■'! ., LABORATORY MANUAL OF AGRICULTURAL CHEMISTRY HEDGES AND BRYANT ;i 1 Class LA Book.. ^ 6^ / 7V CDPYPIGriT DEPOSm .„.^.^*^^*r>. PROFESSOK S. W. JOHNSON LABORATORY MANUAL OF AGRICULTURAL CHEMISTRY BY CHARLES CLEVELAND HEDGES, Ph.D. PROFESSOR OF AGRICULTURAL CHEMISTRY AND HEAD OF THE DEPARTMENT OF CHEMISTRY AND CHE3IICAL ENGINEERING TEXAS AGRICULTURAL AND MECHANICAL COLLEGE AND WILLIAM THOREAU BRYANT, B.S., Ch.E. INSTRUCTOR IN AGRICULTURAL CHEMISTRY TEXAS AGRICULTURAL AND MECHANICAL COLLEGE GINN AND COMPANY BOSTON • NEW YORK • CHICAGO • LONDON ATLANTA • DALLAS • COLUMBUS • SAN FRANCISCO COPYRIGHT, 1916, BY CHARLES CLEVELAND HEDGES AND WILLIAM THOREAU BRYANT ALL RIGHTS RESERVED 516.8 GINN AND COMPANY • PRO- PRIETORS • BOSTON • U.S.A. ©CI,A438;i74 PREFACE This Laboratory Manual is the outgrowth of several years' experience in agricultural institutions in teaching chemistry in its various relations to agriculture. The direc- tions are designed as a laboratory guide for students in agricultural chemistry. It is necessary that this course be preceded by a course in general or inorganic chemistry and accompanied by a course in the theory of agricultural chemistry. A course in quantitative analysis is not neces- sarily a prerequisite. At the beginning of the Manual, along with the preparation of standard solutions used later in the analysis of agricultural products, a few experiments in quantitative analysis have been given to illustrate the fundamental principles and more important methods of manipulation. Directions as to the setting up of apparatus, details of manipulation, use and care of the balance, chem- istry, and stoichiometry should be given in lectures accom- panying the laboratory practice. The authors did not consider it advisable to burden the laboratory guide with a large amount of explanatory notes giving reasons for each step in the directions. It was thought that this could be accomplished to better advantage by means of lectures accompanying the laboratory work, and by questions at the end of each experiment that are designed to encourage the student to think for himself and to do outside reading. This arrangement gives the teacher an opportunity to [V] present the theory in any particular manner he may desire and to come in closer contact with the students, thereby making the practice more interesting to them by the personal contact. The directions for each experiment are simplified, as far as it is considered advisable, in order that the student might be able to pursue the laboratory work with the least possible assistance from the teacher. In the Appendix is given a list of some of the most important works bearing on this subject so as to further the interest of the student by encouraging outside reading. In preparing this Manual free use has been made of standard works on quantitative analysis, of the publica- tions of the Association of Official Agricultural Chemists, and of the bulletins of the Bureau of Chemistry, United States Department of Agriculture. The authors desire to acknowledge their obligation to the " Letter-Files " and to the Yale University Press for the portrait of Professor S. W. Johnson used as the frontispiece. C. C. HEDGES College Station, Texas W. T. BRYANT [vi] CONTENTS PART I. PREPARATORY QUANTITATIVE ANALYSIS Experiment page Introduction 1 1. Preparation of Cleaning Mixture 2 2. Preparation of an Approximate N/10 NaOH Solution . . 3 3. Preparation of an Approximate N/5 HCl Solution ... 3 4. Determination of Equivalent Volumes 4 5. I. Preparation of a Perforated or Goocli Crucible ... 6 II. Standardization of HCl Solution by Gravimetric Method 8 6. I. Standardization of the HCl Solution by Volumetric Method 10 II. Calculation of the Titre of the NaOH Solution ... 12 7. Determination of the Strength of an Unknown Alkali Solution 12 8. Determination of the Strength of an Unknown Acid Solution 13 9. Determination of the Strength of an Unknown KgCOg Solu- tion, using Methyl Orange as Indicator 13 10. Determination of the Strength of an Unknown 1^2^03 Solu- tion, using Phenolphthalein as Indicator 13 11. Determination of the Strength of an Unknown NaOH and Na^COg Solution 14 12. Determination of Acetic Acid in Vinegar 15 13. Determination of Total Solids in Vinegar , 16 14. Determination of Ash in Vinegar 16 15. Preparation of Standard Potassium Permanganate Solution (KMnO^) 17 16. Determination of the Amount of Calcium Oxide in Limestone 18 [vii] PART II. ANALYSIS OF FEEDSTUFFS EXPERIMENT PAGE Preparation of a Sample of Feedstuff for Analysis ... 21 17. Determination of Moisture in Feedstuffs 21 18. Determination of Ash in Feedstuffs 22 19. Determination of Crude Protein in Feedstuffs .... 23 20. Determination of Ether Extract (Fat) in Feedstuffs . . 26 21. Preparation of a 1.25 Per Cent HgSO^ Solution and a 1.25 Per Cent NaOH Solution 28 22. Determination of Crude Fiber in Feedstuffs 29 23. Determination of Nitrogen-Free Extract in Feedstuffs . . 30 PART III. CHEMICAL ANALYSIS OF SOIL Directions for taking a Sample of Soil for Analysis ... 32 Preparation of Samples for Analysis 33 24. Qualitative Analysis of Soil 34 25. Determination of Moisture in Soil 35 26. Determination of Volatile Matter in Soil 36 27. Determination of Humus in Soil 36 28. Determination of Nitrogen in Soil (Nitrates Absent) . . 37 29. Test for Acidity or Alkalinity of Soil and Determination of Lime Requirements 38 30. Strong Hydrochloric Acid (sp. gr. 1.115) Digestion of Soil. Preparation of Soil Solution 39 31. Determination of Iron (Fe) in Soil Solution by Volumetric Method 41 32. Determination of Calcium (Ca) in Soil Solution by Volu- metric Method 42 33. Determination of Phosphoric Acid (P2^5) ^^ ^^^^ Solution by Gravimetric Method 43 33 a. Determination of Phosphoric Acid (Pa^s) ^^ Soil Solution by Volumetric Method (Optional Method) .... 45 34. Determination of Potash (KgO) in Soil Solution by the Use of Platinum Solution 47 34 a. Determination of Potash (KgO) in Soil Solution by Volumetric Method (Optional Method) 49 34 h. Determination of Potash (K2O) in Soil Solution by the Use of Platinum Solution (Moore's Method modified) (Optional Method) 52 [ viii ] PART IV. ANALYSIS OF FERTILIZERS EXPERIMENT PAGE Preparation of Sample of Fertilizer for Analysis .... 55 35. Determination of Moisture in Fertilizer 55 36. Preparation of a Standard NaOH Solution for Phosphoric Acid (P2^5) Determination 56 37. Determination of Total Phosphoric Acid (PgOg) in Fertilizer 57 38. Determination of Water-Soluble Phosphoric Acid (Pg^s) i^ Fertilizer 59 39. Determination of Citrate-Soluble Phosphoric Acid (P0O5) in Fertilizer 59 40. Determination of Potash (K2O) in a Mixed Fertilizer by the use of Platinum Solution 61 40 a. Determination of Potash (K2O) in a Mixed Fertilizer by Volumetric Method (Optional Method) 62 41. Determination of Nitrogen in Fertilizers (Nitrates Present) 63 PART V. ANALYSIS OF INSECTICIDE AND FUNGICIDE 42. Preparation and Standardization of Solution for Determi- nation of Arsenious Oxide (AsgOg) in Paris Green . 64 43. Determination of Total Arsenious Oxide (AsgOg) in Paris Green 65 44. Determination of Water-Soluble Arsenious Oxide (AS2O3) in Paris Green 66 45. Determination of Moisture in Lead Arsenate 67 46. Determination of Total Lead Oxide in Lead Arsenate . . 67 47. Determination of AVater-Soluble Lead Oxide in Lead Arsenate 68 48. Determination of Total Arsenic Oxide (AS2O5) in Lead Arsenate 69 49. Determination of Water-Soluble Arsenic Oxide (AS2O5) in Lead Arsenate 70 50. Testing Bordeaux Mixture for Soluble Copper 70 PART VI. ANALYSIS OF MILK 51. Determination of Specific Gravity of Milk 72 52. Determination of Total Solids in Milk 73 53. Determination of Ash in Milk 73 [ix] EXPERIMENT PAGE 54. Determination of Fat in Milk by the Werner-Schmidt Method 74 55. Determination of Total Protein (Casein and Albumin) in Milk 75 56. Determination of Casein in Milk 75 PART VII. A BRIEF SANITARY EXAMINATION OF WATER 57. Determination of Total Solids in Water 77 58. Determination of Chlorine as Chlorides in Water .... 77 59. Detection of Free Ammonia in Water 78 60. Detection of Nitrites in Water 79 61. Detection of Nitrates in Water 79 62. Determination of Absorbed Oxygen in Water 80 63. Determination of Temporary Hardness or Alkalinity of Water 80 PART VIII. APPENDIX Books of Reference 82 Tables of Weights 83 Tables of Measm-es 84 Strength of HCl Solution at Different Densities, 15° C. . . . 85 Strength of H2SO4 Solution at Different Densities, 15° C. . . 80 Strength of HNO3 Solution at Different Densities, 15° C. . . 86 Strength of NH^OH Solution at Different Densities, 15° C. . . 86 Strength of NaOH Solution at Different Densities, 15° C. . . 87 Rules to determine Solubilities in Water 88 Directions for Preparation of Reagents 88 Apparatus for Desk Equipment 93 International Atomic Weights (1916) 94 [^] LABORATORY MANUAL OF AGRICULTURAL CHEMISTRY LABORATORY MANUAL OF AGRICULTURAL CHEMISTRY PART I PREPARATORY QUANTITATIVE ANALYSIS Introduction At the first laboratory period the student should check up the apparatus in the desk assigned to him and imme- diately report any shortage or broken apparatus to the instructor in charge. Each student should be required to turn in at the end of the term's work a desk fully equipped with a complete set of apparatus in perfect condition. He should also be required to make a wash bottle to be used m the analytical work, and have it inspected by the in- structor. All records of the laboratory work should be recorded in a notebook in a neat and systematic manner. Reports of experiments and answers to all questions should be submitted at the next period, after the experi- ment is completed. Cleanliness, neatness, patience, and the most careful attention to details of the directions cannot be overemphasized in laboratory manipulations. [1] Experiment No. 1 PREPARATION OF CLEANING MIXTURE Dissolve 20 g. of commercial KJ^vfi^ in 75 cc. of warm water, cool, and pour slowly into it, with constant stirring, 115 cc. of commercial sulphuric acid (H^SO^). The potas- sium dichromate solution should be placed in a No. 7 evap- orating dish, if convenient, before pouring the sulphuric acid into it. When the solution is completely cooled, it should be transferred to a 250 cc. wide-mouthed bottle. (Be careful in making this mixture, so as not to spill it on your clothes.) Invert the burettes in the cleaning mix- ture, attach the rubber tubing, draw up to the 50 cc. mark, and allow to stand for at least half an hour before being used. (^See that the burette stopcocks work smoothly and are not clogged ivith grease.) Coat the burette stopcocks with a very small amount of vaseline to prevent sticking. The cleaning mixture is to be used throughout the course. Avoid the addition of water to the cleaning mixture. A burette is clean when the drops of water will not adhere to the sides. Other useful cleaning mixtures are soap solutions, alcoholic KOH solutions, and ammoniacal alcohol solutions. Chemistry K,Crp^ + 2 H^SO^ = 2 KHSO^ + H^Cr^^. H^Cr^^ breaks up into H^CrO^ + Cr03 (red ppt). 2 H^CrO^ = Cr^O^ + 2 Hp + 3 O. 2Cr03 = CrP3 + 3 0. Both H^CrO^ and CrO^ oxidize organic matter. Ci-p^ + 8 H^SO, = Cr, (SO,)3 + 3 H^O. [2] Questions 1. AVhy does cleaning mixture clean ? 2. Write equation. 3. What would you use to clean grease from glassware ? Give reason. 4. After using the mixture for some time, it may become green in color. Give reason. 5. What is meant by the terms comfimercial and C. P. cheynicals ? Experiment No. 2 PREPARATION OF AN APPROXIMATE N/10 NaOH SOLUTION A normal solution is one which contains the hydrogen equivalent of the active constituent in grams per liter ; that is, the amount in a liter which brings into reaction 1.008 g. of hydrogen or 8 g. of oxygen, or their equivalent. One molecule of NaOH brings into reaction one atom of hydrogen when it reacts with an acid. Therefore 40.058 g. of NaOH is equivalent to 1.008 g. of hydrogen ; hence there are 40.058 g. of NaOH in one liter of normal NaOH solution, and 4.0058 g. in one liter of a N/10 NaOH solution. Since the NaOH "sticks" contain about 10 to 20 per cent of water, weigh out (on rough balance) 5 g., dissolve in distilled water, and dilute to one liter. Shake the solution thoroughly. Experiment No. 3 PREPARATION OF AN APPROXIMATE N/6 HCl SOLUTION One molecule of hydrochloric acid (HCl) contains one replaceable hydrogen atom; therefore 36.458 g. of hydrogen chloride furnishes 1.008 g. of reacting hydrogen. In other words, the molecular weight of HCl (36.458) contains [3] 1.008 parts of reacting or replaceable hydrogen. Therefore it requires 36.458 g. of hydrogen chloride (HCl) for one liter of a normal hydrochloric acid (HCl) solution, and 7.2916 g. for one liter of a N/5 hydrochloric acid (HCl) solution. The specific gravity of the C. P. concentrated hydro- chloric acid solution on the reagent shelf should be determined by means of a specific-gravity spindle or hydrometer. Example. Should the specific gravity of the C. P. concentrated hydrochloric acid solution on the reagent shelf be 1.175, it would contain 34.43 per cent of hydrogen chloride by M-eight (see table of specific gravities, p. 85). Therefore 1.175 times .3443 = grams of hydrogen chloride in 1 cc. of the C. P. concentrated hydrochloric 7 '^916 acid solution, and ^ ^^J" — — -— = 18 cc. of C. P. concentrated hydro- 1.17o X .3443 ^ chloric acid required to furnish approximately 7.2916 g. of hydro- gen chloride. This is the weight or amount of hydrogen chloride required for one liter of a N/5 hydrochloric acid solution, providing the concentrated acid is of the above specific gravity. Measure out the amount of the concentrated C. P. hy- drochloric acid required by your calculations (in the above example it would be 18 cc.) and dilute to one liter with distilled water. Shake the solution thoroughly before usmg. Experiment No. 4 DETERMINATION OF EQUIVALENT VOLUMES Rinse out two burettes (which have been standing in cleaning mixture) with distilled water. After each burette is rinsed with distilled water, it should be rinsed again with a 5 cc. portion of the solution to be used in the respective burette, so as to remove any adhering particles [4] of water (letting the solution run through the tip each time). Label the burette according to the solution to be used therein. Fill one of the burettes * a little above the zero mark with the approximate N/10 NaOH solution. Open the stopcock or pinchcock cautiously until the read- ing of solution in the burette is zero. In the same manner fill the other burette with the approximate N/5 HCl solu- tion, using the same care as to washing, etc. Draw out approximately 10 cc. of the NaOH solution into a 250 cc. Erlenmeyer flask or beaker. Dilute to 50 cc. with distilled water, add one drop of methyl orange, and then rapidly add the HCl solution until the solution in the flask or beaker changes color, indicating an acid solution. Now bring the flask or beaker under the burette containing the NaOH, and add the NaOH solution more slowly, until the color turns yellow. Then bring the flask or beaker under the burette containing the HCl, and add the HCl solution slowly until the solution turns red. Continue this opera- tion until a point is obtained where one drop, or even half a drop, of either solution will cause a color change. When this point — known as the end-point — is reached, allow the solutions in the burettes to dram for a minute, and then read the exact volume of each solution used. Record in your laboratory notebook the exact volume of solution used. As a check on this determination and also as work with indicators, make titrations, using phenol- phthalein, cochineal, and methyl red as indicators. Make at least two titrations with each indicator. Different determinations should agree within .05 cc. Take the aver- age of the titration for the calculations. From the data * It is advisable to use a rubber-tipped burette for the alkali solution. [5] obtained calculate and report the cubic centimeters of HCl solution neutralized by 1 cc. of the NaOH solution. Also calculate and report the cubic centimeters of NaOH solution neutralized by 1 cc. of the HCl solution. Questions 1. How many grams of the following reagents will be required for one liter of a normal solution ; one liter of fifth-normal solution : HNO3, H,SO^, HgPO^, H.^C^O^, 2 H^O, NH^H, NaHCOg, AgN03, K,SO^ ? 2. How many cubic cen- timeters (cc.) of N/10 HCl = 15cc. of N/1 NHpH? N/5 K2CO3? N/10 NaOH? N/1 KOH=:10cc.? N/4 H.C.p^? N/2 H.^SO^? 3. If 8g. of a sample containing some NaOH were dissolved in 200 cc. of distilled water, and 20 cc. of this solu- tion were equivalent to 15 cc. of a N/5 acid, what would be the percentage of NaOH in the original material ? Experiment No. 5 I. PREPARATION OF A PERFORATED OR GOOCH CRUCIBLE Prepare two crucibles in the following manner: Place the Gooch funnel in the neck of a filter flask by means of the rubber stopper, stretch the rubber band over the funnel, and place the crucible in the opening. Con- nect the filter flask, by means of a rubber tubing, to the filter pump, and before turning on the suction pour into the crucible some of the coarse, suspended asbestos* (obtained by shaking the bottle). When the water has filtered through, turn on the suction and pour on some of the finer asbestos (supernatant liquid obtained on allow- ing the solution to settle a short time). Tap well with flattened glass rod, and add another layer. Then wash * Prepared according to directions on page 88. [6] with at least 100 cc. of distilled water, and dry in the air bath at 130°-150° C. for two hours. Cool m desiccator, and weigh accurately to tenths of a milligram. (Crucibles ANALYTICAL BALANCE should be handled only with clean forceps.) The asbestos film should be thin enough to be translucent when wet, but not so thin that it will be liable to permit a fine precipitate to pass through. [7] Do not put any labels on the crucibles, and do not mark them. They may be identified by placing them in a labeled funnel.* The crucibles should be treated in the same way before and after receivmg the precipitates. This applies to the length of time in the drying oven, the heat applied, and the length of time they stand in the desiccator before weighmg. Questions 1. What is asbestos, and how is it obtained ? 2. How should asbestos be prepared for use in a Gooch crucible ? 3. In Experiment No. 5, why not filter through a filter paper? 4. Give three precautions that should be taken when using a desiccator. 5. Name four reagents that could be used in a desiccator, for drying purposes, and discuss their efficiency. II. STANDARDIZATION OF HCl SOLUTION BY GKAVIMETRIC METHOD Into two 250 cc. Erlenmeyer flasks, which have been cleaned with cleaning mixture and carefully rinsed with distilled water, measure out accurately from a burette 25 cc. portions of HCl solution. (Allow the burette to drain for about five minutes before reading.) Add 75 cc. of distilled water, 5 cc. of C. P. cencentrated HNO^ solu- tion, and then a solution of silver nitrate t (AgNOg) very gradually and with constant agitation of solution until the precipitation is complete. Close the flask with a clean rubber stopper, wrap in a black cloth, and shake the flask vigorously for several minutes until the AgCl * Crucibles may be permanently marked for identification either with China paints by Yoder's method (circular of Bureau of Chemistry) or, more conveniently, by burning in a '^ grease " Prussian blue pencil mark. J. E. Huber, Chemist Analyst, January, 1915, p. 25. i Prepared according to directions on page 89. [8] is flocculated and the supernatant liquid is perfectly clear. When the precipitation is complete, the supernatant liquid quickly becomes clear. To this clear portion a drop of silver nitrate may be added to decide whether enough has been added for complete precipitation of the hydro- chloric acid. Avoid the addition of an excess of the silver solution. It is necessary to protect the flask con- taining the precipitate from the light, as much as possible, as light tends to decompose the silver chloride precipitate (AgCl). Let the precipitate settle, then filter off the supernatant liquid through the tared Gooch crucible by suction, intro- ducing as little of the precipitate as possible on the filter. Wash with about 150 cc. of a cold 1 per cent HNO^ solution by similar decantation through the Gooch. Transfer the precipitate, without loss, from the flask to the tared cruci- ble, with about 100 cc. more of a 1 per cent HNO^ solu- tion, making sure that none is left in the flask or on the rubber stopper, and wash thoroughly with a 1 per cent HNOg solution until 15 cc. of the filtrate does not give a test for silver nitrate (AgNO^). Suck fairly dry. Dry the crucible and contents for two hours at 130°-150° C, cool in desiccator, and weigh. Heat again for one hour, cool, and reweigh. Repeat until weight is constant. Duplicates must not differ in weight more than 1 mg. At least four trials should be made. Chemistry AgNOg + HCl = AgCl -h HNO3 Mol. wt. of AgCl : mol. wt. of HCl : : weight of ppt. : x X = grams of hydrogen chloride (HCl) in number of cubic centimeters of hydrochloric acid solution used. [9] = p-rams of hydrog^en chloride Volume of HCl used "" ^ ^ (HCl) in 1 cc. of the hydrochloric acid solution, which is known as the titre of that solution. Questions 1. Show how to make a N/10 HCl solution, a N/5 H^SO^ solution, a N/10 HNO3 solution, a N/20 NaOH solution, using HCl, sp. gr. 1.185 ; H^SO^, sp. gr. 1.8 ; HNO3, sp. gr. 1.4 ; NaOH, containing 20 per cent of water. 2. What is the percentage of Ag in AgCl ? Fe in FeS0^(NHj2S0^ • 6Hp? S in BaSO^ ? and CaO in CaCOg ? 3. How many cubic centi- meters of HCl (sp. gr. 1.2) are necessary to precipitate com- pletely the silver in 2 g. of AgNO^ ? 4. How many cubic centimeters of N/10 AgNOg solution will be necessary to precipitate the chlorine from .12 g. of CaCl^ ? 5. What effect has light upon AgCl ? Explain. Experiment No. 6 I. STANDARDIZATION OF THE HCl SOLUTION BY VOLU- METRIC METHOD Weigh out accurately 0.2 to 0.3 g. portions of C. P. Na^COg into 250 cc. Erlenmeyer flasks or beakers, and dissolve each portion in 50 cc. of distilled water. Add one drop of methyl orange to one portion, and titrate with HCl solution until the first tmge of pink appears. Repeat the operation with the second portion. Record accurately the burette readings. Chemistry and Calculations Na^Og + 2 HCl = 2 NaCl + Hp -f CO, Mol. wt. of Na^COg : mol. wt. of 2 HCl : : wt. of Na^Og : x 106.1 : 72.916 : : weight of Na^CO^ taken : x [10] — = grams of hydrogen chloride Volume of HCl used (HCl) in 1 cc. of the hydrochloric acid solution, which is known as the titre of that solution. If the duplicates APPARATUS FOR QUANTITATIVE ANALYSIS i, Erlenmeyer flask (500 cc.) ; ^, wash bottle ; 5, measuring flasks (500 and 1000 cc.) ; 4, burettes and burette holder ; 5, desiccator ; ^ iii the soil soluble in the acid solution. Question Give the reason for each step in the determination and write equations illustrating the reactions. [46] Experiment No. 34 DETERMINATION OF POTASH (KgO) IN SOIL SOLUTION BY THE USE OF PLATINUM SOLUTION* Measure out, with a burette or pipette, two 100 cc. portions of Solution A, place in beakers, heat nearly to boiling, and add NH^OH, dy^o]? hy drop, until the solu- tion is strongly alkaline. Cover the beaker and boil the solution for about one minute ; if no ammonia is given off (detect by smelling), more is added, droij hy drop^ until it can be detected. Do not allow the precipitate to settle, but stir and filter immediately while hot, washing it thoroughly with liot water. Evaporate the filtrate and washings to complete dryness, heat below redness to expel ammonium salts, dissolve in about 25 cc. of hot water, add about 5 cc. of saturated barium hydroxide, and heat to boiling. Let the solution stand until the precipitate set- tles, and test the supernatant liquid with a drop of barium hydroxide solution to be sure that precipitation is com- plete. When the precipitation is complete, filter and wash the residue thoroughly with hot water. AYhile the solution is boiling add ammonium hydroxide and ammonium car- bonate to precipitate the barium. Allow the solution to stand for a short time on a water bath, filter, wash the pre- cipitate thoroughly with hot water, and evaporate filtrate and washings to dryness. Expel the ammonium salts by heating at a low red heat as before, dissolve the residue in about 20 cc. of water, add about 2 cc. of ammonium * If desired, potash can be determined by optional methods (Exps. Nos. 34 a, 34&). [47] •5-: hydroxide and a drop of ammonium carbonate solution, let stand on a water bath for a few minutes, and filter into an evaporating dish. Evaporate filtrate and washings nearly to dryness, add 1 cc. of dilute H^SO^ (1 : 1), evap- orate to dryness, and ignite to whiteness. As all the potassium is in the form of sulphate, no loss need be apprehended by volatilization of potash, and a full red heat must be mamtained until the residue is perfectly white. Dissolve the residue in about 15 cc. of water, add a few drops of hydrochloric acid, and platinum solution (H^PtClg) * in slight excess (avoid the use of too large an excess, as the reagent is very expensive). Evaporate on a water bath to a thick paste, and treat the residue with 80 per cent alcohol (sp. gr. 0.8645). If enough platinum solution has been added to precipitate all the potassium, the alcoholic solution will be slightly colored. If the alco- hol is not slightly colored, it must be evaporated off, the precipitate redissolved in water containing a few drops of HCl, more platinum solution added, and again evaporated to a thick paste and treated with alcoliol as before. If the alcoholic solution is not colored, owmg to an excess of platinum solution, do not add more platinum solution directly to the alcoholic solution, but evaporate off the alcohol first. Also avoid the absorption of ammonia by the solution. After the precipitate is treated with the 80 per cent alcohol, filter into a properly prepared and iveighed Gooch crucible, wash thoroughly with 80 per cent alcohol, then with 10 cc. of the special ammonium chloride solu- tion t to remove impurities. Repeat washing with the special ammonium chloride solution about five times, and * Prepared according to directions on page 90. t Prepared according to directions on page 90. [48] again wash thoroughly with 80 per cent alcohol. Dry the precipitate for thirty minutes at the temperature of boil- ing water, cool in desiccator, and weigh. The precipitate is potassium platinic chloride (K^PtClJ, and should be per- fectly soluble in water (which gives a means of checking the results if desired). For the conversion of potassium platinic chloride to potassium oxide (}^fi^ use the factor 0.1941. Calculate and report the percentage of potash (K^O) in the soil soluble in the acid solution. (Save all filtrates and potassium platinic chloride precipitates so as to recover the platinum.) Questions 1. How is the factor 0.1941 obtained ? 2. Write equations illustrating each step in the determination. Experiment No. 34 a (Optional Method) DETEKMINATION OF POTASH (K.fi) IN SOIL SOLUTION BY VOLUMETllIC METHOD * Measure out, with a burette or pipette, two 100 cc. portions of Solution A, place in beal^ers, heat to boiling, add NH^OH, drop hy drop, until the solution is strongly alkaline, and a few cubic centimeters of ammonium oxalate solution. Cover the beaker and boil the solution for about one minute ; if no ammonia is given off (detect by smelling), more is added, drop by drop, until it can be detected. Do not allow the precipitate to settle, but stir and filter imme- diately while hot, washing it thoroughly with hot water. * Most of the points in the manipulation were taken directly from a method suggested by O. M. Shedd for the determination of total potas- sium in soils, Journal of Industrial and Engineering Chemistry, Vol. I, No. 5, May, 1909. [49] Evaporate the filtrate and washings nearly to dryness in an evaporating dish, add 1 cc. of dilute H^SO^ (1 : 1), evaporate to dryness, and ignite to whiteness by maintain- ing a full red heat until the residue is perfectly white. Dissolve the residue in hot water, filter if necessary to remove any insoluble material, acidify the clear solution slightly with acetic acid, and evaporate to a volume of about 10 or 15 cc* Ten cubic centimeters or a liberal excess of the cobaltinitrite reagent, prepared according to Adie and Wood, are added slowly, so that the precipitate may not be too finely divided, and the liquid evaporated off on the water bath to a sirupy consistency, becoming solid on cooling. It is important not to heat longer than is necessary. After cooling, the soluble matters are dissolved in about 25 cc. of cold water (which should give a brown solution, showing excess of reagent), the solution decanted through a carefully prepared Gooch crucible,''' and this operation repeated until the dish and any precipitate re- maining in it have been thoroughly washed. t Be sure that all the precipitate is completely removed from the dish. After washing the filter, the contents of the crucible (the asbestos with the precipitate) are transferred to a 500 cc. beaker and well broken up by stirring with a glass rod in a little water. If any of the precipitate adheres to the Gooch crucible so that it cannot be washed off, the cruci- ble also is to be put into the dish. A measured excess * When the reagent is added to a dilute solution, it is decomposed before the potassium salt is precipitated. In small volumes this does not happen. t The asbestos pulp for making the filter should be just fine enough to hold the precipitate and be free from very fine particles. t A half-saturated solution of common salt may be used instead of water if there is trouble in filtering the precipitate. [50] of standard potassium permanganate solution * (usually 20-40 CO.) is now run in, and the whole diluted to about eight or ten times the volume of permanganate added, the dish covered, and its contents heated to boihng over a free flame or on a hot plate, with frequent stirring for about ten minutes, or until the potassium cobaltinitrite is oxidized completely. It has been found that the oxida- tion requires a somewhat longer time than the five to eight minutes recommended by Drushel, apparently because it is hard to separate the yellow potassium precipitate from the asbestos so that the permanganate can come in contact with it. When the oxidation is complete — as indicated by the darkening of the solution and the separation of the man- ganese hydroxide — about 15 cc. of dilute sulphuric acid (1 : 7) are added and allowed to act three or four minutes to favor oxidation of the last traces of cobaltinitrite. t A measured excess of the standard oxalic acid t containing 50 cc. of concentrated sulphuric acid to the liter is then run in, and the liquid kept at the same temperature until all the manganic hydroxide has been dissolved and the solution is colorless. At this point it will be seen by the absence or presence of the yellow potassium compound whether the oxidation of the cobaltinitrite precipitate was complete. The excess of oxalic acid is now titrated with the standard permanganate solution. § The total volume of permanganate solution used, less that equivalent to the oxalic acid added, gives the amount used up in oxidizing * See Experiment No. 15 (approximate N/10 solution). t The sulphuric acid is not to be added at first, along with the per- manganate, as the action would be very rapid and some cobaltinitrite might escape oxidation. t Prepared according to directions on page 90, § See Experiment No. 15. [51] the cobaltinitrite ; and this, multiplied by the appropriate factor, gives the weight of potassium obtained. One cubic centimeter of N/10 permanganate solution is equivalent to 0.000711 g. of K, or 0.000856 g. of Kp. If the potas- sium permanganate solution used for the titration is not exactly N/10, then it is necessary to calculate the appro- priate factor to be used. It is also necessary to carry out a blank experiment, under the same conditions as the analysis, using the same quantities of the reagents, and to subtract the small amount of permanganate solution con- sumed from that found in the analysis. From the results obtained, calculate and report the percentage of potash (K O) in the sample of soil soluble in the acid solution. Question How is the factor for the K equivalent of 1 cc. N/10 KMO^ obtained ? Experiment No. 34 & (Optional Method) DETERMINATION OF POTASH (K^O) IN SOIL SOLUTION BY THE USE OF PLATINUM SOLUTION* Measure out, with a burette or pipette, two 100 cc. portions of Solution A into glazed porcelain evaporating dishes, add 10 cc. concentrated C. P. hydrochloric acid, and evaporate to dryness. Take up with 10 to 15 cc. of distilled water, add about 5 cc. of platinum chloride solution and 2 or 3 cc. of hydrochloric acid, and evaporate to dryness or to a thick paste on a water bath. Remove the dish from the water bath and let stand until it is * This method is a modification of the method proposed by C. C. Moore, Journal of American Chemical Society, Vol. XX (1898), p. 340, and of the method used in the laboratories of the Texas Experiment Station. [52] perfectly cold. Add from 10 to 30 cc. of " acid alcohol," * according to the amount of precipitate in the dish. All other materials beside the precipitate of potassium platinic chloride should be completely dissolved. If there is heat evolved when the acid alcohol is added, more alcohol is added to cool the solution, as this reaction often forms a white insoluble substance which would ruin the results. If enough platinum solution has been added to precipitate all the potassium, the alcoholic solution will be slightly colored. If the alcohol is not slightly colored, it has to be evaporated off, the precipitate redissolved in distilled water containing a few drops of hydrochloric acid, more platinum solution added, and again evaporated to a thick paste and the solution treated Avith acid alcohol, as before. If the alcoholic solution is not colored, owing to an excess of platinum solution, do not add more platinum solution directly to the alcoholic solution, but evaporate off the alcohol first. After the precipitate is treated with acid alcohol, filter by decantation into a properly prepared and weighed Gooch crucible ; wash once with acid alcohol, then with 95 per cent alcohol until the alcohol wash does not dissolve any more colored material of any kind; pour the washings through the crucible each time, but leave the precipitate in the evaporatmg dish as far as possible. Add 10 cc. of special ammonium chloride solution t to the pre- cipitate in the dish, let stand a few minutes so as to dissolve impurities, and pour off the solution through the Gooch crucible. Repeat the washing with the special ammonium chloride solution about five times and again * 10 cc. of concentrated C. P. hydrochloric acid solution added to 100 cc. of 95 per cent alcohol. t Prepared according to directions on page 90. [53] wash thoroughly with 95 per cent alcohol. Transfer the potassium platinic chloride precipitate from the dish to the Gooch crucible by the use of 95 per cent alcohol, washing the side of the crucible carefully so as to remove any adhering solution of ammonium chloride. Dry the pre- cipitate for thirty minutes at the temperature of boiling water, cool in desiccator, and weigh. The precipitate is potassium platinic chloride (K^P^^Ilg), and should be per- fectly soluble in water (which gives a means of checking the results if desired). For the conversion of platinic chloride to potassium oxide (K„()) use the factor 0.1941. Calculate and report the percentage of potash (K^O) in the soil soluble in the acid solution. (Save all filtrates and potassium platinic chloride precipitates so as to recover the platinum.) Note. " Available " phosphoric acid and potash in soils can be determined by digestion with 1 per cent citric acid (Dyer's method). Journal of American Chemical Society, Vol. LXVI (1894), p. 115 ; Lunge, Technical Methods of Chemical Analysis, Vol. I, p. 852. [54] PART lY ANALYSIS OF r^RTILIZEES Pkeparation of Sample of Fektilizer for Analysis * Grind the sample fine enough to pass through a sieve having circular perforations 1 mm. in diameter, and then mix thoroughly. Perform the grinding and sifting as rap- idly as possible to avoid loss or gain during the operation. After the sample is prepared and thoroughly mixed, it should be kept in a well-stoppered bottle. Enough sample should be prepared for all the determinations. Experiment No. 35 determination of moisture in fertilizer Weigh out exactly 2 g. of the fertilizer in a weighed watch glass and dry for three hours at the temperature of boiling water ; cool in desiccator, and weigh rapidly. Heat again at intervals of one-half hour until the material ceases to lose weight. IMake duplicate determinations. Calculate and report the percentage of moisture in the sample of fertilizer. * Bulletin No. 107 (Revised), Bureau of Chemistry, United States Department of Agriculture. [55] Experiment No. 36 PREPARATION OF A STANDARD NaOH SOLUTION FOR PHOSPHORIC ACID (PgOg) DETERMINATION Make up a solution (500 cc.) of sodium h3'droxide (NaOH) so that 10 cc. of this solution should neutralize 16.2 cc. of an exactly N/5 HCl solution. If your standard hydrochloric acid solution is not exactly N/5, then calcu- late the number of cubic centimeters of your HCl solution mk',^ «^i^S^; i^^HiiSli^ COMBINATION ELECTKIC WATER BATH AND HOT PLATE which will be equivaleyit to 16.2 cc. of an exactly N/5 HCl solution. Standardize the NaOH solution so that 10 cc. of it will exactly neutralize the calculated number of cubic centimeters of your standard acid. One cubic centimeter of the NaOH solution will then be equivalent to .001 g. of phosphoric acid (P^O^). [56] Question Show that 1 cc. of the NaOH solution is equivalent to .001 g. of Pp,. Note. For equation see Experiment No. 33 a. Experiment No. 37 DETEEMINATION OF TOTAL PHOSPHORIC ACID (P^O^) IN FERTILIZER Weigh out 2 g. of the sample of fertilizer and place it in a beaker with 15 to 20 cc. of concentrated hydrochloric acid and from 3 to 10 cc. of concentrated nitric acid, and digest from 20 to 30 minntes under the hood. After the solution is complete, cool, add 25 cc. of distilled water, filter, and wash the residue thoroughly, allowing the wasii- ing-s and the original solution to run into a 250 cc. measur- es o m(/ flask. INIake up to the mark with distilled water, stopper the flask, and shake thoroughly. Measure out, with a burette or pipette, two 25 cc. portions into beakers for analysis, and to each portion add 25 cc. of distilled water. Make alkaline with NH^OH, adding 10 cc. in excess, and then sli(jhtlij acid with HNO^ (1 : 1), using a small piece of litmus paper m the solution as indicator. Avoid much excess of HNOg. Warm the solution to the temperature of 60° to 65° C. by standing the beakers in a pan containing warm water. After the solution has reached the required temperature add 30 cc. of ammonium molybdate solution ; stir, and let stand for fifteen mmutes in the warm water at 60° to 65° C. Filter at once and wash twice with water by decantation^ by pouring the solu- tion through the filter, using 25 to 30 cc. of water each time, agitating the precipitate thoroughly, and allowing it [57] to settle. Transfer to the filter paper and wash with cold water until washings are free from acid. (Test by means of litmus paper.) Transfer the filter paper containing the precipitate back into the beaker in which it was precipi- tated. From the burette add your standard NaOH solu- tion (prepared for the l^fi^ determination) until the yellow precipitate is completely/ dissolved. Add about 25 cc. of dis- tilled water and a few drops of phenolphthalein indicator. 1. Should the solution be colorless with the indicator added, continue the addition of NaOH solution until a permanent pink color is obtained; that is, the end-point is reached. 2. Should the solution be colored after tlie indicator is added, that is, alkaline, titrate with your standard HCl solution until the color is discharged, and then titrate with your standard NaOH solution until the end-point is obtained. In either case the total amount of NaOH used to dis- solve mid titrate the yellow precipitate and also the total amount of standard HCl used should be recorded. From the data obtained calculate and report the percentage of phosphoric acid (P^O^) in the sample of fertilizer. Questions 1. Give the reason for each step in the determination and write equations for the reactions. 2. Define raw rock phos- phate, basic slag, acid phosphate, water-soluble phosphoric acid, reverted phosphoric acid, insoluble phosphoric acid, and give their chemical compositions and methods of preparation. [58] Experiment No. 38 DETERMINATION OF WATER-SOLUBLE PHOSPHORIC ACID (P2O5) IN FERTILIZER Weigh out 2 g. of the sample, place it on a 9 cm. filter paper, and leach with successive small portions of distilled water into a 250 cc. measuring flask (allowing each por- tion of water to run through before adding more) until the filtrate measures nearly 250 cc. If the filtrate is turbid, add a few drops of concentrated IIN^O^. Make up to the mark with distilled water and shake the solution thor- oughly. JVIeasure out, with burette or pipette, two 25 cc. portions into beakers and proceed as in Experiment No. 37. Save the residue in the filter paper for Exj^eriment No. 39. Experiment No. 39 DETERMINATION OF CITRATE-SOLUBLE PHOSPHORIC ACID (P2O5) IN FERTILIZER Heat 100 cc. of strictly neutral ammonium citrate solu- tion * (sp. gr. 1.09) to G5°C. in a 200 to 300 cc. Erlen- meyer flask placed in a warm water bath, keeping the flask loosely stoppered. When the citrate solution has reached the temperature of Q^° C, drop into it the filter paper containing the leached residue from the water-soluble phos- phoric acid determination (Exp. No. 38), close tightly with a smooth rubber stopper, and shake violently until the filter paper is reduced to a pulp. Place the flask in the bath, and maintain it at such a temperature (about 67° C.) * Prepared according to directions on page 91. [59] that the contents of the flask will stand exactly at 65° C. Shake the flask every five minutes. At the expiration of exactly thirty minutes from the time the filter with con- tents was introduced, remove the flask from the bath and filter as rapidly as possible. Wash the residue and flask tliorouglily with distilled water heated to the temperature of 65° C. Return the filter with contents to the Erlen- meyer flask, add 30 cc. of concentrated HNO^ and 10 cc. of concentrated HCl, and digest under the hood until phosphates are dissolved ; that is, about twenty or thirty minutes. Dilute with 50 cc. of distilled water, and filter into a 250 cc. measuring flask, washmg the residue thor- oughly. Make up with distilled water to the mark, shake thoroughly, and measure out, with burette or pipette, two 25 cc. portions into two beakers. Then proceed as in Ex- periment No. 37. The total phosphoric acid minus the sum of the water-soluble and citrate-insoluble gives the citrate- soluble phosphoric acid. Calculate and report the percent- age of citrate-insoluble and citrate-soluble phosphoric acid (P^Og) m the sample of fertilizer. Questions 1. Give the formulas for uiolybdic acid, ammonium molyb- date, ammonium phosphomolybdate, and citrate-soluble phos- phoric acid. 2. Write the equation for the reaction of ammonium phosphomolybdate and ISTaOH. 3. Discuss the solu- bility of monocalcium, diealcium, and tricalcium phosphate. 4. Define " available " phosphoric acid. [60] Experiment No. 40 DETERMINATION OF POTASH (K.^O) IN A MIXED FERTI- LIZER BY THE USE OF PLATINUM SOLUTION* Boil 5 g. of the fertilizer sample with 300 cc. of distilled water thirty minutes. Add to the hot solution a slight excess of NH OH and then sufficient ammonium oxalate 4 solution to precipitate all the lime present. Cool, dilute to 500 cc. with distilled water in a measuring flask, shake thoroughly, and filter through a chy filter. Evaporate in an evaporatmg dish 100 cc. of the solution (measured exactly and corresponding to 1 g. of the sample) nearly to dryness, add 1 cc. of dilute sulphuric acid (1 : 1), evap- orate to dryness (being careful not to lose anything by spattering), and ignite to whiteness. As all the potas- sium is in the form of sulphate, no loss need be appre- hended by volatilization of potash, and a full red heat must be maintained until the residue is perfectly white. Dissolve the residue in hot water and filter if any insoluble material remains. Add to the clear solution a few drops of HCl, and platinum solution (H2PtClg)t in slight excess. Evaporate on a water bath to a thick paste and treat the residue with 80 per cent alcohol (sp. gr. 0.8645). If enough platinum solution has been added to precipitate all the potassium, the alcoholic solution will be slightly colored. If the alcohol added to the residue is not slightly colored, the alcohol has to be evaporated off, residue redissolved in water containing a few drops of HCl, more platinum * Potash can be determined by optional method (Exp. No. 40 a). t Prepared according to directions on page 90. [61] solution added, and the solution again evaporated to a thick paste and treated with alcohol. Do not add more platmum solution to the alcoholic solution before evapo- rating off the alcohol. Avoid the absorption of ammonia by the solution. After the residue is treated with 80 per cent alcohol, filter into a properly prepared and treighed Gooch crucible and wash the precipitate thoroughly with 80 per cent alcohol, then with 10 cc. of the special ammonium chloride solution,* to remove impurities. Repeat washing with 10 cc. portions of special ammonium chloride solution about five times, and agam wash thoroughly w^ith the alco- holic solution. Dry the precipitate for thirty minutes at the temperature of boiling water, cool in desiccator, and Aveigli. The precipitate is potassium platinic chloride (KgPtClg) and should be perfectly soluble in water (which gives a means of checking the results if desired). For the conversion of potassium platinic chloride (K^PtClg) to potassium oxide (K^O) use the factor 0.1941. From data obtained, calculate and report the percentage of potash (K O) in the sample of fertilizer. (Save all the filtrates and potassium platinic chloride precipitates so as to recover the platinum.) Experiment No. 40 a (Optional Method) DETERMINATION OF POTASH (K.^O) IN MIXED FERTILIZER BY VOLUMETRIC METHOD Measure ont into evaporating dishes, with a burette or pipette, two 25 cc. portions of the filtered potassium solu- tion prepared in Experiment No. 40. Evaporate each por- tion nearly to dryness in an evaporating dish, add 1 cc. * Prepared according to directions on page 90. [62] of dilute sulphuric acid (1 : 1), evaporate to dryness, and ignite to whiteness by maintaining a full red heat until the residue is perfectly white. Dissolve the residue in hot water, filter if any remains undissolved, acidify the clear solution slightly with acetic acid, and proceed in the same manner as in Experiment No. 34 a. From data obtained calculate and report the percentage of potash (K^O) in the sample of fertilizer. Experiment No. 41 DETERMINATION OF NITROGEN IN FERTILIZERS (NITRATES PRESENT) Weigh out exactly 1 to 2 g. of the sample and transfer to an 800 cc. Kjeldahl flask. Add 30 cc. salicylic acid solution* and 5 g. of sodium thiosulphate. Heat over a low flame until all danger of frothing has passed, cool, and then add about 10 g. of K^SO^ and about .5 g. copper sulphate (CuSO^ . 5 H^O). Continue the digestion until the material is completely oxidized. Make the distillation and titration as given in Experiment No. 19. Make duplicate determinations. From data obtained, calculate and report the percentage of nitrogen in the sample of fertilizer. Questions 1. Explain the use of salicylic acid and sodium thiosulphate. Write equations illustrating. 2. Explain the other steps in the determination. * Prepared according to directions on page 91. [6.3] PART y ANALYSIS OF INSECTICIDE AND FUNGICIDE Experiment No. 42 PREPARATION AND STANDARDIZATION OF SOLUTION POR DETERMINATION OF ARSENIOUS OXIDE (ASgOg) IN PARIS GREEN Starch solution for iyidicator. Place 1 g. of starch in 10 cc. of cold distilled water to separate the granules, and then pour this mixture into 100 cc. of boiling water. Boil for five minutes, stirring continuously. Standard iodine solution. Dissolve about 3.5 g. of iodine in 200 cc. of distilled water in which has been dissolved from 8 to 10 g. of pure potassium iodide (KI). Dilute to a volume of 500 cc. with distilled water and shake thoroughly. Before standardizing be sure that all the iodine is in solution. Dissolve exactly 1 g. of pure arsenious oxide (As O ) m 50 cc. of HCl (1:1), heating rapidly if neces- sary to bring all the arsenic into solution. (Do not boil the solution.') Cool and make up to a volume of 250 cc. in a measuring flask. Perform the titration as follows: Measure out, with a burette or pipette, two portions of 25 cc. of the arsenious oxide (As^O^) solution into porce- 1am evaporating dishes (about 6 in. m diameter) or into [64] large beakers, add about 300 cc. of distilled water, and sodium bicarbonate (NaHCOg) in slight excess. Add the iodine solution from a burette, using the starch solution as an indicator. The titration is complete when you obtain the first permanent blue color. Make at least two titra- tions. Calculate the strength of the iodine solution in terms of arsenious oxide (As^Og). Question Why should the hydrochloric acid solution of arsenious oxide not be boiled ? Experiment No. 43 DETERMINATION OF TOTAL ARSENIOUS OXIDE (AS2O3) IN PARIS GREEN To determine the total arsenious oxide in Paris green use 2 g. and proceed exactly as with the arsenious oxide in the standardization of iodine solution (Exp. No. 42). Make duplicate determmations. Calculate and report the percentage of arsenious oxide (As^O^) in the sample of Paris green. Questions 1. Is Paris green a compound or a mixture ? 2. If a com- pound, what is its formula ? 3. To what is the As^Og oxidized by the iodine ? 4. Give equations for the reaction. 5. How much As^Og can Paris green contain and still be safe as an insecticide ? 6. Give a simple test for the purity of Paris green. [65] Experiment No. 44 DETERMINATION OF WATER-SOLUBLE ARSENIOUS OXIDE (AS2O3) IN PARIS GREEN Place 1 g. of Paris green (weighed exactly) in a large flask with exactly 500 cc. of distilled water (previously boiled to expel carbon dioxide and then cooled to room temperature). Stopper the flask, shake thoroughly, and let stand for one week, shakmg as often as convenient. At the end of this time filter the solution through a dry filter. Dilute 100 cc. of the filtrate with 100 cc. of dis- tilled water, add sodium bicarbonate (NaHCO^) in slight excess, and titrate with your standard iodine sohition in the same manner as m Experiment No. 42, using the starch solution as indicator. Make duplicate titrations. Calculate and report the percentage of water-soluble arsenious oxide (As^Og) in the sample of Paris green. Analysis of Lead Arsenate * Preparation of saynple. If the sample is in the form of a paste (as it usually is), dry the whole sample to constant weight at the temperature of boiling water and record the results as total moisture. Grind the dry sample (which will gain a small amount of moisture during grinding) to a fine powder and determine the various constituents as follows: * These methods are modifications of methods proposed by Haywood, Bulletin No. 105, Bureau of Chemistry, United States Department of Agriculture (1907), p. 165. [66] » Experiment No. 45 DETERMINATION OF MOISTURE IN LEAD ARSENATE Heat 2 g. of the sample in the water oven at the tem- perature of boiling water for eight hours or in the hot- air oven at 110° C. for from five to six hours or till constant weight is obtained. Make duplicate determina- tions. Calculate and report the percentage of moisture in the sample of lead arsenate. Experiment No. 46 DETERMINATION OF TOTAL LEAD OXIDE IN LEAD ARSENATE Dissolve 2 g. of the sample in about 80 cc. of water and 15 cc. of concentrated nitric acid on the steam or water bath ; transfer the solution to a 250 cc. measuring flask and make up to the mark. To 50 cc. of the solution add 3 cc. of concentrated sulphuric acid ; evaporate on the steam bath to a sirupy consistency and then on a hot plate till white fumes appear and all nitric acid has been driven off. Add 50 cc. of water and 100 cc. of 95 per cent alcohol, let stand for several hours, and filter off the supernatant liquid ; wash about ten times with acidified alcohol (water 100 parts, 95 per cent alcohol 200 parts, and concentrated sulphuric acid 3 parts) and then with 95 per cent alcohol* till free from sulphuric acid. Dry, transfer as much as possible of the precipitate from the paper into a weighed crucible, and ignite at a low red * Prepared according to directions on page 92. [67] heat. Burn the paper in a separate porcelain crucible, and treat the residue first with a little nitric acid, which is afterwards evaporated off, and then with a drop or two of sulphuric acid. Ignite, weigh, and add this weight to the weight of the precipitate previously removed from the paper for the amount of the lead sulphate. Calculate and report the percentage of lead oxide m the sample of lead arsenate. Question Write equations for the chemistry of each step in the determination. Experiment No. 47 DETERMINATION OF WATER-SOLUBLE LEAD OXIDE IN LEAD ARSENATE Weigh out 2 g. of the lead arsenate, place in a flask with 2000 cc. of carbon-dioxide-free water, and let stand for a week, shaking as often as convenient (eight times a day if possible). Filter through a dry filter and use aliquots (200 to 400 cc.) of this solution for determin- ing soluble lead oxide and arsenic oxide (As^O^) ; deter- mine lead as described in Experiment No. 46 for total lead oxide, using the same relative proportions of sul- phuric acid, water, and alcohol, but keeping the volume as small as possible. ]\Iake duplicate determmations. Cal- culate and report the percentage of water-soluble lead oxide m the sample of lead arsenate. [68] Experiment No. 48 DETERMINATION OF TOTAL ARSENIC OXIDE (AS2O5) IN LEAD ARSENATE Transfer 100 cc. of the nitric acid solution of the sample, prepared as in the determination of lead (Exp. No. 46), to a porcelain dish, add 6 cc. of concentrated sulphuric acid, evaporate on the water bath to a sirupy consist- ency and then on a hot plate until the appearance of white fumes of sulphuric acid. Wash into a 100 cc. flask with water, make up to the mark with distilled water, filter through a dry filter, and use 50 cc. aliquot parts for further work. Transfer this to an Erlenmeyer flask of 400 cc. capacity, add 4 cc. of concentrated sulphuric acid and 1 g. of potassium iodide, dilute to about 100 cc, and boil until the volume is reduced to about 40 cc. Cool the solution under running water, dilute to about 300 cc, and exactly use up the iodine set free and still remaining in the solution w4th a few drops of approximately tenth-normal sodium thiosulphate solution. Be careful that an excess of sodium thiosulphate is not used. Wash the mixture into a large beaker, make alkalme with sodium carbonate, and slightly acidify with dilute sulphuric acid, using up all the sodium carbonate ; then make alkaline with an excess of sodium bicarbonate. Titrate the solution with your standard iodine solution until a blue color appears, using the starch solution as indicator. Calculate and report the percentage of arsenic oxide (As^O^) in the sample of lead arsenate. [69] Questions 1. Discuss the commercial preparation of lead arsenate and varieties. 2. Name the desirable properties of an insecticide. 3. Write equations for the chemistry of each step in the determination. Experiment No. 49 DETERMINATION OF WATER-SOLUBLE ARSENIC OXIDE (AS2O5) IN LEAD ARSENATE For this determination use 200 to 400 cc. of the water extract obtained under the determination of soluble lead oxide (Exp. No. 47). Add 0.5 cc. of sulphuric acid and evaporate to a sirupy consistency, then heat on a hot plate until white fumes appear. Add a very small amount of distilled water, and filter through a small iilter paper to remove the lead, using as little wash water as possible. Place this filtrate in an Erlenmeyer flask, and determine arsenic, as described above, for total arsenic oxide, using the same amount of reagents and the same dilutions. Cal- culate and report the percentage of Avater-soluble arsenic oxide (As.^Og) in the sample of lead arsenate. Experiment No. 50 TESTING BORDEAUX MIXTURE FOR SOLUBLE COPPER Take a small piece of quicklime (CaO) and slake it with water. Weigh out on the rough balance about 5 g. of copper sulphate (CuSO^ • 5 H^O) and dissolve in about 100 cc. of water. Add the milk of lime to the copper sulphate solution until you cannot obtain a test with potassium ferrocyanide (K^Fe(CN)g).* (The test for * Prepared according to directions on page 92. [70] soluble copper should be made by using small filtered por- tions taken from the original mixture.) This is known as Bordeaux mixture. Take a portion of the mixture, dilute it with water, and pass carbon dioxide mto it for about fifteen minutes. Again test the solution for soluble copper. Questions 1. Explain your results. 2. Also make the test for soluble copper by adding a drop of dilute ammonia to the clear solu- tion, noting the blue copper hydroxide. Add more ammonia and observe the soluble blue compound. 3. How does the carbon dioxide of the air cause bad effects with Bordeaux mixture ? 4. How could you prevent it ? 5. Discuss the composition of Bordeaux mixture and the killing of foliage by its use as a spray. 6. With what insecticides can it be used ? [71] PART YI ANALYSIS OF MILK Experiment No. 51 DETERMINATION OF SPECIFIC GRAVITY OF MILK The sample of milk is thoroughly mixed and poured into a cylinder or hydrometer jar. Determine iirst the temperature of the milk and then, by means of a hy- drometer or lactometer, determine the specific gravity. The hydrometer or lactometer should be gently lowered into the milk and the reading observed from the top of the meniscus. The temperature of the milk should be adjusted to 15.5° C. before the readmg is made, or the correction for the temperature should be made so as to record the specific gravity reading at the temperature of 15.5° C. or 60° F. The Quevenne and New York Board of Health lactometers are used to the largest extent for this determination. To prevent the milk from souring before the other determinations are made, add 1 cc. of formalin (40 per cent solution of formaldehyde) to one pint of the milk, and keep the bottle stoppered. Questions 1. What is specific gravity ? 2. Name four ways of deter- mining specific gravity of a liquid. 3. Explain the effect of [72] watering and skimming (and the two combined) upon the specific gravity. References Leach. Food Inspection and Analysis. Richmond. Dairy Chemistry. Van Slyke. Modern Methods of Testing Milk and Milk Products. Wiley. Agricultural Analysis, Vol. III. Experiment No. 52 DETERMINATION OF TOTAL SOLIDS IN MILK Measure out, with a burette or pipette, 10 cc. of milk of known specific gravity mto a tared flat-bottomed dish of not less than 5 cm. diameter. Evaporate to dryness on a water bath, and dry in water oven for thi^ee hours at the temperature of boiling water. Cool in desiccator and weigh rapidly. Heat again at intervals of one-half hour until the material ceases to lose weight. Make duplicate determmations. Calculate and report the percentage of total solids in the sample of milk. Questions 1. What does the total solids of milk contain ? 2. The milk residne should be nearly pure white (a brownish color shows decomposition). Explain. 2. What effect would the souring of milk have on the content of the total solids in the milk? Explain. Experiment No. 53 DETERMINATION OF ASH IN MILK Measure out, with a burette or pipette, two 25 cc. por- tions of milk into weighed porcelam dishes. Add 5 cc. of concentrated HNO^, evaporate to dryness, and ignite at [78] I a temperature just below redness until the ash is free of carbon. Cool in desiccator and weigh. Make duplicate determinations. Calculate and report the percentage of ash in the sample. Question What does the ash of milk contain ? Experiment No. 54 DETERMINATION OF FAT IN MILK BY THE WERNER- SCHMIDT METHOD Transfer 10 cc. of milk, measured accurately^ to a large test tube (50 cc. capacity), add 10 cc. of concentrated HCl, cork tightly, shake thoroughly, and heat in a water bath for about ten minutes, with frequent shaking, until the liquid is of a deep-brown color. The heating must not be continued too long. Cool the tube thoroughly in a stream of water, add about 30 cc. of ether, and shake vigorously. Allow to stand until the ether layer, which contains the fat, has separated out. Transfer as much as possible of the ether layer, without disturbing the other layer, to a weighed flask (this may con- veniently be done by closing the test tube with a cork provided with small glass tubes similar to a wash bottle, the larger tube adapted to slide up and down in the cork and turned up slightly at the bottom. When the ether layer is ready to be transferred to the flask, the slid- ing tube is arranged so that it terminates just above the division of the two layers, and the ether is then blown out into the weighed flask). Add 10 cc. of ether to the test tube and shake again. Transfer this ether layer to the weighed flask. In the same manner make two more [74] extractions and transfer the ether layer to the weighed flask as before. Evaporate off the ether in the weighed flask, dry at the temperature of boiling water until free of ether^ cool in desiccator, and weigh. Make duplicate determinations. Calculate and report the percentage of fat in the sample. Questions 1. Name and describe two other methods for the determina- tion of fat in milk. 2. If the sample of milk is slightly churned, how would you proceed to determine the fat content ? Experiment No. 55 DETERMINATION OF TOTAL PROTEIN (CASEIN AND ALBUMIN) IN MILK Measure out, with a burette or pipette, two 5 cc. portions of milk into Kjeldahl flasks, and proceed with the diges- tion, distillation, and titration as in Experiment No. 19. Multiply the percentage of nitrogen by 6.38 to obtain the percentage of total protem in milk. Calculate and report the percentage of total protem in the sample. Question How was the factor 6.38 obtained ? Experiment No. 56 DETERMINATION OF CASEIN IN MILK Measure out, with a burette or pipette, two 10 cc. por- tions of milk into beakers, dilute with distilled water to a volume of 100 cc, heat to a temperature of 40° to 42° C, and add at once 1.5 cc. of an approximate 10 per cent [75] acetic acid solution. Stir with a rubber-tipped glass rod, or policeman, and let stand for about five minutes, then decant on filter, wash thoroughly with cold water by decantation (pouring the washings through the filter paper each time), and transfer precipitate completely to filter. The filtrate should be clear or very nearly so. If it is not clear when it is first run through, it should again be filtered through the same filter and washed as before. Transfer the filter paper and contents to Kjeldahl flasks and proceed with the digestion, distillation, and titration as in Experiment No. 19. Multiply the percentage of nitrogen by 6.38 to obtain the percentage of casein in the milk. Calculate and report the percentage of casein in the sample. Questions 1. What is the federal standard for milk ? the state stand- ard ? 2. What is the composition of cow's milk ? 3. How does it differ from hmnan milk ? 4. How is cow's milk modified for infants ? 5. What facts shown by an analysis would influ- ence you to believe that a sample of milk had been skimmed ? watered ? skimmed and watered ? 6. To what is the acidity of milk due ? 7. What is the composition of Cheddar cheese ? 8. Give the commercial uses of casein. Reference Leach. Food Inspection and Analysis (3d ed.), p. 160. 1914. Note. Casein may be determined by volumetric methods : AValker, Journal of Industrial and Engineering Chemistry, Vol. VI, pp. 131, 356 (1914) ; Hart, Journal of Biological Chemistry, Vol. VI, p. 445 (1909) ; Van Slyke and Bosworth, Technical Bulletin No. 10 (1909), New York (Geneva) Experiment Station. [76] PART VII A BEIEF SANITAEY EXAMINATION OF WATER Experiment No. 57 DETERMINATION OF TOTAL SOLIDS IN WATER Evaporate 200 cc. of water iii a small evaporating dish on a water bath (a portion of the total volume can be evaporated, then more added until the total amount is evaporated). Dry at 105° C. in an oven until weight is constant, cool in desiccator, and weigh. Calculate and report parts of total solids per million parts of water, also in terms of grains per gallon. Qualitative Analysis Test the residue for phosphates, chlorides, sulphates, iron, aluminium, magnesium, and calcium. Experiment No. 58 DETERMINATION OF CHLORINE AS CHLORIDES IN WATER Measure out, with a pipette or burette, 50 cc. of water into each of two small beakers or evaporating dishes. Add from three to four drops of potassium chromate solu- tion (10 per cent) as an indicator, coloring the contents of each beaker exactly alike. Place the beakers on a white surface. Titrate the water in the beakers with standard [77] silver nitrate (AgNO^) solution. Add one drop at a time, and continue the titration with frequent agitation until the water shows the first tinge of red. Make duplicate determinations. If convenient, the titration should be per- formed under a yellow light or by wearing yellow-colored goggles. Calculate and report parts of chlorine and its equivalent in NaCl per million parts of water. Questions 1. If the water contains over 5 parts of chlorine per 100,000 parts of water, what is suspected ? Discuss. 2. What is the chlorine content of sea water ? 3. What is the sanitary significance of the chlorine content of water ? 4. Write equa- tions illustrating all reactions. 5. State the relative solubilities of silver chloride and silver chromate. Experiment No. 59 DETECTION OF FREE AMMONIA IN WATER To 25 cc. of water in a tall test tube add 5 cc. of Ness- ler's reagent * and note the color. Only a faint yellow tinge should be visible. A deeper color or turbidity generally indi- cates animal contamination. Compare the treated sample with the untreated sample in a similar tube. The experi- ment can be made quantitatively by comparing the color of the sample with different samples of distilled water con- taining known amounts of ammonium chloride (NH^Cl). Questions 1. Of what does Nessler's reagent consist ? 2. Define free and albuminoid ammonia. 3. How is albuminoid ammonia determined? 4. Discuss the significance of free and albumi- noid ammonia in water. * Prepared according to directions on page 92, [78] Experiment No. 60 DETECTION OF NITRITES IN WATER Into a large test tube place a drop of HCl, 2 cc. sulphanilic acid* and equal volumes of naphthylamine hydrochloride,* and 50 cc. of the water under examination. If a red color is produced immediately or within twenty minutes, the presence of nitrites is assured. As a rule nitrites are not found in good water. Any water contain- ing nitrites should be suspected of being contaminated. Why ? The test tube should be corked to avoid contami- nation from laboratory atmosphere. Experiment No. 61 DETECTION OF NITRATES IN WATER Evaporate 100 cc. of the sample to dryness in an evaporating dish over a water bath. Treat with 1 cc. of phenolsulphonic acid,* stirring thoroughly. Add 10 cc. of distilled water and half as much NH^OH. In the pres- ence of nitrates the characteristic color (yellow) of the ammonia salt of nitrophenol-sulphonic acid is formed. Nitrates are present in almost all natural waters. Why? * Prepared according to directions on page 93 or by a method proposed by Chamot, Pratt, and Redfield in an article entitled "A Study on the Phenolsulphuric Acid Method for the Determination of Nitrates in Water" (a modified phenolsulphuric acid method), Journal of American Chemical Society, Vol. XXXIII, No. 3 (1911). The reagent when prepared by the method recommended by Chamot, Pratt, and Redfield consists of the diacid with only traces of monoacids. This method is especially desirable when the reagent is to be used for quantitative work, as the method of preparation given in this manual yields a mixed product. [79] Experiment No. 62 DETERMINATION OF ABSORBED OXYGEN IN WATER Place 100 cc. of water in a beaker and add 10 drops of H^SO^. Warm gently and add the standard solution (KMnO^), drop by drop (stirring constantly). As soon as the first tinge of pink appears, warm the beaker again and notice if the color is permanent. The first tinge of permanent pink denotes the end of the operation. The test should be limited to about fifteen minutes. This determination gives reliable information concern- ing the amount of organic contamination, but does not distinguish between that of vegetable and animal origin. If more than one grain per gallon is absorbed, the water is probably polluted. Experiment No. 63 DETERMINATION OF TEMPORARY HARDNESS OR ALKALINITY OF WATER Titrate 100 cc. of water with your standard solution of HCl, using methyl orange or erythrosin and chloroform as indicator. Calculate and report results in parts of cal- cium carbonate (CaCOg) per 100,000 parts of water, giving the so-called degrees of hardness. If sodium or potassium carbonates are present, they will also react alkaline, but a correction for this error can be obtained by determining permanent hardness. Reference Olsen. Quantitative Chemical Analysis. [80] Questions 1. What is hard water ? 2. Define permanent hardness and temporary hardness. 3. Give another way in which the hardness of water may be determined. 4. Give the essential determinations on water for the following purposes : (1) drink- ing, (2) boiler, (3) irrigation. 5. State the benefits derived from each. 6. Discuss the correction of undesirable properties of waters used for different purposes. [81] PART YIII APPENDIX BOOKS OF REFERENCE Airman, C. M. Milk, its Nature and Composition. Allen, A. H. Commercial Organic Analysis. 4 vols. Allyn, L. B. Elementary Applied Chemistry. Blyth, a. W. Foods, their Composition and Analysis. Bulletin No. 107 (Revised) (1907), Bureau of Chemistry, United States Department of Agriculture. " Methods of Analysis adopted by the Association of Official Agricultural Chemists." Bulletin No. 65 (1902), Bureau of Chemistry, United States Depart- ment of Agriculture. "Provisional Methods for the Analysis of Foods adopted by the Association of Official Agricultural Chemists." Chamot and Redfield. Analysis of Water. CoHN, Alfred I. Indicators and Test Papers. Evans, P. N. Course in Quantitative Chemical Analysis. FouLK, C. W. Notes on Quantitative Chemical Analysis. Frankland, Percy F. Agricultural Chemical Analysis. Fresenius. Quantitative Analysis. 2 vols. Translated by Cohn. Hillebrand, W. F. The Analysis of Silicate and Carbonate Rocks. Bulletin No. 305, United States Geological Survey. Ingle, H. Manual of Agricultural Chemistry. Journal of the Association of Official Agricultural Chemists. Leach, A. E. Food Inspection and Analysis (3d ed.). Leffman and Beam. Select Methods of Food Analysis. Lincoln and Walton. Elementary Quantitative Chemical Analysis. Mahin, E. G. Quantitative Analysis. Morse, H. N. Exercises in Quantitative Analysis. Olsen, J. C. Pure Foods. [82] Olsen, J. C. Quantitative Chemical Analysis (3d ed.). Richmond, II. D. Dairy Chemistry. Sherman, H. C. Organic Analysis (2d ed.). Snyder, H. Dairy Chemistry. Snyder, H. Soils and Fertilizers. Sutton, F. Volumetric Analysis (10th ed.). Talbot, H. P. Quantitative Chemical Analysis. Treadwell-Hall. Analytical Chemistry. Vol. II, Quantitative Analysis. Van Slyke, L. L. Modern Methods of testing Milk and, Milk Products. 1913. Wiley, H. W. Foods and their Adulteration. 1913. Wiley, H. W. Principles and Practice of Agricultural Analysis. Vol. I, "Soils" (1906); Vol. II, "Fertilizers and Insecticides" (1908); Vol. Ill, "Agricultural Products" (1911). TABLES OF WEIGHTS Metric System Milligram = 0.0154 grain Gram = 15.4323 grains Gram = 0.03527 ounce avoirdupois Gram = 0.0321 ounce troy Kilogram = 2.2046 pounds avoirdupois Kilogram = 2.6792 pounds troy Avoirdupois Long ton = 2240 pounds = 1016.047 kilograms Short ton = 2000 pounds = 907.184 kilograms Pound = 16 ounces = 7000 grains = 453.5924 grams Ounce = 437.5 grains = 28.3495 grams Grain = 64.798 milligrams = 0.06479 Tro2j Pound = 12 ounces = 5760 grains = 373.241 grams Ounce = 20 pennyweights = 480 grains = 31.103 grams Pennyweight = 24 grains = 1.555 grams Grain =: 64.7989 milligrams = 0.06479 gram [83] Troy (^jjliarinacij) Ounce = 8 drams = 480 grains = 31.1034 grams Dram = 3 scruples = 60 grains = 3.8879 grams Scruple = 20 grains = 1.295 grams TABLES OF MEASURES Length Millimeter = 0.039 inch Centimeter = 0.393 inch Decimeter = 3.937 inches Meter = 39.37 inches Meter = 3.280 feet Meter = 1.0936 yards Inch = 2.540 centimeters Foot (12 inches) = 3.0480 decimeters Yard (3 feet) = 0.914 meter Mile (1760 yards) = 5280 feet Mile (1.609347 kilometers) = 1609.347 meters Surface Square millimeter = 0.00155 square inch Square centimeter = 0.1549 square inch Square decimeter = 15.499 square inches Square decimeter = 0.1076 square foot Square meter = 1549.997 square inches Square meter (10.764 square feet) = 1.195 square yards Volume Gallon (U.S.) = 231 cubic inches Gallon (U.S.) = 3.785 liters Quart (U.S.) = 0.946 liter Pint (U.S.) = 0.473 liter Liter (U.S.) = 2.113 pints (U.S.) = 1.0566 quarts (U.S.) = 0.264 gallon (U.S.) Cubic meter = 1.307 cubic yards = 35.314 cubic feet An imperial gallon (English) = 4.545 liters = 277.410 cubic inches (U.S.) [84] STRENGTH OF HCl SOLUTION AT DIFFERENT DENSITIES, 15°C. Specific Per cent Grams HCl Specific Per cent Grams HCl Gravity OF HCl IN 100 cc. Gravity OF HCl IN 100 cc. 1.095 19.06 20.9 1.150 29.57 34.0 1.100 20.01 22.0 1.155 30.55 35.3 1.105 20.97 23.2 1.160 31.52 36.6 1.110 21.92 24.3 1.165 32.49 37.9 1.115 22.86 25.5 1.170 33.46 39.2 1.120 23.82 26.7 1.175 34.42 40.4 1.125 24.78 27.8 1.180 35.39 41.8 1.130 25.75 29.1 1.185 36.31 43.0 1.135 26.70 30.3 1.190 37.23 44.3 1.140 27.66 31.5 1.195 38.16 45.6 1.145 28.61 32.8 1.200 39.11 46.9 STRENGTH OF H2SO4 SOLUTION AT DIFFERENT DENSITIES, 15° C. Specific Gravity Per cent OF H2SO4 Grams H2SO4 IN 100 cc. Specific Gravity Per cent OF H2SO4 Grams H2SO4 IN 100 cc. 1.700 77.17 131.2 1.790 85.70 153.4 1.710 78.04 133.4 1.800 86.90 156.4 1.720 78.92 135.7 1.810 88.30 159.8 1.730 79.80 138.1 1.820 90.02 163.9 1.740 80.68 140.4 1.825 91.00 166.1 1.750 81.56 142.7 1.830 92.10 168.5 1.760 82.44 145.1 1.835 93.43 171.3 1.770 83.32 147.5 1.840 95.60 175.9 1.780 84.50 150.4 [85] STRENGTH OF HNO3 SOLUTION AT DIFFERENT DENSITIES, 15° C. Specific Gravity Per cent OF HNO3 Grams HNO3 IN 100 CO. Specific Gravity Per cent OF HNO3 Grams HNO3 IN 100 cc. 1.20 32.36 38.8 1.37 59.39 81.4 1.21 33.82 40.9 1.38 61.27 84.6 1.22 35.28 43.0 1.39 63.23 87.9 1.23 36.78 45.2 1.40 65.30 91.4 1.24 38.20 47.5 1.41 67.50 95.2 1.25 39.82 49.8 1.42 69.80 99.1 1.26 41.34 52.1 1.43 72.17 103.2 1.27 42.87 54.4 1.44 74.68 107.5 1.28 44.41 56.8 1.45 77.28 112.1 1.29 45.95 69.3 1.46 79.98 116.8 1.30 47.49 61.7 1.47 82.90 121.9 1.31 49.07 64.3 1.48 86.05 127.4 1.32 50.71 66.0 1.49 89.60 133.5 ^ 1.33 52.37 69.7 1.50 94.09 141.1 1.34 54.07 72.5 1.51 98.10 148.1 1.35 55.79 75.3 1.52 99.67 151.5 1.36 57.57 78.3 STRENGTH OF NH^OH SOLUTION AT DIFFERENT DENSITIES, 15° C. Specific Gravity Per cent of NH3 Grams NH3 IN 100 cc. Specific Gravity Per cent OF NH3 Grams NH3 IN 100 cc. " .936 16.82 15.74 .916 23.03 21.09 .934 17.42 16.27 .914 23.68 21.63 .932 18.03 16.81 .912 24.33 22.19 .930 18.64 17.34 .910 24.99 22.74 .928 19.25 17.86 .908 25.65 23.29 .926 19.87 18.42 .906 26.31 23.83 .924 20.49 18.93 .904 26.98 24.39 .922 21.12 19.47 .902 27.65 24.94 .920 21.75 20.01 .900 28.33 25.50 .918 22.39 20.56 .898 29.01 26.05 [86] STRENGTH OF NaOH SOLUTION AT DIFFERENT DENSITIES, 15° C. Specific Gravity Baume Per cent of NaOH Grams NaOH IX 100 cc. 1.075 10 6.55 7.0 1.083 11 7.31 7.9 1.091 12 8.00 8.7 1.100 13 8.68 9.5 1.108 14 9.42 10.4 1.116 15 10.06 11.2 1.125 16 10.97 12.3 1.134 17 11.84 13.4 1.142 18 12.64 14.4 1.152 19 13.55 15.6 1.1G2 20 14.37 16.7 1.171 21 15.13 17.7 1.180 22 15.91 18.8 1.190 23 16.77 20.0 1.200 24 17.67 21.2 1.210 25 18.58 22.5 1.220 26 19.58 23.9 1.231 27 20.59 25.3 1.241 28 21.42 26.6 1.252 29 22.64 28.3 1.263 30 23.67 29.9 1.274 31 24.81 31.6 1.285 32 25.80 33.2 1.297 33 26.83 34.8 1.308 34 27.80 36.4 1.320 35 28.83 38.1 1.332 36 29.93 39.9 1.345 37 31.22 42.0 1.357 38 32.47 44.1 1.370 39 33.69 46.2 1.383 40 34.96 48.3 1.397 41 36.25 50.6 1.410 42 37.47 52.8 1.424 43 38.80 55.3 1.438 44 39.99 57.5 1.453 45 41.41 60.2 [87] SOLUBILITIES IN WATER All the chlorides are soluble except those of silver, lead, and mercurous mercuri/. All the sulphates are soluble except those of strontium, barium, and lead. All the carbonates and phosphates are insoluble except those of sodium,, potassium, and amvionium. All the hydroxides are insoluble except those of sodium, 2)otassium, ammoniuMi, calcium, strontium, and barium. All nitrates, acetates, and chlorates are soluble. DIRECTIONS FOR PREPARATION OF REAGENTS Indicatoks for Volumetric Analysis Litmus. Boil 1 g. of purified powdered litmus with 60 cc. of distilled water, filter, and divide filtrate into two equal por- tions. To one portion add dilute H.^SO^, drop by drop, until the solution is just acid. Mix the two portions and keep in a glass-stoppered bottle. CochineaL Digest 1 g. of crushed cochineal dregs in 100 cc. of 25 per cent alcohol (be sure the alcohol is neutral) and filter. Methyl Orange. Dissolve 1/10 g. in 100 cc. of distilled water. Methyl Redo Dissolve 1/10 g. in 100 cc. of distilled water. Phenolphthalein. Dissolve 1 g. in 100 cc. of 50 per cent alcohol. Corallin. Saturate alcohol (that has previously been made neutral) with corallin. I. Solutions for Quantitative Analysis Asbestos for Gooch Crucible. Select a good grade of asbestos with long fibers. The asbestos should be separated until the fibers are about one-fourth inch long, then digested with con- centrated HCl for twelve hours, filtered, and washed with dis- tilled water until free from chlorides. Transfer the asbestos to a bottle containing distilled water [88] Silver Nitrate Solution. Dissolve 16.994 g. of silver nitrate (AgNOg) crystals in 1000 cc. of distilled water (free from chlorides) and place in a dark-colored bottle away from the sunlight. Ammonium Oxalate Solution. Dissolve 42 g. of ammonium oxalate ((NH2)2Cp^ • Hfi) in 1000 cc. of distilled water. 11. Solutions used in the Analysis of Feedstuff Saturated Solution of Sodium Hydroxide. Dissolve about 1000 g. of NaOH in 1 liter of water, cool, and pour into a bottle (crude NaOH may be used if the impurities are allowed to settle and the clear solution drawn off for use). Anhydrous, Alcohol-Free Ether. Let the ether stand in con- tact with calcium chloride (CaCl^, 50 g. to about 500 cc.) until next laboratory period, and distill, using a distilling tube. Place the distilled ether in a dry glass-stoppered bottle over metallic sodium free from" oil. For a short time leave the bottle loosely stoppered so that the hydrogen evolved may escape. The ether should be filtered, or the clear solution should be drawn off ivithout distui'hing the residue. III. Solutions used in the Anahjsis of Soils Ammonium Oxalate Solution. Prepared as in I. Sodium Ammonium Hydrogen Phosphate (Microcosmic Salt). Dissolve 100 g. of sodium ammonium hydrogen phosphate (NaNH^HPO^ . 4 Hp) in 1 liter of distilled water. Ammonium Molybdate Solution. "* Dissolve 100 g. of molybdic acid in 144 cc. of ammonium hydroxide (sp. gr. 0.90) and 271 cc. of water ; slowly, and with constant stirring, pour the solution thus obtained into 489 cc. of nitric acid (sp. gr. 1.42) and 1148 cc. of water. Keep the mixture in a warm place for * Bulletin 107 (Revised), Bureau of Chemistry, United States Depart- ment of Agriculture. [89] several days or until a portion heated to 40*^ C. deposits no yellow precipitate of ammonium pliospliomolybdate. Decant the solution from any sediment and preserve in a glass-stoppered bottle. Ammonium Carbonate Solution. Add 250 cc. of ammonium hy- droxide (sp. gr. 0.90) to 250 g. ammonium carbonate ((NHJ^CO ) and make up to a liter. Saturated Solution of Sodium Hydroxide. Prepared as in I. Saturated Solution of Barium Hydroxide. Dissolve about 50 g. of barium hydroxide in 1 liter of water. Platinum Solution. Dissolve 172.8 g. PtCl^ in 1 liter of water. (1 cc. of the solution contains .1 g. of platinum, e(_[uivalent to .21 g. H^^PtCl^.) Solution of Oxalic Acid. Dissolve 3.2 g. of oxalic acid (Cfifi^ . 2H,0) in 500 cc. of distilled water containing 25 cc. of concentrated C. P. H.,SO^. Measure out, with a pipette or burette, two 25 cc. portions into beakers, add 2 cc. of H^SO^ (1 : 1), heat to 60° C, and titrate with the standard KMnO^ solu- tion. Note the volume of KMnO^ solution required to oxidize completely 1 cc. of the oxalic acid solution. Ammonium Chloride Solution saturated with Potassium Chloro- platinate. Dissolve 100 g. of ammonimn chloride in 500 cc. of water, add from 5 to 10 g. of pulverized potassium chloroplat- inate (potassium platinic chloride), and shake at intervals for six or eight hours. Allow tlie mixture to settle, filter, and use the clear filtrate for the potash determination. The residue may be used for the preparation of a fresh supply. Cobaltinitrite Reagent.* Dissolve 220 g. of sodium nitrite in 400 cc. of water and 113 g. of cobalt acetate in 300 cc. of water, and add 100 cc. of glacial acetic acid. The two solu- tions are mixed and gently warmed, NO2 is evolved, and the solution becomes dark colored. The NO^ is best evacuated from the bottle by a water pump and the liquid left overnight, * F. Sutton, Volumetric Analysis (Otb ed.), p. 62. [90] during whicli a yellow precipitate settles. The solution is then filtered and diluted with water to 1 liter. Alcohol Solution. Prepare the alcohol solution containing 80 per cent alcohol (sp. gr. .8639 at 15° C). Asbestos for Gooch Crucible. Prepared as in I. IV. Solutions used in the Analysis of Fertilizers Ammonium Molybdate Solution. Prepared as in III. Ammonium Oxalate Solution. Prepared as in I. Ammonium Chloride Solution saturated with Potassium Chloro- platinate. Prepared as in III. Asbestos for Gooch Crucible. Prepared as in I. Alcohol Solution (8o%). Prepared as in III. Cobaltinitrite Reagent. Prepared as in III. Platinum Solution. Prepared as in III. Magnesia Mixture. Weigh out 11 g. of recently ignited cal- cined magnesia and dissolve in dilute hydrochloric acid, avoid- ing an excess. Add a little excess of magnesia and boil to precipitate iron, alumina, and phosphoric acid. Filter, add 140 g. ammonium chloride and 130.5 g. of ammonium hydrox- ide (sp. gr. .9), and dilute to 1 liter. Instead of the calcined mag- nesia, 55 g. of crystallized magnesium chloride (MgCl^ • 6 H^O) may be used. Salicylic Acid Solution. Add 1 g. salicylic acid to 30 cc. H^SO^. Shake until thoroughly mixed, and allow it to stand from five to ten minutes, with frequent shakings. Ammonium Citrate Solution.* Dissolve 370 g. of commer- cial citric acid in 1500 cc. of water; nearly neutralize with * Hall, Journal of Industrial and Engineering Chemistry^ Vol. Ill (1911), p. 559 ; Rudnick, Journal of Industrial and Engineering Chemistry, Vol, V (1913), pp. 12, 998 ; E. D. Eastman and J. H. Hildebrand, Journal of Industrial and Engineering Chemistry, Vol. VI (1914), p. 578 ; Hall, Jour- nal of American Chemical Society, Yo\. XXXVII (January, 1915), p. 208. Bulletin 107 (Revised), Bureau of Chemistry, United States Department of Agriculture. [91] commercial ammonium hydroxide; cool; add ammonium hy- droxide until exactly neutral (testing with saturated alcoholic solution of corallin) ; and dilute to a volume of 2 liters. Deter- mine the specific gravity, which should be 1.09 at 20° C. V. Solutions used in the Amdysls of Insecticides Alcohol Solution (95% CgHgOH by Volume). Prepare a solu- tion of alcohol whose specific gravity is .8164 at 15° C. Potassium Ferrocyanide Solution. Dissolve 84 g, of potassium ferrocyanide (K^Fe(Cn)g) in 1 liter of distilled water. VI. Solutions used in the Analysis of Milk Anhydrous, Alcohol-Free Ether. Prepared as in II. Saturated Sodium Hydroxide Solution. Prepared as in II. VII. Soli(tio7is used in a Brief Sanitary Ejcaniination of Water Potassium Chromate Solution (Indicator). Dissolve 10 g. of potassium chromate (K^CrO^) in 100 cc. of distilled water. Nessler's Reagent.* Dissolve 62.5 g. of jootassium iodide in about 250 cc. of distilled water, set aside a few cubic centimeters, and add gradually to the larger part a cold saturated solution of mercuric chloride (of which about 500 cc. will be required) until the mercuric iodide precipitated ceases to redissolve on stirring. When a permanent precipitate is retained, restore the reserved potassium iodide so as to redissolve it, and con- tinue adding mercuric chloride very gradually until a slight precipitate remains undissolved. (The small quantity of j^otas- sium iodide is set aside merely to enable the mixture to be made rapidly without danger of adding an excess of mercury.) Next dissolve 150 g. of potassium hydroxide in 150 cc. distilled water, allow the solution to cool, add it gradually to the above solu- tion, and make up with distilled water to 1 liter. * F. Sutton, Vohunetric Analysis (10th ed.), p. 437. [92] On standing, a brown precipitate is deposited and the solu- tion becomes clear and of a pale greenish-yellow color. It is ready for use as soon as it is completely clear, and should be decanted into a smaller bottle as required. The reagent improves on keeping. Sulphanilic Solution. Dissolve .8 g. of the acid in 100 cc. of distilled water, heating if necessary. Naphthylamine Hydrochloride Solution. Dissolve .8 g. of the salt in 100 cc. of hot distilled water to which 1 cc. of llCl has been added. Filter through bone black, or add bone black to the solution, and decant as needed. Keep away from the light. Phenolsulphonic Acid. Mix 30 g. of phenol with 210 cc. or 370 g. of concentrated H^SO^ in a flask. Place the flask in a water bath so that the surface of the liquid in the flask will be below the water. Heat for six hours at the temperature of boiling water. APPARATUS FOR DESK EQUIPMENT 4 beakers: two 200 cc; two 350 cc. 5 bottles : two 500 cc. ; two 1000 cc. ; one 250 cc. (wide-mouthed). 2 Bunsen burners with 4 ft. of "rubber tubing, 2 burettes, complete. 1 burette holder. 1 condenser with clamp. 1 crucible tongs. 2 crucibles, porcelain, No. 7, with covers. 2 crucibles, Gooch. 1 cylinder, graduated, 50 cc. 1 desiccator, complete. 2 evaporating dishes. No. 4. 25 filter papers, 9 cm. 1 flask, 500 cc. with rubber stop- per for wash bottle. 4 flasks, Erlenmeyer : two 250 cc. ; two 500 cc. 2 flasks, Kj eldahl digestion : 800 cc . 2 flasks, measuring: one 250 cc; one 500 cc. 1 flask, filtering. 5 funnels: four 50mm.; one Gooch. 1 funnel holder, wood. Matches, safety, 1 box. 2 pipettes: one25cc; one 50cc. 2 rings, iron, 3-inch. 4 rods, glass. 1 stand, iron. 6 test tubes, 10 cm. 1 test-tube brush. 1 test-tube rack. 1 thermometer, 100° C. Towel or one-half yard absorption cloth. 2 triangles, pipestem. Tubing, glass, for wash bottle. 4 watch glasses: one 35 mm.; one 50 mm^ ; one 62 mm. ; one 80 mm. [93] INTERNATIONAL ATOMIC WEIGHTS (1916) Abridged Table Element Aluminium Antimony Arsenic . Barium . Bismuth . Boron Bromine . Calcium . Carbon . Chlorine . Chromium Cobalt . Copper . Fluorine Gold . . Hydrogen Iodine Iron . . Lead . . Symbol . Al . Sb . As . Ba . Bi . B . Br . Ca . C . CI . Cr . Co . Cu . F . Au . H . I . Fe . Pb AT03IIC! Weight 27.10 120.20 74.96 137.37 208.00 11.00 79.92 40.07 12.00 35.46 52.00 58.97 63.57 19.00 197.20 1.008 126.92 55.84 207.20 Element Symbol Lithium Li Magnesium .... Mg Manganese .... Mn Mercury Hg Molybdenum , , . Mo Nickel Ni Nitrogen N Oxygen Phosphorus . . . . P Platinum Pt Potassium . . . . K Silicon Si Silver Ag Sodium Na Strontium . . . , Sr Sulphur S Tin Sn Uranium U Zinc Zn Atomic Weight 6.94 24.32 54.93 200.6 96.0 58.68 14.01 16.0 31.04 195.2 39.10 28.30 107.88 23.00 87.63 32.06 118.70 238.20 65.37 [94] ANNOUNCEMENTS RECENT BOOKS ON AGRICULTURE LABORATORY MANUAL OF HORTICULTURE By George W. Hood, University of Nebraska. 234 pages, illustrated, $1.00. Exercises on seeding and seed testing, principal metliods of propa- gation (cutting, budding, grafting, etc.), differentiating between branch and fruit buds of the different fruits, pruning, manufacture of insecticides and fungicides (with something of the chemistry underlying these oper- ations), and analysis and comparative study of the principal fruits, in- cluding the description, identification, and value of some of the most important varieties. MANUAL OF SOIL PHYSICS By Percy B. Barker, University of Missouri, and H. J. Young, University of Nebraska. 44 Exercises, with blank pages for notes, in Biflex Binder, 65 cents. A COMPLETE set of exercises for laboratory work in soils, affording a comprehensive survey of the whole subject. The exercises give the stu- dent an understanding of the origin of the soil ; soil water, its move- ments, use, and conservation ; soil heat ; the texture and structure of the soil ; organic matter, its effect upon the physical condition of the soil and its influence upon productiveness. The study includes exercises in some of the more simple and practical methods of soil examination. A MANUAL OF BACTERIOLOGY For Agricultural and Domestic-Science Students By Howard S. Reed, Agricultural Experiment Station, Riverside, Cal. xii + 179 pages, illustrated, $1.25. Experiments which give the student a first-hand knowledge of the principles and processes concerned in the bacteriology of such subjects as water, soils, milk, plant disease, and yeast and other organisms con- cerned in food fermentations. The manual contains full directions for the preparation of culture media, and for staining, sterilization, and other manipulations. LABORATORY MANUAL OF AGRICULTURAL CHEMISTRY By Charles Cleveland Hedges and William Thoreau Bryant, Texas Agri- cultural and Mechanical College, [hi press] Sixty-three exercises organized under the following heads : Prepar- atory Quantitative Analysis, Analysis of Feedstuffs, Chemical Analysis of Soils, Analysis of Fertilizers, Analysis of Insecticide and Fungicide, Analysis of Milk, Sanitary Examination of Water. GINN AND COMPANY Publishers COUNTRY LIFE EDUCATION SERIES A SERIES of practical texts for the student and the professional farmer, written by experts in their respective lines. These books aim to give a thorough exposition of both the theory and the practice of the various branches of farming and breeding. TYPES AND BREEDS OF FARM ANIMALS By Charles S. Plumb, Professor of Animal Husbandry in the College of Agri- culture, Ohio vState University. 563 pages, illustrated, |i2.oo. PRINCIPLES OF BREEDING Pjy Eugene Daveni'Ort, Dean of the College of Agriculture, Director of the Agricultural Experiment Station, and Professor of Thremmatology in the Univer- sity of Illinois. 727 pages, illustrated, ;?2.5o. FUNGOUS DISEASES OF PLANTS By Benjamin Minge Duggar, in charge of Graduate Laboratorj', Missouri Botanical Garden, St. Louis. 508 pages, illustrated, ^2.00. SOIL FERTILITY AND PERMANENT AGRICULTURE By Cyril George Hopkins, Professor of Agronomy in the University of Illinois ; Chief in Agronomy and Chemistry and Vice Director in the Illinois Agricultural Experiment Station, xxiii + 653 pages, $2.25. PRINCIPLES AND PRACTICE OF POULTRY CULTURE By John H. Robinson, Editor oi Farm-Poit^irj/. xvi + 611 pages, illustrated, J2.50. GARDEN FARMING By Lee Cleveland Cokbett, Horticulturist in the Bureau of Plant Industry, United States Department of Agriculture. 462 pages, illustrated, #2.00. THE APPLE By Albert E. Wilkinson, of the Department of Horticulture in Cornell Uni- versity. 492 pages, illustrateci, ^2.00. EQUIPMENT FOR THE FARM AND THE FARMSTEAD By Harry C. Ramsower, Professor of Agricultural Engineering in Ohio State University. [In />ress] Other z'o/umes in preparation i74z GINN AND COMPANY Publishers BOOKS ON AGRICULTURE SHEEP FEEDING AND FARM MANAGEMENT By D. Howard Doane, Assistant Agriculturist in the Office of Farm Management, United States Department of Agriculture, and Assistant Professor, in charge, of Farm Management in the University of Missouri. i2mo, cloth, 128 pages, illustrated, $1.00. A PRACTICAL manual on the feeding of sheep for market, embodying the experience of successful sheep men and farmers throughout the country. As a textbook for classes in farm management, animal hus- bandry, and agronomy, the book contains much useful material. SOIL PHYSICS LABORATORY MANUAL By J. G. MosiER, Professor of Soil Physics, and A. F. Gustafson, Associate in Soil Physics, in the University of Illinois. 8vo, cloth, 71 pages, illustrated, 60 cents. Practices designed to give the student a knowledge of the physical principles that underlie the common agricultural operations. Many of these practices are here published for the first time. An appendix contains work for advanced students. EXAMINING AND GRADING GRAINS By Thomas L. Lyon, Professor of Soil Technology in the Federal Experimental Station, Cornell University, and Edward G. Montgomery, recently Assistant Pro- fessor of Experimental Agronomy in the University of Nebraska. i2mo, cloth, loi pages, illustrated, 60 cents. Text and exercises providing a thorough drill in the study of the structure and quality of all cereals, in the identification of seeds of the common grasses, millets, and legumes, and in judging the quality of hay of these crops. EXPERIMENTAL DAIRY BACTERIOLOGY By H. L. Russell, Dean of the College of Agriculture, and E. G. Hastings, Asso- ciate Professor of Agricultural Bacteriology in the University of Wisconsin. i2mo, cloth, 147 pages, illustrated, $1.00. A STUDY of the bacteriological processes which must be understood before the relation of microorganisms to dairy processes can be appre- ciated. This guide will be found equally valuable for the student and for the practical worker. PRINCIPLES OF RURAL ECONOMICS By Thomas Nixon Carver, David A. Wells Professor of Political Economy in Harvard University. 8vo, cloth, xx + 386 pages, $1.30. Chapters on the history of agriculture, the factors of agricultural production, farm management, agricultural cooperation, the distribution of the agricultural income, and the problems of rural social life are among those included in this book. GINN AND COMPANY Publishers TEXTBOOKS IN PHYSICS AND CHEMISTRY FOR HIGH SCHOOLS AND COLLEGES PHYSICS Cavanagh, Westcott, and Twining : Physics Laboratory Manual $0.70 Hastings and Beach : Textbook of General Physics 2.75 Higgins : Lessons in Physics 90 Higgins : Simple Experiments in Physics 35 Hill: Essentials of Physics i.io IngersoU and Zobel : Mathematical Theory of Heat Conduction 1.60 Jeans: Theoretical Mechanics 2.50 Miller : Laboratory Physics 2.00 Millikan : Mechanics, Molecular Physics, and Heat 1.50 Millikan and Gale: First Course in Physics (Rev. 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