''MmiiHi^kilMHiii imim^^^ 
 
 
 
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 i^EPARATION OF 
 
 UB STANCES 
 
 CHARLES A. PETERS 
 
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£>tate CoIIese of Agriculture 
 
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Cornell University Library 
 S 585.P4 1919 
 
 The preparation of substances Important 
 
 3 1924 000 880 173 
 
a Cornell University 
 y Library 
 
 The original of tliis bool< is in 
 tine Cornell University Library. 
 
 There are no known copyright restrictions in 
 the United States on the use of the text. 
 
 http://www.archive.org/details/cu31924000880173 
 
The Preparation of Substances 
 Important in Agriculture 
 
 A Laboratory Manual of Synthetic 
 Agricultural Chemistry 
 
 THIRD EDITION 
 
 BY 
 
 CHARLES A. PETERS, Ph.Ei 
 
 Professor of Inorganic and Soil Chemistry 
 
 Department of General and Agricultural Chemistry 
 
 Massachusetts Agricultural College 
 
 NEW YORK 
 JOHN WILEY & SONS, Inc. 
 
 Lokdok: chapman & HALL, LiMirBa> 
 1919 
 
OOPTKlbHT, 1919, 
 
 BY 
 
 C. A. PETERS 
 
 Stanbope jpress 
 
 .GILSON COMPAN? 
 BOSTON, U.S.A. 
 
PREFACE 
 
 It has been the aim in this manual to 
 select substances of agricultural interest, 
 adapt them to laboratory preparation, and 
 explain their chemistry to the best of our 
 present knowledge not overlooking their 
 practical significance. 
 
 The work was at first nothing more than 
 laboratory directions, but the interest of the 
 student gradually required the addition of 
 explanatory matter to such a degree that 
 the emphasis on an accompanying text has 
 been greatly reduced. The method of pres- 
 entation aims to put a few major points 
 before the student and extend the work on 
 such points over so long a time that the 
 student will absorb it. The author feels 
 that when a student, in his earlier years in 
 college, works interestedly for a whole exer- 
 cise around one thing he grasps something 
 while if a dozen important points pass in 
 review during the time he is left in a maze 
 and gets little but technical benefit. While, 
 however, the student is busy on the one 
 
iv Preface 
 
 major piece of work other minor points may 
 be gatherd aroxmd it and are readily ab- 
 sorbd. 
 
 In this collection of agricultm-al material 
 it is ioteresting to note the points that are 
 brot home to the student as the work 
 develops Among these are oxidation, neu- 
 tralization, distillation, crystaUization, sat- 
 uration, chemical calculations, metathesis, 
 mass action, double salts, equilibrium and 
 colloids. By making a process necessary 
 to the production of material the student 
 must grasp it or fail in the experiment. 
 Take the seemingly simple matter of satura- 
 tion. It is but the work of a minute to ex- 
 plain what is meant by the process; the 
 student will give an intelligent expression of 
 the phenomenon in a second minute; how- 
 ever, when in the laboratory he is making a 
 preparation from two others, the success of 
 which depends upon the preparation of two 
 saturated solutions, then, and not until then, 
 does the student understand saturation. 
 
 Only about half of the students entering 
 this college have had farm experience. It is 
 difficult to interest a student in the prepara- 
 tion of superphosphate or Bordeaux mixture 
 unless he knows something of its use, hence 
 the amount of space given in the notes to the 
 p'-actical use of each substance. This does 
 
Preface v 
 
 not lessen the value of the material for 
 chemical instruction but rather enhances 
 it. 
 
 The work was designd for students in an 
 agricultural college who have already had 
 such a knowledge of chemistry as is acquired 
 from a year's work in the high school. It is 
 intended to be done in two or three hour 
 laboratory periods, and furnishes sufficient 
 material for one semester of such exercises. 
 The arrangement of the work is such that a 
 laboratory full of students can all be doing 
 the same thing at the same time without 
 extended waiting; procedures, such as crys- 
 tallization and cooling, taking place in the 
 interim between exercises. With us it is 
 customary to score the preparation when 
 completed, as one would butter or milk, 
 allowing something for quality and some- 
 thing for quantity and to give credit for the 
 exercise only upon completion of the prepara- 
 tion. 
 
 The author is endeted to Professor A. A. 
 Blanchard of the Massachusetts Institute of 
 Technology not only for the development of 
 synthetic method of laboratory work for first 
 year work in college, but also for the privilege 
 to adapt three preparations from his book. 
 Synthetic Inorganic Chemistry, for use in 
 this manual. The three preparations are 
 
vi Preface 
 
 Potassium Nitrate, Copper Sulfate and Lead 
 Nitrate. 
 
 The appreciation of the author is also 
 exprest to Dr. H. S. Adams of New Bruns- 
 wick, N. J., who was associated with this 
 work in its early stages, and to Professor 
 Ernest Anderson of this laboratory who has 
 given this course for several years. Valuable 
 suggestions have come from both these men. 
 
 The first edition was printed privately in 
 1914; the second was again mimeographed 
 in 1916; the third is herewith offerd to those 
 laboratories that have used the manual since 
 1914 and to others that wish to experience 
 the fascination of the synthetic method in 
 agricultural chemistry. 
 
 A few simplified speUings have been used. 
 
 Amherst, Mass., 
 August 1, 1918. 
 
CONTENTS 
 
 Faoz 
 
 Superphosphate 1 
 
 Sulfate op Ammonia 13 
 
 Potassium Nitbatb 20 
 
 Potash Salts 26 
 
 Sulfate of Potash-Magnesia 26 
 
 Sulfate of Potash (High Grade) 28 
 
 Muriate of Potash 30 
 
 Lead Nitrate 38 
 
 Lead Arsenate 41 
 
 Lime-Sulfur 50 
 
 Copper Sulfate 59 
 
 Paris Green 64 
 
 Bordeaux Mixture 68 
 
 Emulsions 78 
 
 vil 
 
The Preparation of Substances 
 Important in Agriculture 
 
 SUPERPHOSPHATE 
 
 Superphosphate is made from the natural 
 rock phosphate, finely ground, and sulfuric 
 acid, the phosphate being acted upon as 
 shown in equation (1) which follows: 
 
 (1) CasPzOs + 2H2SO4 • aq = CaHiP.Os • H2O 
 + 2CaS04 • 2H2O. dih^dio^n 
 
 Calcium sulfate (gypsum) , , ° 
 
 phosphate 
 
 Two-thirds of the calcium of the tricalcium 
 phosphate are replaced by the hydrogen of the 
 acid. Chamber sulfuric acid is used. It is 
 necessary to calculate the actual amount of 
 tricalcium phosphate in the material at hand, 
 the amount of sulfuric acid to act on 200 
 grams of this material and the amount of 
 water that must be added to the sulfuric acid 
 to make it of the proper strength. 
 
 Calculations. — (a) Note the purity of 
 the phosphate rock and calculate the number 
 of grams (a) of the tricalcium phosphate in 
 1 
 
2 Preparation of Substances 
 
 200 grams of the material used. Record the 
 amount. 
 
 (6) From the equation given above cal- 
 culate the number of grams (&) of H2SO4 
 necessary to react with (a) grams of CaaPjOg. 
 Note the number. 
 
 (c) Read the specific gravity of the 
 chamber acid from the spindle floating in the 
 acid on the side shelf. Refer to the table of 
 specific gravity and read off the weight of 
 the H2SO4 in 1 cc. of the chamber acid. 
 Calculate the niunber of cubic centimeters 
 of chamber acid (c) necessary to contain 
 the (6) grams of H2SO4. Record the 
 volum. 
 
 (d) The chamber acid is too strong to be 
 used directly on the rock phosphate and must 
 be diluted until it has the specific gravity 
 1.53. Calculate the number of cubic centi- 
 meters (d) of this acid necessary to contain 
 (6) grams of sulfuric acid. This is the volum 
 to which (c) cubic centimeters of chamber 
 acid should be diluted before the rock phos- 
 phate is added to it. Record the niunber. 
 
 Tabulate the results of the four calcula- 
 tions as indicated below and have them veri- 
 fied by an instructor before proceding with 
 the work. 
 
Superphosphate 3 
 
 (a) Weight of Ca3P208 in 200 grams rock phos- 
 phate, grams. 
 
 (6) Weight of H2S04 required for 200 grams rock 
 phosphate, grams. 
 
 (c) Volimi of chamber acid required for 200 grams 
 
 rock phosphate, cc. 
 
 (d) Volum to which the (c) cc. of chamber acid must 
 
 be diluted, cc. 
 
 Procedure. — Measure out the volum (c) 
 of chamber acid and pour it into (d-c) cubic 
 centimeters of water in a porcelain dish. 
 Weigh out 200 grams of the rock phosphate 
 and stir it slowly into the acid. Let the 
 mixture stay in the evaporating dish until 
 the next exercise. The hydrofluoric acid 
 fumes that arise are to be avoided. 
 
 Notebook; Test for Soluble Phosphates. 
 — Shake a little of the superphosphate with 
 water, filter the solution, add to the filtrate a 
 solution of ammonium molj^bdate and warm 
 the liquid gently in a test tube. If the yellow 
 precipitate of ammonium phosphomolybdate 
 does not form after a few seconds its ap- 
 pearance may be hastend by adding a gram 
 or two of solid ammonium nitrate. The 
 addition of ammonium hydroxid foUowd 
 by nitric acid will accomphsh the same result 
 including the heating; when this is done the 
 solution must be left acidic with nitric acid. 
 
 If some of the natural rock phosphate is 
 
4 Preparation of Substances 
 
 treated similarly it will be seen that only an 
 inappreciable amount of phosphate dissolvs 
 in water. 
 
 Test for Lime. — Dissolv some of the 
 superphosphate in water and filter as before. 
 To the clear filtrate add a solution of oxalic 
 acid or ammonimn oxalate. The white 
 precipitate that forms is calcium oxalate 
 which shows the presence of calcium com- 
 pounds in solution. 
 
 NOTES 
 
 The Beaum6 hydrometer is an instrument 
 for determining density that has wide indus- 
 trial use. It is, however, unscientific as it has 
 
 SuLPUKic Acid. Specific Gravitt op Aqueous Solu- 
 tions 
 
 Degrees B6. 
 
 Sp.Er. 
 
 1 cc. contains grams 
 H^SO,. 
 
 50.0 
 
 1.53 
 
 0.957 
 
 50.6 
 
 1.54 
 
 0.977 
 
 51.2 
 
 1.55 
 
 0.996 
 
 52.8 
 
 1.56 
 
 1.015 
 
 52.4 
 
 1.57 
 
 1.035 
 
 53.0 
 
 1.58 
 
 1.054 
 
 53.6 
 
 1.59 
 
 1.075 
 
 54.1 
 
 1.60 
 
 1.096 
 
 54.7 
 
 1.61 
 
 1.118 
 
 55.2 
 
 1.62 
 
 1.139 
 
 two separate scales, one for liquids heavier 
 than water and me for liquids lighter than 
 water, the two having no relation. Further, 
 
Superphosphate 5 
 
 neither scale bears any relation to true specific 
 gravity. See Thorp, Inorganic Chemical 
 Preparations, p. 32. 
 
 The solubility of the natural rock phosphate, 
 or floats, in a short time under most soil 
 conditions, is so slight that it has become a 
 common practise to "dissolv" it, that is, 
 to convert it into the water-soluble acid 
 phosphate having only one-third of the ori- 
 ginal amount of calcium. Under ordinary 
 business conditions one-half of all the sul- 
 furic acid made in this country is used in this 
 process. 
 
 Tricalcium phosphate, whether as rock 
 phosphate, bones or the mineral apatite, is 
 always associated with fluorin and generally 
 chlorin. In addition rock phosphate is gen- 
 erally associated with calcimn and magnesium 
 carbonates and sometimes iron and alumi- 
 num phosphates so that the reactions which 
 take place with the sulfuric acid are more 
 complicated than that given at the beginning 
 of this exercise. The following are the more 
 important : 
 
 (2) 2Ca3P208 • Ca^FPO* -1- 7H2SO4 • aq = 
 
 3CaH4P208 • H2O + 7CaS04 • 2H2O 
 -I-2HF. 
 
 (3) CaCOa + H2SO4 • aq = CaSOi • 2H2O 
 
 + CO2. 
 
 (4) 2AIPO4 + 3H2SO -aq = 2H3PO, -h 
 
 2A1(S04)3 • I8H2O. 
 
6 Preparation of Substances 
 
 The fertilizer manufacturer must determin 
 the exact amount of sulfuric acid to be used 
 for each substance present in the ground rock. 
 The student is not askt to do this. How- 
 ever, to insure the presence of sufficient acid 
 to combine with all these substances, the 
 calcium phosphate content of the floats as 
 given to the student is increased 5 to 10 per 
 cent. 
 
 The strength of sulfiu-ic acid used will vary- 
 according to the source and composition of 
 the natural rock. If large amounts of cal- 
 cium compounds other than phosphate are 
 present a more dilute acid is used so that 
 there will be water enuf to hydrate the 
 land plaster (calcium sulfate) formd in the 
 reaction. 
 
 The calcimn fluorid present reacts with 
 the sulfuric acid producing the disagreeable 
 poisoiious hydrofluoric acid gas. Avoid 
 breathing the fumes from the mixtiu'e. 
 
 Notice that after standing the mass crum- 
 bles easily in the hand. After storing several 
 weeks, during which time the action of the 
 sulfuric acid continues until the insoluble 
 phosphates are reduced to a fraction of one 
 per cent, the material is ground, if necessary, 
 and put on the market or used as a "base," 
 i.e., one of the substances from which fer- 
 tilizers are made. 
 
Superphosphate 7 
 
 9 
 
 There being several calcium compounds in 
 the rock phosphate which all appear finally 
 as hydrated calcium sulfate (gypsum) it is 
 not strange that the resulting superphos- 
 phate is composed of. 60-70 per cent of 
 gypsum. From this it is easy to see why 
 superphosphate contains only 14 to 16 per 
 cent of phosphoric acid (P2O6). 
 
 The deposits of rock phosphate at present 
 being extensivly workt are foimd in South 
 Carolina, Florida and Tennessee. The larg- 
 est and most newly discoverd deposits are 
 in Idaho, Utah and Wyoming. 
 
 A good grade of groimd rock carries 65 per 
 cent of tricalcium phosphate and the material 
 not infrequently nms over 80 per cent. In- 
 ferior rock containing a few per cent of 
 phosphoric acid and mixt with carbonate 
 of lime is abundant, but it is not economical 
 to ship this any great distance or treat it 
 with suKuric acid. 
 
 The use of " raw rock " vs. "dissolvd rock " 
 is a much discust question in agriculture. 
 Thru the East, on hght soils and for intensiv 
 cultivation, the dissolvd rock is used ex- 
 clusivly; for some of the heavy soils of the 
 West raw rock is recommended in connection 
 with decaying organic matter. According to 
 Professor Hopkins of Illinois the raw rock in 
 a heavy soU is converted to dissolvd rock 
 
8 Preparation of Substances 
 
 by acid in the soil, the steps in the process 
 being first, the production of ammonium 
 carbonate, (NH4)2C03, from the amino 
 groups, — NH2, in the plant; second, the 
 oxidation of ammonia to nitrous acid by- 
 bacteria; third, the conversion of the raw 
 rock to dissolvd rock by the action of the 
 nitrous acid which may be represented by 
 the equation, 
 
 CasPjOs + 4HNO2 + H2O = CaHiPaOs • H2O 
 
 + 2Ca(N02)2; 
 
 and fourth, the oxidation of the calcium 
 nitrite, Ca(N02)2, to calcium nitrate, 
 Ca(N03)2, by the action of bacteria. Both 
 the acid phosphate and the calcium nitrate 
 resulting from the action are available to the 
 plants for food. Naturally the plants richest 
 in amino groups, such as clovers and alfalfa, 
 are most desirable to plow under with the 
 raw rock. This action of the dissolving of 
 raw rock by acid in the soil has been demon- 
 strated by Professor Hopkins in the labora- 
 tory, but others deny that it actually takes 
 place in the soil. 
 
 As a general conclusion it may be said 
 that all the phosphorus of acid phosphate 
 is immediately available to plants while only 
 a small amount of the phosphorus in the 
 raw rock is available during one growing 
 
Superphosphate 9 
 
 season; however, the phosphorus in raw rock 
 continues to become available, year by year, 
 until the total amount is drawn upon. For 
 cultural pm-poses the important question is 
 whether or not there is sufficient phosphorus 
 available in one season for the crop in ques- 
 tion; this, of course, depends upon many 
 factors which cannot be gone into here. 
 
 Analysis of Rock Phosphate. — An analy- 
 sis of Tennessee rock phosphate taken from 
 the American FertiUzer Handbook for 1908 
 is here given: 
 
 Per cent 
 
 Moisture (loss on drying) 0.87 
 
 Combined water and organic~matter ^ 
 
 (loss on ignition) 1 . 53 
 
 Sand and insoluble matter 2.76~\ 
 
 Ferric oxid, FejOs 2.40 ) ^^■'^ 
 
 Alumina, AI2O3 1 . 99 \ u /^ 
 
 Lime, CaO 49.07 / 
 
 Magnesia, MgO 0. 24 
 
 Carbon dioxid, CO2 1.08 v 
 
 Fluorin, F 2.98 
 
 Sulfur trioxid, SO3 
 
 Phosphoric acid, PzOe 35 . 
 
 99757 
 
 X^^ 
 
 1.03 
 
 35.62_j 
 
 When these figures are put together in an 
 attempt to show the substances that existed 
 in the original rock the data shown under 
 colum (a) is obtaind. The composition of 
 another sample of rock phosphate is shown 
 
10 
 
 Preparation of Substances 
 
 in colum (6). It is noticeable that many 
 ■of the constituents vary widely ia quantity. 
 
 (a) 
 
 m 
 
 Moisture and organic matter 
 
 Phosphate of lime, CaaPjOj 
 
 Phosphates of iron and aluminium 
 
 FeP04, AIPO4 
 
 Carbonate of lime, CaCOs 
 
 Carbonate of magnesia, MgCOs . . . 
 
 Fluorid of lime, CaFj 
 
 Iron pyrites, FeSa 
 
 Iron oxid, FezOs 
 
 Alumina, AUO 
 
 Sand and silicious matter 
 
 Per cent 
 
 2.30 
 
 77.76 
 
 Per cent 
 
 1.00 
 55.00 
 
 
 6.50 
 
 4.43 
 
 3.50 
 
 0.50 
 
 0.75 
 
 6.11 
 
 2.25 
 
 0.77 
 
 
 1.88 
 
 
 1.99 
 
 
 2.76 
 
 28.00 
 
 98.50 
 
 100.00 
 
 The natural sources of phosphorus are 
 the mineral apatite, or phosphorite, which is 
 an ingredient of nearly all soils. It has the 
 same formula as the raw rock phosphate but 
 is entirely different in appearance. Immense 
 deposits of this mineral are localized in 
 Quebec and Ontario, Canada. 
 
 QUESTIONS 
 (To be answerd in the notebook.) 
 
 1. What is the per cent of P2O5 in calcium dihy- 
 drogen phosphate? 
 
 2. Supposing equation (2) to represent all that 
 happens when sulfuric acid acts upon rock phosphate, 
 calculate the per cent of hydrated acid phosphate and 
 the per cent of hydrated calcium sulfate in the« 
 mixture. 
 
Superphosphate 1 1 
 
 3. Again supposing equation (2) to represent what 
 happens when superphosphate is made, what is the 
 highest per cent of PjOs it is possible to have in super- 
 phosphates? 
 
 4. What per csnt of P2OB is present in ordinary 
 superphosphat3? Name the substance represented by 
 the symbol P2O6. 
 
 5. What per cent of tricalcium phosphate is found 
 in natural phosphates? 
 
 6. Which would use the more sulfuric acid, a raw 
 rock carrying 60 per cent tricalcium phosphate and 
 6 per cent calcium carbonate or a rock carrying 55 per 
 cent tricalcium phosphate and 10 per cent calcium 
 carbonate? 
 
 7. What gases escape during the action of the sul- 
 furic acid on the rock phosphate? Which is poison- 
 ous? 
 
 8. Whkt compounds are found in the raw rock? 
 In the dissolvd rock? The student cannot give, for 
 example, calcium oxide, CaO, or phosphorus pentoxid, 
 P2O6, as compounds present in either the raw or dis- 
 solvd rock altho such compounds are well known and 
 moreover are represented in the table of analysis. In 
 the raw and dissolvd rocks the lime and the phosphoric 
 acid are in combination and the student should give, 
 as well as he can, the actual lime and phosphorus com- 
 pounds that are present. 
 
 9. How could phosphoric acid be made by a process 
 similar to that for making superphosphate? 
 
 10. How could the acid phosphate be made into a 
 neutral salt? How would the solubility change? 
 
 11. Write a ssrmbol for another acid calcium phos- 
 phate; name the compound. 
 
 12. How is the test made for soluble phosphate? 
 
 13. Describe the test for lime. 
 
12 Preparation of Substances 
 
 14. How many grams of actual sulfuric acid in a 
 liter of dilute acid of a density of 51.5 B6.? 
 
 15. Where are the phosphate deposits in this 
 country? 
 
 16. Where should a plant for tnaking superphosphate 
 be located? Near the phosphate mines or near the 
 farmer? Give reasons for the answer. 
 
 17. What is meant by the terms, " raw rook," " dis- 
 solvd rock " ? 
 
 18. Where is the use of dissolvd rock recommended? 
 
 19. Is calcium sulfate soluble in water? (See text 
 under calcium compounds.) 
 
 20. Write symbols for limestone; slaked lime; quick- 
 lime. 
 
SULFATE OF AMMONIA 
 
 Sulfate of ammonia is made by distilling 
 the ammonia from the gas liquor into sulfuric 
 acid. The first problem is to find out, ap- 
 proximately, how much gas liquor should be 
 used to neutralize a convenient amount, say 
 15 cc, of chamber sulfuric acid. 
 
 Calculations. — Read the specific gravity 
 spindle floating in the sulfuric acid and cal- 
 culate, from the table on page 4, the amount 
 of actual sulfuric acid in the 15 cc. to be used. 
 From the equation, 
 
 2NH3 + H2SO4 = (NH4)2S04, 
 
 find out how many grams of ammonia are 
 necessary to unite with this amount of acid. 
 
 Ascertain the strength of the gas liquor 
 and compute the voliun necessary to con- 
 tain the desired amount of ammonia. 
 
 For example: If 30 grams of ammonia 
 (NH3) are desired and the gas liquor is 8 per 
 
 cent ammonia, there will be — -- = 125 grams 
 
 0.08 
 
 required. The density of gas liquor being 
 
 nearly the same as water, 125 cc. in place 
 
 of 125 grams may be considerd the correct 
 
 amount. 
 
 13 
 
14 Preparation of Substances 
 
 Enter the results as given below and have 
 them verified by an instructor. 
 
 Amount of actual acid in 15 cc. of chamber acid, . .grams. 
 
 Amount of ammonia equivalent to the acid, grams. 
 
 Volum of gas liquor to contain the ammonia, cc. 
 
 Procedure — Arrange a distilling appa- 
 ratus consisting of a flask of a capacity of 
 from 500 to 1000 cc. carrying a two-hole rub- 
 ber stopper. Thru one hole put a thistle 
 tube reaching to within 1 cm. of the bottom 
 of the flask, thru the other hole insert a 
 bent tube carrying a one-hole stopper fitted 
 to a condenser. Put 15 cc. of chamber sul- 
 furic acid into a 250-cc. gas bottle and adjust 
 to the delivery tube of the condenser so that 
 the bottle rests on the desk and the deUvery 
 tube dips under the acid. Draw from 10 
 to 50 cc. more than the calculated amount 
 of gas liquor, — the amount depending 
 on its strength, — pour it thru the thistle 
 tube into the flask and begin heating. As 
 soon as the distillation is well under way, 
 look for the deposit of ammonium carbonate 
 in the condenser. If any appears — as it 
 always does — it will be necessary to break 
 up this conipound in the flask by adding lime. 
 To do this make a paste of 10 to 15 grams of 
 lime and 50 to 75 cc. of water and pour 
 the mixture, which is milk of lime, thru a 
 
Sulfate of Ammonia 15 
 
 piece of cheese cloth placed over the thistle 
 tube. The reaction results in the precipi- 
 tation of calcium carbonate in the flask, 
 
 CaOzHa + (NH4)2C03 = CaCOs + 2NH3 
 + 2H2O, 
 
 and the liberation of ammonia which vola- 
 tilizes faster than the ammonium carbonate. 
 
 When the sulfuric acid is entirely neutra- 
 hzed, as is shown by the action of litmus 
 paper or a decided change in the appearance 
 of the distillate, disconnect the apparatus. 
 Filter the solution of ammonimn sulfate in 
 the gas bottle if tarry matter has collected in 
 it, first making sure that aU the ammonium 
 sulfate is in solution, and evaporate the clear 
 filtrate in a porcelain dish to the point of 
 crysta'Uzation. 
 
 Cool the mixture, bring the mass of crystals 
 on a paper filter and allow them to drain and 
 further dry by pressing between filter papers. 
 Weigh the crystals and enter the amount in 
 the notebook. 
 
 To become familiar with the properties of 
 the salt, heat a little in a dry test tube and 
 hold a piece of moistend red litmus in the 
 mouth of the tube. Ammonium sulfate 
 melts at 140°; at 280° it decomposes, losing 
 ammonia and leaving behind ammonium 
 acid sulfate. 
 
16 Preparation of Substances 
 
 NOTES 
 
 The time of the student is such an impor- 
 tant factor that considerable more than the 
 required amount of ammonia is recommended 
 for use. This obviates waiting for all the 
 ammonia to be driven off and also saves 
 evaporation of the increased amount of water 
 which would distil over. Of course a waste 
 of ammonia results. Industrially such a 
 waste of ammonia would not be allowd. 
 
 If the evaporation proc"edes beyond a cer- 
 tain point the mass upon cooling will be solid 
 salt. In this case filtering and drying are 
 unnecessary. The danger in using this 
 quicker method of drying lies in the fact that 
 the solution of ammoniiun sulfate in water 
 upon being heated to dryness passes over into 
 a clear molten anhydrous mass so quickly that 
 the change may not be noticed. Heating this 
 molten anhydrous mass results in the decom- 
 position of the salt as explaind in a previous 
 paragraf. 
 
 In the manufacture of coal gas, by heating 
 soft coal much of the nitrogen present is 
 combined with hydrogen forming ammonia. 
 Some of the oxygen that enters the retorts as 
 they are charged combines with the carbon 
 forming carbon dioxid. This weak acid, 
 carbonic acid, unites with the weak base 
 
Sulfate of Ammonia 17 
 
 ammonia and forms the volatil salt, am- 
 monium carbonate. Part of the process of 
 purification of coal gas consists in washing 
 out the ammonia and ammonium carbonate 
 in water. This wash is known as dilute gas 
 liquor (2| oz. of ammonia to the gallon) 
 and may be concentrated by distillation. 
 Such a concentrated product contains the 
 equivalent of about 18 oz. of ammonia 
 (NH3) per gallon of liquid. 
 
 The United States normally produces 
 about 300,000 tons of sulfate of ammonia 
 annually. Since the war the production has 
 doubled and is constantly increasing. It is a 
 plant food furnishing both nitrogen and sulfur; 
 excessive use as a fertilizer, however, may 
 deplete the soil of its calcium. 
 
 The milk of lime which decomposes the 
 ammonimn carbonate must be straind or 
 the lumps wUl clog the thistle tube. In 
 place of the procedure described the mixture 
 may be allowd to settle four or five seconds 
 after stirring and the upper portion pourd 
 thru the thistle tube leaving the lumps be- 
 hind on the bottom of the container. 
 
 Should the process of distillation be inter- 
 rupted before bhe sulfuric acid is neutral- 
 ized the product will be a mixture of the 
 neutral and acid ammonium sulfates. 
 
 Sometimes the tarry materials exist in the 
 
18 Preparation of Substances 
 
 neutralized solution in colloidal condition 
 and are not flocculated until the ammonium 
 sulfate solution has become more concen- 
 trated. Should flocculation occur during the 
 course of evaporation the tarry substance 
 then may be filterd out. It is this material 
 left in the preparation which gives the pecu- 
 liar brownish color to commercial sulfate of 
 ammonia. 
 
 The point of crystallization is determind 
 by blowing across the surface of the hot 
 liquid. When a sciun appears at once the 
 evaporation by flame may cease. 
 
 QUESTIONS 
 (To be answerd in the notebook.) 
 
 1. How many grams of ammonia in 2 kUos of a solu- 
 tion containing 28.33%? 
 
 2. How much ammonia in 250 cc. of a solution of a 
 sp. gr. of 0.970 containing 7.31% of NH3? 
 
 3. How many tons of ammonium sulfate could be 
 made from a tank car of concentrated ammonia con- 
 taining 5000 gaUons of 14% NH3? The weight of a 
 gallon may be taken as 8 pounds. What is this worth 
 at $60.00 per ton? 
 
 4. What is the per cent of ammonia in ammonium 
 sulfate? 
 
 5. Write the reactions, giving] the names, showing 
 how two different salts may be made by putting to- 
 gether ammonium hydroxid and sulfuric acid. 
 
 6. What other substances in addition to ammonia 
 are produced by distilling soft coal? 
 
Sulfate of Ammonia 19 
 
 7. What is the use of the lime in the distillation of 
 gas liquor? 
 
 8. Explain the presence of ammonium carbonate in 
 gas liquor. 
 
 9. Why is commercial sulfate of ammonia brown? 
 10. Why does a brown substance sometimes settle 
 
 out during the concentration of the ammonium sul- 
 fate solution? 
 
POTASSIUM NITRATE 
 
 Potassium nitrate is made by metathesis of 
 potassium chlorid and sodium nitrate, taking 
 advantage of the different solubilities of the 
 four possible salts in hot and cold water. 
 
 Procedure. — Heat 200 cc. of water in a 
 porcelain dish and when hot add 100 grams 
 of sodium nitrate and 90 grams of muriate 
 of potash. Evaporate until the volum is 
 reduced to about 100 cc, and filter off the 
 sodium chlorid, sand and dirt thru a 
 carefully prepared Witt filter. Throw away 
 the residue on the filter, and cool the fil- 
 trate until the crystals of potassium nitrate 
 appear in quantity. 
 
 Some care is required to judge when the solution is 
 boild down to one-half its original volum. If it is 
 filterd too soon, ia which case few or no potassium 
 nitrate crystals separate out of the filtrate on cooUng, 
 the filtrate should be evaporated further and again 
 filterd to remove the sodium chlorid which will sepa- 
 rate as solution boils away. If the mixture boils too 
 long before filtering the crystaUization of the potas- 
 sium nitrate will take place ia the funnel stem and 
 clog the filter. In such a case the whole mass should be 
 put back in the dish with about 50 cc. more of water 
 and reheated. It sometimes aids the filtering to warm 
 20 
 
Potassium Nitrate 21 
 
 the funnel just previous to using. This can be done 
 by pouiiag a test tube of hot water thru the funnel. 
 Empty out the water. 
 
 Filter off the crystals of potassium nitrate 
 when the solution is cold; set the crystals 
 aside. Evaporate the filtrate again until 
 reduced about one-half its volum, or imtil 
 crystals of sodium chlorid appear in quan- 
 tity, filter thru the Witt plate, rejecting 
 the sodium chlorid on the filter and cool the 
 filtrate to the lowest point possible to crystal- 
 lize the potassium nitrate. Filter off this 
 crop of potassiiim nitrate, and put with 
 the quantity previously obtaind. As both 
 crops of crystals came from a solution 
 saturated with sodium chlorid as well as 
 potassium nitrate and as sodium chlorid is 
 slightly less soluble (4 grams per 100 cc.) in 
 cold water than hot some sodium chlorid 
 crystals will have formd on the nitrate. To 
 get rid of these, dissolv the nitrate in hot 
 water, using about 50 cc. or less for every 
 100 grams of crystals, and cool in cold water 
 as was done before. Filter. The mother 
 Hquor should contain all the sodium chlorid 
 and if the mother liquor adhering to the 
 crystals on the filter can be replaced by water 
 before they dry out the product will be free 
 from chlorid. Wash the crystals with cold 
 water, a drop at a time, until a few of the 
 
22 Preparation of Substances 
 
 crystals in water in a test tube give no test 
 for chlorin ions when a soluble silver salt is 
 added. 
 
 The microscope can be used to advantage here. 
 If square right angle blocks (sodium chlorid) are 
 formd adhering to the long nitrate bars the crystals 
 will have to be redissolvd. If no bloclcs of sodium 
 chlorid are seen it may be takeii for granted that 
 purification may be brot about by continued, drop by 
 drop, washing with cold water. The crystals when 
 pure may be dried by pressing between filter paper or 
 by allowing to stand over one exercise. 
 
 NOTES 
 
 The Witt filter consists of a perforated 
 porcelain disk in a funnel fitted into a 
 heavy glass suction flask, having connection 
 with an aspirator. It is a convenient 
 and rapid means of filtering when prop- 
 erly used. The student should be supplied 
 with paper filters of a diameter about one 
 centimeter greater than that of the porcelain 
 plate. Should the plates become chipt they 
 can still be used if a small piece of filter 
 paper is torn off and laid over the damaged 
 place. Unless the chipt place is so closed 
 pressure will make a hole in the filter paper 
 allowing the precipitate to pass thru into the 
 filtrate. 
 
 The flask should be supplied with rubber 
 tubing of ordinary thickness, not pressure 
 
Potassium Nitrate 23 
 
 tubing, and a pinchcock to help regulate the 
 pressure. The proper use consists in ar- 
 ranging the apparatus, starting the pump, 
 emptying the mixture on the filter, closing 
 the rubber tube with the pinchcock and 
 then shutting off the water. As the vacuum 
 in the flask is relieved it can be increased by 
 starting the pump and momentarily opening 
 the pinchcock. Too much use of the pump 
 is to be avoided. 
 
 It is only in exceptional cases where potas- 
 sium nitrate is of agricultural importance. 
 True, it contains both potash and nitrogen in 
 one compoimd and therefore in concentrated 
 form, but these substances are as well sup- 
 pUed in agricultm-e by the sodium nitrate and 
 the potassiimi chlorid separately. In isolated 
 locaUties where the freight rate is exception- 
 ally high it is possible that the cost of manu- 
 facture of potassium nitrate would be less 
 than the freight on the sodium chlorid elimi- 
 nated in the process. In such a locality it 
 might be desirable to use potassium nitrate 
 for fertilizer. 
 
 The classic use of potassium nitrate is for 
 black powder. Sodium nitrate being hygro- 
 scopic does not make a powder suitable for 
 use in fire arms; however a coarse blasting 
 powder is made from it, the large grains 
 being glazed to keep out moisture. 
 
24 Preparation of Substances 
 
 When the two salts are dissolve! in water 
 all four ions, K+, Na+, CI", NOs", exist as 
 well as all possible combinations of these. 
 As water evaporates the least soluble com- 
 bination of ions, sodium chlorid, will come out 
 of solution first, so that the reaction precedes 
 by metathesis, 
 
 KCl + NaNOs = KNO3 + NaCl. 
 
 It is to be noted in this reaction that as the 
 Na and CI ions form the least soluble sub- 
 stance so do the two ions remaining after 
 these unite, K+ and NO3", form the most 
 soluble combination. Either circumstance 
 would be sufficient to determin the direc- 
 tion of the reaction. 
 
 The change in solubility of the potassium 
 nitrate in hot and cold solution is very great. 
 When hot potassium nitrate is many times 
 more soluble than sodiirai chlorid; at 33°, 
 their molar solubilities are equal and below 
 that temperatm-e potassium nitrate is less 
 soluble, being about one-half that of sodium 
 chlorid at 10°. 
 
 A graphic representation of the solubilities 
 of these salts will be of aid to the student. 
 Such figures are found in the following texts : 
 Kahlenberg, p. 435; Alexander Smith, p. 131; 
 Blanchard, Synthetic Inorganic Chemistry, 
 p. 26. 
 
Potassium Nitrate 25 
 
 QUESTIONS 
 (To be answerd in the notebook.) 
 
 1. How many grams of potassium chlorid are 
 required to unite with 100 grams of sodium nitrate? 
 Keep one decimal piece in the figure. 
 
 2. Of what use is potassium nitrate? 
 
 3. Write the symbols of the four salts that exist 
 in solution at the beginning of this experiment. Write 
 symbols for the ions. 
 
 4. What is the solubility of potassium nitrate at 
 100°? of sodium chlorid? 
 
 5. What is the solubility of these two salts at room 
 temperatiu'e or the temperature of hydrant water? 
 State the exact temperature selected. 
 
 6. Describe a test for chlorid ions. 
 
 7. Describe the crystals of potassiiun nitrate; of 
 sodium chlorid. 
 
 8. When might it be desirable to use potassium 
 nitrate as a fertilizer? 
 
 9. Where is sodium nitrate found? What is its 
 common name? Why is it not used for making gun 
 powder? 
 
 10. If one kilo of a solution of salt saturated at 100° 
 is coold to 10° how many grams of salt will separate 
 out? Consult the cjafs in one of the references given 
 in the last paragraf before the question. 
 
POTASH SALTS 
 
 PART I 
 SULFATE OF POTASH-MAGNESIA 
 
 The sulfate of potash-magnesia is made 
 according to the equation, 
 
 3KC1 + 2MgS04 • H2O + IIH2O = K2SO4 • 
 MgS04 • 6H2O + KCl • MgCl2 • 6H2O, 
 
 by mixing saturated brines of potassiima 
 chijorid and magnesium sulfate. 
 
 Procedure. — Weigh out 60 grams of 
 muriate of potash and add it, as fast as it will 
 dissolv, to about 100 cc. of boiling water. 
 Making sure that all the salt is in solution 
 filter the mixtm-e while hot through a Witt 
 plate to separate the iron oxid, dirt and sand. 
 Put the filtrate in a beaker, keep the liquid 
 at. boiling temperatiu*e, and concentrate the 
 brine until crystals of potassium chlorid begin 
 to appear on the surface, showing that the 
 solution is satiu-ated at that temperatm-e. 
 
 While the foregoing is in operation weigh 
 out 100 grams of kieserit and dissolv it in 
 about 75 cc. of boiling water, adding the 
 salt slowly. In case it does not all go into 
 solution, indicated by a residue of salt on the 
 26 
 
Sulfate of Potash-Magnesia 27 
 
 bottom of the beaker and a scum on the 
 surface of the Uquid, add 10 or 20 cc. more 
 of water and heat, repeating the addition of 
 small amounts of water and heating, if 
 necessary, until the magnesium sulfate is 
 all dissolvd. Filter, using the Witt plate, 
 and concentrate the clear filtrate until the 
 hquid is saturated as indicated by the for- 
 mation of a scum on the surface. Mix 
 the two hot saturated salt solutions and set 
 the mixture aside for at least twelve hours. 
 Both the solutions must be saturated upon 
 mixing or the experiment will be a failure. 
 The crystals that begin to form upon put- 
 ting the solutions together and which further 
 separate on cooUng are the double sulfates of 
 potassium and magnesium, K2SO4 • MgS04- 
 6H2O, sometimes cald the sulfate of potash- 
 magnesia. 
 
 After the mixture has stood, filter off the 
 crystals, drain them well on a Witt plate, 
 transfer them to a paper and weigh. Save 
 the filtrate which contains a solution of arti- 
 ficial carnallit. 
 
 The crystals of double sulfate may be dried 
 in a few horn's by spreading on paper when 
 the exact weight may be obtaind or the 
 approximate weight may be had at once, 
 assuming that 5 to 6 per cent of the weight is 
 water adhering to the crystals. 
 
PART II 
 SULFATE OF POTASH, HIGH-GRADE 
 
 It is customary to make sulfate of potash 
 from the double salt by adding sufficient 
 potassium chlorid to carry on the following 
 reaction: 
 
 3KC1 + K2SO1 . MgS04 • 6H2O = 2K2SO4 + 
 KCl • MgCU . 6H2O. 
 
 Procedure. — Calculate the amount of 
 potassium chlorid necessary to react with 
 the amount of double salt at hand, and weigh 
 out enuf muriate of potash to furnish this 
 amoimt of actual salt, allowing for impiu-ity. 
 Heat the necessary amount of water to boil- 
 ing, dissolv the salt, filter off the dirt on a Witt 
 plate, and heat the filtrate until it is satu- 
 rated all as previously described under sul- 
 fate of potash-magnesia. 
 
 Add the sulfate of potash-magnesia to 
 boiling water, using 100 cc. for every 80 grams 
 of salt, and put this mixture with the hot 
 saturated solution of the chlorid. Potas- 
 sium sulfate begins to separate at once and 
 continues to come out on cooling. After 
 standing 24 hours the salt may be filterd off 
 
 28 
 
Sulfate of Potash, High-Grade 29 
 
 and dried in the air. Record the weight of 
 dried salt. 
 
 The filtrate, which should be saved, also 
 contains the double chlorids of potassium and 
 magnesium (carnallit) similar to that obtaind 
 under Part I. 
 
PART III 
 MURIATE OF POTASH 
 
 Procedure. — Put the two filtrates contain- 
 ing the artificial carnaUit brine together and 
 evaporate the water until the hollow octahe- 
 dral crystals of potassium chlorid appear in 
 abundance. The decomposition of the car- 
 nalUt yields some potassium chlorid which 
 crystalhzes out first; this is rapidly foUowd 
 by the clear dense crystals of the carnallit 
 itseK. The latter may compose the major 
 portion of the precipitate. If too much or 
 nearly all the water is evaporated off mag- 
 nesium chlorid will separate out making the 
 product deliquescent. The crystals may be 
 separated from the magnesium chlorid brine 
 by the use of the Witt plate. The filtrate 
 containing the solution of magnesium chlorid 
 may be thrown away. 
 
 The two salts, sulfate of potash and muri- 
 ate of potash, dried and weighd, are handed 
 in separately. 
 
 NOTES 
 
 The amount of water used to dissolv 
 the salts may be quite a little more than 
 would be calculated from the solubility 
 
 30 
 
Muriate of Potash 31 
 
 tables. There are several reasons for this. 
 First, there are impurities present which if 
 they contain an ion in common with the 
 principal salt may necessitate the use of more 
 water. To illustrate this suppose there are 
 10 grams of sodium chlorid in every 50 grams 
 of the crude potassium chlorid (a chlorid ion 
 in common), then it is necessary to furnish 
 water for the sodium chlorid as well as for 
 the potassiiim chlorid; while if 10 grams of 
 calcium nitrate were present (no common ion : 
 K+, Ca+, NOs", Cl~) this substance would 
 dissolv in the solution already saturated with 
 potassium chlorid. Second, sufficient water 
 should be present so that the solutions may 
 be filterd before they approach satxiration; 
 otherwise the crystalHzation that results on 
 cooling clogs the filter and causes delay. 
 
 In filtering all such mixtm-es which con- 
 tain fine sediment, first allow them to settle 
 and bring the solid matter onto the filter 
 only at the end of the operation after the 
 clear liquid has past thru the filter. 
 
 Kieserit, the magnesium sulfate with one 
 molecule of water, is the salt that has sepa- 
 rated out in the German deposits. Ordinarily 
 from water the heptahydrate, MgS04 • 7H2O, 
 separates out. Epsom salts, the hepta- 
 hydrate, are made from kieserit by dissolving 
 kieserit and allowing the salt to crystallize. 
 
32 Preparation of Substances 
 
 In all this work it is the object to precipi- 
 tate a salt by mixing two hot saturated solu- 
 tions. The appearance of crystals or a scum 
 (film of fine crystals) on the surface may be 
 taken as an indication of saturation. Mixing 
 solutions which are not saturated may result 
 in large loss of the desired substance. Often 
 the addition or withdrawal of one cubic 
 centimeter of water is all that is necessary 
 to produce the condition sought. 
 
 In dissolving the double sulfate in water the 
 salt may not appear to dissolv completely. 
 This is immaterial as the residue is potassium 
 sulfate, the same as the desired product. It 
 is possible to crystallize out potassium sul- 
 fate by evaporating the solution of potash- 
 magnesia sulfate. 
 
 Muriate of potash is sold in three grades 
 containing 80, 95 and 98 per cent, respec- 
 tively. The material containing 80 per cent 
 potassium chlorid is the grade mostly used 
 for fertilizers. This is produced industrially 
 by treating the raw salts as they are mined 
 with a hot saturated solution of magnesium 
 chlorid such as is thrown away at the end 
 of this experiment. The resulting hot solu- 
 tion is coold in cement tanks and the crude 
 muriate of potash separates out. The crys- 
 tals are centrifuged and further dried over a 
 fire in sloping pans about 10 X 60 feet in 
 
Muriate of Potash 33 
 
 size. Bromin is obtaind from the magne- 
 sium bromid in the spent magnesixma chlorid 
 brine. 
 
 In former years one of the salts mined 
 extensively in Germany was carnaUit in a high 
 degree of purity. Such deposits are no longer 
 available, and in its place the carnaUit brine 
 appears from which the high grade, 96 to 98 
 per cent, muriate of potash is made by con- 
 centration and crystallization. 
 
 The American sources of potash which 
 have been investigated since 1908 and devel- 
 oped since the war are the giant kelps of the 
 Pacific coast, the nativ potash-bearing rocks, 
 the products of blast furnaces and cement 
 kilns and the salts of inland lakes. A brief 
 discussion of each source is given. 
 
 The kelps exert a selective action on the 
 salts in the sea and take up relatively more 
 potassium chlorid than other compounds. 
 When the kelp is dried and incinerated the 
 ash contains 15 to 50 per cent muriate of 
 potash. The cost of production is so high, 
 however, that the procedure is not economi- 
 cal. On the other hand an ingenious fer- 
 mentation process has been devised, pro- 
 ducing acetone and esters as the principal 
 products and potash as a by-product. This 
 is in successful operation on the Pacific coast. 
 
 The amount of potash in such minerals as 
 
34 Preparation of iSubstances 
 
 feldspar is unlimited, but here again the 
 cost of production is so great that httle 
 potash is, as yet, produced from this source. 
 Another mineral containing large quantities 
 of potash is found in Utah and called alunite. 
 This substance contains silicates and sul- 
 fates of potassium and aluminium which on 
 heating furnish water soluble sulfate of pot- 
 ash. Six hundred tons a month of potas- 
 sium sulfate were being produced in 1918 
 from this source. 
 
 Potash is being produced in this country, 
 England and France from the blast furnaces 
 of the steel industry. The limestone, iron ore, 
 and coke used in the smelting may each con- 
 tain some potash; if so during the heating 
 some of this is volatilized. Special devices, 
 electrical precipitators, take the potash-bear- 
 ing dust out of the gases as they pass from the 
 furnaces. Potassium chlorid is the substance 
 obtaind. As there is generally insufficient 
 chlorin to combine with the potassium the 
 amount of substance volatihzed is limited by 
 the chlorin available. The addition of com- 
 mon salt, sodium chlorid, to the furnace 
 charge consequently increases the amount 
 of potash recoverd. It is said that there is 
 sufficient potash available from this source to 
 furnish the entire needs of this country. 
 
 The cement kilns also volatilize potassium 
 
Muriate of Potash 35 
 
 chlorid from potash compounds present in 
 the limestone and silicates used in their 
 manufacture. The material is very fine and 
 would be lost as " smoke " if the particles 
 were not charged with electricity and then 
 caused to deposit on strong electrically 
 charged plates in the Cottrell process of 
 electrical precipitation. 
 
 Searles Lake in the California desert con- 
 tains over 12 square miles of a crystal de- 
 posit 70 feet thick. These crystals are 
 surrounded by a saturated brine carrying 
 about 5 per cent of potassium chlorid. The 
 brine contains two bases, sodium and potas- 
 sium; and four acids, chlorides, sulfates, 
 borates and carbonates. Potassium chlorid 
 and borax are the products of this industry. 
 It is calculated that there are 30 million 
 tons of potash in this region which in itself 
 is sufficient to supply the needs of America 
 for 25 or more years. 
 
 The work outlined in this exercise deals 
 with double salts occasiond by the presence 
 of magnesium when the magnesium is absent, 
 as in most of the American deposits, the 
 process of crystallization is much simplified. 
 
 The size of the crystal generally varies 
 with the rapidity with which it forms. If 
 the salt forms quickly, the crystals are small; 
 if more slowly, the crystals are larger. 
 
36 Preparation of Substances 
 
 ' Each of the crystals has its definit shape which is 
 easily seen under the microscope. Reference is given 
 to various figures of crystals in Watt's Dictionary of 
 Chemistry, Vol. II, pages 148 £f. 
 
 The hydrated double sulfate of potassium and mag- 
 nesium is inclined to form coarse monocHnic prisms 
 which lock hke half cubes or diamonds which have 
 been prest so that the upper faces are not directly over 
 the lower ones. Compare Figs. 285 and 287. 
 
 Potassium chlorid, hke sodium chlorid, appears in 
 cubes or colums, or commonly as a four-sided funnel 
 or hollow pyramid. 
 
 Potassium sulfate may be in small hexagonal prisms 
 (reaUy rhombic) or in longer prisms with a bluntly 
 tapering end. Vid. Figs. 272 and 297. Similar figures 
 are shown in GmeUn-Kraut, Vol. 2i, p. 49. 
 
 Magnesium sulfate is inclined to grow in long 
 needles (rhombic) with faces on the very abrupt end. 
 Vid. Fig. 281. 
 
 Magnesium chlorid, MgCU • 6H2O, forms mono- 
 clinic prisms much like the double sulfate of potash- 
 magnesia. Vid. Figs. 285 and 287. 
 
 QUESTIONS 
 (To be answerd in notebook.)] 
 
 1. Calculate the per cent of potash, K2O, in the 
 sulfate of potash-magnesia; in potassimn sulfate; in 
 potassium chlorid. Express results as foUows: 
 
 K^O 94-3 54.1%. 
 
 K2SO4 174.4 
 
 2. Tell when a solution is saturated. 
 
 3. How many pounds of potassium chlorid in a ton 
 of muriate of 80 per cent grade? 
 
Muriate of Potash 37 
 
 4. How much potash is there in a ton of kainit 
 containing 12 per cent K2O? 
 
 5. If potassium chlorid and magnesium sulfate 
 solutions are mixt what salt is most likely to be pre- 
 cipitated? Why? 
 
 6. What is the solubOity of four salts used in the 
 exercise? Express relatively at some definite tem- 
 perature, putting the most soluble at the head of the 
 colum. 
 
 7. What materials, in addition to sodium chlorid, go 
 to make up the 20% impurities in ordiuary muriate 
 of potash? 
 
 8. How does the double sulfate of potash-magnesia 
 decompose upon being dissolvd in a small quantity 
 of water? 
 
 9. What use is made industrially of the magnesium 
 chlorid brine that, in this exercise, is thrown away after 
 the high-grade muriate of potash has bsen filterd off? 
 
 10. Describs the American sources of potash. 
 
LEAD NITRATE 
 
 Lead nitrate is made from litharge, PbO, 
 and nitric acid. 
 
 Calculation. — From the equation, 
 
 PbO + 2HNO3 = Pb(N03)2 + H2O, 
 
 calculate the amount of nitric acid required 
 to act on 20 grams of lead oxid. Read the 
 spindle floating in the nitric acid to be used 
 and, by reference to the table at the end of 
 this exercise, ascertain how many grams of 
 actual nitric acid in one cubic centimeter of 
 this liquid. By division find out how many 
 cubic centimeters of this nitric acid must 
 be used. 
 Enter the results in the following form : 
 
 Nitric acid required, grams, 
 
 Density of nitric acid solution, 
 
 Number grams nitric acid in 1 cc, 
 
 Volume of nitric acid solution, required, cc, 
 
 Procedure. — Weigh out 20 grams of 
 Utharge, and place it in a small beaker with 
 the required amount of nitric acid. Heat 
 untn the oxid is converted to nitrate and 
 solution results, adding more water, if neces- 
 sary, to dissolv the crystals of lead nitrate. 
 
 38 
 
Lead Nitrate 39 
 
 If a white precipitate of lead sulfate is pres- 
 ent the mixture must be filterd to remove the 
 lead sulfate. Heat the filtrate, or the clear 
 solution, in case filtration was not necessary, 
 until it is saturated; then either cool the 
 solution rapidly or allow it to stand until the 
 next exercise. The lead nitrate crystals may 
 be filterd on an ordinary filter or on a Witt 
 plate and dried in the open air. If the amount 
 of mother-liquor (filtrate) is considerable 
 more crystals may be obtaind by continuing 
 the evaporation of the liquid. / 
 
 NOTES \ 
 
 It is essential that the apparatus be 
 clean. If sulfates are introduced by means 
 of the measuring cylinders or beakers 
 white insoluble lead sulfate will be form.d 
 which must be filterd out. If commercial 
 nitric acid is used it may contain sulfiu-ic acid. 
 
 If the Utharge does not all dissolv more 
 nitric acid may be added or the solution may 
 be filterd and the excess litharge discarded. 
 An excess of nitrate ions from the acid re- 
 duces the solubility of the lead nitrate in 
 water so it is difficult to use solubility tables 
 to determin the least volume of liquid neces- 
 sary to hold the amount of lead nitrate pro- 
 duced in solution. 
 
 The amount of lead nitrate in 100 cc. of a 
 
40 
 
 Preparation of Substances 
 
 solution saturated at given temperatures is 
 found in the following table. 
 
 Solubility Table 
 
 Temperature 
 
 0° 
 
 10° 
 
 18° 
 
 25° 
 
 50° 
 
 100° 
 
 Pb(N03)2grams 
 
 36 
 
 44 
 
 51 
 
 56 
 
 79 
 
 127 
 
 Strength op Nitric Acid Solutions 
 
 
 1 cc. contains 
 
 Density. 
 
 nitric acid, 
 
 
 grams. 
 
 1.05 
 
 0.094 
 
 1.10 
 
 0.188 
 
 1.15 
 
 0.2177 
 
 1.20 
 
 0.388 
 
 1.25 
 
 0.486 
 
 1.30 
 
 0.617 
 
 1.35 
 
 0.753 
 
 1.40 
 
 0.914 
 
 1.45 
 
 1.121 
 
 QUESTIONS 
 (To be answerd in the notebook.) 
 
 1. How many grams of lead nitrate could be made 
 from 20 grams of litharge? What amount of boiling 
 water is necessary to dissolv this amount of salt? 
 (See solubility table.) 
 
 2. How many grams of lead nitrate did you make? 
 
 3. Is the salt more or less soluble in nitric acid than 
 in water? Why? 
 
 4. How many cubic centimeters of nitric acid of a 
 density of 1.10 would be necessary to measure out if 
 200 grams of actual acid were required? 
 
 5. How is nitric acid made? Explain the presence 
 of sulfuric acid in commercial nitric acid. 
 
LEAD ARSENATE 
 
 Lead arsenate is the standard arsenical 
 poison for chewing insects. It is made by 
 mixing equivalent amounts of solutions of 
 either lead acetate or lead nitrate with sodium 
 arsenate. 
 
 Calculation. — Inquire as to the character 
 of the sodiiun arsenate available — as to its 
 condition of hydration and degree of purity 
 — and from the equation, 
 
 Na^HAsO* • 7H2O + Pb(N03)2 = PbHAs04 
 + 2NaN03 + 7H2O, 
 
 calculate the amount of disodium hydrogen 
 arsenate that will be necessary to react with 
 20 grams of lead nitrate. 
 
 If the salt is hydrous the 7H2O will be weighd out 
 and must be calculated; if anhydrous the 7H2O must 
 be left out of the calculation. If the salt is 80 per cent 
 pure the amount to be used must be increased by divid- 
 ing by 0.80. 
 
 Dissolv the lead nitrate in 50 cc. of warm 
 water and dilute to a total volum of 350 cc. 
 with cold water. Similarly dissolv the req- 
 uisit amount of arsenate of soda in a little 
 warm water and dilute to 350 cc. with cold 
 
 41 
 
42 Preparation of Substances 
 
 water. Mix the two solutions. Test the 
 liquid with pieces of red and blue litmus 
 paper. 
 
 As the precipitate of white lead arsenate 
 settles decant the clear supernatant Uquid 
 — best over the edge of the beaker, not using 
 the lip — fill the beaker with fresh water, stir 
 the mixture and again allow the precipitate to 
 settle. Repeat this washing until the soluble 
 salts ar6 removed, and the precipitate, be- 
 comiag colloidal in character and refusing to 
 settle completely, is partially dispersed thru 
 the Uquid. 
 
 This condition being reacht allow the mix- 
 ture to stand over night, so that as much as 
 possible of the lead arsenate wiU settle out, 
 then decant most of the Uquid, neglecting the 
 loss of the comparatively small amount of 
 precipitate in colloidal condition, and bring 
 all the remaining precipitate gradually onto 
 one 15-cm. filter folded in the ordinary way. 
 Allow the precipitate to drain in the funnel 
 for several days; even a week, as a rule, is 
 not too long. 
 
 When the amount of moisture is reduced 
 to about 50 per cent the mass will separate 
 easily from the paper and should be handed 
 in. 
 
Lead Arsenate 43 
 
 NOTES 
 
 With large beakers such as are most al- 
 ways used in this washing process it is an 
 easy matter to put a stirring rod thru the 
 bottom or sides of the beaker. The student 
 should learn to stir without touching the 
 stirring rod to the beaker. In such a case as 
 the one in hand the stirring is best done by 
 the force of the entering wash water. 
 
 The quality of the sodium arsenate on the 
 market varies greatly. The best grades are 
 crystallin and hydrated. The inferior grades 
 are frequently anhydrous, massiv, of spongy 
 appearance and carry considerable sodiiun 
 carbonate and sulfate. 
 
 If the two salts are not used in equivalent 
 proportions the litmus paper will show which 
 was taken in excess. Lead nitrate turns the 
 paper red while sodium arsenate turns it 
 blue. 
 
 The washing takes out the excess of either 
 salt that may have been used, and the sodium 
 nitrate formd by the reaction. In the pres- 
 ence of any considerable quantity of these 
 salts the small particles of lead arsenate are 
 flocculated, that is, many thousands are 
 brot together in one floe. As the concen- 
 tration of the soluble salts is lowerd by wash- 
 ing the particles separate, are deflocculated, 
 
44 Preparation of Substances 
 
 and become so small that their rapid motion 
 ofsets the force of gravity. 
 
 The rapid motion of any small particle 
 in suspension may be easily observd under 
 a high power microscope. The motion is 
 produced by the molecules of water which 
 strike the larger particles with sufficient force 
 and frequency to keep them in oscillation. 
 This motion is known as the " Brownian 
 movement." 
 
 The action which the arsenate of lead 
 undergoes in becoming colloidal is said to 
 be as follows: When the soluble salts (elec- 
 trolytes) are sufficiently decreased by the 
 washing process some groups of mole- 
 cules of lead arsenate react with either the 
 hydrogen or the hydroxyl-ions of the water 
 combining with them. If the particles com- 
 bine with the hydrogen they become posi- 
 tively charged colloids and the hquid re- 
 taining the negativ hydroxyl group becomes 
 negativ. It is entirely possible that it is 
 the layer of atoms on the surfaces of the 
 particles of arsenate of lead which is active 
 in combining with either the H"*" or the ""OH 
 of the water. The action of salt in coagu- 
 lation, or precipitation, consists in neutraliz- 
 ing the electrical charges. As this takes 
 place the lead arsenate particles, which were 
 previously all of the same electrical condi- 
 
Lead Arsenate 45 
 
 tion and consequently were all repellent of 
 each other, gradually floe together, the 
 Brownian motion slows down, and as the 
 particles continue to coalesce the Brownian 
 motion ceases and the solid separates out as 
 a precipitate. 
 
 The arsenate of lead f ormd is a mixture of 
 two compounds; one acidic having the sym- 
 bol PbHAs04, and one basic represented by 
 the formula Pb3As204 • PbjOHAsOi. These 
 two compounds are in equilibrium, 
 
 5PbHAs04 + HOH ^ Pb60H(As04)3 
 + 2H3ASO4, 
 
 the acidic one being gradually changed to the 
 basic one as the arsenic acid formd in the 
 reaction is decanted off during the washings. 
 The change to the basic compound, however, 
 is very slow as with very sUght concentra- 
 tions of arsenic acid such as accumulate in 
 the wash water the action stops and no more 
 basic compound is formd until the superna- 
 tant wash water is replaced by fresh. As an 
 example of the slowness of the change it 
 required, in an experiment by McDonnell 
 and Graham of Washington, D. C, con- 
 tinuous washing for a year to change two 
 grams of the lead acid arsenate to the basic 
 substancq. 
 A piece of blue litmus paper added to the 
 
46 Preparation of Substances 
 
 mixture after the material has been well 
 washt will turn red slowly showing the pres- 
 ence of a sUght concentration of acid. This 
 is the arsenic acid hydrolyzed off from the 
 acid arsenate. 
 
 The addition of any acid changes the 
 equilibrium from right to left forming the 
 acidic arsenate with the elimination of the 
 basic compound. Most of the lead arsenate 
 pastes on the market are made with lead 
 nitrate and the acidity of the system is 
 sufficient to produce a mixture consisting 
 mostly of the acid arsenate with smaller 
 proportions of the basic compound. 
 
 Inasmuch as the acidic arsenate consists 
 of approximately 33 per cent As20b and the 
 basic approximately 23 per cent the analysis 
 of the compound will show the proportions 
 of the two arsenates present. For example, 
 a mixture of the two analyzing 30 per cent 
 AS2O5 is nearly all acidic and contains very 
 Uttle of the basic compound, while one 
 analyzing 2S per cent is composed of equal 
 parts of the two arsenates, basic and acidic. 
 These facts can be applied to the analysis of 
 two commercial samples of arsenate of lead 
 which are here given, one made from, lead 
 nitrate which contains a strong acid and the 
 other made from lead acetate containing a 
 weak acid. 
 
Lead Arsenate 
 
 47 
 
 Analyses op Lead Arsenate 
 
 
 Made from lead 
 
 nitrate, per cent in 
 
 dry salt. 
 
 Made from lead 
 
 acetate, per cent in 
 
 dry salt. 
 
 AsjOs. . . . 
 PbO 
 
 31.40 
 62.80 
 
 25.40 
 74.11 
 
 It will be seen that both preparations are 
 mixtures of the two compounds, the one made 
 from lead nitrate containing much more, in 
 fact is nearly all, of the acidic compound 
 PbHAs04, while the one made in the presence 
 of less acid contains a large proportion of the 
 basic compound. 
 
 Most of the arsenate of lead on the market 
 is in the form of a paste containing 45 to 50 
 per cent water, consequently the actual per 
 cents of arsenic and lead oxids in the ma- 
 terials would be about one-half the figures 
 just given. The dry powder on the market 
 is said to be made by an entirely different 
 process, by suspending lead plates in arsenic 
 acid and causing chemical action by means of 
 an electric current. The lead arsenate that 
 falls off the plates has only to be washt and 
 dried. 
 
 For most uses lead arsenate replaced Paris 
 green as an arsenical poison. Its two advan- 
 tages are its greater insolubility and its ability 
 to stick. The solubility of lead arsenate in 
 
48 Preparation of Substances 
 
 pure water is extremely slight. It is, how- 
 ever, readily decomposed by the salts which 
 appear in natural waters, the carbon dioxid of 
 hard water being particularly effective. The 
 amounts of arsenic acid set free by this reac- 
 tion are, generally, less than one per cent, 
 depending on the water used and not enuf to 
 burn foliage. 
 
 QUESTIONS 
 (To be answerd in the notebook.) 
 
 1. How many grams of anhydrous, 80 per cent 
 pure, arsenate of soda would be required to put with 
 20 grams of lead nitrate? 
 
 2. Explain how lead nitrate can turn Utmus red. 
 
 3. Similarly, how sodium arsenate can turn litmus 
 blue. 
 
 4. What is meant by the terms flocculent; de- 
 flocculated? 
 
 5. Explain the action of soluble salts in flocculating 
 the precipitate. 
 
 6. What salts are washt out of the mixture? How 
 did the litmus paper act in your preparation im- 
 mediately after mixing? 
 
 7. How much arsenic acid (AS2O6) in an ordinary 
 lead arsenate paste? 
 
 8. If lead costs more than arsenic which is cheaper 
 to use as a lead salt, the nitrate or the acetate? The 
 analyses of lead arsenates given will furnish the answer. 
 
 9. Calculate the per cents of AS2O5 and PbO in 
 PbHAs04 in the basic coriipound. This will be confus- 
 ing unless the student keeps in mind the fact that the 
 amount of two arsenics cannot be calculated where 
 only one exists, i.e., AS2O6 cannot be calculated from 
 
Lead Arsenate 49 
 
 one molecule PbHAs04, whereas it can from two mole- 
 cules. In other words the student is askt to resnlv 
 2PbHAs04 into 2PbO, AsjOs and H2O, the water being 
 neglected in this case. 
 
 10. What are the advantages of lead arsenate over 
 Paris green? 
 
LIME-SULFUR 
 
 36-80-50 Formula 
 
 Lime-sulfur is an amber colord liquid con- 
 taining calcium polysulfids, CaS4 and CaSs, 
 and some calcium thiosulfate, CaS203. It is 
 made by boiling lime with a suspension of 
 sulfur. It first came into use as an insecticide 
 on the Pacific coast about 1900 to combat the 
 San Jose scale. Previous to that time a 
 "Lime, Sulfur and Salt" mixture had been 
 used as a sheep wash. Nowadays its use ia 
 more dilute solutions is extending rapidly to 
 control "blights" or fungus diseases, while 
 the stronger solution is still one of the stand- 
 ard remedies for scale insects. In the 
 stronger solutions it is applied during the late 
 winter or early spring before the buds burst. 
 
 Procedure. — Select a beaker or porcelain 
 dish of 400-500 cc. capacity, measm-e into it 
 200 cc. of water, and mark the level of the 
 liquid so that the mark can be recognized 
 after the dish is used for boiling. Weigh out 
 38 grams of quicklime, and slake it in the 
 proper amount of water. Weigh out 80 
 grams of sulfur flour and make this into a 
 thoroly moistend paste with about 200 cc. of 
 
 50 
 
Lime-Sulfur 51 
 
 water. Bring the ingredients together in 
 the markt dish, place the dish on a piece of 
 asbestos over a flame, and keep the mixture 
 boiUng gently. 
 
 During the boihng replace the water if it 
 gets near the 200 cc. mark. It is not neces- 
 sary that any particular volum should re- 
 main at the end of the boiUng period; the 
 less water the stronger the solution and the 
 more thiosulfate is decomposed and the more 
 CaSs is formd in place of CaS4; however, if 
 the solution is made too concentrated there 
 will not be sufficient Uquid to float the 
 hydrometer spindle. To make a solution of 
 the same density as the commercial prepara- 
 tions, 34° Be., it would be necessary to con- 
 centrate the liquid to less than 200 cc. 
 
 When the liquid acquires a dark amber 
 color and the suspended sulfur has dis- 
 appeard the Ume-sulfm- is made. This may 
 require an hour. If the preparation is to 
 stand until the next exercise it should be 
 coverd to keep out as much oxygen as pos- 
 sible. Reducing the surface by placing the 
 mixture in a narrow vessel also reduces the 
 oxygen absorption. If it is intended to com- 
 plete the work at once the mixture may be 
 coold by immersing the container in water. 
 After standing observe that a crust has 
 formd on the surface of the liquid which is 
 
62 Preparation of Substances 
 
 much thicker if the preparation has stood 
 for several days. Decant the clear Uquid 
 into the special Ume-sulfur hydrometer cyl- 
 inders and take the density on both the 
 specific gravity and Beaume scales. From 
 the concentrated clear liquid prepare two 
 sprays, one for use when the buds are dor- 
 mant and one for use on the green foliage 
 in summer. Take the density (Be.) of both 
 diluted sprays and record the data in the 
 notebook. 
 
 If any lead arsenate is available make a 
 thin paste of this and add some of it to the 
 dilute summer spray. Notice the gradual 
 darkening as some of the lead is withdrawn 
 from the combination with arsenic acid and 
 combined with sulfur to form black lead 
 sulfid; small amounts of arsenic acid are set 
 free at the same time. This is a combination 
 spray having two functions, insecticidal and 
 fungicidal. 
 
 NOTES 
 
 The 1910 Geneva Formula, 36 pounds 
 of lime; 80 pounds sulfur; 50 gallons water, 
 is here made over for laboratory use. The 
 directions are based on bulletin No. 329 
 of the New York Agricultural Experiment 
 Station, by Van Slyke, Bosworth and Hedges. 
 
 If the lime is pure 36 grams should be used, 
 if 95 per cent CaO {i.e., 5 per cent MgO) 
 
Lime-Sulfur 53 
 
 38 grams should be used, if 90 per cent lime 
 40 grams. Lime that is over 10 per cent 
 magnesium oxid should not be used as 
 it is a waste of material. The magnesium 
 forms insoluble compounds that go into the 
 sediment. In case the lime is already slaked 
 increase the quantity in the ratio of the 
 weights of CaO : CaOaHa {i.e., 56 : 74). 
 
 It is an easy matter to select lime that 
 carries less than 2 per cent of magnesia as the 
 analysis is on the barrel and the product of a 
 given lime-kiln is fairly constant in compo- 
 sition. 
 
 If all the material is not in very finely 
 divided condition it will remain as sediment 
 and not react; hence the sulfur is moistend 
 to prevent lumping. 
 
 If a beaker is used place a piece of asbestos 
 under it, otherwise the solid material will 
 form a blanket over the bottom of the beaker 
 and prevent the diffusion of the heat. The 
 glass will not stand sudden local heating and 
 cooling resulting from such blanketing. 
 
 The reactions which take place when the 
 material is being made, according to Pro- 
 fessor Tartar at the Oregon Agricultural Ex- 
 periment Station, are, first, the action of lime 
 and sulfur to form calcium tetrasulfid, and 
 calciiun thiosuHate, 
 
 3Ca02H2 + lOS = 2CaS4 + CaSzOs + 3H2O. 
 
54 Preparation of Substances 
 
 Second, as the liquid becomes concentrated 
 the calcium thiosulfate breaks down forming 
 the insoluble calciima sulfite liberating one 
 atom of sulfur, 
 
 CaSzOs = CaSOs 4- S. 
 
 This reaction may be taking place in this 
 experiment when the volume of the liquid is 
 reduced to about 200 cc. The insoluble cal- 
 cium sulfite remains as a sediment. Third, 
 the sulfur liberated from the thiosulfate unites 
 with the tetrasulfid forming pentasulfid, 
 
 CaS4 -I- S = CaSs. 
 
 Thus the composition of the mixture 
 changes during concentration. The amounts 
 of thiosulfate and tetrasulfid become lessend 
 and the quantity of pentasulfid increased. 
 Such changes are considerd desirable and 
 have been effected in most of the commercial 
 preparations on the market. 
 
 Combination sprays may be made by mix- 
 ing Ume-sulfur with arsenate of lead or 
 nicotine sulfate, or both, and simultaneously 
 kill chewing insects and aphis, as well as 
 prevent attacks of fungus diseases. 
 
 Professor Schaefer, of the Michigan Agri- 
 cultural College, states that the action of 
 lime-sulfur solution upon the San Jos6 scale 
 is one of suffocation; that the caustic liquid 
 
Lime-Sulfur 55 
 
 finds its way under the edges of the little 
 shell under which the insect lives, shutting 
 off the outside oxygen and rapidly con- 
 suming what remains inside. 
 
 The fungicidal action of lime-sulfur is 
 thot to be due to the sulfur deposited from it. 
 This, in the air, oxidizes slowly to sulfur 
 dioxid which is toxic. 
 
 Long boihng exposed to the air, as is neces- 
 sary in laboratory manipulation, is harmful 
 to the product as the polysulfids react rapidly 
 with the oxygen of the air depositing sulfur 
 and forming thiosulfate, 
 
 CaSs + 30 = CaSaOs + 3S. 
 
 This is the change that takes place when 
 lime-sulfur stands exposed to the air. At 
 first only a fihn of. sulfur is seen as the cal- 
 cium thiosulfate dissolvs, but as the upper 
 layer becomes saturated with thiosulfate 
 crystals these become mixt with the sulfur 
 forming a hard crust. It is evident from this 
 that the mixture should not stand in the 
 laboratory any longer than necessary. 
 
 The action of lime-suKur when used as a 
 spray follows from the explanation in the 
 previous paragraf. First, it rapidly takes 
 up oxygen forming calcium thiosulfate and 
 depositing all the sulfur in excess of two atoms 
 to the molecule. Second, the thiosulfate 
 
66 
 
 Preparation of Substances 
 
 slowly breaks down to insoluble sulfid and 
 one atom of sulfur is set free. This change 
 is slow and is represented by the equation, 
 
 CaSzOs = CaSOs + S. 
 
 Limb-Sulfur Table " 
 Data furnishing a basis for diluting lime-sulfur wash 
 
 
 Sulfur 
 
 to 
 
 l-B^., 
 
 per 
 
 cent. 
 
 Sulfur 
 
 in sol., 
 
 per 
 
 cent. 
 
 Wt. one 
 
 Sulfur 
 in one 
 
 fbl' 
 
 Dilution as indicated for 
 1 gal. solution. 
 
 Den- 
 sity. 
 
 Dormant 
 spray. 
 
 (San Jo.s6 
 
 scale) , 
 jals.wate.". 
 
 Blister 
 mile, 
 gals. 
 
 water. 
 
 Sum- 
 mer 
 
 spray, 
 gals. 
 
 water. 
 
 36 
 
 0.75 
 
 27.00 
 
 11.08 
 
 2.99 
 
 9 
 
 12i 
 
 45 
 
 35 
 
 0.75 
 
 26.25 
 
 10.98 
 
 2.88 
 
 8f 
 
 12 
 
 43- 
 
 34 
 
 0.75 
 
 25.50 
 
 10.88 
 
 2.77 
 
 8i 
 
 IH 
 
 41 
 
 33 
 
 0.75 
 
 24.75 
 
 10.78 
 
 2.67 
 
 8 
 
 11 
 
 40 
 
 32 
 
 0.74 
 
 23.70 
 
 10.69 
 
 2.53 
 
 7? 
 
 101 
 
 37| 
 
 31 
 
 0.74 
 
 22.95 
 
 10.60 
 
 2.43 
 
 7i 
 
 10 
 
 36i 
 
 30 
 
 0.73 
 
 21.90 
 
 10.51 
 
 2.30 
 
 6- 
 
 9i 
 
 34i 
 
 29 
 
 0.73 
 
 21.15 
 
 10.42 
 
 2.20 
 
 6- 
 
 9 
 
 32f 
 
 28 
 
 0.72 
 
 20.15 
 
 10.32 
 
 2.08 
 
 6 
 
 8i 
 
 31 
 
 27 
 
 0.72 
 
 19.45 
 
 l'J.23 
 
 1.99 
 
 5f 
 
 8 
 
 291 
 
 26 
 
 0.71 
 
 18.45 
 
 10.15 
 
 1.87 
 
 5i 
 
 7i 
 
 271 
 
 25 
 
 0.70 
 
 17.50 
 
 10.07 
 
 1.76 
 
 5 
 
 7 
 
 26 
 
 24 
 
 0.69 
 
 16.65 
 
 9.98 
 
 1.65 
 
 ^ 
 
 6i 
 
 24i 
 
 23 
 
 0.68 
 
 15.65 
 
 9.90 
 
 1.55 
 
 4i 
 
 6 
 
 22J 
 
 22 
 
 0.67 
 
 14.75 
 
 9.82 
 
 1.45 
 
 3J 
 
 5i 
 
 21| 
 
 21 
 
 0.66 
 
 13.85 
 
 9.74 
 
 1.35 
 
 3i 
 
 5 
 
 19| 
 
 20 
 
 0.65 
 
 13.00 
 
 9.67 
 
 1.26 
 
 3i 
 
 4f 
 
 18i 
 
 19 
 
 0.65 
 
 12.35 
 
 9.59 
 
 1.18 
 
 3 
 
 4i 
 
 17 
 
 18 
 
 0.65 
 
 11.70 
 
 9.51 
 
 1.11 
 
 21 
 
 4 
 
 16 
 
 17 
 
 0.65 
 
 11.05 
 
 9.44 
 
 1.04 
 
 2i 
 
 3f 
 
 15 
 
 16 
 
 0.65 
 
 10.40 
 
 9.37 
 
 0.97 
 
 2i 
 
 3i 
 
 14 
 
 15 
 
 0.65 
 
 9.75 
 
 9.30 
 
 0.90 
 
 2 
 
 3 
 
 12i 
 
 * From Bulletin No. 329, page 316, New York Agri- 
 cultural Experiment Station; Van Slyke, Bosworth and 
 Hedges. 
 
Lime-Sulfur 57 
 
 Third, the sulfite takes up oxygen forming 
 calcium sulfate, 
 
 CaSOs + O = CaS04, 
 
 so that calcium sulfate and sulfur are the 
 final products of decomposition of the lime- 
 sulfur mixture. 
 
 The analysis of a commercial lime-sulfur 
 concentrate is as follows: 
 
 Sp. gr., 1.30 or 33.7 B^. 
 
 Sulfur in thiosulf ate, 0.25% 
 
 Sulfur in tetrasulfid, 0.50% 
 
 Sulfur in pentasulfid, 24.75% 
 
 Total sulfur, 25. 50% 
 
 This shows that the amount of thiosulfate 
 has been greatly reduced, and that the sub- 
 stance present in greatest quantity is cal- 
 cium pentasulfid. 
 
 QUESTIONS 
 (To be answerd ^ the notebook.) 
 
 1. Did you have sufficient lime-sulfur solution to 
 float the hydrometer spindle? What was the Beaum6 
 reading of your solution? 
 
 2. How many pounds of sulfur in one gallon of your 
 solution? 
 
 3. How much would the sulfur in 50 gallons cost 
 at the rate of $20.00 per ton? 
 
 4. What dilution did you make for the San Jos6 
 scale? What was the density of the dilute solution? 
 
58 Preparation of Substances 
 
 5. What dilution for summer spray? Resulting 
 density? 
 
 6. What change was observd when lead arsenate 
 was mixt with the summer spray? What new in- 
 soluble substance was formd? 
 
 7. What is the per cent of sulfur in the lime-sulfur 
 you made? 
 
 8. What substances are in lime-sulfur? Under- 
 score the one present in largest quantity. 
 
 9. What is in the sediment in lime-sulfur? 
 
 10. Write the reactions that take place when the 
 lime-sulfur is made, placing the name of each substance 
 xmder its symbol. 
 
 11. Similarly write the series of reactions that take 
 place when lime-sulfur is oxidized. 
 
 12. What effect on the composition of lime-sulfur 
 has long boiling? The concentration below 200 cc? 
 
 13. What are the uses of lime-sulfur? 
 
 14. What is said to be the action of lime-sulfur 
 in killing San Jos6 scale? 
 
 15. What are the final products of oxidation of 
 lime-sulfur? 
 
 16. A barrel of lime-sulfur was left half full over one 
 season. What substances would be found in the 
 crust that formd on the liquid? 
 
 17. What specific gravity is equivalent to 33 B6.? 
 
 18. What are the ordinary impurities ui lime? 
 
 19. Write the reaction for slaking lime. 
 
 20. How many grams of slaked lime can be made 
 from 40 grams of quicklime? 
 
COPPER SULFATE 
 
 Procedure. — Place in a beaker 10 grams 
 of metallic copper, 50 cc. of water, 15 to 18 cc. 
 of chamber sulfviric acid and 25 cc. of dilute 
 (sp. gr. 1.2, 32 per cent) nitric acid. Place 
 the mixture on asbestos, under a hood, and 
 heat gently with a low flame until the copper 
 is all dissolvd. This should require about 
 an hour. In case the solution becomes 
 satmrated dm-ing the heating as evinst by 
 the crystals forming on the surface, add a 
 few drops of water. When the copper is all 
 dissolvd continue heating until the solution is 
 satm-ated, then remove the beaker, place it 
 in cold water and stir the solution as it cools 
 imtil crystalhzation is complete. Filter off 
 the crystals on a Witt plate. Evaporate 
 the filtrate to the point of crystalhzation and 
 cool the hquid until all the crystals have 
 formd that will. If possible pour out the 
 mother liquor, which consists mostly of strong 
 acids, and bring the remaining crystals onto 
 a Witt filter. Put both crops of crystals into 
 25 cc. of boiling water and adjust the quan- 
 tity of water, by adding directly and boiling 
 off, until the salt is all dissolvd and the solu- 
 
 59 
 
60 Preparation of Substances 
 
 tion becomes satxirated. Cool the liquid 
 with stirring or allow it to stand until the 
 next exercise. Filter off the crystals and dry 
 them between filter paper. Save the mother 
 liquor for the tests which follow. 
 
 Tests for copper ; Notebook. — Test some 
 copper sulfate by adding ammonium hy- 
 droxid, at first one drop, then in larger quan- 
 tity. The light blue insoluble substance 
 f ormd .by the small amount of ammonia is a 
 basic copper sulfate; the blue solution con- 
 tains copper and ammonia together in one 
 ion, an ammonio-cupric suKate Cu(NH3)4S04. 
 This solution contains very few copper ions — 
 only those that break away from this com- 
 plex. The formation of a blue solution is a 
 test for copper. To the blue solution add a 
 few drops of potassium ferrocyanide. There 
 being so few Cu ions the copper ferrocyanide 
 formd is not v sible. Break up the ammonio- 
 copper complex by adding acetic or dilute 
 hydrochloric acids. As soon as copper ions 
 are present in amount of about 0.002 per cent 
 the copper ferrocyanide begins to be visible. 
 
 Add a few drops of potassium ferrocyanide 
 to a copper sulfate solution. The formation 
 of brown copper ferrocyanide is a test for 
 copper. 
 
Copper Sulfate 61 
 
 NOTES 
 
 Bluestone or copper sulfate is the impor- 
 tant salt of copper for agriculture. Its weak 
 solution is fungicide and a disinfectant. 
 Seed wheat is treated with it to kill the 
 spores of the smut. Bordeaux mixture and 
 Paris green are made from it. 
 
 Copper does not dissolv in acids without 
 first being oxidized. This may be accom- 
 phsht, superficially, by heating in air when 
 the resulting coating of black copper oxid 
 wiU dissolv in suKuric acid. Copper may be 
 fused with sulfm- when the resulting copper 
 sulfid will respond to the action of sulfuric 
 acid. The unreduced copper sulfid of copper 
 matte which falls to the bottom of the tank 
 when crude copper is electrolytically piirified 
 is used to make copper sulfate. Copper 
 moistend with acid will take oxygen from the 
 air and dissolv slowly. In this experiment 
 the oxygen is obtaind from nitric acid. 
 
 QUESTIONS 
 (To be answerd in the notebook.) 
 
 1. From the symbol, CUSO4 • 5H2O, calculate the 
 amount of crystaUized salt that may be made from 10 
 grams of metaUic copper. 
 
 2. From the same symbol find out how many grams 
 of sulfuric acid would be necessary. 
 
 3. Consult the table of the density of sulfuric acid 
 under superphosphate and determin how many cubic 
 
62 Preparation of Substances 
 
 centimeters of sulfuric acid would be necessary to 
 contain the number of grams found under 2. 
 
 4. What volum of nitrogen oxids was given off in 
 this experiment? To solv this problem it wiU be 
 necessary to establish the relationship between the 
 weight of copper used and the volum of gas given off. 
 The gas given off is the colorless nitric oxid which 
 changes to the brown nitrogen dioxid without change 
 ia volum upon exposure to the air. The following 
 equation shows the decomposition of nitric acid as it 
 takes place in the experiment, 
 
 4HNO3 = 2H2O + 3O2 + 4N0. 
 
 The change from the colorless to the brown oxid is 
 simple, 
 
 2N0 +02= 2NO2, 
 
 and the quantities 2N0 and 2NO2 bear out the state- 
 ment that there is no change in volum in the oxida- 
 tion of nitric oxid to nitrogen dioxid. The relation of 
 the nitrogen dioxid to the copper must be sought thru 
 the oxygen which imites with the copper, 
 
 Cu + = CuO. 
 
 The copper being once oxidized we lose interest in it, 
 for the purposes of this calculation, as it reacts with 
 the sulfuric acid without changing its relationship to 
 the oxygen, 
 
 CuO + H2SO4 • aq. = CUSO4 • aq. 
 
 Now it is possible to establish the relationship of the 
 copper to the nitrogen dioxid thru the oxygen as fol- 
 lows: One Cu unites with one 0, hence 6Cu unites 
 with -302 and, from the first equation, the produc- 
 tion of 3O2 is accompanied by the evolution of 4N0 
 which goes to 4NO2 without change in volum. Then 
 6Cu are accompanied by the production of 4NO2 
 
Copper Sulfate 63 
 
 which establishes the relationship between the copper 
 and the gas given off. The number of giams repre- 
 sented by the symbol NO2 occupies 22.4 Uters (molec- 
 ular volum) . Now we have the complete data for the 
 ratio which is 
 
 6Cu _ 381.6 grams of copper 
 4(22.4 Uters) 89.6 liters of gas 
 
 As 10 grams of copper were used in the experiment the 
 following proportion wiU give the number of hters of 
 gas produced: 
 
 ?|L§ = 1° = Uters of either NO or NO2. 
 89.6 X 
 
 5. What is necessary to make copper dissolv in 
 acids? 
 
 6. What are the uses of copper suUate? 
 
 7. What are two tests for copper? What compoimd 
 in each case is used to recognize the copper? 
 
 8. How can the number of copper ions in a solution 
 be reduced to a negUgible quantity? 
 
 9. What oxid, or oxids, of nitrogen are red? What 
 colorless? 
 
 10. How many liters of nitrogen dioxid were given 
 off in this experiment ? Of nitric oxid oxidized by the 
 air? How many grams of each? 
 
PARIS GREEN 
 
 Paris green closely approximates the for- 
 mula Cu(C2H302)2 • 3Cu(As02)2, which was 
 assignd it by Ehrmann in 1834, and is cald 
 an aceto-arsenite of copper. There are two 
 general processes for making it, first replacing 
 most of the acetate ion of copper acetate by 
 the arsenite ion of arsenious acid; and second, 
 replacing some of the arsenite ion of copper 
 arsenite by the acetate ion of acetic acid. 
 The latter process is foUowd in these direc- 
 tions. 
 
 Procedure. — Dissolv 9 grams of dry 
 carbonate of soda, or 24 grams of hydrous, in 
 a beaker or porcelain d'sh in 80 cc. of water. 
 Into this solution sprinkle gradually 16 
 grams of arsenious oxid, and boil until the 
 acid has united with the soda as shown by 
 solution of the resulting sodium arsenite. 
 
 Dissolv 20 grams of copper sulfate in 80 
 cc. of water. When both of the solutions 
 are at about 60° — as warm as the hand can 
 comfortably bear — pour the sodium arsenite 
 solution into the copper sulfate. Add 10.5 
 cc. of 50 per cent acetic acid — or an equiva- 
 lent of any other strength, and allow the 
 
 64 
 
Pans Green 65 
 
 mixture to digest at about 50° for some time 
 on a piece of asbestos board over a low flame. 
 If the green copper aceto-arsenite does not 
 form at this point, not enough acetic acid 
 has been added. Consult an Instructor 
 before adding more than a few drops of acid 
 as too much may decompose the salt. Stir 
 occasionally — once in five minutes — and 
 when the reaction seems complete drain the 
 green product on a funnel and wash to 
 remove soluble arsenites and sodixmi sulfate. 
 Examin the size and shape of the particles 
 under a microscope. When dry put in a 
 clean, dry beaker and see if it "flows" well. 
 
 NOTES 
 
 Paris green is one of the oldest arsenical 
 insecticides. For many years it was the 
 standard remedy for the potato beetle. It 
 is applied to the vines suspended in water. 
 
 The composition of Paris green required 
 by the symbol is never exactly attaind, the 
 amount of arsenic being somewhat less than 
 the ideal quantity. The analysis of a theo- 
 retical compound of the formula given, of 
 two samples of Paris green carefully made, 
 and the average analysis of 494 samples 
 bot on the open market in Pennsylvania, are 
 given in the following table : 
 
66 
 
 Preparation of Substances 
 
 Analyses of Paris Green 
 
 
 Theoretical. 
 
 Avery, 
 Nebraska. 
 
 Holland 
 and Reed, 
 Massachu- 
 setts. 
 
 FelloK. 
 average 494 
 
 samples, 
 Penn., 1910. 
 
 AS203 
 
 CaO 
 
 {CKMCOhO 
 
 58.55 
 31.39 
 10.06 
 
 57.55 
 31.75 
 10.31 
 
 56.94 
 
 31.74 
 
 10.37 
 
 78 
 
 57.97 
 
 29.41 
 
 
 
 
 100.00 
 
 99.61 
 
 99.83 
 
 
 
 
 It is noticed that while the arsenic falls 
 about one per cent short the amount of copper 
 oxid is slightly increased as is the acetic acid, 
 this may be taken to mean that there is 
 slightly more copper acetate in the compound 
 than is shown by the symbol. 
 
 In the solution from which Paris green is 
 made, arsenite, acetate and copper ions must 
 be in such concentrations, and the tempera- 
 tures so adjusted as to allow the formation 
 of the copper aceto-arsenite. Too much 
 acetic acid will throw the white arsenious oxid 
 out of solution. The reagents must be 
 measured with considerable care to avoid the 
 effect of varying masses. The base and acids 
 concernd are all weak, and the compound is 
 easily hydrolyzed by water; hence the long 
 digestion to allow the formation of large 
 particles in which the ratio of mass to surface, 
 m/s, is greater. 
 
Paris Green 67 
 
 QUESTIONS 
 (To be answerd in the notebook.) 
 
 1. Name the acidic and basic ions used in making 
 Paris green. 
 
 2. What shaped particle has the largest ratio of m/s? 
 
 3. What are the relativ advantages of Paris greens 
 composed of large particles; of small particles; of 
 particles of spherical shape; of broken cornered par- 
 ticles? (Discuss in reference to degree of hydrolysis 
 and time of suspension.) 
 
 4. What is the objection to putting Paris green in 
 water several days before using? Of applying on a wet 
 day? 
 
 5. How many grams of crystallized sodium carbon- 
 ate, NajCOa •IOH2O, could be made from 10 grams of 
 the anhydrous salt? 
 
 6. Water hydrolyzes Paris green. State some of 
 the possible products of hydrolysis. Which of these 
 are soluble? 
 
 7. Write a symbol for orthoarsenious acid; meta- 
 arsenious acid. (See textbook.) 
 
 8. Write a reaction between NajCOa and AS2O3 
 naming all the substances. 
 
 9. Write the s5rmbol of acetic acid. 
 
 10. How many grams of arsenic trioxid wiU react 
 with 24 grams of dry sodiimi carbonate? 
 
BORDEAUX MIXTXJRE 
 
 I. ORDINARY BORDEAUX 
 
 The composition of the mixture produced 
 by the formula ordinarily used, 4-^-50, is 
 said to be a basic suKate of copper and lime; 
 its composition being represented by the 
 symbol, CuS04-9CuO-CaS04-3CaO. 
 
 Procedure. — Weigh out 8 grams of cop- 
 per sulfate, dissolv it in 50 cc. of water, using 
 heat if it is desired to hasten the solution, and 
 add 350 cc. of cold water making the total 
 volmn 400 cc. Slake 8 grams of quicklime 
 with a little water, dilute the paste with about 
 200 cc. of cold water and strain the mass thru 
 a piece of cheesecloth placed over a funnel 
 or a thistle tube. Dilute the milk of lime to 
 400 cc. Mix the cold solutions. 
 
 n. WOBURN BORDEAUX 
 
 Woburn Bordeaux may consist of either 
 of three basic sulfates of copper, the pro- 
 portions of base to acid in each being shown 
 in the following formulas: CuS04-3CuO; or 
 CuS044CuO; or CuS04-9CuO.CaS04. Its 
 most striking characteristic is the absence 
 of any free Ume. Either of the three com- 
 es 
 
Bordeaux Mixture 69 
 
 pounds may be made in this experiment ac- 
 cording to the amount of Ume-water used. 
 
 Procedure. — Weigh out 0.5 gram of 
 copper suUate or get a solution containing 
 that amount and dilute it to 380 cc. Meas- 
 ure out either 70, 74 or 84 cc. of lime-water 
 and dilute it to 380 cc. Mix the two solu- 
 tions. 
 
 Properties of Bordeaux Mixtures; Note- 
 book. 
 
 1. Compare the color of the two mixtures. 
 
 2. Stir them up and allow to stand. Which stays 
 in suspension best? 
 
 3. How much does each mixture settle in 15 min- 
 utes? Is a white scum to be seen on either prepara- 
 tion? If so which one? 
 
 4. Filter some of the Woburn Bordeaux and add 
 a few drops of potassium ferrocyanide solution to test 
 tube of the clear filtrate. If copper is in solution as 
 positiv ion, in amounts of over 0.002 per cent, the 
 brownish color of copper ferrocyanid should be seen. 
 It may be necessary to look down the colum onto a i 
 white background to see the color and it may be well 
 to compare this tube with another containing only 
 water and the same number of drops of ferrocyanid 
 solution. Are any copper ions (Cu++) in solution? 
 
 NOTES 
 
 The ordinary, or one per cent, Bordeaux 
 is made from 4 poimds of copper sulfate, 
 4 pounds of quicklime and 50 gallons 
 of water. This formula is here reproduced 
 
' 70 Preparation of Substances < 
 
 on a small scale suitable for laboratory pur- 
 poses. The Woburn Bordeaux, if enlarged 
 to barrel proportions, would consist of 4|- 
 ounces of copper sulfate, 4^- gallons of lime- 
 water in 51 gallons of the mixture. 
 
 Several compoimds of copper can be made 
 by mixing lime and copper sulfate in different 
 amounts. The following symbols* show the 
 proportions present in the various substances 
 that can be f ormd : 
 
 (I) CuS04-3CuO. (II) CuS044CuO. 
 (Ill) CuS04-9CuO-CaS04. (IV) CuS04- 
 9CuO-CaS04-3CaO. (V) CuO-SCaO. 
 
 It will be noted that the compound (II) is 
 more basic than (I) and that the basicity 
 increases progressively so that (V) is all base. 
 The compounds are produced successively, 
 by using increased quantities of lime-water 
 with the same amount of copper sulfate. 
 For example, with 0.5 gram of copper siilfate, 
 70 cc. of lime-water will produce the com- 
 pound CuS04-3CuO, 74.1 cc. of lime-water 
 will give CuS044CuO and 83.3 cc. of lime- 
 water will make CuS04-9CuO-CaS04. Wo- 
 burn Bordeaux may be any one of these 
 
 * Taken from the 11th Annual Report (p. 25) of the 
 Wobum Experimental Fruit Farm by the Duke of Bed- 
 ford and Mr. Pickering. Some calcium sulfate is reported 
 united with the first three compounds in addition to that 
 represented. 
 
Bordeaux Mixture 71 
 
 compounds or mixtures of then}. With a 
 large excess of the base the compound 
 (IV) is produced having the formula 
 CuS04-9CuO.CaS04-3CaO. This is still 
 more basic in that it contains some of the 
 basic calcium sulfate in addition to the basic 
 copper sulfate. Such a compound the ordi- 
 nary Bordeaux mixture is said to be. 
 
 From the symbol of the copper compound 
 in ordinary Bordeaux, CuS04'9CuO'CaS04' 
 3CaO, an equation may be written to account 
 for the formation of such a substance, 
 
 IOCUSO4 + 12Ca02H2 = CuS04-9CuO- 
 CaS04-3CaO + 8CaS04 + I2H2O. 
 
 From this it is seen that considerable cal- 
 cium suKate is formd at the time the Bor- 
 deaux is made. Calcium sulfate is soluble 
 in water at 25°, to the amount of 0.21 gram 
 per liter. If any free Ume is left over, which 
 is always the case, the solubility is lessend, 
 as both compounds contain a common cal- 
 cium ion. 
 
 A rough calculation on the part of the 
 student will show that 8 grams of copper 
 sulfate require about 2 grams of lime to 
 react with it. For example, the formula for 
 the precipitate in ordinary Bordeaux is 
 given as CuS04-9CuO-CaS04-3CaO. Lime is 
 used to produce the 9CuO and the 3CaO 
 
72 Preparation of Substances 
 
 making 12CaO used for every lOCu; or 
 more in detail, 9Ca02H2 were necessary to 
 react with QCuSO* before the resulting 
 9CUO2H2 could form 9CuO and 3CaO are 
 found in the product making a total of 12CaO 
 required. The lOCu come from lOCuSO^- 
 5H2O and thus the ratio between copper 
 sulfate and Ume, l0CuSO4-5H2O/12CaO, is 
 estabUsht. In figures it is 2497.3/672 or 
 3.7 showing that nearly four times as much 
 Ume is used as is cald for by the symbol. 
 This ratio has been fixt by horticultural 
 practise. 
 
 From the previous paragraf it is evident 
 that nearly four times as much Ume is used 
 as is needed. The student wiU inquire as to 
 what becomes of the remainder. The solu- 
 biUty of calcium hydroxid at 25° is 0.16 
 gram in 100 cc. of water. This amount, 
 however, is lessend by the presence of cal- 
 cium sulfate so that only a smaU portion of 
 the whole amount of lime dissolvs in water. 
 Further, not aU the lime weighd out gets 
 into the preparation, as lumps, air-slaked 
 material and frequently Ume itseU may be 
 rejected by the strainer. It is obvious that 
 aU the lime not in solution must be mixt in 
 with the precipitate. 
 
 The white scum is calcium carbonate 
 made up of carbon dioxid from the air and 
 
Bordeaux Mixture 73 
 
 the excess lime in solution. There must be 
 lime enuf present to precipitate all the cop- 
 per before there can be any left over to 
 react with carbon dioxid so that the forma- 
 tion of a white scum is proof that no copper 
 remains in solution and that the mixture 
 does not contain any soluble copper that can 
 bum fohage. 
 
 Bordeaux mixture protects plants from 
 attacks of fungous diseases. When spread 
 over the leaf it dissolvs very slightly and 
 disease spores blown on by the wind are 
 Idld upon germination by the soluble copper 
 formd. 
 
 The substances which act upon the Bor- 
 deaux to make the copper soluble, to the best 
 of our present knowledge, are the carbon 
 dioxid, the ammonia and the nitric acid 
 present in the atmosphere. The carbon 
 dioxid first combines with hme forming in- 
 soluble calcium carbonate and following this 
 begins the conversion of the copper to basic 
 copper carbonate which is accompanied by 
 the liberation of copper sulfate. Basic cop- 
 per carbonate is dissolvd by more carbon 
 dioxid, by ammonia, by nitric acid, or by 
 ammonium nitrate made from the ammonia 
 and nitric acid. The amount of soluble cop- 
 per produced by the atmospheric agencies 
 is very small, — thousandths or ten-thou- 
 
74 Preparation of Substances 
 
 sandths of one per cent, — while the amount 
 of soluble copper that a leaf can stand without 
 burning is much larger and is in the neigh- 
 borhood of 0.04 per cent. 
 
 The ordinary Bordeaux mixture — con- 
 taining four times as much lime as is needed 
 for producing the insoluble copper compounds 
 — after being spread out on the plant does 
 not begin the liberation of soluble copper until 
 the carbon dioxid of the atmosphere has 
 acted on the excess of lime present. This 
 process requires several days. On the other 
 hand the Woburn Bordeaux having no excess 
 of lime is acted upon by the carbon dioxid 
 at once and soluble copper is available in a 
 short time. 
 
 The increased vigor of plants, particularly 
 potatoes, which is noticed when they have 
 been sprayd with Bordeaux mixture, is due, 
 to the best of our knowledge, to the preven- 
 tion of minor insect ravages rather than a 
 stimulating action of the very dilute copper 
 solution on the chlorophyl. It has been 
 shown by Pickering that potato leaves im- 
 merst in dilute copper sulfate solution give 
 off iron and take on copper and from this it 
 was argued that the dilute copper solution 
 might have an accelerating effect upon the 
 chlorophyl action. Recent work has shown, 
 however, that the simpler explanation of in- 
 
Bordeaux Mixture 75 
 
 sect and disease prevention is the more 
 plausible explanation of the apparent stimu- 
 lation. Iron is a constituent of chlorophyl. 
 The rate at which Bordeaux mixture settles 
 is an important matter. Each of the com- 
 pounds I to V has a different density, is more 
 or less volmninous and settles at a different 
 rate from the others. Pickering states that 
 the volmns occupied by the precipitates after 
 standing 15 minutes vary regularly and may 
 be represented, approximately, by these mun- 
 bers, 8(1), 17(11), 86(111), 98(IV), 20(interpo- 
 lated) (V). This means that (IV), ordinary 
 Bordeaux, is the most volmninous and stays 
 in suspension best. Butler* shows that the 
 order of mixing and the concentration of solu- 
 tions at the time of mixing have a bearing 
 on length of time the precipitate stays in sus- 
 pension and recommends making a dilute 
 copper solution and pouring this into a strong 
 milk of lime. The directions for this exercise 
 allow the student to make the copper and lime 
 solutions of equal volmn and pom- one into 
 the other indiscriminately. According to 
 Butler the methods foUowd in this exercise 
 take second rank in producing desirable volu- 
 minous precipitates. 
 
 * Technical Bulletin, No. 8, New Hampshire Experi- 
 ment Station; also Phytopathology, 1914. 
 
76 Preparation of Substances 
 
 QUESTIONS 
 (To be answerd in the notebook.) 
 
 5. What amounts of copper sulfate and lime-water 
 did you use in making your Woburn Bordeaux? 
 
 6. How many times as much copper sulfate is used 
 for ordinary Bordeaux as for the Woburn mixture? 
 How does the ordinary Bordeaux mixture differ in 
 composition from Woburn? 
 
 7. Give a definition for a basic salt. 
 
 8. How may one test for copper? 
 
 9. What is meant by the expression 4-4-50? 
 
 10. The symbol for the compound (I) CuSOi-SCuO 
 may be written 4CuO'S03. Rewrite (II), (III) and 
 (IV) in a similar manner. Underscore the least basic 
 of these compounds. Double underscore the basic 
 part of this compoimd. 
 
 11. What is the use of Bordeaux mixture? How 
 does it act? 
 
 12. Figure the amoimt of calcium sulfate produced 
 when the Bordeaux is made using the ratio, lOCuSO*: 
 SCaSOi, in the equation given in the notes. At a 
 volum of 800 cc. what is the maximum amount that 
 could dissolv? How much would be left undissolvd? 
 Is the undissolvd portion present in Bordeaux mixture? 
 
 13. How much lime is used in this experiment? 
 How much is used in the reaction? How much dis- 
 solvs in water? What becomes of the remainder? 
 
 14. What substances are in the sohd part of the 
 Bordeaux? What substances are in solution? 
 
 15. Did you observ the formation of a thin white 
 scum on the surface of the ordinary Bordeaux? Ex- 
 plain what it is and how it was formd. Write the 
 equation showing its formation. 
 
 16. What substances cause the copper to dissolv 
 from the Bordeaux mixture? 
 
Bordeaux Mixture 77 
 
 17. What is meant by copper in a positiv ion? 
 Copper in a negativ ion? 
 
 18. In which ion is the copper in copper sulfate? 
 Positiv or negativ? 
 
 19. Why is the liberation of soluble copper salt 
 from Bordeaux delayd by the presence of lime? 
 
 20. How strong a solution of copper sulfate is 
 necessary to kiU fungous spores? To kill plants? 
 
EMULSIONS 
 
 An emulsion contains two inmiiscible 
 liquids and a third colloidal substance mis- 
 cible to a greater or less degree with each of 
 the other two substances. 
 
 I. KEROSENE EMULSION 
 
 Procedure. — Weigh 5 grams of ordinary 
 yellow soap cut into pieces to aid solution and 
 dissolv by the aid of heat in 40 cc. of water in 
 beaker. When solution is complete add 80 
 cc. of kerosene and stir vigorously, or poiu- 
 from one beaker to another, until the emul- 
 sion is complete as evinst by the disap- 
 pearance of the oil. This is a stock solution 
 wh'.ch is diluted with 2-10 parts of water as 
 required. 
 
 Notebook. 
 
 1. Dilute some of the emulsion and examin a drop 
 under the microscope. What is seen? 
 
 2. What substance mixes, to a slight extent, with 
 both the kerosene and the water? 
 
 3. Would the decomposition of this substance 
 destroy the emulsion? Verify by experiment and tell 
 how it was done. 
 
 4. How long, upon standing, before kerosene sepa- 
 rates? 
 
 78 
 
Emulsions 79 
 
 n. MISCIBLE OILS 
 
 There are preparations on the market 
 which contain various oils with the emulsify- 
 ing agent already added. These are ready 
 to use after the addition of water. 
 
 Procedure. — Making sure that all the 
 apparatus used is clean, get 10 cc. of a 
 miscible oil and dilute it with 12 volums of 
 water. If free oil appears on the surface 
 after standing a minute clean the apparatus 
 once more and repeat the experiment. 
 
 NOTES 
 
 Kerosene emulsion is an old remedy for in- 
 sects that do not chew and consequently can- 
 not be poisond. Such sucking insects have 
 to be attackt thru their breathing apparatus. 
 The aphis is an example. Kerosene alone wiU 
 burn foUage badly. The emulsion allows the 
 use of so Uttle kerosene that no harm is done 
 the fohage, there still being sufficient to de- 
 stroy the insect. In pract se the happy 
 medium is sometimes hard to reach. Kero- 
 sene emulsion is practically replaced by solu- 
 tions of nicotine suKate which are obtaind 
 from refuse tobacco. 
 
 The miscible oils are a standard remedy for 
 scale insects and are apphed in the winter or 
 spring before the buds start. It is more 
 
80 Preparation of Substances 
 
 effective than the lime-sulfur as it creeps 
 under the bark reaching all places. One 
 thoro application of these oils will eliminate 
 scale from an orchard. 
 
 When the miscible oil is not properly 
 made by the manufacturer in the first place 
 or when the apparatus used in dilution is not 
 clean some free oil may separate upon stand- 
 ing. If much of any oil appears the material 
 is worthless for spraying as the free oil kills 
 the twigs and small hms by penetrating the 
 bark. 
 
 In the miscible oils the oil and the third 
 substance, a colloid in concentrated form, 
 have been put together and it only remains 
 to add water to make the emulsion. Their 
 condition is comparable to eg-yolk which 
 consists of 30 per cent fat diffused thru col- 
 loidal protein. 
 
 Some idea of emulsions may be gaind from 
 the following remarks. 
 
 It is possible to diffuse droplets of kerosene 
 thru water by violent agitation. Such sys- 
 tems are not stable as the droplets of kerosene 
 soon coalesce and separate. This is said to 
 be due to the great surface tension which is 
 a name for the tendency of small drops to get 
 together and get the most mass under the 
 least siu-face. Soap solution — a colloid — 
 has a much less surface tension than kero- 
 
Emulsions 81 
 
 sene and droplets of kerosene mixt with soap 
 solution will exist separately for a long time. 
 There is a second reason why the kerosene 
 will stay emulsified. The droplet is mixt 
 with the soap colloid. The concentration of 
 the colloid is much greater on the surface 
 of the drop than elsewhere. Now when the 
 droplet of kerosene and soap has reacht an 
 equilibrium, that is, the concentration of the 
 soap solution, inside, on the surface, and out- 
 side the droplets have come into adjustment, 
 a coaUtion of two droplets of kerosene would 
 cause a readjustment of the concentration 
 of the solution on the surface which would 
 require energy. Consequently the droplet 
 once in equilibrium tends to be stable. 
 
 QUESTIONS 
 (To be answerd in the notebook.) 
 
 5. What three substances are necessary in an 
 emulsion? 
 
 6. Name a colloidal substance. 
 
 7. What is the use of miscible oUs? 
 
 8. Which has the greater surface tension soap 
 solution or water? 
 
 9. Define the term surface tension. 
 
 10. Where about a droplet of liquid does a colloid, 
 when present, tend to concentrate?