oil Cake.—Protein is found by determining total nitrogen by the Kjeldahl method, calculating it to protein. : ; a 7 3 ’ CHAPTER XXVII. TENTATIVE SPECIFICATIONS FOR RAW TUNG OIL AND METHODS OF TEST A. §. T. M. Raw tung oil shall conform to the following requirements: Maximum. Minimum. CCHICEeTavivy ab LD2De Cong eden 0.943 0.940 15.5° Acid number (Alcohol-Benzol)...........-- aD cat ees ee BOT ALON TUMDECL ioc ccnepectec 195 190 Unsaponifiable matter, per cent..................... DES cake fee ees Pret VAC tIVGnINGES Ate ZO) Conc eee mttaer 1.520 1.5165 Pere DST OW LYS) ae siltstone 163 Belieatine testy MiINUles ee ea, eA ‘ METHODS OF TESTING Solutions Required.—The following reagents will be required: Standard Sodium Thiosulfate Solution.—Dissolve pure sod- ium thiosulfate in distilled water that has been well boiled to free it from carbon dioxide in the proportion so that 24.83 g. erystallized sodium thiosulfate will be present in 1000 cc. of the solution. It is best to let this solution stand for about two weeks before standardizing. Standardize with pure resublimed iodin. (See Treadwell-Hall, Analytical Chemistry, Vol. II, third edition, p. 646.) This solution will be approximately N/10 and it is best to leave it as it is after determining its exact iodine value, rather than to attempt to adjust it to exacly N/10 strength. Preserve in a stock bottle with a guard tube filled with soda lime. Starch Solution.—Stir up 2 to 3 g. of potato starch or 5 g. soluble starch with 100 cc. of 1-per-cent salicylic acid solution, add 300 to 400 cc. boiling water, and boil the mixture until the starch is practically dissolved. Dilute to 1 liter. Potassium Iodide Solution—Dissolve 150 g. of potassium iodide free from iodate in distilled water and dilute to 1000 ce. lodine-Monochloride Solution Dissolve iodine in glacial acetic acid that has a melting point of 14.7 to 15° C. and is free from reducing impurities in the proportion so that 13 g. of iodine will be present in 1000 cc. of the solution. The prepara- tion of the iodine-monochloride solution presents no great diffi- culty, but it shall be done with care and accuracy in order to obtain satisfactory results. There shall be in the solution no 239 240 EXAMINATION OF PAINTS, VARNISHES AND COLORS 5 cc. Sample-=.\.. Cottonseedor : | ; QE Soya Brie ae red Vertical Section. — OPECIFICATIONS — A. Beaker Glass 800 cc. D. Test Tubes; lScm, x 16mm. B. Cover Plate (/ron or Wood.) E. Thermometer,- Small Range. C. Collar Support ( Rubber Stopper No. 6.) FIGURE 98 Tung Oil Heat Test Apparatus (Revised 1920) Note.—Collars C may be omitted and tubes supported in present place by oa wire gauze placed in bottom of oil bath and resting on bottom of beaker. F. Glass Rods, (3mm. with Cork Stoppers ) SPECIFICATIONS FOR TUNG OIL 241 sensible excess either of iodine or more particularly of chlorine, over that required to form the monochloride. This condition is most satisfactorily attained by dissolving in the whole of the acetic acid to be used the requisite quantity of iodine, using a gentle heat to assist the solution, if it is found necessary. Set aside a small portion of this solution, while pure, and pass dry chlorine into the remainder until the halogen content of the whole solution is doubled. Ordinarily it will be found that by passing the chlorine into the main part of the solution until the characteristic color of free iodine has just been discharged, there will be a slight excess of chlorine, which is corrected by the addition of the requisite amount of the unchlorinated portion until all free chlorine has been destroyed. A slight excess of iodine does little or no harm, but excess of chlorine must be avoided. Chloroform.—Should be U. S. P. Standard Sodium Hydroxide Solution—Prepare a stock con- centrated solution of sodium hydroxide by dissolving NaOH in water in the proportion of 200 g. NaOH to 200 cc. water. Allow this solution to cool and settle in a stoppered bottle for several days. Decant the clear liquid from the precipitate of sodium carbonate into another clean bottle. Add clear barium hydrox- ide solution until no further precipitate forms. Again allow to settle until clear. Draw off about 175 cc. and dilute to 10 liters with freshly boiled distilled water. Preserve in a stock bottle provided with a large guard tube filled with soda lime. Determine the exact strength by titrating against pure benzoic acid (C,H.COOH) using phenolphthalein as indicator. (See Bureau of Standards Scientific Paper No. 183.) This solution will be approximately N/4, but do not attempt to adjust it to any exact value. Determine its exact strength and make proper corrections in using it. Alcoholic Sodium Hydroxide Solution.—Dissolve pure NaOH in 95-per-cent ethyl alcohol in the proportion of about 22 g. per 1000 cc. Let stand in a stoppered bottle. Decant the clear liquid into another bottle, and keep well stoppered. This solu- tion should be colorless or only slightly yellow when used; it will keep colorless longer if the alcohol is previously treated with NaOH, (about 80 g. to 1000 cc.), kept at about 50° C. for 15 days, and then distilled. For an alternate method see Jour- nal, American Chemical Society, 1906, p. 395. 242 EXAMINATION OF PAINTS, VARNISHES AND COLORS Half Normal Sulfuric Acid Solution.—Add about 15 cc. H,SO, (sp. gr. 1.84) to distilled water, cool and dilute to 1000 cc. De- termine the exact strength by titrating against freshly standard- ized NaOH or by any other accurate method. Either adjust to exactly N/2 strength or leave as originally made, applying ap- propriate correction. Methods.—The oil shall be tested in accordance with the fol- lowing methods: General.—The laboratory sample shall be thoroughly mixed by shaking, stirring, or pouring from one vessel to another and the samples for the individual tests taken from this thoroughly mixed sample. Specific Gravity.—Use a pyknometer accurately standardized and having a capacity of at least 25 cc., or any other equally accurate method, making the test at 15.5° C., water being 1 at 1D... 2G. Acid Number.—Weigh from 5 to 10 g. of the oil. Transfer to a 300-cc. Erlenmeyer flask. Add 50 cc. of a mixture of equal parts by volume of 95-per-cent ethyl alcohol and ce. p. re- agent benzol. (This mixture should be previously titrated to a very faint pink with dilute alkali solution, using phenolph- thalein as an indicator.) Add phenolphthalein indicator and titrate at once to a faint permanent pink color with the stand- ard sodium hydroxide solution. Calculate the acid number (milligrams KOH per gram of oil). Saponification Number.—Weigh about 2 g. of the oil in a 300-cc. Erlenmeyer flask. Add 25 cc. alcoholic sodium hydroxide solution. Put a condenser loop inside the neck of the flask and heat on the steam bath for one hour. Cool, add phenolphthalein as indicator, and titrate with N/2 H,SO,. Run two blanks with the alcoholic sodium hydroxide solution. These should check within 0.1 cc. N/2 H,SO, From the difference between the number of cubic centimeters of N/2 H,SO, required for the blank and for the determination, calculate the saponification number (milligrams KOH required for 1 g. of the oil). Unsaponifiable Matter—Weigh 8 to 10 g. of the oil. Trans- fer to a 250-cc. long-neck flask. Add 5 cc. of strong solution of sodium hydroxide (equal wieghts of NaOH and H,O), and 50 cc. 95-per-cent ethyl alcohol. Put a condenser loop inside the neck of the flask and boil for two hours. Occasionally agitate the flask to break up the liquid but do not project the liquid onto the SPECIFICATIONS FOR TUNG OIL 243 sides of the flask. At the end of two hours remove the con- denser and allow the liquid to boil down to about 25 cc. Transfer to a 500-cc. glass-stoppered separatory funnel, rins- ing with water. Dilute with water to 250 cc., add 100 cc. redis- tilled ether. Stopper and shake for one minute. Let stand until the two layers separate sharp and clear. Draw all but one or two drops of the aqueous layer into a second 500-cc. separatory funnel and repeat the process, using 60 cc. of ether. After thor- ough separation draw off the aqueous solution into a 400-cc. beaker, then the ether solution into the first separatory funnel, rinsing down with a little water. Return the aqueous solution to the second separatory funnel and shake out again with 60 ec. of ether in a similar manner, finally drawing the aqueous solution into the beaker and rinsing the ether into the first separatory funnel. Shake the combined ether solution with the accumulated water rinsings and let the layers separate sharp and clear. Draw off the water and add it to the main aqueous solution. Shake the ether solution with two portions of water (about 25 cc. each). Add these to the main water solution. Swirl the separatory funnel so as to bring the last drops of water down to the stopcock, and draw off until the ether solu- tion just fills the bore of the stopcock. Wipe out the stem of the separatory funnel with a bit of cotton on a wire. Draw the ether solution (portionwise if necessary) into a 250-cc. flask and distill off. While still hot, drain the flask into a small weighed beaker, rinsing with a little ether. Evaporate this ether, cool and weigh. Refractive Index.—Use a properly standardized Abbé refrac- tometer at 25° C., or any other equally accurate instrument. Iodine Number.—Place a small quantity of the sample in a small weighing burette or beaker. Weigh accurately. Transfer by dropping from 0.16 to 0.19. g. to a 500-cc. bottle having a well-ground glass stopper, or an Erlenmeyer flask having a spe- cially flanged neck for the iodine tests. Reweigh the burette or beaker and determine the amount of sample used. Add 10 ce. of chloroform. Whirl the bottle to dissolve the sample. Add 10 ec. of chloroform to each of two empty bottles like that used for the sample. Add to each bottle 25 cc. of the Wijs solu- NotTE.—The unsaponifiable oil from adulterated drying oils is volatile and will evaporate on long heating. Therefore heat the beaker on a warm plate, occasionally blowing out with a current of dry air. Discontinue heating as soon as the odor of ether is gone. 244 EXAMINATION OF PAINTS, VARNISHES AND COLORS tion and let stand with occasional shaking for 30 minutes in a dark place at a temperature of from 21 to 23° C. Add 10 ce. of the 15-per-cent postassium iodide solution and 100 cc. of water, and titrate with standard sodium thiosulfate using starch as the indicator. The titrations on the two blank tests should agree within 0.1 cc. From the difference between the average of the blank titration and the titration on the samples and the iodine value of the thiosulfate solution, calculate the iodine number of the samples tested. (Iodine number is given in centi- grams of iodine to 1 g. of sample.) * Heating Test.—Test tubes containing the oil should be 15 cm. by 16 mm., with a mark near the bottom to indicate 5 cc., and closed by a cork so perforated that a glass rod 3 mm. in diameter can move freely. Fill an 800-ce. glass beaker (height, 13 cm.; diameter, 10 em.) with cottonseed oil or soya bean oil to a height of 7.5 cm. Place a thermometer so as to be 1.5 cm. from the bottom of the bath. Use a nitrogen-filled, chemical thermometer; engraved stem; total length 4 to 414 in., graduated from 210 to 310° C. in 2° intervals; the length between 210 and 310° C. not less than 214 in. Thermometer glass shall be well annealed. When the bath temperature is 293° C. (560° F.) and very slowly rising at this point, place the tube containing 5 cc. of the oil to be tested and the tube containing 5 cc. of a control sample of known value, so that the bottom of each tube is level with the lowest part of the bulb of the thermometer. If desired, the collars C may be omitted and the tubes allowed to rest upon a piece of wire gauze placed in the bottom of the oil bath so that the tubes will be 1.5 cm. from the bottom of the bath. Note the time. Remove the source of heat for about 45 seconds and then reapply. Before 2 minutes have elapsed the temperature of the bath will have fallen to 282° C. (530° F.), at which point it should be kept as steady as possible. When the samples have been in the bath 9 minutes, raise the glass rods at intervals of 14, minute. Note the time when each sample becomes firmly set. At this period the oil will be so stiff that the entire tube may he lifted by aid of the rod if the collar C is omitted from the ap- paratus. As setting or jellying takes place within a few seconds of fluidity, a good end determination is afforded. Remove the * It is always well to include a test on a sample of tung oil of known iodine value. This may be kept in a dark-colored bottle as a standard. ee a ee ee ey SPECIFICATIONS FOR TUNG OIL 245 specimens. Heat the bath again to 293° C., and repeat the ex- periment with fresh portions of the sample. No stirrer is used in the bath. A screen around the bath en- ables the temperature to be more easily reached. When the bath oil has become tarry and viscid, it should be renewed; otherwise heating may be irregular. Quality Test.*—Into an ordinary agateware casserole, having a bottom diameter of 3 in., weigh 150 g. of the tung oil to be tested, and set the casserole on a wide-flanged tripod having a 3-in. open- ing. The object of the flange is to prevent super-heating of the sides of the casserole. Heat rapidly with a full Bunsen flame, stirring with a thermometer, until the heat reaches 540° F. (282.2° C.) Turn down the flame and hold the heat as near 540° F., (282.2° C.) as possible stirring with the thermometer, until on lifting the latter the oil drops with a pronounced string, showing that polymerization has started. The time required after reach- ing 540° F. (282.2° C.) until the string is noted, is the time of the heat test. For pure tung oils this will not exceed eight min- utes. As soon as the oil strings, remove the lamp and the ther- mometer, and stir with a stiff spatula until the oil is solid. After stringing, a pure tung oil will require not over 40 seconds more to become solid. When solid, allow to stand just one minute, then turn out, upside down, on clean paper and cut with a clean spatula. Pure tung oil gives, a gel that is dry, not adhering to the spatula when cut, that is firm, crumbling under pressure of the spatula without sticking, and the cut portions should crumble under pressure like dry bread crumbs. Adulterated tung oil gives a gel that is soft, sticky, and which will not crumble. It has been found that the optical dispersion of tung oil is ex- tremely high as compared to that of many other oils. Based on this, Holley has worked out a method to determine the purity of tung oil (Holley, Analysis of Paint Vehicles, 1920, p. 81). This method, however, is not commonly in use because of the expense and difficulty of obtaining the type of apparatus used for the pur- pose. It is believed, nevertheless, that optical dispersion methods are of great value for the examination of tung oil and that they should be used when the apparatus and instruments are avail- able, as additional or confirmatory tests. As a rule, determina- tion of specific gravity, refractive index, and quality tests, as outlined above, afford sufficient information to judge the purity and value of tung oil. * Furnished by R. S. Worstall. CHAPTER XXVIII. ANALYSIS OF VARNISH The testing of oleo-resinous varnish should largely be of a physical nature. Such properties as odor, consistency, clarity, flowing, time of drying, character of finish, hardness, resistance to moisture and abrasion, elasticity, etc., point out the real value of a varnish. Chemical tests that give additional information, sometimes of a valuable nature, are as follows: Flash point, acid number, ash, character of solvent, fixed oil and resins. Flash Point.—A nickel or iron crucible of 60 mm. diameter and 40 mm. height is filled with the varnish to within 20 mm. of the top. It is then supported in a water bath in such a man- ner as to be about two-thirds immersed in the water. The water should, be from 15° to 20° C. at the start and should be heated slowly so that the temperature of the varnish as indicated by a thermometer suspended in it, will show a rise of about 1 de- gree per minute. Test for flash at each half degree, using a very small flame. (See also A. S. T. M. use of Tag closed tester. ) Acid Number.—Ten to 20 grams of the varnish are weighed into a small Elenmeyer flask, 50 ce. neutral alcohol added, and a small funnel inserted in the neck. Heat on the water bath for one-half hour, with occasional shaking. Allow to cool some- what, add two drops of phenolphthalein indicator and titrate with tenth-normal potassium hydroxide solution. The acid number is the number of milligrams of KOH required to neutralize each gram of the varnish. Use of a mixture of equal volumes of alcohol and benzol 90° gives the true acid number of a varnish including colloidal acidity that would not be indi- cated by alcohol alone. Ash.—Weigh in a porcelain or fused silica crucible several grams of the varnish. Burn off over a small Bunsen flame, using great caution to avoid boiling over and spattering. When all combustible matter is destroyed, weigh the ash and if desired analyze it. Solvent—Steam distillation of a portion of the varnish will remove the solvents, leaving a residue of fixed oils and varnish _ resins, which may be weighed after driving off the water. The distillate should be examined as recommended under Turpentine 246 ANALYSIS OF VARNISH 247 FIGURE 99 Apparatus for determining gas re- sistance of varnish. See Interdepart- mental Specifications, back of volume. FIGURE 100 Apparatus for determining draft resistance of varnish. See Inter- departmental Specifications, back of volume. 248 EXAMINATION OF PAINTS, VARNISHES AND COLORS Specifications. The amount of mineral spirits and turpentine may thus be determined. It is customary to conduct the steam distillation upon 50 grams of varnish in a 500-cc. Erlenmeyer flask placed in an oil bath maintained at about 130° F. The distillate may be col- lected in a separatory funnel. The water may then be drawn off and the distillate examined. A much more rapid and fully as accurate a method for de- termining the percentage of volatile is as follows. This method, however, does not yield the actual volatile for subsequent ex- amination. Percentage of Volatile-—Place a portion of the sample in a stoppered bottle. Weigh the container and sample. Transfer about 1.5 grams of the sample to a flat bottom metal dish about 8 cm. in diameter (a friction top can plug). Weigh the bottle again and by difference calculate the exact weight of the portion of the sample transferred to the metal dish. Heat the dish and contents in an oven maintained at 105° to 110° C. for 3 hours. Cool and weigh. From the weight of the residue left in the dish and the weight of the sample taken, calculate the percent- age of non-volatile residue. Fixed Oils and Resins.—In the above determination, the total amount of fixed oils and resins is obtained. It is a difficult matter, however, to determine the exact percentage and char- acter of resins that. have been used in the manufacture of the varnish. This is due to the fact that during the process of heating oils in the presence of resins many intricate chemical changes are brought about, a considerable portion of the resins being distilled off in the form of vapors and combinations of the oil brought about that are difficult of separation. One of the best methods, however, of separating the fixed oils and varnish resins is carried out in the following manner: A portion of about a half ounce of the varnish resin should be placed in a 3800-cc. tared beaker. There should then be added about 200 cc. of ice-cold petroleum ether. After stirring the beaker should be covered and allowed to stand, preferably in a dish containing ice. In an hour’s time the resinous ingredients will be found precipitated at the bottom of the beaker or adher- ing to the side thereof (with the exception of rosin, which is largely soluble in petroleum ether). The precipitated resins should be washed with fresh portions of cold petroleum ether ah tend Nt |i i ba ANALYSIS OF VARNISH 249 two or three times, pouring the decanted portions into a large bottle. The combined portions of petroleum ether may then be filtered through a tared filter, adding by the aid of a stirring rod the resins contained in the beaker. The filter paper and the beaker with the resins may then be dried at 100° C. and weighed. The combined filtrates may be distilled to obtain the fixed oil as a residue, which may be examined for constants. (This fixed oil may contain rosin.) The amount of rosin contained in a varnish may be roughly ascertained by thoroughly shaking in a separatory funnel a portion of the varnish with a large quantity of absolute alcohol. The rosin may be obtained by evaporation of the alcoholic extracts. The fixed oils after oxidation or poly- merization, as caused by the heating of the varnish during manufacture, are not readily soluble in alcohol. Separation of Polymerized Oils and Resins.—In the making of varnish, most oils become oxidized or polymerized to a condi- tion resembling resins. For instance, when a varnish is ex- amined for resins by the above method, it will often be found that a considerable amount of matter insoluble in petroleum ether will be obtained even when hard resins are absent. The insoluble substance is oxidized or polymerized oil. It may be differentiated from varnish resins by the fact that it may be saponified by alcoholic potash. This method, as used by the regulatory division of the State of North Dakota, is the original method published by E. W. Boughton of the Bureau of Standards (see U. 8S. Bureau of Standards Technologic Bulletin 65), as modified in North Da- kota. Although it involves a tremendous amount of work, it is probably the most accurate method for the separation of polym- erized oils and resins. The method follows Boughton’s original scheme very closely. The use, however, of ice-cold ether and ice- cold water is probably an advantage in that the ether separa- tions are quicker and sharper. In Boughton’s original method, the material extracted by ether from the first saponification mixture of acids and fatty acid soaps is termed unsaponifiable matter. In the North Dakota revision, the proposal is made to add this same ether extract to the resin portion. This consti- tutes a somewhat radical difference between the two schemes and clearly brings out the fact that neither Boughton’s method nor the North Dakota method can be relied upon to give the true oil content of present-day varnishes. For instance, at 250 EXAMINATION OF PAINTS, VARNISHES AND COLORS least one of the varnishes on the market today contains wool fat (degras). In Boughton’s method this product would show up as unsaponifiable matter, while in the North Dakota method the unsaponifiable part of the wool fat would be included in the resins. This same difference would be true of a varnish con- taining paraffin. On the other hand, a varnish made of tung oil and cumarin resin would show a high unsaponifiable and resin content by Boughton’s method, while the North Dakota method would indicate the cumarin as resin. In view of the above, it is quite apparent that neither one of these methods should be included as a part of any routine method of analysis of a varnish but should be merely classed as “stunt” tests for a research laboratory, where an insight into the ingredients of a varnish is desired. All of which brings out the absolute futility of a varnish analysis as a basis of evaluation. Physical tests afford the only reliable data in judg- ing the properties of an oleo-resinous varnish. Method.—Weigh by difference from 4 to 6 grams of the varnish into a 125-cc. Erlenmeyer flask, add 25 ec. of water and boil gently until not over 5 cc. of water is left. This is best performed by placing the flask in an oil bath, and by passing a stream of carbon dioxide through the mixture during the evap- oration. Then add 25 cc. each of half normal alcoholic potash and benzol, and reflux for one hour. Evaporate the solution down to about 10 ce. and transfer to a 500-cce. globe-shaped separatory funnel, rinsing the flask well with water, alcohol and ether. Add 100 cc. each of water and ethyl ether and shake well, using a moderate circular motion. In this and all similar operations use ice-cold ether and ice- cold water. The shaking should be repeated three times. Should an emulsion form and not break within five minutes, add 2 ec. of alcohol. Draw off the aqueous layer into another separatory funnel and wash the ether layer twice with cold water. Add the wash- ings to the aqueous layer and transfer the ether layer to a weighed Erlenmeyer flask labeled “Gums.” Acidify the aqueous layer and completely extract with ether. Transfer the ether solution to the Erlenmeyer flask into which the varnish was weighed and distill off the solvent, using a vertical condenser. Then add 10 cc. absolute alcohol and evaporate on a steam bath. This is to remove the water present. Distill off the solvent in : ) ; 4 | : ; ; ; F a ee ee a gare OT We ANALYSIS OF VARNISH 251 the “Gums” flask whenever the flask becomes half-full. All ether solutions of unsaponifiable matters and the resins acids that are separated out from subsequent extractions are trans- ferred to this flask. To the residue extracted from the acid solution add 20 cc. of absolute alcohol and 20 cc. of a mixture of 4 parts of absolute alcohol and 1 part of concentrated sulphuric acid. Reflux for five minutes, transfer to a separatory funnel, rinsing the flask with water and ether, and add 100 cc. of ether. Shake well, add 100 ce. of a 10-per-cent solution of sodium chloride, and shake several times. Draw off the aqueous layer and extract with 50 cc. of ether. Wash the combined ether layer and dis- card the aqueous layers. To the ether layer add 50 cc. fifth nor- mal aqueous potassium hydroxide and 10 cc. of alcohol and shake well, using a moderate circular motion. Repeat the shaking as soon as the layers have separated. Separate the layers and wash the ether layer with 50 cc. of water containing 5 cc. of the aqueous potassium hydroxide and 5 cc. of alcohol. Combine the aqueous layers and extract with ether keeping all insoluble soaps with the ether layer. Then combine the ether layers, transfer to an Erlenmeyer flask, and distill off the sol- vent. Take the aqueous layers, acidify with hydrochloric acid and extract completely with ether. Transfer this ether solu- tion to the “Gums” flask. Take the residue and reflux with 25 cc. of alcoholic potash for one hour. Evaporate on steam bath until only 10 cc. re- mains. Cool, transfer to a separatory funnel with the aid of 50 ec. each water and ether and shake. Use the same moderate circular motion. Repeat the shaking twice and draw off the aqueous layer. Extract the aqueous layer with ether again. Combine the ether layers and wash twice with 600 cc. portions of water. Transfer the ether lavers to the “Gums” flask. Take the aqueous layer and the washings from the ether layer, acidify with hydrochloric acid and extract completely with ether. Trans- fer these ether extracts to a weighed Erlenmeyer flask, distil] off the solvent and heat on a steam bath with small portions of absolute alcohol until all of the water is removed. Then heat to constant weight at 105° C., in an oven filled with carbon dioxide. Weigh as fatty acids. Take the “Gums” flask, distill off the solvent, remove the water, dry and weigh as in the case of the fatty acids. This weight is reported as resins or as varnish gums. 252 EXAMINATION OF PAINTS, VARNISHES AND COLORS Calculations: (a) Wt. of ‘Resins. X: 1.07 < 100—per cent total of resins Wt. of sample (direct). Wt. of fatty acids i rsa le x 100—per cent of total oils. (b) (c) (Per cent of non-volatile—per cent of ash) =per cent of total resins (by difference). A method of examining the fatty acids separated from the resins in a varnish, as described by de Waele* and by Wolff,; is referred to on page 329 of the very valuable book entitled “Var- nishes and Their Components,” by R. S. Morrell (Oxford Tech- nical Publications). The reader is referred to the original papers for a detailed study of the methods. It is believed that while occasion may arise for work of this character, as a rule much more information regarding the suitability of a varnish for a certain purpose can be obtained by practical physical tests, as referred to in other sections of this volume. EXAMINATION OF SPIRIT VARNISHES Distillation of 100 cc. may be made when it is important to de- termine the type of solvents used. The distillate can be frac- tioned and tested for alcohol benzol, or similar light solvents gen- erally employed in such varnishes. Mineral spirits and turpen- tine are to be looked for when spirit varnishes of the dammar type are believed present. The solvents used in shellac varnish and shellac varnish substitutes Manilla Rosin, etc., are generally of the alcohol soluble type. For a determination of the amount of solvent present in a spirit varnish, a quantity can be weighed out in a friction top tin cover, evaporated in an oven, and the residue weighed as de- scribed elsewhere in this volume for the determination of the amount volatile matter in varnishes. The residue left from the evaporation may be examined to secure some information re- garding the type of resin used. Determination of the solubility of the residue in various solvents, determination of the acid *de Waele, Journ. Oil Col. Chem. Assoc., 1920, 8°75: tH. Wolff, Chem. Age, 1921, 15, 2989. ANALYSIS OF VARNISH 253 value, and similar characteristics, as outlined under the chapter for the examination of resin, may afford considerable informa- tion. Morrell, in commenting upon a scheme for the detection and separation of common resins, as published by H. Rebs in “Die Spirituslackfabrikation” (1905), makes the following statement: Concentrated acetic acid will dissolve lac, rosin, an oleoresin of turpentine and accroides resin. Very dilute ammonium chloride will dissolve lac, while manila, sandarach, rosin, and accroides are insoluble. Benzine (light petroleum) will dissolve rosin or an oleoresin, but manila, sandarach, lac, and accroides are insoluble in that solvent. In order to separate the different resins qualitatively and quantitatively in a spirit varnish, the solvent is distilled off, the residue is finely powdered and warmed on the water bath with the solvents mentioned above. If lac and rosin be present, the lac will dissolve in very dilute ammonium chloride. Lac may be sepa- rated from manila or sandarach, and likewise from rosin, but the separation of sandarach from manila copal is very doubtful. The estimation of dammar ad- mixed with spirit copal or kauri by means of alcohol and chloroform has been put forward by Stewart.* The resin is boiled with alcohol, which dissolves the spirit copal and part of the dammar. The residue is ex- tracted with chloroform in a Soxhlet, whereby the re- mainder of the dammar is dissolved. The amount of the chloroform-soluble extract is a measure of the per- centage of dammar. The insolubility of a genuine sam- ple of the particular variety of dammar must be known. It is evident that the methods of separation of the in- dividual resins in a mixture are by no means satisfac- tory, and there is need for much investigation in that field.t At present the works tests are essentially the most reliable. Elasticity, lustre, hardness, uniformity of film, and, in the case of coloured spirit varnishes, stability to heat and light, are compared against special requirements. On metals the varnish film must be clean and the coating must not have an acidity likely to set up chemical interaction with the metals. Determi- nation of acidity, behaviour on drying, flow, colour, and specific gravity are compared with corresponding values of the standard sample. If the spirit varnish contain nitrocellulose celluloid, or cellulose acetate, the residue after the removal of the * S. Stewart, Journ. Soc. Chem. Ind., 1909, 28, 348. + Dietrich, Analysis of Resins, 2nd Ed. 254 EXAMINATION OF PAINTS, VARNISHES AND COLORS solvents must be examined by special tests. Treatment with a dilute solution of diphenylamine in concentrated sulphuric acid will give a blue coloration in the presence of nitrocellulose. Nitrocellulose may be estimated in the residue by measuring the volume of nitric oxide evolved by the action of ferrous chloride and hydrochloric acid at 100° C., whereby the nitro-group of the nitrocellulose is reduced to nitric oxide. Celluloid may be detected by the identification of the incorporated camphor, which can be removed by ether or by methyl] alcohol, in which the nitrocellulose is in- soluble. For the detection of cellulose acetate, gentle heating ‘with concentrated sulphuric acid and a little alcohol will give amyl acetate. | For the identification of the cellulose component the original residue may be boiled with hydrochloric acid (s. g. 1.10), neutralised, and tested for the sugars with Fehling’s solution. The cellulose in nitrocellulose and celluloid can likewise be detected by the production of reducing sugars on hydrolysis. ae oe wh Ce Le ee a ee Se ee ae ee ee ee ee Pe EL Oe ee ee ee eT ee a ee Ee ee a ee eee ae a ee TS ee ee CHAPTER XXIX. ANALYSIS OF MIXED DRIERS While composed mainly of organic material, mixed driers may contain silicon, iron, aluminum, calcium, magnesium, phos- phorus, copper, zinc, lead, manganese and cobalt. Some of these are present in linseed oil, oils and resins, some may be accident- ‘ally introduced (as from kettles) and some are purposely added. Although the last three only are usually determined, the possible interference of the others must be considered in any scheme of analysis. When an accurate determination of the percentage of various metallic driers in oils and varnishes is desired, it is customary to slowly ignite the mass and examine the ash. Wet oxidation, of such large amounts of sample as are necessary, with nitric and sulphuric acids is impracticable and rapid ignition at high tem- peratures will result in the volatilization of some or all of ele- ments such as lead and zinc. The ash is usually extracted with nitric acid, on account of the presence of lead. It is to be borne in mind that direct de- termination of lead as sulphate is not permissible in the pres- ence of calcium, that the bismuthate method for manganese can not be used in the presence of cobalt, and that most methods for the determination of cobalt require the elimination of several of the above constituents. RECOMMENDED PROCEDURE* (For lead, manganese and cobalt) Ash 50-200 g. of the drier in a muffle at the lowest possible temperature. Dissolve the ash in dilute nitric acid (1:1), add- ing hydrogen peroxide to facilitate solution in case peroxides are present. Filter and dilute to measured volume. Determine manganese in an aliquot of the above solution by the persulphate-arsenite method if cobalt is present and by either this method or the bismuthate method in the absence of cobalt. (A.S. T. M. Standards, 1921, pages 514-16.) Determine lead in another aliquot by first precipitating with hydrogen sulphide in a solution of suitable acidity, dissolving * Suggested by P. H. Walker. 256 256 EXAMINATION OF PAINTS, VARNISHES AND COLORS the precipitate in hydrochloric acid with the aid of a little nitric acid toward the end, if necessary, and then finally precipitating the lead as sulphate or as chromate by the usual procedures. Determine cobalt in another aliquot by first evaporating with sulphuric acid to eliminate lead, then carrying on a double pre- cipitate with ammonia to eliminate iron and aluminum, and finally adding potassium nitrite to the combined ammoniacal filtrates after acidification with acetic acid. In case the amount of cobalt is very small, a preliminary concentration should be carried out by treating the ammoniacal filtrates with ammonium sulphide, filtering, dissolving the sulphides, making the solution alkaline and then proceeding with the acidification and addition of nitrite. ; If a determination of zinc is desired, it may be carried out in the filtrate from the hydrogen sulphide separation of lead. In this case, the filtrate should be treated with sulphuric acid and evaporated until sulphuric acid is evolved. The cooled solution should then be diluted, neutralized until it contains approxi- mately one hundredth normal sulphuric acid and zine pre- cipitated in the sulphide which can then be ignited and weighed as oxide or sulphate. For determining the efficiency of a drier, see methods outlined under Interdepartmental Specifications for Drier, back of this volume. Quick Test for Driers in Varnishes and Pigmented Enamels.— A quick test communicated to the writer by C. L. Schumann,* for determining such constituents, is as follows: Weigh 50 grams of varnish into a 500 cc. Erlenmeyer flask, add 60 cc. of denatured alcohol, 60 cc. concentracted hydrochloric acid, aud a few glass beads. Heat on a hot plate until most of - the alcohol is boiled off. Add about 12 oz. of water and heat to — boiling, subsequently filling up to the neck of the flask with tur- pentine substitute. Heat and let stand until a clear separation is noted. Siphon off the turpentine substitute and add another portion thereof. Repeat process. Evaporate the water solution to a sufficient concentration for determining metals present. This water solution will contain all the metal portion of the varnish. The same method as above may be used with enamels, but only 2 to 3 grams is required. : Morrell+ gives certain qualitative tests for lead, manganese, — * Pratt and Lambert Laboratories. + Robert S. Morrell, Varnishes and Their Components. Oxford Technical Publications. ANALYSIS OF MIXED DRIERS 257 and cobalt driers in varnish, that are referred to herewith. For detecting the presence of lead, the varnish or drier is diluted with about an equal quantity of light petroleum ether. A dilute solu- tion of potassium bichromate is added, and the mixture shaken thoroughly. If lead is present, there will be no sharp line of division between the water and the diluted varnish, owing to the formation of a precipitate of lead chromate at the dividing sur- face, and also on the walls of the test tube. The contents are poured out of the tube and the walls carefully examined for the presence of yellow lead chromate adhering to the sides. The ad- dition of some ammonium sulphide, which will turn the chromate to a dark color, is confirmatory. This test works in the presence of manganese and cobalt. For the presence of manganese, 2 or 3 cc. of the varnish are thinned with from 8 to 4 cc. of petroleum ether and shaken for about 8 minutes with moderately dilute nitric acid. The aqueous layer is withdrawn and boiled with a pinch of manganese-free lead peroxide. On settling, a violet color indicates the presence of manganese. This test can be performed directly in the pres- ence of lead and cobalt. For the presence of cobalt, the varnish is diluted with light petroleum ether, and then shaken with dilute hydorchloric acid. The water layer is separated, and to it there is added an excess of ammonium sulpho cyanate with a little concentrated potas- sium acetate and 2 or 8 drops of saturated tartaric acid (to re- move ferric sulpho cyanate), a blue coloration indicating cobalt. If rosin is present, the procedure is slightly modified. 114 ce. of the thinned varnish is shaken with 14 cc. of ammonium sulpho _ cyanate solution; 14 cc. amyl alcohol, and from 8 to 4 cc. of ether ‘are added. This mixture is shaken. As a red color might indi- ‘ cate a trace of iron, 1 cc. of ammonium acetate solution and 2 or r 3 drops of saturated solution of tartaric acid are added, whereby the varnish-ether-amyl alcohol layer becomes green. The addi- tion of 1 cc. of acetone causes a cobalt blue color to appear in the aqueous layer. The presence of lead and manganese does not in- terfere. CHAPTER XXX. EXAMINATION AND ANALYSIS OF VARNISH RESINS* The value of a resin for varnish purposes depends largely upon its physical properties, such as color, hardness, and fusibil- ity. In certain cases chemical tests such as acid number and acetyl value, yield important information. Knowledge of the chemistry of the varnish resins, however, is far from complete and their composition, except in two or three cases, is not definitely known. Consequently there is much confusion in the literature regarding the proper method of procedure for de- termining the chemical constants. The purchase of resins on chemical constants such as iodine, saponification, and acid values together with ash, color, and size of lumps may not be far dis- tant. Such procedure would at least eliminate many fanciful “gradings” now existing and which have but little meaning. All resins used in varnish making may, for analysis at least, be conveniently divided into two classes: (1) Fossil Resins (“Copals” or “Varnish Gums”). These are in general very hard and difficultly soluble. They must be melted and held at a rather high temperature until a certain portion is driven off and they become soluble in oil. (2) Spirit soluble resins such as rosin, sandarac, mastic, damar, etc. These two groups interlap to a certain extent. For instance, Manila which is soluble in alcohol, must be “cracked” at a rather high temperature when used in oil varnishes and for the latter purpose might be considered as a fossil resin. PHYSICAL CHARACTERISTICS OF FOSSIL RESINS Hardness.;—The term hardness is purely relative, no definite method for determining it having yet been devised.t Moreover, * Arranged by the writer and P. C. Holdt, from Scientific Section, Cir- cular No. 159. ; y+ One of the writers has found valuable for determining the relative hardness of resins that may be dissolved in volatile solvents and then evaporated to form films, an instrument that will be described in a Scientific Section Circular to be printed late in February, 1925. ¢ An ingenious method has been described by P. Nicolardot and Ch. Coffignier, Chimie et Industrie 5150-156-1921. In their apparatus a defi- nite weight is applied to a small ball which rests on a piece of the resin. The relative hardness of a series of resins is inversely proportional to the diameter of the indentation observed when the weight is removed. 258 tia of Sk 259 ANALYSIS OF VARNISH RESINS ‘19[}}0g 0} ONp St 91GB, SITYL, “UOTINOS 9Y} JO Y}HU0I}8 OY} 07 Jojar oyvIpAY [BIOTYO JapuN sjyoyousq UI soinSy ou, "SOATOSSIP 91991] [2 ‘d 06 ¥ 08] “aTqnyos “ayqnyos “atqnyos B ‘SESIUTZBTEF) | ‘e[qnjos ATysoy |-eTqnjos Ayeayua eTqnjos ApSoyy a[qnyosuy Ajeyotduiog, | Ayaatyue 4ysoupy Ajeyetaures yo oo ere AE % = ‘aiqnjos. | [0 -d06 9 os] ‘paayossip sid 1d “aTqnyos ‘ajqnjos | se ‘aTqnyjos AjWysI{S ‘sestulyeax) | Afeityua ysowpy | efqnjos Ajywed | ‘9 ‘d OT ynoqy | -njos Ajeyo[dur10*D Ajeqe[durog ATO Vo] CULO Gyn enme ween LIN BY ae per = * aby “oNpIsed SNOUT}B = i: = ‘pa alOssIp -[es 8 YJIM ynq *PpaAlOSsrIp ‘eTqn SORA OOS TS IST BLS OOF eal 0a She OMUL Ie sa aiel ia. ahaa Ot || lee ceca) ewiev ie (oie, si oie! Pie) (wdupiitarn! a1 eteG tcteate an aiemialna! tally is ener 9) ‘d OL ynoqgy ‘paAfOssip ATASOTT 4) ‘d og 4qnoqy -[OSUI {SOUL Vy se eee *SoIpuy 4SOM a S Fe ‘Lo -d og] oe: *eTqnyjos ‘aTqnyos * ‘aiqnjos ‘aTqnyos a. SS Se, OL Se ee ee) eatie (a \ayeeXte, 0 Tes) :@ Je) of w_\8y lee: ils Ome) at it liek Te eG Met (eee cater bie bate 98[qnyjos Ajoleg Ajei14yue JSOWI[V Ajeqo[dut0* Ajeze[d W107 Ajeye[durog ey tay est Se exe) ee, *[IzBig te Rae po 4 ‘u01}Se3d ‘3 ‘onpIisel snouns - 23) -Ip suo[ 109;8 “paATOssip -[os & YYIM Ing *PpeATOSsip ‘arqn ‘a[qnyos Ajyieg | ‘epqnjos Ajareg | Apysour = aqnjog [* ste ‘0 ‘d OL ynNogy | peajossip AYsoyy | *o -d OT ynoqy S[OSUTE SOUL Vans weenie IVQIZUBT i ; : *“PpaAlOSsIp A ~ -Butajosstp yno *paAalOssip es *poajos x 2 a a A acl MeN LU LE et ce ON Dak CMe ee UCR CUR OC a aN AS TD cma Tore Oleg oe, Coce Dr ma. Bhs coach. ren a) ‘d GS ynoqy -YJIM SNOUTyvIE*) 9) ‘d OL 4qnoqy -stIp ApQieg Se sisal 8! Suelia uooloWIed aa a = f. e “oNprIsed SNoulys S Bre : *paAlOssip ‘atqn -[es 8 JIM 9ng *paalossip *paajos CHRONOS 0 eC ote | ‘aTqnyos Apeieg "9 ‘d oc qnoqy Lee |e tee Hota ese ete) wey) ie -[OsuI JSOUL[Y ‘PpeAfOssip ATISOT ‘9 ‘d og 4ynoqy -SIp ApJIB gq Se ‘ou0e'T BIIBIG ae at ie ? a “onptisel snoulye s ee *8]qnjos [0 ‘d Og] -[es B YIM ynq *paAlossip *poaros ae eee atc Me PRS Ajaitjyue JSOWITY ‘aTqnyos ApVYSI[S e[qnjos Ajareg ‘oTqnyposuy | ‘peajosstp ATysoyy | “0 ‘d QT ynoqy | -stp API A asmor 5 *SULA[OS Si ‘oNnptIsed Snoulye . . ie “SIP JnoyyIM ‘['o -d ¢-Z OT] -[es & VIM 4nqG “PeATOssIp ‘eTqn ‘oTqnyos AT\soyy SNOUI}BIE) ‘aTqnyos Apavg a[qnjos Ajeivg ‘eTqnyjosuy | “peajossip AyysoyT | *o -d QZ ynoqy | -josur ysowlpy |* *Bpnsueg MoT[aX oer i “oNnpIsel Snoulye ‘Ta dct] -[es @ YJIM 9ngG *peAlOssIp ‘Ppa AlOssip ‘aqqnjog | ‘atqnjos Ajereg “aTqnjos ATV 9TqQnjos Ajoreg “oTqnyjosuy | “peajossip Ayysoyy | ‘0 ‘d GT ynoqy | ‘0 ‘d OT ynoqy |: ° - vjnsueg OFM ‘gurajos. | é J ‘anpiser snourye 4 “SIp ynoyyiM “pinbyy [2 “d 08] “Jos 8 YIM yng “pealossip “pealossip he tree he SNOUT}BIAY) | plqin} 0} sfqnjog | s[qnjosur ysourTy ‘9TqANyosu] | ‘peayossip AT\sop | “9 ‘d gT ynoqy | ‘o ‘d oT ynoqy |°-°***-vjosuy poy e fled “anptser Snoulye “pinbiy prq ‘arqnyjos “pinbiy -[93 B Y}LM 4nq "pearossip “peaTossip -In} 0} 9IqQn[Og | Ajeilyue ysowm[y | prqiny 07 Ol UNIO OP uate ea kre ‘etqnjosuy | “‘peapossip Apysoyy | “0 ‘d OT ynoqy | ‘a ‘d eg ynoqy |°-:*: BIOSUY 23 AA IFPOVz*0D syed joyoo|e Aq uOI}N[OS splIo[yoR1494 9Uu040y ulIpAYIOTYOIp 9U0}0V © [enba jo asinjzxIJy | PpaMoOT[o} 19q3q oyeIpAy [Bs0[YD uoqieg ooutdiay, [440-[Aqq0TN -eyd{Ty sjedoy IIL1IX Fav 260 EXAMINATION OF PAINTS, VARNISHES AND COLORS the value of the resin depends not so much upon its initial hard- ness as upon the degree of hardness which it imparts to the fin- ished varnish. A resin of greatest initial hardness, however, usually produces the hardest varnish. The general scale of hardness of the principal types of copal, according to E. J. Parry,t is as follows: 1. Zanzibar 6. Sierra Leone (fossil) 11. Manila 2. Mozambique 7. Yellow Benguela 12. White Myola 3. Lindi 8. White Benguela 13. Kauri 4. Benguela 9. Camaroon 14. Sierra Leone 5. Pebble 10. Congo (living trees) 15. South American This table agrees fairly well with that of other investigators. TABLE XLIV—Table Showing Percentage of Resins Dissolved by Various Solvents. By Coffignier sd Carbon Ethyl Amyl Spirits of * Alcohol Ether Alcohol | Turpentine ee FRDZADAT Sk oo ats eee a 14.10 | 25.00 | 36.70 | Insoluble Insoluble Madagastar a; 2 iN tia 26.20 | 35.00 77.60. 39.70 15.00 Demersiar see tee 27.90 | 44.60 | 47.00 7.50 24.50 CONROE oe te ee 74.70) 51.70 45-97 au 31.80 30.90 pierrs: Leone’. ak ye an 31.10 | 52,20 |} 9620 28 .60 29.10 Brazile pe ae ae 69.80 | 70.30 | 98.20 51.80 55.10 Beriguelenik aenzeks tae 83.50 | 56.30 | 99.10 31.20 26.00 lors) ete 2, Be EN BER os Mn Ora 42.60 | 57.40 | 91.50 20.40 30.10 Kameritigs st ase ehekas 33.30 | 44.20 | 70.80 21.40 26 .30 ACDYE. «80th se Ep en et 52.20 | 56.00). 95,90 20.30 19.70 Kaui; blond) 52 93.40 | 38.20 | Soluble 22.50 18.90 Kaiti: srowiie ave oe ess 64.20 | 39.30 | Soluble 26.40 22.70 Kaur. bushi sae es 87.70 | 52.70 | Soluble 27.10 28.10 Manila, hard, 28. ct. thon 44.10 | 41.50 | Soluble 26.80 31.00 Manild, triable.) >. Sa Soluble | 71.30 | Soluble 35.90 38 .00 Pontianads oa.5 ce ee Soluble | 54.00 | Soluble 33.60 38 .09 Bilne Angolnaarc, sence ak 84.90 | 72.70 | 98.60 30.60 38.70 RedhAngolic ssi aieaies 62.40 | 48.70 | 93.00 23 .00 22.30 Colom bis ac7tg4.p sae ee 83.00 | 50.00 | 95.10 31,30 30.40 According to Bottler, resins may be tested for hardness by seratching with rock salt. All are scratched; the hardest only with much difficulty. He classifies them in order of decreasing hardness: 1. Zanzibar 5. Congo 2. Red Angola 6. Manila 3. Sierra Leone 7. White Angola 4. Benguela 8. Kauri {Gums and Resins, E. J. Parry, Pitman & Sons, London. ere rors Te ee et, Re ee ee ANALYSIS OF VARNISH RESINS 261 Solubility.—The solubility of the various resins in different organic solvents has been thoroughly studied and numerous at- tempts made to develop a system of classification based on this property. The solubility of a particular resin varies with its age, handling after collection, etc. The hardest and best va- rieties are in general the most difficultly soluble. Table XLITI, XLIV and XLV are taken from K. Dieterich’s “Analysis of Resins.” Fusibility.—None of the resins have sharply defined melting points. The fusing is a continuous process and may extend over a considerable range of temperature, as indicated in the table below. The harder resins require higher temperatures to melt them, and always undergo partial decomposition during the melting process. Different samples of the same kind of resin often differ considerably in this respect, hence the melting point is of little value in identifying a resin. TABLE XLV—Due to Coffignier Specific Softening | Melting Gravity Point Point HERI OE ost pos kd 1.058 at16° 65° 165° Dribariaiiiven ee ae oe. 16055 atil7> 45° 95° PreOLEIrOt Wee ty a 1.066 at 17° 90° 300° OCLC SS 0 as ne 1.061 at 17° 90° 195° oS eleamser, 0 a or 1.072 at 19° 60° 130° ee ek. LUGO ra ZF bal, eae eee 110° VE TOSCO: Ce Oa I Oa rr | Gs WIS ALTR eat gid: (OU Sear op ape 150° ee emer eo te LeO Ga Alle Coe, ne Ree ee 1202 rg TCaMe ee 1.065 at 17° 80° 190° Diaelanerighle) eae ek we 1.060 at 17° 45° 120° Pen ener eee eT 1.037 at 16° 55° 135° mally we ca the, wee. 100° Bele armen Mer ete ors ey eyelet 2 AD ce ke ue 300 Specific Gravity.According to Bottler and Sabin,* specific gravity determinations are very useful in estimating the value of a resin. The specific gravity of the resin in its usual condi- tion and after being freed from contained air is found. The resins showing the smallest differences contain the least enclosed air and are assumed to be more valuable than their opposites. They find that Zanzibar, thus treated at 15° C., gives 1.0621 *Bottler & Sabin, German and American Varnish Making, John Wiley & Sons. Pages 138-14. 262 EXAMINATION OF PAINTS, VARNISHES AND COLORS and 1.0636, the difference being 0.0015. Lindi copal shows a difference of 0.0010; red Angola 0.014; Camaroon 0.015; Manila 0.059; and Kauri 0.064. A method for specific gravity suggested by Dieterich for rosin and which could be applied to other resins is as follows: A series of solutions of common salt, ranging between sp. gr. 1.070 and 1.085 at 15° C., are prepared, and in each of these is placed a few fragments of the colophony under examination, the temperature being maintained constant. The sp. gr. of the solu- tion which retains the colophony in suspension will be the same as that of the substance. In selecting the test pieces, care must be taken to reject any which exhibit cracks, air bubbles, or im- purities. 7 CHEMICAL EXAMINATION OF FOSSIL RESINS Tschirch and his collaborators, K. Dieterich and others, have done a great deal of work on the various resins and have col- lected much data concerning their composition, and chemical behavior. According to the majority of investigators, varnish resins consist largely of resin acids (resinolic acids) and neutral substances of unknown composition (designated resenes by Tschirch), with small proportions of volatile compounds, ash and impurities. The absence of esters, ethers, anhydrides and lac- tones (except in the case of rosin) has been fairly well estab- lished.* According to Tschirch and Stephen, the composition of Zan- zibar copal is as follows: trachylolic acid (C,,H.,O,), 80 per cent; iso-trachylolic acid (C,,H,.O,), 4 per cent; essential oil, 9.46 per cent; Alpha-resene (C,,H,,0,) and Beta-resene (C,.H,.0,), together 6 per cent; ash .12 per cent; impurities .42 per cent. Congo copal, according to A. Engel+ has the following composition: Congo Copalic Acid (C,,H;,0,.) 48 to 50 per cent; Congo-Copalolic Acid (C,,.H,,0,) 22 per cent; Alpha Con- go-Copal Resene, 5 to 6 per cent; Beta Congo Copal Resene, 12 per cent; Ethereal Oil, 3 to 4 per cent; Impurities and Ash, 4 to 5 per cent. For those resins which contain no other saponifiable com- pounds than the free resin acids, it might be expected that the acid number, determined in the usual manner (i. é., by dissolv- * KE. J. Parry, contrary to most other workers, states that all copals contain esters. + Journal American Chemical Society, 1903; Vol. 25, p. 860. ANALYSIS OF VARNISH RESINS 263 ing the resin in a suitable solvent and titrating directly with KOH solution) would be identical with the saponification num- ber. This, however, is not found to be true in practice. The saponification number (indirect acid number) is usually con- siderably higher than the direct acid number. There are prob- ably several contributing causes for this variation. According to evidence presented by Worstallt (in a very excellent article on Fossil Resins) when a resin is titrated directly with an alkali solution, the resin acids are neutralized very slowly. There are also indications that small amounts of aldehydes may be pres- ent and that these take up alkali during the saponification pro- cess, thus giving a higher figure by this method. Numerous methods have been proposed for determining acid and saponification numbers using different solvents in varying proportions. Widely varying values have been reported, and much of the literature on the subject is highly contradictory. These differences of opinion are undoubtedly due in some cases to actual variations in the samples examined, many being of doubtful origin. In other cases where there is a wide divergence on apparently authentic samples of the same resin, it is probably due largely to a difference in the method employed. Hence re- ported values are meaningless unless the method used is Spe- cifically described. Since many of the resins are insoluble or only partially soluble in alcohol, it is in general advisable to use other solvents. Various mixtures of alcohol, benzine, benzol, ether and chloro- form have been suggested. Alcohol alone is suitable only for rosin, shellac, and possibly Manila. The presence of water in the solution should be carefully avoided. It will not mix with most organic solvents, but forms an emulsion which makes the titration more difficult by render- ing the end point less distinct. Furthermore, according to Dieterich, the addition of water decomposes the resin soaps and results in abnormally high values. An alcoholic KOH solution should always be employed. The following methods of analysis have been used and found satisfactory by the writers. Direct Acid Number.—Weigh three grams of powdered resin into a 500 cc. Erlenmeyer flask and add 200 ce. of alcohol benzol. {Archive der Pharmacie, 1908, p. 293. 264 EXAMINATION OF PAINTS, VARNISHES AND COLORS Allow the mixture to stand overnight in a tightly stopped flask and then titrate with fifth normal alcoholic KOH solution, using phenol-phthalein indicator. Run a blank on the alcohol-benzol at the same time. Both the alcohol and the benzol used as solvents should be re- distilled before using. The alcohol passing over at 78 to 80° C. and the benzol at 80 to 82° C. being collected for the purpose. A fifth normal solution of KOH in C. P. absolute Methyl Al- cohol is used for both acid and saponification numbers. Methyl is preferable to Ethyl Alcohol on account of the difficulty in ob- taining the latter sufficiently free from aldehydes to prevent darkening on standing. Sapontfication Number (Indirect Acid Number).—The same quantities of resin and solvent are used as in taking acid number. An excess of alcoholic KOH is added, the flask tightly stop- pered, allowed to stand 18 hours and then back-titrated with fifth normal sulphuric acid. A blank is run on the same quantity of alkali and solvent as used in the determination. The saponification number may also be determined by boiling the resin-solvent-alkali mixture for 14 hour under a reflux con- denser. The solution is cooled and the residual alkali titrated as before. Saponification numbers determined in this way are somewhat higher than those determined by saponification in the cold. The solvents and alkali solution for saponification numbers are made up in the same manner as those used for Direct Acid — Number. A method recommended by K. Dieterich and used by Worstall* with a slight modification in solvents gives very good results. This method is as follows: Weigh one gram of the finely powdered resin into a glass- stoppered bottle and add 15 cc. benzol and 5 ec. alcohol. Solu- tion is complete in a few minutes with these solvents. Then add 15 ce. fifth normal alcoholic potash solution and allow to stand 18 hours. Add 25 ec. alcohol and titrate the excess alkali with fifth normal sulphuric acid, using phenolphthalein as the indi- cator. Blank determinations are run each time. The addition of alcohol before the titration is a great help in securing sharp end reactions. Acetyl Valuwe.—K. Dieterich proposed the following method for determining the acetyl value of resins: * Journal American Chemical Society, Vol. 25 (1903), page 862. — ee a ee or ee | ee mR ee ee ee ee ae a E ; é | ANALYSIS OF VARNISH RESINS 265 Boil the resin under a reflux condenser with an ex- cess of acetic anhydride and a little anhydrous sodium acetate, until completely dissolved, or until it is evident that no further portion will pass into solution. Pour the solution into water, collect the ensuing precipitate and extract with boiling water until perfectly free from all traces of uncombined acetic acid. The insoluble residues left by copal and dammar are also treated in the same manner. The dried acetylized products are then tested for the acetyl, acid, ester and saponification values by dissolving 1 gram in cold alcohol and titrat- ing with half normal caustic potash. The saponification is also effected with half normal alkali for half an hour under a reflux condenser, and the product titrated back after cooling and dilution with alcohol (not water). As in the case of fats, the difference between the acetyl- saponification value and the acetyl-acid value gives the “true acetyl value.” Resins Other Than Fossil.—Under this heading are included the following types of resins: (1) Resins ordinarily used as solutions in some volatile sol- vent. Prominent in this group are shellac and macassar which are usually applied in alcohol solution and sandarac, mastic, and damar, which are generally cut in petroleum spirits, turpentine or some similar solvent.+ (2) Rosin. (3) Ester Gum. (4) Synthetic resins. These resins are distinguished from the fossil resins in being softer, much more readily soluble in volatile solvents and having lower melting points. As indicated at the beginning of this chap- ter, however, there is no sharp line of demarcation between the classes. For example, both manila and macassar might be classed either as fossil or as alcohol soluble resins. Acid and saponification numbers can be determined by the same methods as used for the fossil resins. While most of them are soluble to a certain extent in alcohol more concordant results will, in general, be obtained when the resin is dissolved in a mix- ture of alcohol and benzol.t Alcohol alone is entirely suitable as a solvent only for rosin, shellac and macassar. + Manila might also be placed in this class as it is soluble in alcohol and is frequently so used. t Sandarac is practically insoluble in benzol. For analytical purposes hot absolute alcohol is the best solvent. 266 EXAMINATION OF PAINTS, VARNISHES AND COLORS Macassar, Sandarac, Mastic and Damar.—These resins are usually evaluated entirely on a basis of color, solubility, size of lumps and freedom from dirt or other foreign material. How- ever, chemical tests such as the determination of acid number are of value in checking up on the uniformity of different shipments. Shellac (see Chapter XX XI). Ester Gum.—The main consideration in the evaluation of ester gum is, as a rule to secure the lowest possible acid number con- sistent with good color. Determination of melting point and the degree of darkening occuring during melting are also important indications of quality. Cumaron Resin and Synthetic Phenol Resins.—Ellis* refers to the de- tection of cumaron resin when mixed with other resins in varnishes pointing out that cumaron resin dissolves completely or almost completely in acetone. Phenol aldehyde resins are insoluble in petroleum spirits, while cumaron resin is partially soluble therein. Phenol aldehyde resins yield quantities of phenols on treatment with soda lime, while cumaron resins yield only traces of these bodies. Natural resins generally have a high acid number, thus differentiating them from the ordinary synthetic resins. Separation of cumaron resins from fatty acids is accomplished by esteri- fication, the esters being sufficiently removed by distillation or extraction with alcohol. Further identification of the resins may be made by de- structive distillation, cumaron resin decomposing at about 800° C., with the formation of cumarine, iodine, etc. Qualitative tests for cumaron resin may be made by color reactions with bromine, cumaron resin giving a permanently red color when treated with bromine dissolved in chloroform, in the presence of glacial acetic acid. Ellis’ method of conducting the test is to use 1 cc. of a 10% solution of the resin in chloroform, subsequently diluting with 6 cc. of chloroform and 1 cc. of glacial acetic acid. The solution is shaken and 1 ce. of a 10% solution of bromine in chloroform is added. The solution is again shaken and al- lowed to stand in a covered container, the presence of cumaron resin being indicated by a permanent red color. Ellis also refers to a method of Steinitzer for the detection of phenol formaldehyde resins, stating that when they are boiled with sodium hy- droxide solution or heated with soda lime, liberation of phenols results, which may be identified by their color reactions. Yacca Gum (Red Gum; Gum Accrotiides). This product which is quite widely used as a shellac substitute in dark colored compositions, is almost entirely insoluble in benzol, mineral spirits, or turpentine. It is readily soluble in acetone, ether, and alcohol. Distillation under vacuo generally yields a phenol body having a strong phenol odor. Analysis of Resin Solutions—Analysis of Solution of Spirit Soluble Resins is given in Chapter XXVIII, page 252. * Synthetic Resins and Their Plastics. The Chemical Catalog Co., Inc. Re Nt ee Se gee ee Pe. ee eee ee a ee a ee ee eee he Ai Vite Siete ets adele bails es Te es 2 eee Pag et oe Bvteore li a oY bed % ‘a sou * = ; CHAPTER XXXI. TENTATIVE METHOD OF TESTING SHELLAC A. S. T. M. Serial Designation: D 29-23 T DETERMINATION OF MATTER INSOLUBLE IN HoT ALCOHOL (a) Continuous Extraction Method (suitable for all grades of lac). APPARATUS 1. The extraction apparatus (Fig 101) shall consist of a wide- neck flask in which is suspended a metal return condenser. From the lower part of this condenser is hung a siphon tube of Knoefler type. The extraction cartridge used for the determin- ation shall be cut down to such a size that the top of the cart- ridge is just above the upper curve of the siphon. It shall be supported on three indentations in the glass so that there will be a little space beneath and around the cartridge to permit of a free flow of liquid. Note.—Any type of siphon extractor where the siphon is continuously surrounded by the vapors of boiling alcohol may be substituted for the above form of apparatus. SOLUTIONS REQUIRED 2. 95-per-cent Alcohol.—Specially denatured alcohol, U. S. In- ternal Revenue Bureau Formula No. 1 or Formula No. 30. METHOD 3. Prepare an extraction cartridge 26 mm. in diameter by 80 mm. in height (Schleicher and Schull No. 603 or the equivalent). Place the cartridge in the extraction apparatus, Fig. 1, and ex- tract for 30 minutes with boiling 95-per-cent alcohol. Dry in an air bath at 105° C., transfer to a glass-stoppered weighing bottle, cool and weigh. Dry to constant weight. A number of cartridges can be prepared and kept in glass-stop- pered weighing bottles until wanted. Now weigh accurately 5 g. of the lac in a 100-cc. beaker and dissolve in 75 ec. of boiling 95-per-cent alcohol by immersing the beaker in a hot water bath until all the shellac is dissolved and the wax is in solution. Transfer this solution quickly into the weighed extraction cartridge, previously wet with hot alcohol, putting the cartridge 267 268 EXAMINATION OF PAINTS, VARNISHES AND COLORS into a carbon filter tube of suitable size supported in a hot water bath (Fig. 2), the outlet tube extending through the bottom of the bath allowing the escape of the filtrate. Wash all the residue from the beaker into the cartridge with hot 95-per-cent alcohol. Put the cartridge in the extraction apparatus (Fig. 101), and ex- tract for exactly one hour. | Keep the alcohol boiling briskly during the extraction. The rate of extraction may be controlled by the use of an electric hot-point stove, 6 in. in diameter, and using the full current of 2.2 amperes at 110 volts. The volume of alcohol in the flask should be 125 cc. Protect the flask from drafts. Under these conditions the tube should siphon over at least 33 times in 1 hour. The condenser should be able to return all the alcohol volatilized during the vigorous boiling of the contents of the flask, the object being to effect the maximum extraction during the specified time. The weight of the residue insoluble in alcohol thus obtained, divided by the weight of the sample, and this quotient multiplied by 100 is the percentage of alcohol insoluble matter in the Tac. NoTe.—When the determination of alcohol-insoluble matter in bleached shellac is required, the sample shall be dried if in the form of bars or hanks or ground shellac, as the water present dilutes the alcohol to a point where solution may not be complete. It is recommended that in preparing shellac for this determination, a separate portion be dried by exposure to the air in a thin layer, without the application of heat. (6) Gooch Filtration Method (Not Applicable for Stick, Seed or Grain Lac and Bleached Shellac). SOLUTIONS REQUIRED 4, 95-per-cent Alcohol.—Specially denatured alcohol, U. S. Internal Revenue Bureau Formula No. 1 or Formula No. 30. METHOD 5. Grind a 50-g. sample fine enough to pass a 40-mesh sieve. Weigh accurately 2 g. of the sample and transfer to a small beaker, heat the shellac with 25 cc. of 95-per-cent alcohol. Pre-— pare a Gooch crucible with an asbestos pad in the usual man- ner’ and dry it to constant weight. Arrange the crucible for “For the preparation of the Gooch crucible see any standard text on quantitative analysis for example, Fresenius (Cohn Translation), p. 120, 1904, or Treadwell-Hall, third edition, Vol. II, p. 26. i i OT ee TS TESTING SHELLAC 269 filtration by suction and pour sufficient boiling alcohol through it to thoroughly heat the crucible. Notre.—A cold crucible will congeal the wax and prevent filtration. Immediately filter the boiling solution through the crucible, using suction, transfer the insoluble material from the beaker to the crucible, using a “policeman” if necessary and a wash bottle containing hot alcohol until the washings are colorless and then wash five more times, nearly filling the crucible each time with boiling alcohol. NoTE.—It will be necessary to shut off the suction momentarily to fill the crucible. Wash off any film of shellac on the sides or bottom of the crucible with hot alcohol and dry to constant weight in an oven at 105 to 110° C. The weight of the residue in the crucible, multiplied by 100 and divided by the weight of the sample, is the percentage of material insoluble in hot alcohol. DETERMINATION OF ROSIN SOLUTIONS REQUIRED 6. Acetic Acid.—99-per-cent glacial acetic acid having a melt- point of 14.8° C., free from reducing impurities as shown pies its action on a eliveriate in sulfuric acid. Notre.—If these requirements are not met the results of the rosin deter- mination will be erratic. Iodine Monochloride Solution.—Dissolve 13 g. of iodine in a liter of acetic acid, using gentle heat if necessary, determining the strength by titration with thiosulfate. Set aside 50 to 100 ec. of the solution and introduce dry chlorine gas into the re- mainder until the characteristic color change occurs, and the halogen content has been doubled. By titration, ascertain if the halogen content has been more than doubled, and if so reduce it by adding the requisite quantity of the iodine acetic acid solu- tion. A slight excess of iodine does no harm but an excess of chlorine must be avoided. Chloroform.—Should be chemically pure. Sodium Thiosulfate Solution—Dissolve 24.83 g. of the pure galt in a liter of cold, boiled, distilled water. Standardize by titrating against freshly resublimed iodine. It 1s recommended that the resublimed iodine be collected into a glass-stoppered weighing bottle and weighed after cooling. Starch Solution.—Dissolve 0.2 g. of starch per 100 cc, of water and boil. 270 EXAMINATION OF PAINTS, VARNISHES AND COLORS METHOD 7. Introduce 0.2 g. of ground shellac into a 250 cc. dry bottle of clear glass with a ground-glass stopper, add 20 cc. of glacial acetic acid and warm the mixture gently on top of a hot water bath until solution is complete (except for the wax). A pure Shellac is rather difficultly soluble; solution is quicker according to the proportion of rosin present. Add 10 ec. of chloroform and cool the solution to 21.5 to 22.5° C. The bottles should be allowed to stand half immersed in a shallow pan of water, well insulated or equipped with a suitable thermostat, at least 30 minutes at 21.5 or 22.5° C. before the Wijs solution is added. Add 20 cc. of Wijs solution (which shall be at a temperature of 21.5 to 22.5° C.) from a pipette, having a rather small de- livery aperture (about 30 seconds). Close the bottle, place it back into the pan of water, and note the time. The bottles must be kept half immersed in water at 21.5 to 22.5° C. during the one hour that the shellac is exposed to the Wijs solution. Agitate the bottles occasionally during that hour. Notre.—If a number of samples are being run, at least 5 minutes should be allowed between the addition of the Wijs solution. After exactly one hour, add 10 ce. of freshly prepared 10-per- cent potassium iodide water solution, washing into the bottle any Wijs solution on the stopper with the same. Titrate the solution immediately with the 0.1 N sodium thiosulfate solution, allowing the solution to run in slowly (about 25 to 30 cc.) with vigorous shaking until the solution becomes a straw color. Now add 15 cc. of freshly prepared starch solution and finish titrat- ing. The end point is sharp, as the reaction products of shellac remain dissolved in the chloroform; any color returning after 14 minute or so is disregarded. A blank determination shall be run at the same time on the reagents. The blank is necessary on account of the well-known effect of temperature changes on the volume, and possibly loss of strength of the Wijs solution. A sample of pure shellac of known iodine value should also be run with every set of tests on unknown samples. In the case of grossly adulterated samples, or in the testing of pure rosin, it is necessary to use, instead of 0.2 g. of material, a smaller amount (0.15 g. or 0.1 g.) in order that the excess of iodine monochloride may not be too greatly reduced, since the excess of halogen is one of the factors in determining the amount De a Ee Ee eT ae ae ee ee ee ee ee ee, ee Nall 1 ea Nal al TESTING SHELLAC 271 of absorption. In case less than 25 cc. of the thiosulfate solution are required, another test should be made, using a smaller amount of the shellac to be tested. In weighing shellac, some difficulty is at times experienced on account of its electrical properties. In very dry weather it may be found that the necessary handling to prepare it for weighing has electrified it, and it may be necessary to leave it on the bal- ance pan at rest for a few minutes before taking the final weight. No pure shellacs show a higher iodine absorption than 18. As pure shellac is relatively a high-priced material and as the variation between its highest and lowest figures is not great, it is recommended that 18 should be taken as the standard figure for rosin-free shellac, determined by the method above de- scribed. The determination for added rosin in bone-dry bleached shellac is run the same as above, except that the iodine absorption of pure bleached shellac is taken as 10 instead of 18. It is recommended that the value for the iodine number of rosin be taken as 228. The results of using in this method the value of 18 as the iodine number of shellac and 228 as the num- ber of rosin, may be that a slightly lower percentage of rosin, under some circumstances, will be found than that which is actually present. The percentage of rosin shall be determined from the formula: EMMI UREN OT COE eS ICL AC cc5 iil con nck, Secchccher tesa lbnaMe lets d dee ee 18 e f ROMP Sti ae, < - ee Pya ee a ag renee oe 228 ae - BOTTA KUNA VC) oh eee Fe ta al Ao uu ae es eR ig 1 («2 — 18) ee , (228 — 18) < 100 = percentage of rosin lodimesniumber of, bleached: shellac... 2 10 at : EE COLT E Se fk le tk I ak eS Rie ee 228 _ ‘ BePINISLUPOr ee se ee ee eet oe ae ets eae Ay (2 — 10) (228 —10) x 100 = percentage of rosin DETERMINATION OF MOISTURE IN SHELLAC 8. Both orange and bleached shellac give off volatile matter at temperatures approaching 100° C. Bleached shellac alters chemically at these temperatures, losing its solubility in alcohol. For these reasons the usual methods of determining water by heating in the air bath at 100 to 110° C. are not applicable in the analysis of shellac. 212 EXAMINATION OF PAINTS, VARNISHES AND COLORS SAMPLING 9. Bleached shellac is sold in three forms: as hanks or bars containing approximately 25 per cent of water, as ground bleached in pulverized form with about the same water content, and as bone-dry or kiln-dried shellac. The latter is prepared by drying the ground bleached shellac in the air or in vacuum driers at moderate temperatures. It may contain, depending upon the completeness of the drying and weather conditions, up to 10 per cent or more of water. 10. Bone-Dry Shellac.—In sampling bone-dry bleached shellac about 1 lb. should be taken from different parts of the barrel and finely ground by running through a coffee mill. No attempt must be made to sieve it. It is rapidly mixed and transferred to a Mason jar provided with a screw cap and rubber ring seal. The jar should be filled not more than two-thirds full, leaving — room for a thorough mixing by shaking the contents. It shall be kept in a cool place and tested as promptly as possible. If too warm the shellac may become partially solidified, in which case the lumps must be broken up by shaking the bottle. 11. Bars or Hanks.—In sampling bars or hanks it is recom- mended that a whole hank be taken. It is crushed and ground as rapidly as possible. : 12. Ground Bleached Shellac_—Ground bleached shellac may be treated as above, bearing in mind that the large amount of moisture present makes rapid handling imperative. METHOD 13. Bone-Dry.—Weigh 5 g. of the finely ground sample in a flat-bottomed dish about 4 in. in diameter and place the dish in a well-ventilated air bath from three to six hours at 38 to 43° C. One or two electric light bulbs provide a convenient source of heat. The temperature should not be allowed to rise above AB oC NOTE.—With poorly ventilated ovens the drying may take much longer. Completeness of drying should be ascertained by continuing the treatment to constant weight. The standard is 5 per cent of moisture. 14. Hanks and Ground Bleached.—Proceed ag in Section 13, but with this one exception, that the dish and its contents are allowed to dry in the air or in a sulfuric acid desiccator over night before it is placed in the air bath. The standard is 25 per cent of moisture. : y re a 3 4 . _ of : 2 a & TESTING SHELLAC ha 15. Orange Shellac——Proceed as in the case of Section 13. Orange shellac contains between 1 and 2 per cent of moisture. Direct Method for Rosin in Shellac.—A direct method for de- termining the amount of rosin in shellac has long been desired. Such a method is being worked out by the Bureau of Standards and promises to be very satisfactory. It is based upon the solu- bility of rosin in certain light fractions of petroleum hydrocar- bons. See the Bureau of Standards Technologic Paper No. 282. This petroleum ether method has not superseded the Wijs iodine method where a numerical value for percentage of rosin is de- sired. It is, however, of great value in determining the adulter- ation of shellac varnishes. STEELE MODIFICATION OF THE MCILHINEY METHOD FOR THE DETECTION AND ESTIMATION OF ADULTERANTS IN SHELLAC VARNISH Petroleum ether distilling between 55 and 75° C.* was ob- tained by the distillation on the steam bath of either commercial petroleum ether or aviation gasoline, fighting grade.+ Glacial acetic acid was diluted with water until its solidification point was between 13 and 14° C. Method.—In case of a shellac varnish, determine the percent- age of nonvolatile matter. Place a portion of the well mixed sample in a stoppered container. Weigh the container and sample. Transfer a weight of the sample corresponding as closely as practicable to 2 g. of nonvolatile matter to a 2-liter Florence flask, the neck of which has a volume of over 100 cc. and restopper the container. Weigh the container again and by difference calculate the exact weight of the portion transferred to the flask. Calculate the exact weight of Shellac in the sample taken from the percentage of nonvolatile matter in the varnish. The procedure from this point is the same for dry and cut shellac. Add 20 ce. of the special acetic acid and. heat the flask until the shellac resin and wax are dis- solved. With certain shellac adulterants there may be a small amount of resin which can not be dissolved. Cool the flask to room temperature (19-21° C.), whereupon a part of the natural * A fraction with initial boiling point of 40° C. should be satisfactory, provided it is not used in extremely hot weather. + Bureau of Mines Technical Paper No. 323, p. 1. 274 EXAMINATION OF PAINTS, VARNISHES AND COLORS shellac wax usually separates. Add slowly from a pipette 50 cc. of the petroleum ether cooled to 19-21° C., with constant shaking of the flask, allowing one to two minutes for the addi- tion. Add all at once from a graduated flask 100 ce. more of the petroleum ether kept at 19-21° C., stopper the flask and shake vigorously. While shaking the flask, slowly add tap water kept at 19-21° C., until the shellac has separated as an amorphous mass. Half fill the flask with water and agitate so as to thoroughly wash the ether layer. Add water until the petroleum ether layer nearly fills the neck of the flask, cork and let the flask stand until the ether layer is free from suspended particles. Transfer 100 cc. of the ether layer to a 100 ce. gradu- ated flask. It is convenient to fit the large flask with a two-hole stopper with tubes arranged like a wash bottle, so that the ether solution can be blown into the graduated flask. Evaporate the 100 cc. of petroleum ether solution, portion wise if necessary, in a small weighed Erlenmeyer flask on a hot plate. When the dry point is reached, suck out the residual solvent vapors, cool the flask, and weigh. The weight of the residue multiplied by 150 and divided by the weight of shellac taken is the percentage of “matter soluble in petroleum ether.” Dissolve this residue in 25 cc. of a mixture of equal volumes of 95 per cent denatured alcohol and benzol (the mixture should be previously titrated to a faint pink color with dilute alkali, using phenolphthalein as an indicator) and titrate in the cold with 0.1 N alcoholic sodium hydroxide with phenolphthalein as an indicator. Calculate the acid number of the “matter soluble in petroleum ether” (milligams of KOH required for 1 g. of petroleum ether residue). Transfer most of the petroleum ether layer remaining in the Florence flask to a small beaker or flask and evaporate to dryness. Test this residue for rosin by means cf the Halphen-Hicks test already referred to. Report a faint purple or blue coloration as “faint test for rosin” and a deep purple or blue as “decided test for rosin.” An examination of the results on many samples tested by this method indicate that a large number of the samples of shellac _ were free from rosin, as shown by a qualitative test and by an iodine value below the arbitrary accepted limit of 18. Such samples can probably be safely considered as unadulterated Shellacs. These samples of pure shellac, with few exceptions, “Se TESTING SHELLAC 275 yielded values between the limits of 6.0 and 7.0 per cent for ma- terial soluble in petroleum ether and acid values for this residue between the limits of 60 and 90. TABLE XLVI—Suggested Method for Rating Samples of Shellac Purity Pure. Slightly adulterated; probably 1—2 per cent rosin, as in ‘‘Superfine”’ Suspicious; no adulteration proved. Somewhat adulterated; probably a ‘‘T.N.” shellac. Somewhat adulterated with an adulterant other than rosin. Badly adulterated; possibly as high as 40 per cent adulteration. Grossly adulterated; possibly no shellac present. Petroleum Acid number of ether soluble Rosin test residue percentage @usoriess.... | Negative......... BOSONS ace nice: ROO). te cook es POSITIVE «cal oc ws May be greater or less than 90. Hees Os. oes ee WNP ALIVE™s tal) uc ela ce en GOme to whe teak OOO. 2 HPOSLULV.G@r artless Generally, but not always over 90. 3101 0 St a Oa INGHAM NE Se AERA ONS See c fy See cee B12:0=20:0). =... Positive or nega- |..... olen: See eee tive. PETE Met ered Osh ce os sles oor | die eae 's Gans teas eigen: oa & ’B S ——e os iy | 5 ' N eS + Se H ! FI 5 S : 5 § : Ley Depression’ | ‘ ee a Extraction Apparatus for Alco- hol-Insoluble Matter FIGURE 101 Filtering Device Apparatus Used in Testing Shellac A. S. T. M. Method CHAPTER XXXII. TESTING INSULATING VARNISHES Methods for testing the types of insulating varnishes used in ~ America have been worked out by a special committee of the American Society for Testing Materials. The tentative methods — adopted are as follows: TENTATIVE METHODS OF TESTING INSULATING VARNISHHES. A. S. T. M. Serial Designation: D 115-23 T. — Issued, 1921; Revised, 1922; 1923 1. These tests are intended for varnishes which are applied by brushing, dipping or spraying, and are primarily for the pur- pose of providing electrical insulation. Specific Gravity 2. The specific gravity shall be measured with a pyknometer, Westphal balance or with a hydrometer so graduated that the specific gravity can be determined to 0.001. The temperature ‘ of the varnish shall be not less than 18° C. (64.4° F.) nor more — than 22° C. (71.6° F.) and corrected to 20° C. (68° F.) by ap- plying a correction of 0.0007 per 1° C. (0.0004 per 72) Viscosity 3. (a) The vicoscity shall be determined with a Stormer or — MacMichael viscosimeter and shall be stated in terms of the q viscosity of distilled water determined with the same instrument _ under the same conditions. The short-tube type of efflux vis- cosimeter usually employed for lubricating oils is not acceptable. The temperature of the varnish shall be 20° C. (68° F.). (6) The report shall include such details as the kind of in-~ strument used, the size of the counterweight if a Stormer instru- ment is used, or the size of the wire in case the MacMichael in- strument is used, etc. Flash Point 4. The flash point shall be determined in accordance with the Standard Method of Test for Flash Point of Volatile Flammable — 276 en TE ee a ae ee ae, ee INSULATING VARNISHES prareye Liquids (Serial Designation: D 56) of the American Society for Testing Materials.* Time of Drying 5. (a) Specimens for this test shall be pieces of thoroughly cleaned, smooth sheet copper or brass about 3 cm. (1.18 in.) wide and 20 cm. (7.88 in. long and about 0.127 mm. (0.005 in.) thick. (6) The specimen shall be dipped once in the varnish at a room temperature of approximately 20° C. (68° F.) and with- drawn slowly and uniformly (about 38 cm. (15 in.) per minute). The consistency of the varnish shall be first so adjusted by trial that, when dry as determined in accordance with Section 7, the thickness of the film of varnish on each side of the metal shall be between 0.022 mm. (0.0009 in.) and 0.026 mm. (0.001 in.). Care shall be taken before dipping the specimens that the var- nish has stood in the dipping tank for a sufficient length of time to be free from air bubbles. 6. (a) Specimens of air-drying varnish shall be dried in free air at a room temperature of approximately 20° C. (68° F.). (b) In the case of baking vanishes, six specimens shall be dipped and allowed to drain at a room temperature of approxi- mately 20° C. (68° F.) until the varnish is set as indicated when the impression left on the surface by pressing lightly thereon with a finger will not become obliterated by further flow of the material. They are then to be dried in free air in an oven at approximately 100° C. (212° F.). At the end of the first 30 min- utes, and again at the end of each 10-minute period thereafter, one specimen shall be taken from the oven and examined. In the case of slow-drying varnishes, this 10-minute period may be lengthened at the discretion of the operator. 7. The varnish shall be considered dry when a specimen will not stick to itself when folded and pressed together between the thumb and finger at a temperature of approximately 20° C. fos i.) Dielectric Strength Test 8. (a) Specimens for the dielectric strength test shall be pre- pared by dipping pieces of thoroughly cleaned, smooth sheet cop- per or brass about 20 cm. (7.88 in.) square and about 0.127 mm. (0.005 in.) thick into the varnish which shall be at the con- sistency prescribed in Section 5 (0). * 1921 Book of A. S. T. M. Standards. 278 EXAMINATION OF PAINTS, VARNISHES AND COLORS (b) Each specimen shall be dipped twice, as specified in Sec- tion 5 (b), once in each direction, in order to give a more uni- form thickness of coating. The specimen shall be dried after each dip in the same vertical position in which it was dipped. (c) Specimens of air-drying varnish shall be dried in free air after each dip at a room temperature of approximately 20° C. (68° F.) for a period of 600 per cent longer than that deter- mined in accordance with Section 7, provided such period does not exceed 24 hours. (d) Specimens-of baking varnish shall be drained and then baked after each dip for a period of 300 per cent greater than that determined in accordance with Section 7 provided such pe- riod does not exceed 24 hours. (e) The final thickness of the film of varnish on each side of the specimen shall be between 0.089 mm. (0.0035 in.) and 0.102 mm. (0.004 in.). 9. (a) The dielectric strength of the two films of varnish shall be determined by applying alternating potential to two circular metal disks, 3 cm. (1.18 in.) in diameter and with edges rounded to a radius of 0.64 em. (0.25 in.) which are placed in contact with the two sides of the specimen directly opposite each other and under a pressure of approximately 0.5 kg. (1.1 lb.). The potential shall be applied at a low value and gradually raised at a rate such that puncture will occur in about ten to fifteen seconds. Ten such punctures are to be made at various points selected at random on each specimen. In each test the thickness of the films of varnish is to be determined as close to the point of puncture as practicable. Note.—When necessary, in order to get ten punctures, an additional specimen should be tested. (6) The frequency of the test potential shall be not greater than 100 cycles per second, and each part of the testing appa- ratus shall have a continuous rating of not less than 2 kva. (pre- ferably larger).- The wave form shall be a sine curve as defined, and the voltage shall be measured by methods approved by the American Institute of Electrical Engineers.* (c) The voltage may be controlled by any approved method which does not distort the wave from beyond the limits pre- scribed above and which does not subdivide the voltage in steps * Standards of the American Institute of Electrical Engineers. INSULATING VARNISHES 279 greater than 500 volts. The apparatus shall comply with the Standards of the American Institute of Electrical Engineers. 10. The volts at puncture, the net thickness of insulation and the volts per mil of net thickness shall be reported for each of the ten tests together with the average maximum and minimum volts per mil. Water Absorption Test 11. Specimens similar to those described in Section 8 shall be immersed in water at a room temperature of approximately 20° C. (68° F.) for a period of 24 hours. Upon removal from the water, the surface water shall be wiped off and dielectric strength tests made immediately as described in Section 9. 12. The volts at puncture, the net thickness of the insulation and the volts per mil of net thickness shall be reported for each of the ten tests, together with the average, maximum and mini- mum volts per mil. | Heat Endurance Test 18. For the heat endurance test, specimens shall be prepared as in Section 8. After removing not less than 1.27 cm. (0.5 in.) from one edge of the specimens, the number of strips required by Section 14 (a) shall be cut from the same edge, each 1.9 cm. (0.75 in.) in width. 14. (a) After setting as shown by the test indicated in Section 6 (b), the strips referred to in Section 13 shall be placed in a uniformly heated oven in which the temperature is maintained at 100° C. (212° F.) within + 5° C. (9° F.). A strip shall be removed at the end of 1, 2, 4, 8 and 24 hours respectively and every 24 hours thereafter. These, together with the initial strip, shall be tested as follows at a room temperature of appoximately oy 2G. (68°. EF.) : (b) Each specimen shall be bent through 180 deg. over a rod 0.32 cm. (1% in.) in diameter. The number of hours of baking at which first cracking in the insulation occurs shall be noted and reported. Acid and Alkali Proof Test 15. The specimens to be used for the test for acid and alkali proofness shall be brass rods 1.5 cm. (0.59 in.) in diameter, 15 em. (5.90 in.) long and carefully rounded at one end to a radius of 0.75 cm. (0.295 in.). These specimens shall be dipped three times into the varnish, leaving exposed about 3 cm. (1.18 in.) 280 EXAMINATION OF PAINTS, VARNISHES AND COLORS of the rod at the end opposite the rounded end. Each coat shall be dried 25 per cent longer than the period determined in Sec- tion 7. Three specimens each shall be prepared for the acid and alkali solutions. 16. (a) The three specimens shall be suspended in the acid or alkali whose effect it is desired to determine to within 3 ecm. (1.18 in.) of the end of the coated portion of the rod and suit- able provision made for detecting the change in the electrical resistance between the rod and the solution. (Note 1.) (6) It is recommended that these tests be made in 10-per-cent solutions as follows: Sulfuric acid of sp. gr. 1.069 at 60° F. (15.5° C.) or nitric acid of sp. gr. 1.056 at 60° F. (15.5° C.) or hydrochloric acid of sp. gr. 1.050 at 60° F. (15.5° C.) and sodium hydroxide of sp. gr. L145 at 607 (15:5. (c) The temperature of the solution shall be kept at approx- imately 20° C. (68° F.). NoTE 1. A simple method is to connect a voltmeter between each rod in turn and one side of a 110-volt direct current circuit, the other side of the circuit being connected to the solution through any piece of suitable metal suspended in the solution. The resistance will be inversely proportional to the deflection of the voltmeter pointer, that is, the smaller the deflection, the greater the resistance. Failure of the material will, therefore, be in- dicated by a sudden increase in the deflection of the voltmeter pointer. 17. The resistance between each rod and the solution shall be measured once per day and the number of days elapsing before breakdown occurs shall be taken as the “proofness” of the var- nish. Oil Test 18. For the test for the effect of oil, pieces cut from the speci- mens prepared for the dielectric strength test (Section 8) may be used after they have been punctured and measured. 19. The effect of oil on the varnish shall be determined by im- mersing the specimens in transformer oil at a temperature of 100° C. (212° F.) for 48 hours and noting the effect on the var- nish as indicated for example, by wiping with a piece of dry white cloth. NotTe.—Incipient disintegration of the surface of the varnish may some- times be detected by examining the oil for turbidity. If a specimen of the oil filtered through filter paper can be distinguished from an unfiltered sample when the two samples are held in front of a strong light, the oil is turbid. INSULATING VARNISHES 281 Draining Test (Also known as “Working Viscosity” Test) 20. A strip of bond paper 0.064 mm. (2.5 mils) in thickness, 10.2 cm. (4 in.) in width and 50.8 cm. (20 in.) in length, shall be immersed in the varnish at a room temperature of approximately 20° C. (68° F.) up to a line previously drawn across the paper a few inches from the top. The paper shall be withdrawn at a slow and uniform rate, care being taken that the varnish is free from air bubbles. The specimen shall be permitted to drain thoroughly at room temperature while suspended in a vertical position. It shall then be dried or baked (according to the type of the varnish) until dry as determined in accordance with Sec- tion 7. 21. The thickness of the specimen in mils shall be measured at points 5.1 cm. (2 in.), 17.8 cm. (7 in.) and 30.5 cm. (12 in.), respectively, from the line to which the specimen was immersed. 22. The thickness of each film in mils at the three points speci- fied in Section 21 shall be recorded. The difference between the thickness at the upper point (5.1 cm.) and that at the lower point (30.5 cm.) shall be taken as a measure of the variation in the film thickness caused by draining. Evaporation Test 23. One hundred cubic centimeters of the varnish shall be placed in a flat-bottom crystallizing dish approximately 75 mm. (2.95 in.) in diameter and 45 mm. (1.77 in.) in height. It shall be heated to a temperature of 100° F. (37.8° C.) + 2° F. (1.1° C.) for a period of 7 hours, the sample being exposed to still air in the open room. 24. The decrease in volume of the sample shall be taken as the evaporation, this decrease being determined by noting the amount of water or kerosene that must be added to fill the dish to the original level. NoTE.—This test is relative only. That is, it is only suitable for com- paring one varnish with another when the tests are made simultaneously under exactly the same conditions. Test for Non-Volatile Matter 25. A portion of the sample shall be placed in a stoppered bot- tle or weighing pipette and weighed. About 1.5 g. of the sam- ple shall be transferred to a weighed flat-bottom metal dish about 282 EXAMINATION OF PAINTS, VARNISHES AND COLORS 8 cm. (3.15 in.) in diameter, such as the cover of a friction-top tin can. The container shall again be weighed and the exact weight of the portion of the sample transferred to the weighed dish calculated by difference. The dish with its contents shall be heated for three hours in an oven maintained at 105 to 110° C. It shall then be weighed after cooling. 26. The ratio of the weight of the residue to that of the orig- inal sample expressed as a percentage shall be taken as the per- centage of nonvolatile matter in the varnish. CHAPTER XXXTIT. EXAMINATION OF PYROXYLIN LACQUER COATINGS Heretofore but little information has been published on the analysis of soluble cotton solutions, with the exception of that given by Zimmer.* Additional matter of a later character is pre- sented below, including material used by the writer for several years and data submitted through the kindness of J. B. Wiesel, Dr. I. M. Jacobsohn, and Dr. Hugo Schlatter. No comprehensive scheme of analysis has yet been devised which may be considered suitable for all types of nitrate lacquers. In the analysis of such lacquers, much depends upon the experience and ingenuity of the analyst. He must obtain clues as to the ingredients present, and must then devise methods to suit the particular mixture at hand. The separation, identification, and quantitative determination of mixtures of organic solvents, particularly those of similar chemical and physical properties, e. g., butyl and amyl acetate, and those yielding constant boiling mixtures, are very difficult procedures for which methods of analysis cannot be devised without a definite knowledge of all of the ingredients present in the par- ticular lacquer under examination. The experienced analyst will find a physical examination of the lacquer of great value in obtaining clues as to the identity of the solvent mixture. The determination of the specific gravity, viscosity, color, luster or dullness upon drying, behavior upon flowing on glass or spray- ing on sheet metal, thickness of film obtained, and the detection of the various solvents and thinners by odor, will all be of great aid to the experienced analyst in judging the probable composi- tion of a given lacquer. For instance, in testing airplane dopes it is usual to apply five coats of the dope by a brush to standard airplane cotton stretched tautly upon an open frame. Duplicates are exposed with and without a top coating of finishing enamel made either with pig- mented dope or pigmented varnish; the latter usually being preferable. After three months, the tautness of the cloth, the elasticity of the film and the breaking strength of the cotton *Zur Analyse der Zapon und Zelluloidlacke. Fr. Zimmer. Kunststoffe, 8, 823 (1918). Chem. Abs., 8, 582 (1914). 283 284 EXAMINATION OF PAINTS, VARNISHES AND COLORS cloth, warp and filling, are determined. For exposing panels of nitro-cellulose finishes for automobiles the writer uses black iron plates and either applies the dope by brush or by spray gun in one coat work, exposing duplicates with and without a top coat- ing of finishing oil varnish. While this method does not dupli- cate the conditions obtaining in the finishing of automobiles, © where several coats are applied sometimes over eleo-resinous var- nish primers and fillers, it does give a quick indication of the durability of different types of dopes that are made for experi- mental purposes. It is obviously impossible to give in one chapter in this, book complete information regarding the examination of all such — compounds as might be derived from aliphatic acids. A study of such derivatives of alcohols, including the various esters that can be produced with formic, acetic, propionic, and other acid derivatives, should be made by the reader, of such extended books on the subject as Allen’s Commercial Organic Analysis, and Lewkowitsch. Weight per Gallon Determination.—The pyroxylin solution is adjusted to a temperature of 20° C., and weighed in a marked cylinder; the weight of the equivalent volume of water at the same temperature being previously determined. Weight of pyroxylin solution Weight of equivalent volume of water Se ie Specific gravity x 8.34—Weight per gallon Specific Gravity—tThe specific gravity determination is made as outlined above or with a pyconometer. The determination is made at 15.5° C. Viscosity Determination.—For thin solutions—one to six ounces—the viscosity is determined by using a water-jacketed pipette, which is standardized to deliver 100 ec. of water at 25° C. in eight seconds. The number of seconds required for the pipette to deliver 100 cc. of the pyroxylin solution at 25° C. is the viscosity of pyroxylin solution. Much more accurate deter- mination may be made by comparing the solutions poured in glass tubes with Gardner-Holdt viscosity standards. For all heavy solutions, the viscosity is determined by the steel ball method. The viscosity in this method is equal to the number of seconds that it takes a steel ball 5/16” in diameter to fall — re oes EL ual Rit nat oe ee a eae Re eT Eee eae EO ee Tee eae PYROXYLIN LACQUER COATINGS 285 through ten inches of the pyroxylin solution at 25° C. A glass tube is to be used, which is at least fourteen inches long and only one inch wide, and: with the bottom mark of the required _ ten inches at least one inch from the bottom of the tube. Effect on Metal.—Much information can be obtained regard- ing the non-corrosive properties of a clear lacquer or of the sol- vents to be used in a lacquer, by evaporating 50 cc. in a brightly polished spun copper dish. The presence of free acid in the solvent, usually developed by the hydrolysis of the esters, or of free acid developed in lacquers from unstable nitrated cotton, will cause a green discoloration. The evaporation may be made on asteam bath. The residue, if any is present, may be weighed. Free Acidity.—Add to 20 gms. of a clear lacquer, with con- stant stirring, 40 c. of a neutralized mixture of 50 per cent de- natured alcohol and 50 per cent of water. Then add diluted neutralized denatured alcohol until all the solids are precipitated and the supernatent liquid is clear. This liquid is then decanted and the precipitate washed by decantation with a small amount of neutralized denatured alcohol. The decanted liquid and washings are then titrated with N/10 sodium hydroxide, using phenolphthalein as indicator, until a faint pink color persists for at least ten seconds. To neutralize the denatured alcohol in the’ above procedure, add a few drops of phenolphthalein indicator, and then N/10 sodium hydroxide, drop by drop, with constant stirring, until a faint pink color appears. Pigment Separation.—The separation of pigments from a pigmented lacquer is usually a very difficult thing. Even when as low as 10 grams of pigmented lacquer are thinned with as high as 100 grams of a mixed solvent, and centrifuged for an hour, the colloidal nature of the lacquer is often such as to cause some finely divided pigments to remain in suspension. Filtering through double layers of filter paper will not remove such pig- ments, For this reason, it is customary in many instances to merely ash at low temperature a 20 gram sample of the lacquer, first having gotten rid of the volatile constituents by evapora- tion. The residue from ignition may be examined in accord- ance with the methods outlined for the examination of pigments in other chapters of this book. Zine oxide, lithopone, and titanium oxide are, however, the white pigments usually used in white lacquers. When Prussian blue is used, it is neces- sary to make a nitrogen determination on the residue from 286 EXAMINATION OF PAINTS, VARNISHES AND COLORS evaporation, and then calculate the Prussian blue from the ; nitrogen content (see Chapter XLI on blue pigment analysis). If this method is used allowance must be made for nitrogen com- ing from nitro-cotton present, the amount of which must be de- 4 termined. Where organic colors are present, such as paranitran- iline, toluidine reds, and similar toners, the determination of the exact amount of pigment present is almost an impossibility. ~ These pigments would be destroyed in a determination of igni- tion residue. Because of their very fine subdivision, they usually — cannot be removed by centrifuging. One method, however, that % can be tried is to add to the colored lacquer sufficient water to precipitate the cotton present, which will carry down with it the majority of the pigment present. After removal of the solvent and water, the mixture of cotton and pigment can be dried. The cotton as a rule can be largely extracted with a very : light volatile ester such as ethyl acetate. Some pigmented lacquers, however, readily yield their pigment content by centri- fuging a mixture of 10 grams of lacquer and 100 grams of mixed solvent (1/3 ethyl acetate, 1/3 benzol, 1/3 acetone). If the re- — moval of the pigment by extraction is successful, the analytical procedure should follow that given in Chapter XXXYV. Total Solids (Method A).—Evaporate carefully, to constant weight, on a friction top can lid, a 5 gm. sample of the lacquer, stirring occasionally to break the “skin” which forms at the surface upon the evaporation of the solvents. The solid residue upon evaporation may consist of pure cellulose nitrate, of mix- tures of cellulose nitrate and camphor, or tri-cresyl phosphate, or various resinous and oily materials, in the case of clear lacquers, or these various ingredients mixed with pigments in the case of pigmented lacquers. This method not as accurate as method B on account of difficulty of getting rid of last traces of solvents. Total Solids (Method B).—A sample (5 to 10 grams) is _ weighed out as rapidly as possible in a tared aluminum can with a tight fitting cover. About 100 cc. of an ether-alecohol mixture (2 to 1) is added, and the mixture stirred until a homogeneous mass is obtained. The ether-alcohol solution is then brought to a boil over a hot plate or a steam bath and 25 ec. of water is added very slowly, with continual stirring. The stirring is then continued until the solvent is evaporated off. The stirring is es- sential, in order to avoid colloidal precipitate. If the precipita- ee ee a ae ee ee go ee ee PYROXYLIN LACQUER COATINGS 287 tion is carried out as outlined, a stringy precipitate is obtained. A precipitate in this form dries more easily than a lumpy pre- cipitate. The solution is evaporated to dryness on a steam bath, and then placed in an oven at 100° C. + 1° C. for two hours; cooled in a desiccator for a half (14) hour and then weighed. Weight of evaporated material in aluminum can x 100 Weight of sample _ If a cloud is formed on the addition of water to the ether-alcohol solution, the presence of camphor is indicated. When camphor is present, it is necessary to make two or three additions of water, evaporating to dryness after each addition in order to drive off all of the camphor. The percentage of camphor may be de- termined by the refractometer, as given in Allen’s Commercial Organic Analysis. The presence of oil in this pyroxylin solution is indicated by an oily feel and appearance of the total solids residue. The presence of gums is sometimes indicated by the dark brown appearance and brittleness of the total solids residue. When oils or gums are present, a weighed portion of the total solids residue is placed in a paper thimble, and is extracted with alcohol-free ether or chloroform in a Soxhlet extraction tube for four hours. The ether or chloroform, containing the oils or gums in solution, is transferred to a tared beaker and evapo- rated to dryness. Increase in weight divided by the weight of the sample times 100, gives the percentage of oils and gums in the total solids. To identify the oil or gum used, see methods of oil and resin analysis, elsewhere in this volume. The acid value, iodine number, and saponification number of this residue will give much information. Volatile Constituents—Distill a sample of approximately 150 grams of the lacquer, in steam. Add to the distillate sufficient sodium chloride to make a 20% solution of the aqueous layer, thus “‘salting out” certain of the solvents and thinners. Separate the two layers, oily and aqueous. Fractionate the aqueous layer, which should contain alcohol and acetone, if present. The presence of alcohol can be detected in the higher boiling fraction. The oily layer is referred to below for further examination. Acetone Content Determination.—The acetone content is de- termined by the Messinger Method.* Careful attention should be given to details, in order to get accurate results. It should be = % total solids * Allen’s Commercial Organic Analysis. 288 EXAMINATION OF PAINTS, VARNISHES AND COLORS remembered that some other solvents such as iso-propyl alcohol give the iodoform reaction. Sulphuric Acid Insoluble-——Equal volumes of 95% sulphuric acid and the oily layer secured as under determination of vola- tile constituents are placed in a glass-stoppered, graduated cylinder. The acid should be added very slowly with continued agitation. The mixture is well shaken and allowed to stand until there is a complete separation. The volume of the upper layer is the amount of distillate insoluble in sulphuric acid. These are hydrocarbons such as benzol, toluol, ete. Saponification Value.—Duplicate samples of from four to seven grams of the “oily layer’? dried over fused calcium chloride are weighed into a pressure flask. Fifty cc. of approximately normal alcoholic KOH is added. The pressure flask 1s heated in an oven at 100° C. for one hour. It is advisable to wrap the pressure flask in a towel before placing in the oven, as there is danger of explosion. The flask should be shaken three or four — times while being heated. A blank determination is made on the alcoholic KOH at the same time as the distillate is being saponified. The saponified material in the pressure flasks is al- lowed to cool, and is then titrated with N-2 HCl, using phenol- phthalein as an indicator. One cc. of N/1 alcoholic KOH is equivalent to 0.088 grams of ethyl acetate, or 0.1301 grams of amyl] acetate. If, after deducting the sulphuric acid insoluble portion, the saponification number is between 400 and 500, it is probable that amyl acetate is the only other constituent of the oily layer. However, since butyl acetate is now being used in such lacquers, one must not place too much reliance upon the quantitative an- alytical data without actually determining the nature of the ester present. It must be borne in mind that these analytical data are only indictions as to the nature of the materials present. : Should the saponification number, however, be above 500, the presence of esters of lower alcohols is indicated. It will, there- fore, be advisable to fractionate the oily layer to separate these esters. The fraction distilling below 85° C. is collected separ- ately from that distilling above 85° C. That passing over be- low 85° C. is probably composed of ethyl acetate, gasoline, or benzol, or mixtures of these substances. In the absence of ethyl acetate, this fraction should be completely insoluble in cold — concentrated sulphuric acid. The higher boiling fraction is gen- erally composed of amyl or butyl acetate, or mixtures of both, PYROXYLIN LACQUER COATINGS 289 contaminated possibly by some free amy] or butyl alcohol. High boiling hydrocarbons, such as xylene, are also occasionally used. The presence of such hydrocarbons can be best detected by their insolubility in cold concentrated sulphuric acid as outlined above. After fractionating the oily layer, the sulphuric acid insoluble portion of each fraction is determined. Saponify each fraction by the method above. Deduct from the total amount of each fraction the amount of hydrocarbons present before calculating the saponification number. This will give an indication of the nature and quantity of the esters present. Technical ethyl ace- tate, which may be present in the lower boiling fraction, has a saponification number of 600-635. Distillation Range.—Fifty cc. of the dried oily layer are dis- tilled, using a Barrett 200 cc. benzol distillation flask. The temperature range at which each ten per cent by volume distills is noted. Tricresyl Phosphate.—Boil a small portion of the non-volatile residue with sodium hydroxide, then acidify. If tricresy] phos- phate is present, the odor of cresol will be detected and the presence of phosphates may be determined in the solution. Qualitative Tests for Benzol_—Qualitative tests are made by adding one cc. of water and one cc. of mixed acid (nitric and sulphuric) simultaneously to one cc. of the distillate on a watch glass. The characteristic odor of nitrobenzol indicates the presence of benzol. Discussion and Interpretation of Results.—In the total solids determination, the best results are obtained when working with about one gram dry weight of nitrocellulose. For this reason, it is best to take about 5 grams of solution when determining the total solids of a 32-ounce solution, while with a solution con- taining less nitrocotton per gallon, a larger sample is taken. Camphor is usually present in pyroxylin solutions, in which scrap celluloid is used as the base, or in pyroxylin solutions when a high boiling latent solvent is needed, such as in mantle dips. When more than one or two per cent camphor is present, the camphor content should be determined by the refractometer. Wken analyzing a solution which contains scrap celluloid as a base, about 20% of the weight of the nitrocotton, as determined by the total solids determination, should be added to the total solids determination in order to get the percentage of scrap celluloid used. The camphor type of pyroxylin solution is easily 290 EXAMINATION OF PAINTS, VARNISHES AND COLORS recognized after some experience in working with such solu- tions, and it is seldom necessary to use the refractometer in evaluating the pyroxylin solution. In determining whether a low, medium or high viscosity type of soluble cotton was used in the solution, the viscosity de- termination and the nitrocotton content of the solution are taken into consideration. From the weight per gallon determination and the specific gravity of the distilled solvent, the ounces of nitrocotton per gallon of solution may be determined. Soluble cotton ranges in nitrogen content from about 11 to 12.6 per cent, the former being used for celluloid and similar plastics, the latter for smokeless powder. Either of these varie- ties or any in between these two extremes may be met with in present day lacquers. The nitrogen content (between the limits stated) alone is, however, no indication of the suitability of a soluble cotton for any particular purpose, nor does it bear any direct relation to viscosity or solubility in any particular solvent. The saponification determination indicates the presence of any esters. Knowing the range of the distillation of the various esters, the type of ester present in the distillate may be in- dicated from the distillation range of the distillate; and from the saponification value, the percentage of this ester in the distillate is estimated. The acetone content determination indicates the percentage of acetone or ketones present. The sulphuric acid insoluble gives the approximate proportion of benzol or benzine, and possibly toluol or xylol present. The water soluble layer includes all of the denatured alcohol, wood acohol, acetone, or ketone present. Some of the esters and acetone oil have also a small water soluble. From the above assumptions, the ap- proximate composition of the distillate is estimated. The spe- cific gravity of this mixture is calculated, and changes are made in the approximate composition until the specific gravity of the approximate composition compares favorably with the ~ specfic gravity of the distillate. The saponification value and the acetone content are the most accurate of any of the determin- ations made, with the exception of the specific gravity and dis- tillation; and in making changes to obtain the correct specific gravity, it is not possible to make as many changes in the solvent composition of the distillate as it is in the non-solvent composi- tion of the distillate. When changes have been made, so that the specific gravity of the approximate composition agrees with the specific gravity of the distillate, such a solvent mixture is Al ZOL quan SOINUIW Ul SWI] Ogi OZ! O91 OSI OF! OF! OZ! ON OO! O06 o8 oOZ4 09 PYROXYLIN LACQUER COATINGS mace mee In Aol 61) O) ne ‘3 FANE meee | ES S ies Ee Res oe LA te ee SINGATOS UANOOVT AO NOILVUOdVAA AO CAddS 292, EXAMINATION OF PAINTS, VARNISHES AND COLORS made up, and the specific gravity, water soluble, H,SO, insoluble and distillation determinations made on this mixture. If the analysis. of this mixture does not compare favorably with the analysis of the distillate, further changes in the composition are made until the two agree. From the composition of the distillate, and the percentage of nitrocotton, gums, and oils, the composition of the pyroxylin solution may be calculated. Stability Test for Cellulose Nitrate.—The stability of cellulose nitrate is determined by subjecting samples dried at 35-43 C. to various temperatures in the presence of potasium iodide paper. The stability may be measured in terms of the length of time and temperature necessary to discolor the potassium iodide paper. Full details as to this method may be obtained in Scott’s “Standard Methods of Chemical Analysis.” Other val- uable articles on soluble cotton are found in the books entitled Nitro-Cellulose Industry, by Worden; Valuation of Pyroxylin Solvents and Leather Solutions, by J. R. Lorenz, Oct., 1919, Jour. of Am. Leather Chem. Asso.; and Sidney Young’s book on “Dis- tillation Principles,” in which methods for analysis of solvent mixtures are given. Young also gives on page 261 a simple method (modified Messinger method) for determining acetone. Materials to Look For in Pyroxylin Coatings.—There is given below a list of the more important materials that are used in pyroxylin coatings. There have been proposed probably one hundred different plasticizers and stabilizers. Those given be- low, however, are the most commonly used. Solvents: Ethyl, Butyl, and Amyl Acetates, Ethyl Lactate, Acetone Oil, Methyl-Ethyl Ketone, Fusel Oil, Ethyl and Methy] Alcohols, Butyl Alcohol, Acetone, Benzol, Toluol, Gasoline. Plasticizers and Stabilizers: Di-Ethyl Carbonate, Tri-Cresy] Phosphate, Di-Ethyl, Phthalate Urea. Oils: Castor Oil, Linseed Oil, or Rape Seed Oil usually in Blown or Heavy Bodied Form. Resins: Copal, Kauri, Pontianac, Manilla, Shellac, Damar, Ester Gum and Phenol Colophony or Phenol Formaldehyde, Con- densation Resins. Cotton: Usually Regular Soluble Nitrated Cotton. Special Nitrated Cotton soluble in absolute alcohol also used. Pigments: Usually high strength toners, C. P. chemical colors, high strength blacks, and finely ground mineral or chemical col- ors of greatest hiding power. CHAPTER XXXIV. BITUMINOUS PAINTS, VARNISHES, CEMENTS AND SIMILAR MATERIALS During the past five years the use of bituminous substances for cold application as protective coatings has increased con- siderably. This has resulted in an urgent demand for specifica- tions and methods for analyzing and testing them. Heretofore, reliable methods have not been available. The following descrip- tions and methods, as prepared for this volume by E. F. Berger, formerly of the Bureau of Standards, are to be highly recom- mended. Bituminous compositions for cold application can be divided into paints, coatings, varnishes, japans, and plastic cements. Bituminous Paints——Bituminous paints are generally mix- tures of a bituminous material and a volatile solvent which are of brushing consistency and which dry and harden by the evapo- ration of the volatile solvent. They may contain mineral filler and pigment and small amounts of fatty matter. The term, paint, as defined by the A. S. T. M. is, however, misapplied to these materials except in the few instances where pigment is added. Bituminous paints are marketed under various names but the most important kinds can be classed as dampproofing and roof- ing paints. Dampproofing paints are used almost exclusively on masonry and concrete to prevent the absorption or penetra- tion of moisture and are rarely exposed to the weather, being protected in some manner. The two most common kinds are stone backing and plater bond. Stone backing is a solution of a bituminous material in a volatile solvent used for coating all surfaces except the exposed face of cut stone, concrete blocks, etc., to prevent staining, efflorescence, or other discoloration of the exposed face. It is of heavy brushing consistency, invariably dries to a tough, flexible film free from tackiness and which will not chip or flake off in handling. They are composed either of asphaltic or coal tar materials. Plaster bond is a solution of a rather soft bituminous sub- stance in a suitable volatile solvent for coating the inside of 293 294 EXAMINATION OF PAINTS, VARNISHES AND COLORS exterior walls of brick, tile, stone, etc., before plastering to prevent staining, etc. Its value as a means of increasing the bond between the plaster and the wall is a matter of question. Plaster bonds are usually made from asphaltic materials and my contain fatty materials, rosin, rosin oil, aluminum stearate or oleate or other heavy metal soaps. They are of heavier con- sistency than stone backings and dry to soft, flexible films which have a tendency to remain permanently tacky or sticky. Roofing paints are used for painting metal roofs and for re- coating prepared and built-up bituminous roofing. They vary in consistency from those which can be applied with an ordinary paint brush to those which require a stiff bristle dauber or three knot roof brush for application. The former are usually called roofing paints and the latter roof coatings. Roofing paints con- sist of a bituminous material thinned with a solvent and may contain fine mineral filler or pigments. When pigments are present, some drying or fatty oil may be used. Roof coatings are of heavier consistency than roof paints and contain mineral or other filler usually of a fibrous character in the proportion of about 5 to 15 parts per 100 parts of finished paint. Their com- mon trade name is liquid fibrous asbestos roof coating. Roof paints and coatings may be made from either asphaltic or coal tar materials. When using them for prepared or built-up roofing only asphaltic materials should be applied over asphaltic roofings and only coal tar materials over roofings made with coal tar materials. Occasionally paints are encountered which consist of a bitu- minous substance dissolved in carbon bisulphide or carbon tetrachloride. These paints are based on the formula given in the patent of Pearce & Beardsley. Their chief advantage is that they dry rapidly and give relatively thicker dried films than paints of the same consistency made with ordinary solvents. Bituminous Varnishes.—Bituminous varnishes are mixtures of a bituminous material and fatty oil thinned to a suitable con- sistency with a volatile solvent which dry partially by the evapo- ration of the volatile solvent and partially by the oxidation of the fatty oil. The toughness and general characteristics of the film obtained from bituminous varnishes are influenced by the fatty oil present. Bituminous varnishes may be either long or short oil but those most commonly sold are the short oil type with about one part of oil to four of bituminous material. Hard BITUMINOUS PAINTS 295 bituminous materials are generally used and include gilsonite, hard native and residual oil asphalts, glance pitch, manjak, wurtzelite pitch, grahamite, and fatty acid pitches. Bituminous Japans.—Bituminous japans are mixtures of bitu- minous materials with or without fatty oil and resins and vola- tile solvent the drying and hardening of which is brought about by baking. The cheaper grades of japan usually consist of a bituminous substance dissolved in a solvent, the better grades are mixtures of a bituminous substance with fatty acid pitch, drying oils, and resins, with or without small amounts of pig- ment. Most black insulating varnishes and Brunswick Black are of this character. Bituminous Plastic Cements.—Bituminous plastic cements are mixtures of trowelling consistency of bituminous materials with or without fatty oil and volatile solvent and containing about 15 to 40 parts of filler, generally of a fibrous character, per 100 parts of cement. They are applied in thick layers and usually dry to tough coatings which remain plastic for long periods. They are made either from asphaltic or coal tar materials and the same precautions should be taken in their use on bituminous roofing as with roof paints and coatings. Pine tar, pine tar oil, and hard wood tar are sometimes used to improve spreading quality and to modify the odor of coal tar materials. CONSTITUENTS OF BITUMINOUS PAINTS, VARNISHES. CEMENTS, ETc. The following materials are generally used in these products, although any material entering into the manufacture of oil paints, varnishes, etc., is likely to be used. (1) Bituminous Materials. Petroleum Asphalts Glance Pitch Trinidad Asphalt Wurtzelite Pitch Bermudez Asphalt Coal Tar Pitch Gilsonite Water Gas Tar Pitch Grahamite Pine Tar and Wood Pitches Manjak Fatty Acid Pitches (2) Fatty and Resinous Materials. Linseed Oil Castor Oil China Wood Oil Rosin Cottonseed Oil Fossil Resins Rosin Oil (3) Driers. Any drier used in oil paints and varnishes. 296 EXAMINATION OF PAINTS, VARNISHES AND COLORS (4) Thinners. Petroleum Distillates Pine Oil and Pine Tar Oil Coal Tar Distillates Carbon Bisulphide Turpentine Carbon Tetrachloride (5) Fillers and Pigments. Asbestos Slate Dust Asbestine Silica Clay Rag Fibers Portland Cement Jute Fibers Limestone Dust Paper Pulp Gypsum METHODS OF ANALYSIS AND TEST (A) Volatile and Nonvolatile: (1) Materials without filler—Heat a 1.5 to 2 gram sample in a tared metal dish at 105° to 110° C. for three hours. The loss in weight is calculated as volatile. (2) Materials with filler—Heat a 3 to 5 gram sample spread out to a thin layer in a tared metal dish at 105° to 110° C. for seven hours. The loss in weight is calculated as volatile. (B) Separation and Examination of Thinner: (1) Low boiling thinners.—Distill 100 grams of the sample with steam at a temperature of 130° C., collecting the distillate in a separatory funnel. Stop the distillation when 300 cc. of water has distilled. When the distillate has separated into two distinct layers, draw off the water, and examine the distillate for refractive index, specific gravity, soluble in 38 N. sulphuric acid, dimethyl sulphate, or by any other tests necessary for its identification. If no pigment or filler is present the residue in the flask may be dried and used for a testing as in para- graph (D). (2) High boiling thinners.—Distill 100 grams of the sample in a 200 ec. Engler distilling flask at the rate of about one drop per second, avoiding overheating, which may crack the bitumi- nous material. Collect fractions up to 170° C., and 170° to 300° C., at which point the distillation is stopped. In most cases the thinner will all have distilled at a point below 300° C. and the distillation should be stopped when this occurs. The dis- tillates are examined as in (1). The residue in the flask is al- lowed to cool until vapors are no longer evolved, when it is poured out into a suitable container and, if no pigments are present, preserved for further testing as in paragraph (D). BITUMINOUS PAINTS 297 (C) Fillers, pigments and free Carbon: Separate the fillers, pigments, and free carbon from the vehicle by any of the following methods: (1) Weigh accurately about 10 grams of the sample into a centrifuge tube. Add about 25 cc. of benzol and stir so as to break up the sample, then add about 25 cc. more solvent and centrifuge until well settled. Decant the supernatant liquid and repeat the extraction twice with 50 cc. portions of benzol and then with a mixture of equal parts of benzol and carbon tetra- chloride until the supernatant liquid is colorless. Dry residue in tube at 105° to 110° C. for one hour and weigh. Preserve extracts for further examination of vehicle. The insoluble resi- due contains the pigment and fillers, and mineral matter occur- ring naturally in the bituminous materials (7. e., Trinidad and Bermudez asphalts) and free carbon from coal tar pitches. (2) Weigh accurately about 5 grams of the sample into a small beaker, add 25 cc. of carbon bisulphide or carbon tetra- chloride or benzol (if an examination of the vehicle is to be made), break up the sample by stirring and allow to stand for 15 minutes. Filter through a weighed Gooch crucible, prepared with a medium thick mat of asbestos, or an Alundum crucible using suction if necessary to aid filtration. Wash the residue in the crucible until the washings are colorless, dry in air at room temperature until the odor of carbon bisulphide has almost disappeared, and then for 1 hour at 105° to 110° C. Cool, weigh, and calculate percentage of insoluble material. In this method if Trinidad asphalt is present some of the fine mineral matter may pass through into the extract. This can be determined by evaporating the extract, burning off the bituminous matter, and weighing the ash obtained. (3) Weigh the sample into a paper thimble and extract in a Soxhlet or other suitable extractor. Examination of “insoluble matter.—The insoluble matter (filler, pigment, free carbon) is examined as in the case of oil paints, except as follows: (1) Fibrous Filler—Examine microscopically for mineral wool, rag fibers, jute, paper pulp and asbestos. (2) Free carbon from coal tar compositions, in presence of mineral matter containing water of crystallization—When the filler is asbestos, this method gives satisfactory results. Extract about 5 grams of the sample as in “C” and weigh the residue of carbon and asbestos. Now burn off the carbon and weigh. 298 EXAMINATION OF PAINTS, VARNISHES AND COLORS Increase this weight by 14 per cent to compensate for water of crystallization driven off from the asbestos. Calculate per- centages of free carbon and asbestos. (3) For mixtures of free carbon with asbestos and clay.—The following method has been suggested but has not as yet been thoroughly investigated: Extract about 5 grams of the sample as in “C” and weigh the residue. Ignite the residue in a crucible for seven minutes in a current of dry carbon dioxide (using a Rose crucible cover) with a flame about 20 cm. high, or in a platinum crucible with a tightly fitting cover in a muffle at between 950° and 975° C. for seven minutes. Cool and weigh. The loss in weight is water of crystallization from the filler. Now burn off the carbon, cool, weigh and calculate the loss in weight as free carbon. (D) Nonvolatile Vehicle: Saponifiable or fatty matter may be determined by either of the following methods. If no pigment or filler is present, the original material may be taken. If pigment or filler is present, it should be removed as in (C) and the extract containing the nonvolatile vehicle or base should be evaporated to a small volume over a steam bath. (1) The following method is essentially that given in “Asphalts and Allied Substances”—1920, by Herbert Abraham. Weigh 5 grams of the original material (or take the evapor- ated extract from 7.5 grams of material obtained as in (C)) and dissolve in 50 cc. of benzol using heat, if necessary, to aid solu- tion. Add 5 cc. of dilute nitric acid (1:1) and boil under a reflux condenser for one-half hour to decompose any metallic soaps (7. e., driers, etc.). Add 150 cc. of water, boil under a reflux condenser, then transfer to a separatory funnel, draw off the aqueous layer, and repeat extractions with water until all metals are removed. To the benzol solution add 30 cc. of a saponifying liquid made by dissolving 100 grams of anhydrous potassium hydroxide in 500 cc. of 95 per cent ethyl alcohol and diluting to 1,000 ec. with 90 per cent benzol, and boil under a reflux condenser from one- half to one hour. Pour the mixture while still warm into a separatory funnel containing 150 cc. of boiling water and 25 ec. of a 10 per cent solution of potassium chloride. Add 250 ce. of benzol, shake vigorously, and allow the funnel to rest quietly in a warm place BITUMINOUS PAINTS ZA until the solvent separates. (If an emulsion forms which re- fuses to separate on standing, add 200 cc. of benzol and 100 cc. of 95 per cent ethyl alcohol and stand in a warm place over night.) Usually three layers are obtained. Draw off the aque- ous solution of the soaps as completely as possible and decant the benzol layer leaving the intermediate layer in the funnel. Extract the aqueous soap solution with 200 cc. portions of benzol until the benzol extract is colorless. Combine the benzol extracts with the layer obtained from the funnel and extract with 100 cc. portions of 50 per cent ethyl alcohol. Add the alcohol extracts of the benzol layer to the intermediate layer in the separatory funnel and extract with benzol until the benzol extracts are colorless. Combine the benzol extracts, evaporate, dry at 105° C., and weigh as unsaponifiable. Combine the aqueous soap and alcohol extracts and acidify with dilute hydrochloric acid, warm, and extract with benzol. Evaporate the benzol extract, dry at 100° C. and weigh as saponifiable. (2) The following method (B. S. Circular 104, Recommended Specifications for Asphalt Varnish) is more rapid and avoids troublesome emulsions. It has not been tried on compositions containing very soft petroleum asphalts, Trinidad and Bermudez asphalt, or resins, but it gives satisfactory results on mixtures of fatty oil with hard petroleum asphalts, gilsonite, wurtzelite pitch, and manjak. Weigh about 5 grams of the material into a wide-mouthed flask (or take the evaporated extract from 7.5 grams of ma- terial obtained as in (C)), add 50 cc. of benzol and 5 grams of silica sand, and heat under a reflux condenser on a steam bath until the material is entirely dissolved. Add 25 cc. of a half normal alcoholic caustic potash solution, and 25 cc. of de- natured alcohol, and continue boiling under the reflux condenser for one hour. Remove the condenser and evaporate the solution to dryness. . Add to the residue in the flask 50 cc. of distilled water and heat until the residue is disintegrated. Filter the water solution of the soaps. Repeat this operation with 25 cc. portions of water until the residue is completely disintegrated and the wash water is clear and colorless. Combine the filtrates (the soap solution and washings), 300 EXAMINATION OF PAINTS, VARNISHES AND COLORS acidify with hydrochloric acid, and heat until the fatty acids and any emulsified asphalt separate and rise to the top, and the water below is clear. Cool, transfer to a separatory funnel, and extract three times with 50 cc. portions of ether. Combine the ether extracts and wash with water until free from acid. Filter the ether extracts through paper into a beaker and wash the residue on the paper with ether until the washing runs through colorless. Evaporate the ether solutions to dryness. Add 15 cc. of 95 per cent ethyl alcohol to the residue in the beaker and warm on the steam bath. Cool to room temperature and filter through paper into a tared flask or dish. Repeat this operation with 10 cc. portions of 95 per cent ethyl alcohol until the alcohol remains colorless. Finally wash the residue on the paper with 95 per cent ethyl alcohol until the washings run through colorless. Evaporate to dryness on a steam bath and heat for an hour in an oven at 105° C. (221° F.). Cool and weigh. From the weight of the residue in the flask and the weight of the original sample calculate the percentage of fatty matter. (Sometimes the residue obtained after saponification and the evaporation of the benzol and alcohol from the saponifying mix- ture is not completely disintegrated by boiling with water. In that case, extract with water until nothing further dissolves and then dry. Dissolve in benzol, using heat if necessary, and wash the benzol solution several times with water. Heat the washings until the odor of benzol has disappeared and add to the soap solution before acidifying.) Examination of Saponifiable-——The saponifiable obtained as above may be separated into fatty and resin acids by method of E. W. Boughton, B. S. Tech. Paper No. 65, and may be tested for rosin and fatty acid pitch (Test 37b) “Asphalt and Allied Substances” by Herbert Abraham—1920. Examination of Unsaponifiable—The unsaponifiable should be tested for melting point and fixed carbon. In case the sample contains no pigment, filler, or saponifiable these tests should be made on the nonvolatile obtained as in (A) or in the residue from distillation as in (B). For asphaltic materials determine the melting point by the “Standard Method of Test for Softening Point of Bituminous Materials Other Than Tar Products”—D. 36-21, A. S. T. M. Standards, 1921, page 739—(Ring and Ball Method). Se Se a Se i 7, a or te eee ee BITUMINOUS PAINTS 301 For tar products determine the melting point by the “Standard Method of Test for Softening Point of Tar Products” —D. 61-20, A. S. T. M. Standards, 1921, page 743—(Cube in Water Method). For tar products having melting points above 77° C. (170.6° F.) use Cube Method in Air—‘Asphalts and Allied Sub- stances,” by Herbert Abraham—1920, page 516. Determine fixed carbon on asphaltic materials by method given in Journal of American Chemical Society, 1899, Vol. 21, page 1116, or “Fixed Carbon in Bituminous Materials, Its Deter- mination and Value in Specifications,” by L. Kirschbaum, Eng. Contr. 39, 172 (1913). The fixed carbon obtained from common asphaltic materials is as follows. EEA ge Uo gi ES 0) sa a nr 12 to 14 per cent CSE UIVES cai ® ge UGS ole 2 | A ERR pean teaes ee ne ete 9% to 18 per cent I Feb aS RLS a) VE Eo en a 15 to 22 per cent Ss CNC eels on citlcla te aeatinccettenee anti 13 to 16 per cent GPa hg fe 0 cep c) aa bay ane eae ee ee eR Renee ee 10 to 18 per cent Toya Qi 5 2 iia Dn nar See ema oD 14 to 20 per cent OVE Fie oS NC BA 0 9 gee oem 15 to 25 per cent ETE LESS yyy oo RR IR eee os ee cso 30 to 55 per cent (E) Tests for the Differentiation of Asphalt and Coal Tar Pitch: Owing to the prejudice of the buying public against coal tar paints and cements, brought about by the use of materials of poor quality made from coal tar materials, and the fact that some dealers in asphaltic materials are using these failures as selling arguments, the analyst is often called upon to prove the presence of coal tar materials other than thinners in asphaltic products and vice versa. The following tests are useful for this purpose: (1) Color of solution of nonvolatile in benzol.—Coal tar mate- rials usually give a solution with a yellowish or greenish brown fluorescence. Asphaltic materials give a brown solution with- out fluorescence. The presence of oily constituents in some asphalts may at times give a fluorescence that might be mistaken for that obtained from coal tar materials. Wood pitches may also give a slight fluorescence. (2) Free Carbon.—The presence of free carbon indicates the presence of coal tar or coal tar pitch. (3) Distillation Test.—Weigh into an iron or copper distill- ing retort 100 grams of the material under examination. Heat 302 EXAMINATION OF PAINTS, VARNISHES AND COLORS very slowly until distillation begins and then distill off the thinner at the rate of about one drop a second. Usually around 200° C. a point will be reached where the distillate will stop coming over and the temperature will tend to drop. At this point the thinner is usually all removed. Change the receiver and continue distillation so as to crack or destructively distill the bituminous material until the temperature reaches 360° C. Note the character of the distillate. Asphaltic materials usually give liquid distillates of a brown or reddish brown color. Coal tar materials usually give solid distillates of orange or reddish color or liquid distillates from which crystals tend to separate. The character of distillates from mixtures of the two materials varies. The presence of fatty oil is recognized by the odor of | acrolein. . The following tests are made on the cracked distillate: (a) Specific Gravity of Cracked Distillate at 25° C.—Cracked distillate of asphaltic materials—0.74 to 0.87. Coal tar mate- rials—0.98 to 1.07. Cracked fatty oil lowers the specific gravity. (b) Sulphonation with 38 N H,SO,. | The following amounts of residue are usually obtained: Coal Tar Materials... 2 = 0 to 10 per cent Water *Gas =TarPitth. =.) 2 ee 0 to 15 per cent Asphaltic Materials cc...) min. 80 per cent Wood Tar’ Pitches. 2 0 to 5 per cent Fatty Acid Pitches and Fatty Oils... 0 to 5 per cent (c) Soluble in Dimethyl Sulphate.—This test may be used but with caution owing to its unreliability in the case of small amounts of either material. The distillates from coal tar materials are usually completely Soluble in dimethyl sulphate, while those from asphaltic mate- rials are about 85 per cent insoluble. (d) Anthraquinone Test.—Melt. the distillate if solid or if it contains solid particles and take about 5 cc. for examination. Cool and add 10 ce. of absolute ethyl alcohol and allow to stand until the solids separate. Decant the liquid and dry the solids. Dissolve in 45 cc. of glacial acetic acid and boil under a reflux condenser for 2 hours. Add drop by drop to the boiling solution, a solution of 15 grams of anhydrous chromic acid dissolved in 10 cc. of glacial acetic acid and 10 ce. of water. Boil under reflux condenser for two hours, allow to cool and add 400 ee. of cold water, and filter off the precipitated anthraquinone. The crystals of anthraquinone are washed with hot water, then a hot ee ee ee BITUMINOUS PAINTS 303 1 per cent solution of NaOH, and then with hot water. The residue is dried and weighed and the percentage of anthracene ealeulated. From 0:25 to 0.75 per cent of anthracene is found in coal tars, and correspondingly larger amounts in coal tar pitches. A qualitative test to identify the crystals consists in boiling them with zinc dust and caustic soda solution, whereupon an intense red colored solution (Alizarin) is obtained, which de- colorizes in contact with the air. This test will serve to identify coal tar materials in asphalt compositions. (4) Diazo Reaction—devised by E. Graefe—‘Distinction be- tween Lignite Pitches and Other Pitches,’ Chem. Zeit. 30—298 — (1906), serves to distinguish those bituminous substances con- taining phenolic bodies from those not containing them, as as- phalts. It should be made on the original bituminous sub- stance. In the absence of coal tar materials, this test will estab- lish the presence of wood tars and pitches in asphaltic mixtures especially with a positive Liebermann Storch reaction. (F) Physical Tests: While the foregoing tests will give some information about the composition and quality of these materials, and their suit- ability for the purpose intended, the following physical tests are at times more valuable for determining the adaptability of a material for a particular use. (1) Time of drying or setting on prepared roofing, metal, concrete, etc. (2) Heat test at 140° F. (3) Exposure test outdoors at angle of 45° to the south for periods varying from one week to a month. (4) Baking test. (5) Toughness. (6) Working Properties. (7) Resistance to water, lubricating oil, and acids. (8) Heat test on smoke stack paint at 410° F. (9) Adhesion tests. CHAPTER XXXV. ANALYSIS OF WHITE PAINT PIGMENTS The vehicle having been extracted from the paint under ex- amination, by the previously outlined methods, see pages 213 to 214, the pigment is left ready for analysis. The pigment can be readily classified under one of the following heads by its color, thus shortening any preliminary examination. Many of the colors have a white base which necessitates a determina- tion of both the colored portion of the pigment and of any white base which may have been used. The general analysis of colored pigments is carried out accord- ing to the specific method outlined for the individual colored, pigments, together with the methods for a composite white paint, provided a qualitative examination does not directly reveal the identity of the pigment. The pigments used in the manufacture of paints are classified as follows, in certain instances the trade names being given by which the particular pigments are shown. WHITE PIGMENTS Lead Pigments Corroded White Lead—Basic Carbonate of Lead. Old Dutch Process White Lead. Quick Process White Lead. Mild Process White Lead. Carter Lead. Sublimed White Lead—Basic Sulphate of Lead—Basic Sul- phate-White Lead. Zine Lead. Leaded Zinc. Zinc Pigments Zine Oxide—Zine White. Lithopone — Alabalith — Ponolith — Beckton White—Charlton White—Orr’s White. Other Opaque White Pigments : Titanium Oxide—Titanox. a Antimony Oxide. Silica Pigments Silica—Silex, Asbestine—Taleose. China Clay—Kaolin—Tolamite. i 304 ANALYSIS OF WHITE PAINT PIGMENTS 305 Calcium Pigments Whiting—Paris White—Chalk—Alba Whiting—Spanish White. Gypsum—Plaster of Paris—Terra Alba—Agalite. Barium Pigments Barytes—Barite—Blanc Fixe—Barium Sulphate. Barium Carbonate—Witherite. RED AND BROWN PIGMENTS Red Lead—Orange Mineral. Vermillions—Para Reds. Ochres—Tuscan Red—Indian Red—Venetian Red. Umbers—Siennas. BLUE PIGMENTS Sublimed Blue Lead. Ultramarine Blue. American Blue—Prussian Blue—Antwerp Blue—Chinese Blue. YELLOW AND ORANGE PIGMENTS Chrome Yellow—Lemon Yellow—Medium Chrome Yellow. American Vermillion—Orange Chrome—Basic Lead Chromate. Orange Mineral. GREEN PIGMENTS Chrome Green. Chromium Oxide. Green Earth. BLACK PIGMENTS Graphite. Carbon Black—Bone Black—Lamp Black—Drop Black—lIvory Black—Mineral Black. Willow Charcoal. Black Oxide of Iron. CORRODED WHITE LEAD Basic Carbonate of Lead—Old Dutch Process White Lead— Quick Process White Lead—Mild Process White Lead Corroded white lead contains approximately 80 per cent metallic lead and 20 per cent carbonic acid and combined water with traces sometimes of silver, antimony and other metals. This material should approach the composition indicated by the formula 2PbCO,.Pb (OH).. Total Lead (Gravimetric) —Dissolve 1 gram in 20 cc. of HNO, (1:1) in a covered beaker, heating till all CO, is expelled; wash off cover, add 20 cc. of H,SO, (1:1) and evaporate to fumes of SO,, cool, add about 150 cc. of water and 150 cc. of ethyl alcohol; let stand in cold water one hour, filter on a Gooch 306 EXAMINATION OF PAINTS, VARNISHES AND COLORS crucible, wash with 95 per cent ethyl alcohol, dry at 110° C., and weigh the PbSO,. Calculate to PbO or to basic carbonate.* Instead of determining the lead as sulphate, the sample may be dissolved by boiling with acetic acid; then dilute to about 200 ee. with water, make alkaline with NH,OH, then acid with acetic — acid, heat to boiling and add 10 to 15 cc. of a 10 per cent solution of potassium dichromate; heat till the yellow precipitate assumes an orange color. Let settle and filter on a Gooch crucible, wash- ing by decantation with hot water till the washings are color- less, finally transferring all of the precipitate. Then wash with 95 per cent ethyl alcohol and then ether; dry at 110° C. and weigh PbCrO,. (Any insoluble matter should be filtered out before preciptating the lead.) Factor .6375 gives lead content. Total Lead (Volumetric).—Dissolve 0.5 gram of sample in 20 cc. of (1:1) hydrochloric acid and 2 grams sodium chloride, boil till solution is effected, cool, dilute to 40 ec. and neutralize with ammonium hydroxide. Add acetic acid until distinctly acid, dilute to 200 ec. with hot water, boil and titrate with am- monium molybdate as follows: Dissolve 4.25 grams of ammonium molybdate in water and make up to one liter. To standardize this solution dissolve about 0.2 gram of pure lead foil in nitric acid (pure PbO or PbSO, may also be used), evaporate nearly to dryness, add 30 cc. of water, then 5 cc. H,SO, (sp. gr. 1.84), cool, and filter. Drop filter with PbSO, into a flask, add 10 cc. concentrated HCl, boil till completely disintegrated, add 15 cc. of HCl, and 25 cc. of ammonium acetate slightly acidified with acetic acid. Acidify with acetic acid, dilute to 200 cc..with hot water and boil. Titrate, using an outside indicator of one part of tannic acid in 300 parts of water. | | It should be noted that when calcium is present, it forms a more or less insoluble molybdate, and results are apt to be high. With samples containing less than 10 per cent of lead, the lead should be precipitated as PbSO,, filtered, redissolved and titrated as in the process of standardizing. Carbon Dioxide.—Determine by evolution with dilute hydro- chloric acid absorbing in soda-lime or KOH solution. Calcu- late CO, to PbCO., subtract PbO equivalent from total PbO and calculate residual PbO to Pb(OH).. * This method of weighing lead sulphate is not accurate in the presence of calcium componds. ANALYSIS OF WHITE PAINT PIGMENTS 307 A more simple and efficacious method of determining the car- bonic acid content will be found in the following method. The method can be used in such cases where the substances to be analyzed evolve gases other than carbon dioxide; that is, hy- drogen sulphide, sulphur dioxide, or organic matter. The appa- ratus used is shown in Fig. 103. A weighed sample of the sub- stance is introduced into the Erlenmeyer flask (A). Into flask FIGuRE 108 Carbon Dioxide Apparatus (B) is placed a 10 per cent solution of barium chloride, more than sufficient to hold the carbon dioxide evolved, and 20 cc. of concentrated ammonium hydroxide free from carbou dioxide. If sulphides are present, it is sometimes advisable to pass the lib- erated gas first through a few c.c. of strong potassium permanga- nate. The flask (B) is warmed until completely filled with am- monia fumes. Flask (D) is a safety bottle containing the same solution as flask (B). Only in rare cases will any trace of the carbon dioxide be noticed in the safety flask. After flask (B) is completely filled with ammonia vapor, make all connections and 308 EXAMINATION OF PAINTS, VARNISHES AND COLORS allow the hydrochloric acid to drop slowly from the separatory funnel into the decomposition flask (A). When effervescence has ceased, heat the contents of the flask until filled with steam. The delivery tubes and sides of the precipitating flask are then washed with boiling water, the flask is filled to the neck, stop- pered, and the precipitated barium carbonate allowed to settle. Wash thoroughly by decantation, each time stoppering the flask to prevent any error from the carbon dioxide present in the air, and determine either gravimetrically, by conversion into barium sulphate, or volumetrically, by dissolving in standard hydro- chloric acid and titrating the excess of acid used with standard potassium hydroxide. Calculate the barium found to carbonate and the amount of carbon dioxide from the found carbonate. The entire operation may be hastened by conducting a brisk current of air free from carbon dioxide through the entire apparatus. Two rapid volumetric methods for the determination of car- bonic acid contents are described in detail by Leon T. Bonser in the Journal of Industrial and Chemical Engineering, March, 1912, page 203, and by H. W. Brubaker in the same journal, August, 1912. Acetic Acid.*—Place 18 grams of the pigment in a 500 cc. flask, add 40 cc. of syrupy phosphoric acid, 18 grams of zinc dust and 50 cc. of water. Connect to a straight Liebig con- denser, apply heat and distill down to a small bulk. Then pass steam into the flask until it becomes about half full of con- densed water, shut off the steam and distill down to a small bulk—this operation being conducted twice. To the total dis- tillate which was collected in a larger flask add 1 cc. of syrupy phosphoric acid, connect to a Liebig condenser, using a spray trap, and distill to a small volume—about 20 cc. Pass steam through till about 200 cc. of water condenses in the distillation flask, shut off steam and continue the distillation. These opera- tions of direct and steam distillations are conducted until 10 cc. of the distillate require only 1 drop of N/10 alkali to give a change in the presence of phenolphthalein. Then titrate the total distillate with N/10 sodium hydroxide and phenolphthalein and calculate the total acidity as acetic acid. It will be found convenient to titrate each 200 cc. portion of the distillate as col- lected. Metallic Lead.*—Weigh 50 grams of the sample into a 400 * Thompson’s Method, Jour. Soc. Chem. Ind., 24, 487, 1905. ANALYSIS OF WHITE PAINT PIGMENTS 309 ec. beaker, add a little water and add slowly 60 cc. of 40 per cent acetic acid and after effervescence has ceased, boil on hot plate. Fill the beaker with water, let settle, and decant the clear solution. To the residue add 100 cc. of a mixture of 360 ce. of strong NH,OH, 1080 cc. of water, 2160 cc. of 80 per cent acetic acid, and boil until all solution is complete. Fill the beaker with water, let settle and decant the clear solution. Col- lect residue on a watch-glass, floating off everything but metallic lead. Dry and weigh. Result x 2—percentage of metallic lead in sample. LEAD HYDRATE The following method of A. N. Finn (unpublished) gives total basicity of a pure white lead: Place 2 grams of pigment in an evolution flask, add a little CO.-free water, connect with a _ separatory funnel and condenser (Knorr type), add through the funnel, finally washing down, 100 cc. of N/4 nitric acid, boil and absorb the CO, in a soda lime tube in the usual manner (having H,SO, and CaCl, drying tubes in train) and weigh. To the solution in the evolution flask, add about 20 cc. of neu- tral sodium sulphate solution and titrate with N/4 sodium hydroxide solution (carbonate-free), using phenolphthalein. CO, is calculated to PbCO,. The amount of N/4 acid corre- sponding to the CO, is calculated and deducted from the total amount of N/4 acid neutralized by the sample and the differ- ence calculated to combined H,O, from which Pb(OH), is com- puted. Electrolytic Deposition of Lead—lIn samples of pigment which contain less than 5 per cent of lead, the lead content may be determined electrolytically in a very rapid manner by follow- ing the procedure as outlined by Smith* in his Electro-Analysis, as follows: Twenty cc. of concentrated nitric acid were added to a solution of lead nitrate, giving a total volume of about 125 ce. and acted upon with a current of N.D..,,,—=10 amperes and 4.5 volts. The rotating electrode (cathode) performed 600 revolutions per minute. The deposits had a uniform, velvety black color. There was no tendency on the part of the deposit to scale off, though more than a gram of the dioxide was preci- pitated. The time varied from ten to fifteen minutes. * Electro-Analysis, Smith: P. Blakiston’s Sons & Co. 310 EXAMINATION OF PAINTS, VARNISHES AND COLORS A platinum dish with sand blasted inner surface was used as an anode. By using a current of N.D.,,,.=11 amperes and 4 volts upon a solution of lead nitrate containing 0.4996 gram of lead or 0.5787 gram of dioxide, the rate of precipitation was found to be: Ins oI Ues a2 i eee ees 0.4940 gram lead dioxide Dn. BO sm Ti tess 2 a co ae ee 0.5708 gram lead dioxide In: 1d: mintites rar oe ee 0.5747 gram lead dioxide in ?20-sminwtes: ate, es 0.5770 gram lead dioxide In 26 ,,ariniu teaser ees ee plone 0.5787 gram lead dioxide In BON ates. ce a oe ee 0.5789 gram lead dioxide “The maximum time period for a quarter of a gram of metal is twenty-five minutes.” See also Interdepartmental Specifica- tions in back of volume. 7 BASIC SULPHATE OF LEAD (Sublimed White Lead) * * Schaeffer Method. : 2 : ; An average approximate analysis of sublimed white lead as commercially placed upon the market should show about 78.5 per cent of lead sulphate, 16 per cent of lead one and 5. 5 per @ cent of zine oxide. ANALYSIS Total Sulphates Mix 0.5 gram of the sample with 3 grams of sodium car- bonate in a beaker. Treat the mixture with 30 cc. of water and boil gently for ten minutes. Allow to stand for four hours. Dilute the contents of the beaker with hot water, filter off the residue and wash until the filtrate is about 200 ec. in volume. Reject the residue. By this reaction all the lead sulphate is — changed to carbonate, the sulphate being transposed into sodium sulphate, which is found in the filtrate. Acidulate the filtrate with hydrochloric acid and add an excess af about 2 cc. of the acid. Boil, and add a slight excess of barium chloride solution (12 ec. of an 8 per cent solution). When the precipitate has well settled, 4 hours or preferably over night, filter on an ashless filter, wash, ignite and weigh as BaSO,. Calculate the BaSO, to PbSO, by using the factor 2.6, when a half gram sample is used. Weight of BaSO, x 1.3 equals weight PbSO,. On 0.5 gram sample factor BaSO, to PbSO,—2.6. ANALYSIS OF WHITE PAINT PIGMENTS Bt TOTAL LEAD Molybdate Method.t—Dissolve 1 gram of the sample in 100 cc. of an acid ammonium acetate solution made up as follows: i See TEE AEL YS) ARE 4 (0 A na Lecce: Concentrated ammonium hydroxide... 95 cc. ria catnnn lb ens Snccspecsesbaguedeubncbseseovingtvennnsoariontc 100 cc. Add this solution hot and dilute with about 50 ce. of water. Boil until dissolved. Dilute to 200 cc. and titrate with standard ammonium molyb- date solution, spotting out on a freshly prepared solution of tannic acid. Ammonium molybdate is a slightly variable salt, but a solu- tion containing 8.67 grams per liter usually gives a standard solution: 1 ec. equals 0.01 gram Pb. Standardize against pure PbO. Weigh .5 gram pure litharge add 30 cc. hot water and 32 cc. (80%) acetic acid. Heat to boiling, and when all litharge is in solution add 27 cc. concen- trated ammonium hydroxide. Dilute to 200 cc. with hot water, boil and titrate, using outside indicator of 1 part of tannic acid in 300 parts of water. . Bichromate Method.—Treat the sample as above described until dissolved. If the solution is not quite clear, filter. Add to the filtrate an excess of neutral potassium bichromate solu- tion. Boil until the lead chromate has become an orange yellow color and stand in a warm place until the precipitate has settled. Filter on a Gooch crucible, wash thoroughly, ignite below a red heat and weigh as PbCrO,. The PbCrO, may be estimated volumetrically by titrating the chromic acid present. For this method, dissolve the lead chro- mate from off the filter with hydrochloric acid. Wash well and determine the chromic acid present with a standard solution of ferrous ammonium sulphate, using a dilute solution of potas- sium ferricyanide as an outside indicator. The ferrous ammo- nium sulphate is made up of such strength that 1 cc. will equal exactly 0.00202 gram Fe. Dissolve 14.19 grams C. P. ferrous ammonium sulphate in one liter of distilled water. A small scrap of aluminum foil in the bottle prevents oxidation. For a one + Modification of Low’s Method. Technical Methods of Ore Analysis, Low, p. 149. 312 EXAMINATION OF PAINTS, VARNISHES AND COLORS gram sample dividing the number of cc. of ferrous ammonium sulphate used by 4 gives the per cent of total lead. Deduct the lead found as lead sulphate from the total lead and calculate the residual lead to PbO. TOTAL ZINC* Boil one gram of the sample in a beaker with the following solution: A) (| i MMMM 30 cc. Ammonium “chloride... 4 grams Concentrated hydrochloric Aid... a ccccccscascesssstensteeon 6 cc If the sample is not quite dissolved the result is not affected, as the residue is lead sulphate or precipitated lead chloride. Dilute to 200 cc. with hot water, add 2 ce. of a saturated sodium thiosulphate solution and titrate-with a standard solution of potassium ferrocyanide, spotting out on a 5 per cent solution of uranium nitrate. Calculate the zinc to zine oxide by multi- plying by the factor 1.245. TOTAL IRON OXIDE Determine this constituent as outlined under the Analysis of Litharge. THE LEAD CONTENTS IN SUBLIMED WHITE LEAD—A CALCULATION} The composition of sublimed white lead, the basic sulphate of lead, has become a most important factor to users of this pigment. Both among rubber manufacturers and producers of paints, it is being found essential that the contents of lead oxide and lead sulphate be known, so that advantage may be fully taken of its characteristic properties. This control neces- sitates an analysis of the compound in the laboratory. In analyzing sublimed white lead by the usual method, it is found that the percentage composition can be determined only by an analysis entailing lengthy manipulation, in which the content of lead oxide is directly dependent upon the accuracy of the other determinations, owing to the necessity of estimating its percentage by a calculation based upon the percentage of the * Low’s Technical Methods of Ore Analysis. + J. Ind. & Eng. Chem., 6, 200 (1914). ANALYSIS OF WHITE PAINT PIGMENTS 313 other constituents present. The steps in the procedure must therefore be closely watched for slight inaccuracies at all times. As is well known, the average composition of sublimed white lead is given as follows: Mm arctrem er es 78.5 RM Meme 8 16.0 er are CM ee 5.5 That its composition varies only slightly from the above analysis during a long period of time, is shown by its comparison with an average of the entire output of the Eagle-Picher Lead Company extending over five months’ time an average embrac- ing 270 total analyses. This average shows the composition to be: DG, UNCLES SINS ere anne 76.68 eqn ere eae ee: fo ee yo P25 Peer CC 5.19 99.70 A slightly higher lead oxide and zinc oxide content and a cor- respondingly lower lead sulphate content is found, than in the usually stated formula. It shows, however, only slight variation. The average total percentage, consisting of lead sulphate, lead oxide, and zinc oxide, was found to be 99.70 per cent. The remaining 0.3 of a per cent is only rarely determined, and when actually sought is found to consist of moisture, occluded gas and ash. A definite ratio exists between the total lead content and the lead sulphate and lead oxide contents, and advantage may be taken of this relation for a rapid and accurate deter- mination of the lead constituents in sublimed white lead. In order to arrive at the short method for the anaysis which is based upon a direct calculation of the lead and zinc contents, it is necessary that only the percentage of zinc and lead be deter- mined by the methods already described. Using the percentages of zine oxide and total lead, together with the average total, 99.70 per cent, determined from the large number of analyses, the contents of lead oxide and lead sulphate are readily estimated by the following calculation: 314 EXAMINATION OF PAINTS, VARNISHES AND COLORS Total percentage of lead compounds present equals 99.70 per cent (average) = total percentage found of ZnO, PbO and PbSO, less percentage ZnO. Total percentage of lead compounds present equals 99.70 per cent (average total) minus percentage ZnO. Atomic weight lead... ....<.5... 2s) oa 207.1 Molecular weight lead oxide........., 5. sae 223.1 Molecular weight lead sulphate..................... 303.1 As a hypothetical case, we can assume the presence of a 4.70 per cent ZnO and | 69.00 per cent metallic lead. (1) ——————— X % Pb found } — % Pb constituents At. wt. Pb. a ears Mol. wt. PbSO, — mol. wt. PbO Mol. wt. PbO Mol. wt. PbO Ss ate oe en ) — % Pb constituents At. wt. Pb = % PbSOQ, present (2) Mol. wt. PbO — Mol. wt. PbSO, Mol. wt. PbSO, Determining the percentage of lead oxide and lead sulphate present by the above formulas we find: 303.1 (1) —— X 69.00 } — 95.00 207.1 + = per cent PbO =s150ne 303.1 — 223.1 223 .1 223.1 (2) | OR 09.00) — 95.00 207.1 —_--———-——— = per cent PhSOQ, = farce 223.1 — 303.1 303.1 Therefore by substituting the percentages of lead and zine oxide in the following formula which is derived from equation (1) the percentage of PbO in the sublimed white lead is easily found. The sum of the percentages of zine oxide and lead oxide subtracted from 99.7 gives the percentage of lead sulphate. Per cent PbO=[1.464 x % Pb — (99.7 — % GnO) YT 219: A comparison of the actual results obtained by the complete analysis of sublimed white lead and its calculated composition shows that the values obtained are concordant. Indeed the only essential factors for the short method are accurate determina- tions of the lead and zine contents. The removal of several steps in the analysis leads to greater accuracy coupled with a con- siderable curtailment of time. A table of comparisons shows the following concordance of results: Te Gee i ras lg a i LS ee ee Re ce ee het i ot aoe See ea oe oe eee ANALYSIS OF WHITE PAINT PIGMENTS 315 TABLE XUUVII . Lead Lead Zine Total No. Analysis sulphate} oxide oxide lead Total MEMUOOINICHO. 555 dae sss 79.20 15.28 Bae 68.30 99.72 vested es... 79.17 TOU. ie et ee Gee tes ooh MMP OINDNIGLG og) la is os. 77.74 16.81 sn 68.70 | 99.66 Riouintede.... ced. et. CL OE AO? O2 iia a reser oo eared Oe ren ce oo = COR Gre TS ean a 77.09 16.95 Halo 68.40 99.77 Ra culated. oS, 76.85 i UP SES Jet ea te iP Me aE a ks Se Ber ONINetet ces. oe. ose 80.20 14.66 4.86 68.40 99.72 : aleuloteis eo. eS 80.15 ee Ot ames ye emer Sr dae oT Demee OM pletej 224... ls. S700) a 10 O0t a5. FT pa 70 OO 071 ain tedaten hi kw. . Keo PAS Va ea 0 Oe te Ca Oe ke, ee ee Mee Gomplctess. 77.84 Lad 4.86 69.00 99.80 Mraleiiistonee oS. 77.69 bE Bs 3 ar CE ea gS) ee a PeimeeOINDIGLE a we... 41222 16.20 Gees 67.80 99.63 A COTUN 7 Ce ea rr 77.41 Who Wel tee ang eae ae ae fe enn ee Beep Omnicte ee... 44.19.| 20.21} 5.48 69.40 | 99.79 Calcnlateds) «22... on o>... 74.00 imate ie eee my ie ET ge ee ek, Pee OMpIEtG h) oui ca wok 77.63 15.92 6.23 67.80 99.78 Menlciulnted foe) lk... ai Al POROU earache re eS oe ge Pre OmMvete .0 44 76.05 17.93 5.73 68 .60 99.71 Soaloniategeri ches) Ss) 76.04 PAGERS acy celle. os ape ema angie me MA IMDIELO a cain ss sk 76.98 Lie78 4.98 69.10 | 99.74 erieiinted ye os she 76.85 EI TU PR eee ene Se ae (ong That this method will prove of value will be readily appreci- ated by all chemists who have to determine the percentage com- position of any basic sulphate of lead, either for the purpose of meeting specifications or for accurate control of finished products. Graphic Analysis of Sublimed White Lead.—In order to escape the determination of SO, and at the same time eliminate the calculations the accompanying chart was devised by Burton Paxton.* The left hand scale of the chart is graduated from 5 to 10, representing percentage of zinc oxide in the pigment. Right-hand scale is graduated from 65 to 70, representing total lead in the pigment. The two center scales are graduated in terms of lead sulphate and lead oxide. A line drawn across the chart connecting any point (a) on the ZnO scale with any point (6) on the Pb scale will intersect the center scales at percent- ages of lead sulphate and lead oxide contained in pigment having a per cent of ZnO and b per cent of Pb. To use the chart it is necessary to have percentages of Pb and ~ * Above method and chart as published by Burton Paxton in Chem. & Met. Eng., May 24, 1922. 316 EXAMINATION OF PAINTS, VARNISHES AND COLORS ZnO in the pigment. These may be determined quite rapidly by volumetric methods as follows: For ZnO.—Boil 1 gram of pigment in 6 cc. HCl, 30 ce. H,O and 5 grams NH,Cl. Pigment will not all dissolve, but this has no effect on result. Dilute to 250 cc. with hot water, add a few drops of 10 per cent sodium sulphite solution and titrate with a standard solution of potassium ferrocyanide, using ammonium molybdate as an outside indicator. Ferrocyanide solution should equal 0.01 gram ZnO per cc. For Lead.—Dissolve 1 gram of pigment in acid ammonium acetate and dilute to 200 ce. Heat to boiling and titrate hot with a standard solution of ammonium molybdate, using tanic acid as an outside indicator. Molybdate solution should equal 0.01 gram of Pb per cc. Now lay straightedge across chart connecting percentage of ZnO on left-hand scale with percentage of Pb on right-hand scale. Intersection of this line with center scales wil] give per- centages of PbSO, and PbO. The sum of percentages of ZnO, PbSO, and PbO is, for all practical purposes, a constant, 99.7 per cent. Using this chart, it is possible to make an analysis of pigment in 10 or 15 minutes. See also Interdepartmental Specifications in back of volume. LEADED ZINC Leaded zinc is a varying compound containing zine oxide and lead sulphate, the latter running from 5 to 35 per cent. Moisture.—Heat 2 grams at 105° C. for two hours. Lead and Zinc.—Determine the lead directly by the volu- metric molybdate method and the zinc by the volumetric ferro- cyanide method as outlined under Basic Sulphate-White Lead. Total Soluble Sulphates.* (In the absence of BaSO,).—Treat 0.5 gram of the sample with 5 cc. of water, 3 grams of NH,Cl and 5 cc. of HCl saturated with bromine; digest (covered) on the steam bath about fifteen minutes, add 25 ce. of H,0O, neutral- ize with dry Na,CO, and add about 2 grams more. Boil ten to fifteen minutes; let settle, dilute with hot water, filter and wash * Report of Sub-committee VIII of Committee D-1, Proceedings of American Society for Testing Materials, 14, 271-2, 1914. ANALYSIS OF WHITE PAINT PIGMENTS 317 with hot water; redissolve in HCl, reprecipitated as above and wash thoroughly with hot water. Acidify the united filtrates with HCl and add a slight excess of 10 per cent BaCl, solution. Let stand on steam bath for one hour, filter, wash with hot water, ignite and weigh the BaSO,. Calculate to SO, (includes SO, formed from SO,). Total Soluble Sulphate (in the presence of BaSO,).—Treat 1 gram in a 600 cc. beaker with 10 cc. of H,O, 10 ce. of strong HCl, saturated with bromine, and 5 grams of NH,Cl, heat on a steam bath in a covered beaker for five minutes, add hot water to make about 400 cc., boil for five minutes and filter to separate any insoluble material. (A pure pigment should be completely dissolved.) Wash with hot water, ignite and weigh the insoluble. Remove lead with Na,CO, as above, making a double preciptation, acidify, and to the boiling hot filtrate add slowly, with stirring, 20 cc. of a 10 per cent BaCl, solution; let stand for two hours on the steam bath, filter, wash, ignite, and weigh as BaSO,. (Includes SO, formed from SO.,.) Soluble Zinc Sulphate.—Boil 2 grams of the sample with 150 cc. of water and 50 cc. of alcohol for thirty minutes, filter and wash with a mixture of alcohol and water (1:3). Heat the. filtrate to boiling and expel most of the alcohol; then determine SO, by the usual method of precipitation with BaCl,. Calculate to ZnSO, and to SO,. Sulphur Dioxide Digest 2 grams of the sample with fre- quent stirring in 100 cc. of freshly boiled cold water and 5 ce. of concentrated HCl; let stand ten to fifteen minutes, add an excess of 0.01 normal iodine solution and titrate back with 0.01 normal sodium thiosulphate solution, using starch indicator. Report as SO,. Run blank on reagents and make corrections. Calculations.—Report soluble SO, as ZnSO, Deduct ZnO equivalent of the ZnSO, from total ZnO and report residue as ZnO. Deduct soluble SO, and SO, equivalent to SO, from total SO., calculate remainder to PbSO,; subtract PbO equivalent of PbSO, from total PbO and report remainder as PbO. See also Interdepartmental Specifications in back of volume. ANALYSIS OF ZINC OXIDE Total Zinc.—Dissolve 0.25 to 0.3 g. in 10 cc. of concentrated HCl and 20 cc. of H,O, make alkaline with NH,OH, then acid with HCl, add 3 ce. more of concentrated HCl, dilute to about 318 EXAMINATION OF PAINTS, VARNISHES AND COLORS 250 cc. with H,O, heat nearly to boiling and titrate with stand- ard potassium-ferrocyanide solution. Report as ZnO (Includes — Cd). Iron, copper or other interfering substances should be first removed. Total Soluble Sulphur.—Moisten a 10 g. sample with water, add a few drops of bromine and then concentrated HCl, boil — to expel bromine. A small strip of aluminum is added and the solution heated gently to throw out any lead that may be pres- ent. Now filter off the lead and insoluble and wash with hot water. Make alkaline with NH,OH, then just slightly acid with HCl, heat to boiling and add about 15 cc. of hot barium-chloride solution. Let stand several hours (overnight), filter on a weighed Gooch crucible, wash well with hot water, dry, ignite for five minutes, cool and weigh as BaSO,. Calculate to S. Sulfur Dioxide.—Mix 5 g. of sample with 50 ec. of warm (freshly boiled and then partly cooled) water to an emulsion and pour into a glass-stoppered flask containing 18 ec. of HCl and exactly 25 cc. of N/10 iodine solution, stopper and shake until all the oxide is dissolved. Titrate the excess of iodine as rapidly as possible with N/10 sodium-thiosulfate solution. Use starch indicator. Calculate to SO.. | Soluble Zinc Sulfate-——Determine as under Leaded-Zinc. Lead Oxide Determination by the Breyer-Croll Electrolytic Method.—9.330 grams of the sample are dissolved in a 250 cc. beaker with 40 cc. of concentrated HNO, and about 100 ce. of distilled water. The solution is boiled for a few minutes until all red fumes are expelled. Add enough silver nitrate to precipitate all chlorides. Electrolyse for two hours, using about 0.5 ampere and a solid sheet platinum anode. The solutions are tested for lead before turning off the current by raising the liquid in the beaker and allowing to continue for twenty minutes. If there is no fresh deposit of PbO,, the electrode is washed three times with distilled water (current still on). After drying one hour at 110° C., the electrode is weighed. The weight of PbO, in milligrams divided by 100 gives the per- centage of PbO. . The above method is satisfactory for routine work on zinc oxide. Where a detailed analysis of other impurities is im- portant, the following method may be used. Ee OL eae oe ae er Te Mase ee ee ee ANALYSIS OF WHITE PAINT PIGMENTS d19 Ferric Oxide.—Treat 10 grams with 50 ce. strong HCl, add about 1 gram KCl1O,, and boil down to a syrupy consistency. Cool, add water and a large excess of ammonia. Allow to stand until the ferric oxide separates, and filter; wash with dilute ammonia water and then with hot water. Dissolve the precipi- tate of ferric oxide in an Erlenmeyer flask with warm dilute H,SO,. Wash the filter paper thoroughly with hot water, dilute the solution in the Erlenmeyer flask to about 200 cc. and pass in hydrogen sulphide for five minutes. Place a funnel in the neck of the flask and boil until all H,S is expelled. Cool and titrate with dilute KMnO,. A blank determination is carried out in a similar manner and the number of cc. of KMnO, re- quired to give a pink color is subtracted from the total number required on the sample. Manganese Oxide.—Treat a 10 gram sample in a 16 ounce Erlenmeyer flask with 100 cc. of HNO, (1:3), heat to boiling and add a pinch of sodium bismuthate, when the pink color of permanganic acid is produced; now add a few cc. of dilute Na,S,O, solution to destroy the pink color, and continue boiling to drive off all nitrous oxide fumes. Cool thoroughly and add 50 ce. of a 3 per cent solution of HNO., and a very small pinch of sodium bismuthate to restore the pink color again. Filter the solution through a Gooch crucible to remove the excess of sodium bismuthate, rinsing the flask and Gooch with 50 cc. of 3 per cent HNO, solution to which a small amount of sodium bismuthate has been added. Now add 10 cc. of ammonium ferrous sulpha%e _ solution, and titrate the excess of ammonium ferrous sulphate with standard KMnO, whose iron value has been determined. One gram of KMn0O, per liter is a convenient strength; and 12.4 grams of ammonium ferrous sulphate, and 50 cc. strong H.SO, to the liter gives a solution which is almost equal to the per- manganate solution. A blank determination is carried out in exactly the same manner as with the sample of oxide, and the difference in the number of cc. of KMnO, required to give a pink color with the blank determination and the sample of oxide is equal to the amount of MnO present. The manganese value of the KMn0O, is calculated from the iron value, according to the ratio of Mn : Fe, or 55 : 279.5 or 0.1968 : 1. Arsenious Oxide-—Weigh 10 grams of oxide in a 16-ounce Erlenmeyer flask, add about 10 grams of FeSO,, place a rubber 320 EXAMINATION OF PAINTS, VARNISHES AND COLORS stopper with an acid delivery tube and an exit tube, which is immersed in a beaker containing about 200 cc. distilled water. The beaker of water is placed in a pan of cold water, the pan having an inlet and overflow. Now add 100 cc. strong HCl from the delivery tube, and heat the flask to boiling so as to dis- till the arsenic into the beaker of water. Continue boiling until about two-thirds of the acid has been distilled, remove from the flame, rinse the delivery tube, add 10 cc. strong HCl to th2 solution in the beaker, warm and pass in H.S to precipitate the arsenic, as As,S,. Let stand in a warm place for some time and filter in a Gooch crucible, wash the precipitate of As,S, with alcohol and then with carbon bisulphide and several times. with dilute alcohol. Dry at 105° C. for one hour and weigh. | Dissolve the As.S,, in the Gooch crucible with dilute ammonia water, wash well with hot water, and dry at 105° C. and reweigh. - The loss in weight is As,S,, from which the As,O, may be calcu- — lated. See procedure for arsenic, p. 34 Standard Methods of - Chemical Analysis, Scott (D. Van Nostrand Co.) Cuprous © chloride used in this method. Chlorine-—Ten grams of the sample are covered with water’ } and 10 ce. of N/10 AgNo, solution, which has been standardized” against pure NaCl, added. Forty ec. of concentrated HNO; 4 are added and the solution boiled until nitrous fumes are re- moved. It is then cooled, 5 cc. of ferric nitrate solution (1:6) ~ added and the solution titrated to a faint pink with N/10 am- monium sulfocyanide (NH,CNS). A blank shall be run with the same reagents, to determine the relative strengths of pe solutions. Acid Insoluble-——A sample of 10 grams is treated with bi 25 ec. of water and 25 cc. of hydrochloric acid and evaporated ; dryness. The residue is taken up with 50 cc. of 1:4 hydrochlor. acid and the insoluble filtered off and thoroughly washed wit i 1:4 hydrochloric acid and then with boiling water. It is further washed with hot ammonium acetate solution and again with boiling water. The insoluble is then burned off and weighed.. Water Soluble Salts —Five grams of the sample are shaken in a 500 cc. graduated flask for 10 minutes with 250 ec. of water at room temperature. The solution is made up to exactly 500 ec. and filtered through dry paper. One hundred cc. of fhe clear filtrate are measured out, poured into a weighed plat) um Ray Mie.” a be, iw oe ANALYSIS OF WHITE PAINT PIGMENTS eae | dish and evaporated to dryness on a sand-bath, the contents be- ing protected from dust. The residue is dried for one or two hours at 110° C., cooled and weighed rapidly. The increase in weight represents the water soluble salts. ANALYSIS OF LITHOPONE ALBALITH, PONOLITH, BECKTON WHITE, STERLING WHITE, » SUNOLITH, ETC. - This pigment is a chemically precipitated pigment containing ~pproximately from 69 to 70 per cent barium sulphate, the re- unainder consisting of zinc sulphide, with occasional impuri- ties of zinc oxide and carbonate. , Moisture—Heat 2 grams for two hours at 105° C. -* Water Soluble-—Determine as under zinc oxide. Insoluble and Total Zinc.—Take 1 g. of the sample in a 200 ec. beaker, add 10 cc. of concentrated HCl, mix, and add in small partions about 1 g. of KCIO,, then heat on the steam & until about half of the liquid is evaporated. Dilute with : : 71.0, add 5 cc. of dilute H,SO, (1:10); boil, let settle, filter, » wash, ignite, cool, and weigh the insoluble which should be only c°: make a qualitative examination for alumina and silica. ;The insoluble should be examined under the microscope for the presence of natural crystallin barytes. Sample may also be _ examined direct. Make filtrate from insoluble alkaline with 3 NH, OH, acid with HCl, add 8 cc. of concentrated HCl, dilute to. about 250 cc. with H,O, heat nearly to boiling and titrate with K,Fe(CN), solution as under zinc white. Calculate to Zn. Zinc Oxide.—Treat a 4 g. sample of the lithopone for 4 hours »Ww? a 200 cc. of 1 per cent acetic acid at room temperature, stir- -_ g occasionally. Filter by suction on a double filter paper and ~ ash with cold water; add to the clear filtrate 13 cc. of concen- t ated NH,OH, neutralize with HCl and then add 3 cc. of con- centrated HCl in excess. Heat to boiling and titrate with K\Fe(CN),, using uranium-acetate solution as an outside indi- cator. Calculate to ZnO. Calculate this result to Zn, subtract froin total Zn, and calculate the difference to ZnS. (Any ZnCO, or ZnSO, is included in the ZnO.) ‘Zine Sulfide.*—Place 0.5 g. of pigment in evolution flask with .* ‘olution Method of W. G. Scott, “White Paints and Painting Ma- te _,’ p. 257; see also Blair, “Chemical Analysis of Iron.” O22 EXAMINATION OF PAINTS, VARNISHES AND COLORS about 10 g. of “feathered” or mossy zinc, add 50 cc. of water; insert the stopper carrying a separatory funnel and an exit tube. Run in 50 ce. of concentrated HCl from the funnel, having previously connected the exit tube to two absorption flasks in series; first flask contains 100 cc. of alkaline lead-nitrate solu- tion; second flask, 50 cc. of same as a safety device. After all of the acid has run into the evolution flask, heat slowly, finally boiling until the first appearance of steam in the first absorption flask; disconnect, let the lead sulfide settle, filter, wash with cold water, then with hot water till neutral to litmus paper and wash- ings give no test for lead. The PbS precipitate is dissolved in hot, dilute HNO., evaporate to fumes with H,SO, and finally weighed as PbSO,. Calculate PbS or PbSO, to ZnS. The alkaline lead solution is made as follows: Into 100 ec. of KOH solution (56 g. in 140 ec. of H,O) pour a saturated solution of lead nitrate (250 g. in 500 ec. of H,O) until the pre- cipitate ceases to redissolve, stirring constantly while mixing. About 3 volumes of the lead solution will be required for one of the alkali. Instead of absorbing the evolved H,S in alkaline lead-nitrate solution, a solution of 8 g. of cadmium chloride in 250 cc. of water and 150 cc. of NH,OH (sp. gr. 0.90) may be used. The CdS precipitate may be filtered on a weighed Gooch, washed with water containing a little NH,OH, dried at 100° C., and weighed. Calculate to ZnS. It is better to filter the CdS on a small filter and wash as above, then place filter and precipitate in a beaker and dissolve in HCl and KCIO, (keeping at room temperature at first), filter out any paper pulp or insoluble matter; make filtrate alkaline with NH,OH, then just acid with HCl, heat to boiling and precipate with BaCl, in usual manner. Filter, wash, ignite, and weigh BaSO,. Calculate to ZnS. For very rapid work the contents of the absorption flask, after all H,S has been absorbed, may be washed into a vessel with cold water and diluted to about one liter, acidified with concentrated HCl and titrated with standard iodine solution, using starch indicator. (The precipitate should be completely dissolved.) The iodine solution is prepared by dissolving about 12.7 g. of pure resublimed iodine and 18 g. of KI in a little water and then diluting to one liter. ANALYSIS OF WHITE PAINT PIGMENTS 323 While the above methods have proved generally satisfactory, the evolution method for zine sulfide is rather tedious. Breyer and Croll of the N. J. Zinc Co. omit this method and secure the zine sulfide content by difference, after determining total zinc and barium sulfate. Their methods for the latter as communi- cated recently to the writer, are given below: Total Zine in Lithopone (B * C Method).—A 2 gram sample is weighed out into a 150 ce. beaker and treated with 25 cc. con- centrated hydrochloric acid. When action has largely ceased, 80 ce. of 1:1 sulphuric acid is added, evaporated to fumes and the heating continued, with beaker covered, until all barium sulphate has gone into solution. After cooling, cold water is poured in to nearly fill the beaker. The solution and reprecipi- tated barium sulphate are then poured into a graduated 500 cc. flask, water added to the mark and the whole thoroughly mixed and filtered. A 250 cc. portion of the clear filtrate is measured out into a 600 cc. beaker, 20 cc. of citric acid solution and 10 ec. of ferric nitrate solution added. The excess acid is neutralized with ammonia, using litmus paper, and a definite excess of 15 cc. of ammonia added. The solution is brought to a boil and then the titrating solu- tion of potassium ferrocyanide is run in with constant stirring until within 1 cc. of the end point. The addition is continued 0.2 cc. at a time until all the zinc has been precipitated as indi- cated by a blue coloration appearing when a drop of the solu- tion is added to a few drops of acetic acid on a test plate. The potassium ferrocyanide solution is standardized by start- ing with a weighed amount of C.P. zinc approximately equal to the amount to be titrated in the sample, and carrying through the same procedure. Barium Sulphate in Lithopone (BX C Method).—A 1 gram Sample is weighed out into a platinum crucible, mixed with 6-8 grams of sodium carbonate and fused for twenty minutes over a Bunsen Burner and twenty minutes over a blast lamp. The fusion is then leached out with about 200 cc. of hot water in a 250-cc. beaker. The insoluble barium carbonate is filtered off and washed thoroughly with hot sodium carbonate solution (2 grams per liter). The barium carbonate is then dissolved from the paper into a 600-cc. beaker with hot 1:4 hydrochloric acid, 324 EXAMINATION OF PAINTS, VARNISHES AND COLORS washing thoroughly. The solution is diluted to about 400 cc. neutralized with ammonia and then made slightly acid with hydrochloric acid (2 cc. excess). The solution is heated to boil- ing and barium sulphate precipitated with hot ammonium sul- phate solution (40 grams per liter). After standing four hours © on a steam plate, the barium sulphate is filtered off on to a weighed, ignited Gooch crucible. See also Interdepartmental Specification in back of volume. . For a scheme of analysis for Cadmium Lithopone see chapter on Yellow Pigments, page 359. ANALYSIS OF DRY TITANOX The recent advent of titanium oxide as a constituent of white paints should be of interest to analytical chemists, since special methods are necessary for the determination of the titanium present. There is given below L. E. Barton’s method for the analysis of dry titanium oxide pigment such as is made in the United States and which usually contains 75% barium sulphate and 25% titanium oxide. There is also given a method for the separation of zinc and lead from mixtures containing titanium. Determination of Barium Sulphate—Weigh 14 gram sample into 250 cc. Pyrex glass beaker; add 20 cc. concentrated sul- phuric acid and 7 or 8 grams sodium sulphate. Mix well and heat on hot plate until fumes of sulphuric anhydride are evolved and then heat directly over flame to boiling for five minutes or until solution is complete. Traces of silica, if any, remain as an insoluble residue. Cool, take up with 100 ce. of water, boil and filter off barium sulphate and silica, washing with 5 per cent sulphuric acid to free residue from titanium. Determination of Titaniwm.—The volumetric method used for determination of titanium is essentially that described by P. W. & E. B. Shimer (Proc. Eight Internat. Congress of Ap- plied Chem.) ; the method hereafter described differing prin- cipally in the form of reductor and also in a few details of oper- ation. Reagents.—Standard ferric ammonium sulphate solution. Dissolve 30 grams of ferric ammonium sulphate in 300 cc. water acidified with 10 cc. of sulphuric acid; add potassium per- manganate drop by drop as long as the pink color disappears, to ANALYSIS OF WHITE PAINT PIGMENTS WAS oxidize any ferrous to ferric iron; finally dilute the solution to one liter. Standardize this solution in terms of iron. The iron value multiplied by 1.4829 gives the value in titanic oxide (TiO,) ; and iron value multiplied by .86046 gives the value of the solution in terms of metallic titanium. Indicator—Saturated solution of potassium thiocyanate. Reductor.—As a reductor a 500 cc. dispensing burette is used. The internal dimensions of the burette are 15% inches by 22 inches. The reductor is charged with 1200 grams of 20 mesh amal- gamated zinc, making a column about 12 inches high and hav- ing an interstice volume of about 135 cc. This form of reductor is convenient, and when used as hereafter described is adapted to maintaining hot solutions, which is essential for complete reduction of the titanium. The reductor is connected to a liter flask for receiving the reduced titanium solution through a three-hole rubber stopper, which carries also an inlet tube for carbon dioxide supply and an outlet tube for connecting with the suction pump. The reductor is prepared for use by first passing through it a little hot dilute sulphuric acid followed by hot water, finally leaving sufficient hot water in the reductor to fill to the upper level of the zinc. The hot filtrate from the barium sulphate determination is now introduced; about 10 cc. of water being drawn from the reductor into the original beaker to bring the solution to about the upper level of the zinc. The water thus removed will not contain any titanium if the operation has been conducted as described, but it serves as a safeguard and is also convenient to acidify this water with 10cc. sulphuric acid and reserve it on the hot plate to be used as an acid wash after the reduction of the sample solution. - The titanium solution is allowed to remain in the reductor for 10 minutes. While the solution is being reduced, the receiving flask is con- nected to the reductor and the air completely displaced by carbon dioxide, conveniently drawn from a cylinder of the liquified gas. | \ ~ 326 EXAMINATION OF PAINTS, VARNISHES AND COLORS When the reduction is complete the receiving flask is con- nected with the suction pump, and while still continuing the flow of carbon dioxide the reduced solution is drawn out, fol- lowed by the reserved acid wash and then three or four 100 ce. washes with hot water. The displacement of the sample solu- tion and washing of the zinc is so regulated by means of the stopcock that the reductor is always filled with solution or water to the upper level of the zinc. When the washing is complete, gradually release the suction to prevent air being drawn back into the receiving flask. Disconnect the flask, add 5 cc. of potassium thiocyanate solu- tion as indicator and titrate immediately with standard ferric ammonium sulphate solution, adding the solution rapidly until a brownish color is produced, which will remain for at least one minute. ANALYSIS OF PAINTS CONTAINING TIO, After the pigment has been extracted and dried, a sample is weighed out and decomposed by the ordinary acid treatment. Weigh 1 gram into a 250 cc. Pyrex beaker; add 40 cc. concen- trated sulphuric acid and 15 grams ammonium sulphate. Mix well and heat on a hot plate until fumes of SO, are evolved, and then continue heat to boiling for five minutes. Silica, if pres- ent, will, of course, remain undissolved. Cool, take up with 200 ce. water, boil and filter off lead sulphate, barium sulphate, silica, and similar acid insoluble inert pigments. Separate as usual. (See above.) The filtrates should contain the titanium and zinc in solution as sulphates. To the filtrate ammonia is added in excess, which precipitates the titanium with the iron group. For the complete separation of zinc from the iron group, the hydroxide precipitate should be re-dissolved in acid and a second precipitation with ammonia should be made.. Zine may then be determined in the combined filtrate. Titanium should be determined on a separate sample, as de- scribed in the above method for dry TiO, pigments. See also F. S. B. Spec. No. 115, back portion of this volume and new specification of Federal Specification Board to be issued in February, 1925, on Titanox-Zinc Ready Mixed Paint Resistant to Sulphur Gases. ANALYSIS OF WHITE PAINT PIGMENTS 327 ANTIMONY OXIDE PIGMENTS Antimony Oxide.*};—Antimony trioxide (Sb,O,) a fume pig- ment that has recently been introduced, may be occasionally found in certain classes of mixed paints. After being brought into solution, it may be quantitatively estimated by oxidation with permanganate or iodine. (See pages 27 and 28, Scott’s Standard Methods of Chemical Analysis.) SILICA OR SILEX—-CHINA CLAY—ASBESTINE These pigments, while all true silica pigments, are widely different from the standpoint of physical structure. A micro- scopic examination is of great value, showing silica or silex to consist of small, sharp particles, china clay to be tabloid in ap- pearance and asbestine to consist of long, rod-like fibrous par- ticles. Moisture—Heat 2 grams at 105° for two hours. Loss on Ignition.—Ignite 1 gram to constant weight in a platinum crucible. Insoluble Matter.—Boil 2 grams for thiry minutes with 50 ec. HCl (1:1), add 50 cc. of water, wash, ignite, and weigh in- soluble residue. In the case of china clay, or asbestine, a sodium carbonate fusion should be resorted to, with the subsequent dehydration of the silica. The insoluble residue in either case is volatilized with H,SO, and HF in the usual manner, any loss in weight being considered silica. Any residue is fused with sodium carbonate, the fusion being added to the original filtrate. Should BaSO, be present, the melt is digested with warm water, the BaCO, filtered off, washed, dissolved in hot diluate HCl and precipitated and de- termined as BaSQ,. The filtrates, combined from the preceding filtrations, are ex- amined for alumina, iron, manganese, calcium and magnesium in the usual way. Should it be necessary to determine the alkalies present, a * See “The evaluation of white pigments with special reference to anti- mony oxide,” by H. E. Clarke, J. Oil & Colour Chemists’ Assoc., Vol. 4, pp. 2-26 (1921); Chem. Abstrs., Vol. 15, p. 2197 (1921). + See also Circulars 152 and 153 of Scientific Section for results of ex- posure tests. 328 EXAMINATION OF PAINTS, VARNISHES AND COLORS separate sample is treated according to the J. Lawrence Smith method as described in Bulletin No. 700, U. S. Geological Survey. Carbon Dioxide-—Determine by evolution with HCl, weighing in soda-lime, KOH solution, or by absorbing in Ba(OH), solu- tion and titrating or weighing as BaCO,. Any excess of calcium is reported as oxide. The magnesium is calculated as MgO, unless the carbon dioxide is in excess of the amount of calcium present, in which case it is reported as MgCoO,, and the remainder as MgO. CALCIUM PIGMENTS WHITING, PARIS WHITE, SPANISH WHITE, AND CHALK These pigments are of the following composition: Whiting.—The natural form of calcium carbonate. Paris White.—The artificial form of calcium carbonate. Gypsum.—The hydrated form of calcium sulphate, of formula CasO 7. 2H-0; These pigments are analyzed in the following manner: Moisture.—Heat 2 grams at 105° C. for two hours. Total Soluble Lime.*—Weigh out 0.75 g. of the pigment into a small crucible, ignite cautiously to dull redness to destroy organic matter, cool, transfer to a 400-ce. beaker, add 20 ce. of HO, cover, then add 15 cc. of concetrated HCl and 3 or 4 drops of concentrated HNO,, and boil till all the soluble matter is dis- solved and all the CO, expelled. Wash off and remove the cover, dilute to about 150 cc. with freshly boiled H,O, heat to boiling and add dilute NH,OH (sp. gr. 0.96) carefully until a shght permanent precipitate forms. Heat to boiling and add 10 cc. of a 10-per-cent solution of oxalic acid; stir until the oxides of iron and aluminum are entirely dissolved and only a slight precipitate of calcium oxalate remains. Now add 200 cc. of boiling H,O and sufficient saturated solution of ammonium oxalate (20 to 25 cc.) to precipitate the lime. Boil and stir for a few moments, remove from the heat, let settle and filter on an 11-cm. filter. Wash 10 times with 10-to-15-cc. portions of hot water. Place beaker in which precipitation was made under the funnel, pierce apex of filter with stirring rod and wash pre- * Meade, ‘Portland Cement.” ANALYSIS OF WHITE PAINT PIGMENTS 329 cipitate into beaker with hot water, pour warm dilute H,SO, (1:4) through paper and wash a few times; add about 30 cc. of the dilute H,SO, (1:4), dilute to about 250 cc., heat to 90° C. and titrate at once with standard KMnO, solution (solution should not be below 60° C. when end-point is reached). The KMn0O, is best standardized against Bureau of Standards sod- ium oxalate.* Calculate to CaO and CaCO.,,. Mixed Calcium and Magnesium Carbonates.t—Weigh 1 g. of the finely powdered sample into a small porcelain dish, add 25 ec. of normal HCl, cover with a watch glass, and when efferves- cence has ceased, heat to boiling. Cool and titrate with normal NaOH solution, using methyl orange as indicator. The calculation is as follows: One gram CaO=35.7 cc. of normal acid. CaO x 1.7844 = CaCO,. Subtract number of cubic centimeters of NaOH re- quired from 25; result gives number of cubic centimeters of nor- mal acid corresponding to the CaCO, + MgCO,. Multiply the weight of CaO in 1 g. of sample (as found in preceding section on total soluble lime) by 35.7; product gives number of cubic centimeters of normal acid corresponding to the CaO present; subtract from total number of cubic centimeters of acid re- quired by CaCO, + MgCO, and multiply result by 0.042, obtain- ing weight of MgCO, in 1 g. of sample. The MgCO, determined by this process should not differ more than 0.25 per cent from that obtained by more elaborate methods. It is to be noted that this method is a measure of the total alkalinity, and if Ca or Mg are present in other forms than carbonate, a complete analysis would be necessary to give percentages of CaCO, and MgCO,. BARYTES AND BLANC FIXE Of these two barium pigments used in the manufacture of paints, barytes is the natural barium sulphate, while blanc fixe is precipitated barium sulphate. The following method may be used for the analysis of these pigments: Moisture.—Heat 2 grams at 105° C. for two hours. Loss on Ignition—lIgnite 1 gram to constant weight. The * Circular No. 40, Bureau of Standards. + J. W. Mellor, “A Treatise on Quantitative Inorganic Analysis,” p. 522. 330 EXAMINATION OF PAINTS, VARNISHES AND COLORS loss will be reported as loss on ignition, and will consist of free and uncombined water, carbon dioxide and organic matter. Barium Sulphate.—Boil 1 gram with dilute HCl, evaporate to dryness, moisten with HCl, add water, boil, filter and wash. Should lead be present in the insoluble residue, as shown by the action of H,S, treat the insoluble residue with a little (1:1) HCl and several drops of H,SO,. Filter, wash and weigh the residue. Treat the ignited residue with H.SO, and HF, evap- orate to dryness and ignite. The residue should show no loss as silica. The filtrate is examined for alumina, iron, calcium and magnesium in the usual manner. Soluble Sulphates.—Treat 1 gram with 20 ce. cone. HCl, dilute to 200 cc. with hot water, boil, filter, wash, add NH,OH until neutral, make acid with HCl and precipitate any sulphat as BaSO,. Determine in the usual manner. Calculate to CaSO,. If carbonates are present, calculate the remaining CaO to CaCO,. Any excess of oxide is reported as CaO. Carbon Dioxide.—Determine as outlined under silica. If any barium carbonate is present, it is determined in the filtrate from the preliminary HCl treatment, by precipitation and weighing, as BaSO,. Any excess of carbon dioxide over the barium is reported as calcium carbonate. ANALYSIS OF A COMPOSITE WHITE PAINT A white paint may consist of a mixture of any of the preced- ing pigments, except that lead pigments and lithopone are sel- dom found together. After separation from the oil and other liquids as outlined in Chapter XXIV, page 213, the white pigment mixture may be rapidly analyzed by the following method. It is, however, often advisable to resort to a qualitative examination before beginning the quantitative analysis. Also note method of analysis in inter- departmental specifications. Insoluble Residue.—Boil 1 gram of the sample with 20 cc. (1:1) HCl. Evaporate to dryness, moisten the residue with a few cc. of concentrated HCl, allow to stand a few minutes, dilute with hot water, boil, filter and wash the insoluble residue thor- oughly with hot water. Treat the insoluble residue with (1:1) HCl and 2 cc. H,SO, to remove the last traces of lead. Filter, ANALYSIS OF WHITE PAINT PIGMENTS dol wash and weigh the insoluble residue. Determine the silica by volatilization with H,SO, and HF. Any loss is reported as silica. Determine the BaSO, in the residue by boiling with dilute HCl or making a potassium bisulphate fusion. The residue remain- ing after either of these treatments is reported as barium sul- phate. Total Lead.—This constituent can be best determined on a separate sample. To 1 gram add 10 cc. of conc. HNO., boil, add, after cooling, conc. H,SO, and evaporate to strong SO, fumes. Dilute with water, allow to stand several hours, filter, wash slightly, dissolve and determine the lead volumetrically as out- lined under Basic Sulphate White Lead. Lead can also be determined in the combined filtrates from the insoluble residue. Precipitate the lead in an acid solution with H,S and determine volumetrically in the above outlined manner. To determine whether both sublimed white lead and corroded white lead are present, treat a separate portion of the paint with boiling acetic acid, filter and collect the insoluble residue. De- termine the lead either in the filtrate or in the insoluble residue by the volumetric method. The lead soluble in acetic acid is the basic carbonate of lead and the lead oxide from the sublimed white lead, while the lead sulphate from the sublimed white lead remains insoluble. Alumina and Iron Oxide—Remove the H,.S from the filtrate by boiling, after removal of the lead, and precipitate the hydroxides in an ammoniacal solution after boiling with the ad- dition of a few drops of HNO,. Determine and separate in the usual manner. Zinc.—Precipitate the zinc in the filtrate from the alumina and iron precipitation, after acidifying with acetic acid, and de- termine the zinc as outlined under Basic Sulphate White Lead. Calcium and Magnesium.—Determine the calcium and mag- nesium in the filtrate from the precipitation of zinc sulphide in the usual manner, testing, however, first for the presence of barium. Sulphate.—Determine as outlined under Zinc Lead and Leaded Zincs. 332 EXAMINATION OF PAINTS, VARNISHES AND COLORS Sulphide.—Should lithopone be present, separate the zinc oxide and zinc sulphide as outlined under Lithopone. Carbon Dioxide.—Determine as outlined under Silica. Calculations.—Silica is reported as silica, except where alu- mina is present, showing the presence of china clay. In this case, calculate the alumina to clay by the method of Scott. — Weight of Al,O, + 2.5372 — weight of clay. Weight of clay < 0.4667 = weight of SiO, in clay. Any difference greater than 5% may be considered silica. Barium sulphate is reported as barium sulphate or as lith- opone, if zine sulphide is present, according to the given com- position of lithopone, 70% barium sulphate and 30% zine sul- phide. 3 Lead is reported as Basic Carbonate of Lead on the formula 2PbCo,.Pb(OH).. Calculate lead soluble in acetic acid, after determining CO,, to basic lead carbonate and any residual lead to lead oxide which, together with the lead sulphate, is reported as Sublimed White Lead. Should calcium sulphate be present the portion soluble in water is examined for lime or sulphuric acid and calculated to calcium sulphate, any residual lime being calculated to calcium carbonate and any residual sulphuric acid being calculated to lead sulphate. Any residual CO, after calculating calcium car- bonate is calculated to white lead and any residual lead is cal- culated to lead oxide. Lead oxide should not be reported except in the presence of lead sulphate. Any large percentage of magnesium denotes the presence of asbestine. See also Interdepartmental Specifications in back of volume. a a? oe ‘a: = ‘2 foNGy Fie ‘ef = fle De Oe eek. eS CHAPTER XXXVI. ANALYSIS OF LEAD OXIDES These pigments in the pure form are oxides of lead, of the generally accepted formula, Pb,O,, being probably mixtures of lead monoxide, and lead dioxide. In chemical composition they are the same, the proportions of lead monoxide and lead dioxide varying, however, but by their physical structure and color they can be readily differentiated. Two methods are given for the analysis of this pigment. Moisture.—Dry 2 grams at 105° for two hours. Organic Color.—Boil 2 grams with 25 cc. of 95% ethyl alcohol, let settle, decant off the supernatant liquid; boil residue with water, decant as before and boil residue with very dilute NH,OH. If either the alcohol, water or NH,OH is colored, organic coloring matter is indicated. Total Lead and Insoluble Residue.—Treat 1 gram with 15 ce. of HNO, (1:1) and sufficient hydrogen dioxide to dissolve all the PbO, on warming. If any insoluble matter is present, add 25 ec. of water, boil, filter and wash with hot water. Insoluble contains free SiO,, and should be examined for BaSO, and silicates, if appreciable. To the original solution or filtrate from insoluble, add 20 cc. of conc. H,SO, and evaporate to SO, fumes; cool and determine lead as lead sulphate either gravi- metrically or volumetrically. If the sample contains soluble barium salts, the PbSO, will contain BaSO, and should be treated with acid-ammonium acetate solution, the lead being de- termined in the filtrate. Determination of Lead Peroxide (PbO,) and True Red Lead (Pb.0,). (Method of Diehl,* modified by Topft—not applic- able when substances are present, other than oxides of lead, that liberate iodine under conditions given.) Weigh 1 gram of finely ground sample into a 200-cc. Erlen- meyer flask, add a few drops of distilled water and rub the mixture to a smooth paste with a glass rod flattened on end. Mix in a small beaker 30 grams of C.P. “Tested Purity” crystal- *Dingl. Polyt. Jour., 246, 196. + Zeitschrift fiir analytische Chemie, 26, 296. 333 334 EXAMINATION OF PAINTS, VARNISHES AND COLORS lized sodium acetate, 2.4 grams of C.P. potassium iodide, 10 cc. of water and 10 cc. of 50% acetic acid; stir until all is liquid, warming gently; if necessary add 2 or 3 cc. of H,0, cool to room temperature and pour into the flask containing the red lead. Rub wit hthe glass rod until nearly all the red lead has been dissolved; add 30 cc. of water containing 5 or 6 grams of sodium acetate, and titrate at once with decinormal sodium thiosulphate, adding the latter rather slowly and keeping the liquid constantly -In motion by whirling the flask. When the solution has become light yellow, rub any undissolved particles up with the rod until free iodine no longer forms, wash off rod, add the sodium thiosulphate solution until pale yellow, add starch solution and titrate until colorless, add decinormal iodine solution until blue color is just restored and subtract the amount used from the volume of thiosulphate that had been added. : Calculation.—The iodirie value of the sodium thiosulphate solution multiplied by 0.94193 = PbO,; the iodine value multi- plied by 2.69973 = Pb,O,; the PbO, value multiplied by 2.86616 = POO r: . Sodium Thiosulphate Solution (decinormal) —Dissolve 24.83 grams of C.P. sodium thiosulphate, freshly pulverized and dried between filter paper, and dilute with water to 1 liter at a tem- perature at which the titrations are to be made. The solution should be made with well-boiled H,O, free from CO., or let stand eight to fourteen days before standardizing. Standardize with pure, resublimed iodine and also against pure potassium iodate. The two methods of standardization should agree within 0.1% on iodine value. In place of pure iodine, a decinormal solution of potassium permanganate may be used for standardization. Starch Solution.—Two to 3 grams of potato starch are stirred up with 100 cc. of 1% salicylie acid solution, and the mixture boiled till the starch is practically dissolved and then diluted to 1 liter. | The second method for determination of the lead peroxide or true red lead content is somewhat shorter. Treat 1 gram in a beaker with 15 cc. of nitric acid, sp. gr. 1.2 (110 ce. nitric acid sp. gr. 1.42 to 100 ce. of water). Stir the sample until all trace of red color has disappeared. Add from ANALYSIS OF LEAD OXIDES Soper a calibrated pipette or burette exactly 10 cc. of dilute hydrogen dioxide (1 part of 3% hydrogen dioxide to 3.5 parts of water). Add about 50 cc. of hot water and stir until all the lead dioxide has passed into solution. In the case of some coarsely ground oxides the contents of the beaker may have to be gently heated to effect complete solution. After the oxide has completely passed into solution, dilute with hot water to about 250 cc. vol- ume and titrate directly with a standard potassium perman- ganate solution, having an iron value of 0.005. Titrate to the faint pink permanganate color. A blank titration on the hydro- gen dioxide solution must now be made. Into a beaker pour 15 cc. of nitric acid of above strength and add exactly the same amount of hydrogen dioxide (10 cc.). Dilute to 250 cc. with hot water and titrate with standard potas- sium permanganate solution to a faint pink color. The difference between the number of cc. of potassium per- manganate required for the blank titration and the number re- quired for the red lead titration is the amount required for the hydrogen dioxide which was reacted on by the red lead. The difference between the two amounts of potassium permanganate required multiplied by 3.058 grams gives the percentage of red lead present. The difference multiplied by 1.067 gives the per- centage of PbO, present. Lead in Extracted Pigment.—Another very good method of determining the percentage of true red lead in an extracted pig- ment is to weigh the sample into a flask, add no water, but sub- stitute 10 cc. of a mixture of 7 parts of chloroform and 3 parts of glacial acetic acid, and proceed in the usual manner as out- lined above. ——_—_— The latest methods for the examination of red lead and lith- arge, together with colorimetric measurements for the de- termination of copper and iron in pig lead, lead oxides, and lead carbonate, as furnished the writer by Dr. John A. Schaeffer, J. A. Calbeck and B. S. White, of The Eagle-Picher Lead Co., are given herewith. 336 EXAMINATION OF PAINTS, VARNISHES AND COLORS A COLORIMETRIC METHOD FOR THE DETERMINATION OF COPPER AND IRON IN PIG LEAD, LEAD OXIDES, AND LEAD CARBONATE* Most methods in use for the determination of the small per- centage of copper contained in pig lead, lead oxides and lead carbonate are long and tedious. This is especially true in those instances where refined metal serves as the base for the finished product and the copper content being extremely low, many diffi- culties present themselves; these can be overcome by the use of this colorimetric method. While the estimation of the iron content in these compounds can be readily carried out colorimetrically by a Separate ana- lysis,t it has been found that the following method, which com- bines the determination of both copper and iron colorimetrically In one analysis, adds greatly to the rapidity and accuracy in finding the percentages of these impurities. The method not only eliminates the use of hydrogen sulphide, but it shortens the time of a single analysis to 30 to 40 minutes, while the re- sults attain the same degree of accuracy as those established by the longer and more complicated methods. The method of procedure varies somewhat with the nature of the sample to be examined: hence, it will be necessary to make especial mention of red lead. | ANALYSIS OF Pic LEAD, LITHARGE AND LEAD CARBONATE FOR COPPER Weight of Sample.—In analyzing refined pig lead, or lead compounds made from refined metals, it is necessary, owing to the small percentages of copper and iron usually present, to use large samples. It has been found, by the use of this method, that smaller samples may be used with equally accurate results, thereby reducing the bulk to be handled and eliminating any errors which frequently result from the use of large volumes. A sample weighing 30 grams has been found sufficiently large for refined products, and not over 10 grams need be used for the crude or unrefined material. Method of Procedure.—Weigh the finely divided sample into a 400-cc. beaker, and add small portions of hot (1:1) nitric acid until solution is effected. If any basic lead nitrate has been * J. Ind. Eng. Chem., 7, 1035 (1915). +J. Ind. Eng. Chem., 4, 659 (1912). ANALYSIS OF LEAD OXIDES 337 formed, dilute slightly with warm water and boil. Add 32 cc. (1:1) sulphuric acid, stirring constantly while adding. Let the precipitate settle, and decant filtrate through a coarse filter paper. Wash four times by decantation, using small portions of warm, distilled water. Transfer the precipitate to the paper, wash again and allow to drain. Make the filtrate neutral with ammonium hydroxide and add 4 cc. excess. Boil for a short time and filter. Wash the precipitate well with warm water, and reserve for the determination of the iron. MRender the filtrate acid with special c. p. hydrochloric acid, adding not more than two drops excess. Add six drops of (1:10) potassium ferrocyanide solution, filter through close filter papers using two to each funnel. Catch the filtrate and inspect for copper ferrocyanide. Let the precipitate drain well without washing. Dissolve the copper ferrocyanide off of the paper with alternate washings of small portions of ammonium hydroxide and hot water. Wash well and keep the bulk to 30 or 40 cc. Render ! slightly acid with hydrochloric acid, adding not over two drops excess. Transfer to a 100-cc. Nessler tube, and dilute to mark with distilled water. The copper is then determined colori- metrically according to a modification of the method of Car- nelly.* In another Nessler tube, place 10 cc. of 5 per cent ammonium nitrate solution, two drops concentrated nitric acid and 90 cc. distilled water, add from a burette graduated to tenths of 1 cc., standard copper sulphate solution until the color matches the sample under examination. Standard Copper Sulphate Solution.t—“Dissolve 0.393 gram of pure CuSO,.5H,O, in one liter of distilled water. 1 cc. = 0.0001 gram of copper,” or 0.00033 per cent when using a 30- gram sample. — Analysis of Red Lead for Copper.—Treat 30 grams of the sample with 40 ec. (1:1) nitric acid, using great care that the violence of the reaction does not cause the sample to froth over the beaker. Slowly add 30 to 40 cc. of 8 per cent hydrogen peroxide, stirring constantly. Boil until solution is effected, and proceed as directed above. Sodium sulphite c. p. may be used in place of the hydrogen * Sutton’s Volumetric Analysis, p. 204. + Sutton’s Volumetric Analysis, p. 205. 358 EXAMINATION OF PAINTS, VARNISHES AND COLORS peroxide for effecting the solution of lead peroxide, adding it dry in small portions and boiling until no brown lead peroxide is present. Determination of Iron in the Above Compounds.—For the iron determination, use the precipitate of iron hydroxide re- moved from the copper solution, proceeding as follows: Dis- solve the precipitate contained on the paper with (1:1) hydro- chloric acid, collecting the filtrate in a 300-cce. volumetric flask. Wash the paper free from acid with hot, distilled water, dilute to mark, and mix thoroughly. Place 10 ec. in a 100-ceec. Nessler tube, add three drops nitric acid, 10 ee. (1:15) ammonium sul- phocyanide solution, dilute to mark and compare with a stand- ard iron solution.t The color is compared with a blank made in the following manner: A solution of ferric ammonium sulphate of known strength is required. This is made by dissolving 0.7022 gram of ferrous ammonium sulphate in water. Acidify with sul- phuric acid, heat to boiling and add a solution of potassium permanganate until all the iron is converted to the ferric condi- tion. Only the very slightest pink tinge may be present after the addition of the potassium permanganate, as this tinge will fade away, while the presence of a pink color tends to vitiate the results. Allow the solution to cool and dilute to one liter. One cc. of this solution equals 0.0001 gram of iron. Prepare the blank by pouring into a 100-cc. Nessler cylinder, 10 cc. ammonium sulphocyanide solution, and three drops of concentrated nitric acid. Dilute to 100 ec. and titrate to the exact color developed in the sample under examination, by the addition of the standard ferric ammonium sulphate solution. One cc. of this solution equals 0.01 per cent iron as the 10 cc. removed from the flask contained 1 gram sample. It will be found that the color can be accurately compared to within 0.001 per cent of iron content. Comparison of Results on Copper.—Table XLVIII shows the results obtained by the above method, as compared with the method set forth by Fresenius,* on two sets of samples and a copper sulphate solution of known strength. {£J. Ind. & Eng. Chem., 4 (1912), 659. * Fresenius’ Quantitative Chemical Analysis, Vol. II, p. 584. ANALYSIS OF LEAD OXIDES 339 Precautions and Interfering Elements.—I£ the sample con- tains much zinc, the following method may be used for remov- ing it: The filtrate from the iron precipitation, before precipi- tating the copper ferrocyanide, is rendered slightly acid with acetic acid, and 5 cc. of an 8 per cent sodium ammonium phos- phate solution are added; boil, cool, filter and treat the filtrate as before outlined. TABLE XLVIII—Comparative Results (Percentages Cu) by Method of Fresenius and of Author Litharge and Pig Lead Red Lead CuSO, Solution No. Fres. Color. Fres. Color. Fres. Color. Lee present 1 0.0009 | 0.00088 | 0.002 0.002 0.002 0.002 0.002 2 0.0013 | 0.0013 | 0.0008 | 0.0008 | 0.0008 | 0.0008 | 0.0008 3 0.0009 | 0.00088 | 0.0009 | 0.00088 | 0.00066 | 0.00066 | 0.0007 4 0.002 0.002 0.0007 | 0.0007 | 0.001 0.001 0.001 5 0.001 0.001 0.0015 | 0.0015 | 0.00066 | 0.00066 | 0.00066 6 C200 loa 0015, > 6.00388. | 0.0038 | 0.0015. | 0.0015 | 0.0015 cf 0.0012 | 0.0012 | 0.00088 | 0.00088 | 0.00088 | 0.00088 | 0.00088 8 0.0079 | 0.0079 | 0.00088 | 0.0009 | 0.0009 | 0.00088 | 0.0009 | 9 eu tawoeo O0lo: | 6:0013 }.0:0018) |) 0.0015. }.0.0015° | 0.0015 10 0.0004 | 0.0004 | 0.00066 | 0.00066 | 0.0007 | 0.00066 | 0.0007 Lead, when present in not too large quantity, has little or no effect on the accuracy of the colorimetric comparison of copper. If a faint white cloud of lead ferrocyanide should develop in the sample under examination, the addition of a small amount of very dilute lead nitrate solution to the standard will overcome this difficulty. Reagents and Indicators.—This method presupposes the use of absolutely pure reagents, especially free from iron and cop- per. Use litmus paper as an indicator, as all other indicators, once introduced, will affect the final color. RED LEAD AND ORANGE MINERAL Schaeffer’s Latest Method * Moisture.—Dry 2 grams of the sample for 2 hours at 105° C. The loss will be moisture. * See Chemical Analysis of Lead and Its Compounds. Schaeffer, White and Calbeck. Pub. by The Eagle-Picher Lead Co., Joplin, Mo. 340 EXAMINATION OF PAINTS, VARNISHES AND COLORS Red Lead, or Lead Dioxide.t—Treat 1 gram of the sample in a beaker with 15 cc. of nitric acid, specific gravity 1.2 (110 ec. nitric acid, specific gravity 1.42, to 100 cc. of water. This solution should be aerated to free it from all nitrous fumes). Stir the sample until all trace of red color has disappeared. Add from a calibrated pipette or burette exactly 10 cc. of dilute hydrogen peroxide (1 part of 3-per-cent hydrogen peroxide to 3.5 parts of water). Add about 50 cc. of hot water and stir until all the lead dioxide has passed into solution. In the case of some coarsely ground oxides the contents of the beaker may have to be gently heated to effect complete solution. After the oxide has completely passed into solution, dilute with hot water to about 250 cc. volume and titrate directly with a standard potassium permanganate solution, having an iron value of 0.005. Titrate to the faint pink permanganate color. A blank titration on the hydrogen peroxide solution must now be made. Titration of Hydrogen Peroxide, and Calculation of Results.— Into a beaker pour 15 cc. of nitric acid having the strength as above given and add exactly the same amount of hydrogen peroxide (10 cc.). Dilute to 250 cc. with hot water and titrate with standard potassium permanganate to a faint pink color. The difference between the number of cubic centimeters of potassium permanganate required for the blank titration and the number required for the red lead titration is the amount of potassium permanganate required for the hydrogen peroxide which was reacted on by the lead dioxide. The difference be- tween the two amounts of potassium permanganate required multiplied by 3.058 gives the percentage of red lead present according to the following proportion: Let X = % Pb,O, per cc. difference 2 Fe:Pb,0, :: 0.005: X 112:685 :: 0.005: X X equals 3.058 To determine the lead dioxide present multiply this difference by 1.067 according to the following proportion: Let Y = % PbO, per ce. difference 2 Fe:PbO, :: 0.005 : Y 112 : 239 :: 0.005 - Y Y equals 1.067 iJ. Ind. Eng. Chem., 8, 237 (1916). oye a, ee ANALYSIS OF LEAD OXIDES 341 These calculations have been arrranged in a series So devised as to permit the direct’ reading of the red lead percentage. The basis of the calculations depends on the fact that each cc. of potassium permanganate solution (iron value, 0.005) is equiv- alent to 3.058 per cent of true red lead; or, each 0.1 cc. is equivalent to 0.3058 per cent true red lead on a one-gram sample. A red lead or orange mineral having 100-per-cent true red lead content requires 32.7 cc. potassium permanganate solution of the above strength. The calculation, therefore, arranges itself as follows: Each 0.1 cc. on the selected burette represents 0.3058 per cent true red lead. The number 32.7 being equivalent to 100 per cent occupies an analogous position on the chart. Calculations should be continued upward to 40.0 or to that point where the hydrogen peroxide solution used is of such strength that 10 cc. of the hydrogen peroxide solution require 40 ce. of the potassium permanganate solution. Calculations should be continued downward to 9.48 per cent true red lead content. In using the series the chart is attached to the burette by a serew clamp. The blank determination is first made on the hydrogen peroxide solution and the value found is placed op- posite zero on the burette. In the analysis of the red lead the value is then read off directly. As a hypothetical case we wili use a hydrogen peroxide solution with a blank titration of 34.1 ec. In the analysis of a red lead or orange mineral 4.2 cc. of the potassium permanganate solution is required for a final titration value. The calculation shows the difference between the two readings to be 29.9 cc. or multiplied by 3.058 equals a true red lead percentage of 91.48 per cent. Comparing this with the series of calculations we find 4.2 cc. from the 34.1 to be 91.43 per cent. Should it be preferred to determine the lead peroxide con- tent, the calculation will be based on the value 0.1067 for each 0.1 ce. of the potassium permanganate solution. It is under- stood that the division must be made to correspond to the 0.1 ec. divisions on the burette. It is always advisable to make several blank determinations each day when this analysis is constantly made and when only 342 EXAMINATION OF PAINTS, VARNISHES AND COLORS occasionally used a blank titration should be made before each — analysis. The strength of the hydrogen peroxide solution will vary but — the permanence of the permanganate solution renders the method accurate over a long period of time. Standard Potassium Permanganate.—It is necessary to al- — ways have a potassium permanganate solution with an iron value of exactly 0.005 if the method described for red lead is — used. Dissolve 5.75 grains c. p. salt in two liters distilled water — and store in a brown bottle in a dark place for a week or more. By this time all organic matter will have been oxidized and ~ after filtering the solution through an asbestos filter the solu- tion is ready for standardization. As small amounts of MnO, — destroy the permanence of this solution, it is necessary that it — be removed by filtering. The method described in Bureau of — Standards Circular No. 40 should be used. This method is as follows: In a 400-ce. beaker, 0.25 gram of sodium oxalate is dissolved — in 200 to 225 cc. of hot water (80-90° C.) and 10 ce. of (1:1) ~ sulphuric acid added. The solution is at once titrated with the — solution of permanganate, the solution being stirred continu- : cusly and vigorously. The permanganate must be added at the — rate of 10 to 15 cc. per minute and the last 0.5 to 1 ce. must be ~ added drop by drop, each drop being allowed to decolorize fully — before the next is added. The solution should not be below 60° C. by the time the titration is completed. With a perman- : ganate solution having an iron value of 0.005 per cc., 41.66 cc. of the permanganate are required to react with 0.25 gram sod- ium oxalate. If the first titration shows that the solution is too strong a small amount of distilled water should be added. To calculate exactly how much water to add divide 41.66 by the number cc. required in the titration and multiply by the number of cc. re- maining in the bottle. The difference between this product and the number of cc. in the bottle will be the volume of water to add. If the solution is too weak this difference multiplied by 0.00283 will be the grams of potassium permanganate salt to add. After the addition of water or salt the solution should again be titrated and if a titer of 41.66 is not obtained water or SO ee oa ee es i lita tain tg ANALYSIS OF LEAD OXIDES 343 salt added until this titer is obtained. A solution carefully pre- pared in this manner should keep for months. ANALYSIS OF FLAKE RED LEAD SCHAEFFER METHOD In certain instances it is found that flake red lead is soluble only with the greatest difficulty by the above procedure. In cases where this difficulty is encountered the following method will be found to give excellent results: Digest 1 gram of the sample in a beaker with 15 cc. of nitric acid made up of a strength as given in the previous method. Boil the solution for a short time, add 10 cc. of a standard oxalic acid solution, the strength of which has been previously de- termined. Add 2 cc. of sulphuric acid (1:1). Boil the solu- tion and titrate with a standard solution of potassium perman- ganate having an iron value of 0.005. A blank titration on the same amount of oxalic acid must be made. The difference be- tween the amount of potassium permanganate required for the blank titration and that required for the red lead titration multiplied by the factor 3.058 or 1.067 will give the content of red lead or lead dioxide according to the proportions in the. previous analysis. Iron—The iron should be determined colorimetrically as described under Red Lead. Copper.—This constituent may be determined gravimet- rically, or colorimetrically. By the gravimetric method twenty grams of the sample are treated in a large beaker with 50 cc. nitric acid, 25 cc. of water and sufficient hydrogen peroxide to cause complete solution of the lead dioxide. Determine the copper as outlined under the Analysis of Litharge. The colorimetric method described under Red Lead is, how- ever, more rapid and convenient. Silica.—Silica is found to be present in oxides of lead both as free silica and as lead silicate, though usually in inappreciable amounts. Digest 2 grams of the sample in a casserole with 2 grams of potassium chlorate and 15 cc. of dilute nitric acid. Proceed from this point as outlined under the Analysis of Litharge. 344 EXAMINATION OF PAINTS, VARNISHES AND COLORS Organic Color.—The adulteration of red lead and orange min- eral with organic coloring matter may be detected by adding | 20 cc. of 95 per cent alcohol to 2 grams of the oxide, heating to boiling and allowing to settle. Pour off the supernatant liquid, boil with water, allow to settle and add a very small amount of ammonium hydroxide. If either the alcohol, water or | ammonium hydroxide are colored, it indicates organic coloring matter. The quantitative determination is exceedingly difficult and the organic color is usually estimated by difference. ANALYSIS OF LITHARGE SCHAEFFER METHOD Litharge, the monoxide of lead, PbO, may contain small per- — centages of iron, copper, silica, silver and free metallic lead. When the litharge has been made by a process where steam is — used, there may be an appreciable amount of moisture present. It appears on the market in two colors, yellow and red. In some instances litharge is found containing a comparatively large percentage of red lead, which in certain uses is undesir- — able. The determination of each of the foreign constituents in litharge depends largely upon the use to which the litharge is to be put, as in very few cases are all the constituents determined. Moisture.—Dry 2 grams of the sample at 105° C. for two hours. The loss will be moisture. Free Metallic Lead.—Two grams of the sample are treated in a beaker with hot water and just sufficient acetic acid is slowly added, to dissolve the lead oxide. Stir the solution well and note whether any lead silicate remains undissolved. Should such remain, continue stirring until solution has been effected. The solution should never have greater than a 5-per-cent acetic acid strength. Filter the solution and wash the residual metal three or four times by decantation with hot water, having all the wash water pass through the filter paper, which is finally thoroughly washed with hot water. Transfer any metal on the filter paper to the beaker containing the residual lead, add 1 ce. of concentrated nitric acid and heat to solution. Dilute with 50 ec. of water, add 1 gram of sodium acetate and follow this with an excess of saturated neutral potassium bichromate solution, sufficient to precipitate all the lead. Boil, dilute to 100 cc., allow to cool, Ch, ae ee ae a NT [ae eae pe ee See, Ve ee ANALYSIS OF LEAD OXIDES 345 filter off the lead chromate, wash thoroughly and determine the lead chromate gravimetrically by drying at 100° C. or volumet- rically by titration of the chromic acid present as outlined un- der the analysis of Basic Sulphate of Lead. For the direct de- termination of lead in this case the factor to divide by is 2, as a 2-gram sample is used. Red Lead.—Determine the percentage of red lead present as outlined under the Analysis of Red Lead. Iron.—Treat 1 gram of the sample with 10 cc. of water and just sufficient nitric acid, added drop by drop, to cause com- plete solution. Heat to boiling to oxidize all the iron and de- termine it colorimetrically. Copper.—Copper may be rapidly and accurately determined by the method described on page 335. The following gravimetric method, however, may be found more convenient if only a few determinations are to be made. Twenty grams of the litharge contained in a 200-cc. flask are dissolved in nitric acid (50 cc. concentrated nitric acid to 100 ec. water). Boil to complete solution. Add 40 cc. of dilute sul- phuric acid (1:1), boil gently for one hour and allow to cool. Filter off the lead sulphate and wash the precipitate thoroughly. Nearly neutralize all the free acid present with ammonium hydroxide, render slightly acid with hydrochloric acid, warm the solution and pass in hydrogen sulphide until no further pre- cipitation of suphide occurs. Filter off the precipitate with- out washing, using some of the filtrate to transfer the last traces of sulphide to the filter paper. Dissolve the precipitate in a little nitric acid and wash the filter paper thoroughly with hot water. Add 8 cc. of concentrated sulphuric acid, evaporate until the white fumes of sulphuric acid are evolved and allow the solu- tion to cool. Add a little water and allow to stand for some hours. Filter off the lead sulphate, washing with hot water containing a little sulphuric acid. Heat the filtrate to boiling and precipitate the copper as sul- phide with hydrogen sulphide in an ammoniacal solution. Filter off the copper sulphide through an ashless filter paper, wash, ignite and weigh in a covered porcelain crucible, from which the heat and cover are occasionally removed for a few seconds. The precipitate will consist of a mixture of CuO and Cu,S. 346 EXAMINATION OF PAINTS, VARNISHES AND COLORS Since the percentage of copper is the same in both of these, the copper may be determined by multiplying the amount found by the factor 0.7988. Silica.—Digest 5 grams of the sample in a covered casserole ~ with 2 grams of potassium chlorate and 15 ec. of dilute nitric acid (1:1). Evaporate to dryness and dehydrate. Treat the residue, after cooling, with hot water and nitric acid. Heat to boiling, and filter the solution through an ashless filter paper. Wash the residue and filter paper thoroughly with hot acid ammonium acetate solution, made up to a strength as outlined on page 310. Should the residue show a trace of iron, wash it thoroughly with dilute hydrochloric acid. Complete the wash- ing with hot water, dry, ignite and weigh as SiO,. The residue may be volatilized with hydrofluoric acid, if there is any doubt regarding the purity of the silica. The silica is present as lead silicate and free silica. The above method determines the total content of silica. The free silica may be determined by dissolving the litharge in dilute nitric acid. Heat to boiling, filter, wash, ignite and weigh as silica. ON ee eee ee bs 3 ‘ ‘ CHAPTER XXXVII. ANALYSIS OF VERMILIONS The following portion of Walker’s* method, will suffice for the examination of Mercury Vermilion. Should the analyst desire to determine the sulphide of mercury present or make a more complete examination—reference may be made to the original method. True vermilion, or, as it is generally called, English ver- milion, is sulphide of mercury. On account of its cost it is rarely used in paints, and is liable to gross adulteration. It should show no bleeding on boiling with alcohol and water and no free sulphur by extraction with carbon disulphide. A small quantity mixed with five or six times its weight of dry sodium carbonate and heated in a tube should show globules of mercury on the cooler portion of the tube. The best test for purity is the ash, which should be not more than one-half of 1%. Make the determination in a porcelain dish or crucible, using 2 grams of the sample. Ash in a muffle or in a hood with a very good draft, as the mercury fumes are very poisonous. It is seldom necessary to make a determination of the mercury. Genuine mercury vermilion is at the present time little used in paints. Organic Reds.—Organic lakes are used for most of the bril- -jiant red, scarlet and vermilion shades. These organic coloring matters are sometimes precipitated on red lead, orange mineral or zinc oxide; but as a usual thing the base is barytes, whiting or china clay. Paranitraniline red, a compound of diazotized paranitraniline and beta-napthol, is largely employed; but a number of colors may be used. The examination of these reds follows the method as communicated to the writer by BE. F. Hick- son. Qualitative Tests for Reds.—In qualitatively testing ver- milions (para red, toluidine red, and lithol red) the following suggestions may be useful: (1) Para Red. The intense purple eolor in a mixture of alcohol (ethyl or denatured) and sodium hydroxide solution distinguishes para red from the other two. * P, H. Walker, Miscellaneous Publications, No. 15, U. S. Bureau of Standards, p. 32. 347 348 EXAMINATION OF PAINTS, VARNISHES AND COLORS oe eee (2) Toluidine and Lithol Reds. (a) Chloroform Test.—A small amount (0.1 g. or less) of C.P. toluidine red, when stirred into _ 100 ce. of warm chloroform, gives a practically clear, orange red Solution within one hour. Lithol red under the same conditions remains practically undissolved, even overnight, giving a nearly © colorless filtrate. (b) Sodium Carbonate.—C.P. toluidine red is 3 exceptionally resistant to strong alkalies and acids. A boiling solution of fairly strong sodium carbonate will have practically no effect on the bright orange red color of the toluidine, whereas the lithol red (barium lake), will be converted to the sodium _ salt; make both liquids slightly acid with dilute sulphuric acid and without filtering, place a piece of clean, freshly washed wool in each, and allow to remain for 10 minutes. Take each piece of wool and wash thoroughly with mild soap and water, taking ‘ care to wash off any absorbed pigment particles. The lithol dyes the wool a fast, uniform pink (coral) color that will not wash out; the toluidine does not dye the wool. Percentage of Pigment in Paste or Paint.—Weigh accurately — about 15 g. of the paste or paint into a weighed centrifuge tube. Add 20 to 80 ce. of petroleum ether, mix thoroughly with a glass rod, wash the rod with more of the petroleum ether, and add sufficient of the reagent to make a total of 60 cc. in the tube. Place the tube in the container of a centrifuge, surround with water, and counter-balance the container of the opposite arm with a similar tube or a tube with water. Whirl at a moderate speed until well settled. Decant the clear supernatant liquid. Repeat the extraction twice using petroleum ether. After draw- ing off the last extract, set the tube on top of a warm oven for 10 minutes, then in an oven at 110 to 115° C. for two hours. Cool, weigh, and calculate the percentage of pigment. Grind the pigment to a fine powder, pass through a No. 80 screen to remove any skins, and keep in a stoppered bottle. Analysis of Pigment.—Test the pigment first qualitatively. Place a small portion of the pigment in a 50 ec. beaker and add about 25 cc. of alcoholic KOH or NaOH. Para-red will turn a dark reddish purple. Pour off the colored solution, and repeat until all the color is in solution and a white base remains. Add a little HNO, to some of the base to show the presence of car- bonate. A white base, giving no effervescence or test for CO,, ee ee a ee ee ee ANALYSIS OF VERMILIONS 349 is probably composed of silicates or silicate and barium sulphate. Occasionally the base contains orange mineral; the addition of HNO, will turn this pigment brown and bleach out on adding a few drops of dilute NaNO, solution. Percentage of color.—wWeigh accurately about 0.5 g. portion of the pigment into a 250 cc. beaker, add about 100 ce. of warm chloroform, and stir with a glass rod, breaking up any lumps. Decant the colored solution through a weighed Gooch crucible, and leave the residue in the beaker. Add a 50 cc. portion of chloroform to the residue and stir well with a glass rod, break- ing up any lumps. Decant the colored solution through the Gooch crucible and repeat the washing of the residue in the beaker with 50 ce. more of chloroform. Finally transfer the residue onto the Gooch crucible, and continue the washing with chloroform from a wash bottle until the base is white or the washings colorless. Dry the Gooch crucible at 105-110° C. to constant weight and report the loss as “‘pure color.” NoTe.—In case the examination of the pigment shows calcium carbonate to be absent and the base to be barium sulphate and silicates, a direct loss on ignition using 1 g of the sample will generally check the above within 0.5 per cent. In case the base contains calcium carbonate, hydrated clays, alumina, etc., an ignition loss can not be calculated to organic color, since the results are too high, due to loss of combined water in the clay. The above method for percentage of color will give in most cases a base free from organic color with about 250-300 cc. of chloroform. Some samples have been washed with the following mixture for the percentage of color and satisfactory results were ob- tained: 10 vol. ethyl ether 6 vol. benzol 4 vol. methyl alcohol 1 vol. acetone Make alkaline with NaOH This is followed with alcoholic NaOH, alcohol and ether. In separating the pigment from the vehicle, petroleum ether has been found to dissolve out only a slight amount of organic color. 300 EXAMINATION OF PAINTS, VARNISHES AND COLORS Another suggested solvent for separating the pigment from vehicles is a mixture of two-thirds to three-quarters petroleum ether and one-third to one-quarter ethyl ether. Benzol or the mixed solvents mentioned above do not work well with some samples of vermilion paint. The reader is also referred to Fed- eral Specification Board Specification No. 66 for Red Knamel, in the back of this book. Ee ee ae a ae ee can eee CHAPTER XXXVIII. ANALYSIS OF INDIAN REDS, RED OXIDES (PRINCE’S METALLIC, TUSCAN RED, ETC.) Added Coloring Matter.—Test the pigment successively with hot water, 95 per cent ethyl alcohol, alcoholic NaOH or KOH and acetic acid. Chloroform, NaOH, H.SO, HCl-stannous chloride, and other reagents may be tried.* The presence of an organic color may often be noted by the characteristic odor given off on ignition. Loss at 100° C.—Heat 2 g. in a steam-jacketed oven at atmos- pheric pressure for three hours, or to constant weight. Loss on Ignition.—Ignite a portion in a covered porcelain crucible to constant weight. This may include combined water, CO.,, organic matter, and some SO, if much CaSO, is present. CO, may be determined on a separate portion of the sample if desired.t Free Acid or Alkali.mBoil 10 g. of sample with 100 cc. of water; filter and wash. Test filtrate with litmus paper; if acid, titrate with standard alkali and methyl orange and calculate to the equivalent of H,SO,. If alkaline, titrate with acid and cal- culate to the equivalent of Na,O. Test filtrate for alkali salts and alkaline earths. Insoluble, Iron Oxide, Etc.—Digest 2.5 g. of the sample (previ- ously roasted at a low temperature if much organic matter is present; if very low in carbonaceous matter a little KC1O, or NaClO, may be used in effecting solution) with 25 cc. of HCl (adding a little HNO, or chlorate, if not already added), wash off cover, and evaporate to dryness. Take up with HCl and water, filter, wash with dilute HCl and cold water. Make the filtrate up to 500 cc., mix, and examine as below.{ Ignite the * For details consult Zerr, “Tests for Coal-Tar Colors in Aniline Lakes,” (English translation by C. Meyer); Schultz and Julius, “A Systematic Survey of the Organic Coloring Matters’; Hall, “The Chemistry of Paints and Paint Vehicles”; and Mulliken, “Identification of Pure Organic Com- pounds,” Commercial Dyestuffs, Vol. III. + It is inadvisable to use platinum unless it is known that attacking sub- stances are absent. + For more exact work this filtrate should be evaporated to dryness and SiO. removed. 351 352 EXAMINATION OF PAINTS, VARNISHES AND COLORS - SS residue and weigh as “insoluble matter;’§ if this contains — BaSO, it may be determined by fusing with six times its weight — of Na,CO,, cooling, digesting with hot water, filtering, and wash- E ing the residue with hot water until free of sulfate. a Remove filtrate and place beaker used for the digestion under. oe neath the funnel, pierce the filter with the glass rod, and wash — the residue with a little water into the beaker; then pour hot — dilute HCl (1:1) over paper, and finally wash with hot water. ‘ If necessary add more HCI to the beaker to dissolve the BaCO,; heat to boiling, add dilute H,SO, in slight excess, let stand about one hour on steam bath; filter, wash, dry, ignite, and weigh BaSO,. (This subtracted from total insoluble will give “‘in- soluble silicious matter,” if it is desired to so report.) If it is desirable to analyze the insoluble silicious matter, this can be © done by the usual methods for silicate analysis, but the results 5 should be reported as a separate analysis. } A For the determination of iron place 100 ce. of the first filtrate in a flask, add about 3 g. of granulated zine, put a funnel into . the neck of the flask, heat when the action slackens; if basic — salts separate out add a few drops of HCl. When the reduction ¢ is complete, add 30 ec. of H,SO, (1:2), and as soon as the residual zine is dissolved, wash down the funnel inside and out and the neck of the flask with a fine jet of water, filling the flask (1000 ce.) about two-thirds full, cool in water, add 10 cc. of “titrating solution” (made by dissolving 160 g. of manganese sulfate in water, diluting to 1750 cce., adding 330 cc. of HeEvO} Sp. gr. 1.72, and 320 ce. of concentrated H,SO,), and titrate with KM..9,. (5.659 g. per liter) that has been standardized against Bureau of Standards sodium oxalate. Run a blank on the zine, correct for same and calculate total iron as Fe,O,. Instead of adding the zinc to the solution, the reduction may be effected in a zine reductor.* The Fe,0, may also be determined by the K,Cr,O, method. Lime.—Dilute an aliquot of 100 ce. of the original solution to about 200 ce., add 10 ce. of HCl, make alkaline with NH,OH, @ add 2 or 8 ec. of bromine water, and boil till excess of NH, is. .@ " Pee en) a eee en a ee § If the insoluble contains appreciable amounts of Fe it will be necessary — to fuse it with Na.CO, or K.S.0; to determine total Fe in samples. ee ‘§ Lord and Demorest, “Metallurgical Analysis,” 1918, pp. 28-29. ¢ Ibid., pp. 21-26. ANALYSIS OF RED OXIDES 300 expelled. Let settle, wash by decantation, redissolve in HCl, and reprecipitate with NH,OH and bromine water. (Precipi- y tate = Fe,O,.Al,0,.TiO, .P,0O,.MnO,.) This precipitate may be ignited and weighed if desired. To the combined filtrates add a few drops of NH,OH, heat to oiling, and add an excess of saturated ammonium-oxalate solu- - ion; continue the boiling until the precipitate becomes granular, ‘et stand about 30 minutes, filter, and wash with hot water till free of ammonium oxalate,* place beaker in which precipitation “was made under the funnel, pierce apex of filter with stirring rod and wash precipitate into beaker with hot water, pour warm dilute H,SO, (1:4) through paper and wash a few times; add about 30 cc. of H,SO, (1:4), dilute to about 250 cc., heat to 90° C. and titrate at once with standard KMn0O, solution (solution should not be below 60° C. when end-point is reached). Calculate to CaO. (The Fe value of KMnO, x 0.502 = CaO.) The calcium-oxalate precipitate may be ignited to constant weight as CaO. If desired, magnesia may be determined as Mg,P,0, in the usual manner in the filtrate from the calcium oxalate. t Soluble Sulfates.—Treat 1 g.t of the pigment (roasted gently if much organic matter is present) with 30 cc. of HCl, boil 10 © minutes, add about 50 cc. of water, boil, filter, and wash with hot water. Heat the solution to boiling, add NH,OH, filter and wash a few times with hot water; dissolve precipitate in hot dilute HCl and reprecipitate with NH,OH, wash well with hot water. Render united filtrates just distinctly acid with HCl, boil, add by drops with stirring excess of 10 per cent BaCl, solution, boil about 10 minutes, filter on a Gooch crucible, wash with hot water, ignite and weigh as BaSO,. Calculate to SO, or CaSQ,. Total Sulfur other than that Present as BaSO,.—Treat 5 g. of the sample in a covered porcelain dish with 50 cc. of aqua * For more exact work this precipitate should be dissolved in HCl and the calcium oxalate reprecipitated as above. 7 If desired, a direct determination of Al,.O; may be made on an aliquot of the solution or on the HCl solution of the NH.OH precipitate by Peters’ phosphate method (this will include titanic acid) as described by Blair, “The Chemical Analysis of Iron,” and Philips, “Methods of Iron Analysis Used in the Pittsburgh District.” ; {If low in soluble sulfates use a larger portion of sample. ; ’ 354 EXAMINATION OF PAINTS, VARNISHES AND COLORS regia (LHNO,:9 HCl) and evaporate to dryness on steam bath. Add 20 ec. of concentrated HCl and about 250 cc. of water, make double NH,OH precipitation; determine BaSO, as given under “Soluble Sulfates.”’ Cuprous Oxide Red in Antifouling Paints.—The red cuprous oxide used in antifouling paints can be analyzed in accordance with the following method. Weigh accurately about 0.25 g. of — the dry sample into a 250-ce. ground glass stoppered Erlenmeyer flask. Add 10-15 cc. of acid ferric chloride solution (200 g. FeCl,. 6 H,O in 500 cc. of 1:1 HCl), and a few glass beads, stop- — per, and rotate until the oxide is completely dissolved (usually within 2 or 3 minutes on high-grade finely ground samples). Warm on the steam bath, if necessary, but it is not advisable and generally unnecessary. Add 5 cc. of syrupy phosphoric acid, 200 cc. of cool distilled water, and titrate the ferrous iron with decinormal KMn0O, to the first permanent (30 seconds) color change. A blank (usually about 3 drops) should be run on the reagents. 1 cc. O. 1 N KMn0O, = 0.00636 g. Cu. = 0.00716 Cu,O CHAPTER XXXIX. ANALYSIS OF OCHERS (SIENNAS, UMBERS, ETC.) Loss at 100° C., loss on ignition, insoluble matter, total or soluble iron, alumina, lime and sulfur may be determined as outlined under the ‘‘Methods for Analysis of Indian Reds, etc.,” using 1 g. or an aliquot corresponding to this weight. Lead Chromate.—If present, the lead is removed in the above scheme by nearly neutralizing the filtrate from the insoluble matter with NH,OH, cooling, and passing in H.S, to precipitate PbS. Filter, wash with water, containing H.S, dissolve PbS in hot dilute HNO,, add 10 cc. of concentrated H,SO,, evaporate till SO, is evolved, cool, dilute to 200 cc., let stand a few hours, filter on a Gooch crucible, wash with 1 per cent H,SO,, ignite, and weigh PbSO,. Calculate to PbO or Pb. Heat the filtrate from the PbS to expel H,S, oxidize with a little HNO., and make up to volume if working on more than 1 g. The iron is best determined in an aliquot by the K,Cr.,O, method. Another aliquot is treated with NH,OH, the precipi- tate containing AI,O,.Fe,0,.Cr,0;.P,0,.TiO,. Lime and MgO may be determined in filtrate. | The NH,OH precipitate is dissolved in hot dilute HCl, wash- ing paper with hot water, cooled, oxidized with Na,O., boiled to expel H,O,, cooled, cover glass washed off, diluted to about 150 cc., and acidified with H,SO,. Add a measured excess of ferrous ammonium-sulfate solution — (NH,),Fe(SO,).,.6H,O, 12.4 g.; concentrated H,SO,, 50 cc.; and water to make 1 liter, and titrate back with standard K,Cr,O, solution to determine its value in terms of the latter. The Fe value of the K,Cr,O, solution « 0.5969 = CrO.. Or, moisten 1 g. of the pigment with water, add 5 cc. of con- centrated HCl, boil a few minutes, cool, add Na,O, in excess, boil to expel H,O., cool, wash off cover glass, dilute, acidify with H.SO,, and titrate CrO, as above. ANALYSIS OF VENETIAN RED Analyze as given under “‘Method for Analysis of Indian Reds, etc.” Insoluble matter may be treated with HF and H.SO, to determine SiO, by loss if desired. 355 356 EXAMINATION OF PAINTS, VARNISHES AND COLORS ANALYSIS OF SIENNAS AND UMBERS After gently roasting to destroy organic matter, test as given under “Methods for Analysis of Indian Reds, etc.” Manganese.—Manganese is determined by the bismuthate | method.* Ignite gently (to destroy organic matter) 1 g. of the © sample in a platinum dish, cool, add 10 cc. of water, 4 cc. of concentrated H,SO, and about 20 cc. of HF (if necessary, add — a little sulfurous acid). Evaporate until the H,SO, fumes freely, — cool and dissolve in 25 ec. of HNO, (1 part concentrated HNO, to 3. parts water). If no appreciable residue remains, transfer — to a 100-cc, volumetric flask, using 25 ec. of HNO, (1:3) to — rinse the dish, dilute to the mark with water, mix thoroughly. — If there is an appreciable residue, filter on a small filter, wash with water, ignite residue in a platinum crucible, and fuse with a little sodium or potassium pyrosulfate. Dissolve in water, with the addition of a little HNO,, add to the main filtrate, evaporate nearly to dryness, take up in HNO, (1:8) and trans- fer to the flask as before. Pipette an aliquot of 10 cc. into a 200-cec. Erlenmeyer flask, add 30 cc. of water and 10 cc. of con- centrated HNO., sp. gr. 1.4; add about 0.5 g. of sodium bis- muthate, heat for a few minutes, or until the pink color has dis- appeared with or without the precipitation of MnO,. Add a few small crystals of sodium or potassium nitrate to dissolve — the MnO, and boil the solution several minutes to expel nitrous fumes (a little Na,CO, will aid this). Add water to bring the volume up to 50 cc. and cool to about 15° C.; add about 0.5 g. — of bismuthate and shake the flask well. Add 50 cc. of water containing 30 cc. of concentrated HNO, to the liter, filter by suc- tion through an asbestos felt into a 300-cc. Erlenmeyer flask and wash with 50 to 100 cc. ofthe same acid. Run in a meas- ured volume of standard ferrous ammonium-sulfate solution and titrate to a faint pink color with standard KMnO, solution. The number of cubic centimeters of the KMnO, solution obtained, subtracted from the number corresponding to the volume of ferrous solution used, will give the volume of KMnO, equivalent to the manganese in the sample, which, multiplied by the value of the KMnO, in Mn, gives the weight of manganese in the por- tion of sample used. * Blair, “The Chemical Analysis of Iron.” OCHRES 357 Standard KMnO, Solution —tThe solution of KMnO, is com- posed of 1 g. dissolved in a liter of water. The Fe value of this solution X 0.1968 = Mn. This solution may be _ standardized against Bureau of Standards sodium oxalate (using about 0.05 to 0.1 g.)* Weigh of Na,C,O, x 0.1639 = Mn. Twelve grams of (NH,).Fe(SO,),.6H,O, 25 cc. of concentrated H,SO,, and 25 cc. of H,PO,, sp. gr. about 1.7, are made up to 1 liter with water. The value of this solution should be determined against the KMn0O, each day as follows: Measure into a 200-cc. Erlenmeyer flask 50 cc. of HNO, (1:3), cool, add a little bismuthate, dilute with 50 cc. of 3-per- cent HNO.,, filter by suction through an asbestos felt into a 300-cc. Erlenmeyer flask, and wash with 50 cc. of 3-per-cent HNO,. Run in 25 ec. of the ferrous solution and titrate with KMn0O, solution. Instead of titrating the permanganic acid formed by the bismuthate with the ferrous solution and then titrating back with KMn0O,, a direct titration with standard sodium arsenite solution may be made.t *W. Blum, “Original Communications, Eighth International Congress of Applied Chemistry,” Vol. I, pp. 61-85. + Lord and Demorest, “Metallurgical Analysis,” 1913, p. 82. CHAPTER XL. ANALYSIS OF YELLOW. AND ORANGE PIGMENTS CHROME YELLOWS, AMERICAN VERMILION, BASIC LEAD CHROMATE A pure chrome yellow should contain only lead chromate and . other insoluble lead compounds. Added Coloring Matter.—Test the pigment successively with hot water, 95-per-cent ethyl alcohol, and chloroform. The solu- tions should remain colorless. Other reagents may be tried.* Moisture.—Heat 2 g. at 105° C. for two hours. The loss in weight is reported as moisture. Insoluble Matter.—Treat 1 g. with 25 cc. of concentrated HCl and boil for from 5 to 10 minutes in a covered beaker adding about 6 drops of alcohol to the boiling liquid, one at a time. Dilute to 100 cc. with hot water and boil for from 5 to 10 min- utes (the solution should be complete). Filter the hot solution (if insoluble matter is present) and wash with boiling water till washings are free from lead and chlorine. Ignite the insolu- ble matter, weigh, and examine for SiO,, BaSO,, and Al1,O,. | Total Lead.—Nearly neutralize with NH,OH the filtrate from the insoluble matter (or the original solution), dilute to about 300 cc., and pass into the clear solution a rapid current of H,S until all of the lead is precipitated as PbS. Let the precipitate settle, filter, wash with water containing some H.S. Boil the filter and precipitate with dilute HNO, until all of the lead has ~ dissolved, filter, and wash thoroughly with hot water. To the — filtrate, add 10 cc. of H,SO, (1:1), evaporate until copious fumes of SO, are evolved, cool, add about 75 cc. of H,O and then 75 ec. of 95-per-cent ethyl alcohol. Let stand about one hour, — filter on a Gooch crucible, wash with dilute alcohol, dry, ignite, and weigh as PbSO,. Chromium (Iron, Aluminum) .—Heat the filtrate from the PbS to expel H.S and, if iron is present, add a few drops of * For details consult Zerr, “Tests for Coal-Tar Colors in Aniline Lakes” (English translation by C. Mayer) ; Schultz and Julius, “A Systematic Sur- vey of the Organic Coloring Matters’; Hall, “The Chemistry of Paints and Paint Vehicles”; and Mulliken, “Identification of Pure Organic Compounds,” Commercial Dyestuffs, Vol. ITI. 358 ORANGE AND YELLOW PIGMENTS 359 HNO, and boil about two minutes. Render the solution just alkaline with NH,OH, boil a few minutes, filter, and wash with hot 2-per-cent NH,Cl solution. (If the sample contains an appreciable amount of zinc, a double precipitation should be made.) In the absence of iron and aluminum this precipitate may be ignited and weighed as Cr,O,. If iron and aluminum are present, dissolve the NH,OH precipitate with hot dilute HCl, washing the paper with hot water; cool, add NH,OH until alka- line, and then add Na,O, (about 1 g.), keeping the beaker cov- ered. Digest until all of the chromium and aluminum have been dissolved, adding more Na,O, if necessary. Filter off the Fe(OH),, wash thoroughly with hot water, ignite and weigh as Fe,O,; or, dissolve the precipitate in HCl and determine the Fe content volumetrically. Make up the filtrate from the Fe(OH), to 250 ce. in a graduated flask, and mix. Render an aliquot portion acid with H,SO,, boil to expel any free oxygen, cool, add an excess of standard (NH,).Fe(SO,)..6H,O solution and titrate back with N/10 K,Cr,0, solution, using K,Fe(CN), as outside indicator. (The CrO, may also be determined by acidifying the aliquot portion with acetic acid, precipitating as PbCrO, or BaCrO,, and finally weighing on a Gooch crucible.) To determine Al,O,, make an aliquot portion of the filtrate from the Fe (OH), acid with HCl, and then just distinctly alkaline with NH,OH, heat to boiling, let settle, filter, wash with hot 2- per-cent NH,Cl solution, ignite and weigh as Al,O,. If iron and aluminum are not to be determined or are present in negligible amounts, the first NH,OH precipitate may be dissolved in dilute HCl, oxidized with Na,O., acidified with H,SO,, boiled, and CrO, determined volumetrically. The CrO, in the absence of other Oxidizing substances, may be determined on 1 g. of the pigment by Schwartz’ method (Fresenius Quantitative Chemical An- alysis, Ed. 6, Vol. 1, p. 424). Zinc, Calcwm, and Magnesium.—Precipitate any zinc in the filtrate from the first NH,OH precipitate with H,S, filter, wash with dilute (NH,).S, dissolve the zine sulfide in dilute HCl, and determine the Zn content volumetrically by K,Fe(CN), method. In the filtrate from the zine sulfide, determine calcium by the oxalate method and magnesium as Mg.,P.0.. Sulfuric Anhydride.—Heat 1 g. of the pigment with 10 cc. of concentrated HCl until free chlorine is expelled, add about 300 360 EXAMINATION OF PAINTS, VARNISHES AND COLORS ec. of water and boil; filter off any insoluble matter and wash thoroughly with hot water, heat to boiling, and precipitate with BaCl, solution in the usual manner. Keep the solution hot while filtering off the BaSO, and wash with hot water until the wash- ings show no lead or chlorine. Carbon Dioxide.—Determine carbon dioxide by the evolution method, using dilute HNO.,, free from oxides of nitrogen. Water-Soluble Matter.—Weigh 5 g. of the pigment on to a weighed Gooch crucible (containing asbestos, and dried at 110° C.), wash six times with 25-cc. portions of cold water; dry at 110° C. and weigh. The loss in weight, corrected for moisture (as determined above), represents the soluble salts removed by the water. The washing may be examined, if desired. Calculations.—Calculate CrO, to PbCrO,, and SO, to PbSO, if calcium is absent. If CO, is present and calcium and man- nesium are absent, calculate to (PbCO,),.Pb(OH).. Report any residual Pb as PbO. If calcium is present, calculate to CaCO, if CO, is also present. If calcium and SO, are present and CO, is absent, calculate to CaSO,. If calcium, CO,, and SO, are present, calculate to CaCO,; any residual calcium is then calculated to CaSO,. Report zinc as ZnO. CADMIUM LITHOPONE This pigment is a chemically precipitated pigment containing approximately 68 per cent barium sulphate, the balance consist- ing principally of yellow cadmium sulphide with some zinc sul- phide. It is not affected by hydrogen sulphide. For moisture, water soluble, total sulphides, and oxides, see methods for litho- pone. Method for Cadmium and Zine Sulphides.—Take 1 gram of the sample in a 200 cc. beaker, add 15 cc. of concentrated HCl, mix, and add in small portions about 1 g. KCIO,, then heat on the steam bath until about half of the liquid is evaporated and the yellow color of the CdS has disappeared. (If necessary, a few ce. of concentrated HNO, may be added at this point to ef- fect the solution of the CdS.) Then add 15 ce. of 1-1 sulphuric acid and evaporate to fumes of SO,. Cool, dilute with 100 cc. of water, filter off, and weigh the insoluble barium sulphate and examine it for alumina and silica (not likely to be present). To the filtrate from the insoluble, add water until volume is 200 cc. Cool and pass a rapid stream of H,S gas through the so ORANGE AND YELLOW PIGMENTS 361 lution for 15 minutes. Add dilute NH,OH, drop by drop until yellow cadmium sulphide begins to precipitate. Heat the solu- tion to about 90° C. and again pass H.S for five minutes. Boil the solution for a few minutes, let settle, and filter through close- grained paper, washing the precipitated CdS with cold 10% sul- phuric acid and with hot water. Save filtrate for zinc. Dissolve the sulphide on the filter in 1-2 HCl in a clean beaker, add 15 cc. (1-1) sulphuric acid, take to fumes, and repeat pre- cipitation of CdS. Filter through weighed Gooch crucible, wash with 10% sulphuric acid and hot water, dry at 110° C. for one hour, and weigh as CdS. Combine the two filtrates from the CdS precipitation cool thoroughly, make slightly alkaline with NH,OH, and pass a rapid stream of H,S gas for ten minutes. Heat to boiling, let settle, filter on fine-grained paper, wash well, and ignite carefully in crucible to ZnO. Factor ZnO to ZnS = 1.1975. CHAPTER XLI. ANALYSIS OF BLUE PIGMENTS IRON CYANIDE BLUES. (PRUSSIAN BLUE, CHINESE BLUE, ANTWERP BLUE, MILORI BLUE, BRONZE, BLUE, STEEL BLUE.) The analysis of these blues, as is generally the case with pig- ments, does not necessarily give results which can be used to grade samples, the strength and color tests being most impor- tant. Movrsture.—Heat 2 g. of the pigment at 105° C. for two hours. The loss in weight is reported as moisture. A “dry” Prussian blue should contain less than 7 per cent of moisture. Insoluble Matter.—Ignite 1 g. of the pigment in a porcelain dish at a low temperature, just high enough to decompose the last. trace of blue, but not high enough to render the iron diffi- cultly soluble in HCl. Cool, add 15 cc. of HCl and a few drops of bromine, cover with a watch-glass, and digest on the steam bath; wash off cover, evaporate to a syrup, add water, boil, filter, wash with hot water, ignite the residue and weigh. Examine the insoluble residue for silica, barium sulfate, and alumina. A pure Prussian blue should show no insoluble residue. Iron and Aluminum.—Determine iron and aluminum in the filtrate from the insoluble matter by precipitation with NH,OH in the usual manner. A double precipitation is desirable. Ignite and weigh Fe,0,-+ Al,O,, deduct Fe,O, (calculated from total Fe), and calculate Al,O, to Al. Calcitum.—Determine calcium in the filtrate from the Fe,0, + Al,O, by precipitation with ammonium oxalate ; titrate with KMn0O,, or, ignite and weigh as CaO. Acidify the filtrate from the calcium oxalate with HCl and dilute to a definite volume and mix. Sulfuric Acid.—Determine sulfuric acid in an aliquot of the above solution as BaSO, in the usual manner. Alkali Metal and Alkaline Salts.—Evaporate an aliquot of the above solution with sulfuric acid, ignite (treating with solid ammonium carbonate), and weigh. Determine whether the alkali metal is sodium or potassium and subtract the alkali metal 362 Oa BLUE PIGMENTS 363 corresponding to the sulfate (SO,) found. The remainder is alkali combined with the blue and is reported as Na or K. Total Iron—Decompose and dissolve 1 g. of the pigment as. under “Insoluble Matter,” reduce, and determine the total iron with KMnO, or K,Cr,0,. There should be not less than 30 per cent, calculated on the dry pigment. Total Nitrogen.—Determine the total nitrogen on a 1-g. sam- ple of the pigment by the Kjeldahl-Gunning Method, digesting for at least 214 hours. The sulfuric acid should not blacken, which would indicate organic adulteration. Water-Soluble Matter.—Weigh 2.5 g. of the pigment into a graduated 250-cc. flask, add 100 cc. of water, and boil for five minutes. Dilute with water, let stand until at room tempera- ture, make up to mark, mix and let settle. Filter through dry paper and discard the first 25 cc. Transfer 100 cc. of the clear filtrate to a weighed dish, evaporate to dryness on a steam-bath, ary in-an oven at 105° C. for 30 minutes, cool and weigh. Calculations —The percentage of Prussian blue may be ob- tained with sufficient accuracy for commercial purpuses by mul- tiplying the percentage of nitrogen by 4.4 or the percentage of iron (in the absence of other iron pigments) by 3.03.* NoTEe.—Some blues, e. g-, Chinese blue, may contain tin salts. Others may contain manganese or chromium compounds. The presence of these compounds should be determined by a qualitative examination at least. Heckel Method for Iron in Prussian Blue.—In a method for the examination of Prussian blue, worked out by James E. Heckel, the sample is heated in an open crucible, gently at first and later with strong heat. The contents of the crucible are then brushed into a beaker, also placing the crucible in the beaker if any of the Fe,O, clings to it. Heat with 25 cc. con- centrated HCl and add 3 cc. SnCl,. In about fifteen minutes solution is complete. If the crucible has been placed in the beaker, remove it after rinsing with distilled water into the beaker, and transfer the solution to a 500-cc. flask, washing out all FeCl, from beaker. Make up to mark with distilled water. Concentrate a 100-cc. aliquot portion and reduce with SnCl.. Stir constantly, adding the material, drop by drop, from a burette until apple-green color is produced—from chrome- oxidized blues. For chlorate-oxidized blues, the SnCl, is added * Parry and Coste, The Analyst, Vol. 21, pp. 225 to 230 (1896). 364 EXAMINATION OF PAINTS, VARNISHES AND COLORS until complete disappearance of the yellow color. At once pour in 50 ce. cold HgCl, and 50 ec. MnSO,, dilute with cold distilled water to about 600 cc. and titrate with KMnO,. For those in- terested in this method, see files of Drugs, Oils and Paints. ANALYSIS OF ULTRAMARINE BLUE An analysis is of little value for determining the quality of pure ultramarines, but is useful in the identification of foreign admixtures. Practical tests as to the stability and compatibil- ity of the pigment in mixtures with other pigments, coloring power, tint, fineness, fastness to light, etc., are more important than chemical analysis. Moisture.—Heat 2 g. of the pigment at 105° C. for two hours, cool and weigh. The loss in weight is reported as moisture. Silica.—Treat 1 g. of the pigment in a covered dish or cas- serole with 30 cc. of HCl (1:1), heat until decomposed, wash off and remove cover, and evaporate to dryness on the steam- bath. Moisten with concentrated HCl and again evaporate to dryness, add 1 to 2 cc. of concentrated HCl, let stand about 5 minutes, add hot water, filter and wash the insoluble matter with hot water. If great accuracy is desired, evaporate the filtrate to dryness, take up with HCl and water, filter on a second paper, wash, and add the residue to the main insoluble. Ignite the insoluble matter, cool and weigh. Determine SiO, by volatilization with H,SO, and HF. Make a qualitative examina- tion of any residue that may remain. Alumina.—Render the filtrate from the silica faintly alkaline with NH,OH, boil a few minutes, filter, wash with hot 2-per- cent NH,Cl solution, ignite and weigh as Al,O,( + Fe,0,). For more accurate work, dissolve the Al(OH), precipitate in HCl and reprecipitate as above. Sodium Oxide—Acidify the filtrate from the Al,O, with H.SO,, evaporate to dryness, ignite (finally adding solid am- monium carbonate) and weigh as Na,SO,. Calculate to Na,O. If calcium is present it should be precipitated with ammonium oxalate in the filtrate from the Al,O,, ignited and weighed as CaO, and the sodium determined in the filtrate from the calcium oxalate, as described. . Total Sulfur.—Mix 1 g. of the ultramarine with 4 FOOL Na,CO, and 4 g. of Na,O, in a nickel crucible, cover with about 1 BLUE PIGMENTS 365 g. of Na,CO, and fuse, using an aluminum or asbestos shield to prevent the sulfur being taken up from the gas. Dissolve the fused mass in dilute HCl, filter and wash, if necessary (there should be no insoluble residue), precipitate with BaCl, and de- termine total sulfur by weighing as BaSO,. Calculate to S. Sulfur Present as Sulfate——Dissolve 1 g. of the pigment in dilute HCl, boil to expel H.S, and filter if necessary; make the solution faintly alkaline, with NH,OH and just distinctly acid with HCl, and treat with BaCl, in the usual manner. Calculate BaSO, to SO, and to S. Sulfur Present as Sulfide-—Subtract the sulfur present as sulfate from the total sulfur. ANALYSIS OF COBALT BLUE This pigment is essentially a compound of the oxides of alum- inum and cobalt.* Certain shades of ultramarine blues are often sold under the name “cobalt blue.” Moisture.—Heat 2 g. of the pigment at 105° C. for 2 hours. The loss in weight is reported as moisture. Alumina.—Fuse 1 g. of the pigment with 12 to 15 g. of sodium or potassium pyrosulfate cool, digest with water and HCl, filter, and wash the residue with hot water. Make the filtrate up to 250 cc. in a graduated flask and mix. Ignite the residue, cool, weigh, and examine for SiO, and BaSO,. Dilute an aliquot portion of the filtrate to 200 cc., add 5 g. of NH,Cl, heat to boil- ing, and add dilute NH,OH till just distinctly alkaline (a few drops of 0.2-per-cent alcoholic solution of methyl red is recom- mended as indicator). Boil for one or two minutes, filter at once, dissolve the precipitate with HCl, and reprecipitate as before. Filter, wash thoroughly with hot 2-per-cent NH,Cl (or NH,NO,) solution, ignite, and weigh as AI,O.,. Calcium and Magnesium.—Unite the filtrates from the AI,O,, saturate with hydrogen sulfide, filter, and determine calcium and magnesium in the filtrate in the usual manner. Cobalt Oxides.—Subtract the determined constituents from 100 and report the difference as cobalt oxides, unless a qualita- tive examination shows the presence of other substances in sig- nificant amounts. Should the pigment contain phosphoric acid (or arsenic acid) in more than negligible amounts, these must * “ Analysis of Paint and Varnish Products,” C. D. Holley, p. 210 (1912). 366 EXAMINATION OF PAINTS, VARNISHES AND COLORS be removed before determining aluminum, calcium and mag- nesium.t ANALYSIS OF SUBLIMED BLUE LEADT BASIC SULPHATE—BLUE LEAD Total Lead.—The total lead content is determined by the vol- umetric method for lead as outlined under Basic Sulphate-White Lead. Total Sulphur.—Treat 0.5 gram with 10 cc. of water and a few ec. of bromine water. Boil gently until all the bromine has passed off. Dilute with water, add another portion of bromine water, boil, and continue the treatment until the sediment has become white in color. Add 8 cc. of nitric acid, evaporate until the brown fumes of nitric acid have disappeared, dilute with water and add an excess of sodium carbonate. Determine as outlined under Basic Sulphate-White Lead. Lead Sulphate-—On a separate sample determine the lead sulphate as outlined under Sublimed White Lead, by transposi- tion of the sulphate with sodium carbonate. Lead Sulphite.—Boil one and one-half: grams of the sample with 3 grams of sodium carbonate, allow to stand, filter and thoroughly wash. To the filtrate add 3 cc. of bromine water, heat gently to oxidize the sodium sulphite to sulphate, acidify with HCl and precipitate the sulphate with barium chloride. Filter, wash and weigh in the usual manner. The barium sul- phate formed will contain both the sulphur present as sulphate and that present as sulphite converted to sulphate. Deduct the amount present as sulphate and calculate the remainder to lead sulphite. Lead Sulphide.—Deduct the sulphur present as sulphate and sulphite from the total sulphur and report the difference as lead sulphide. Lead Carbonate.—A small amount of lead may be present as carbonate. Determine the carbonic acid present as outlined under Basic Carbonate White Lead, and calculate this carbonic acid to lead carbonate. Lead Oxide.—Deduct the lead present as lead sulphate, lead ae tee } sNora ieiay eee of Chemical Analysis,” Lunge-Keane, Vol. III, t “The Chemical Analysis of Lead and its Compo . White, pp. 22-24, mpounds,” Schaeffer and BLUE PIGMENTS 367 sulphite, lead sulphide and lead carbonate from the total lead and report the difference as lead oxide. Zine Oxide—Determine the zine present as outlined under Sublimed White Lead, and report it as Zine Oxide. Carbon and Volatile Matter—lIgnite the sample in a partially covered crucible at a low heat for two hours. Report the differ- ence as carbon and volatile matter. CHAPTER XLII. ANALYSIS OF GREEN PIGMENTS (CHROME GREEN) A pure chrome green should contain only Prussian blue and pure chrome yellow. A microscopic examination should be made to determine whether the green is a combined precipitation product, which is of the greater value, or one mixed after sep- arate precipitation. A good green will show the presence of green and blue particles, while a poor green will show yellow and blue particles mixed with green. . Moisture.—Heat 2 g. of the pigment at 105° C. for two hours. The loss in weight is reported as moisture. Insoluble Matter.—Heat gently 1 g. of the pigment in a small porcelain dish until the blue color has been decomposed. The heating should be carried out very carefully so as not to render the iron difficultly soluble. (With some very pure chrome greens it may be advantageous to mix the sample with 2 to 5 times its weight of pure barium sulfate or pure anhydrous sodium car- bonate before igniting.) Let cool, transfer to a beaker, and de- termine insoluble matter as outlined in Section 5 for Yellow Pigments. Lead.—Determine lead in the filtrate from the above as out- lined in Section 6 for Yellow Pigments. Iron, Alumina and Chromium.—Determine iron, aluminum > and chromium in the filtrate from the PbS as outlined for Yel- low Pigments, making a double precipitation. Zinc, Calcium, and Magnesium.—Determine zinc, calcium and magnesium in the filtrate from the iron, aluminum and chrom- ium determination as outlined for Yellow Pigments. Carbon Dioxide.——Determine carbon dioxide by the evolution method, using dilute HNO, (1:5). Sulfuric Anhydride.—Heat gently 1 g. of the pigment, cool, transfer to a beaker, add 30 ce. of concentrated HCl, cover, and heat on a steam-bath for about 30 minutes (in some cases, the iron compounds will go into solution more readily by letting the solution stand for some time at room temperature and then heat- ing). Wash off cover, add 50 cc. of boiling water, boil for five 368 GREEN PIGMENTS 369 minutes, filter, render the filtrate faintly alkaline with NH,OH, then slightly acid with HCl, heat to boiling, and precipitate with BaCl, (15 cc. of 10-per-cent solution) in the usual manner, boil- ing about ten minutes. Filter, wash with hot water, ignite, and weigh the BaSO,,. Nitrogen.—Determine nitrogen on a l-g. portion of the pig- ment by the Kjeldahl-Gunning Method, digesting for at least 214 hours. Water-Soluble Matter.—Weigh 2.5 g. of the pigment into a graduated 250-cc. flask, add 100 ec. of water, and boil for five minutes. Dilute with water, let stand until at room tempera- ture, make up to the mark, mix, and let settle. Filter through dry paper and discard the first 25 ec. Transfer 100 cc. of the clear filtrate to a weighed dish, evaporate to dryness on a steam- bath, dry in an oven at 105° C. for 30 minutes, cool and weigh. CHAPTER XLIII. ANALYSIS OF BLACK PIGMENTS The black pigments include those which contain carbon as their essential constituent. The introduction of asphaltic and coal-tar mixtures complicates their chemical analysis. For those pigments which contain coal-tar mixtures, recourse may be had to works* covering this matter thoroughly. The analysis of the simple black pigments may be carried out in the following way: Moisture.—Dry 2 grams at 105° C. for two hours. Oil.— Extract 2 grams, with ether in a fat-extraction ap- paratus. Carbon.—Determine the carbon by difference after determin- ing the moisture, oil and ash. For an exact determination of carbon make a combustion test, absorbing the carbon dioxide in soda-lime or caustic potash as usual. Ash.—Ignite 2 grams to a bright red heat until all the carbon is driven off. If graphite is present, the ignition should be car- ried out with the aid of oxygen. Should carbonate be present, mix the ash with a small amount of ammonium carbonate and again ignite, thus reconverting to carbonate any oxide which may have been formed. Analysis of Ash.—The ash is boiled with concentrated HCl and the insoluble residue determined in the usual manner. The filtrate is examined for calcium, magnesium and phosphoric acid. Calculate the magnesium to phosphate, any residual phos- phoric acid to calcium phosphate and any residual calcium to carbonate. Gases.—Black pigments such as lamp or gas blacks may con- tain as high as 15 per cent absorbed or adsorbed gases. High vacuum is necessary to free such gases from the pigment. * Allen’s “Commercial Organic Analysis,” 4th Edition; “The Analysis of Paints,” Gardner and Schaeffer. 370 INDEX A Accelerated roof expusure tests, 197 Accelerated testing cabinets, 71 Accelerated testing vs. exterior ex- posure, 76 Accelerated weathering test chart, 74 Acetone in lacquer, 287 Acid number of varnishes, 246 Acid resins, 262 Acid test, 279 Acidity, Effect of on light resist- ance, 123 Acidity of lacquers, 285 Air-liquid tension, 155 Alkali resistance test, 279 Aluminwm oxide in aluminum stear- ate, 190 Aluminum stearate, 181 Aluminum stearate solutions, 186 American Society for Testing Ma- terials tests on insulating varnishes, 276 American Society for Testing Ma- terials tests on shellac, 267 American vermilion, 358 Analysis of aluminum stearate, 191 bituminous paints, 296 driers, 255 paints, 213 - paint oils, 218 paint vehicles, 213 pyroxylin coatings, 283 resins, 258 white paint, 304 et seq. Anthraquinone tests, 302 Antifouling paints, 208, 204, 354 Antimony oxide, 304, 327 Apparatus for oil absorption, 108 specific gravity, 84 testing shellac, 275 Abestine analysis, 327 Ash in varnishes, 246 Asphalts, 301 Asphalt tests, 301 B Barium carbonate, 304 Barytes analysis, 329 Basic chromate yellows, Analysis of, 358 Bending test of films, 13 Benzol, 289 Benzol in paints, 217 Bituminous cement, 293 japans, 295 paints, 293 Analysis of, 296 varnish, 293 Black pigments, 370 Blanc fixe analysis, 329 Bleached shellac, 272 Blue pigments, 362 Blown oil test on thinners, 178 Boiled linseed oil, Constants of, 219 Bone dry shellac, 272 Brightness and hiding power of pig- © ments, 28, 24, 28 Brightness of white pigments, 210 Bulking values of colors, 89 paint liquids, 88 pigments, 89 C Cadmium lithopone, 360 Calcium pigments, Analysis of, 328 Calculating analysis of lead pig- ments, 315 Camphor in lacquer, 289 Candlenut oil constants, 219 Caramel solutions, Color strength of, 166 Carbon dioxide apparatus, 307 Catfish oil constants, 220 Celluloid in varnish, 254 Cellulose acetate in varnish, 254 nitrate in varnish, 254 stability, 292 371 372 INDEX Te ———ee—e_e—_e_—_—_—eeeeeeee Chemical examination of aluminum stearate, 188 Chia oil constants, 219 Channel catfish oil constants, 219 China clay analysis, 327 Chinese blue, 362 Chinese wood oil analysis, 239 in paints, 217 specifications, 239 constants, 219 Chrome green, 368 yellows, 358 Coal tar pitch, 302 Coating apparatus, Experimental, 13 Cobalt blue, 365 drier, 255 Coefficient of diffuse reflection of pigments, 80 Color analyzer, Keuffel & Esser, 42 change cabinet, 61 chip maintenance, 45 of varnishes, 167 white pigments, 210 standards for varnishes, 165 strength of caramel solutions, 166 systems, 34, 35 Colorgraphing color, 43 Colorimeter for white Pfund, 21, 22 Colorimeters, 34, 36, 38 Colorimetric determination of cop- per, 336 Colors, Method for testing, 206 Colors, Wave length of, 46, 47 Condition of pigments on absorbing oil, 117 Consistency of stearate 184 Constants of oils, 219, 220 Cooper-Hewitt ultraviolet light, 125 Copper oxide in paint, 354 paint, 354 Corroded white lead, 304 Corn oil constants, 219 Cottonseed oil constants, 219 Cumaron resin, 266 Cryptometer, Pfund, 19, 20 Cyanide blue, 362 D Detection of special oils in paints, 216 spirit varnish components, 252 surfaces, solutions, Diazo reaction, 303 Dielectric strength tests, 277 Diffuse reflection of pigments, Co- efficient of, 80 Discoloration of interior whites, 61 Distillation range of mineral spirits, 179 Distillation range of thinners, 171 Draft test apparatus, 247 Draft test on varnish, 247 Drier analysis, 255 Driers in paints, 216 varnishes and pigmented enamels, 256 Drying time meter, 56 Du Nouy surface tension apparatus, 156 E Eastlack-Booge test for lithopone, 134 Eastman Universal Colorimeter, 38 Effect of acidity on light resistance, — 123 Effect of colors on hiding power, 26 Effect of lacquer upon metal, 285 solvents upon resins, 259, 260 ultraviolet light on pigments, 146 Elasticity of paint films, 17 Ester gum, 265 Evaporation effects, 169 Evaporation speed of lacquer sol- vents, 291 Experimental coating apparatus, 138 Exposure tests on antifouling paints, 203, 204 metal paints, 195 paints and varnishes, 193, 199 paper, 12 Exterior exposure vs. accelerated testing, 76 F Figuring bulking values of paint, 90 Film gauge, Pfund, 27 Films, Elasticity of, 17 Hardness of, 68 Hiding power of, 17 Nelson tests on, 17 paint, Testing of, 11 ; s E Pet OR Se ee ga ee eee ee ee Yee INDEX 373 Films, strength of, 14-16 tested for hardness, Photomicro- graphs of, 69 thickness of, 14-16 Use of microscope for examining, 64 Fineness, Greene method for determ- ining, 101 of paint pigments,. 91 testing apparatus, 95, 96 Fish oil constants, 220 in paints, 217 Fixed oils and resins in varnish, 248 Flake red lead analysis, 343 Flash point of varnishes, 246 Flaxseed analysis, 237 examination, 237 Flow curves of paints and varnishes, 51 Flowing values of paints and var- nishes, 54, 55 Flowmeter, 48 Fossil resin analysis, 258 Fur seal oil constants, 220 Fusibility of resins, 261 G Gardner photomicrographic camera for exterior tests, 106 Gardner-Holdt colorimeter, 165 viscometer, 150 Gas resistance of varnishes, 247 test apparatus, 247 Gel test apparatus for stearate, 185 Gels of aluminum stearate, 189 Grapeseed oil constants, 219 Graphic analysis of sublimed white lead, 315 Grayfish oil constants, 220 Green pigments, 368 Greene method for determining fine- ness, 101 Gypsum, 304 aluminum H Hardness of films, 68 Heat test, 279 Heat test for tung oil, 240 Heating test on tung oil, 244 Heavy bodied linseed oil, Constants of, 219 Hempseed oil constants, 219 Hexabromide numbers on oils, 234- 236 Hexabromide test on oils, 224 Hiding power, Effect of colors on, 26 of films, 17, 21 of pigment-oil mixtures, 27 of pigments, 28, 25 tests, Shaded paper for, 18 Humidity cabinet for testing films, 59 Indian red, 351 Insulating varnishes, 276 Interfacial tension, 154 apparatus, 158 Iron arc equipment design, 135 test on lithopone, 134, 138-142 Iron cyanide blues, 362 J Japanese wood oil constants, 219 K Kapok seed oil constants, 219 Kauri gum reduction tests on min- eral spirits, 177 Keuffel & Esser color analyzer, 42 L Lacquer analysis, 293 Lacquer components, 292 Lake colors, Qualitative tests for, 347 Lead chromate, 358 drier, 255 oxide analysis, 333 Leaded zinc, 304, 316 Light resistance of lithopone, 128 Linseed oil analysis, 218 constants, 219 Litharge analysis, 336 Lithographic linseed oil, Constants OFA219 at4 INDEX Litho] red, Analysis of, 348 Lithopone, 304 analysis, 321, 360 Light resistance of, 123 tests for darkening, 142 Lumbang oil constants, 219 M Manganese drier, 255 Marine exposure tests, 204 Mcllhenny-Steele method on shellac, 273 Melting point of resins, 261 Menhaden oil constants, 220 Mercury arc tests on pigments, 80 Method of determining texture of pigments, 119 Microscope, Use of, for examining films, 64 Mineral spirits, Distillation range of, 179 Sulphur test on, 179 Testing, 175 Moist cabinet for testing paints, 58 Moisture in shellac, 271 Mullen’s tester, 10 N Nelson cabinet, 71 test on paint films, 17 New Jersey Zinc Company’s accele- rated testing cabinet, 72 Non-volatile matter, 281 O Ochre analysis, 355 Oil absorption of colors, 207, 208 factors on pigments, 110 of pigments, 107, 111 Oil analysis, 218 et seq. constants, 219, 220 in flaxseed cake, 237 test, 280 Opacity of pigments to ultraviolet light, 147 Optical dispersion of tung oil, 245 Orange mineral analysis, 339 pigments, 358 Organic color in red lead, 344 lakes, 847 red pigments, 347 Oticia oil constants, 219 iM Palo Maria oil constants, 219 Panels for exposure tests, 194 Paper, Tests on, 12 Para red, 347 Peanut oil constants, 219 Perilla oil constants, 219 Permeability of films, 10 Pfund paint testing instruments, 19- 22,21, 29, 308 Photographing pigments, 102 Photographs of exposed lacquers, varnishes and paints, 202 Photomicrographic camera for ex- terior tests, Gardner, 106 Photomicrographs of films tested for hardness, 69 of paint texture, 121 of paint and varnish films, 65-67 of pigments, 98-100, 102, 104, 105 of pigment screens, 92 of pigment texture, 121 Physical character of films, 9 Examination of paint materials, 9 properties of white pigments, 210 Pig lead analysis, 336 Pigment in lacquer, 285 Plasticity of paints and varnishes, 51, 55 Plasticity and yield value, 48 Polymerized oils and resins, 249 Poppyseed oil constants, 219 Prince’s metallic red analysis, 351 Protein in oil cake, 288 Prussian blue, 362 Pycnometer for specific gravity, 86 Pyroxylin lacquer coatings, 283 Q Quality test on tung oil, 244 Quartz tube mercury lamp, 73 R Raisinseed oil constants, 219 Raw Linseed oil, Constants of, 219 ee ee ee ee ae ee ee ee _—— P , ‘ ill ee tet a ee ee ee oe INDEX Red lead analysis, 333, 339 oxide of iron analysis, 351 Reporting conditions on exposure tests, 196 Resinates in paints, 216 Resin acids, 262 Resin analysis, 258, 266 Solubility of, 259, 260 in varnish, 248 Rosin, 265 in shellac, 269, 273 oil constants, 219 Routine testing methods for white pigments, 210 Rubberseed oil constants, 219 S Salmon oil constants, 220 Saponification value of lacquers, 288 Sardine oil constants, 220 Schaeffer analytical methods, 348 Seal oil constants, 220 Sesame oil constants, 219 Settling test for pigments, 211 Shaded paper for hiding power tests, 18 Shark oil constants, 220 liver oil constants, 220 Shellac purity by Steele-McIlhenny method, 273 Shellac testing, 267 weighing, 275 Ship paints, 204 Sienna analysis, 355 Silica analysis, 327 Skate liver oil constants, 220 Soft lumbang oil constants, 219 Softening point of resins, 261 Solids in lacquer, 286 Solubility of resins, 261 Solutions for shellac testing, 268 Solutions for testing oils, 218 Solvent in varnishes, 246 Source of ultraviolet energy, 78 Soya bean constants, 219 Special oils in paints, Detection of, 216 Specific gravity apparatus, 82, 84 of colors, 89 of paint liquids, 85, 88 of pigments, 81, 89 Speed of evaporation of thinners, 169 375 Spectrophotometers, 34, 40 Spirit varnishes, 352 Spreading rate of paints, 32, 33 Standard solutions for testing oils, 218 Stearate solutions, 183 Steel panel exposure tests, 195 Steele-McIlhenny method on shellac, 273 Steele & Washburn test, 225 Strength of films, 14-16 Sublimed blue lead analysis, 366 Sublimed white lead, 304, 310 Sulphur test on mineral spirits, 179 Sunflower oil constants, 219 Surface tension, 154 of paint oils and liquids, 157 Synthetic resin, 265, 266 Ak Talking machine record tests on pig- ments, 98-100 Tar pitch, Coal, 301 water gas, 302 wood, 302 Tension of paint liquids, 160 Testing cabinets, 71 et seq. Testing colors for tone and strength, 206 Testing paint films, 11 Testing the light resistance of litho- pone, 124 Texture of pigments, 118 Thickness of films, 14-16, 30, 31, 33 Thinners, Blown oil test on, 178 Distillation range of, 171 Effect of upon viscosity, 174 Evaporative rate of, 173 Viscosity effects induced by, 169 Tinting strength of white pigments, ra Titanium oxide, 304 Titanox analysis, 324 paint analysis, 326 Toluidine red, 348 Total solids in lacquer, 286 Tricresyl phosphate, 289 Tuna fish oil constants, 220 Tung oil constants, 219 test apparatus, 240 testing, 239 Turpentine, 175 Tuscan red analysis, 351 376 U Ultramarine blue, 364 Ultraviolet energy, Source of, 78 light for testing cabinet, 73 opacity tests, 147, 148 tests on pigments, 146 Umber analysis, 355 Use of microscope for examining films, 64 Uviare lamp, 125 test on lithophone, 126-134 V Varnish analysis, 246 Varnishes, Color of, 167 Viscosity of, 174 Vehicles, Analysis of, 213 Venetian red analysis, 355 Vermilion analysis, 347, 358 Viscosity, Effect of different thin- ners on, 174 effects induced by thinners, 169 of stearates, 184 varnishes, 149, 174, 284 in poises, 151 Volatile constituents in lacquer, 287 Volatiles in paints and varnishes, 216, 248 INDEX W Washburn and Steele test, 225 Water absorption tests, 279 gas tar, 302 in oil cake, 237 Wave length measurements on pig- ments, 80 of colors, 46, 47 pigments, 41 Whale oil constants, 220 White lead, 304 White paint analysis, 304 et seq. White pigments, Brightness of, 210 Color of, 210 Physical properties of, 210 Routine testing methods for, 210 Tinting strength of, 211 Whiting analysis, 328 Wood oil constasts, 219 Wood tar, 302 Y Yellow lithopone, 360 pigments, 358 Yellowing of whites, 61 Yellow tailfish oil constants, 220 Yield of paint, 90 Yield values, 48 Z Zine lead, 304 oxide, 304 analysis, 317 STANDARD SPECIFICATIONS For USE OF DEPARTMENTS AND INDEPENDENT ESTABLISHMENTS OF THE U. S. GOVERNMENT OFFICIALLY ADOPTED BY THE FEDERAL SPECIFICATIONS BOARD The specifications issued to date, in so far as they are available at the Government Printing Office, have been bound in this volume. The list is given below: Bureau ards ___ fications er Board Edition Title ° 0) 82 4 2nd Edition—Linseed Oil. 84 5 29nd Edition—Basic Carbonate White Lead. 85 6 2nd Edition—Basic Sulphate White Lead. 86 c 2nd Edition—Turpentine. 87 8 2nd Edition—Zine Oxide. ] 2nd Edition—Leaded Zine Oxide. 89 10 2nd Edition—White and Tinted Paints (Exterior). 90 11 2nd Edition—Red Lead. 91 12 2nd Ediiton—Ocher. 93 13 2nd Edition—Iron Oxide Paints. 94 14 2nd Edition—Black Paint. 97 15 3rd Edition—Green Paint. 98 16 2nd Edition—Mineral Spirits. 102 17 Ist Edition, corrected—Composite Thinner. 103 18 3rd Edition—Spar Varnish 104 19 9nd Edition—Asphalt Varnish. 105 20 29nd EKdition—Liquid Paint Drier. 111 21 2nd Edition—Flat Interior Lithopone Paint. 117 22 2nd Edition—Interior Varnish. 146 66 Sept., 1923—Water-Resisting Red Enamel. 147 67 Sept., 1923—Gloss Interior Lithopone Paint. 163 115 Feb., 1924—Titanium Pigment, Dry and Paste. At a recent meeting of the Federal Specifications Board, two new specifications were adopted and will be printed in the very near fu- ture. Copies may possibly be obtained about the first of April, 1925, from the Government Printing Office, Washington, D. C., at five cents each. These specifications will be designated as follows: “Federal Bureau Specifi- of cations Stand- Board ards Spectfica- Circular cation Title No. 0. k : DOO re a Specification for Heavy Rust Preventive Com- pound. Rr eae Nitanox-Zine Exterior Paint. February 1, 1925. RY OTS As Te ial Gs ae at (HiT ae NG eee 5 oe ae mc | we t yg cet cee ' ; Fie rttov. att a nse a ee, vad: a f 4 rs | ee me a rt ASE TRA ete EOE helene ie fF a get > SO se PO ror ernest ter ah £ 2. ! rade ei coma FPR Ru aa er e dees f teen off! Fae Kea se dey any ™ ‘e Mioh ae b merge bie OU Thi ei Sta “M00. FL vod s fey Sa Gaa DEPARTMENT OF COMMERCE BUREAU OF STANDARDS S. W. STRATTON, Direcior CIRCULAR OF THE BUREAU OF STANDARDS No. 82 [2d edition. Issued June 8, 1922] UNITED STATES GOVERNMENT SPECIFICATION FOR LINSEED OIL, RAW, REFINED, AND BOILED ee ee FEDERAL SPECIFICATIONS BOARD STANDARD SPECIFICATION No. 4 This Specification was officially adopted by the Federal Specifications Board, on February 3, 1922, for the use of the Departments and Independent Establish- ments of the Government in the purchase of materials covered by it. CONTENTS rg » 09 o (TS oe ee a irre ene ee Oa PEE ER ITIOAIOD oe. preeeiee y

‘ t { H iJ , t , : . yin } Ge ec + : 7 2 : ? * ‘ ‘ ”-F a 4 , - pie ‘ hae ae i t+ ! i rece , Ce ae A as ' - + -f- 7 Fs z je A PRCT Le Eee . A “PETAR ae YA LOU AT Sein 4 x Asity Pate Oh. Ld ea sae VSM Sip 2 OTR S see Lit Oey Pee ery + bal 4 DEPARTMENT OF COMMERCE. BUREAU OF STANDARDS. S. W. STRATTON, Director. CIRCULAR OF THE BUREAU OF STANDARDS. No. 84. [2d edition. Issued July 3, 1922.] UNITED STATES GOVERNMENT SPECIFICATION FOR BASIC CARBONATE WHITE LEAD, DRY AND PASTE, FEDERAL SPE@JFICATIONS BOARD. STANDARD SPECIFICATION NO. 5. This Specification was officially adopted by the Federal Specifications Board on February 3, 1922, for the use of the Departments and Independent Establish- ments of the Government in the purchase of materials covered by it. CONTENTS. Page Teel IE MS, ei Be LY 2 ep I en, eee ee ee ee, 2 3. Laboratory examination of dry pigment.........................-.-... 2. 3 4. Laboratory examination of paste...........:...... Bis OS Rae dds TREE 4 eS Oa re es a OG an Rae a Ok 7 1. GENERAL. Basic carbonate white lead may be ordered in the form of dry pigment or paste ground in linseed oil. Material shall be pur- chased by net weight. (2) Dry PicmMeNnt.—The pigment shall be the product made from metallic lead and shall have a composition corresponding approximately to the formula 2PbCO,.Pb(OH),. It shall be thoroughly washed after corroding, shall be free from impurities and adulterants, and shall meet the following requirements: 106568 °—24 2 Circular of the Bureau of Standards Color—Color strength.—When specified, shall be equal to that of a sample mutually agreed upon by buyer and seller. I pa sn omer Minimum, | Maximum. a Per cent. | Per cent. Coarse particles retained on Standard No. 325 SCFeeN............ 2 cee ndt een eee efasar ere canes 1.0 Fead carbomate,.. cc. veg. occs cyece epee ls home esinee nine shove’ al 1008s s Gees 65. 0 75.0 Total impurities, including moisture..........-..+++++rerreeesstrrertseetetetetstestsssses ees 2.0 (b) Paste.—The paste shall be made by thoroughly grinding the above-described pigment with pure raw or refined linseed oil. The paste as received shall not be caked in the container and shall break up readily in oil to form a smooth paint of brushing consistency. ‘The paste shall consist of: ee Minimum. | Maximum. a Pigment) 2002 dic tels ones coco tensed seus tenann na ea» Vester a ata hi Linseed Of)... oc ss cede ecu se cacweessae ema aes Ap at ho «bin sivs sy fee rs 8 10 Moisture and other volatile matter............. 0.0. .e ee ece terete ete nee eee elec eee ee eeees 0.7 Coarse particles and ‘‘skins’’ (total residue retained on No. 325 screen based on pigment)... ...ce.ciseeceenecenseecuneeeaueee cee snl ens tanianhi)s at AN ois se 1.5 a Nore.—Deliveries will, in general, be sampled and tested by the following methods, but the purchaser reserves the right to use any additional available information to ascertain whether the material meets the specification. 2. SAMPLING. It is mutually agreed by buyer and seller that a single package out of each lot of not more than 1,000 packages shall be taken as representative of the whole. With the dry pigment, this package shall be opened by the inspector and a sample of not less than 5 pounds taken at random from the contents and sent to the laboratory for test. When requested, a duplicate sample may be taken from the same pack- age and delivered to the seller, and the inspector may take a third sample to hold for test in case of dispute. Whenever possible, an original unopened container shall be sent to the laboratory with the paste; and when this is for any reason not done, the inspector shall determine by testing thor- oughly with a paddle or spatula whether the material meets the requirement regarding not caking in the container. (See 4 (a).) After assuring himself that the paste is not caked, the inspector shall draw a sample of not less than 5 pounds of the thoroughly mixed paste, place it in a clean dry metal or glass container, which must be filled with the sample, closed with a tight cover, sealed, marked, and sent to the laboratory for test with the inspector’s report on caking in container. . Specification jor Basic Carbonate White Lead, Dry and Paste 3 3. LABORATORY EXAMINATION OF DRY PIGMENT. (a) CoLlor.—Take 1 g of the sample, add 10 to 12 drops linseed oil, rub up on a stone slab or glass plate with a flat-bottomed glass or stone pestle or muller to a uniform smooth paste. Treat in a similar manner 1 g of the standard basic carbonate white lead. Spread the two pastes side by side on a glass microscope ) slide and compare the colors. If the sample is as white or whiter than the ‘‘standard,”’ it passes this test. If the standard is whiter than the sample, the material does not meet the specification. (b) CoLoR STRENGTH.—Weigh accurately 0.01 g of lampblack, place on a large glass plate or stone slab, add 5 drops of linseed oil, and rub up with a flat-bottomed glass pestle, or muller, then add exactly 10 g of the sample and 45 drops of linseed oil, and grind with a circular motion of the muller 50 times; gather up with a sharp-edge spatula and grind out two more times in a like manner, giving the pestle a uniform pressure. Treat another 0.01 g of the same lampblack in the same manner, except that 1o g of standard basic carbonate white lead is used instead of the 10 g of the sample. Spread the two pastes side by side on a glass microscope slide and compare the colors. If the sample is as light or lighter in color than the standard, it passes this test. If the standard is lighter in color than the sample, the material does not meet the specification. (c) Coarse ParTICLES.'—Dry in an oven at 105° to 110° C. a No. 325 screen, cool and weigh accurately. Weight 25 g of the sample; dry at 100° C.; transfer to a mortar, add 100 cc kero- sene, thoroughly mix by gentle pressure with a pestle to break up all lumps, wash with kerosene through the screen, breaking up all lumps, but not grinding. After washing with kerosene until all but the particles which are too coarse to pass the screen have been washed through, wash all kerosene from the screen with ether or petroleum ether, heat the screen for one hour at 105 to 110° C., cool and weigh. (d) QUALITATIVE ANALYSIS.—Test for matter insoluble in acetic acid, zinc, calcium, etc., by the regular methods of qualitative analysis. (ec) MorsruRE.—Place 1 g of the sample in a tared wide-mouth short weighing tube provided with a glass stopper. Heat with tie fey en 1 For a general discussion of screen tests of pigments and data regarding many pigments on the market, see Circular No. 148 of the Educational Bureau, Scientific Section, Paint Manufacturers’ Association of the United States. 4 Circular of the Bureau of Standards stopper removed for two hours at a temperature between 105 and 110°C. Insert stopper, cool and weigh. Calculate loss in weight as moisture. (f) Tota, LEAD AND INSOLUBLE ImpuRITY.—Weigh 1 g of the sample, moisten with water, dissolve in acetic acid. If any insol- uble residue remains, filter, dry at 105 to 110° C. and weigh as insoluble impurity. Dilute the solution to about 200 ec, make alkaline with NH,OH, then acid with acetic acid, heat to boiling and add ro to 15 cc of a 10 per cent solution of sodium bichromate or potassium bichromate, and heat until the yellow precipitate assumes an orange color. Let it settle and filter on a Gooch crucible, washing by decantation with hot water until the wash- ings are colorless, and finally transferring all the precipitate. Then wash with 95 per cent ethyl alcohol and then with ethyl ether; dry at 100° C. and weigh PbCrO,. Calculate to lead oxide (PbCrO, x0.69=PbO). Total lead may be determined by the sulphate method if preferred. (g) CARBON Diox1DE.—Determine by evolution with dilute acid and absorption in soda-lime or KOH solution, calculate CO, to PbCO,, subtract PbO equivalent from total PbO and calculate residual PbO to Pb(OH),. CO; x6.072 = PbCO, CO, X 5.072 =Fpw PbO X 1.197 = PbCOz PbO X 1.08 =Pb(OH), 4. LABORATORY EXAMINATION OF PASTE. (a2) CAKING IN CONTAINER.—When an original package is received in the laboratory, it shall be weighed, opened, and stirred with a stiff spatula or paddle. The paste must be no more difficult to break up and show no more caking than a normal good grade of white-lead paste. The paste shall finally be thor- oughly mixed, removed from the container, and the container wiped clean and weighed. This weight subtracted from the weight of the original package gives the net weight of the contents. A portion of thoroughly mixed paste shall be placed in a clean container and the portions for the remaining tests promptly weighed out. (6) MixiInc witH LINSEED O1,.—One hundred grams of the paste shall be placed in a cup, 30 cc linseed oil added slowly with a Specification for Basic Carbonate White Lead, Dry and Paste 5 careful stirring and mixing with a spatula or paddle. ‘The result- ing mixture must be smooth and of good brushing consistency. (c) MOISTURE AND OTHER VOLATILE MATTER.—Weigh accu- rately from 3 to 5 g of the paste into a tared flat-bottomed dish, about 5 cm in diameter, spreading the paste over the bottom. Heat at 105 to 110° C. for one hour, cool and weigh. Calculate loss in weight as percentage of moisture and other volatile matter. _ (d) PERCENTAGE oF PIGMENT.—Weigh accurately about 15 g of the paste into a weighed centrifuge tube. Add 20 to 30 cc “extraction mixture”’ (see Reagents), mix thoroughly with a glass rod, wash the rod with more of the extraction mixture, add enough of the reagent to make a total of 60 cc in the tube. Place the tube in the, container of a centrifuge, surround with water and counterbalance the container of the opposite arm with a similar tube or a tube with water. Whirl at a moderate speed until well settled. Decant the clear supernatant liquid. Repeat the extraction twice with 4o cc of the extraction mixture, and once with 40 cc of ether. After drawing off the ether, set the tube in a beaker of water at about 80° C., or on top of a warm oven for 10 minutes, then in an oven at 110 to 11 5° C. for two hours. Cool, weigh, and calculate the percentage of pigment. (e) EXAMINATION OF PIGMENT.—Grind the pigment from (d) to a fine powder, pass through a No. 80 screen to remove any “skins,” preserve in a stoppered tube and apply tests 3(a), 3(b), 3(d), 3(7), and 3(g). (7) PREPARATION oF Fatty Actps.—To about 25 g of the paste in a porcelain casserole add 15 cc of aqueous sodium hydroxide (see reagents) and 75 cc of ethyl alcohol, mix and heat uncovered on a steam bath until saponification is complete (about one hour). Add 100 cc of water, boil, add sulphuric acid of specific gravity 1.2 (8 to 10 cc in excess), boil, stir, and transfer to a separatory funnel to which some water has been previously added. Draw off as much as possible of the acid aqueous layer and lead sulphate precipitate, wash once with water: then add 50 cc of water and 50 cc of ether. Shake very gently with a whirl- ing motion to dissolve the fatty acids in the ether, but not so violently as to form an emulsion. Draw off the aqueous layer and wash the ether layer with one 15 cc portion of water and then with 5 cc portions of water until free from sulphuric acid. Then draw off the water layer completely. Transfer the ether solution to a dry flask, add 25 to 50 g of anhydrous sodium sulphate. 6 Circular of the Bureau of Standards Stopper the flask and let stand with occasional shaking at a tem- perature below 25° C. until the water is completely removed from the ether solution, which will be shown by the solution becoming perfectly clear above the solid sodium sulphate. Decant this clear solution (if necessary through a dry filter paper) into a dry 100 cc Erlenmeyer flask. Pass a rapid current of dry air (pass through a CaCl, tower) into the mouth of the Erlenmeyer flask and heat ata temperature below 75° C. on a dry hot plate until the ether is entirely driven off. . Norx.—It is important to follow all of the details, since ether generally contains alcohol and after washing with water always contains water. It is very difficult to remove water and alcohol by evaporation from fatty acids, but the washing of the ether solution and subsequent drying with anhydrous sodium sulphate removes both water and alcohol. Ether, in the absence of water and alcoliol, is easily removed from fatty acids by gentle heat. The fatty acids prepared as above should be kept in a stoppered © flask and examined at once. (g) TEST FOR MINERAL O1.—Place 10 drops of the fatty acid (f) in a 50 cc test tube, add 5 cc of alcoholic soda (see reagents), boil vigorously for five minutes, add 40 cc of water and mix. A clear solution indicates absence of more than a trace of unsaponi- fiable matter. If the solution is not clear, the oil is not pure linseed oil. (hk) lopINE NUMBER OF Farry Acips.—Place a small quantity of the fatty acids (f) in a small weighing burette or beaker. Weigh accurately. Transfer by dropping about 0.15 g (0.10 to 0.20 g) to a 500 cc bottle having a well-ground glass stopper, or an Erlenmeyer flask having a specially flanged neck for the iodine test. Reweigh the burette or beaker and determine the amount of sample used. Add ro cc of chloroform. Whirl the bottle to dissolve the sample. Add 10 cc of chloroform to two empty bottles like that used for the sample. Add to each bottle 25 cc of the Hanus solution (see reagents) and let it stand with occa- sional shakings for one-half hour. Add 10 ce of the 15 per cent potassium-iodide solution and 100 cc of water, and titrate with standard sodium thiosulphate, using starch as indicator. The ti- tration on the two blank tests should agree within 0.1 cc, From the difference between the average of the blank titrations and the titration on the sample, and the iodine value of the thiosul- phate solution, calculate the iodine number of the sample tested. (Iodine number is centigrams of iodine to 1 g of sample.) If ee ee ae ee Se Specification for Basic Carbonate White Lead, Dry and Paste 7 the iodine number is less than 170, the oil does not meet the specification. (i) COARSE PARTICLES AND ‘“‘SKINS.”—Weigh an amount of paste containing 25 g of pigment (see 4 (d)), add roo cc kero- sene, wash through a No. 325 screen and weigh the residue as in arte): 5. REAGENTS. (a) ExTRACTION MIxTURE— 10 volumes ether (ethyl ether). 6 volumes benzol. 4 volumes methyl alcohol. 1 volume acetone. (6) AQguEOuS Soprum HyproxIpE.—Dissolve 100 g sodium hydroxide in distilled water and dilute to 300 cc. (c) STANDARD SODIUM ‘THIOSULPHATE SOLUTION.—Dissolve pure sodium thiosulphate in distilled water that has been well boiled to free it from carbon dioxide, in the proportion of 24.83 g crystallized sodium thiosulphate to 1,000 cc of the solution. It is best to let this solution stand for about two weeks before standardizing. Standardize with pure resublimed iodine.” This solution will be approximately decinormal, and it is best to leave it as it is after determining its exact iodine value, rather than to attempt to adjust it to exactly decinormal. Preserve in a stock bottle provided with a guard tube filled with soda lime. (d) STARCH SOLUTION.—Stir up 2 to 3 g of potato starch or 5 g of soluble starch with too ce of 1 per cent salicylic acid solution, add 300 to aoo cc of boiling water, boil the mixture until the starch is practically dissolved, and then dilute to one liter. (e) Porasstum IopIDE SOLUTION. —Dissolve 150 g potassium iodide free from iodate in distilled water and dilute to 1,000 cc. (7) Hanus So_utron.—Dissolve 13.2 g iodine in 1,000 cc of glacial acetic acid, 99.5 per cent, which will not reduce chromic acid. Add enough bromine, about 3 cc to double the halogen content, which is determined by titration. The iodine may be dissolved by applying heat, but the solution should be cold when the bromine is added. | . (g) ALCOHOLIC SopIUM-HYDROXIDE SOLUTION.—Dissolve pure sodium hydroxide in 95 per cent ethyl alcohol in the proportion of 2 See Treadwell-Hall Analytical Chemistry, I], 3d ed., p. 646. 8 Circular of the Bureau of Standards about 22 g per 1,000 cc. Let the solution stand in a stoppered bottle. Decant the clear liquid into another bottle, and keep well stoppered. This solution should be colorless or only slightly yellow when used, and it will keep colorless longer if the alcohol is previously treated with NaOH (about 80 g to 1,000 cc), kept at about 50° C. for 15 days, and then distilled. ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. AT 5 CENTS PER COPY V WASHINGTON : GOVERNMENT PRINTING OFFICE : 1924 DEPARTMENT OF COMMERCE. BUREAU OF STANDARDS. S. W. STRATTON, Director. CIRCULAR OF THE BUREAU OF STANDARDS. No. 85. [2d edition. Issued July 3, 1922.] UNITED STATES GOVERNMENT SPECIFICATION FOR BASIC SULPHATE WHITE LEAD, DRY AND PASTE. es FEDERAL SPECIFICATIONS BOARD. STANDARD SPECIFICATION NO. 6. This Specification was officially adopted by the Federal Specifications Board on February 3, 1922, for the use of the Departments and Independent Estab- lishments of the Government in the purchase of materials covered by it. CONTENTS. Page AT RM Tos. PRS oon eke St EP Eee bis fe Phare ee I Merete me renee CPOE Ge BE, tteis al a he ae oF Sd Be 2 S.:Laborsary examination of dry pigment): !) i). ui du. biiee an A 2 eet el Oe TIENT OL DASte Fs. ow sce sien, posh mlenyn'e anita w Aa seb vok ‘ SnaNMNE Teme re sesh, Sh Pa at OEE RA OE ARE, | ee Res 7 1. GENERAL. Basic sulphate white lead may be ordered in the form of dry pigment or paste ground in linseed oil. Material shall be pur- chased by net weight. (2) Dry Picment.—The pigment shall be the sublimed product prepared from lead sulphide ores, free from impurities and adul- terants, and shall meet the following requirements: Color—Color Strength.—When specified shall be equal to that of a sample mutually agreed upon by buyer and seller. Minimum. | Maximum. Coarse particles: ~ Per cent. | Per cent. etabied. on Mandard Nov425.acreen=: . sor vty oo. 4. 08.8 BSD ee ek ewe 1.0 Composition: RC ERE rece te ty eae hag eee ine ce chase Cost ae ieee 11.0 18.0 CAT GEO C ihe aole cts oy 6 te Eg Te Oe eA Pi ee TIS AO RBG a oR 9.0 20al impudties, including moisture ooo es us Has sob en ddd wes wivewsetuasacdpeuwOsaiaves 1.0 The remainder shall be lead sulphate. a 104952°—24——-1 2 Circular of the Bureau of Standards (b) PasteEs.—The paste shall be made by thoroughly grinding the dry pigment with pure raw or refined linseed oil. The paste as received shall not be caked in the container and shall break up readily in oil to form a smooth paint of brushing consistency. It shall mix readily in all proportions without curdling with linseed oil, turpentine, or volatile mineral ie or any combination of these substances. The paste shall consist of: ees Per Sori [ko (991) 1) eg erry aed CON EDR EO LRM MGR OMANI EM am 1.0 Pinseed Oil... Bak sh ioe oe a ks Me a BOY ee eee rN 0 Moisture and other volatile: matter...) occ. css cies wse.pesiecls selssens « ve ee ee 0.7 Coarse particles and ‘‘skins”’ ( totai residue retained on No. 325 screen, based on PUTMNCTL) ee eed aa ce ba banaue baccevs sce un/be wb oals meu o/h-cln a alkene an 1.5 Note.—Deliveries will, in general, be sampled and tested by the following methods, but the purchaser reserves the right to use any additional available information to ascertain whether the © matety meets the specification. 2. SAMPLING. It is mutually agreed by buyer and seller that a single package out of each lot of not more than 1,000 packages shall be taken as representative of the whole. With the dry pigment, this package shall be opened by the inspector and a sample of not less than 5 pounds taken at random from the contents and sent to the laboratory for test. With the paste, whenever possible, an original unopened con- tainer shall be sent to the laboratory; and when this is for any reason not done, the inspector shall determine, by thorough test- ing with a paddle or spatula, whether the material meets the requirement regarding not caking in the container. (See 4a.) After assuring himself that the paste is not caked in the container the inspector shall draw a sample of not less than 5 pounds of the thoroughly mixed paste, place it in a clean dry metal or glass con- tainer, which must be filled with the sample, closed with a tight cover, sealed, marked, and sent to the laboratory for test with the inspector’s report on caking in container. When requested, a duplicate sample may be taken from the same package and delivered to the seller, and the inspector may take a third sample to hold for test in case of dispute. 3. LABORATORY EXAMINATION OF DRY PIGMENT. (a) CoLor.—Take 1 g of the sample, add ro to 12 drops linseed oil, rub up on a stone slab or glass plate with a flat-bottomed glass or stone pestle or muller to a uniform smooth paste. Treat in Specification for Basic Sulphate White Lead, Dry and Paste 3 a similar manner, 1 g of the standard basic sulphate white lead. Spread the two pastes side by side on a glass microscope slide and compare the colors. If the sample is as white as or whiter than the “standard,” it passes this test. If the ‘‘standard’’ is whiter than the sample, the material does not meet the specification. (6) CoLor StRENGTH.— Weigh accurately o.o1 g of lampblack, place on a large glass plate or stone slab, add 5 drops of linseed oil and rub up with a flat-bottomed glass pestle or muller, then add exactly 10 g of the sample and 45 drops of linseed oil and grind with a circular motion of the muller 50 times; gather up with a sharp-edge spatula and grind out twice more in a like manner, giving the pestle a uniform pressure. ‘Treat another 0.01 g of the satne lampblack in the same manner except that 10 g of standard basic sulphate white lead is used instead of the 10 g of the sample. Spread the two pastes side by side on a glass microscope slide and compare the colors. If the sample is as light as or lighter in color than the ‘‘standard,”’ it passes this test. If the ‘‘standard’’ is lighter in color than the sample, the material does not meet the specification. (c) COARSE PaRTICLES.'—Dry in an oven at 105 to 110° C. a No. 325 screen, cool, and weigh accurately. Weigh 25 g of the ~ sample, dry at 10o0°C.; transfer to a mortar, add 100 cc kerosene, thoroughly mix by gentle pressure with a pestle to break up all Jumps, wash with kerosene through the screen, breaking up all lumps but not grinding. After washing with kerosene until all but the particles too coarse to pass the screen have been washed through, wash all kerosene from the screen with ether or petroleum ether, heat the screen for one hour at 105 to 110° C., cool, and weigh. (d) QUALITATIVE ANALYSIS. —Test for matter insoluble in acid ammonium acetate solution, for calcium, for carbonates, and for any other impurities suspected by the regular methods of qualitative analysis. (e) MorsturE.—Place 1 g of the sample in a tared, wide mouth, short weighing tube provided with a glass stopper. Heat with Aig removed for two hours'at a temperature between 105 and 110°C. Insert stopper, cool, and weigh. Calculate loss in weight as moisture. 1 For a general discussion of screen tests of pigments and data regarding many pigments on the market, see Circular No. 148 of the educational bureau, scientific section, Paint Manufacturers’ Association of the United States. 4 Circular of the Bureau of Standards (f) INSOLUBLE ImpuRITY AND ToTaL LeEapD.—In a 250 cc beaker, moisten 1 g of the pigment with a few drops of alcohol; add 50 cc of acid ammonium acetate solution. (See Reagents 5a.) Heat to boiling and boil for 2 minutes. Decant through a filter paper, leaving any undecomposed matter in the beaker. To the residue in the beaker, add 50 ce of the acid ammonium acetate solution, heat to boiling, and boil for 2 minutes. Filter through - the same paper and wash with hot water. If an appreciable residue remains, ignite and weigh as insoluble impurity. Unite the acid ammonium acetate solutions, heat to boiling, and add dropwise, with stirring, a slight excess (in total about 10 to 15 cc) of dichromate solution. (See Reagents 55.) Heat until the precipitate assumes an orange color, let settle, filter on a weighed Gooch crucible, wash by decantation with hot water until the washings are colorless, and finally transfer all of the precipitate to the crucible. Then wash with 10 cc of 95 per cent ethyl alcohol and finally with rocc of ethyl ether. Dry at 110 to 120° C., cool, and weigh PbCrO,. Calculate to PbO by multiplying by the factor 0.69. (g) Zinc Ox1DE.—Weigh accurately about 1 g of the pigment, transfer to a 400 cc beaker, add 30 ce of HCl (1:2), boil for 2 or 3 minutes, add 200 cc of water and a small piece of litmus paper, add NH,OH until slightly alkaline, render just acid with HCl, then add 3 cc of concentrated HCl, heat nearly to boiling, and titrate with standard potassium ferrocyanide as in standardizing that solution. (See Reagents 5d.) Calculate total zinc as ZnO. (h) LEAD SULPHATE.—Treat 0.5 g of the pigment in a 400 cc beaker with a few drops of alcohol, add 10 ce of bromine water, toccof HCl (1:1), and 3 g of NH,Cl. Cover with a watch glass and heat on a steam bath for 5 minutes, add hot water to give a total volume of about 200 ce, boil for 5 minutes, filter to separate any insoluble matter (a pure pigment should be completely dis- solved), and wash thoroughly with hot water. (The insoluble matter may be ignited, weighed, and examined qualitatively.) Neutralize the clear solution (original solution or filtrate from insoluble matter) in a covered beaker with dry Na,CO,, add 1 g more of dry Na,CO,, and boil 10 to 15 minutes. Wash off cover, let settle, filter, and wash with hot water. Redissolve the precipi- tate in HCl (1:1), reprecipitate with Na,CO, as above, filter, and wash thoroughly with hot water. Acidify the united filtrates with HCl, adding about 1 cc in excess. Boil to expel bromine, Specification for Basic Sulphate White Lead, Dry and Paste 5 and to the clear boiling solution add slowly with stirring 15 cc of barium chloride solution. (See Reagents 5¢.) Let stand on steam bath for about one hour, filter on a weighed Gooch crucible, wash thoroughly with boiling water, dry, ignite, cool, and weigh as BaSO,. Calculate to PbSO,, using the factor 1. Co : (4) CaLCULATIONS.—Calculate the percentage of PbSO, to PbO by multiplying by the factor 0.736 and subtract the result from the percentage of PbO found under (f); report the difference as PbO. Report ZnO found under (g) as percentage of ZnO. Mois- ture and insoluble matter are reported as such.’ 4, LABORATORY EXAMINATION OF PASTE. (aq) CAKING IN CONTAINER.—When an original package is received in the laboratory it shall be weighed, opened, and stirred with a stiff spatula or paddle. The paste must be no more difficult to break up and show no more caking than a normal good grade of white lead paste. The paste shall be finally thoroughly mixed, removed from the container, and the container wiped clean and weighed. ‘This weight subtracted from the weight of the original package gives the net weight of the contents. A portion of the thoroughly mixed paste shall be placed in a clean container and the portions for the remaining tests promptly weighed out from it. (6) Mrxine with LINSEED Om,.—One hundred grams of the paste shall be placed in a cup, and 30 cc of linseed oil added slowly with careful stirring and mixing with a spatula or paddle. The resulting mixture must be smooth and of good brushing con- sistency. (c) MOISTURE AND OTHER VOLATILE MatTTER.—Weigh accu- rately from 3 to 5 g of the paste into a tared flat-bottomed dish, about 5 cm in diameter, spreading the paste over the bottom. Heat at 105 to 110° C. for one hour, cool and weigh. Calculate loss in weight as percentage of moisture and other volatile matter. (d) PERCENTAGE OF PicMENT.—Weigh accurately about 15 g of the paste into a weighed centrifuge tube. Add 20 to 30 ce of “extraction mixture” (see Reagents), mix thoroughly with a glass rod, wash the rod with more of the extraction mixture, and add sufficient of the reagent to make a total of 60 cc in the tube. Place the tube in the container of a centrifuge, surround with water, ? A method given by Schaeffer, J., Ind. and Eng. Chem., 6, p. 200 (1914), based on calculation of compo- sition after determination of moisture, impurities, total lead, and total zinc oxide, is sometimes used. ‘This method requires very accurate determination of Pb and ZnO, since the errors of determination are multi- plied by approximately four in making the calculation to PbO and Pbsoa. 104952°—24 2 6 Circular of the Bureau of Standards and counterbalance the container of the opposite arm with a sim- ilar tube or a tube with water. Whirl at a moderate speed until well settled. Decant the clear supernatant liquid. Repeat the extraction twice with 4o cc of extraction mixture and once with 4o cc of ether. After drawing off the ether set the tube in a beaker of water at about 80° C. or on top of a warm oven for 10 minutes, then in an oven at 110 to II 5° C. for two hours. Cool, weigh, and calculate the percentage of pigment. (e) EXAMINATION OF PicMent.—Grind the pigment from (d) to a fine powder, pass through a No. 80 screen to remove any ‘‘skins,”’ preserve in a stoppered tube, and examine as under 3 (a), 3(0), 3(d), 3 (f), 3(9), 3(2), and 3 (2), Laboratory Examination of Dry Pigment. ({) PREPARATION OF FaTTy Aciws.—To about 25 g of the paste in a porcelain casserole add 15 cc of aqueous sodium hydroxide (see Reagents), and 75 cc of ethyl alcohol, mix, and heat uncovered on a steam bath until saponification is complete (about 1 hour). Add 100 ce of water, boil, add sulphuric acid of specific gravity 1.2 (8 to 10 cc in excess), boil, stir, and transfer to a separatory funnel to which some water has been previously added. Draw off as much as possible of the acid aqueous layer and PbSO, precipitate, wash once with water, then add 50 cc of water and so ce of ether. Shake very gently with a whirling motion to dissolve the fatty acids in the ether, but not violently, so as to avoid forming an emulsion. Draw off the aqueous layer and wash the ether layer with one 15 ce portion of water and then with 5 cc portions of water until free from sulphuric acid. Then draw off completely the water layer. Transfer the ether solution to a dry flask, add 25 to 50 g of anhydrous sodium sulphate. Stopper the flask and let stand with occasional shaking at a temperature below 25° C. until the water is completely removed from the ether solu- tion, which will be shown by the solution becoming perfectly clear above the solid sodium sulphate. Decant this clear solution (if necessary through a dry filter paper) into a dry 100 ce Erlenmeyer flask. Pass a rapid current of dry air (pass through CaCl, tower) into the mouth of the Erlenmeyer flask and heat to a temperature below 75° C. on a dry hot plate until the ether is entirely driven off. The fatty acids prepared as above should be kept in a stop- pered flask and examined at once.* 3Itis important to follow all of the details since ether generally contains alcohol and after washing with water always contains water. It is very difficult to remove water and alcohol by evaporation from fatty acids, but the washing of the ether solution and subsequent drying with anhydrous sodium sulphate removes both water andalcohol. Ether, in the absence of water and alcohol, is easily removed from fatty acids by gentle heat. Specification for Basic Sulphate White Lead, Dry and Paste 7 (g) Test For MINERAL O1L.—Place 10 drops of the fatty acid (7) in a 50 cc test tube, add 5 cc of alcoholic soda (see Reagents), boil vigorously for 5 minutes, add 40 cc of water, and mix; a clear solution indicates that not more than traces of unsaponifiable matter are present. If the solution is not clear the oil is not pure linseed oil. (h) lopine NuMBER oF Farry Acips.—Place a small quantity of the fatty acids (f) in a small weighing burette or beaker and weigh accurately. ‘Transfer by dropping about 0.15 g (0.10 to 0.20 g) to a 50occ bottle having a well-ground glass stopper, or an Erlen- meyer flask having a specially flanged neck for the iodine test. Reweigh the burette or beaker and determine the amount of sample used. Add 1toccof chloroform and whirl the bottle to dissolve the sample. Add 1occ of chloroform to each of two empty bottles like that used for the sample. Add to each bottle 25 cc of the Hanus solution (see Reagents 5) and let stand with occasional shaking for one-half hour. Add 10 ce of the 15 per cent potassium iodide solution and 100 ce of water, and titrate with standard sodium thiosulphate, using starch as indicator. The titration on the two blank tests should agree within 0.1 cc. From the difference be- tween the average of the blank titrations and the titration on the sample and the iodine value of the thiosulphate solution, calculate the iodine number of the sample tested. (Iodine number is centi- grams of iodine to1 gof sample.) If the iodine number is less than 170, the oil does not meet the specification. (1) COARSE PARTICLES AND “SKINS.’’—Weigh out an amount of paste containing 25 g of pigment (see d), add 1oocc of kero- sene, wash through No. 325 screen, and weigh the residue as in 3 (c). 5. REAGENTS. (2) Acid AMMONIUM ACETATE SOLUTION.—Mix 150 cc of 80 per cent acetic acid, 100 ce of water, and 95 cc of strong ammo- nium (specific gravity 0.90). (6) DICHROMATE SOLUTION.—Dissolve 100 g sodium dichro- mate (Na,Cr,0,2H,O) or potassium dichromate (K,Cr,O,) in water and dilute to 1,000 cc. (c) URANYL INDICATOR FOR ZINC TIrRATION.—A 5 per cent solution of uranyl nitrate in water or a 5 per cent solution of uranyl acetate in water made slightly acid with acetic acid. (d) STANDARD PoTASSIUM FERROCYANIDE.—Dissolve 22 g of the pure salt in water and dilute to 1,000 cc. To standardize, 8 Circular of the Bureau of Standards transfer about 0.2 g (accurately weighed) of pure metallic zine or freshly ignited pure ZnO to a 400 cc beaker. Dissolve in 10 cc of HCland 20 cc of water. Drop in a small piece of litmus paper, add NH,OH until slightly alkaline, then add HCI until just acid and finally add 3 cc of strong HCl. Dilute to about 250 cc with hot water and heat nearly to boiling. Run in the ferrocyanide solution slowly from a burette with constant stirrmg until a drop tested on a white porcelain plate with a drop of the uranyl indica- tor shows a brown tinge after standing 1 minute. A blank should be run with the same amounits of reagents and water as in the stand- ardization. The amount of ferrocyanide solution required for the blank should be subtracted from the amounts used in stand- ardization and in titration of the sample. The standardization must be made under the same conditions of temperature, volume and acidity as obtain when the sample is titrated. (ec) BARtuM CHLORIDE SoLuTIOoN.—Dissolve 100 g of pure crystallized barium chloride in water and dilute to 1,000 cc. (f) STANDARD SODIUM THIOSULPHATE SOLUTION.— Dissolve pure sodium thiosulphate in distilled water that has been well boiled to free it from CO, in the proportion of 24.83 g of crystallized sodium thiosulphate to 1,000 cc of the solution. It is best to let this solution stand for about two weeks before standardiz- ing. Standardize with pure resublimed iodine. (See Treadwell- Hall, Analytical Chemistry, vol. 2, 3d ed., p. 646.) This solu- tion will be approximately decinormal, and it is best to leave it as it is after determining its exact iodine value, rather than to at- tempt to adjust it to exactly decinormal strength. Preserve in a stock bottle provided with a guard tube filled with soda lime. (g) Srarcu SOLUTION.—Stir up 2 to 3 g of potato starch or 5 g of soluble starch with 100 ce of 1 per cent salicylic acid solu- tion, add 300 to 400 cc of boiling water, and boil the mixture until the starch is practically dissolved; then dilute to 1 liter. (h) EXTRACTION MIXTURE.—Mix 10 volumes ether (ethyl ether), 6 volumes benzol, 4 volumes methyl alcohol, and 1 volume acetone. (1) AguEOUS Soprum HyprOxIDE.—Dissolve 100 g of NaOH in distilled water and dilute to 300 cc. | (7) PotTasstum IopipE SoLUTION.—Dissolve 150 g of potassium iodide free from iodate in distilled water and dilute to 1,000 cc. (k) Hanus SoLuTION.—Dissolve 13.2 g of iodine in 1,000 cc of glacial acetic acid, 99.5 per cent, which will not reduce chromic acid. Add enough bromine to double the halogen content, de- Specification for Basic Sulphate White Lead, Dry and Paste 9 termined by titration (3 cc of bromine is about the proper amount). ‘The iodine may be dissolved by the aid of heat, but the solution should be cold when the bromine is added. (7) Atconotic Soprum MHyproxipE SoLuTion.—Dissolve pure sodium hydroxide in 95 per cent ethyl alcohol in the propor- tion of about 22 g per 1,000 cc. Letstand ina stoppered bottle. Decant the clear liquid into another bottle, and keep well stop- pered. This solution should be colorless or only slightly yellow when used; it will keep colorless longer if the alcohol is previously treated with NaOH (about 80 g to 1,000 cc) kept at about 50°C. for 15 days, and then distilled. ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. AT 5 CENTS PER COPY Ve . if, 3 s v, DEPARTMENT OF COMMERCE BUREAU OF STANDARDS S. W. STRATTON, Director CIRCULAR OF THE BUREAU OF STANDARDS No. 86 [2d edition. October 6, 1922] UNITED STATES GOVERNMENT SPECIFICATION FOR TURPENTINE (Gum Spirits and Wood Turpentine) FEDERAL SPECIFICATIONS BOARD STANDARD SPECIFICATION NO. 7 This specification was officially adopted by the Federal Specifications Board, on February 3, 1922, for the use of the Departments and Independent Establish- ments of the Government in the purchase of materials covered by it. CONTENTS Page Paes meet Yr cid Sia as seltieek Aes aod ea MO gethn OO I 2. Detection and removal of separated water...... 2.0... ec cece cece ececceccces 2 I Re i, os card as Ga ee ads 2 Pre ermcery Se MettAarION <6. 2. oe, Oe ROR Ee VE Woe! ED 3 Seen pe Ibiasl? oii Ale. ctr ib hoo Giese teste Be) 1. GENERAL These specifications apply both to the turpentine which is distilled from pine oleoresins, commonly known as gum Spirits or spirits of turpentine, and to turpentine commonly known as wood turpentine, which is obtained from resinous wood, whether by steam or by destructive distillation. When ordering under these specifications, the purchaser shall specify whether (a) gum spirits or (b) wood turpentine is desired. When wood turpentine is specified, it may be stated whether steam or destructively distilled wood turpentine shall be furnished. 7788°—22 2 Circular of the Bureau of Standards Turpentine shall be pure and conform to the following require- ments: APPEARANCE.—Shall be clear and free from suspended matter and water. CoLor.—Shall be ‘‘standard”’ or better. Opor.—Shall be characteristic of the variety of turpentine specified and, if desired, shall conform to the odor of the sample agreed upon. Maximum Minimum Specific gravity, 15.5/15:5° C..i). 6s - he Ga eeeens Refractive index at 20° C........5...... cds ee ees eT Pen 1.480 | Initial boiling point at 760 mm pressure................ 160°C * os fee Distilling below 170° C at 760 mm pressure (per cent)...]............, 90 2. DETECTION AND REMOVAL OF SEPARATED WATER Draw a portion by means of a glass or metal container with a - removable stopper or top, or with a “‘ thief,’ from the lowest part of the container, or by opening the bottom valve of the perfectly level tank car. If water is found to be present, draw it all out, record the quantity, and deduct it from the total volume of liquid delivered. 3. SAMPLING The method of sampling given under (a) should be used when- ever feasible. When method (a) is not applicable, method (0), (c), or (d) is to be used according to the special conditions that obtain. (a) While Loading Tank Car or While Filling Containers for Shipment.—Samples shall be drawn by the purchaser’s inspector at the discharge pipe where it enters the receiving vessel or vessels, The‘ composite sample shall be not less than 5 gallons and shall consist of small portions of not more than 1 quart each taken at regular intervals during the entire period of loading or filling. — Specifications for Turpentine 3 The composite sample thus obtained shall be thoroughly mixed and from it three samples of not less than 1 quart each shall be placed in clean, dry, glass bottles or tin cans, which must be nearly filled with the sample and securely stoppered with new, clean corks or well-fitting covers or caps. “These shall be sealed and distinctly labeled by the inspector; one shall be delivered to. the buyer, one to the seller, and the third held for check in case of dispute. (6) From Loaded Tank Car or Other Large Vessel.—The com- posite sample taken shall be not less than 5 gallons and shall consist of numerous small samples of not more than 1 quart each taken from the top, bottom, and intermediate points by means of a metal or glass container with removable stopper or top. This device, attached. to a suitable pole, is lowered to the various desired depths, when the stopper or top is removed and the con- tainer allowed to fill. The sample thus obtained is handled as in (a). (c) Barrels and Drums.—Barrels and drums shall be sampled aiter gaging contents. Five per cent of the packages in any ship- ment or delivery shall be represented in the sample. Thoroughly mix the contents of each barrel to be sampled by stirring with a clean rod and withdraw a portion from about the center by means of a “thief” or other sampling device. The composite sample thus obtained shall be not less than 3 quarts, shall consist of equal portions of not less than one-half pint from each package sampled, and shall be handled asin (a). Should the inspector suspect adul- teration, he shall draw the samples from the suspected packages. (dq) Small Containers, Cans, Etc., of 10 Gallons or Less.—T'hese should be sampled, while filling, ea method (a) whenever possible; but in case this is impossible the composite sample taken shall be not less than 3 quarts. This shall be drawn from at least five packages (from all when fewer), and in no case from less than 2 per cent of the packages. The composite sample thus taken shall be thoroughly mixed and subdivided as in (a). 4. LABORATORY EXAMINATION Samples will, in general, be tested by the following methods; but the purchaser reserves the right to apply any additional tests or use any available information to ascertain whether the material meets the specifications: (a) Appearance.—Examine to determine compliance with the specifications. A Circular of the Bureau of Standards (b) Color.—Fill a 200 mm perfectly flat-bottomed colorimeter tube, graduated in millimeters, to a depth of from 40 to 50 mm with the turpentine to beexamined. Place the tube in a colorim- eter and place on or under it a No. 2 yellow Lovibond glass. Over or under a second graduated tube in the colorimeter, place a No. 1 yellow Lovibond glass and run in the same turpentine until the color matches as nearly as possible the color in the first tube. Read the difference in depth of the turpentine in the two tubes. If this difference is 50 mm or more, the turpentine is “standard’’ or better. (c) Odor.—Determine’ by comparison with several samples of known purity, which have been kept in the dark in completely filled, well-stoppered bottles and are free from separated water. (d) Specific Gravity Determine at 15. 5/15.5° C, in a pycnom- eter accurately standardized and having a capacity of at least 25 cc, or by any other equally accurate method. (e) Refractive Index.—Determine refractive index at 20° C with an accurate instrument. When the refractive index is determined at any other temperature, the readings obtained shall be corrected to 20° C by adding to or by subtracting from the actual reading 0.00045 for each degree centigrade that the temperature at which the determination was made is, respectively, above or below 20° C. (f) Distillation —Apparatus.*—C ondenser.—The type of appa- ratus (see Fig. 1) adopted by the American Society for Testing Mate- rials for the distillation of paint thinners other than turpentine, substituting for the thermometer there described? an immersed ther- mometer such as is described below, is preferred. In case the A.S.’T. M. distillation apparatus is not available, use an ordinary straight glass-tube condenser, about 22 inches long, with 16 inches in contact with the cooling water. The end of the condenser tube should be fitted with an adapter or should be bent down to a nearly vertical position, and the tip should be cut off or ground down at an acute angle. The tip should extend a short distance into the receiving cylinder. Flask.—Comparable results can be obtained only by using flasks of the same dimensions. ‘The distilling flask used shall be the standard Engler flask, as used for petroleum distillation, having the following dimensions: Diameter of bulb, 6.5 cm; cylindrical neck, 15 cm long, 1.6 cm internal diameter; side or vapor tube, 10 cm long, 0.6 cm external diameter, attached to ee a ee 1 Fig. 1. 2A.S. T. M. Standards, p. 607; roz8. Specifications for Turpentine 5 . neck at an angle of 75°, so that when the flask contains its charge of 100 ce of oil the surface of the liquid shall be 9 cm below the bottom of the junction of the side tube and neck. Support for Flask.—Support the flask on a plate of asbestos 20 cm in diameter, having an opening 4 cm in diameter. in its: center, and heat with an open flame. Surround the flask and burner with a shield to prevent fluctuation in the temperature of the neck of the flask. Or, support the flask in a metal cup, 15 to 20 cm in diameter, containing high-boiling mineral oil or glycerin aD | Fic. 1.—Distillation apparatus and fitted with a concave cover having in the center a circular opening 54 to6 cmin diameter. In all cases take the necessary precautions to prevent fluctuation in temperature in the neck of the flask. Thermometer.—The thermometer used for turpentine distillation shall conformi to the following specifications: : It shall be graduated from 145° to at least 200° C in 0.2° inter- vals. Thermometers graduated above 200° C may be used, pro- vided they also comply with the following requirements: Length, bottom of thermometer to 175° mark, not more than 8 nor less than 6 Circular of the Bureau of Standards 6.5 cm. Length, top of bulb to 145° mark, not less than 1.5 cm. | Length, 145 to 175° mark, not more than 6 cm. The thermometer shall be made of suitable thermometric glass and thoroughly annealed, so that the scale errors will not increase after continued heating. | The thermometer shall be filled above the mercury with an inert gas, with sufficient pressure above the mercury column to prevent breaking of the column. It shall have a reservoir at the top, so that the pressure will not become excessive at the highest tem- perature. Every fifth graduation shall be longer than the intermediate ones, and the marks shall be numbered at each interval of 5°. The graduation marks shall be clear-cut and fine and the number- ing clear-cut and distinct. . The error at any point on the scale shall not exceed +0.5° CG when tested for total immersion of the mercury column. Receiving Cylinder.—Collect the distillate in an accurately grad- uated so or 100 ce cylinder. The so-called normal or precision cylinder of 50 cc capacity, having an internal diameter of 1.5 cm and graduated in 0.2 cc, is preferred. If a cylinder with larger inside diameter is used, a pasteboard cover should be placed over the top and surround the condenser tube. OPERATION.—Place 100 ce of the turpentine and several small pieces of pumice (or glass) in the distilling flask, fit the thermom- eter so that the top of the mercury bulb is level with the bottom of the side tube, and the 175° C (347° F) mark is below the cork. Place the flask in position on the asbestos board or oil bath and — connect with the condenser. Apply the heat cautiously at first, and, when distillation begins, regulate the heat so that the tur- pentine distills at the rate of not less than 4 nor more than 5 cc per minute (approximately two drops per second). The initial boiling point is the thermometer reading at the instant when the first drop falls from the end of the condenser. Discontinue dis- tillation when the temperature reaches 170.0° C (338° F), or an equivalent thereof, depending on the atmospheric pressure, as outlined below; let the condenser drain and read the percentage distilled. The percentage distilled below successive selected temperatures and the temperature at which each successive 10 ce. distills may also be determined, if desired, making the necessary correction 0 the temperature for variations in atmospheric pressure. _ Ss 2 a Specifications for Turpentine 4 CORRECTION FOR VARIATION IN ATMOSPHERIC PRESSURE.— Since distillation results are comparable only when obtained under exactly the same pressure conditions, turpentine shall be distilled at that pressure which, at room temperature, is equivalent to a pressure of 760 mm of mercury ato°C. Whenever the atmos- pheric pressure after correcting to 0° C is other than 760 mm, a correction must be made. Since alteration of the pressure in the distilling system requires rather complicated apparatus, it is simpler to alter the temperature observation points to correspond to the prevailing pressure. To determine what the atmospheric pressure at the prevailing room temperature, or at the temperature of the barometer, would be at 0° C, read the barometer and thermometer alongside when about to begin distillation. Refer to Table 1, page rz. Under the column nearest the observed pressure reading, and on the line nearest the observed temperature of the barometer will be found the correction which must be subtracted from the observed pres- sure reading to obtain the equivalent, or true, reading at 0° C. The distilling temperature of turpentine is affected plus (-) or minus (—) 0.057° C for each millimeter variation of the barometer above or below the normal 760 mm ato° C2 If the barometer reading, after correcting to 0° C, is below 760 mm, the turpen- tine will distill at a slightly lower temperature than under normal pressure. Therefore, the temperature recorded at the beginning of distillation (and any others observed during the course of the distillation) must be corrected to get its équivalent at normal pressure. ‘The final temperature observation point (170° C of the specifications) must be altered accordingly to get its equiva- lent at the pressure (corrected to 0° C) at which distillation is made. For example, if the barometer reading, after correcting to o°® C, is 750 mm, the correction of the observed initial distilling temperature will be 0.057 10=0.6° C approximately. If the reading of the thermometer when the turpentine begins to distill is 155.6° C, the corrected initial distilling temperature will be 155.6°+0.6°=156.2° C. Furthermore, the temperature ob- servation point at end of distillation (170.0° C at 760 mm) must be altered to the same extent. Since the turpentine is distilling 0.6° C below what it would at normal pressure, distillation must § Landolt-Bornstein Physikalisch-Chemische Tabellen, Ed. 4, Table 127, p. 43 ce 8 Circular of the Bureau of Standards be discontinued at 0.6° C below the specified limit of 170.0° C to determine the percentage distilling below 170.0° C. , If the barometer reading corrected to 0° C is above 760 mm, subtract the temperature correction from the observed ther- mometer reading to determine the initial distilling point, and continue distillation to 170.0° C plus the correction to determine the percentage distilling below 170.0° C. (g) Polymerization.—Place 20 cc of 38 N (equivalent to 100.92 per cent H,SO,) sulphuric acid in a graduated, narrow-necked Babcock flask, stopper, and place in ice water to cool. Add slowly, from a pipette, 5 cc of the turpentine to be examined. Gradually mix the contents, keeping warm, but being very care- ful that the temperature does not rise above 60° C. When the mixture no longer warms up on shaking, agitate thoroughly and place the flask in a water bath and heat at 60 to 65° C for not less than 10 minutes, keeping the contents of the flask thoroughly mixed by vigorous shaking for one-half minute each time, six times during the period. Do not stopper the flask after the turpentine has been added, as it may explode. Cool to room temperature, fill the flask with concentrated sulphuric acid until the unpolymerized oil rises into the graduated neck and centri- fuge from four to five minutes at not less than 1200 r. p. m., or for 15 minutes at 900 r. p. m., or allow to stand, lightly stop- pered, for 12 hours. Calculate the percentage, note the consist- ency and color, and determine the refractive index (at 20° C) of the unpolymerized residue. The consistency should be viscous and the color straw or darker. REAGENT FOR TESTING.—In a weighed glass-stoppered bottle (the regular 2'%4-liter acid bottle is of a convenient size) mix ordinary concentrated sulphuric acid (sp. gr. 1.84) with fuming sulphuric acid. If the fuming acid used contains 50 per cent excess SO,, the ratio of one part, by weight, of the former to three-fourths of a part, by weight, of the latter will give a mix- ture slightly stronger than the required strength. To determine ‘the exact strength of this mixture in terms of H,SO,, weigh exactly, in a weighing pipette of about 10 ce capacity, approxi- mately 20 g of the acid. Allow it to flow down the sides of the neck into a 1o00-cec volumetric flask containing about 200 ce of distilled water. When the pipette has drained, wash all traces of the acid remaining in the pipette into the flask, taking precau- tions to prevent loss of SO,, and make up to the mark. Titrate Specifications for Turpentine 9 20-cc portions, drawn from a burette, against half normal alkali. Calculate the concentration in terms of the percentage of H,SO, in the sample taken. In the same way determine the percentage of H,SO, in the stock of ordinary concentrated acid (sp. gr. 1.84). From these data calculate the quantity of the latter which must be added to the quantity of mixed acid in the weighed bottle to bring it to a concentration, in terms of H,SO,, of 100.92 per cent. After adjusting the concentration by the addition of the ordinary sulphuric acid, thoroughly shake the bottle of mixed acid and again de- ‘termine its concentration. The al- lowable variation is + 0.05 per cent HpO).s Eimally as a check run a polymerization test on gum turpen- tine known to be pure. The residue should fall below 2 per cent. Special precautions must be taken to prevent dilution of this acid by the absorption of atmospheric mois- ture. The arrangement shown in Fig. 2 is most suitable for storing and delivering measured quantities of this reagent. With the three-way stopcocks A and B in the position shown, acid is siphoned into the pipette P, the dis- » placed air passing into R. To empty the pipette, A and B are turned to the position shawn by the broken lines, air passing in at a. The acid adhering to the walls of the pipette dries this air so that when it passes into R on again filling the pipette there is no accumulation of moisture in the acid remaining in the reser- voir. If such arrangement is not to be had, the acid should be kept in well-fitting glass-stoppered bottles of not more than one- _ half liter capacity. Fic. 2.—Acid bottle and pipette vik jah ue. wey J 5 ? Ty 3 wy stoarsQ-eeb ih = f - 4 oe FHS ante aay as) _ : : ae ’ a pissin ® Se near ee eee 4 elo eile d y m sues) na EAR a er oe iiareen vege ‘ ? ek . ie ae ey Sa - x i ei £ He e>4 oe Sei TY 4 > ; “4 “~~ + . * ad t; : o * Ps : t ee t “Rae othe y * : ; = - : * % ; " . % ; q $ : q a : a as ) “ x ‘ ; ( : - Be, , iy j i et £ . , ° t y M ‘, : oer 4 : © + F i Pees ‘ “ cm ’ 4 ™ . : . a ¥ * = Fi > 4 ’ is 7 ( ‘ae E . . ‘ aw ; rt % + et ? ef * : Py t } =) Mas + es jhe Po ay -. * : : terse ; ’ wy, HeRS 2 . a me 2 . i os 7 we FAME RR hi? OE ThE : ETRE OA INE ee f. ¢ i + i » * * DEPARTMENT OF COMMERCE. BUREAU OF STANDARDS. S. W. STRATTON, Director. CIRCULAR OF THE BUREAU OF STANDARDS. No. 87. [2d edition. Issued July 3, 1922.] UNITED STATES GOVERNMENT SPECIFICATION FOR ZINC OXIDE, DRY AND PASTE. FEDERAL SPECIFICATIONS BOARD. STANDARD SPECIFICATION No. 8. ‘This Specification was officially adopted by the Federal Specifications Board on February 3, 1922, for the use of the Departments and Independent Establish- ments of the Government in the purchase of materials covered by it. CONTENTS. Page. NE Be cide ain gS woe Sosa, so sibge dpe td UV aL Oeeh Deon I eR MMM ee OT Tae oe ois oc eres ae Mate Sele tp OVEN ERS OE OU ee a 2 3. Laboratory examination of dry pigment............... BME, UD LN se ER OO 3 Ppaeeoe yeexaniisation Of paste. (. iss 64 a eas dyaet as 1:0 lice nae e en mean tne ernis yl High-leaded. Low-leaded. Maximum. | Minimum. | Maximum. Minimum. pian oe ops ; Per cent. | Percent. | Percent. | Per cent. Zinc oxide (ZnO). . Looe Sa ee LE oS - eS Te aes ee 60° eaten ss ecu 93 Water soluble salts. .......------------@--+--2-2 ctr 1,0 [Sites TO ae ae Total impurities, including MOSUL ss: < ee nese ae oe Linseed Ol... -c-ccn- cco cccn ce weet ewes cee bnncn nec et eine bse 50 ee ee 12.0 Moisture and other volatile matter. ...--.-----------+-----++-- proto (i Rise Ripa Seno ESS Coarse particles and “‘skins”’ (total residue left on No. 325 screen based on pigment) ese 1 a (ees “erst Note.—Deliveries will, in general, be sampled and tested by the following methods, but the pur- chaser reserves the right to use any additional available information to ascertaim whether the material meets the specification. , 2. SAMPLING. S > It is mutually agreed by buyer and seller that a single package out of each lot of not more than 1,000 packages shall be taken as representative of the whole. ; With the dry pigment, the package’ is to be opened by the in- spector and a sample of not less than 5 pounds taken at random from the contents and sent to the laboratory for test. With the paste, whenever possible, an original unopened con- tainer shall be sent to the laboratory, and when this is for any reason not done, the inspector shall determine, by thorough testing with a paddle or spatula, whether the material meets the requirement regarding not caking in the container. (See 4 (a.) After assuring himself that the paste is not caked in the con- tainer, the inspector shall draw a sample of not less than 5 pounds of the thoroughly mixed paste, place it in a clean dry metal or glass container, which must be filled with the sample, closed with Specification for Leaded Zinc Oxide, Dry and Paste 3 a tight cover, sealed, marked, and sent to the laboratory for test with the inspector’s report on caking in container. When requested, a duplicate sample may be taken from the same package and delivered to the seller, and the inspector may take a third sample to hold for test in case of dispute. 3. LABORATORY EXAMINATION OF DRY PIGMENT. (a) CoLtor.—Take 5 g of the sample, add 1.5 cc of linseed oil, rub up on a stone slab or glass plate with a flat-bottomed glass or stone pestle or muller to a uniform smooth paste. ‘Treat in a similar manner 5 g of the standard leaded zinc oxide. Spread the two pastes side by side on a clear colorless glass plate and compare the colors. If the sample is as white or whiter than the “standard,” it passes this test. If the ‘‘standard’’ is whiter than the sample, the material does not meet the specification. (6) CoLoR STRENGTH.—Weigh accurately 0.01 g of lampblack, place on a large glass plate or stone slab, add 0.2 cc of linseed oil, and rub up with a flat-bottomed glass pestle or muller; then add exactly 10 g of the sample and 2.5 cc of linseed oil, and grind with a circular motion of the muller 50 times; gather up with a sharp-edged spatula and grind out twice more in a like manner, giving the pestle a uniform pressure. ‘reat another 0.01 g of the same lampblack in the same manner, except that 10 g of standard leaded zinc oxide is used instead of the 10 g of the sam- ple. Spread the two pastes side by side on a glass microscope slide and compare the colors. If the sample is as light as or lighter in color than the ‘‘standard,’’ it passes this test. Ifthe “‘standard”’ is lighter in color than the sainple, the material does not meet the specification. (c). COARSE PARTICLES.'"—Dry in an oven at 105° to 110° C. a 325 screen, cool and weigh accurately. Weigh 10 g of the sample; dry at 1oo° C., transfer to a mortar, add 100 cc kero- sene, thoroughly mix by gentle pressure with a pestle to break up all lumps, wash with kerosene through the screen, breaking up all lumps, but not grinding. After washing with kerosene until all but the particles which are too coarse to pass the screen have been washed through, wash all kerosene from the screen with ether or petroleum ether, heat the screen for one hour at 105° to 110°C., cool and weigh. 4 1 For a general discussion of screen tests of pigments and data regarding many pigments on the market, see Circular No. 148 of the Educational Bureau, Scientific Section, Paint Manufacturers’ Association of the U.S. 4 Circular of the Bureau of Standards (d) QUALITATIVE ANALYsSIS.—Test for matter insoluble in hydro- chloric acid, lead, calcium, carbon dioxide, etc., by regular methods of qualitative analysis. (e) MoIstuRE.—Place 1 g of the sample in a wide-mouth short weighing tube provided with a glass stopper. Heat with stopper removed for two hours at a temperature between 105 and 110° C. Insert stopper, cool, and weigh. Calculate loss in weight as moisture. | (f) WATER SOLUBLE SaLts.—To 10 g of pigment in a 500 cc volumetric flask, add 200 cc of water, boil for five minutes, nearly fill the flask with hot water, allow to cool, fill to mark, mix, filter through a dry paper, discard the first 50 ce of filtrate, transfer 100 cc of the filtrate (corresponding to 2 g of sample) to a weighed dish, evaporate to dryness, heat for one hour in an oven at 105 to 110° C., cool, and weigh, calculate to percentage of water soluble salts. (g) ZINC OxIDE.— Weigh accurately about 0.3 g of the pigment, transfer to a 400 ce beaker, add 30 cc of hydrochloric acid (1 :2), boil for two or three minutes, add 200 ce of water and a small piece of litmus paper; add ammonium hydroxide until slightly alkaline, render just acid with hydrochloric acid, then add 3 ce of strong hydrochloric acid, heat nearly to boiling, and titrate with standard potassium ferrocyanide as in standardizing the solution. (See Reagents 5 (d).) Calculate total zinc as ZnO. (h) CALCULATIONS.—If, as will be the case with material com- plying with the specification, no metals but zine and lead are found by qualitative tests, add the percentage of ZnO, moisture, and water soluble salts and subtract the sum from 100. Call the remainder ‘‘normal and basic lead sulphate.”’ 4. LABORATORY EXAMINATION OF PASTE. (2) CAKING IN ConTAINER.—When an original package is re- ceived in the laboratory, it shall be weighed, opened, and stirred with a stiff spatula or paddle. ‘The paste must be no more diffi- cult to break up and show no more caking than a normal good grade of leaded-zinc oxide paste. The paste shall be finally thoroughly mixed, removed from the container, the container wiped clean, and weighed. This weight subtracted from the weight of the original package gives the net weight of the con- tents. A portion of the thoroughly mixed paste shall be placed in a clean container and the portions for the remaining tests promptly weighed out. Specification for Leaded Zinc Oxide, Dry and Paste 5 (6) Mrxine wiry LINSEED O1L.—One hundred grams of the paste shall be placed in a cup, 35 ce of linseed oil added slowly with careful stirring and mixing with a spatula or paddle, the resulting mixture must be smooth and of good brushing consistency. (c) MOISTURE AND OTHER VOLATILE MaTTER.—Weigh accu- rately from 3 to 5 g of the paste into a tared flat-bottomed dish about 5 cm in diameter, spreading the paste over the bottom. Heat at 105 to 110° C. for one hour, cool, and weigh. Calculate loss in weight as percentage of moisture and other volatile matter. (d) PERCENTAGE OF PIGMENT.—Weigh accurately about 15 ¢ of the paste into a weighed centrifuge tube. Add 20 to 30 cc “extraction mixture’’ (see Reagents), mix thoroughly with a glass rod, wash the rod with more of the extraction mixture, add suffi- cient of the reagent to make a total of 60 cc in the tube. Place the tube in the container of a centrifuge, surround with water, and counterbalance the container of the opposite arm with a similar tube or a tube with water. Whirl at a moderate speed until clear. Decant the clear supernatant liquid. Repeat the extraction twice with 4o cc of extraction mixture, and once with 40 cc of ether. After drawing off the ether, set the tube in a beaker of water at about 80° C. or on top of a warm oven for 10 minutes, then in an oven at 110 to 115° C. for two hours. Cool, weigh, and calculate percentage of pigment. (¢) EXAMINATION OF PiGMENT.—Grind the pigment from (d) to a fine powder, pass through a No. 80 screen to remove any ‘“skins,’’ preserve in a stoppered tube, and apply tests 3 (d), (f), (g), and (h). If required, apply tests 3 (a) and (6) in comparison with a portion of pigment extracted from the standard paste in exactly the same manner as in extracting the sample. (7) PREPARATION OF Farry Acips.—To about 25 g of the paste in a porcelain casserole, add 15 cc of aqueous sodium hy- droxide (see Reagents) and 75 cc of ethyl alcohol; mix, and heat uncovered on a steam bath until saponification is complete (about one hour). Add 100 cc of water, boil, add sulphuric acid of specific gravity 1.2 (8 to 10 cc in excess); boil, stir, and trans- fer to a separatory funnel, to which some water has been pre- viously added. Draw off as much as possible of the acid aqueous layer and lead sulphate precipitate, wash once with water, then add 50 cc of water and 50 cc of ether. Shake very gently with a whirling motion to dissolve the fatty acids in the ether, but not violently, so as to avoid forming an emulsion. Draw off the 6 Circular of the Bureau of Standards aqueous layer and wash the ether layer with one 15 cc portion of water and then with 5 ce portions of water until free from sul- phuric acid. Then draw off completely the water layer. Transfer the ether solution to a dry flask, add 25 to 50 g. of anhydrous sodium sulphate. Stopper the flask and let stand with occa- sional shaking at a temperature below 25° C. until the water is completely removed from the ether solution, which will be shown by the solution becoming perfectly clear above the solid sodium sulphate. Decant this clear solution (if necessary, through a dry filter paper) into a dry “1oo cc Erlenmeyer flask. Pass a rapid current of dry air (pass through CaCl, tower) into the mouth of the Erlenmeyer flask and heat to a temperature below 75° C. on a dry hot plate until the ether is entirely driven off. Novte.—It is important to follow all of the details, since ether generally contains ~ alcohol and after washing with water always contains water. It is very difficult to remove water and alcohol by evaporation from fatty acids, but the washing of the ether solution and subsequent drying with anhydrous sodium sulphate removes both water and alcohol. Ether, in the absence of water and alcohol, is easily removed from fatty acids by gentle heat. The fatty acids prepared as above should be kept in a stoppered flask and examined at once. | (g) Test FOR MINERAL OI, AND OTHER UNSAPONIFIABLE MAT- TER.—Place 10 drops of the fatty acid (f) in a 50 cc test tube, add 5 cc of alcoholic soda (see Reagents), boil vigorously for five minutes, add 4o cc of water and mix; a clear solution indicates that not more than traces of unsaponifiable matter are present. If the solution is not clear, the oil is not pure linseed oil. (hk) IlopInE NUMBER oF Farry Acrps.—Place a small quantity of the fatty acids (/) in a small weighing burette or beaker. Weigh accurately. Transfer by dropping about 0.15 g (0.10 to 0.20 g) to a 500 cc bottle having a well-ground glass stopper or an Erlen- meyer flask having a specially flanged neck for the iodine test. Reweigh the burette or beaker and determine the amount of sample used. Add soccof chloroform. Whirl the bottle to dissolve the sample. Add ro cc of chloroform to two empty bottles like that used for the sample. Add to each bottle 25 cc of the Hanus solu- tion (see Reagents) and let stand with occasional shaking for one- half hour. Add 10 ce of the 15 per cent potassium iodide solu- tion and 100 cc of water and titrate with standard sodium thio- sulphate, using starch as indicator. ‘The titrations on the two blank tests should agree within 0.1 cc. From the difference be- tween the average of the blank titrations and the titration on the Specification for Leaded Zinc Oxide, Dry and Paste y, sample. and the iodine value of the thiosulphate solution calculate the iodine number of the sample tested. (Iodine number is centi- grams of iodine to 1 g of sample.) If the iodine number is less than 170, the oil does not meet the specification. (1) COARSE PARTICLES AND ‘“‘SKINS.’’—Weigh an amount of paste containing 10 g of pigment (see 4(d)), add roo g of kerosene and wash through a No. 325 screen. The residue is reported as ‘““coarse particles and ‘skins.’ ”’ 5. REAGENTS. (a) URANYL INDICATOR FoR Zinc TITRATION.—A 5 per cent solution of uranyl nitrate in water or a 5 per cent solution of uranyl acetate in water made slightly acid with acetic acid. (b) STANDARD PoTasstuM FERROCYANIDE.—Dissolve 22 g of the pure salt in water and dilute to 1,000 cc. To standardize, transfer about 0.2 g (accurately weighed) of pure metallic zinc or freshly ignited pure zinc oxide to a 400 cc beaker. Dissolve in 10 ec of hydrochloric acid and 20 cc of water. Drop in a small piece of litmus paper, add ammonium hydroxide until slightly alkaline, then’ add hydrochloric acid until just acid and then add 3 ec of strong hydrochloric acid. Dilute to about 250 cc with hot water and heat nearly to boiling. Run in the ferrocyanide solution slowly from a burette with constant stirring until a drop tested on a white porcelain plate with a drop of the uranyl indi- cator shows a brown tinge after standing one minute. A blank should be run, using the same amounts of reagents and water as in the standardization. The amount of ferrocyanide solution re- quired for the blank should be subtracted from the amounts used in standardization and in titration of the sample. The standardi- zation must be made under the same conditions of temperature, volume, and acidity as obtain when the sample is titrated. (c) BartuM CHLORIDE SoLuTION.—Dissolve 100 g of pure crystallized barium chloride in water and dilute to 1,000 cc. (d) STANDARD SODIUM THIOSULPHATE SOLUTION.— Dissolve pure sodium thiosulphate in distilled water that has been well boiled to free it from carbon dioxide, in the proportion of 24.83 g of crystallized sodium thiosulphate to 1,000 cc of the solution. It is best to let this solution stand for about two weeks before stand- ardizing. Standardize with pure resublimed iodine (See Ana- lytical Chemistry, Treadwell-Hall, 2, 3d ed., p. 646). This solu- tion will be approximately decinormal, and it is best to leave it as 8 Circular of the Bureau of Standards it is after determining its exact iodine value, rather than to attempt to adjust it to exactly decinormal. Preserve in a stock bottle provided with a guard tube filled with soda lime. (ec) STtaRCH SOLUTION.—Stir up 2 to 3 g of potato starch or 5 g of soluble starch with 100 cc of 1 per cent salicylic acid solution, add 300 to 400 cc of boiling water, and boil the mixture until the starch is practically dissolved, then dilute to 1 liter. (f) EXTRACTION MIXTURE.— 10 volumes ether (ethyl ether). 6 volumes benzol. 4 volumes methyl alcohol. 1 volume acetone. (g) AguEOUs SopiumM HyproxIbE.—Dissolve 100 g of sodium hydroxide in distilled water and dilute to 300 cc. (hk) Porasstum IopIDE SoLUTION.— Dissolve 150 g of senate iodide free from iodate, in distilled water and dilute to 1,000 cc (1) Hanus SOLUTION.—Dissolve 13.2 g of iodine in 1,000 ce of 99.5 per cent glacial acetic acid, which will not reduce chromic acid. Add enough bromine to double the halogen content, deter- mined by titration (3 cc of bromine is-about the proper amount). The iodine may be dissolved by the aid of heat, but the solution should be cold when the bromine is added. (7) ALCOHOLIC SopIUM HypDROXIDE SOLUTION.—Dissolve pure sodium hydroxide in 95 per cent ethyl alcohol in the proportion of about 22 g per 1,000 cc. Let stand in a stoppered bottle. Decant the clear liquid into another bottle, and keep well stop- pered. This solution should be colorless or only slightly yellow when used, and it will keep colorless longer if the alcohol is pre- viously treated with sodium hydroxide (about 80 g to 1,000 cc), kept at about 50° C. for 15 days, and then distilled. ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. AT 5 CENTS PER COPY WASHINGTON : GOVERNMENT PRINTING OFFIC : 1924 DEPARTMENT OF COMMERCE. Ant BUREAU OF STANDARDS. S. W. STRATTON, Director. CIRCULAR OF THE BUREAU OF STANDARDS. No. 89. {2d edition. Issued July 3, 1922.] UNITED STATES GOVERNMENT SPECIFICATION FOR WHITE PAINT AND TINTED PAINTS MADE ON A WHITE BASE, SEMIPASTE AND READY MIXED.’ Oe FEDERAL SPECIFICATIONS BOARD. STANDARD SPECIFICATION NO. 10. This Specification was officially adopted by the Federal Specifications Board on February 3, 1922, for the use of the Departments and Independent Establish- ments of the Government in the purchase of materials covered by it. CONTENTS. Page ee te Bi) omit bare cert ane (29 heir © or RM ERE SU. haley, IR (cle dew Ae eva «td Rae putilye ev oe aWidle 9 ag . 3 9) LGboraveny GmamINALON oem paste... 2. ck ek eee pee cee ne renne« 3 ee aie sere. SEI. SIRO. OR LAA, Ba CAB AEA, ot 6 Ra hanoratory ecamination—Mixed paint... topes) 1s rept srca'y sald. oh Dyas 7 Pe a eg RN i hn face 5 ob ie ain Be hk ty hs LEMAR no pele aa pekaed 4 8 1. GENERAL. White paint and tinted paints made on a white base may be ordered either in the form of semipaste pigment ground in linseed oil or of ready-mixed paint. The semipaste shall be purchased by net weight, the ready-mixed paint either by weight or volume (231 cubic inches to the gallon). (a) PIGMENT.—The pigment shall be composed of: Maximum.| Minimum. Per cent. | Per cent. White lead (basic carbonate, basic sulphate, or a mixture thereof)................ 70 45 Zanic Orde (ZNO)... ...). 5. ¢ ota» Domandd eaigawdgea sh aaah. pee Suaisbislent. sige 16S. Beh 55 30 White mineral pigments, containing no lead or zinc compounds, pure tinting MOLE GY TUIXCUITC TMCLOO! 5 icin ser da.c sin vile ae a0 oie gna e 4.0 p inih exer Vintharein) Dy opicew eiphe 15 0 1It is believed that this specification admits practically all high-grade prepared paints generally avail- ablein the United States, and which are therefore obtainable without requiring manufacturers to make up speciallots. On large contracts for which paint will be specially made, the purchaser may require the bidder to submit the formulaof the paint he proposes tofurnish as conforming to the specifications. 109840°—22—.-1 2 Circular of the Bureau of Standards In no case shall the sum of the basic lead carbonate, basic lead sulphate, and zinc oxide be less than 85 per cent. The lead and zinc pigments may be introduced in the form of any mixture preferred of basic carbonate white lead, basic sulphate white lead, zinc oxide, or leaded zinc, provided the above requirements as to composition are met. The total lead dissolved by dilute acetic acid and hot acid ammonium acetate, weighed as lead sulphate, and this weight multiplied by the factor 0.883 shall be considered white lead. (It is not possible to determine the amount of lead carbonate and lead sulphate when carbonates or sulphates of other metals such as calcium are present. Also neither basic lead carbonate nor basic lead sulphate are definite compounds. The factor to convert PbSO, to (PbCO,), Pb(OH), is 0.854, to convert PbSO, to PbSO,PbO is 0.868, and to convert PbSO, to (PbSO,), PbO is 0.913. The arbitrary factor used under this specification is the mean of the largest and smallest of these three factors. (6) Ligurp.—The liquid in semipaste paint shall be entirely pure raw or refined linseed oil; in ready-mixed paint it shall con- tain not less than go per cent pure raw linseed oil, the balance to be combined drier and thinner. The thinner shall be turpentine, volatile mineral spirits, or a mixture thereof. (c) SEMIPASTE.—Semipaste shall be made by thoroughly grind- ing the pigment with pure raw or refined linseed oil. The semipaste as received and three months thereafter shall be not caked in the container and shall break up readily in linseed oil to form a smooth paint of brushing consistency. It shall mix readily with linseed oil, turpentine, or volatile mineral spirits, or any combination of these substances, in all proportions without curdling. The color and hiding power when specified shall be equal to that of a sample mutually agreed upon by buyer and seller. The weight per gallon shall be not less than 19.0 pounds. The paste shall consist of: Maximum.) Minimum. Per cent. | Per cent. PUCMENE och, osccve.s a gaievidews ws cae + ete Nite ah el Oke 77 73 LARSOOEPON 5 EY FOR LS so accu bars 5 gs data eM cinema G2 od a2 27 23 Moisture and other volatile matter...... 40 8U02) Sorry. cl a ee at Pi ay Riel a Ph Coarse particles and ‘‘skins”’ (total residue retained on No. 325 screen based on pigment)... oo... ee cutee eek RL RR, Shee ee: 2) 0 ay ery beh cyt (dq) Reapy-MrxEp Parint.—Ready-mixed paints shall be well ground, shall not settle badly or cake in the container, shall be readily broken up with a paddle to a smooth uniform paint of good ~ Specification for White Paint 3 brushing consistency, and shall dry within 18 hours to a full oil gloss, without streaking, running, or sagging. The color and hiding power when specified shall be equal to those of a sample mutually agreed upon by buyer and seller. The weight per gallon shall be not less than 1534 pounds. The paint shall consist of: Maximum. | Minimum. Per cent. | Per cent. ee Pea ee MERA, GSE e 8s S8 559.5 dase tet att Sale SELLE m mY Oslo aiale alee ata eee 52 48 Moisture and other volatile matter ........ 0.02. cece eect entre ett tence et scans DoF tesutseecuas Coarse particles and “‘skins”’ (total residue retained on No. 325 screen based on Mr ettt) os os cdc Ua cs pc re bbe 0 a be wna veo alee nm en le ohare gee Le Och i ete easter (d) Reapy-Mixep Parnt.—Ready-mixed paint shall be well ground, shall not settle badly or cake in the container, shall be readily broken up with a paddle to a smooth uniform paint of good brushing consistency, and shall dry within 18 hours to a full oil gloss, without streaking, running, or sagging. The color and hiding power when specified shall be equal to those of a sample — mutually agreed upon by buyer and seller. The weight per gallon shall be not less than 9 pounds. ‘The paint shall consist of: | Maximum.) Minimum, Ui Sasa 1 ene ea Ce oO SE pier n ee tie Mines Re MEME AN TERT er Lk Liquid (containing at least 80 per cent linseed oil)........... 0... 00s cece eee eee 72 68 WAR BT er OURS al ae ac Gen a et IC re Coke Ca tek ts UC ah weshts he srs 0,3 ickenceny ain Coarse particles and ‘“‘skins”’ (total residue retained on No. 325 screen based on SEES oa Say sins Gclcvp 5.0 Wom OED RA DID RR Res ae Mies eh dace ge LG leew tuacebes Notr.—Deliveries will, in general, be sampled and tested by the following methods, but the purchaser reserves the right to use any additional available information te ascertain whether the material meets the specification. | Specification for Black Patwnt 3 2. SAMPLING. It is mutually agreed by buyer and seller that a single package out of each lot of not more than 1,000 packages shall be taken as representative of the whole. Whenever possible an original unopened container shall be sent to the laboratory, and when this . is for any reason not done, the inspector shall determine by thorough testing with a paddle or spatula whether the material meets the requirements regarding caking in the container. He © shall then thoroughly mix the contents of the container and draw a sample of not less than 5 pounds of the thoroughly mixed paint, place it in a clean, dry metal or glass container, which it shall nearly fill. The container shall be closed with a tight cover, sealed, marked, and sent to the laboratory for test with the inspector’s report on caking. , When requested, a duplicate sample may be taken from the same package and delivered to the seller, and the inspector may take a third sample to hold for test in case of dispute. 3. LABORATORY EXAMINATION—SEMIPASTE. (a) CAKING IN CONTAINER.—When an original package is received in the laboratory it shall be weighed, opened, and stirred with a stiff spatula or paddle. The paste must be no more diffi- cult to break up than a normal good grade of semipaste paint. _ The semipaste shall finally be thoroughly mixed, removed from the container, and the container wiped clean and weighed. This weight subtracted from the weight of the original package gives the net weight of the contents. A portion of thoroughly mixed _ semipaste shall be placed in a clean container and the portions for the remaining tests promptly weighed out. (b) CoLor.—Place some of the paint on a clean clear glass plate. Place some of the standard agreed upon beside the sample on the plate, turn the glass over, and compare the colors. (c) WEIGHT PER GALLON.—From the weight of a known volume of the paste calculate the specific gravity, which multiplied by 8.33 gives the weight in pounds per gallon. Any suitable con- tainer of known volume may be used for the purpose, but a short cylinder of heavy glass with rounded bottom about 75 mm. high and having a capacity of from 125 to 175 cc (a glass cap to keep dust from reagent bottle stopper) is a convenient apparatus for the purpose. The capacity of this vessel is deternined to within Ice. The paste is packed into it until completely full, the top 4 Circular of the Bureau oj Standards leveled off smooth with a spatula, and weighed to +0.5 g. Sub- tract the weight of the empty container and divide the remainder by the number of cubic centimeters representing the capacity of the container. ‘The quotient is the specific gravity, which can be thus determined within +2 in the second decimal place. (d) Mrxtnc wits LinsEED Ou.—One hundred grams of the paste shall be placed in a cup, 70 cc linseed oil added slowly with careful stirring and mixing with a spatula or paddle. ‘The result- ing mixture must be smooth and of good brushing consistency. (ec) MorstuRE AND OTHER VOLATILE MaTTER.—Weigh accu- rately from 3 to 5 g of the paste into a tared flat-bottomed dish about 5 cm in diameter, spreading the paste over the bottom. Heat at 105 to 110° C. for one hour, cool, and weigh. Calculate loss in weight as percentage of moisture and volatile matter. (f) PERCENTAGE OF PicMENT.—Weigh accurately about 15 g of the paste into a weighed centrifuge tube. Add 20 to 30 cc of ‘extraction mixture”? (see reagents), mix thoroughly with a glass rod, wash the rod with more of the extraction mixture, and add sufficient of the reagent to make a total of 60 cc in the tube. Place the tube in the container of a centrifuge, surround with water, and counterbalance the container of the opposite arm with a similar tube or a tube with water. Whirl at a moderate speed until well settled. Decant the clear supernatant liquid. Repeat the extraction twice with 40 cc of extraction mixture and once with 40 cc of ether. After drawing off the ether, set the tube in a beaker of water at about 80° C. or on top of a warm oven for 10 minutes, then in an oven at 110 to 115° C. for two hours. Cool, weigh, and calculate the percentage of pigment. Grind the pigment to a fine powder, pass through a No. 80 screen to remove any skins, and preserve in a stoppered bottle. | (g) PREPARATION OF Farry Actps.—To about 25 g of the paste in a porcelain casserole, add 15 cc of aqueous sodium hydroxide (see reagents) and 75 cc of ethyl alcohol, mix and heat un- covered on a steam bath until saponification is complete (about one hour). Add 100 ce of water, boil, add sulphuric acid of specific gravity 1.2 (8 to 10 cc in excess), boil, stir, and transfer to a separatory funnel to which some water has been previously added. Draw off as much as possible of the acid aqueous layer, wash once with water, then add 50 cc of water and occ of ether. Shake very gently with a whirling motion to dis- solve the fatty acids in the ether, but not so violently as to form » Specification for Black Paini 5 an emulsion. Draw off the aqueous layer and wash the ether layer with one 15 cc portion of water and then with 5 cc portions of water until free from sulphuric acid. Then draw off the water layer completely. ‘Transfer the ether solution to a dry flask and add 25 to 50 g of anhydrous sodium sulphate. Stopper the flask and let stand with occasional shaking at a temperature below 25° C. until the water is completely removed from the ether solu- tion, which will be shown by the solution becoming perfectly clear above the solid sodium sulphate. Decant this clear solution, if necessary, through a dry filter paper, into a dry 100 cc Erlen- meyer flask. Pass a rapid current of dry air (pass through a CaCl, tower) into the mouth of the Erlenmeyer flask and heat to a temperature below 75° C. on a dry hot plate until the ether is entirely driven off. NoTE.—It is important to follow all of the details since ether generally contains alcohol and after washing with water always contains water. It is very difficult to remove water and alcohol by evaporation from fatty acids, but the washing of the ether solution and subsequent drying with anhydrous sodium sulphate removes both water and alcohol. Ether, in the absence of water and alcohol, is easily removed from fatty acids by gentle heat. The fatty acids prepared as above should be kept in a stoppered flask and examined at once. | (h) Test FoR MINERAL Om, AND OTHER UNSAPONIFIABLE MaTTER.—Place 10 drops of the fatty acid (g) in a 50 cc test tube, add 5 cc of alcoholic soda (see reagents), boil vigorously for five minutes, add 40 cc of water, and mix; a clear solution indicates that not more than traces of unsaponifiable matter are present. If the solution is not clear, the oil is not pure linseed oil. (2) opine NuMBER oF Farry Actps.—Place a small quantity of the fatty acids (g) in a small weighing burette or beaker. Weigh accurately. ‘Transfer by dropping about 0.15 g (0.10 to 0.20 g) into a 500 cc bottle having a well-ground glass stopper, or an Erlenmeyer flask having a specially flanged neck for the iodine test. Reweigh the burette or beaker and determine amount of sample used. Add tocc of chloroform. Whirl the bottle to dis- solve the sample. Add 10 cc of chloroform to two empty bottles like that used for the sample. Add to each bottle 25 cc of the Hanus solution (see reagents) and let stand with occasional shaking for one-half hour. Add 1occ of the 15 per cent potassium iodide solution and 100 cc of water, and titrate with standard sodium thiosulphate, using starch as indicator. The titrations on the two blark tests should agree within 0.1 cc. From the 6 Circular of the Bureau of Standards difference between the average of the blank titrations and the titration on the sample and the iodine value of the thiosulphate solution, calculate the iodine number of the sample tested. (Iodine number is centigrams of iodine to 1 g of sample.) If the iodine number is less than 170, the oil does not meet the specification. (7) CoarsH PARTICLES AND Sxins.—Dry in an oven at 105 to 110° C. a No. 325 screen, cool, and weigh accurately. Weigh an amount of semipaste containing 10 g of pigment (see 3 (f)), add 50 cc of kerosene, mix thoroughly, and wash with kerosene through the screen, breaking up all lumps but not grinding. After washing with kerosene until all but the particles too coarse to pass the screen have been washed through, wash all kerosene from the screen with ether or petroleum ether, heat the screen ror one hour at 105 to 110° C., cool, and weigh. 4. ANALYSIS OF PIGMENT. (az) QuatitativE ANALysIs.—Make qualitative analysis follow- ing ordinary methods. (b) Loss on Icnrt10oN.—Ignite 1 g of the pigment in a weighed porcelain crucible until all carbon is consumed. It is best to use gentle heat with free access of air. Cool, weigh, and calculate the percentage of loss on ignition. (c) CARBON AND INSOLUBLE MINERAL MATERIAL.—Place 1 g of the pigment in a porcelain dish, moisten with a few drops of alcohol, add 20 cc of concentrated hydrochloric acid, cover, and heat on steam bath for 15 minutes. Remove cover and evaporate to dryness, moisten with hydrochloric acid, add 25 ce of water, filter on a weighed Gooch crucible, and wash with hot water until the washings are free from lead and iron. Dry the crucible and contents at 105 to 110° C. for 2 hours. Ignite for 7 minutes in a current of dry carbon dioxide (using a Rose crucible cover) with a flame about 20 cm high. Cool ina current of dry carbon dioxide and weigh. ‘Then ignite with free access of air (or in a current of oxygen) until all carbon is consumed. Cool and weigh. The loss in weight is calculated as carbon, and the residue remaining on the Gooch crucible is calculated as insoluble mineral material. (d) Leap OxIpDE AND IRON OxipE.—Determine lead and iron in the filtrate from the carbon determination by any convenient method, calculating lead to Pb,O, and iron to Fe,O,. | Specification for Black Paint 7 5. LABORATORY EXAMINATION—MIXED PAINT. (a) CAKING IN CONTAINER.—Follow the procedure outlined in 3(@), noting that the paint should be no more difficult to break up than a good grade of mixed paint. (6) Cotor.—Follow the procedure outlined in 3(b). (c) WEIGHT PER GAaLLON.—Weigh a clean, dry, 100 ce gradu- ated flask. Fill to the mark with tHe thoroughly mixed paint and weigh again. The increase in weight expressed in grams, divided by 100, gives the specific gravity, which multiplied by 8.33 gives the weight in pounds per gallon. (d) BRUSHING PROPERTIES AND Time oF Dryinc.—Brush the well-mixed paint on a suitable panel, which may be ground glass, steel, or well-filled wood. Note whether the paint works satis- factorily under the brush. Place the panel in a vertical position in a well-ventilated room and let stand for 18 hours. ‘The paint shall be dry, smooth, and free from streaks. — (e) WaTer.—Mix 100 g of the paint in a 300 cc flask with 75 cc of toluol. Connect with a condenser and distill until about 50 cc of distillate has been collected in a graduate. ‘The tempera- ture in the flask should be then about 105 to 110°C. ‘The number of cubic centimeters of water collecting under the toluol in the receiver is the percentage of water in the paint. Material com- plying with the specification should yield less than 0.5 cc. (7) VOLATILE THINNER.—Follow the procedure outlined in 3(e). Correct the result for any water found (see 5(e)) and report the remainder as a volatile thinner. (g) PERCENTAGE OF PiGMENT.—Follow the procedure outlined in 3 (7). (h) Testinc NoNVOLATILE VEHICLE.—Follow the procedure outlined in 3(g), 3(), and 3(2), except that in the preparation of the fatty acids the mixture of paint and alkali is heated on the. steam bath until all volatile thinner is driven off. (1) COARSE PARTICLES AND SKINS.—Follow the procedure out- lined in 3(9). (j) Testinc Picment.—Follow the procedure outlined in 4(a) to 4(d) inclusive. 8 Circular of the Bureau of Standards 6. REAGENTS. (a) EXTRACTION MIXTURE.— ‘ro volumes ether (ethyl ether). 6 volumes benzol. 4 volumes methy] alcohol. 1 volume acetone. (b) Aguzous Sop1um HyproxmeE.—Dissolve roo g of sodium hydroxide in distilled water and dilute to 300 cc. : (c) STANDARD SopruM THIOSULPHATE SOLUTION.—Dissolve pure sodium thiosulphate in distilled water (that has been well boiled to free it from carbon dioxide) in the proportion of 24.83 g of crystallized sodium thiosulphate to 1,000 cc. of the solution. It-is best to let this solution stand for about two weeks before standardizing. Standardize with pure resublimed iodine. (See Treadwell-Hall, Analytical Chemistry, vol. 2, 3d ed., p. 646.) This solution will be approximately decinormal, and it is best to leave it as it is after determining its exact iodine value, rather than to attempt to adjust it to exactly decinormal. Preserve in a stock bottle provided with a guard tube filled with soda lime. (d) StarcH SOLUTION.—Stir up 2 to 3 g of potato starch or 5 g of soluble starch with 100 cc of 1 per cent salicyclic acid solu- tion, add 300 to 400 ce. boiling water, and boil the mixture until the starch is practically dissolved, then dilute to 1 liter. (ec) Porassrum IopipE SoLUTION.—Dissolve 150 g of potassium iodide free from iodate in distilled water and dilute to 1,000 cc. (f) Hanus SoLurion.—Dissolve 13.2 g of iodine in 1,000 cc of 99.5 per cent glacial acetic acid, which will not reduce chromic acid. Add enough bromine to double the halogen content, determined by titration (3 cc of bromine is about the proper amount). The iodine may be dissolved by the aid of heat, but the solution should be cold when the bromine is added. (g) ALCOHOLIC SoprtumM HypRoxIDE SOLUTION.—Dissolve pure sodium hydroxide in 95 per cent ethyl alcohol in the proportion of about 22 g per 1,000 ce. Let stand in a stoppered bottle. Decant the clear liquid into another bottle and keep well stoppered. This solution should be colorless or only slightly yellow when used, and it will keep colorless longer if the alcohol is previously treated with sodium hydroxide (about 80 g to 1,000 cc), kept at about 50° C. for 15 days, and then distilled. WASHINGTON : GOVERNMENT PRINTING OFFICE: 1924 DEPARTMENT OF COMMERCE. BUREAU OF STANDARDS. S. W. STRATTON, Director. CIRCULAR OF THE BUREAU OF STANDARDS. No. 97. [3d edition. Issued July 3, 1922.] UNITED STATES GOVERNMENT SPECIFICATION FOR GREEN PAINT, SEMIPASTE AND READY MIXED. FEDERAL SPECIFICATIONS BOARD. STANDARD SPECIFICATION NO. 15. This Specification was officially adopted by the Federal Specifications Board on February 3, 1922, for the use of the Departments and Independent Establish- ments of the Government in the purchase of materials covered by it. CONTENTS. Page Sanpete Ae Aiea. EAE. Aidt’ BAA lies Dae. Thijs EAA ides I RI ty orn Sn 5 cin hp care dns how needs 400d be dean Myth. abieteg epee 3 Gomera amination of: semipastery, . i... Gyvieded-« Kin + coe 0 Me tials «ape 3 eee et a ee psp dene cram 0 ons va tp ee p Gn eee 6 gree eeeniory examination of mixed paint... ii... ses eee cee ee utes unas 8 ER eC es Ec ey see os his eT Oe EE TS cE SE Vale £0 5 eek Gee re) 1. GENERAL. The paint contemplated by this specification is a chrome green paint, and it may be ordered either in the form of semipaste pigment ground in linseed oil or as ready-mixed paint. The basis of purchase may be either net weight or volume (231 cubie inches to the gallon). (a) PicMENT.—The pigment in both semipaste and ready- mixed paints should be a chrome green containing about 23 per 109836°—22——1 2 Circular of the Bureau of Standards cent of color (sum of lead chromate and insoluble Prussian blue), about 10 per cent of magnesium silicate, aluminum silicate, or similar siliceous material, and about 67 per cent of barium sul- phate. It should be made by precipitating the color on the proper base rather than by mixing the individual materials. It must yield on analysis: oa Maximum.) Minimum, Per cent. | Per cent. Color (total lead chromate and insoluble Prussian blue)... ............e eee e ese efor eee eee eee Material soluble in water, including soluble Prussian blue...................... ie cries tan ees Acid-soluble or water-soluble calcium in any form, calculated as CaO........... ORE BH Bee Gcn pce oy he Material other than color and barium sulphate,................ cee eee cere eeees mike pL WROKE Ba apy sak eh The remainder must be barium sulphate. (b) Liguip.—The liquid in semipaste paint shall be entirely pure raw or refined linseed oil; in ready-mixed paint it shall contain not less than 90 per cent pure raw linseed oil, the balance to be combined drier and thinner. The thinner shall be turpen- tine, volatile mineral spirits, or a mixture thereof. (c) SemipastE.—Semipaste paint shall be made by thoroughly grinding the pigment with pure raw or refined linseed oil. The semipaste as received and three months thereafter shall be not caked in the container and shall break up readily in linseed oil to form a smooth paint of brushing consistency. It shall mix readily with linseed oil, turpentine, or volatile mineral spirits, or any combination of these substances, in all proportions, without curdling. The color and hiding power when specified shall be equal to that of a sample mutually agreed upon by buyer and seller. The weight per gallon shall be not less than 16 pounds. The paste shall consist of: Maximum.) Minimum. Per cent. | Percent. 72 68 Bad (550 l-) 0] ee nr Rn aOR GMRaE CEN sa eaMee Hr Wenge og CRM MORTEM UN ISIS yp Linseed ol os 08 bos cece ago obaleelbas Cutis Raa ea RN adoie RE. cea Vn ea ee 32 28 Moisture and.other volatile matters. <..060.. su oc bc osns0.0.0.0.0 0 00 cuen celcen sna avai Li ey J Are reer ae Coarse particles and ‘‘skins’”’ (total residue retained on No. 325 screen based on PIPMENL) FST Ab aie clon olvl ge sdawleltey Gin sMUstche cachet els coe Aa abe «nhs Wa a:cholele @ aia alitn eee SiS) tT. eens seo (d) Reapy-MixED Parnt.—Ready-mixed paint shall be well ground, shall not settle badly or cake in the container, shall be readily broken up with a paddle to a smooth uniform paint of good brushing consistency, and shall dry within 18 hours to a full oil gloss, without streaking, running, or sagging. ‘The color and hiding power when specified shall be equal to those of a sample Specification for Green Paint 3 mutually agreed upon by buyer and seller. The weight per gallon shall be not less than 12 pounds. ‘The paint shall consist of: Maximum.) Minimum. Percent. | Percent. | ee eae a RSS Oe Sele Ne TS SR iy Oe ene eS 55 Liquid (containing at least 90 per cent linseed oil)................................ 50 45 Be eaten eo eee EL. es ei ican oath ccs bile eae OSC Boldccde cea gt O28 |pake eto ee Coarse particles and “‘skins’’ (total residue retained on No. 325 screen based on eR Mr ee eae W HS es ae Gh a Cates. state lls eid ake wie ecd « kk las og held Dc e-s cn'p cena 2i52 | aad See NotTe.—Deliveries will, in general, be sampled and tested by the following methods, but the purchaser reserves the right to use any additional available information to ascertain whether the material meets the specification. 2. SAMPLING. It is mutually agreed by buyer and seller that a single package out of each lot of not more than 1000 packages shall be taken as representative of the whole. Whenever possible an original unopened container shall be sent to the laboratory, and when this is for any reason not done, the inspector shall determine by thorough testing with a paddle or spatula whether the material meets the requirement regarding caking in the container. He shall then thoroughly mix the contents of the container and draw a sample of not less than 5 pounds. This sample shall be placed in a clean, dry metal or glass container, which it must nearly fill. The con- tainer shall be closed with a tight cover, sealed, marked, and sent to the laboratory for test with the inspector’s report on caking. When requested, a duplicate sample may be taken from the same package and delivered to the seller, and the inspector may take a third sample to hold for test in case of dispute. 3. LABORATORY EXAMINATION OF SEMIPASTE. (a) CAKING IN CONTAINER. — When an original package is received in the laboratory it shall be weighed, opened, and stirred with a stiff spatula or paddle. The paste must be no more diffi- .cult to break up than a normal good grade of semipaste paint. The semipaste shall finally be thoroughly mixed, removed from the container, and the container wiped clean and weighed. ‘This weight subtracted from the weight of the original package gives the net weight of the contents. A portion of thoroughly mixed semipaste shall be placed in a clean container and the portions for the remaining tests promptly weighed out. (b) CoLlor.—Place some of the paint on a clean, clear glass plate. Place some of the standard agreed upon beside the sample on the plate, turn the glass over, and compare the colors. 4 Circular of the Bureau of Standards (c) WEIGHT PER GALLON.—From the weight of a known volume of the paste calculate the specific gravity, which multiplied by 8.33 gives the weight in pounds per gallon. Any suitable con- tainer of known volume may be used for the purpose, but a short cylinder of heavy glass with rounded bottom about 75 mm high and having a capacity of from 125 to 175 cc (a glass cap to keep dust from reagent bottle stopper) is a convenient apparatus for the purpose. ‘The capacity of this vessel is determined to within tcc. The paste is packed into it until completely full, the top leveled off smooth with a spatula, and weighed to +0.5 g. Sub- tract the weight of the empty container and divide the remainder by the number of cubic centimeters representing the capacity of the container. ‘he quotient is the specific gravity, which can be thus determined within +2 in the second decimal place. (d) Mixinc wirH LinsEED O1.—One hundred grams of the paste shall be placed in a cup, 30 cc of linseed oil added slowly with careful stirring and mixing with a spatula or paddle. ‘The result- ing mixture must be smooth and of good brushing consistency. (ec) MoIstURE AND OTHER VOLATILE MaTTEeR. — Weigh accu- rately from 3 to 5 g of the paste into a tared flat-bottomed dish about 5 cm in diameter, spreading the paste over the bottom. Heat at 105 to 110° C. for one hour, cool, and weigh. Calculate loss in weight as percentage of moisture and volatile matter. ({) PERCENTAGE OF PiGMENT.—Weigh accurately about 15 g of the paste into a weighed centrifuge tube. Add 20 to 30 cc of “extraction mixture’’ (see reagents), mix thoroughly with a glass rod, wash the rod with more of the extraction mixture, and add sufficient of the reagent to make a total of 60 cc in the tube. Place the tube in the container of a centrifuge, surround with water, and counterbalance the container of the opposite arm with a similar tube or a tube with water. Whirl at a moderate speed until well settled. Decant the clear supernatant liquid. Repeat the extraction twice with 40 cc of extraction mixture and once with 40 cc of ether. After drawing off the ether, set the tube in a beaker of water at about 80° C. or on top of a warm oven for 10 minutes, then in an oven at 110 to 115° C. for two hours. Cool, weigh, and calculate the percentage of pigment. Grind the pigment to a fine powder, pass through a No. 80 sereen to remove any skins, and preserve in a stoppered bottle. (g) PREPARATION OF Farry Acips.—To about 25 g of the paste in a porcelain casserole, add 15 cc of aqueous sodium Specification for Green Paint 5 hydroxide (see reagents) and 75 cc of ethyl alcohol, mix and heat uncovered on a steam bath until saponification is complete — (about one hour). Add 100 cc of water, boil, add an excess of sulphuric acid of specific gravity 1.2 (8 to 10 cc will usually suffice), boil, stir, and transfer to a separatory funnel to which some water has been previously added. Draw off as much as possible of the acid aqueous layer, wash once with water, then add 50 cc of water and 50 cc of ether. Shake very gently with a whirling motion to dissolve the fatty acids in the ether, but not so violently as to form anemulsion. Draw off the aqueous layer and wash the ether layer with one 15 cc portion of water and then with 5 cc portions of water until free from sulphuric acid. ‘Then draw off the water layer completely. Transfer the ether solution to a dry flask and add 25 to 50 g anhydrous sodium sulphate. Stopper the flask and let stand with occasional shaking at a temperature below 25° C. until the water is completely removed from the ether solution, which will be shown by the solution becoming perfectly clear above the solid sodium sulphate. Decant this clear solution, if necessary, through a dry filter paper, into a dry 100 cc Erlenmeyer flask. Pass a rapid current of dry air (pass through a CaCl, tower) into the mouth of the Erlenmeyer flask and heat to a temperature below 75° C. on a dry, hot plate until the ether is entirely driven off. 2 NoTtE.—It is important to follow all of the details, since ether generally contains alcohol and after washing with water always contains water. It is very difficult to remove water and alcohol by evaporation from fatty acids, but the washing of the ether solution and subsequent drying with anhydrous sodium sulphate removes both water and alcohol. Ether, in the absence of water and alcohol, is easily removed from fatty acids by gentle heat. The fatty acids prepared as above should be kept in a stoppered flask and examined at once. (h) TEST FOR MINERAL Ol, AND OTHER UNSAPONIFIABLE MATTER.—Place 10 drops of the fatty acids (g) in a 50 cc test tube, add 5 cc of alcoholic soda (see Reagents), boil vigorously for five minutes, add 40 cc of water, and ‘mix; a clear solution indicates that not more than traces of unsaponifiable matter are present. If the solution is not clear, the oil is not pure linseed oil. (2) lopINE NUMBER OF Farry Acips.—Place a small quantity of the fatty acids (g) in a small weighing burette or beaker. Weigh accurately. Transfer by dropping about 0.15 g (0.10 to 0.20 g) into a 500 cc bottle having a well-ground glass stopper, or an Erlenmeyer flask having a specially flanged neck for the iodine 109836°—22—2 6 Circular of the Bureau of Standards test. Reweigh the burette or beaker and determine amount of sample used. Add 10 ce of chloroform. Whirl the bottle to dissolve the sample. Add 10 cc of chloroform to two empty bot- tles like that used for the sample. Add to each bottle 25 ce of the Hanus solution (see reagents) and let stand with occasional shaking for one-half hour. Add 10 cc of the 15 per cent potas- sium iodide solution and 100 cc of water, and titrate with stand- ard sodium thiosulphate, using starch as indicator. ‘The titrations on the two blank tests should agree within 0.1 cc. From the difference between the’ average of the blank titrations and the titration on the sample and the iodine value of the thiosulphate solution, calculate the iodine number of the sample tested. (Io- dine number is centigrams of iodine to 1 g of sample.) If the iodine number is less than 170, the oil does not meet the specifica- tion. | (7) COARSE PARTICLES AND SkiNs.—Dry in an oven at 105 to 110° C. a No. 325 screen, cool, and weigh accurately. Weigh an amount of semipaste containing 10 g of pigment (see 3 (f)), add 50 ce of kerosene, mix thoroughly, and wash with kerosene through the screen, breaking up all lumps but not grinding. After washing with kerosene until all but the particles too coarse to pass the screen have been washed through, wash all kerosene from the screen with ether or petroleum ether, heat the screen for one hour at 105 to 110° C., cool, and weigh. 4. ANALYSIS OF PIGMENT. (a) QUALITATIVE ANALYsIS.—Test for Prussian blue by boiling a portion of the pigment with sodium hydroxide solution. A yellow or yellow-brown precipitate with a yellow liquid above it should result. Filter, add a mixture of ferric and fetrous salts to the filtrate, and render acid with dilute hydrochloric acid. A blue color indicates Prussian blue in the sample. Ignite another por- tion very gently to decompose the Prussian blue and make a qualitative analysis of the residue. (b) MatreR SoLUBLE IN WaATER.—Transfer 2.5 g of the pig- ment to a graduated 250 ce flask, add 100 ce of water, boil for 5 minutes, cool, fill to mark with water, mix, and allow to settle. Pour the supernatant liquid through a dry paper and discard the first 20 cc. “Then evaporate roo cc of the clear filtrate to dryness in a weighed dish, heat for one hour at 105 to 110° C., cool, and weigh. ae tee ie Specification for Green Patnt 7 (c) BARTUM SULPHATE AND SILICEOUS MATERIAL.—Heat a 1 ¢ portion of the pigment very gently in a small porcelain dish. The heat must be so regulated by moving the burner that the Prussian blue is thoroughly decomposed without rendering the iron difficultly soluble. Allow to cool, transfer to a 400 cc beaker, add 20 ce of concentrated hydrochloric acid, heat on steam bath for 30 minutes, boil for 5 minutes, dilute with hot water to about 250 cc, filter on paper while hot, wash thoroughly with hot water until the washings are free from lead and chlorine, and ignite and weigh the residue, which will be barium sulphate and siliceous material. Mix the ignited residue with about ro times its weight of anhydrous sodium carbonate (grinding the mixture in an agate mortar if necessary), and fuse the mixture in a covered platinum crucible, heating about one hour. Let cool, place crucible and cover in a 250 cc beaker, add about 100 cc of water, and heat until the melt is disintegrated. Filter on paper (leaving crucible and cover in beaker) and wash the beaker and filter thoroughly with hot water to remove soluble sulphates. Place the beaker containing the crucible and cover under the funnel, pierce the filter with a glass rod, and wash the carbonate residue into the beaker by means of a jet of hot water. Wash the paper with hot, dilute hydrochloric acid (1:1), and then with hot water. If the earbonate residue is not completely dissolved, add sufficient dilute hydrochloric acid to effect solution, and remove crucible and cover, washing them with a jet of water. Heat the solution to boiling and add 1o to 15 cc of dilute sulphuric acid, and continue the boiling for 10 or 15 minutes longer. Let the precipitate settle, filter on a weighed Gooch crucible, wash with hot water, ignite, cool, and weigh as BaSO,. Subtract from the result of the previous determination to obtain the siliceous material. (d) LEAD AND CHROMIUM.—Unite the filtrate and washings from barium sulphate and siliceous material (see (c)), dilute to 500 cc, nearly neutralize with ammonium hydroxide, and pass in a rapid stream of hydrogen sulphide until all the lead is pre- cipitated as Pb§; filter, wash with water containing a little hydro- gen sulphide, dissolve in hot nitric acid (1:3), and determine lead as sulphate in usual manner, weighing as PbSO,. Boil the fil- trate from the lead sulphide to expel hydrogen sulphide. Add sodium peroxide in sufficient amount to render the solution alka- line and to oxidize the chromium to chromate. Boil until the hydrogen peroxide is driven off, cool, acidify with sulphuric acid 8 Circular of the Bureau of Standards (1:4), add a measured excess of a freshly prepared solution of ferrous sulphate, and titrate the excess of ferrous iron with stand- ard potassium dichromate, using potassium ferricyanide solution as outside indicator. ‘Titrate a blank of an equal volume of the ferrous sulphate solution with the standard potassium dichromate. From the difference between the titration on the blank and on the sample, calculate the chromium in the sample to PbCrQ,. From the PbCrO, found, calculate the equivalent of PbSO, by multiplying by the factor 0.938. Subtract this value from the total PbSO, found above and report the remainder as lead com- pounds other than chromate, calculated as PbSQ,,. (ec) CaLcrum.—Ignite 2 g of the pigment and primaries the residue in hydrochloric acid as in 4(c). Then, without filtering from the insoluble matter, transfer to a 500 cc volumetric flask, saturate with hydrogen sulphide, make alkaline with ammonia, fill to the mark, mix, and filter through a dry paper, discarding the first 20 cc. ‘Then determine the calcium in 250 cc of the filtrate (corresponding to 1 g pigment) by precipitation as oxalate and weighing as calcium oxide. (f) Cotor.—Add the percentages of matter soluble in water 4(b), barium sulphate and siliceous material 4(c), lead compounds other than chromate calculated as PbSO, 4(d), and calcium oxide 4(e) and subtract the sum from 100, Call the difference the percentage of color. 5. LABORATORY EXAMINATION OF MIXED PAINT. (a) CAKING IN CONTAINER.—Follow the procedure outlined in 3(a), noting that the paint should be no more difficult to break up than a good grade of mixed paint. (b) CoLor.—Follow the procedure outlined in 3(0). (c) WEIGHT PER GALLON.—Weigh a clean, dry, 100 cc gradu- ated flask. Fill to the mark with the thoroughly mixed paint and weigh again. ‘The increase in weight expressed in grams, divided by 100, gives the specific gravity, which multiplied by 8.33 gives the weight in pounds per gallon. (d) BRUSHING PROPERTIES AND TIME OF DRYING. —Brush the well-mixed paint on a suitable panel, which may be ground glass, steel, or well-filled wood. Note whether the paint works satis- factorily under the brush. Place the panel in a vertical position in a well-ventilated room and let stand for 18 hours. The paint should be dry and free from streaks. Specification for Green Paint 9 (ec) WATER.—Mix 100 g of the paint in a 300 ce flask with 75 cc of toluol. Connect with a condenser and distill until about 50 cc of distillate has been collected in a graduate. ‘The temperature in the flask should be then about 105° to 110°C. The number of cubic centimeters of water collecting under the toluol in the re- ceiver is the percentage of water in the paint. ({) VOLATILE THINNER.—Follow the procedure outlined in 3(e). Correct the result for any water found (see 5(e)) and report the remainder as volatile thinner. (g) PERCENTAGE OF PiGMENT.—Follow the procedure outlined in 3(/). (h) TESTING NONVOLATILE VEHICLE.—Follow the procedure outlined in 3(9), 3(2), and 3(z), except that in the preparation of the fatty acids the mixture of paint and alkali is heated on the steam bath until all volatile thinner is driven off. (2) COARSE PaRTICLES AND Skins.—Follow the procedure out- lined in 3(,). | (j) TEsTING PicmMENT.—Follow the procedure outlined in 4(a) to 4(e), inclusive. 6. REAGENTS. (a) EXTRACTION MIxTURE.— 5 volumes benzol. 4 volumes methyl alcohol 1 volume acetone. (6) AQuEOUS Sopium HypRoxIpE.—Dissolve 100 g of sodium hydroxide in distilled water and dilute to 300 cc. (c) STANDARD SODIUM THIOSULPHATE SOLUTION.—Dissolve pure sodium thiosulphate in distilled water (that has been well boiled to free it from carbon dioxide) in the proportion of 24.83. g crys- tallized sodium thiosulphate to 1,000 cc of the solution. It is best to let this solution stand for about two weeks before stan- dardizing. Standardize with pure resublimed iodine. (See Tread- well-Hall, Analytical Chemistry, vol. 2, 3d ed., p. 646.) This so- lution will be approximately decinormal, and it is best to leave it as it is after determining its exact iodine value, rather than to attempt to adjust it to exactly decinormal. Preserve in a stock bottle provided with a guard tube filled with soda lime. (dq) STaRcH SOLUTION.—Stir up to 2 to 3 g of potato starch or 5 g of soluble starch with 100 cc of 1 per cent salicylic acid solu- IO Circular of the Bureau of Standards tion, add 300 to 400 ce boiling water, and boil the mixture until the starch is practically dissolved, then dilute to 1 liter. (ec) Porassrtum IopIDE SoLutTIoN.—Dissolve 150 g of potassium iodide free from iodate in distilled water and dilute to 1,000 cc. (f) Hanus SoLution.—Dissolve 13.2 g of iodine in 1,000 cc of 99.5 per cent glacial acetic acid, which will not reduce chromic acid. Add enough bromine to double the halogen content, deter- mined by titration (3 cc of bromine is about the proper amount). The iodine may be dissolved by the aid of heat, but the solution should be cold when the bromine is added. (g) ALcoHOLIC SoprumM HypROxIDE SOLUTION.—Dissolve pure sodium hydroxide in 95 per cent ethyl alcohol in the proportion of about 22 g per 1,000cc. Let stand in a stoppered bottle. Decant the clear liquid into another bottle and keep well stop- pered. This solution should be colorless or only slightly yellow when used, and it will keep colorless longer if the alcohol is pre- viously treated with sodium hydroxide (about 80 g to 1,000 cc), kept at about 50° C. for 15 days, and then distilled. (h) STANDARD FERROUS SULPHATE SOLUTION.—Dissolve 14 g of pure crystallized ferrous sulphate (FeSO, 7H,O) in about 500 cc of water, to which 25 cc of concentrated H,SO, has been added, and then dilute to 1,000 cc. This solution should be freshly standardized when needed, as it does not keep well. (1) STANDARD POTASSIUM DICHROMATE SOLUTION.—Dissolve 4.903 g of pure dry crystallized potassium dichromate in water and dilute to 1,000 cc. One cubic centimeter of this solution corresponds to 0.0108 g PbCrO,, or o.oror g PbSO,. (j) PoTasstuM FERRICYANIDE SOLUTION.—Dissolve a piece half as big as a small pea in 50 cc of water. This solution must be made fresh when wanted, because it does not keep. ‘Samaaaspinouepupaapinsae-nadagemaaaapaaaoiae neaeeegineueondamaesoee pane aera nena neen eee eee ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. AT 5 CENTS PER COPY V WASHINGTON : GOVERNMENT PRINTING OFFICE : 1922 “ DEPARTMENT OF COMMERCE. BUREAU OF STANDARDS. CIRCULAR OF THE BUREAU OF STANDARDS. No. 98. [Second edition. Issued February 28, 1923.] UNITED STATES GOVERNMENT SPECIFICATION FOR VOLATILE MINERAL SPIRITS FOR THINNING PAINTS.! SnEEnEEiEeiieeaet FEDERAL SPECIFICATIONS BOARD. STANDARD SPECIFICATION No. 16. [Revised January 2, 1923.j This specification was officially adopted by the Federal Specifications Board on February 3, 1922, for the use of the departments and independent establish- ments of the Government in the purchase of volatile mineral spirits for thin- ning paints. CONTENTS. Page. oS co Boi it ie di eet Allain Sap ‘Saad. Bre nara aoa doll Ai tiaities ysy I a. Detection and removal of separated water.i).. 0.6.0.0. 0 cece ccc 2 te da ile, 29s. <> sak ee eek: -Liaaters «dry dpbeterehs die. db ae 2 Uae MR ITIACION 6 oa se. ge oss ates o 8 Sie Wonk Lat ale ese Bock Cee 3 Si og Uh cae ey pane ee a aE Ne rae Waray Mae Bac Pen’ © ART ania A Fo 9 1. GENERAL. This specification applies only to petroleum distillates, known as mineral spirits. The material delivered under this specifica- tion shall conform to the following requirements: APPEARANCE.— hall be clear and free from suspended matter and water. CoLor.—Shall be no darker than an aqueous solution of potas- sium dichromate containing 0.0048 g per liter (this corresponds to No. 21 Saybolt chromometer). Spot TEst.—Shall evaporate completely from filter paper. Petroleum Products, Bureau of Mines Technical Paper 323. 27818°—23 ‘ 2 Circular of the Bureau of Standards. FLasH Pornt.—Shall be not lower than 30° C. (86° F.) when tested in a closed cup tester. BLACKENING.—Shall not blacken clean metallic copper. Distil- late below 130° C. (266° F.) shall not exceed 5 percent. Distillate below 230° C. (446° F.) shall be not less than 97 per cent. Acipity.—shall be neutral. 2. DETECTION AND REMOVAL OF SEPARATED WATER. Draw a portion by means of a glass or metal container with a removable stopper or top, or with a ‘‘thief,’’ from the lowest part of the container, or by opening the bottom valve of the perfectly level tank car. If water is found to be present, draw it all out, record the quantity, and deduct it from the total volume of liquid delivered. NorTrE.—Deliveries will in general be sampled and tested by the following methods, but the purchaser reserves the right to use any additional available information to ascertain whether the material meets the specification. 3. SAMPLING. The method of sampling given under (a) should be used when- ever feasible. When method (a) is not applicable, method (0), (c), or (d) is to be used, according to the special conditions that obtain. , (2) WuiILe LoapInc TANK Car OR WHILE FILLING CONTAINERS FOR SHIPMENT.—Samples shall be drawn by the purchaser’s imspector at the discharge pipe where it enters the receiving vessel or vessels. The composite sample shall be not less than 5 gallons and shall consist of small portions of not more than 1 quart each taken at regular intervals during the entire period of loading or filling. The composite sample thus obtained shall be thoroughly mixed, and from it three samples of not less than 1 quart each shall be placed in clean, dry glass bottles or tin cans, which must be nearly filled with the sample and securely stoppered with new clean corks or well-fitting covers or caps. These shall be sealed and distinctly labeled by the inspector. One shall be delivered to the buyer, one to the seller, and the third held for check in case of dispute. (6) From LoapEp TANK CAR OR OTHER LARGE VESSEL.—The composite sample taken shall be not less than 5 gallons and shall consist of numerous small samples of not more than 1 quart each taken from the top, bottom, and intermediate points by means of a metal or glass container with removable stopper or top. — Specification for Mineral Spirtts. 3 This device attached to a suitable pole is lowered to the various desired depths, when the stopper or top is removed and the con- tainer allowed to fill. The sample thus obtained is handled as in (a). : (c) BARRELS AND Drums.—Barrels and drums shall be sampled after gauging contents. Five per cent of the packages in any shipment or delivery shall be represented in the sample. Thor- oughly mix the contents of each barrel to be sampled by stirring with a clean rod and withdraw a portion from about the center by means of a “thief” or other sampling device. The com- posite sample thus obtained shall be not less than 3 quarts, shall consist of equal portions of not less than one-half pint from each package sampled, and shall be handled as in (a). Should the inspector suspect adulteration, he shall draw the samples from the suspected packages. (d) SMALL CONTAINERS, CANS, ETC., OF 10 GALLONS OR LESS.— These should be sampled, while filling, by method (a) whenever possible; but in case this is impossible, the composite sample taken shall be not less than 3 quarts. This shall be drawn from at least five packages (from all when fewer), and in no case from less than 2 per cent of the packages. The composite sample thus taken shall be thoroughly mixed and subdivided as in (a). é. 4. LABORATORY EXAMINATION. (a) APPEARANCE.—Exaimine to determine compliance with the specification. (6) CoLor.—Compare in any suitable apparatus the depth of color of the sample with the depth of color of a fresh solution of potassium dichromate in distilled water containing 0.0048 g K,Cr,0, per liter. (If desired, the color may be determined in a Saybolt chromometer, in which case the color must be no darker than No. 21 on that scale.) (c) Spor TEest.—Transfer five drops of the mineral spirits by means of a small pipette or burette to the center of a clean white filter paper supported on a 7-cm crystallizing dish and allow the liquid to evaporate at room temperature, away from direct sun- light. There should be no oily spot left after 30 minutes. (qd) FLAsH Point.—Determine with either the ‘‘Tag”’ or Elliott closed-cup tester. The former is preferred.’ 2 Directions for using the ‘‘Tag”’ tester may be found in A. S. T. M. Standards Ds6-21 and in Bureau of Mines Technical Paper No. 323. Directionsfor using the Elliott cup may be found in Proceedings A.S. T. M., 1917, pt. 1, p. 414. 4 Circular of the Bureau of Standards. (ec) BLACKENING.—Place a clean strip of mechanically polished pure sheet copper, about }4 inch wide and 3 inches long (1.3 cm by 7.5 cm) in a glass test tube about 34 inch wide and 18 inches long (1.9 by 46 cm). Add sufficient of the sample to be tested to completely cover the strip and heat rapidly to its boiling point (it is most convenient to heat the tube by immersion in an oil bath maintained at a temperature slightly higher than the initial boiling point of the mineral spirits). Keep the sample at its boiling point, without any actual distillation taking place, for 30 minutes and then examine the copper strip for blackening. A slight tarnish shall be disregarded, but any marked blackening shall be cause for rejection. | (f) DistILLATION.—Use the A. S. T. M. (D 86-21 T) method as described below, except that it will be necessary to read the volume of the distillate at 130° C. and at 230° C. and the distilla- tion need not be carried beyond the 230° C. (446° F.) point. APPARATUS. Flask.—The standard 100 cc Engler flask is shown in Figure 1, the dimensions and allowable tolerance being as follows: Dimensions of Engler flask. . @f- Description. he wpe 4 . Inches. ei Diancter of bulb; outside <9 see evo had ane Pee ck cals rie 6.5 2. 56 0.2 Diameter of neck, insides... 2e. op oh i oie ae Sk me he oe Bal ee een cee al 1.6 - 63 el Lenvth of meek ke castes ss poe becca sees coe Geert es re cee eee 15.0 5.91 4 Length of vapor tab@y 20) os jccols wire ds ue o bcs maf pts Sone elas oe oie ee aS ee 10. 0 3.94 .3 Diameter of vapor fube, outside. sco aac te est se pes nee -6 24 .05 Diameter of vapor tuhe, inside. . 5..5....509 sche ks 09a gd cn ecm aoe ale : ZANG OLIGE:= | occ. aw oes Lice vos AE Oe RO ES Books « Sebpe 57 Peewee ne eau a ace er ie TOFS Mees Tinting and extending pigments. ............... ccc c cece eee ee eee e eee eee e ne eeares aS i eaerre: oy! Material BBL Die Ate WALCO cos, ow inc dc ial ethce meolass'9 as ibaa os aaeuachis «4, win» ale cetera * ADB abs ere eeaen N OTE. —The lithopone used must contain not less than 26 per cent of zinc sulphide and must not darken on exposure. (6) Liguip.—The liquid ee of the paint shall consis of treated drying oils or varnish, or a mixture thereof, and turpentine or volatile mineral spirits, or a mixture thereof, in such proportions as to insure not less than 25 per cent of nonvolatile vehicle. The nonvolatile vehicle shall dry to a tough and elastic film. (c) Parnt.—The paint shall be well ground, shall not settle badly, cake, or thicken in the container, shall be readily broken up with a paddle to a smooth, uniform paint of brushing con- sistency, and shall dry within 18 hours to a dead flat finish without streaking, running, or sagging and free from laps and brush marks. ‘The color and hiding power when specified shall be equal to those of a sample mutually agreed upon by buyer and seller. After drying for not less than five days, marks made on the painted surface with a soft lead pencil (No. 2 Mogul) shall be easily removed by washing with soap and warm water without appreciably marring the paint surface. The weight per gallon shall be not less than 14% pounds. The paint shall consist of: _ | Maximum, Minimum. Per cent. | Per cent. 7 68 tee Sy AECL SE EET Creer ee se 2 Liquid ocaninisa at least 25 per cent nonvolatile matter)...................c.-00: 4 28 Contes particles and “skins” (total residue retained on No. 325 screen basedon| §8 | — plgrizent) ie... «a un debinho cdailte pike gains Hsp es keane) dima RE ee) sere NotE.—Deliveries will, in general, be sampled and tested by the following methods, but the purchaser reserves the right to use any additional available information to ascertain whether the material meets the specification. 2. SAMPLING. It is mutually agreed by buyer and seller that a single package ‘out of each lot of not more than 1,000 packages shall be taken as representative of the whole. Whenever possible, an ‘original unopened container shall be sent to the laboratory, and when this is for any reason not done the inspector shall determine by thor- Specification for Flat Interior Lithopone Paint 3 \ ough testing with a paddle or spatula whether the material meets the requirement regarding caking in the container. He shall then thoroughly mix the contents of the container and draw a sample of not less than 5 pounds. This sample shall be placed in a clean, dry metal or glass container, which it must nearly fill. The container shall be closed with a tight cover, sealed, marked, and sent to the laboratory for test with the inspector’s report on caking. When requested, a duplicate sample may be taken from the same package and delivered to the seller, and the inspector may take a third sample to hold for test in case of dispute. 3. LABORATORY EXAMINATION. (a) .CAKING IN CONTAINER.—When an original package is re- ceived in the laboratory it shall be weighed, opened, and stirred with a stiff spatula or paddle. ‘The paint must be no more difficult to mix to a uniform consistency than a good grade of flat paint. The paint shall finally be thoroughly mixed, removed from the con- tainer, and the container wiped clean and weighed. This weight subtracted from the weight of the original package gives the net weight of the contents. A portion of the thoroughly mixed paint shall be placed in a clean container and portions for the remaining tests promptly weighed out. (6) Cotor.—Place some of the paint on a clean, clear glass plate. Place some of the standard agreed upon beside the sample on the plate, turn the glass over, and compare the colors. (c) WEIGHT PER GALLON.—Weigh a clean, dry, 100 ce gradu- ated flask. Fill to the mark with the thoroughly mixed paint and weigh again. ‘The increase in weight expressed in grams, divided by 100, gives the specific gravity, which multiplied by 8.33 gives the weight in pounds per gallon. (2) BRUSHING PROPERTIES, TIME OF DRYING, AND RESISTANCE T0 WasHING.—Brush the well-mixed paint on a suitable panel, which may be ground glass, steel, or well-filled wood. Note whether the paint works satisfactorily under the brush. Place the panel in a vertical position in a well-ventilated room and let it stand for 18 hours. The paint should be dry and free from streaks. Let the panel stand for five days, then make marks on it with a soft lead pencil (No. 2, Mogul) and wash these marks off with warm (75° C.) distilled water and white floating soap, using a sponge or soft rag. The marks must be removed by this treatment without appreciably marring the paint film. 4 Circular of the Bureau of Standards (e) FastNEss To Licur.—Apply a sufficient number of coats of the paint to a ground-glass plate to completely hide the surface, cover half of this painted surface with opaque black paper, and exposure indoors in a well-lighted room for five days. Remove the black paper and examine the surface. The exposed portion should be no darker than the portion protected by the black paper. ({) WaTER.—Mix 100 g of the paint in a 300 cc flask with 75 ce of toluol. Connect with a condenser and distil until about 50 ce of distillate has been collected in a graduate. The tem- perature in the flask should be then about 105 to 110° C. The number of cubic centimeters of water collecting under the toluol in the receiver is the percentage of water in the paint. Material | complying with the specification should yield less than 1.0 cc. (g) VOLATILE THINNER.—Weigh accurately from 3 to 5 g of the paint into a tared flat-bottomed dish about 5 cm in diameter, spreading the paint over the bottom. Heat at 105 to 110° C. for one hour, cool, and weigh. Calculate the loss in weight as per- centage of water and volatile thinner, subtract from this the per- centage of water (3 (f)), and report the remainder as volatile thinner. _ (h) PERCENTAGE OF PIGMENT.—Weigh accurately about 15 g of the paint into a weighed centrifuge tube. Add 20 to 30 cc of “extraction mixture’’ (see Reagents), mix thoroughly with a glass rod, wash the rod with more of the extraction mixture, and add sufficient of the reagent to make a total of 60 cc in the tube, Place the tube in the container of a centrifuge, surround with water, and counterbalance the container of the opposite arm with a similar tube or a tube with water. Whirl at a moderate speed until well settled. Decant the clear supernatant liquid. Repeat the extraction twice with 40 ce of extraction mixture and once with 4o cc of ether.- After drawing off the ether, set the tube in a beaker of water at about 80° C. or on top of a warm ~. oven for 10 minutes, then in an oven at 110 to 115° C. for two hours. Cool, weigh, and calculate the percentage of pigment. Grind the pigment to a fine powder, pass through a No. 80 screen to remove any skins, and preserve in a stoppered bottle. Pre- serve the extracted vehicle for 3 (7). (2) PERCENTAGE OF NONVOLATILE VEHICLE.—Add together the percentages of water (3 (f)), of volatile thinner (3 (g)), and of pig- ment (3 (h)), and subtract the sum from 100. ‘The remainder is the percentage of nonvolatile vehicle, which should be not less than one-third as large as the percentage of volatile thinner. Specification for Flat Interror Lithopone Paint 5 (j) NaTuRE oF NONVOLATILE VEHICLE.—Evaporate the ex- tracted vehicle and extraction mixture from 3 (h) to about 5 cc Thoroughly clean with benzol a piece of bright sheet iron, tin plate, or terneplate. Spread a portion of the concentrated ex- tracted vehicle on the sheet of metal, allow to dry for 30 minutes at room temperature in a vertical position, bake for three hours . at 100 to 110° C. (212 to 221° F.), remove from the oven, and keep at room temperature for three days. Test the film with a knife blade at a place not less than 2.5 cm (1 inch) from the edge. The film should be tough and elastic; if it powders or if particles fly under the test, it will be considered brittle, which will be cause for rejection. The film must also stand light, vigorous rubbing with the finger without powdering or disintegrating. (k) COARSE PARTICLES AND SKINS.—Dry in an oven at 105 to 110° C. a No. 325 screen, cool, and weigh accurately. Weigh an amount of paint containing 10 g of pigment (see 3 (h)), add 50 cc of kerosene, mix thoroughly, and wash with kerosene through the screen, breaking up all lumps, but not grinding. After washing with kerosene until all but the particles too coarse to pass the screen have been washed through, wash all kerosene from the screen with ether or petroleum ether, heat the screen fm one hour at 105 to 110° C., cool, and weigh. 4. ANALYSIS OF PIGMENT. Use the pigment extracted in 3 (h). (a) QUALITATIVE ANALYsIs.—Make qualitative sel Si fol- lowing ordinary methods. (6) MATTER SOLUBLE IN WATER. ashipe nice 2.5 g of the pig- ment to a graduated 250 cc flask, add 100 ce of water, boil for five minutes, cool, fill to mark with water, mix, and allow to settle. Pour the supernatant liquid through a dry filter paper and discard the first 20 cc. Then evaporate 100 cc of the clear filtrate to dryness ina weighed dish, heat for one hour at 105 to 110° C., cool, and weigh. ‘The residue should not exceed 0.008 g. (c) BaRIuM SULPHATE AND SILICEOUS’ MaTERIAL.—Transfer 1 g of pigment to a porcelain casserole or dish, moisten with a few drops of alcohol, add 40 cc of hydrochloric acid (1.1, specific gravity), cover, and boil to expel hydrogen sulphide; remove the cover and evaporate to dryness on the steam bath, moisten with hydrochloric acid, dilute with water, filter through paper, and wash with dilute hydrochloric acid and then with hot water until 6 Circular of the Bureau of Standards the washings are free from zinc and chlorine. Ignite and weigh the residue, which will be barium sulphate and siliceous material. Mix the ignited residue with about 10 times its weight of anhy- drous sodium carbonate (grind the mixture in an agate mortar if necessary), fuse the mixture in a covered platinum crucible, heat- ing about one hour. Let cool, place the crucible and cover in a 250 cc beaker, add about 100 cc of water, and heat until the melt is disintegrated. Filter on paper (leaving the crucible and cover in the beaker) and wash the beaker and filter thoroughly with hot water to remove soluble sulphates. Place the beaker containing the crucible and cover under the funnel, pierce the — filter with a glass rod, and wash the carbonate residue into the beaker by means of a jet of hot water. Wash the paper with hot dilute hydrochloric acid (1:1), and then with hot water. If the carbonate residue is not completely dissolved, add sufficient dilute hydrochloric acid to effect solution, and remove the crucible » and cover, washing them with a jet of water. Heat the solution to boiling and add 1o to 15 cc of dilute sulphuric acid, and continue the boiling for 10 or 15 minutes longer. Let the pre- cipitate settle, filter on a weighed Gooch crucible, wash with hot water, ignite, cool, and weigh as BaSO,. Subtract from the re- sult of the previous determination to obtain the siliceous material. (d) Tota, Zinc CALCULATED As Zinc OximpE.—With material containing no interfering elements (iron, for example) weigh ac- curately about 1 g of pigment, transfer to a 400 cc beaker, moisten with alcohol, add 30 ce of hydrochloric acid (1:2), boil for two to three minutes, add 200 cc of water and a small piece of litmus paper; add strong ammonia until slightly alka- line, render just acid with hydrochloric acid, then add 3 ce of strong hydrochloric aeid, heat nearly to boiling, and titrate with standard ferrocyanide as in standardizing that solution (see Reagents). Calculate total zine as zinc oxide. When iron or other interfering elements are present (see 4 (a) ), take the filtrate containing the zinc from 4 (c), add a slight excess of bromine water and 2 g ammonium chloride, heat to nearly boiling, add an excess of ammonia, heat for about two minutes, filter, dissolve the precipitate in hydrochloric acid, add 2 g of ammonium chloride, and reprecipitate with ammonia as above. Filter, wash the precipitate with hot 2 per cent ammonium-chloride solution, unite the two filtrates, and determine zinc as above. 1 Specification for Flat Interior Lithopone Paint 7 (e) Zinc Oxipe.—Weigh accurately 2.5 g¢ of pigment, transfer to a 250 cc graduated flask, moisten with a few drops of alcohol, add about 200 ce of 1 to 3 per cent acetic acid, shake vigorously and let stand for 30 minutes, shaking once every five minutes. Fill to the mark with 1 to 3 per cent acetic acid, mix, filter through a dry paper, discard the first 25 cc and determine zine in 100 cc of the filtrate (corresponding to 1 g) as in 4 (d). Calculate the _ percentage of zinc oxide. (f) CaLcuLations.—Subtract the percentage of zinc oxide (4 (e) ) from the percentage of total zinc as zinc oxide (4 (d) ) and multiply the remainder by 1.2 to convert to percentage of zinc sulphide. In case the percentage of barium sulphate (4 (c)) iis not more than 2.86 times as great as the percentage of zinc sul- phide, add the two together and call the sum the percentage of lithopone. If the percentage of barium sulphate is greater than this amount, take 2.86 times the percentage of zinc sulphide as the percentage of barium sulphate to be included in the percentage of lithopone and include the remainder in the percentage of tinting and extending pigments. Subtract, the sum of the percentage of zine oxide (4 (e) ), lithopone, and matter soluble in water (4 (0) ) from 100. Call the remainder percentage of tinting and extending pigments. 5. REAGENTS. (a) Extracrion MixtuRE.— 3 10 volumes ether (ethyl ether). 6 volumes benzol. . 4 volumes methyl alcohol. I volume acetone. (6) ONE To THREE PER Cen? Acetic “Acip.—Dilute 20 cc glacial acetic acid to 1,000 cc with distilled water. (c) Uranyt InpicaTor For Zinc TirraTIon.—A 5 per cent solution of uranyl nitrate in water or a 5 per cent solution of uranyl acetate in water made slightly acid with acetic acid. (dq) StanDaRD Potasstum FERROCYANIDE.—Dissolve 22 g. of the pure salt in water and dilute to 1,000 cc. To standardize, transfer about 0.2 g (accurately weighed) of pure metallic zinc or freshly ignited pure zinc oxide to a 400 cc beaker. Dissolve in 10 cc of hydrochloric acid and 20 cc of water. Drop in a small piece of litmus paper, add ammonium hydroxide until slightly alkaline, then add hydrochloric acid until just acid, and then 3 cc. 8 Circular of the Bureau of Standards of strong hydrochloric acid. Dilute to about 250 ce with hot’ water and heat nearly to boiling. Run in the ferrocyanide solu- tion slowly from a burette with constant stirring until a drop tested on a white porcelain plate with a drop of the uranyl indi-_ cator shows a brown tinge after standing one minute. A blank should be run with the same amounts of reagents and water as in the standardization. The amount of ferrocyanide solution re- quired for the blank should be subtracted from the amounts used in standardization and in titration of the sample. The standardi- zation must be made under the same conditions of temperature, volume, and acidity as obtain when the sample is titrated. SA SSSR TSS LS SAE TSI ASST AEST SNC Soa | ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D, C. AT 5 CENTS PER COPY Vv DEPARTMENT OF COMMERCE. BUREAU OF STANDARDS. S. W. STRATTON, Director. CIRCULAR OF THE BUREAU OF STANDARDS. No. 117. [2d edition. Issued July 3, 1922.] UNITED STATES GOVERNMENT SPECIFICATION FOR | INTERIOR VARNISH. FEDERAL SPECIFICATIONS BOARD. STANDARD SPECIFICATION No, 22. This Boeifcation was officially adopted by the Federal Specifications Board on February 3, 1922, for the use of the Departments and Independent Establish- ments of the Government in the purchase of materials covered by it. CONTENTS. ; Page EE Pe Sie eT ONT TES RN: UR. RE ERS 20 ee I ROC ete. SS, ise, oN Tf) SRO UCR Ra 2 ee ener eMarmindtion (iy)... fa ls2iitce . nubs they olay ua. paadeeers 2 SE a a as! abcess OP gic OP. cn tes tbo ie 6 1. GENERAL. The varnish shall be suitable for general interior use, including both rubbed and unrubbed finish, exclusive of floors. It must be capable of easy application with a brush in the ordinary manner according to the rules of good standard practice, must flow out to a good level coat free from runs, sags, pits, or other defects, and dry with reasonable promptness to a hard, somewhat elastic glossy coating which can be rubbed in 48 hours or less. ‘The manufac- _ turer is given wide latitude in the selection of raw materials and processes of manufacture, so that he may produce a varnish of the highest quality. The varnish must meet the following requirements: APPEARANCE. 63901 °—23 Clear and transparent. 2 Circular of the Bureau of Standards e CoLor.—Not darker than a solution of 3 g of potassium dichro- | mate in 100 ce of pure sulphuric acid, specific gravity 1.84. FLasu Pornt (cLosED-cup).—Not below 30° C. (85° F.). NoNnvVOLATILE MatTER.—Not less than 45 per cent by weight. Set to Toucu.—In not more than 4 hours. Dry Harp.—In not more than 24 hours. Dry to Rus.—In not more than 48 hours. TOUGHNESS.—Film on metal must stand rapid bending over a rod 3 mm (% inch) in diameter. Worxkinc PRopERTIES.—Must have good brushing, flowing, covering, leveling, and rubbing properties; and must show no impairment of luster or other defect when used where natural or illuminating gases aré burned or when subjected to air currents during the process of drying or application. Water RESISTANCE.—The dried film must stand application of cold water for not less than 18 hours without whitening or showing other visible defect. Note.—Deliveries will, in general, be sampled and tested, by the following methods, but the pur- chaser reserves the right to use any available information to ascertain whether the material meets the specification. 2. SAMPLING. It is mutually agreed by buyer and seller that a single package out of each lot of not more than 1,000 packages shall be taken as representative of the whole. Whenever possible, an original un- opened container shall be sent to the laboratory, and when for any reason this is not done, the inspector shall thoroughly mix the contents of the container sampled, transfer not less than 1 quart to a clean dry glass bottle or tin can which must be nearly filled with the sample, securely stoppered with a new clean cork or well-fitting cover, or cap, sealed, and distinctly labeled by the inspector. The inspector should take a duplicate from the container sampled to be held for check in case of dispute, and, when re- quested, should take a sample for the seller. 3. LABORATORY EXAMINATION. The tin panels used in the following tests shall be cut from — bright tin plate weighing not more than 25 g nor less than 19 g per square decimeter (0.51 to 0.39 pound per square foot). (Commercial No. 31 gage bright tin plate should weigh about 0.44 pound per square foot. It is important that the tin plate used shall be within the limits set.) | | Specification for Intertor Varmsh 3 (a) APPEARANCE.—Pour some of the thoroughly mixed sam- ple into a clear glass bottle or test tube and examine by trans- mitted light. The varnish must be clear and transparent. (b) CoLor.—Prepare a standard color solution by dissolving 3 g of pure powdered potassium dichromate in 100 cc of pure concentrated sulphuric acid of specific gravity 1.84. Gentle. heat may be used if necessary to perfect the solution of the di- chromate. The standard color solution and a sample of the varnish to be tested shall be placed in clear, thin-walled glass tubes of the same diameter. The color comparison shall be made by placing the tubes close together and looking through them by transmitted light. The tubes used for this test should be 1.5 to 2.0 cm (5% to 18 inch) in diameter and shall be filled to a depth of at least 2.5 cm (1 inch). (Since the potassium di- chromate-sulphuric acid must be freshly made for this color comparison, it is frequently more convenient to compare samples with a permanently sealed tube of varnish which has previously been found to be slightly lighter in color than the standard solu- tion of 3 g dichromate in sulphuric acid. When samples are found to be darker than this standard tube of varnish, the di- chromate standard should be made up for final decision.) | (c) FLasH Pornt.—Determine with either the Tag or Elliott closed-cup tester. The former is preferred.’ (d) NonvVOLATILE MaTrer.—Place a portion of the sample in a stoppered bottle or weighing pipette. Weigh container and sam- ple. ‘Transfer about 1.5 g of the sample to a weighed flat-bot- tomed metal dish about 8 cm diameter (a friction-top can plug). Weigh container again and by difference calculate the exact weight of the portion of sample transferred to the weighed dish. Heat _ dish and contents in an oven maintained at 105 to 110° C. (221 to 230° F.) for three hours. Cooland weigh. From the weight of the residue left in the dish and weight of the sample taken, calculate the percentage of nonvolatile residue. (ec) Dryinc TimE.—Pour the varnish on a clean glass or bright tin plate not less than 15 cm (6 inches) long and 1ocm (4 inches) wide. Place the plate in a nearly vertical position in a well- ventilated room but not in the direct rays of the sun. The tempera- ture of the room should be from 21 to 32°C. (7o to 90° F.). The film is tested at points not less than 2.5 cm (1 inch) from the edges of the film by touching lightly with the finger. The varnish is 1 Directions for using the Tag tester may be found in A. S. T. M. Standards D 56-21, and directions for using the Elliott cup in Proceedings A. S. T. M., 1917, pt. 1, D. 414. 4 . Crrcular of the Bureau of Standards. from carbon dioxide and other acid fumes. Wash the residue on the paper or in the crucible with hot neutral alcohol until free from soap. Dry the filter paper or crucible and residue at 100 to 105°C. for three hours, cool, and weigh the total matter insoluble in alco-. hol. (Since the percentage of the matter insoluble in alcohol is not required under this specification, time may be saved by omitting the drying and weighing and proceeding directly with the moist residue to the determination of matter insoluble in water (ae (2) FREE ALKALI oR Free Actp.—Titrate the filtrate from the above, using phenolphthalein as indicator, with standard acid or alkali solution, and calculate the alkalinity to sodium hydroxide (or potassium hydroxide) or acidity to oelic acid. | (3) Matrer INSOLUBLE IN WatTER.—Proceed as in the deter- mination of matter insoluble in alcohol. After filtering and thoroughly washing the residue, extract it with water at 60° C. and wash the filter thoroughly. (When the matter insoluble in water is all inorganic, boiling water may be used for the extraction and washing.) Dry the filter and residue at 100 to 105° C. for , three hours, cool, and weigh matter insoluble in water. The nature of this may be determined by further examination. ‘The insoluble matter should be siliceous. ‘The approximate amount of feldspar contained in the abrasive material of scouring soap (when such material is known to contain nothing but feldspar or quartz or a mixture of the two) may be determined by decom- posing about 0.5 g of the abrasive material with hydrofluoric acid, taking up the residue in water and hydrochloric acid and determining the Al,O,. This weight multiplied by 5.48 and divided by the weight of sample gives the approximate percentage of feldspar in the abrasive material. Feldspar may be identified and the relative amounts of feldspar and quartz roughly deter- mined by means of the petrographic microscope. (4) ALKALI AS ALKALINE SALTS (TOTAL AKLALINITY OF MATTER INSOLUBLE IN ALCOHOL).—Titrate the filtrate from the deter- mination of matter insoluble in water with standard acid, using methyl orange as indicator. Calculate alkalinity to sodium car- bonate (Na,CO,). (d) Steve Test.—Transfer a weighed sample of the insoluble siliceous material to a No. 100 sieve and carefully brush through. Weigh the amount passing through and calculate percentage. After weighing transfer to a No. 200 sieve and treat in the same manner. Weigh the amount passing through and calculate per- centage. i Specification for Interior Varnish 5 from the top of the plate. Let panel stand in the same position for 20 minutes longer, then lay flat. An exaggerated condition of a dusty room shall be created by rubbing some cotton batting between the hands immediately over the panel. Let panel dry for a total of 48 hours in a well-ventilated room. If the comb marks show at this time, the varnish shall be rejected. If no comb marks show, the surface shall then be rubbed with pumice flour, water, and a felt pad with long, even, firm strokes back and forth in one or another direction, but not in circles, until every portion of the panel has been rubbed. Most of the pumice will then be removed from the pad and panel, and the varnish film given a ‘‘water rub” with the pad. A satisfactory rubbing varnish in the above test will yield a smooth, dull film even at those places where the dust particles have been encrusted in the film, and shall show no spots where the pumice has been ground into and become attached to the film, nor show any other evidence of gumming. No sweating shall occur anywhere on the film in 18 hours after rubbing. (2) Gas TEst.—A pparatus.—The necessary apparatus consists of a glass bell jar approximately 20 cm (8 inches) in diameter and 30 cm (12 inches) in height, inside dimensions, having a ground- glass rim; a ground-glass base plate of suitable size: a small, kerosene glowlamp without chimney, or a small alcohol lamp filled with kerosene, using a round wick not over 6 mm (14 inch) in diameter and adjusted to give a flame 2 cm (4/, inch) in height. A wire or a light wooden frame is fitted inside the jar and provided with a support for holding a disk of tin plate 15 cm (6 inches) in diameter in a horizontal position 5 cm (2 inches) above the wick of the lamp. The frame must also be provided with several other supports above this disk for holding in a horizontal position the various varnished panels under test. The test panels consist of semicircular pieces of bright tin plate approximately 15 cm (6 inches) in diameter.. The form and arrangement of the above apparatus is designed to provide an even distribution of the products of combustion over the test panels. Method.—First determine the normal time required for the varnish under examination to set to touch at room temperature. Divide this time by five to arrive at the different drying periods at which the varnish is to be tested in the gas tester. ‘Thus, if a varnish sets to touch in five hours, samples should be tested for resistance to gas at drying periods of one, two, three, and four 6 Circular of the Bureau of Standards hours; it is needless to use the fifth or five-hour period for the above varnish, as a varnish which has set to touch is practically immune to injury from gas fumes. Similarly a varnish which sets to touch in one hour should be tested for resistance to gas at drying periods of 12, 24, 36, and 48 minutes. Example.—A varnish which sets to touch in five hours is tested as follows: First, clean two of the semicircular, bright, tin-plate panels carefully with benzol. Flow the varnish on one-half of panel No. 1 at, say, ro a, m., and allow to drain in a nearly vertical position at room temperature. At 11 a. m., flow the varnish on the other half of panel No. 1; allow to drain as before. At 12 m. varnish one-half of panel No. 2, and at 1 p. m. varnish the other half, as above. At 2 p. m. place the two panels close together in a horizontal position on the upper supports of the frame. Light the lamp and set it under the circular tin. Place the bell jar in position, centering it as nearly as possible, properly seated on the eround-glass plate. If the chamber is tight and lamp properly adjusted, the flame will be extinguished in about four minutes. After the panels have been in the chamber for half an hour, remove the bell jar and examine the varnished panels for gas effects. : he varnish on all four sections should remain bright and clear without trace of pitting, ‘‘crow’s footing,” frosting, or other defects. 4, BASIS OF PURCHASE. Varnish shall be purchased by volume, the unit being a gallon of 231 cubic inches at 15.5° C. (60° F.). The volume may be deter- mined by measure, or, in case of large deliveries, it may be easier to determine the net weight and specific gravity at 15.5/15.5° ©. (60/60° F.) of the delivery. The weight per gallon in pounds can then be determined by multiplying the specific gravity by 8.33. The net weight in pounds divided by the weight per gallon gives the number of gallons. . | ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. AT 5 CENTS PER COPY V WASHINGTON : GOVERNMENT PRINTING OFFICE : 1922 tal A Oe U. S. Gov't Standard Specification, No. 66. DEPARTMENT OF COMMERCE. BUREAU OF STANDARDS. George K. Burgess, Director. CIRCULAR OF THE BUREAU OF STANDARDS, NO. 146. [Issued September 25, 1923.] UNITED STATES GOVERNMENT SPECIFICATION FOR WATER-RESISTING RED ENAMEL. FEDERAL SPECIFICATIONS BOARD. STANDARD SPECIFICATION NO. 66. This specification was officially adopted by the Federal Specifications Board on September 1, 1923, for the use of the Departments and Independent Estab- lishments of the Government in the purchase of water-resisting red enamei. CONTENTS. Page ERM ee alt ng wap inn pw gm owe c OPS rane ueee tans cere idee tlere sd crn cooks I So Seve AI a AE OPO SRN ALS Ce A SLPS ga i OL 2 2 Bpeeepiaee yearn rintloue si olde ied 2, eee eiden peered 4 ec etek. hen 2 en MNCS AE Ee i ie olla es Siig maid a micttie os ak 6 1. GENERAL. The material desired under this specification is an extremely durable, highest quality red enamel, suitable primarily for outside use. It should be made by grinding pure high color strength toluidine red toner (metanitro-paratoluidine-azo-betanaphthol), free from any base or substratum, with the very best water- resisting long oil spar varnish. The color and hiding power when specified shall be equal to those of a sample mutually agreed upon by buyer and seller. It must meet the following requirements: WEIGHT PER GALLON.—Not less than 7!% pounds. PIGMENT.—Not less than 6 per cent by weight; pigment to be composed entirely of pure high color strength toluidine red toner, free from any other organic coloring matter, base, or substratum. 61692 °—23 2 Circular of the Bureau of Standards. CoARSE PARTICLES AND ‘‘SKINS” (total residue retained on No. 325 sieve).—Not more than 0.5 per cent. NoNVOLATILE MaTtER.—Not less than 60 per cent by welghiee Set to Toucu.—In not more than 18 hours. Dry Harp AND ToucH.—In not more than 48 hours. WorKING PROPERTIBS.—Enamel must have good brushing, flowing, covering, and leveling properties and must not cake in the container. WATER RESISTANCE.—Dried film must withstand cold water for 18 hours and boiling water for 15 minutes without whitening, dulling, or change in color. TOUGHNESS.—Enamel must pass a 50 per cent Kauri reduction teStat eas oR ae Deliveries will, in general, be sampled and tested by the following ~ methods, but the purchaser ‘reserves the right to use any addttronal available information to ascertain whether the material meets the specification. 2. SAMPLING. It is mutually agreed by buyer and seller that a singh package out of each lot of not more than 1,000 packages be taken as repre- sentative of the whole. Whenever possible, an original unopened container shall be sent to the laboratory, and when for any rea- son this is not done the inspector shall thoroughly mix the con- tents of the container sampled, transfer not less than 1 quart to a clean, dry glass bottle or tin can, which must be nearly filled with the sample, securely stoppered with a new, clean cork or well- fitting cover or cap, sealed and distinctly labeled by the inspector. The inspector should take a duplicate from the container sampled to be held for check in case of dispute, and, when requested, should take a sample for the seller. 3. LABORATORY EXAMINATION. The tin panels used in the following tests shall all be cut from — bright tin plate weighing not more than 25 nor less than 19 g per square decimeter (0.51 to 0.39 pound per square foot). (Com- mercial No. 31 gauge bright tin plate should weigh about 0.44 pound per square foot. It is important that the tin plate used shall be within the limits set.) The panels shall be about 7.5 by 13 cm (3 by 5 inches) and must be thoroughly" cleaned with benzol immediately before using. (a) CAKING IN CONTAINER AND WORKING PROPERTIES.—When an original package is received in the laboratory, it shall be Specification for Water-Resisting Red Enamel. 3 weighed, opened, and stirred with a stiff spatula or paddle. The enamel must be no more difficult to break up than a normal good grade of enamel paint. The enamel shall finally be thoroughly mixed, removed from the container, and the container wiped clean and weighed. This weight subtracted from the weight of the original package gives the net weight of the contents. Apply some of the thoroughly mixed enamel, both by brushing and flowing, to clean glass plates. It should work easily under the brush. Dry both plates in a nearly vertical position. They should both dry without streaking, separating, or showing brush marks. A portion of thoroughly mixed enamél shall be placed in a clean container and the portions for the remaining tests promptly weighed out. (b) CoLOR AND HipiInc PowEr.—Place some of the enamel on a clean, clear glass plate. Place some of the standard agreed upon beside the sample on the plate, turn the glass over, and compare the colors by transmitted and reflected light. (c) WEIGHT PER GALLON.—Weigh a clean, dry, 100 ce gradu- ated flask. Fill to the mark with the thoroughly mixed enamel and weigh again. ‘The increase in weight expressed in grams, divided by 100, gives the specific gravity, which, multiplied by 8.33, gives the weight in pounds per gallon. (d) COARSE PARTICLES AND SKINS.—Dry in an oven at 105 to 110° C. a No. 325 sieve, cool, and weigh accurately. Weigh accurately about 50 g of the enamel, add 100 cc of kerosene, mix thoroughly, and wash with kerosene through the sieve, breaking up all lumps, but not grinding. After washing with kerosene until all but the particles too coarse to pass the sieve have been washed through wash all kerosene from the sieve with ether or petroleum ether, heat the sieve for one hour at 105 to 110° C., cool, and weigh. (e) PIGMENT.—Qualitative examination. Poe about 1 g of the thoroughly stirred enamel, previously strained through a No. 200 SIEVE: IM)..a )50..cC baler Add about 4o ce of chloroform (U.S. P.) and warm on the steath bath, stirring with a glass rod. A clear orange-red solution should result in a few minutes. Take another portion of the enamel and spread it with a spatula on a smooth, white surface, such as a piece of milk glass. Touch a few drops of alcoholic sodium hydroxide solution to the center of the film and rub well witha glass spatula. There should be no change in color.! _—_— 1 The presence of para nitraniline red is indicated by a violet color. 4 Circular of the Bureau of Standards. Quantitative. determination. Weigh 1 g (+ 10 mg) of the enamel and 6 g (+ 10 mg) of pure zinc oxide, place on a large glass plate, add 2 cc of linseed oil and rub up with a flat-bottomed glass pestle or muller, grinding with a circular motion 50 times. Gather up with a sharp-edge spatula and grind out twice more in like manner, giving the pestle a uniform pressure. Next weigh to + 1 mg an amount of pure high color strength toluidine red toner equal to 6 per cent of the weight of enamel taken, add 4 drops of linseed oil and rub up with the glass pestle. Then add 6 g of pure zinc oxide and 2 cc of linseed oil and treat in exactly the same manner as described above. Transfer por- tions of each paste to a clean microscope slide quite close together, and then draw a palette knife across both samples, so as to make them meet in a line. Compare the tints as shown on both sides of the glass. The color of the sample tested shall be not less than that of the selected standard, and the tone shall be not materially different from it. (7) NONVOLATILE MATTER.—Place a portion of the sample in a stoppered bottle or weighing pipette. Weigh container and sam- ple. Transfer about 1.5 g of the sample to a weighed flat-bot- tomed metal dish about 8 cm in diameter (a friction-top can plug). Weigh container again and by difference calculate the exact weight of the portion of sample transferred to the weighed dish. Heat _ dish and contents in an oven maintained at 105 to 110° C. (221 to 230° F.) for three hours. Cool and weigh. From the weight of the residue left in the dish and weight of the sample taken calcu- late the percentage of nonvolatile residue. (g) Dry1inc Time.—Pour the enamel on one of the tin panels described above. Place the panel in a nearly vertical position in a well-ventilated room, but not in the direct rays of the sun. The atmosphere of this room must be free from products of combus- tion or laboratory fumes. The temperature of the room should be from 21 to 32°C. (7o to 90° F.). The film is tested at points not less than 2.5 cm (1 inch) from the edges of the film by touch- ing lightly with the finger. The enamel is considered to have set to touch when gentle pressure of the finger shows a tacky condition, but none of the enamel adheres to the finger. The enamel is con- sidered to have dried hard when the pressure that can be exerted between the thumb and finger does not move the film or leave a mark which remains noticeable after the spot is lightly polished. If rapid, light rubbing breaks the surface, the sample is considered not to have satisfactorily dried hard. In case the test shows time of setting to touch or drying hard more than 18 and 48 hours, Specification for Water-Resisting Red Enamel. 5 respectively, two additional tests shall be run on different days, and if the enamel does not meet the above drying and hardening requirements on both of these additional tests it shall be con- sidered unsatisfactory. In cases where different laboratories fail to agree on the drying test, due to different atmospheric condi- tions, and umpire tests are necessary, such tests shall be made in a well-ventilated room maintained at a temperature of 70° F. and relative humidity of 65 per cent saturation. (h) WATER RESISTANCE.—Pour the enamel on two of the tin panels described above and allow to dry under the conditions described in paragraph (g) for 48 hours. Place one of these panels in a beaker containing about 2.5 inches of distilled water at room temperature (immersing the end of the panel which was upper- most during the drying period) and leave in water for 18 hours. The enamel shall show no whitening and no more than very slight dulling either when observed immediately after removing from the water or after drying for 2 hours. Place the other panel in a beaker containing about 2.5 inches of boiling distilled water (im- _mersing the end of the panel which was uppermost during the drying period) and allow to remain in the boiling water for 15 minutes. The enamel shall show no whitening, no more than a very slight dulling, and no material change in color, either when observed immediately after removing from the water or after drying for 2 hours. (2) TOUGHNESS.—The toughness of the enamel is determined by the Kauri reduction test, as follows: By proportioriately reduc- ing its toughness by the addition of a standard solution of “‘run- Kauri” gum in pure spirits of turpentine. (1) Preparation of the “run Kawur.’’—Arrange a distillation flask, water-cooled condenser, and a tared receiver on a balance. Place in the flask about one-third of its volumetric capacity of clear, bright hard pieces of Kauri gum broken to pea size. Carefully melt and distil until 25 per cent, by weight, of the gum taken is collected in the tared receiver. (At the end of the distil- lation the thermometer in the distillation flask with the bulb at the level of the discharging point of the flask should register about 316° C. (600° F.).) Pour the residue into a clean pan, and when cold break up into small pieces. (2) Preparation of standard “run-Kaurv’”’ solutton.—Place a quantity of the small broken pieces of run-Kauri, together with twice its weight of freshly redistilled spirits of turpentine, using only that portion distilling over between 153 and 170° C. (308 and 338° F.) in a carefully tared beaker. Dissolve by heating 6 Circular of the Bureau of Standards. to a temperature of about 149° C. (300° F.) and bring back to correct weight when cold by the addition of the amount of redis- tilled spirits of turpentine necessary to replace the loss by evapora- tion during the dissolving of the gum. (3) Reduction of the enamel.—Having carefully determined the nonvolatile content of the enamel according to the method under paragraph (f) of this specification, take 100 g of the enamel and add to it an amount of the standard run-Kauri solution equiva- lent to 50 per cent, by weight, of the nonvolatile matter in the enamel. Mix the enamel-and the solution thoroughly. (4) Application of the enamel.—Flow a coat of the enamel thus reduced on one of the tin panels described above and let stand in a nearly vertical position at room temperature for one hour. Next place the panel in a horizontal position in a properly venti- lated oven and bake for five hours at 95 to 100° C. Remove the panel from the oven and allow to cool at room temper ears prefer- ably 24° C. (75° F.) for one hour. (5) Bending the panel.—Place the panel with the enameled side uppermost over a 3-mm (% inch) rod, held firmly by suitable supports, at a point equally distant from the top and bottom edges of the panel and bend the panel double rapidly. The enamel must show no cracking whatsoever at the point of bending. For accurate results the bending of the panel should always be done at 24° C. (75° F.), for a lowering of the temperature will lower the percentage of reduction that the enamel will stand without cracking, while an increase in the temperature increases the percentage of reduction that the enamel will stand. 4. BASIS OF PURCHASE. Enamel shall be purchased by volume, the unit being a gallon of 231 cubic inches at 15.5° C. (60° F.). The volume may be determined by measure or, in case of large deliveries, it may be easier to determine the net weight and specific gravity at 15.5/15.5° ee (60/60° F.) of the delivery. The weight per gallon in pounds can then be determined by multiplying the specific gravity by 8.33. The net weight in pounds divided by the weight per gallon ee the number of gallons. ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFIC® WASHINGTON, D. C. AT 5 CENTS PER COPY PURCHASER AGREES NOT TO RESELL OR DISTRIBUTE THIS COPY FOR PROFIT.—PUB. RES. 57, APPROVED MAY II, 1923. 4 ~, « U. S. Gov't Standard Specification, No. 67. DEPARTMENT OF COMMERCE. BUREAU OF STANDARDS. George K. Burgess, Director. CIRCULAR OF THE BUREAU OF STANDARDS NO. 147. (Issued September 19, 1923.) UNITED STATES GOVERNMENT SPECIFICATION FOR GLOSS INTERIOR LITHOPONE PAINT, WHITE AND LIGHT TINTS. FEDERAL SPECIFICATIONS BOARD. STANDARD SPECIFICATION NO. 67. This specification was officially adopted by the Federal Specifications Board on September |, 1923, for the use of the Departments and Independent Establish- ments of the Government in the purchase of gloss interior lithopone paint, white and light tints. CONTENTS. Page. Se se dao cigs eens d a ns tang ee ns deg eee bel I IRE gs eck oa oe rads ccs tee hewedeaecuesaue 2 EE rR alls ae es ee OL oe ne ee ee 3 RR Tg ec a rises S Sistc vip ene Wide Gu ajerhelnre mip vsie' dw «aid a abe 6 a ies ce ceases tase eke cbse eg es seer de ss aes 8 1. GENERAL. This specification covers ready-mixed lithopone paints, fre- quently known as gloss mill white, in white and a variety of light tints. Paints under this specification are not intended for out- side exposure. ‘They shall dry to gloss opaque coats that will adhere well to wood, metal, and plaster, stand washing with soap and water, and show no material change in color on exposure to light or material yellowing when kept in the dark. ‘The paint shall be purchased by volume (231 cubic inches to the gallon). 61693°—23 2 Circular of the Bureau of Standards. (a) P1cMENT.—The pigment shall consist of : Maximum.) Minimum. Per cent. | Per cent. Li OPOMe be wee ong& jcc vis wo's coh wcteleleie'u'e wie alae 8. dieihol ale hela a tain ise, o ara 9m alps} a: bvale Wate opty te ne rnana ana 65 ZINC OFIGS, co cis BUREAU OF STANDARDS. George K. Burgess, Director. CIRCULAR OF THE BUREAU OF STANDARDS, No. 163. | [February 20, 1924.] UNITED STATES GOVERNMENT SPECIF ICATION FOR ‘TITANIUM PIGMENT, DRY AND PASTE. FEDERAL SPECIFICATIONS BOARD. STANDARD SPECIFICATION No. 115. This specification was officially adopted by the Federal Specifications Board on February 20, 1924, for the use of the Departments and Independent Estab- lishments of the Government in the purchase of titanium pigment, dry and paste. CONTENTS. Page EE Als ie us 7 Feet oe Moke, a, ee ee 1 peerrmrtrgr Tex cae td, S MIL BIS, TO bad SOFT BR ds sla aide 2 3. Laboratory examination, dry pigment.............0.0/ 006.002.0000 22, 3 4. Laboratory examination, PSC. - ueneaten ide «oe d... Seoeeimer ll. seer a. 6 CUE ere ee A one he ae ORE, ae 9 1. GENERAL. Titanium pigment may be ordered in the form of dry pigment or paste ground in linseed oil. The material shall be purchased by net weight. (2) Dry PicmMENT.—The pigment shall be 25 per cent titanium oxide precipitated upon and coalesced with 75 per cent of blanc fixe (precipitated barium sulphate). It shall be thoroughly washed, shall be free from adulterants, and shall meet the fol- lowing requirements. Color—Color strength.—When specified, the color and color strength shall be equal to that of a sample mutually agreed upon by buye and seller. 84628°—24 2 Circular of the Bureau of Standards i- | Marxi- Min mum. mum. Per cent. | Per cent. Coarse particles retdined on IN0..325 SeV@. 0.2 occ cdi ot oe es eeies ssa veins 0 oiedciesieisien oiininwem .0 Titanium oxide (TiOds). . decay coms aide ep turn oe8 terete + de ts Spies coh ab aia re 24. OF sc uclaes Soe Total impurities, including moisture... ecu kk odeacds doe sdeeccbodece bacnbe tee analy at eta maam 1.0 The remainder shall be barium culghabe. (b) Past#.—The paste shall be made by thoroughly grinding the above-described pigment with pure, raw, or refined linseed oil. The paste as received shall not be caked in the container and shall break up readily in oil to form a smooth paint of brushing consistency. The paste shall consist of: Mini- Maxi- mun, mum, Per cent. | Per cent. Pigtiont 2065 os naccc hws cise Gaui svboew ohisaewines Bes male els hs aimcep es cate ieee etn 80.0 85.0 Linseedl ollie os occ cei ceca ons Swe oe Wnt Ciba gle wie wlan iw mine's eie ele ee eae ea 15.0 20. 0 Moisture and other volatile matterec: <0. s A 7. voc ee ne. adn agen sob secek sek eae eb als eee eins ot Coarse particles and ** skins ” (total residue retained on No. 325 sieve, based on pig- is ment) 2 Deliveries will, in general, be sampled and tested by the following methods, but the purchaser reserves the right to use any additional available information to ascertain whether the materval meets the specification. | 2. SAMPLING. It is mutually agreed by buyer and seller that a single package out of each lot of not more than 1,000 packages be taken as repre- sentative of the whole. (a) Dry Picment.—The package is to be opened by the inspector and a sample of not less than 5 pounds taken at random from the contents and sent to the laboratory for test. (b) Paste.—Whenever possible, an original unopened con- tainer shall be sent to the laboratory; and when this is for any reason not done the inspector shall determine by thoroughly testing with a paddle or spatula whether the material meets the requirement regarding not caking in the container. (See 4 (@).) After assuring himself that the paste is not caked in the can, the inspector shall draw a sample of not less than 5 pounds of the thoroughly mixed paste, place it in a clean, dry metal or glass container, which must be filled with the sample, closéd with a tight cover, sealed, marked, and sent to the laboratory for test with the inspector’s report on caking in container. Specification jor Titanium Pigment 3 When requested, a duplicate sample may be taken from the same package and delivered to the seller, and the inspector may - take a third sample to hold for test in case of dispute. 3. LABORATORY EXAMINATION, DRY PIGMENT. (a) Coror.—Take 5 g of the sample, add 1.5 cc of linseed oil, rub up on a stone slab or glass plate with a flat-bottomed glass or stone pestle or muller to a uniform smooth paste. Treat in a simi- lar manner 5 g of the standard titanium pigment. Spread the two pastes side by side on a clear, colorless glass plate and compare the colors. If the sample is as white as or whiter than the “ stand- ard,”’ it passes this test. If the ‘‘standard” is whiter than the sample, the material does not meet the specification. (6) Color StTRENGTH.—Weigh accurately 0.01 g of lamp- black, place on a large glass plate or stone slab, add o.2 cc of lin- seed oil and rub up with a flat-bottomed glass pestle or muller, then add exactly 10 g of the sample and 2.5 cc of linseed oil, and grind with a circular motion of the muller 50 times; gather up with a sharp-edged spatula and grind out twice more in a like manner, giving the pestle a uniform pressure. ‘Treat another 0.o1 g of lampblack in the same manner, except that 10 g of stand- ard titanium pigment is used instead of 10g of the sample. Spread the two pastes side by side on a glass microscope slide and com- pare the colors. If the sample is as light as or lighter in color than the “standard,” it passes this test. If the ‘‘standard”’ is lighter in color than the sample, the material does not meet the specification. (c) COARSE PARTICLES.'—Dry in an oven at 105 to 110° C. a No. 325 sieve, cool, and weigh accurately. Weigh 10 g of the sample, wash with water through the sieve, breaking up all lumps either by gentle pressure with a pestle in a mortar, but not grind- | ing, or with a brush on the sieve. After washing with water until all but the particles too coarse to pass the sieve have been washed through, dry the sieve for one hour at 105 to 110° C., cool, and weigh. (d) QUALITATIVE ANALYSIS.—Place a small amount (about one- half gram) of the sample in a 250 cc Pyrex glass beaker; add 20 ce of concentrated sulphuric acid and 7 to 8 g of ammonium sul- phate. Mix well, and boil for a few minutes. The sample should 1 For a general discussion of sieve tests of pigments and data regarding many pigments on the market seed Circular No. 148 of the Educational Bureau, scientific section, Paint Manufacturers’ Association of the United States. 4 Circular of the Bureau of Standards. go completely into solution; a residue denotes the presence of silica or siliceous matter. Cool the solution, dilute with 100 cc of water, heat to boiling, settle, filter, wash with hot 5 per cent sulphuric acid until free from titanium, and test the residue for lead, etc. ‘Test the filtrate for calcium, zinc, iron, chromium, etc., by regular methods of qualitative analysis. For the iron deter- mination take a portion of the filtrate, add 5 g of tartaric acid, make slightly ammoniacal, pass in hydrogen sulphide in excess, and digest at the side of a steam bath for a while. No precipitate denotes absence of iron, nickel, cobalt, lead, copper, ete. A black precipitate easily soluble in dilute hydrochloric acid denotes iron. For titanium test a small portion of the original filtrate with hydrogen peroxide (a clear yellow-orange color should result) and another portion with metallic tin or zine (a vee blue to violet coloration should result). The pigment should show negative tests for sulphide sulphur, carbonates, and appreciable water-soluble matter. (ec) MoisturE.—Place 1 g of the sample in a wide-mouth, short weighing tube provided with a glass stopper. Heat with the stop- per removed for two hours at a temperature between 105 and 110° C. Insert the stopper, cool, and weigh. Calculate the loss in weight as moisture. (f) MATTER SOLUBLE IN WATER.—Transfer 2.5 g of the pigment to a graduated 250 cc flask, add 100 cc of water, boil for five minutes, cool, fill to the mark with water, mix, and allow to settle. Pour the supernatant liquid through a dry filter paper and discard the first 20 cc. ‘Then evaporate roo cc of the clear filtrate to dryness in a weighed dish, heat for one hour at 105 to 110° C., cool, and weigh. (g) Tyrantum Oxipk.—Transfer 0.5 g of the dried sample to a 250 cc Pyrex beaker, add 20 cc of concentrated sulphuric acid and 7 to 8 g of ammonium sulphate. Mix well and heat on a hot plate until fumes of siiphuric acid are evolved, and then con- tinue the heating over a strong flame until solution is complete (usually not over five minutes of boiling) or it is apparent that the residue is composed of silica or siliceous matter. Caution should be observed in visually examining this hot solution. Cool the solution, dilute with 100 ce of water, stir, heat carefully to boiling while stirring, settle, filter through paper and transfer the precipi- tate completely to the paper. Wash the insoluble residue with cold 5 per cent (by volume) sulphuric acid until titanium is removed. Specification for Titanium Pigment. 5 Dilute the filtrate to 200 cc and add about 10 ce of ammonia, specific gravity 0.90, to lower the acidity to approximately 5 per cent sulphuric acid (by volume). Wash out a Jones reductor ? with dilute 5 per cent (by volume) sulphuric acid and water, leaving sufficient water in the reductor to fill to the upper level of the zinc. (These washings should require not more than one or two drops of o.1 N potassium per- manganate solution to obtain the pink color.) Empty the receiver, and put in it 25 cc (measured in a graduate) of ferric sulphate solution. (See Reagents.) Reduce the prepared tita- nium solution as follows: (1) Run 50 cc of the 5 per cent sulphuric acid solution through the reductor at a speed of about 100 cc per minute; (2) follow this with the titanium solution; (3) wash out with 100 cc of 5 per cent sulphuric acid; (4) finally run through about 100 cc of water. Care should be observed that the reductor is always filled with solution or water to the upper level of the zinc, Gradually release the suction, wash thoroughly the glass tube that was immersed in the ferric sulphate solution, remove the receiver, and titrate immediately with 0.1 N potassium perman- ganate solution. (See Reagents.) 1 cc o.1 N KMnO,=0.00481 g Ti =0.00801 g TiO, Run a blank determination, using the same reagents, washing the reductor as in the above determination. Subtract this per- manganate reading from the original reading and calculate the final reading to titanium dioxide (TiO,) (which will include iron, chromium, arsenic, and any other substance which is reduced by zinc and acid). (See 3 (2) for reporting TiO,,.) 3 (h) DETERMINATION OF BARIUM SULPHATE.—Ignite and weigh the precipitate of BaSO, obtained in separating the titanium.‘ (See 3 ().) | (1) IRON OxipE.—Prepare a standard ferric solution contain- ing 0.00001 g Fe per cc. (See Reagents.) Weigh ar g portion of the sample and treat as in 3 (g), transfer without filtering to a 200 ce flask, cool, fill to the mark, and determine iron colorimetri- cally in 50 cc aliquots in the following manner. Filter through a 2 Directions for preparing a Jones reductor may be found in Blair, ‘‘ The Chemical Analysis of Iron,” &th ed. Lippincott & Co., or Treadwell-Hall, ‘‘ Analytical Chemistry,” sth ed. J. Wiley & Sons, p. 638 8 Any other accurate method of determining titanium oxide may be used. For a discussion of various methods see ‘‘The Analysis of Silicate and Carbonate Rocks,” by W. F. Hillebrand, U. S. Geological Survey Bulletin 700. ; ‘If the sample is impure it may be necessary to purify this precipitate, using appropriate methods. 84628°—24 2 6 Circular of the Bureau of Standards dry filter paper (discarding the first 20 cc), and transfer 50 cc of the filtrate to a clean roo ce Nessler tube or other color com-’ parator. Add a drop or two of 0.1 N KMnO, solution, to oxidize any ferrous iron until a faint pink color is obtained. Add 10 cc of ammonium or potassium thiocyanate solution (see Reagents), dilute to 100 cc, and mix thoroughly. Compare the color imme- diately with a series of standards, prepared side by side with the sample in similar tubes. Prepare the standards from the standard ferric solution so as to have a range of from 0.000005 g Fe to 0.00004 g (0.5 to 4.0 cc). Dilute these amounts with distilled water to about 50 cc. Add just enough o.1 N KMn0O, to produce a faint pink and then 10 ec of the thiocyanate solution. Finally dilute all standards to 100 cc. For a single sample it is more convenient to run the standard Fe solution from a burette into a Nessler tube containing the acid, 10 cc of the thiocyanate solution, and 60 to 70 cc of distilled water until the depth of the color thus produced on dilution to 100 cc and mixed exactly matches the sample. From the burette reading calculate the amount of Fe. The color comparisons must be made immediately after the stand- ards are prepared. Calculate the total iron found to Fe,O, and report as such. Calculate the TiO, equivalent by multiplying by the factor 1.003 and subtract this figure from the total titanium oxide as deter- mined in 3 (g) and report the remainder as TiO,. 4. LABORATORY EXAMINATION, PASTE. (a) CAKING IN CONTAINER.—When an original package is re- ceived in the laboratory it shall be weighed, opened, and stirred with a stiff spatula or paddle. The paste must be no more diffi- cult to break up and show no more caking than a normal good grade of titanium pigment paste. The paste shall finally be thoroughly mixed, removed from the container, the container wiped clean, and weighed. This weight subtracted from the weight of the original package gives the net weight of the con- tents. A portion of the thoroughly mixed paste shall be placed in a clean container, and the portions for the remaining tests promptly weighed out. (6) MIxING witH LINSEED O1L.—One hundred grams of the paste shall be placed in a cup, 40 cc of linseed oil added slowly with careful stirring and mixing with a spatula or paddle. The re- sulting mixture must be smooth and of good brushing consistency. Flow a portion of this paint on a clean glass plate. Let standina nearly vertical position at room temperature (65 to 100° F.). Specification for Titanium Pigment. ‘i The film after four hours shall show no streaking or separation: within a distance of 4 inches from the top. (c) MoIstuRE AND OTHER VOLATILE MATTER.—Weigh ac- curately from 3 to 5 g of the paste into a tared flat-bottomed dish, about 5 cm in diameter, spreading the paste over the bottom. Heat at 105 to 110° C. for one hour, cool, and weigh. Calculate the loss in weight as the percentage of moisture and other volatile matter. (d) PERCENTAGE OF PIGMENT.—Weigh accurately about 15 g of the paste into a weighed centrifuge tube. Add 20 to 30 ce of “extraction mixture’ (see Reagents), mix thoroughly with a glass rod, wash the rod with more of the extraction mixture, and add sufficient of the reagent to make a total of 60 cc in the tube. Place the tube in the container of a centrifuge, surround with: water, and counterbalance the container of the opposite arm with a similar tube or a tube with water. Whirl at a moderate speed until clear. Decant the clear supernatant liquid. Repeat the extraction twice with 40 cc portions of extraction mixture, and once with 40 cc of ether. After drawing off the ether, set the tube in a beaker of water at about 80° C. or on top of a warm oven for 10 minutes, then in an oven at 110 to 115° C. for two hours. Cool, weigh, and calculate the percentage of pigment. (e) EXAMINATION OF PiGMENT.—Grind the pigment from (d) to a fine powder, pass through a No. 80 sieve to remove any “skins,” and preserve in a stoppered tube and apply tests 3 (d), (7), (9), (2), and (7). If required, apply tests 3 (a) and (b) in comparison with a portion of pigment extracted from the standard paste in exactly the same manner as in extracting the sample. (7) PREPARATION oF Farry Actps.—To about 25 g of the paste in a porcelain casserole add 15 cc of aqueous sodium hydroxide (see Reagents), and 75 cc of ethyl alcohol, mix and heat uncovered on a steam bath until saponification is complete (about one hour). Add too cc of water, boil, add sulphuric acid of specific gravity 1.2 (8 to 10 cc in excess), boil, stir, and transfer to a separatory funnel to which some water has been previously added. Draw off as much as possible of the acid aqueous layer, wash once with water; then add 50 cc of water and 50 cc of ether. Shake very gently with a whirling motion to dissolve the fatty acids in the ether, but not violently, so as to avoid forming an emulsion. Draw off the aqueous layer and wash the ether layer with one 15 cc portion of water and then with 5 cc portions of water until free from sulphuric acid. Then draw off completely the water layer. 8 Circular of the Bureau of Standards. Transfer the ether solution to a dry flask, and add 25 to 50 g of anhydrous sodium sulphate. Stopper the flask and let stand with occasional skaking at a temperature below 25° C. until the water is completely removed from the ether solution, which will be shown by the solution becoming perfectly clear above the solid sodium sulphate. Decant this clear solution (if necessary through a dry filter paper) into a dry roo cc Erlenmeyer flask. Pass a rapid current of dry air (pass through a CaCl, tower) into the mouth of the Erlenmeyer flask and heat to a temperature below 75°C. on a dry hot plate until the ether is entirely driven off. It is important to follow all of the details, since ether generally contains alcohol, and afler washing with water always contams water. It is very difficult to remove water and alcohol from fatty acids by evaporation, but the washing of the ether solution and sub- sequent drying with anhydrous sodium sulphate removes both water and alcohol. Ether, in the absence of water and alcohol, 1s easily removed from faity acids by gentle heat. The fatty acids prepared as above should be kept in a stoppered flask and examined at once. (g) TEST FOR MINERAL OIL AND OTHER UNSAPONIFIABLE MAT- TER.—Place 10 drops of the fatty acid (f) ina 50 cc test tube, add 5 cc Of alcoholic soda (see Reagents), boil vigorously for five min- utes, add 4o ce of water, and mix; a clear solution indicates that not more than traces of unsaponifiable matter are present. If the solution is not clear, the oil is not pure linseed oil. (h) IODINE — oF Farry Acips.—Place a small quantity of the fatty acids! (f) in a small weighing burette or beaker. Weigh accurately. | Transfer (by dropping) about 0.15 g (0.10 to 0.20 g) to a 500 cc} bottle having a well-ground glass stopper, or an Erlenmeyer flask having a specially flanged neck for the iodine test. Reweigh the) burette or beaker and determine the amount of sample used. Add ro cc of chloroform. Whirl the bottle to dissolve the sample. Add 1o ce of chloroform to two empty bottles like that used for the sample. Add toeach bottle 25 cc of the Hanus solution (see Reagents) and let stand, with occasional shaking, for one-half hour. Add ro cc of the 15 per cent potas- sium-iodide solution and 100 cc of water, and titrate with standard sodium thiosulphate, using starch as indicator. ‘The titrations on the two blank tests should agree within 0.1 cc. From the iodine value of the thiosulphate solution and the difference between the average of the blank titrations and the titration on the sample, calculate the iodine number of the sample tested. (lodine number Specification for Titanium Pigment. 9 is centigrams of iodine to 1 g of sample.) If the iodine number is less than 170, the oil does not meet the specification. (2) COARSE PARTICLES AND SKINS.—Dry in an oven at 105 to 110° C. a No. 325 sieve. Weigh an amount of paste containing 10 g of pigment (see 4 (d)), add 100 cc of kerosene, mix thoroughly, and wash with kerosene, through the sieve, breaking up all lumps but not grinding. After washing with kerosene until all but particles too coarse to pass the sieve have been washed through, wash all kerosene from the sieve with ether or petroleum ether, heat the sieve for one hour at.105 to 110° C., cool, and weigh. 5. REAGENTS. (a) EXTRACTION MIxTURE.— 10 volumes ether (ethyl ether). 6 volumes benzol. 4 volumes methyl alcohol. I volume acetone. (b) AguEous Soprum HyproxipEe.—Dissolve 100 g sodium hydroxide in distilled water and dilute to 300 ce. (c) STANDARD SopiuM THIOSULPHATE SOLUTION.— Dissolve pure sodium thiosulphate in distilled water that has been well boiled to free it from carbon dioxide, in the proportion of 24.83 g of crys- tallized sodium thiosulphate to 1,000 cc of the solution. It is best to let this solution stand for about two weeks before standard- izing. Standardize with pure resublimed iodine.’ ‘This solution will be approximately decinormal, and it is best to leave it as it is after determining its exact iodine value rather than to attempt to adjust it to exactly decinormal. Preserve in a stock bottle pro- vided with a guard tube filled with soda lime. (d) STARCH SOLUTION.—Stir up 2 to 3 g of potato starch or 5 g of soluble starch with 100 cc of 1 per cent salicylic acid solution, add 300 to 400 cc of boiling water, and boil the mixture until the starch is practically dissolved, then dilute to 1 liter. (e) Potasstum IopipE SoLuTIon.—Dissolve 150 g of potassium iodide free from iodate in distilled water, and dilute to 1,000 cc. (f) HANUS SOLUTION.—Dissolve 13.2 g of iodine im 1,000 cc of 99.5 per cent glacial acetic acid which will not reduce chromic acid. Add enough bromine to double the halogen content, determined by titration (3 cc of bromine is about the proper ’ Tread well-Hall, Analytical Chemistry, 2, sth ed., p. 645. IO Circular of the Bureau of Standards. amount). The iodine may be dissolved by the aid of heat, but the solution should be cold when the bromine is added. (g) ALconotic Sopium HyproxinE SoLuTIoN.—Dissolve pure sodium hydroxide in 95 per cent ethyl alcohol in the proportion of about 22 g per 1,000 cc. Let stand in a stoppered bottle. De- cant the clear liquid into another bottle and keep well stoppered. This solution should be colorless or only slightly yellow when used, and it will keep colorless longer if the alcohol is previously treated with sodium hydroxide (about 80 g to 1,000 cc), kept at about 50° C. for 15 days and then distilled. (hk) 0.1 N Porasstum PERMANGANATE SOLUTION.—Dissolve 3.161 g of pure potassium permanganate in a liter of distilled water, let stand 8 to 14 days, siphon off the clear solution (or filter through an asbestos filter), and standardize as follows: In a 400 cc beaker dissolve 0.25 to 0.30 g of Bureau of Standards’ sodium oxalate in 250 cc of hot water (80 to 90° C.) and add 15 cc of dilute sulphuric acid (1:1). Titrate at once with the potas- sium permanganate solution, stirring the lquid vigorously and continuously. The permanganate must not be added more rapidly than 10 to 15 ce per minute, and the last 0.5 to r cc must be added dropwise with particular care to allow each drop to be fully decolorized before the next is introduced. The solution should not be below 60° C. by the time the end point is reached. (More rapid cooling may be prevented by allowing the beaker to stand on a small asbestos-covered hot plate during the titration. The use of a small thermometer as a stirring rod is most convenient.) The weight of sodium oxalate used multiplied by 0.8334 gives its iron equivalent, or multiplied by 1.1954 gives its titanium dioxide (TiO,) equivalent*. The permanganate solution should be kept in a glass-stoppered bottle painted black to keep out light. (i) FERRIC SULPHATE SOLUTION For TrTanrumM.—A solution containing 2 per cent of iron as ferric sulphate is desired and may be prepared as follows: Dissolve 20 g of pure iron or plain carbon steel in a slight excess of hydrochloric acid, oxidize with nitric acid, heat with about 80 cc of sulphuric acid until fumes are evolved, finally cool, and dilute to 1,000 cc, set on steam bath, until dissolved, and filter if necessary. Add o.1 N permanga- nate solution until a faint pink color shows that any ferrous iron has been oxidized. Ferric ammonium sulphate may also be used’. 6 International Atomic Weights, 1921-22. 7 Gooch, Methods in Chemical Analysis, 1st ed., p. 426. Specification for Titanium Pigment. II (7) STANDARD FERRIC SULPHATE SOLUTION FOR COLORIMET- RIC DETERMINATION OF IRON.—Determine the strength of the ferric solution reagent used in 5 (i) in terms of iron and dilute this solution until one is obtained of the strength 1 cc =0.00001 g Fe. (k) Potasstum TurocyaNaTe INDICATOR.—Prepare a 2 per cent solution of the pure salt in distilled water. ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D. C, AT 5 CENTS PER COPY Vv h i, : 4 . Cas b SOY, WOR ORE eRe. 1) oD fate Ce RESET ie, OE en Fs a ae i iets th wakes % t ns e a te o. % Ps’ Se Li El - 4 ; ot ra ay ’ 7 F y ois f +. tm oe ae ‘ vy a ‘ a t ) : se r £18 ae > Sh ye , { si wu 6 ry Ay My es 4 ; ye ) vy ( = at é oa ie gran lane t & I * JV £ 0 . y ' ‘ ’ i tg U. S. Gov’t Master Specification, No. 137 DEPARTMENT OF COMMERCE BUREAU OF STANDARDS George K. Burgess, Director CIRCULAR OF THE BUREAU OF STANDARDS, No. 165 [Issued June 21, 1924] UNITED STATES GOVERNMENT MASTER SPECIFICATION FOR OLIVE DRAB PAINT (SEMIPASTE AND READY-MIXED) FEDERAL SPECIFICATIONS BOARD SPECIFICATION No. 137 This specification was officially adopted by the Federal Specifications Board on May 1, 1924, for the use of the Departments and Independent Establishments of the Government in the purchase of olive drab paint (semipaste and ready- mixed) CONTENTS 4. Laboratory examination, ready-mixed PaintLe se et Fee ETN TOs ge ARCS oe ek” < eae alga aE PERE SC aaan aaC LS remeruerrere HEC WAPI 0S NN ee 11 Perro moore IB tOrmatlon 7 eS e N De As Serme eee eee nd Poa eer epeciiicatiting. cu) ole kc er eee 11 I. CLASSES Olive drab paint shall be of the following classes: Semipaste in lineseed oil and ready mixed. 102446°—24 yt CIRCULAR OF THE BUREAU OF STANDARDS II. MATERIAL No details. III. GENERAL REQUIREMENTS No details. IV. DETAIL REQUIREMENTS 1. PIGMENT The pigment shall be composed of: Ingredients % Maximum | Minimum Per cent Per cent White lead (basic carbonate, basic sulphate, or a mixture thereof) --.....---.----|-------.---- 35 PAU OXUAS CLO) hss Re i a ie oka Ped pts Meets! S 30 White mineral pigments (containing no lead or zinc compounds), pure tinting colors, or. any mixture thereof. . 225.225 2226.55 nen soos sean e ee BO. Peas ae PirearG GOlOTS oS ee ecu pa acw een Laveen mecha eee geet Noten (Sec. ee al lOnIGe SUL DAU oo 8 oo ee er 2 oo a a ai eee ee IN On@s; Ae so osee In no case shall the sum of the basic lead carbonate, basic lead sulphate, and zinc oxide be less than 70 per cent. The lead and zinc pigments may be introduced in the form of any mixture pre- ferred of basic carbonate white lead, basic sulphate white lead, zinc oxide, or leaded zinc, provided the above requirements as to compo- sition are met. The difference between the total lead weighed as lead sulphate and the lead sulphate equivalent to the chromium found, multiplied by the factor 0.883 shall be considered white lead. It is not possible to determine the amount of lead carbonate and lead sulphate when carbonates or sulphates of other metals, such as calcium, are present. Also neither basic lead carbonate nor basic lead sulphate is a definite compound. The factor to convert PbSO, to (PbCO,), Pb(OH), is 0.854, to convert PbSO, to PbSO,PbO is 0.868, and to convert PbSO, to (PbSO,), PbO is 0.913. The arbitrary factor used under this specification is the mean of the largest and smallest of these three factors. | 2. LIQUID The liquid in semipaste paint shall be entirely pure raw or refined linseed oil; in ready-mixed paint it shall contain not less than 85 per cent pure raw linseed oil, the remainder to be combined drier and thinner. The thinner shall be turpentine, volatile mineral spirits, or a mixture thereof. 3. SEMIPASTE Semipaste shall be made by thoroughly grinding the pigment with pure raw or refined linseed oil. The semipaste as received, and three months thereafter, shall be not caked in the container and shall break up readily in linseed oil to SPECIFICATION FOR OLIVE DRAB PAINT 3 form a smooth paint of brushing consistency. It shall mix readily with linseed oil, turpentine, or volatile mineral spirits, or any com- bination of these substances, in all proportions without curdling. The color and hiding power when specified shall be equal to those of a sample mutually agreed upon by buyer and seller. The weight per gallon shall be not less than 18 pounds. The paste shall con- sist of: Ingredients Maximum | Minimum Per cent Per cent 77 ga REE a a ed eee ae A ee oe 73 NR ee ca wk ip sn amore mene ek 27; 23 Moisture and ofher volatile matter... | _.0.....-..20.---- 2 n 0.7 |azoues ee Coarse particles and ‘‘skins’’ (total residue retained on No. 325 sieve based on OE BE eh) es SS ae oe ey > ee MMe tine Oe) Wee ge ee 2H0ne Soe ees ae 4. READY-MIXED PAINT Ready-mixed paints shall be well ground, shall not settle badly or cake in the container, shall be readily broken up with a paddle to a smooth uniform paint of good brushing consistency, and shall dry within 18 hours to a full oil gloss without streaking, running, or sagging. The color and hiding power when specified shall be equal to those of a sample mutually agreed upon by buyer and seller. The weight per gallor shall be not less than 15 pounds. The paint shall consist of: Ingredients Maximum | Minimum Per cent Per cent Seen ie mee ce ate ee ee ee ee ceth 66 62 Liquid (containing at least 85 per cent linseed oil) ______________________________- 38 34 ee SPLEEN SO 6 Car eR A Eh ee. OI BS, NR in dN 0: 6 lege cnees ee Coarse particles and ‘‘skins’’ (total residue retained on No. 325 sieve based on eS Breer Ps a ed fs ee Sa ee 2:0: 225. eee V. METHODS FOR SAMPLING AND TESTING Delweries will, in general, be sampled and tested by the following methods, but the purchaser reserves the right to use any additional avatlable information to ascertain whether the material meets the specification. 1. SAMPLING Tt is mutually agreed by buyer and seller that a single package out of each lot of not more than 1,000 packages shall be taken as repre- sentative of the whole. Whenever possible an original unopened container shall be sent to the laboratory, and when this is for any reason not done, the inspector shall determine by thorough testing with a paddle or spatula whether the material meets the requirement regarding caking in the container. He shall then thoroughly mix 4 CIRCULAR OF THE BUREAU OF STANDARDS the contents of the container and draw a sample of not less than 5 pounds of the thoroughly mixed paint, place it in a clean, dry metal or glass container, which must be filled with the sample, closed with a tight cover, sealed, marked, and sent to the laboratory for test with the inspector’s report on caking in container. When requested, a duplicate sample may be taken from the same package and delivered to the seller, and the inspector may take a third sample to hold for test in case of dispute. 2. LABORATORY EXAMINATION, SEMIPASTE (a) Canine 1In Contarner.—When an original package is received in the laboratory it shall be weighed, opened, and stirred with a stiff spatula or paddle. The paste must be no more difficult to break up than a normal good grade of semipaste paint. The semipaste shall finally be thoroughly mixed, removed from the container, and the container wiped clean and weighed. This weight subtracted from the weight of the original package gives the net weight of the con- tents. A portion of thoroughly mixed semipaste shall be placed in a clean container and the portions for the Lae tests promptly weighed out. (6) WereutT per Gatton.—From the weight of a known volume of the paste calculate the specific gravity, which multiplied by 8.33 gives the weight in pounds per gallon. Any suitable container of known volume may be used for the purpose, but. a short cylinder of heavy glass with rounded bottom about 75 mm high and having a capacity of from 125 to 175 ce (a glass cap to keep dust from re- agent bottle stopper) is a convenient. vessel, for the purpose. The capacity of this vessel is determined to within 1 cc. The paste is packed into it until completely full, the top leveled off smooth with a spatula, and weighed_to plus or minus 0.5 g. Subtract the weight of the empty container and divide the remainder by the number of cubic centimeters representing the capacity of the container. The quotient is the specific gravity, which can be thus determined within plus or minus 2 in the second decimal place. (c) Mrxine wirn Linszep Orn.—One hundred grams of the paste shall be placed in a cup, 18 ec of linseed oil added slowly with care- ful stirring and mixing with a spatula or paddle. The resulting mixture must be smooth and of good brushing consistency. (qd) Cotor—To the mixture made, in (¢), add 3 ce of drier (F. S. B. No. 20) and mix thoroughly. Prepare a mixture of the standard paste with 18 cc of linseed oil and 3 ce of drier, using the same linseed oil and drier for both lots of paint. Apply both paints on clean metal or glass so that the edges touch one another. Let dry and compare the colors. eee a 2S SPECIFICATION FOR OLIVE DRAB PAINT 5 (¢) Moisrure anp Oruzr Voiatite Marrer.—Weigh accurately from 3 to 5 g of the paste in a tared flat-bottomed dish about 5 cm in diameter, spreading the paste over the bottom. Heat at 105 to 110° C. for one hour, cool, and weigh. Calculate the loss in weight as the percentage of moisture and volatile matter. (7) Prrcenrace or Picmenr.—Weigh accurately about 15 g of the paste in a weighed centrifuge tube. Add 20 to 30 ce of “ex- traction mixture” (see Reagents), mix thoroughly with a glass rod, wash the rod with more of the extraction mixture, and add enough of the reagent to make a total of 60 cc in the tube. Place the tube in the container of a centrifuge, surround with water, and counter- balance the container of the opposite arm with a similar tube or a tube with water. Whirl at a moderate speed until well settled. Decant the clear supernatant liquid, repeat the extraction twice with 40 ce of extraction mixture and once with 40 cc of ether. After drawing off the ether, set the tube in a beaker of water at about 80° C. or on top of a warm oven for 10 minutes, then in an oven at 110 to 115° C. for two hours. Cool, weigh, and calculate the percentage of pigment. Grind the pigment to a fine powder, pass through a No. 80 sieve to remove any skins, and preserve in a stoppered bottle. (g) Preparation or Farry Aciwws.—To about 25 g of the paste in a porcelain casserole, add 15 cc of aqueous sodium hydroxide (see Reagents) and 75 cc of ethyl alcohol, mix and heat uncovered on a steam bath until saponification is complete (about one hour). Add 100 ce of water, boil, add sulphuric acid of specific gravity 1.2 (8 to 10 ce in excess), boil, stir, and transfer to a separatory funnel to which some water has been previously added. Draw off as much as possible of the acid aqueous layer and lead sulphate precipitate, wash once with water, then add 50 cc of water and 50 cc of ether. Shake very gently with a whirling action to dissolve the fatty acids in the ether, but not so violently as to form an emulsion. Draw off the aqueous layer and wash the ether layer with one 15 ce por- tion of water and then with 5 cc portions of water until free from sulphuric acid. Then draw off the water layer completely. Transfer the ether solution to a dry flask and add 25 to 50 g of anhydrous sodium sulphate. Stopper the flask and let stand with occasional shaking at a temperature below 25° C. until the water is completely removed from the ether solution, which will be shown by the solu- tion becoming perfectly clear above the solid sodium sulphate. De- cant this clear solution, if necessary, through, a dry filter paper into a dry 100 cc Erlenmeyer flask. Pass a rapid current of dry air (pass through a CaCl, tower) into the mouth of the Erlenmeyer flask and heat to a temperature below 75° C. on a dry, hot plate until the ether is entirely driven off. 6 CIRCULAR OF THE BUREAU OF STANDARDS It is important to follow all of the details, since ether generally contains alcohol, and after washing with water always contains water. It is very difficult to remove water and alcohol by evapora- tion from fatty acids, but the washing of the ether solution and subsequent drying with anhydrous sodium sulphate removes both water and alcohol. Ether, in the absence of water and alcohol, is easily removed from fatty acids by gentle heat. The fatty acids prepared as above should be kept in a stoppered flask and examined at once. (2) Txsr ror Minera Orn anp OrHer UNSAPONIFIABLE Marrer.— Place 10 drops of the fatty acid, (7), in a 50 ce test. tube, add 5 ce of alcoholic soda (see Reagents), boil vigorously for five minutes, add 40 cc of water, and mix; a clear solution indicates that not more than traces of unsaponifiable matter are present. If the solution is not clear, the oil is not pure linseed oil. (2) Ioptns Numper or Farry Acips.—Place a anit quantity of the fatty acids, (7), in a small weighing burette or beaker. Weigh accurately. ‘Transfer by dropping about 0.15 g (0.10 to 0.20 g) into a 500 cc bottle having a well-ground glass stopper, or an Erlen- meyer flask having a specially flanged neck for the iodine test. Re- weigh the burette or beaker and determine the amount of sample used. Add 10 cc of chloroform. Whirl the bottle to dissolve the sample. Add 10 cc of chloroform to two empty bottles like that used for the sample. Add to each bottle 25 cc of the Hanus solu- tion (see Reagents) and let stand with occasional shaking for one- half hour. Add 10 cc of the 15 per cent potassium iodide solution and 100 ce of water, and titrate with standard sodium thiosulphate, using starch as indicator. The titrations on the two blank tests should agree within 0.1 cc. From the difference between the aver- age of the blank titrations and the titration on the sample and the iodine value of the thiosulphate solution, calculate the iodine number of the sample tested. (Iodine number is centigrams of iodine to 1 g of sample.) If the iodine number is less than 170, the oil does not meet the specification. (7) Coarse Parrictes anp Sxins.—Dry in an oven at 105 to , 110° C. a No. 325 sieve, cool, and weigh accurately. Weigh an amount of semipaste containing 10 g of pigment (see V 2 (7)), add 100 ce of kerosene, mix thoroustily, and wash with kerosene through the sieve, breaking up all lumps, but not grinding. After washing with kerosene until all but the particles too coarse to pass the sieve have been washed through, wash all kerosene from the sieve with ether or petroleum ether, heat the sieve and contents for one hour at 105 to 110° C., cool and weigh. a SPECIFICATION FOR OLIVE DRAB PAINT 7 3. ANALYSIS OF PIGMENT (a) Quarrrarive Anatysis.—A complete qualitative analysis, fol- lowing the well-established methods, is always advisable. Test a portion of the pigment with hydrochloric acid (1: 1). No odor of hydrogen sulphide should develop. Boil, dilute, filter, and test the filtrate for metals other than lead and zinc (especially calcium and barium). The absence of calcium in this filtrate indicates that the extending pigments contain no calcium carbonate or calcium sul- phate; the absence of barium indicates that the extending pigments contain no barium carbonate. To test for chromate, boil another small portion of the pigment. with dilute nitric acid, filter, cool, and add to the filtrate a few cubic centimeters of ether and a few drops of hydrogen peroxide; stir, let stand until the ether layer separates. If this layer is deep blue, chromium is indicated. Test for Prussian blue (which is rarely present) by boiling a portion of the pigment with sodium hydroxide solution. A yellow or yellow-brown precipitate _ with a yellow liquid above it should result. Filter, add to the filtrate a mixture of ferric and ferrous salts, and render acid with dilute hydrochloric acid. A blue color indicates the presence of Prussian blue in the sample. (6) Wuire Leap—Weigh accurately about 1 ¢ of the pigment, transfer to a 250 cc beaker, moisten with a few drops of alcohol, add slowly 25 cc of concentrated hydrochloric acid, cover, and boil for 5 to 10 minutes. Dilute to about 150 cc with hot water and boil for 5 to 10 minutes. Filter on paper or on a Gooch crucible, and wash the insoluble residue thoroughly with hot water. Discard the residue for quantitative purposes. Nearly neutralize with ammonia the filtrate from the insoluble matter, dilute to about 300 ce and pass into the clear solution a rapid current of hydrogen sulphide to com- plete precipitation, let the sulphide of lead settle, filter on paper, wash with water containing some hydrogen sulphide, dissolve the sulphide in hot nitric acid (1:3), add 10 cc of sulphuric acid (1:1), evaporate until copious fumes of sulphuric anhydride are evolved; cool, add about 75 ce of water, and then about 75 cc of 95 per cent ethyl alcohol. Stir, let settle, filter on a Gooch crucible, wash with dilute alcohol, dry, ignite, and weigh as PbSO,: Subtract the lead sulphate equivalent of the total cromium as found below, (c), multiply the remaining PbSO, by the factor 0.883 and report as white lead. (c) Toran Curomrum.—Heat the filtrate from the lead sulphide to expel hydrogen sulphide. Cool, add sodium peroxide, keeping the beaker covered, in sufficient amount to render the solution alkaline and to oxidize the chromium to chromate. Boil until all the hydro- gen peroxide is driven off, cool, acidify with sulphuric acid (1:4), add a measured excess of a freshly prepared solution of ferrous sul- 8 CIRCULAR OF THE BUREAU OF STANDARDS phate, and titrate the excess of ferrous iron with standard potassium dichromate, using potassium ferricyanide solution as outside indica- tor. Titrate a blank of an equal volume of the ferrous sulphate solu- tion with the standard potassium dichromate. From the difference between the titration on the blank and on the sample, calculate the chromium in the sample to PbCrO,. From the PbCrO, found, cal- culate the equivalent of PbSO, by multiplying by the factor 0.938. (d) Zinc Oxwwn.—Weigh accurately about 1 g of the pigment, transfer to a 250 cc beaker, moisten with alcohol, add 30 ec of hydrochloric acid (1:2), boil for two or three minutes, add about 100 cc of water, let settle, and filter on paper; to the filtrate add about 2 g of ammonium chloride and strong ammonia until slightly alkaline (the latter to precipitate out any iron present), set on the steam bath to settle, filter into a 400 ce beaker, wash the precipitate once with water, remove the beaker and dissolve the.iron hydroxide with dilute hydrochloric acid, catching the ferric chloride in a 250 cc beaker, add to this filtrate 1 g of ammonium chloride and make ammoniacal, let settle, filter and wash thoroughly with hot water, catching the filtrate and washings in the original 400 ec beaker, reserved from the first precipitation. Add a small piece of litmus paper. Render the filtrate first acid with hydrochloric acid, then add 3 ce of strong hydrochloric acid, heat nearly to boiling, and titrate with standard ferrocyanide, as in standardizing that solution (see Reagents). Calculate total zinc as zine oxide. (ec) Orcanio Cotortne Marrer—(A. S. 7. M. Standards, 1921, p. 690).—Test the pigment successively with hot water, 95 per cent alcohol, alcoholic sodium hydroxide, and acetic acid. Chloroform, sodium hydroxide, sulphuric acid, hydrochloric acid-stannous chloride solution, and other reagents may be tried. The solutions should remain colorless. The presence of an organic color may often be detected by the characteristic odor given off on ignition. (f) Catcutations.—Add the percentage of white lead (see V 3 (b)), zine oxide (see V 3 (d)), and subtract from 100; the remainder is reported as extending and tinting pigments. 4. LABORATORY EXAMINATION, READY-MIXED PAINT (a2) Caxine in Conratner.—Follow the procedure outlined in V 2 (a), noting that the paint should be no more difficult to break up than a good grade of mixed paint. (6) Weitcutr per Gatton.—Weigh a clean, dry, 100 cc diva dilibded flask. Fill to the mark with the thoroughly mixed paint and weigh again. The increase in weight expressed in grams divided by 100 gives the specific gravity, which multiplied by 8.33 gives the weight in pounds per gallon. . SPECIFICATION FOR OLIVE DRAB PAINT 9 (¢) Brusaine Proprrrms ano Time or Drytne.—Brush this well-mixed paint on a suitable panel, which may be ground glass, steel, or well-filled wood. Note whether the paint works satis- factorily under the brush. Place the panel in a vertical position in a well-ventilated room and let stand for 18 hours. The paint should be dry and free from streaks. Flow a portion of the paint on a clean glass plate. Let dry ina nearly vertical position at room temperature (65 to 100° F.). The film shall show no streaking or separation within a distance of 4 inches from the top. (zd) Cotor—Paint the sample and the standard on clean metal or glass so that the edges touch one another. Let dry and compare colors. _ (e) Warrr.—Mix 100 g of the paint in a 300 cc flask with 7 ce of toluol. Connect with a condenser and distill until about ©0 ce of distillate has been collected in a graduate. The tem- perature in the flask should be then about 105 to 110° CG. The number of cubic centimeters of water collecting under the toluol in the receiver is the percentage of water in the paint. (7) Voratie Turnner.—Follow the procedure outlined in V 2 (e). Correct the result for any water found (see V 2 (e)) and re- port the remainder as volatile thinner. (g) Prercenrace or Pigment.—Follow the procedure outlined in Woe. (fs : (h) Testinc Nonvorarme Ventcrz.—Follow the procedure out- lined in V 2 (g), (2), and (¢), except that in the preparation of the fatty acids the mixture of paint and alkali is heated on the steam bath until all volatile thinner is driven off. (7) Coarse Particres anv Sxins,—Follow the procedure outlined in V 2 (4). (j) Txstrine Piement.—Follow the procedure outlined in V 3 (a) to (f), inclusive. 5. REAGENTS (a) Uranyn Inpicator ror Zino Trrrarion.—A 5 per cent solu- tion of uranyl nitrate in water or a 5 per cent solution of uranyl acetate in water made slightly acid with acetic acid. (0) Sranparp Porassrum Frrrocyanmpr.—Dissolve 22 g of the pure salt in water and dilute to 1,000 cc. To standardize transfer about 0.2 g (accurately weighed) of pure metallic zinc or freshly - ignited pure zinc oxide to a 400 cc beaker. Dissolve in 10 ce of hydrochloric acid and 20 cc of water. Drop in a small piece of litmus paper, add ammonium hydroxide until slightly alkaline, then add hydrochloric acid until just acid, and then 8 cc of strong hydrochloric acid. Dilute to about 250 cc with hot water and heat nearly to boiling. Run in the ferrocyanide solution slowly from 10 CIRCULAR OF THE BUREAU OF STANDARDS a burette with constant stirring until a drop tested on a white porcelain plate with a drop of the uranyl indicator shows a brown tinge after standing one minute. A blank should be run with the ‘game amounts of reagents and water as in the standardization and in titration of the ue The standardization must be made under the same conditions of temperature, volume, and acidity as obtained when the sample is titrated. (c) Sranparpv Soprum TuiosuteHate Sorurion.—Dissolve pure sodium thiosulphate in distilled water (that has been well boiled to free it from carbon dioxide) in the proportion of 24.83 g of crystal- lized sodium thiosulphate to 1,000 ce of the solution. It is best to let this solution stand for Pycat two weeks before standardizing. Standardize with pure resublimed iodine. (See Treadwell-Hall, Analytical Chemistry, vol. 2, 3d ed., p. 646.) This solution will be approximately decinormal, dad it is best to leave it as it is after determining its exact iodine value, rather than to attempt to adjust — it to exactly decinormal. Preserve in a stock bottle provided with a guard tube filled with soda lime. (2) Srarcu Sorurion.—Stir up 2 to 3 g of potato starch or 5 g of soluble starch with 100 cc of 1 per cent salicylic acid solution, add 300 to 400 cc of boiling water, and boil the mixture until the starch is practically dissolved, then dilute to 1 liter. (e) Exrracrion Mixrurn.— 10 volumes ether (ethyl ether). 6 volumes benzol. 4 volumes methy] alcohol. 1 volume acetone. (f) Aqueous Soprum Hyproxipr.—Dissolve 100 g of sodium hy- droxide in distilled water and dilute to 300 ce. (g) Porasstum Iopme Sorurion.—Dissolve 150 g of potassium iodide free from iodate in distilled water and dilute to 1,000 ce. (hk) Hanus Soturion.—Dissolve 13.2 g of iodine in 1,000 cc of 99.5 per cent glacial acetic acid, which will not reduce ehyreanie acid. Add enough bromine to aouble the halogen content, deter- - mined by titration (3 cc of bromine is about the proper amount). The iodine may be dissolved by the aid of heat, but the solution should be cold when the bromine is added. (2) Axconotic Soprom Hyproxipr Soiurion.—Dissolve pure sodium hydroxide in 95 per cent ethyl alcohol in the proportion of about 22 g per 1,000 cc. Let stand in a stoppered bottle. Decant the clear liquid into another bottle and keep well stoppered. This solution should be colorless or only slightly yellow when used, — and it will keep colorless longer if the alcohol is previously treated with sodium hydroxide (about 80 g to 1,000 cc), kept at about 50° C. for 15 days, and then distilled. SPECIFICATION FOR OLIVE DRAB PAINT Md bs (j) Stanparp Frrrous Suneware Sonvurion.—Dissolve 14 g of pure crystallized ferrous sulphate (FeSO,7H,O) in about 500 cc of water to which 25 cc of concentrated H,SO, has been added, and then dilute to 1,000 cc. This solution should be freshly stand- ardized when needed, as it does not keep well. (4) Sranparp Porasstum Dicuromate Soxvurion.—Dissolve 4.903 g of pure, dry, crystallized potassium dichromate in water and dilute to 1,000 cc. One cubic centimeter of this solution corre- sponds to 0.0108 g PbCrO,, or 0.0101 g PbSO,. This solution may be checked by determining its iron value on Bureau of Standards Standard Sample No. 27a, Sibley Iron Ore. (¢) Porasstum Ferrricyanwe Sorurion.—Dissolve a piece of potassium ferricyanide half as big as a small pea in 50 cc of water. This solution must be made fresh when wanted, because it does not keep. VI. PACKING AND MARKING No details. VII. ADDITIONAL INFORMATION This specification covers the requirements for a high-grade olive drab paint for outside and general. use. It may be ordered either in the form of semipaste pigment ground in linseed oil or of ready- mixed paint, and the purchaser shall state which is desired. The semipaste shall be purchased by net weight, and the ready- mixed paint either by weight or volume (231 cubic inches to the gallon). VIII. GENERAL SPECIFICATIONS No details. ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, D. C. AT 5 CENTS PER COPY V / 4 ‘ . *) Ps : ? ; ‘ ‘ i , ‘te Date Due LIBRARY BUREAU FORM 1137.3 [4s Fe ‘eke GETTY CENTER LIB RY | {| \ | WN] "3125 00017 emi \ a a Wy | | | aH am gna ate SS — lame! Sree ee — = as ——— : a ee