Class Book 8 feS 1 CoiyriglitN /?/3 COPYRIGHT DEPOSIT. CYANAMID - Manufacture, Chemistry and Uses fcXZZiXX^XXXXXXXXXXXXXXXXXXXXXXXXX«X^XXXXXXXXXX-g § Published by ^ The Chemical Publishing Co. Easton, Penna. f$ Publishers of Scientific Books g| Engineering Chemistry Portland Cement gj IHI IEI W Agricultural Chemistry Qualitative Analysis » g Household Chemistry Chemists' Pocket Manual j| M Metallurgy, Etc. g £I*XXXXXXXXXXXXXXXXXXXXXXXX*XXX«XXX^XXXXXXXXXXX3 CYAN AMID Manufacture, Chemistry and Uses BY EDWARD J. PRANKE, B.Sc. 1913 THE CHEMICAL PUBLISHING COMPANY EASTON, PA. LONDON, ENGLAND : WILLIAMS & NORGATE 14 HENRIETTA STREET, CONVENT GARDEN, W. C. Copyright, 1913, by Edward Hart. (CI.A34 78 61 PREFACE. This volume is intended to be a review of the present knowl- edge of Cyanamid, particularly its chemical and agricultural properties. Its purpose is to render some assistance to the investigator who has neither the time nor the library facilities to enable him to make a thorough study, yet who wishes to broaden his knowledge of Cyanamid. Most of the important literature on this subject is written in foreign languages, and many valuable papers occur in journals not found in the ordi- nary agricultural or chemical library. Moreover, the opinions that have been expressed on almost every phase of the be- havior of Cyanamid are so diversified and frequently so deeply buried in controversy that the casual reader is at a loss to know what to accept as generally established facts. It is hoped that the present volume will give to the reader a consistent ex- planation of Cyanamid that will form the starting point for the acquisition of further knowledge. In order to arrive at an understanding of the principles underlying particular phenomena it is necessary to adopt at the beginning of an investigation some sort of working hypothesis that will account for the observed facts. Every further fact that is acquired must then verify the original hypothesis or the latter must be modified to fit the facts. The constant re- modeling of ideas to agree with observed facts finally leads to a system of knowledge, in which every fact explains to a cer- tain extent every other fact, and in no case contradicts any of them. Such a system of knowledge of Cyanamid, it is be- lieved, is now at hand. The pure chemistry of Cyanamid, its physico-chemical action in the soil, its biological behavior, and its agricultural properties, as presented in this volume, are con- sistent with each other. Such consistency is believed to induce confidence in the validity of the views expressed. Further experiments may make necessary some slight changes, but the general scheme of the properties of Cyanamid may now be con- sidered as quite definitely established. iv PREFACE There is no question but that Cyanamid will play an import- ant part in the future development of agriculture, and that a great deal of research will be undertaken to broaden the knowl- edge of its practical application. Much labor has been wasted in the past by the pursuance of faulty methods, and a great deal of work has been but the duplication of earlier efforts, and has contributed little that was not known before. If the publishing of this book will direct research into the fields that still remain more or less unexplored, and if it is helpful in avoiding the errors of past investigations, its purpose will have been accomplished. Nashville, Tenn. January, 1913. TABLE OF CONTENTS. Preface lu CHAPTER I. Discovery and Manufacture of Cyanamid-. i History of Technical Process I Nomenclature of Cyanamid Industry 3 Manufacture of Commercial Cyanamid 4 Preparation for Use as a Fertilizer 7 Commercial Derivatives 8 CHAPTER II. Preparation and Properties of Cyanamide io Preparation I o Properties T i Action of Heat 1 1 Action of Acids 12 Action of Alkalies 12 Action of Oxidizing and Reducing Agents 13 Other Reactions 13 Metal Salts 13 Dimetal Salts 13 Calcium Cyanamide 14 Acid Calcium Cyanamide 14 Basic Calcium Cyanamide 16 Calcium Cyanamide Carbonate 16 Silver Cyanamide 17 DICYANDIAMIDE 17 Dicyandiamidine 18 CHAPTER HI. Analytical Methods 19 Determination of Total Nitrogen 19 Determination of Cyanamide and Dicyandiamide 20 Caro Method 20 Brioux's Modified Caro Method 21 Determination of Urea 22 Identification of Amidodicyanic Acid 23 Identification of Ammeline 23 CHAPTER IV. Storage of Cyanamid 24 Factory Test on Large Scale 24 Test of Two Bags 25 Chemical Changes in Storage 28 Relative Amounts of Decomposition Products 29 CHAPTER V. Decomposition of Cyanamid in the Soie 32 Factors Involved 32 Experiments of Ulpiani 32 Experiments of Kappen 34 First Stage of Decomposition 37 Second and Third Stages of Decomposition 38 Influence of Concentration 40 Influence of Temperature 43 Influence of Soil at ioo°C 43 vi TABLE OF CONTENTS PAGE Nature of Products formed in Soil at Ordinary Temperatures- 44 Effect of Changing Ratio of Liquid to Soil 46 Influence of Aeration 47 Influence of Electrolytes 48 Nature of Effective Soil Constituents 48 Effect of Zeolites 49 Effect of Carbon 50 Experiments with Natural Colloids 51 Experiment with Sterilized Soil 5 b Conclusions 57 CHAPTER VI. Retention of Cyanamid Nitrogen in Soil- 60 CHAPTER VII. Nitrification of Cyanamid Nitrogen 62 CHAPTER VIII. Toxicity of Fertilizers 65 Meaning of ' ' Poison " 65 Conclusions of Dr. Paul Wagner 66 Other Explanations of Toxic Action 73 Dicyandiamide 74 Formation 75 Decomposition 75 Conversion in Soil 77 Pure Substances and Toxicity 80 Conclusion 82 CHAPTER IX. Agricultural Use of Cyanamid 83 Fertilizer Tests 83 Use as a Weed Destroyer 86 Directions for Application as Fertilizer 87 Use of Complete Fertilizer Mixtures 89 CHAPTER X. Making Fertilizer Mixtures With Cyanamid 90 Mixtures with Ammonium Salts 90 Mixtures with Acid Phosphate 91 Other Mixtures 93 Advantages of Cyanamid in Fertilizer Mixtures 93 Drying Action 93 Preventing Loss of Nitric Nitrogen 93 Preventing Bag-rotting 94 CHAPTER XI. Permanganate Availability of Cyanamid.. 95 Solubility on Filter 95 Solubility in Flasks 96 Rate of Solution in Flasks 96 Neutral Permanganate Method 96 Alkaline Permanganate Method 97 Modified Alkaline Permanganate Method 98 CHAPTER XII. Fire and Water Hazard of Cyanamid 102 Test for Flammable Gases 102 Spontaneous Heating Tests 102 Test with Water 103 Acid Tests 103 Behavior of Product when Heated 104 Test with the Oil Used 104 General Behavior when Treated with Water 105 CHAPTER I. Discovery and Manufacture of Cyanamid. The problem of the artificial fixation of atmospheric nitro- gen has engaged the attention of scientists for the greater part of a century. The rapid growth of the fertilizer industry that has attended the development of agricultural science, and the great increase in the number and extent of chemical industries, during the past fifty years, have emphasized the necessity for artificial methods of maintaining and increasing the world's stock of combined nitrogen. One of the influences that stim- ulated immediate action was the introduction in 1887 by MacArthur and Forest, and at about the same time independ- ently by Siemens & Halske, of Berlin, of the cyanide process for leaching gold and silver from their ores. This discovery produced a strong demand for cyanides, which had hitherto been used to the extent of only a few hundred tons a year, principally in the dye-industry and to a smaller extent in electroplating. Attempts had been made early in the nineteenth century to living about the direct synthesis of cyanogen from atmospheric nitrogen and carbon. Among other processes, that worked out in 1847 by Bunsen and Playfair, in which barium car- bonate was heated in an atmosphere of pure nitrogen, seemed promising, but did not prove to be commercially successful. The introduction of the electric furnace in 1894 by Moissan and by Willson, for the production of carbides on a large scale, afforded a new instrument for further research. Siemens and Halske, among others, at once adopted the use of the elec- tric furnace for the working out of the problem of nitrogen fixa- tion. In 1895, they worked on the process of Prof. H. Meh- ner, which consisted in fusing a mixture of sodium carbonate and carbon and conducting nitrogen through the hot mass. In the same year they took up the process of Prof. Adolph Frank and Dr. Nicodem Caro, which consisted in subjecting a mix- 2 CYAN AM ID MANUFACTURE, CHEMISTRY AND USES ture of barium carbide, sodium hydroxide, potassium hydroxide and carbon at a high temperature to the action of steam and nitrogen. Frank and Caro, with the co-operation of F. Rothe, found in 1895 that dry nitrogen is essential to successful absorption. In 189S it was found that when barium carbide is heated to a temperature of 700 ° to 8oo° C, in the presence of nitrogen, about 30 per cent, of the carbide is changed into barium cyanide and the remainder into barium cyanamide. The re- actions can be represented by the following simple equations : BaC 2 + N 2 = Ba (CN)„ Ba(CN) 2 = BaCN 2 + C. Since it was desired to have all the nitrogen in the form of cyanide, further operations were necessary. The product of the above reactions was fused with soda, when the carbon again reacted with the cyanamide group and produced the cyanide form. The cyanide was leached out with water, and treated with ferrous carbonate to form the ferrocyanide, which was sold as such or fused with sodium to form pure sodium cyanide. The barium carbonate residue was again used to produce barium carbide, as represented by the reactions : BaC0 3 + heat = BaO + C0 2 , BaO + 3C = BaC 2 + CO. The fall in the price of cyanides due to the interruption in the production of gold during the Boer War in South Africa made it necessary to seek cheaper methods of manufacture. It was found that calcium carbide could be manufactured at less cost, and also had the advantage of possessing a lower molecular weight. This carbide required a temperature of from i,ioo° to 1,200° C. for the absorption of the nitrogen, but combined it entirely in the form of calcium cyanamide, without the formation of any cyanide. By fusion with alkaline salts, however, the cyanamide form, in the presence of carbon, readily goes over to the cyanide form, which can be leached out with water, if desired, and be further purified. When sodium chloride is used as the fluxing agent, the resultant mass CYANAMID — MANUFACTURE, CHEMISTRY AND USES 3 contains about 30 per cent, sodium cyanide, and is known as a "surrogate." It is suitable for use directly for the extraction of gold ores. Agricultural experiments with the crude calcium cyanamide showed that this material is suitable for use as a nitrogenous fertilizer, and patents were issued in 1910 to Dr. Albert R. Frank, son of Prof. Adolph Frank, and to Herman Freuden- berg, a co-worker of A. R. Frank, protecting the use of Cyanamid for this purpose. The basic patent protecting the process of manufacture of Cyanamid was issued to Prof. Adolph Frank and Dr. Nicodem Caro in 1908. The large demands of agriculture for cheap nitrogenous fertilizer materials have directed the efforts of the manu- facturers toward the production of Cyanamid rather than of cyanides and other derivatives. At present, the total output of sodium cyanide derived from Cyanamid is only about 2,000 tons per annum, all made in Germany, while the world's pro- duction of Cyanamid is estimated at about 120,000 tons per annum. The factory of the American Cyanamid Company, at Niagara Falls, Canada, now has a capacity of 30,000 tons per annum, and extensions now under way will increase this to 60,000 tons per annum. There are thirteen Cyanamid factories abroad, located in Germany, Italy, France, Switzerland, Austria, Norway, Sweden and Japan. NOMENCLATURE OF CYANAMID INDUSTRY. With the development of the Cyanamid industry there has grown up a nomenclature that is often confusing to the un- initiated. The terms here defined will be understood to have the following meanings throughout this treatise : Lime-nitrogen. — Crude calcium cyanamide, ground to a fine powder after removal from the ovens in which it is formed. It contains about 55 per cent, of calcium cyanamide, CN.NCa, about 2 per cent, calcium carbide, and about 20 per cent, of free calcium oxide. 4 CYANAMID MANUFACTURE, CHEMISTRY AND USES Cyanamid. — This is a trade name for the completely hydrated material prepared for use as a fertilizer in the United States. It contains about 45 per cent, calcium cyanamide, 27 per cent, calcium hydroxide and no carbide. The name is always capitalized and has no final "e." Cyanamide. — The compound represented by the formula CN.NHo. It is sometimes referred to as acid cyanamide, or free cyanamide. Calcium Cyanamide. — The chemical compound of the for- mula CN.NCa, or CaCN 2 , as it is freqently written. Calcium Cyanamid. — The name used by the United States Department of Agriculture and by some State Departments of Agriculture to designate commercial Cyanamid. It is some- times used to indicate the substance represented by the formula CN.NCa, but for the sake of clearness the compound CN.NCa will be called calcium cyanamide in the present paper. Nitrolim. — The trade name for the material sold in England for agricultural purposes. It is a lime-nitrogen to which has been added just enough water to destroy the carbide. Practi- cally all the free lime is present as calcium oxide. Kalkstickstoff. — The commercial material manufactured in Germany for use as a fertilizer. It is similar to nitrolim. Stickstoffkalk. — A crude calcium cyanamide made by nitri- fying a calcium carbide which contains about 10 per cent, of cal- cium chloride. Its manufacture in Westeregeln, Germany, under the Polzeniusz patents was discontinued in 1910. Calciocianamide. — The Italian commercial product, com- pletely hydrated. Cyanamide de calcium. — The French commercial product, completely hydrated. MANUFACTURE OF COMMERCIAL CYANAMID. The first step in the manufacture of Commercial Cyanamid is the preparation of calcium carbide. This is brought about in the usual manner by fusing in an electric furnace a mixture of lime and coke in accordance with the following equation: CYANAMID — MANUFACTURE, CHEMISTRY AND USES 5 CaO + 3C — CaC 2 + CO. The carbide is removed from the furnace at regular inter- vals, is cooled, crushed to a fine powder, and packed in the nitrifying ovens. These are cylindrical, perforated steel cans, set in heat-insulated brick ovens. A carbon pencil through the axis of the can is used to heat the carbide to the combining temperature. On admission of the nitrogen to the cans the following reaction takes place: CaC, + N 2 — CaCN 2 + C. This reaction is accompanied by an evolution of heat which is just about sufficient to maintain the mass at the combining temperature. The commercial calcium carbide used contains about 20 per cent, of impurities, which so influence its physical and chemical properties that the absorption of nitrogen takes place very readily at atmospheric pressure at a temperature of about i,ioo° C. The addition of catalytic agents, principally haloids, suggested by various investigators, is not necessary for the fixation of nitrogen, since the manufacturer can easily regulate the reactions by suitable disintegration of materials and by other mechanical means. Nitrogen is obtained either by fractional distillation of liquid air, or by means of the copper oxide process. In the latter, air is passed through a red-hot mass of finely divided copper, suspended in asbestos or other inert material. The copper combines with the oxygen and allows the nitrogen to pass through. The copper oxide is easily recovered for use by reduction in situ with a suitable gas, such as natural gas. The nitrogen used must be pure and dry, otherwise, at high temperatures, there is destruction of the carbon pencils, and of calcium carbide, according to the following reactions : C + O — > CO, C + CO, — 2CO, C + H 2 0*~ CO + H„ H 2 + CaC 2 — * CaO + C 2 H..„ 3O + CaC 2 — > CaO + 2CO. 6 CYANAMID — MANUFACTURE, CHEMISTRY AND USES Carbon dioxide also destroys the calcium cyanamide with formation of calcium oxide, carbon monoxide and free nitro- gen. The reaction by which calcium cyanamide is formed is reversible: CaC 2 + N 2 = CaCN, + C. The temperature of reversal at atmospheric pressure varies greatly with the composition of the carbide used. Thus the temperature of reversal lies at about 1,360° C., 1 for a crude calcium cyanamide containing 21.1 per cent, combined nitro- gen, and made from a commercial carbide of the following composition : Per cent. CaC 2 82.30 C 1.20 CaO 14.72 CaSi 0.06 Ca 3 Pj 0.07 CaS 0.13 Ferrosilicon 0.72 Not determined 0.80 An increase of the free lime in the carbide greatly lowers the critical temperature. Thus with a carbide containing 75 per cent. CaC 2 the equilibrium point lies at about 1150° C. 2 The effect of nitrogen pressure on the equilibrium point has been investigated by M. Thompson, who found that the tem- perature at equilibrium varies directly as the pressure. 3 Since calcium cyanamide is decidedly volatile at the equilibrium tem- perature, even as low as 1,050° C, and distils to the colder parts of the apparatus the determination of the equilibrium conditions is open to some errors, but these may not be large enough to vitiate the general conclusions that have been drawn. It is owing to the reversibility of the reaction that nitrogen 1 Caro, Chem. Trade Jour., 1909, p. 622. 2 LeBlanc & Eschmann, Zeit. fiir Elek., i9ri, 17, 20-34. 3 Thompson & Lombard, Met. and Chem., Eng. , 1910, 617, 682. CYANAMID — MANUFACTURE, CHEMISTRY AND USES 7 cannot be absorbed by liquid carbides as the latter leaves the furnace, since calcium cyanamide cannot exist at the tempera- ture of liquid carbide. As the carbide cools it becomes practi- cally impermeable to gases and absorption takes place only on the surface to a slight depth. Processes for the nitrifying of a heated mass of lime and coke have not been commercially successful. The energy consumption for the fixation of one ton of nitro- gen as calcium cyanamide is about three horse power years, including the manufacture of the carbide and all subsequent factory operations. PREPARATION FOR USE AS FERTILIZER. Cyanamid finds its principal use in agriculture, as a source of nitrogenous plant food, and for this reason practically all the crude calcium cyanamide is converted into a form more suitable for its incorporation in complete fertilizers. To this end, water is added to the crude material in a rotating cylinder; the one or two per cent, of calcium carbide is decomposed and the lime slaked. This powdered Cyanamid is converted to granulated Cyanamid as follows : A small amount of water is mixed with it, and the damp material is run through brick presses. The resulting bricks harden rapidly, and are stored until the material is to be shipped, when they are run through a series of crushing rolls and screens. The coarse material, which passes through a 15-mesh standard screen and over a 60-mesh standard screen, is practically free from dust, and is known commercially as Granulated Cyanamid. The fine material, mostly smaller than 60-mesh, is either incorporated with fresh powdered Cyanamid and again run through the brick presses, or it is mixed with several per cent of an odor- less oil to reduce the dustiness, and is sold without further treatment. Both grades of Cyanamid are packed in ordinary fertilizer bags, and are distributed in carload lots to manu- facturers of mixed fertilizers. Material so prepared contains nitrogen equivalent to 18 to 20 per cent, of ammonia, and is 2 b CYANAMID — MANUFACTURE, CHEMISTRY AND USES sold on the basis of its nitrogen content, as determined by analysis. The following is a typical analysis of commercial Cyanamid. Per cer.t. Calcium cyanamide CaCN 2 45-92 Calcium carbonate CaCO s 4.04 Calcium sulphide CaS 1 .73 Calcium phosphide Ca 3 P 2 0.04 Calcium oxide, free CaO — Calcium carbide CaC 2 Calcium hydroxide Ca(OH) 2 26.60 Free carbon C 13. 14 Iron and alumina R 2 3 1.98 Silica Si0 2 1.62 Magnesia MgO o. 15 Combined moisture — 3.12 Free moisture H,0 0.35 Undetermined — 1.31 100.00 COMMERCIAL DERIVATIVES. Ammonia. — Steam, at a high temperature and pressure, con- verts calcium cyanamide quantitatively into calcium hydroxide and ammonia, thus forming a convenient source of ammonia for the manufacture of ammonium salts. The carbon, which is in the form of graphite, and the lime, can be used over again for the production of carbide. Nitric Acid. — By the Ostwald process, ammonia can be oxi- dized to nitric acid, mixtures of thoria and ceria being used as catalyzers. No external supply of energy is required in this process. Cyanides. — When calcium cyanamide and carbon are fused together with alkaline salts, in the absence of carbide the cal- cium cyanamide is converted into calcium cyanide: CaCN 2 + C — Ca(CN) 2 . The product of this reaction is called a "surrogate." It is used in the recovery of metals by the cyanide process. The above reaction is completely reversed in the presence of carbides, hence their absence is imperative in this process. CYANAMID — MANUFACTURE, CHEMISTRY AND USES 9 Dicyandiamide. — This derivative is easily prepared by leach- ing the crude calcium cyanamide mass with hot water, pre- cipitating the lime in the filtrate with carbon dioxide, and con- centrating the filtrate. Dicyandiamide is used in the dye in- dustry, and also as a deterrent in nitro-explosives, in place of ammonium oxalate. Other derivatives, such as urea, guanidine, nitro-guanidine, are being made at the Spandau works, in Germany. A process has also been worked out for the production of synthetic indigo by the action of dialkylcyanamides on Phenylgycine and its derivatives. Ferrodur and intensit are special mixtures prepared for metallurgical purposes. Ferrodur is a cementing powder used in place of potassium cyanide for hardening iron and steel in ovens. Intensit is a hardening powder for hardening iron and steel in open fires ; it is used in place of potassium ferro- cyanide. There are other powders of a similar nature with special names differing only in the proportion of active in- gredients that they contain. These products are of consider- able importance to metallurgy, since they are cheap, yet efficient for the purposes for which they are sold. CHAPTER II. Preparation and Properties of Cyanamide. PREPARATION. Free cyanamide, CN.NH 2 , was first obtained by Bineau, in 1838, by the action of ammonia on chlorcyan, but it was not isolated by him from the ammonium chloride with which it was formed. The Italian chemists Cloez and Cannizzaro, 1 in 185 1, effected the separation, and gave the first description of the compound. Their method consists in passing chlorcyan into a solution of ammonia in absolute ether, filtering off the crystalline am- monium chloride and evaporating the solution in vacuo below 40 . The reaction takes place according to the following equation : 2NH, + CNC1 — * CNC1 2 NH 4 + NH. It can also be prepared by the action of freshly precipitated mercuric oxide on thio-urea, in the presence of a little am- monium thiocyanate, which dissolves some of the mercuric oxide as the double thiocyanate, and so renders it more active : NH 2 NH 2 S:C/ "~ C \ + H ' S NH 2 N It is most conveniently prepared from either commercial sodium cyanamide or commercial calcium cyanamide. From Commercial Sodium Cyanamide. 2 — Twenty-five grams of the salt are gradually added to 37 grams of hydrochloric acid (sp. gr. 1.19) with strong cooling, and the water is re- moved by distillation in vacuo below 40 C. The residue solidifies on cooling; it is extracted with ether, the ether dis- tilled off from the solution, and the cyanamide caused to 1 Compt. rend., XXXII, 62. A, 78, 229, and Leibig's Annalen 78, 229. 2 Caro, Schiick, Jacoby, Zeit Angew Chem. 1910, XXIII, 2405, 2417. CYANAMID — MANUFACTURE, CHEMISTRY AND USES II crystallize by cooling. It is purified by recrystallization from ether. Yield about 5 grams. From Commercial Calcium Cyanamide. — Fresh commercial Cyanamid or better, the unhydrated lime-nitrogen, is extracted with cold water (solubility about 0.9 grams nitrogen in 100 cc. water). The calcium is removed either with oxalic acid or aluminium sulphate, but preferably with the latter. After re- moval of the calcium sulphate and alumina by filtration, the filtrate is evaporated in vacuo below 40 , and the residue ex- tracted with ether. It can be purified by recrystallization from ether. PROPERTIES OF CYANAMIDE. Cyanamide, 1 CN.NH,, most probably has the formula ,NH, C <^ , although in a very few reactions it seems to act as if it were carbodiimide, Cx" . It is a colorless, crystal- line solid, which melts at 41-42 C, as usually prepared. It can be undercooled to 12 without solidifying. On stirring with a sharp-pointed glass rod the undercooled liquid freezes. The carefully purified substance melts sharply at 46 C. 2 It is easily soluble in water, alcohol and ether, and is volatile in steam. It is slightly soluble in carbon disulphide, chloroform and benzol. Action of Heat. — Pure cyanamide is perfectly stable at ordi- nary temperatures, but polymerizes slowly on heating above its melting point. Impure cyanamide polymerizes slowly at ordinary temperatures. The principal polymer is dicyandia- /NH. mide, NH: C<( >CN, or (H 2 CN 2 ) 2 , which is probably X NH X cyan-guanidine. By strong heating, other derivatives are 1 Sidgwick, Organic Chemistry of Nitrogen, p. 216, (Oxford, 1910). - G. Henschel, Diss. Univ. of Leipzig, 1912. 12 CYANAMID MANUFACTURE, CHEMISTRY AND USES formed, the most important of which are, the polymer N //\ Tricyantriamide or Melamine H,N — C C — NH.„ and Me- I II N N %/ C NH 3 lam, C 6 H,N n , and Mellon, C 6 H 3 N a . Ammonia is evolved during the formation of these bodies. By the action of super- heated steam the conversion of cyanamide to ammonia is almost quantitative. Action of Acids. 1 — Cyanamide reacts readily with acids ; with nitric acid forming urea nitrate (95 per cent, conversion) ; with sulphuric acid and phosphoric acid giving mostly urea, (about 95 per cent, conversion) together with some ammeline, C 3 N 3 (NH 2 ) 2 OH; ammelide, C 3 N 3 (NH 2 ) (OH) 2 ; possibly cyanuric acid, C 3 N n (OH) 3 , and some ammonia. Cyanamide combines directly with the haloid acids. It com- bines slowly with free H 2 S, readily with yellow ammonium sulphide, with formation of thio-urea. Thio-urea is also formed by the action of thioacetic acid on cyanamide in alcoholic solution. Acetic acid produces principally ammo- nium acetate (about 80 per cent, conversion) and some urea. Action of Alkalies. 2 — The strong alkalies KOH or NaOH in aqueous solutions produce almost entirely urea, with no trace of dicyandiamide ; weak alkalies, NH 4 OH or MgO, pro- duce dicyandiamide almost exclusively at first, and then ammonia. CaO, however, produces a mixture of urea, dicyan- diamide, ammeline, amidodicyanic acid I O : Q.C ) ,. v X NH - CN 7 ammonia and other bodies. 1 Ulpiani, Gas Chim., Ital. II, No. 4, 358-417. 2 Beilstein's Handbuch der Organische Chemie. CYANAMID — MANUFACTURE, CHEMISTRY AND USES 1 3 Hence, with strong acids and strong bases, cyanamide in aqueous solutions forms principally urea ; with weak acids principally ammonium salts; with weak bases dicyandiamide, which decomposes further to ammonia; with lime, a mixture of urea, dicyandiamide and other derivatives. Action of Oxidizing and Reducing Agents. — In the chapter on availability it will be shown that oxidizing agents convert the nitrogen of cyanamide or its derivatives into forms more insoluble in water and less easily decomposed by strong alkalies. By the action of zinc and hydrochloric acid, cyanamide yields ammonia and methylamine : CN. NH 2 + H 2 •— CNH -f NH. P CNH + 2H, — CH 3 ,NH r On heating with potassium nitrite solution a violent reaction takes place, and C0 2 , N 2 and dicyandiamide are produced : 4 CN.NH 2 + 4 KN0 2 — * 2K 2 C0 3 + 4 N 2 + (CN.NH 2 ) 2 + 2 H 2 0. Other Reactions. 1 — In cyanamide, either one or both of the hydrogen atoms can be displaced by metals, alkyl or aryl groups, or by alcohol or acid radicals. It combines with amino-acids, especially in the presence of ammonia. It com- bines with ammonium chloride at high temperatures, forming guanidine hydrochloride. Heated with ammonium sulphide it yields guanidine hydrosulphide. It combines directly with cyanogen to form a yellow, amorphous powder. With potas- sium cyanate it forms potassium amidodicyanate, K.C 2 H 2 N 3 0. It combines directly with chloral, and also with aldehydes, but with the separation of water. Metal Salts. — The dimetal salts of the alkali metals can be prepared only in the dry way, since in aqueous solution they lose one of the metal ions by hydrolysis. Thus, Na 2 CN 2 in aqueous solution yields NaHCN 2 : Na 2 CN 2 + H 2 = NaHCN 2 + NaOH 1 Beilstein, Handbuch der Org. Chem. 14 CYANAMID MANUFACTURE, CHEMISTRY AND USES Na 2 CN 2 on fusion with carbon yields sodium cyanide: Na 2 CN, + C <~ 2NaCN. ,NCa Calcium Cyanamide, CaCN 3 or C^ , can be made by the fusion of calcium cyanate: 1 Ca (CNO) 2 — CaCN 2 + C0 2 or by fusion of cyanamide or its polymers with calcium oxide. Calcium cyanamide forms colorless crystals which sublime at about 1,090° C. at atmospheric pressure. It is insoluble in alcohol, but easily soluble in water (about 2.5 g. in 100 cc. water at 25° C). Upon solution of the calcium cyanamide in water it is directly hydrolyzed into the acid calcium cyanamide and calcium hydroxide. 2 CaCN, + 2 H,0 — Ca(CN.NH) 2 + Ca(OH) 2 . That such hydrolysis takes place as indicated by the equa- tion is shown by the relative amounts of lime and nitrogen existing in solutions of calcium cyanamide. C. Ulpiani 1 inves- tigated the relation of lime to nitrogen in a solution of calcium cyanamide kept at a constant temperature for several weeks. At intervals of several days determinations were made of total nitrogen, nitrogen in the form of cyanamide, and calcium in solution. It was noted that crystals of pure calcium hydroxide, as determined by analysis, were deposited on the walls of the vessel after a day or two. The quantities of lime and nitrogen found in the solution are shown in Fig. 1. Since the solubility of calcium cyanamide is much greater than that of calcium hydroxide, a concentrated solution of calcium cyanamide is, after hydrolysis, saturated with respect to calcium hydroxide. In addition, there is present lime as a calcium compound of cyanamide. If this compound is cal- cium acid cyanamide, Ca(CN.NH)._,, there will be in solution one atom of calcium to four of nitrogen, or 56 parts by weight 1 Beilstein loc cit. 2 Rend. Soc. Chim. di Roma, n. 4 (1906). CYANAMID MANUFACTURE, CHEMISTRY AND USES 15 of CaO to 56 of N, or equal weights of each. By reference to the curves in Fig. i it is seen that if the ordinate represent- ing the amount of CaO present as Ca(OH) 2 is subtracted from the ordinate of total CaO, the ordinate of CaO combined in other forms (with cyanamide) would coincide with the ordinate of nitrogen present as cyanamide; that is, the amounts of CaO and N present are in the relation demanded by the formula Ca(CN.NH) 2 . On long standing of the solution, the acid salt Ca(CN.NH) 2 decomposes, forming principally urea, some dicyandiamide, «5 D-Total^ OaO- Total H- aa Cyanamide t* N \ N \ .«« \ \ < N \ a \ \ < \ \ 3 \ \ \ \ \ \ Temp. 35°C \ V \ ^\ 4. V ^^ 1 ^^ . w &* ""-•s. ** >^ CaO- as ~~ ----__ 0a(0H) 2 """" — — —. «a c 4 & 12 16 ZO Z4 Days Fig. I.— Variation of nitrogen and calcium in a solution of lime-nitrogen. and small quantities of melamine, amidodicyanic acid and ammonia. The dicyandiamide diminishes slowly, and finally probably disappears entirely. This is shown in the following analyses by G. Liberi 1 of a solution made by extracting lime- nitrogen containing 18.63 P er cent, cyanamide nitrogen, with twenty times its weight of cold water. The nitrogen figures are given as a percentage of the dry lime-nitrogen. 1 Ann. R. Staz. Chim. Agrar. Sper di Roma., 191 1, Vol. V, Series II. l6 CYANAMID — MANUFACTURE, CHEMISTRY AND USES Nitrogen in solution As cyanamide As dicyanamide After Per cent. Per cent. I day 1456 0.70 3 days 11.76 1.54 6 days 9.10 2.84 11 days 5.18 2.24 18 days 1.75 1. 71 31 days 0.00 1.25 45 days 0.00 0.84 58 days 0.00 0.53 76 days 0.00 0.23 Basic calcium cyanamide is formed in solutions containing an excess of lime: N N /// /// C v + Ca(OH) 2 — * C v /CaOH X NCa X N< ^CaOH It can be obtained from lime-nitrogen by extracting with a small portion of water, filtering, and allowing the solution to stand several hours. Long, needle-shaped white to trans- parent crystals separate out on the walls of the vessel. Filter with suction in the absence of carbon dioxide (under a bell- jar). Dry under a bell-jar over caustic potash. This salt is almost insoluble in water. In the dry condition it is stable at ordinary temperatures, but when heated to 120 C. it rapidly decomposes to dicyandiamide and calcium hydroxide. Calcium cyanamide carbonate 1 is readily formed by the action of carbon dioxide on calcium cyanamide in the presence of moisture. It can be prepared by extracting lime-nitrogen with one and one-half times its weight of water, filtering and bubbling CO, through the filtrate. In about half an hour a white precipitate forms, which can be filtered and washed with alcohol or ether. 1 Ulpiani, loc cit. CYANAMID — MANUFACTURE, CHEMISTRY AND USES \"J N /// CaCN 2 + C0 2 + H 2 — * C x ,Ca X N< | 5 H 2 0. X C0 2 Calcium cyanamide carbonate is somewhat insoluble in water, and insoluble in alcohol and ether. On standing in dry air it slowly loses 4 molecules of water of crystallization, and at the same time decomposes to dicyandiamide and calcium car- bonate. The same change takes place rapidly when heated : N /// 2C V /Ca.5H.,0 — * (CN.NH,) 2 + 2 CaC0 3 + 8H 2 X C0 2 Silver Cyanamide, C N.N Ago. — Obtained on treating an ammoniacal solution containing cyanamide with very dilute (1 : 150) solution of silver nitrate. 1 More concentrated solu- tions yield a mixture of this salt and double or basic silver salts, containing, however, all the cyanamide. Silver cyanamide is an amorphous, yellow substance, almost insoluble in dilute ammonia or caustic potash at ordinary tem- peratures, soluble in hot ammonia solutions, easily soluble in dilute nitric acid. It is easily soluble in alkali cyanide solution, but if an excess of silver nitrate is added, a white, crystalline double salt of silver cyanide and silver cyanamide is precipi- tated. When potassium hydroxide is added to a cyanamide solution containing silver nitrate in excess an insoluble mixed precipi- tate of silver cyanamide and brown silver oxide is formed, which contains all the cyanamide nitrogen. .NH 2 Dicyandiamide," NH:C( .—Obtained by extract- X NH.CN ing lime-nitrogen with boiling water, concentrating the solu- 1 Caro, Schiick, Jacoby, loc cit. 2 Beilstein, loc cit. l8 CYANAMID MANUFACTURE, CHEMISTRY AND USES tion to a syrup and allowing to crystallize. It forms trimetric plates or thin leaves, melting at 205 C. It is decomposed by heating, with evolution of ammonia and formation of mela- mine, melam, and other derivatives. Dicyandiamide is some- what easily soluble in water and alcohol, but almost insoluble in ether. It combines with ammonium chloride at 150 , giving diguanide hydrochloride, C 2 H 7 N 5 HC1; with HC1 at 150 gives guanidine hydrochloride, CH 5 N 3 HC1 ; on boiling with baryta it gives amidodicyanic acid and ammonia ; with zinc and HC1 yields methylamine and ammonia ; with H 2 S it gives guanyl- thiourea; on heating with urea or cyanuric acid it forms ammelin, C a H;;N 5 0, and ammonia. Treated with weak or strong acids, or with strong alkalies, dicyandiamide goes over to dicyandiamidine, /NH 2 NH : C<^ , caustic crystals, easily soluble in ^NH.CO.NH, water and alcohol. Dicyandiamide, treated with silver nitrate solution, forms additional compounds containing, according to the conditions, one, two and three molecules respectively, of dicyandiamide per molecule of silver nitrate. Cold caustic potash added to a dicyandiamide solution containing sufficient silver nitrate causes a white to brown mixture of precipitates of silver dicyandiamide and silver oxide. Silver dicyandiamide is slightly soluble in water, easily soluble in ammonia, soluble in hot nitric acid ; on prolonged boiling with caustic potash is converted into silver cyanamide, CN.NAg 2 , and cyanamide, which polymerizes again to dicyandiamide. If silver nitrate, then nitric acid, is added to a solution of dicyandiamide, a white precipitate is formed, insoluble in cold, soluble in hot nitric acid or in excess of ammonia. (Iden- tification in mixtures of cyanamide and dicyandiamide. Cyan- amide, it will be remembered, gives a yellow precipitate with dilute silver nitrate, soluble in nitric acid, but insoluble in ammonia.) CHAPTER III. Analytical Methods. DETERMINATION OF TOTAL NITROGEN IN CYANAMID. Practically all the Cyanamid manufactured in this country prior to January I, 1912, contained about 23 per cent, of its total nitrogen in the form of nitrates. Hence, for the deter- mination of total nitrogen in such Cyanamid it is necessary to use a method that will determine nitrate nitrogen as well as nitrogen derived from Cyanamid. For this purpose the Official Gunning method, modified for nitrates, is suitable. The period of digestion should be at least five hours. The influ- ence of the period of digestion is shown in the following values obtained on a sample of Cyanamid containing nitrates : Per cent, nitrogen 2 hours digestion 15.61 3 " " I5-76 4 " " 16.03 5 " " 16.06 All the Cyanamid manufactured in this country since Jan- uary 1, 1912, is free of nitrates, and therefore, the simple Kjeldahl or Gunning method may be used. The Gunning, which is in general use, is carried out as follows: REAGENTS REQUIRED. N/2 (Half-normal) Sulphuric or hydrochloric acid. N/10 (Tenth-normal) Sodium hydroxide, or ammonium hydroxide. Sulphuric acid, C. P., specific gravity 1.84. Sodium hydroxide, saturated solution. Potassium sulphate, C. P. Cochineal indicator. To determine nitrogen weigh out 0.7 gram of finely ground sample. Each cc. of half-normal acid is equivalent to 1 per 20 CYANAMID — MANUFACTURE, CHEMISTRY AND USES cent, nitrogen. To determine ammonia weigh out 0.85 gram of finely ground sample. Each cc. of half-normal acid is equivalent to 1 per cent, ammonia. Procedure. — Place the carefully weighed sample in a Kjeldahl flask of about 300 cc. capacity. Add 10 grams of ground potassium sulphate. Shake until well mixed with the sample. Add 25 to 30 cc. of concentrated sulphuric acid and shake until well mixed. Heat slowly for 30 minutes, then heat with a full flame for one and one-half hours. Cool, dilute, and transfer to a distillation flask. (Distillation can be made from the digestion flask if desired.) Add an excess of sodium hydroxide, and distil 200 cc. into a measured quantity of the standard half-normal acid, containing some cochineal indi- cator. Titrate the excess of acid with tenth-normal alkali. DETERMINATION OF CYANAMIDE AND DICYANDIAMIDE. Caro Method.— Of the various methods for determining cyanamide and dicyandiamide, that of Caro 1 seems to be the best. The reagents used are as follows : (a) Silver acetate solution. 100 grams of silver acetate are placed in a liter flask, covered with 400 cc. of 10 per cent, ammonium hydroxide, and the flask is filled to the mark with water. (b) 10 per cent, solution of potassium hydroxide. The procedure is as follows : 5 g. of Cyanamid or lime- nitrogen is agitated by hand or in a shaking machine with 450 cc. of water for about 2V 2 hours, and the flask filled to 500 cc. An aliquot part (250 cc.) is treated with ammonia until it smells strongly thereof and then with silver acetate solution in excess. The precipitate of silver cyanamide salts (p. 12), after shaking and standing a little while, is gathered on a nitrogen-free filter, washed with water until no ammo- nium salts run through, and the nitrogen in it is determined by the Kjeldahl method. 1 Caro, Schiick, Jacob y — loc cit. CYANAMID — MANUFACTURE, CHEMISTRY AND USES 21 An aliquot part of the filtrate, now free from cyanamide, is treated with potassium hydroxide solution in excess, and is boiled until no more ammonia comes off. The precipitate con- tains all the dicyandiamide and some silver oxide. Dilute the solution with an equal volume of water, filter on a nitrogen- free filter, wash with some water, and determine nitrogen in the precipitate by the Kjeldahl method. Brioux 1 claims that the boiling of the strongly alkaline cyanamide-free solution containing the precipitate of silver dicyandiamide and silver oxide causes a conversion of about 1.5 per cent, of the total nitrogen of the dicyandiamide, and he has modified the method so as to obviate this error. His method is briefly as follows : Brioux's Modified Caro Method. — Extract the soluble nitro- gen from 1 or 2 grams of finely ground sample by frequent shaking for three or four hours in a flask with 250 cc. cold water, and filter through a dry filter without washing. In one aliquot portion of 100 cc. of the filtrate determine cyana- mide and dicyandiamide, and in the other determine cyanamide alone. For combined cyanamide and dicyandiamide nitrogen : For each 0.1 gram nitrogen (approx.) in the solution add 20 cc. of 5 per cent, silver nitrate solution. Then add 20 cc. of 10 per cent, potassium hydroxide solution. A brown precipi- tate of mixed cyanamide and dicyandiamide salts forms. Filter and wash with cold distiled water. Determine total nitrogen in the residue by the Kjeldahl process, substituting 1 gram copper sulphate in place of the mercury. For cyanamide nitrogen : In the other portion of the extract from the sample add for each 0.1 gram nitrogen, 20 cc. of 5 per cent, silver nitrate solution. Add an excess of ammonia. A yellowish-brown precipitate forms. Filter and wash with water slightly ammoniacal, finishing with cold distilled water until the washings are free from soluble silver salts. Dissolve the residue in dilute nitric acid (1:2) and determine silver 1 Annales de la Science agron. francaise et etrangere, April 1910. 22 CYANAMID — MANUFACTURE, CHEMISTRY AND USES by the sulphocyanate or other convenient method. One atom of silver corresponds to one atom of nitrogen. In both the Caro and Brioux methods, however, from 25 to 30 per cent, of the urea present is precipitated in caustic potash solution as silver salts along with the dicyandiamide. 1 Since Cyanamid frequently contains more urea than dicyandiamide this occasions considerable error. Henschel 2 found that by the Caro method about 7 per cent, of the nitrogen as dicyandiamide was converted to other forms, presumably by the action of the hot caustic alkali in boiling off the the ammonia. The total nitrogen was not diminished, hence the urea (?) nitrogen was increased at the expense of the dicyandiamide. Determination of Urea.— Caro determines the total nitrogen remaining in the filtrate from the dicyandiamide separation and designates it as urea. Since, however, some of the urea is precipitated along with the dicyandiamide and since the nitrate may also contain other derivatives, the method can hardly be considered as satisfactory. Caro also recommends Liebig's titration method for the determination of the urea in the filtrate. Ulpiani, 3 however, claims that the mercuric nitrate used for the precipitation of urea in this method, also pre- cipitates cyanamide and dicyandiamide, if present, dicyandia- midine. amidodicyanic acid, ammonia, ammonium salts, and probably all nitrogen compounds found in lime-nitrogen. Ulpiani suggests the direct solution of the sample of lime- nitrogen or Cyanamid with alcohol, but since dicyandiamide as well as urea is soluble in alcohol, this procedure would not simplify the problem very much. The question of analysis of cyanamide derivatives is much in need of scientific study, but for the present it will be sufficient for most purposes to determine total nitrogen in a given sample of Cyanamid, then to determine cyanamide and 1 Brioux, loc. cit. 2 Georg Henschel, Das Verhaltendes technischen Calciumcvanamides bei der Aufbewahrung sowie unter dem Einfluss von Kulturboden und Kolloiden — Diss. Univ. Leipzig. 1912. 3 Ulpiani, loc. cit. CYANAMID — MANUFACTURE, CHEMISTRY AND USES 21, dicyandiamide by the Caro method, and to consider the differ- ence as being equivalent to the original urea. The other derivatives usually occur in such small quantities that they are practically negligible. IDENTIFICATION OF AMIDODICYANIC ACID. The following is based upon the procedure given by Ulpiani 1 for the identification of amidodicyanic acid. Remove the cyanamide and dicyandiamide (Brioux's method), carefully neutralize the filtrate with sulphuric acid, and treat with copper sulphate. In a day or two greenish crystals of copper amidodicyanate separate out. Sometimes there is also a slight precipitate of copper salts of cyanamide and dicyandiamide, which are easily washed out by rapid de- cantation, since the copper amidodicyanate is much heavier. The copper amidodicyanate has the formula Cu(Q,H 2 N 3 0) 2 4H0O. It is further identified by mixing the copper salt with ammonia and treating the solution with hydrogen sulphide. The copper sulphide is filtered off, and the filtrate concentrated, when a white precipitate of thiobiuret is formed. This loses water at ioo° and melts at 185 . With copper sulphate a solution of thiobiuret gives a white precipitate. IDENTIFICATION OF AMMELINE. Ulpiani 2 claims that ammeline can be detected in old lime- nitrogen as follows : Extract the sample with dilute nitric acid. Filter and just neutralize the filtrate with ammonia. A white precipitate of ammeline is obtained, insoluble in water, soluble in alkalies or mineral acids. Analysis should show the solid to have the formula C 3 H, 5 N 5 0. 1 Gaz Chim. Ital 1908, II No. 4, 358-417. 2 loc. cit. CHAPTER IV. Storage of Cyanamid. On exposure to the atmosphere, Cyanamid absorbs moisture and carbon dioxide. This absorption of foreign material, of course, increases the weight of the exposed sample, and hence decreases the percentage of the original constituents. Neglect to observe this increase in weight and corresponding decrease of percentages led some early investigators to declare that nitro- gen is lost when Cyanamid is stored for any great length of time. It has lately been shown by carefully conducted experi- ments in the laboratory as well as on a large scale, that under conditions of storage customary for fertilizer materials there is no loss of nitrogen. Factory Test. — When Cyanamid is stored in ordinary burlap bags only the exposed surfaces can receive moisture and carbon dioxide, and penetration into the interior of the bag or pile is necessarily difficult. Even in damp climates, such absorption is not very large when considered in its relation to the entire pile. Thus, a pile of Cyanamid weighing 94.083 pounds, and analysing 15.63 per cent, nitrogen was stored in a warehouse over and a few feet above the surface of the St. Johns river at Jacksonville, Florida, from July 7th to January 13th, and was then carefully weighed and sampled by the purchaser, the sample being taken from different portions of two out ot every three bags in the lot. Per cent, increase Weight in weight. 7 mo's Original 94.083 .... After 7 months- 101,506 7.9 Hence, even in this damp climate, where rains occur almost daily during the summer months, the rate of increase of weight is a little more than one per cent, a month, while the nitrogen content remains constant. Analysis nitrogen I5-63 Pounds nitrogen 14,705 14-52 14,740 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 25 Test of Two Bags. — A test on a smaller scale was made by the author, at Niagara Falls, Ontario, in 191 2. Two ordinary burlap bags, each holding about 150 pounds of Cyanamid hydrated on November 12, 191 1, were exposed November 17, 191 1, on a raised platform made of 4-inch strips spaced 4 inches apart. The room was dry, well-ventilated by an open window, and kept most of the time between io° and 35 C. Samples were drawn and the weight of the bags was taken just before they were laid out on the platform. At the end of each period of exposure as noted below, the bags were carefully weighed, and the contents were removed. After thorough mixing of the material a sample was drawn, and the bags were refilled, tied, weighed, and again laid out on the platform for further exposure. The following data were obtained: Bag A. — Analvses. Moisture Per Sample drawn cent. Nov. 17, 191 1 0.00 Dec. 17, 1911 0.40 Jan. 17, 1912 0.47 Feb. 17, 1912 0.46 May 17, 191 2 0.67 Carbon dioxide Per cent. Nitrogen Per cent. Calcium Per cent. N Ratio — — Ca 1-75 16.54 40.34 O.4100 2.12 16. II 39-94 O.4095 2-75 16. II 39-34 O.4095 2.87 I5-96 33-94 O.4099 4-05 I5-69 37-94 O.4136 Weights. Per cent. gain in weight Weight Gain in since pounds weight previous Date net pounds weighing Nov. 17, 1911 148.25 — — Dec. 17, 1911 x i50-75 2.50 1.69 " " " 2 i49- 2 5 Jan. 17, 1912 150.50 1.25 0.84 " " " i49-5o Feb. 17,1912 150.50 1. 00 0.67 " " " 150.00 May 17, 1912 i53- 2 5 3-25 2.17 1 Before sampling. 2 After sampling. Per cent. Per cent. nitrogen calcu- lated Per cent. nitrogen found nitrogen gained or lost — 16.54 — 16.266 16.31 + 0.04 16. 131 l6.II — 0.02 17.024 I5-96 — O.06 I5-683 I5-69 + O.OI 26 CYANAMID — MANUFACTURE, CHEMISTRY AND USES Bag B. — Analysis. Moisture Per Sample drawn cent. Nov. 17, 19 1 1 O.OO Dec. 17, 191 1 0.43 Jan. 17, 1912 0.44 Feb. 17, 1912 0.46 May 17, 1912 0.69 Carbon dioxide Per cent. i-75 2.10 2.70 2.83 3-9 6 Nitrogen Per cent. 16.34 16.09 15.87 I5-70 I5-50 Calcium Per cent. 40.53 39-94 39-35 38-94 38.76 . N Ratio—- Ca 0.4031 0.4029 0.4033 0.4031 0.3999 Weights. Weight Gain in pounds weight net pounds Nov. 17,1911 149.00 Dec. 17, 1911 '151-75 2.75 " " " 2 i5o.75 Jan. 17, 1912 152.25 1.50 " " " 151-25 Feb. 17,1912 I5I-75 0.50 " " " 151-25 May 17, 1912 154-75 3-5° Per cent. gain in weight since previous weighing I.84 O.99 0-33 2.31 Per cent, nitrogen calcu- lated 16.046 15.890 15.838 15.480 Per cent. nitrogen found 16.34 16.09 15.87 I5-70 I5-50 Per cent. nitrogen gained or lost +O.04 — 0.02 — O.14 +0.02 The addition of free moisture, chemically combined moisture, and carbon dioxide necessarily increases the weight of the sample, and hence causes a proportionate decrease in the percentages of other constituents. It is evident that calcium cannot escape from the stored material either by volatilization, since calcium compounds require at least a red heat before they vaporize appreciably, or by leaching, since the mass re- mains practically dry for years. The decrease in calcium per- centage must therefore be due solely to the addition of other matter, and the ratio of the calcium percentages before and after exposure is equal to the inverse ratio of the weights be- fore and after exposure. Thus in bag A the ratios are 40. ■xa 106.^2 •> , 1 • r , - — — = = — or there has been an increase of 6.32 per cent. 37.94 100.00 on the original weight. As shown by the weighings, the in- 1 Before sampling. 2 After sampling. CYANAMID — MANUFACTURE, CHEMISTRY AND USES 2"J crease of weight was 5.46 per cent, of the original weight. The failure of the two results to check more closely is due to the difficulty of making accurate calcium determinations in Cyanamid. Since the absolute quantity of calcium remains constant in the mass exposed, it follows that if the absolute quantity of nitrogen present do not vary, the ratio of nitrogen to calcium must remain constant. Inspection of the data obtained as described above shows that this is actually the case within sampling and analytical limits of error. Recapitulating the results by analysis and by the weights we have : Increase in weight Variation of nitrogen By Ca ratios b y weighing By N/Ca ratio By weighing Bag A. ••• 6.32 5-46 +O.14 -fo.oi Bag B. ... 4.77 ■ •• 5-54 5-57 5-5i — O. IO -fO.02 Average +0.02 + O.OI5 There has therefore been no loss of nitrogen under ordinary factory conditions of storage, even in the case of a single exposed bag, which exposes a relatively larger surface per pound of material than a large pile would expose. Of the 5.5 per cent, increase in weight, approximately 0.7 per cent, is due to the addition of free moisture, 2.5 per cent, to addition of carbon dioxide, and 2.3 per cent, to addition of combined water; or, of the total increase in weight, about 13 per cent, is due to free moisture, 45 per cent, to carbon dioxide, and 42 per cent, to chemically combined water. In the analyses given above, free moisture was determined by the decrease in weight of a sample heated 5 hours at ioo° C, in a drying oven free of carbon dioxide. The "combined" water is, properly speaking, not present as water at all, but represents water which has acted hydrolytically upon calcium cyanamide with the production of various organic derivatives. Such hydrolyses are in the main irreversible by drying. The increase in weight suffered by a sample of Cyanamid during storage cannot, therefore, be determined by simply correcting final analyses to the so-called "dry basis," since such a correc- 28 CYANAMID — MANUFACTURE, CHEMISTRY AND USES tion is only a small portion of the true correction required. The true increase in weight is best determined by direct weighing of the initial and final sample, or by comparing the calcium content of the initial and final samples. The latter involves very accurate calcium determinations, if the results are to be significant. The absorption of "combined water" and of carbon dioxide takes place for the most part in accordance with the follow- ing equations, which probably account for the formation of dicyandiamide, urea, calcium cyanamide carbonate, and cal- cium carbonate: 2 CaCN 2 + 2H 2 = Ca(CN.NH) 2 + Ca(OH) 2 , Ca(CN.NH), + 2H 2 = (H 2 CN 2 ) 2 + Ca(OH) 2 , CaCN, + 3 H 2 = CO(NH 2 ) 2 + Ca(OH) 2 , CaCN, + C0 2 + H 2 = CaCN 2 .C0 2 .H 2 0, Ca(OH) 2 + C0 2 = CaC0 2 + H,0. After long periods of exposure there are formed slight amounts of secondary derivatives, so that old Cyanamid will contain the following substances : Calcium cyanamide CaCN 2 Acid calcium cyanamid Ca(HCN 2 ) 2 Basic calcium cyanamid CaCN 2 .Ca(OH) 2 Calcium cyanamide carbonate CaCN 2 C0 2 .H 2 Dicyandiamide ( H 2 CN 2 ) 2 Urea CO(NH 2 ) 2 Amidodicyanic acid H 3 C 2 N 3 (slight amounts) Melamine (H 2 CN 2 ) 3 (slight amounts) Ammeline H 5 C 3 N 5 (slight amounts) Ammonium hydroxide NH 4 OH (traces) The following scheme shows the relation of some of these forms to each other, and a possible mechanism for their deriva- tion from calcium cyanamide : CYANAMID — MANUFACTURE, CHEMISTRY AND USES 2$ */ / NCa + 2FL0 ~N Calcium cyanamide. NH, Cyanamide. + 2 H 2 0C< .NH„ C=NH >H + H >° Dicyandiamide. C-NH C=NH Melamine. V / NH 2 N Cyan- amide. 2H,0 + H a — /NH 2 / \ Urea. /NH, Nnh Amidodicyanic acid. /NH 2 C=NH Nnh c=o Nnh CC ~^N Ammeline. Ca(OH) r NH. / CO, \ NH t Ammonium carbonate. + NH 3 . + NH 3 . Relative Amounts of Decomposition Products. — The relative amounts of these decomposition products has been studied in only a few cases, since the total amounts become appreciable only under extraordinarily severe conditions of moisture. A test of this kind is reported by Brioux. 1 1 Annales de la Science agronomique francaise et etrangere, April, 1910. 30 CYANAMID — MANUFACTURE, CHEMISTRY AND USES A sample of lime-nitrogen was exposed on a watch-glass in a bell-jar, the atmosphere of which was kept saturated with moisture by a beaker of water alongside the watch-glass. The 10 gram sample after 8 months exposure weighed 18.75 grams. The analyses before and after exposure are as follows, the third column showing the results corrected to allow for in- crease in weight. After Before After exposure exposure exposure corrected Total nitrogen 17.08 8.99 16. S4 Insoluble nitrogen 1.30 0.38 0.71 Soluble nitrogen in form of Cyanamid I5-Q5 0.14 0.26 Soluble nitrogen in form of Dicyandiamid 0.25 6.87 12.87 Soluble nitrogen in "other forms " 0.48 1.60 3.00 The loss of nitrogen, in the form of free ammonia, has apparently been 0.24 per cent. The soluble nitrogen in "other forms" consists principally of urea, with a small amount of amidodicyanic acid and ammeline. The above test is unusually severe, and has little bearing upon the question of the storing qualities of Cyanamid. Under similar circumstances it takes less than a week for sodium nitrate, ammonium sulphate and calcium nitrate to entirely dissolve in the moisture they absorb, while basic calcium nitrate becomes pasty and sticky in the same time. The Cyanamid, on the other hand, is still in good mechanical con- dition at the end of eight months. A similar test but less severe, and therefore more nearly approaching conditions that may occur in storage on a factory scale, is the following experiment by G. Henschel. 1 10 to 11 grams of commercial Cyanamid was placed in a thin layer on a watch-glass of about 8 cm. diameter, and set in a desiccator jar, in which was a beaker with concentrated sulphuric acid and another with distilled water. This provided a constant circulation of moist air. In addition, for an hour 1 Das Verhalten des teehnisclien Calciumcyanamides bei der Aufbewalirung sowie unter dem Einfluss von Kulturboden und Kolloiden. Inaugural-Dissertation-Univ. of Leipzig, 1912. Per cent. Dicyan- increase Total Cyanamid diatnide Urea in weight nitrogen nitrogen nitrogen nitrogen — 13.09 12.031 O.064 O.694 6.92 12.32 9563 1. 221 I.460 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 3 1 each day during the entire 21 weeks of exposure, a current of air was drawn through the desiccator. Weight of sample Original 10.609 g After 21 weeks- 11.343 g Same corrected to original weight — — 13-17 10.224 1.305 1.560 There is therefore no loss of nitrogen, but on the other hand an apparent slight gain, probably due, in the belief of the experimenter, to loss of moisture before the weighing of the sample for analysis. The total increase in weight is 6.92 per cent., which is about the same as the increase in the factory test at Jacksonville, Florida, described on p. 24. The amount of derivatives formed in the latter case was probably, therefore, about the same as in the laboratory test by Henschel. The amount of dicyandiamide formed is about 10 per cent, of the total nitrogen, and the urea is about the same. The agricultural significance of these changes will be dis- cussed in a later chapter of this volume. The above are a few of the many records at the command of the author, all of which agree in showing that when the increase in weight is allowed for there is no loss of nitrogen in Cyanamid under the ordinary conditions of storage of fer- tilizer materials. CHAPTER V. Decomposition of Cyanamid in the Soil. FACTORS INVOLVED. When Cyanamid is applied to the soil as a fertilizer it must undergo decomposition before the nitrogen can be assimilated by plants. The course of this decomposition, however, has been in dispute since the adoption of Cyanamid in agriculture, and a great deal has been written on the subject. Owing to the incompleteness of many of the reports, and the omission of essential data, no attempt will be made here to review all of them. Of the recent work on the subject the most con- sistent seems to be that of .C. Ulpiani and H. Kappen. Experiments of Ulpiani. — In 1908 Ulpiani reported the results of some experiments 1 that indicate the difficulties sur- rounding the solution of this important question. The results of these tests are summarized in the table on page 33. Aqueous solutions were used containing 0.5 per cent, pure cyanamide, together with various added materials as noted. Calcium was added in the form of calcium hydroxide, two equivalents to one of cyanamide. By "secondary products" is meant dicyandiamide, urea, and traces of amidodicyanic acid and ammonia, amounting to 33 per cent, of the total nitrogen present. Soil was added where shown in the table, in the proportion of 10 grams to 100 cc. of solution. The "nutritive substance for bacteria" consisted of 0.05 per cent, potassium phosphate, 0.01 per cent, asparagine and 0.01 per cent, glucose. Bacteria were introduced into flasks 3 to 8 by extracting soil with the water to be used to make the cyana- mide solution. No bacteria were present in flasks 1 and 2. 0.4 per cent, chloroform was present in flasks 7 and 8. Deter- minations for cyanamide nitrogen in the solutions were made at frequent intervals. The percentages of cyanamide decom- posed in 4 and 8 weeks respectively are shown in the table : 1 Gaz. Chim. Ital., 1908, II, No. 4, 358-417. CYANAMID — MANUFACTURE, CHEMISTRY AND USES 33 Flask Calcium Secondary products Soil Nutritive for substance bacteria Per cent, of cyanamide decomposed Chloroform 4 wks. 8 wks. I. Absent Present Absent Absent Absent 0.63 0.81 2. Present " i< " " 53-25 73.02 3- Absent " Present Present " 50.50 83-03 4- Present " " " " 83.00 100.00 5- Absent Absent " " " 6.84 16.72 6. Present " " " •' 40.62 — 7- Absent " " " Present 7.58 15-52 8. Present " Absent " " 41.04 — Flasks 1 and 2 were not inoculated with bacteria. Flask 1 therefore shows that a solution of cyanamide, in the presence of its derivatives, is not decomposed even upon months of standing. The mere addition of lime in sterile conditions causes a rapid decomposition of cyanamide. The effect of lime is shown throughout by comparing the even-numbered flasks with the odd-numbered flasks. Flask 7 shows that under sterile conditions, in the absence of lime, a small amount of soil causes a small amount of decomposition. Flask 5, which differs from flask 7 only in the fact that the sterilizing agent, chloroform, was omitted, shows that the presence of bacteria had no effect whatever upon the decomposition. The same thing is shown by com- paring flasks 6 and 8, in which lime was present. The larger values obtained in flasks 2, 3 and 4 seem to be related in some way to the presence of secondary products, that is, dicyandiamide, urea, and possibly amidodicyanic acid and ammonia. Flasks 1 and 2 were both uninoculated, hence the larger decomposition of flask 2 as compared with flasks 6 and 8 must be due to the simultaneous action of calcium and secondary products of cyanamide. A separate experi- ment showed, in fact, that the presence of 0.085 P er cent, ammonia in a solution of pure cyanamide containing 0.43 per cent, cyanamide effected the complete removal of the cyanamide in 3 months at 30 C, while the cyanamide without an ammonia addition remained constant. It is interesting to compare flask 1 with flask 3. These differ in two respects, presence of soil and presence of nutri- 34 CYANAMID — MANUFACTURE, CHEMISTRY AND USES tive substance. Now soil in the presence of secondary products may be expected to act similarly to soil in the absence of secondary products, that is, the soil should determine in flask 3 about 7 per cent, of decomposition more than occurred in flask i. The presence of nutritive substance is therefore probably in this case the controlling factor, but not nutritive substance alone, but nutritive substance in combination with soil and cyanamide derivatives. It is quite possible that a bacterial decomposition that does not take place in the pres- ence of cyanamide alone may take place if other nitrogenous substances are present which are capable of being attacked by bacteria. In fact, Ulpiani determined by separate experi- ments that the soil bacteria employed by him were not able to decompose pure cyanamide, but that they grew very readily in impure dicyandiamide solutions, while the experiments of Kappen show that micro-organisms do take part in the decom- position in the presence of nutrient solutions and, with the exception of special fungi, in non-sterilized soil. The effect of micro-organisms and of glucose used as a nutritive sub- stance is shown by the following experiment of Kappen. 1 One hundred grams of a sand soil of low activity was treated with 50 cc. cyanamide solution containing 33 mg. of cyanamide nitrogen. The same treatment was given another 100 grams, but glucose was added. In another case no glucose was added, but the soil was inoculated with cyanamide-splitting clado- sporium, a special fungus, occurring in some soils. The sub- sequent content of cyanamide nitrogen is shown in the fol- lowing table: Without Cyanamide glucose nitrogen in With Without with milligrams glucose glucose cladosporium Applied 33-°° 33-°° 33-°o Analysed immediately 3 x -75 3 2 -°4 3 2 -48 After 1 day 25.87 23.70 — After 2 days 23.52 21.16 4.70 After 3 days 19-69 *7-93 0.00 After 7 days 8.33 12.55 After 9 days 0.00 10.29 1 Zentr. fur Kunstdiinger Ind. XVII, 251, 1912. CYANAMID — MANUFACTURE, CHEMISTRY AND USES 35 It will be noticed that on the third day the amount of cyanamide that had been decomposed was about the same whether glucose were present or not, in fact there seems to be slightly more decomposition when the glucose was omitted, though this is probably accidental. At the end of 9 days, however, the glucose treated sample was entirely decomposed, while the untreated sample still contained about one-third of the original cyanamide. Cladosporium in the presence of soil caused a rapid decomposition, complete in 3 days. It is at once evident that the sand soil used did not contain appre- ciable amounts of cladosporium, or the decomposition would have been more rapid in the first two cases. During the first three days the samples with and without glucose behaved very much alike, hence the same processes were taking place, and these were probably chemical ; then, however, the glucose treated sample became suddenly very active, and this prob- ably represents the beginning of bacterial participation. It should be noted in the above experiment that the concen- tration of cyanamide applied was 0.022 per cent., as compared with the 0.5 per cent, used by Ulpiani. It is likely that the latter concentration is too great to permit bacterial activity, except under the most favorable circumstances and then only with certain bacteria. The quantity of cyanamide applied by Kappen is equivalent to about 600 pounds of nitrogen per acre half-foot of soil. In agriculture, 60 pounds per acre is a maximum that is seldom exceeded. Kappen succeeded in isolating pure cultures of five fungi capable of decomposing cyanamide ; two of them, penicillum brevicaule, and the cladosporium mentioned above, grew even in 2 per cent, solutions, but the others required lower concen- trations. It is therefore difficult to estimate the importance of these special fungi to this problem. It is certain that they do not occur commonly in all soils (those used by Ulpiani for instance and the ordinary soils of Kappen) to any great extent, and it is doubtful if they ordinarily have much to do with Cyanamid decomposition in the soil. 36 CYANAMID MANUFACTURE, CHEMISTRY AND USES Ulpiani explains their action as follows : The fungi may- decompose the glucose, when it is present, with the produc- tion of various aldehydic substances, which, according to well- known chemical reactions unite with the cyanamide with for- mation of compounds of the type R.CH : N.CN. It is also possible that the fungi produce various products of metabolism which are able to react with cyanamide and so neutralize it, probably in the manner of the formation of antitoxins. He cites in support of this theory the well-known ability of penicillum brevicaule to grow in the presence of arsenical substances. 1 The above experiments are in agreement with many others by Kappen, as well as with the experiments of Ashby, 2 Behrens, 3 Stutzer and Reis 4 and others, which show that bac- teria are active in some stage of the process. From these experiments of Ulpiani, Kappen and others, the following facts are evident: 1. A solution of pure cyanamide in the absence of other substances is quite stable, and is not decomposed by ordinary soil bacteria. 2. A solution of pure cyanamide may be decomposed by certain special fungi. 3. A solution of cyanamide in sterile conditions is decomposed by lime, by ammonia, and by soil. 4. A solution of cyanamide is decomposed by soil more rapidly in non-sterile conditions than in sterile conditions, provided the concentration is not too great. The course of the decomposition of cyanamide solutions by lime is very complex (see also p. 28) and leads to the formation of a mixture of urea, dicyandiamide, amidodicyanic acid, ammeline, melammine and other complex derivatives. On the other hand, the decomposition of cyanamide by soil is a simple hydrolysis in accordance with the equation : 1 B. Gosio, Studio sulla Bioreazione dell 'arsenico tellurio e selenio. Roma, Tip, Mantellate, 1907. 2 Zent. Bakt. XX, 704, (1908) ; XX, 281, (1908). s Jahrs. f. Agrik. 121, (1905). 4 Jour. f. Landw. Vol. 58, 65, (1910). CYANAMID — MANUFACTURE, CHEMISTRY AND USES 2>7 /NH 2 CN. NH 2 + H 2 O = OC< X NH 2 The formation of urea is practically quantitative, and is determined ordinarily solely by physico-chemical means, with- out the participation of organisms. It will be shown later that the transformation of the urea to ammonia is probably effected by bacteria. FIRST STAGE OF DECOMPOSITION. The form in which the nitrogen exists in Commercial Cyanamid, neglecting for the moment the alterations produced in storage, is calcium cyanamide. It has been known for many years that this salt is not stable in aqueous solution but immediately hydrolyzes to acid calcium cyanamide and calcium hydroxide : 2CN. NCa + H 3 = (CN. NH),Ca + Ca (OH), Moreover, all investigators agree that the acid calcium cyanamide has but an ephemeral existence in the soil ; when applied in normal fertilizer doses the calcium quickly abandons the cyanamide. Lohnis attributes this action to the effect of carbon dioxide in the soil solution, precipitating the calcium as carbonate and setting free the cyanamide : (CN.NH) 2 Ca + C0 2 = zCN.NH, + CaCO, Kappen considers the removal of calcium as a physical process of absorption in the soil, with simultaneous hydrolysis to free cyanamide : (CN.NH) 2 Ca + 2H 2 = 2CN. NH, + Ca(OH) 2 . He found, for instance, that when 200 grams of clay soil was shaken with 250 cc. of a solution of lime-nitrogen containing 47.8 mg. calcium and 62.2 mg. nitrogen, 39 per cent, of the calcium and only 5 per cent, of the nitrogen was absorbed by 38 CYANAMID — MANUFACTURE, CHEMISTRY AND USES the soil in one hour. Such a fertilization, however, amounts to 560 pounds nitrogen per acre half-foot of soil, a quantity far in excess of any ever used in agriculture. The quantity of calcium absorbed in one hour in this test is equivalent to 600 pounds CaO per acre half-foot of soil. Ulpiani regards the change as taking place with the inter- mediate formation of calcium cyanamide carbonate : (CN. NH) 2 Ca + C0 2 = CN. NH 2 + CaCN 2 C0 2 , CaCN 2 C0 2 + H 2 = CN. NH 2 + CaCO :) Whatever the mechanism of this hydrolysis there is no question but that the result is free cyanamide, and conse- quently the following investigations on the decomposition of cyanamide in the soil were made with the free cyanamide, CN.NH,. SECOND AND THIRD STAGES OF DECOMPOSITION. The following experiment by Ulpiani 1 was made to deter- mine the rate of decomposition of cyanamide: 100 grams of earth carefully dried at laboratory temperature, and sieved through a screen with holes of 1 mm. diameter, was placed in a glass tube and to it was added 20 cc. of a solution of pure cyanamide containing 4.2 per cent, cyanamide. The liquid reached almost to the bottom of the tube, hence the soil was not quite saturated. A series of tubes so prepared was stop- pered with cork and set in a thermostat at 28 C. After various periods of time the content of cyanamide remaining in the tubes was determined as follows : 80 cc. of distilled water was added and thoroughly stirred with the contents of the tube. After exactly an hour the contents were filtered with suction. Of the filtrate (about 70 cc), two portions of 25 cc. each were analyzed for cyanamide. The following results were obtained : 1 Gaz. Chim. Ital. XL, Parte 1, 1910. CYANAMID MANUFACTURE, CHEMISTRY AND USES 39 Quantity of eyanamide Milligrams Initial 84.0 After % hour 79.2 After 6 hours 75.8 After 1 day 65.9 After 3 days 52.5 After 5 days 40.9 After 7 days 29.8 After 9 days 22.6 After 11 days 18.4 After 15 days 10. o After 18 days 00.0 The values obtained are plotted in Fig. 2. It is seen that the removal of eyanamide from the soil solution is a maximum "? — 5 7 1 ?. Days after appl/cat/on RATE OF REMOVAL OF CYANAMIDE FROM SOIL SOLUTION. Fig. 2. in the first few moments of contact. This probably corre- sponds to an initial period of absorption. It is evident, how- 4 4-0 CYANAMID — MANUFACTURE, CHEMISTRY AND USES ever, that the cyanamide is not removed solely by a process of absorption, since it is characteristic of absorption processes that a state of equilibrium is usually reached between the sub- stance in solution and in the absorbing surfaces within a day. The substance that is being absorbed never disappears entirely from the solution. In the present experiment, the reaction proceeds to complete disappearance of the cyanamide. The rate of removal of cyanamide is practically constant after the first 9 days, and shows no tendency to become zero thereafter, as it would if an equilibrium were being approached. Such rapid removal of the cyanamide to the very end of the experi- ment can be due only to chemical conversion of the cyanamide to other forms. INFLUENCE OF CONCENTRATION. The following experiment was made by Ulpiani to deter- mine the effect of varying the concentration of cyanamide. In each of a series of glass tubes was placed ioo grams of soil, which was covered with 25 cc. of a solution of cyanamide at various concentrations. At the end of 3 days and at the end of 10 and 30 days, certain tubes, as shown in the table, were taken out, thoroughly mixed with 75 cc. water and after standing one hour were filtered with suction, and cyanamide was determined. The following results were obtained : Initial quantity of cyanamide -, Final quantity of cyanamide After After After 3 days 10 days 30 days Absolute quantity converted in 3 days Mg. Concen- tration Per cent. Mg. in 25 cc. Percentage converted in 3 days I 25.O trace — — 25.O IOO 2 50.O 25-1 — — 24.2 49 3 75-o 43-5 — — 31-4 42 4 100.0 60.0 — — 40.0 40 5 125.0 84.0 — — 41.0 33 6 150.0 103.4 — — 46.5 31 9 225.0 I7I-3 110.8 13-4 53-7 24 12 300.0 231.8 156.8 40.3 68.2 23 15 375-o 302.4 209.1 60.5 72.6 19 18 450.0 352.8 245-2 67.2 97.2 21 21 525-° 420.0 289.8 71.4 105.0 20 CYANAMID — MANUFACTURE, CHEMISTRY AND USES 41 In Fig. 3 is plotted the percentage of the cyanamide removed with increase of concentration. This percentage is a maximum at the lower concentrations, but decreases as the concentration increases, until finally a steady value of about 20 per cent, is reached, when the amount of cyanamide disappearing in a given time is constant. The fact that this curve is approxi- mately logarithmic indicates that the primary action is one of absorption, since it is well-known that the more dilute the solu- tion the greater is the percentage of substance taken up by the absorbing surfaces, and that as the concentration of solution EFFECT OF CONCENTRATION ON REMOVAL OF CYANAMIDE FROM SOIL SOLUTION. j 0.2 0.3 0.4 05 Fig. 3- increases a condition of equilibrium is reached and the ratio of the concentrations in the absorbing surfaces and in the solution becomes constant. Fig. 4 shows the absolute quantity of cyanamide removed as the concentration increases. It is practically directly propor- tionally to the concentration. This curve shows the same fact as the curve in Fig. 4, namely, that the ratio of the con- centrations in the absorbing surfaces and in the solution is 42 CYANAMID — MANUFACTURE, CHEMISTRY AND USES a constant, a fact highly characteristic of absorption pro- cesses. In this experiment also, the cyanamide finally disappears entirely from the solution in the course of time, and hence, chemical conversion occurs along with the absorption phenomena. Taking all the above facts together, it is easy to under- stand that in the initial period of contact between the cyanamide solution and the soil there is a withdrawal of cyanamide mole- cules from the solution, and a concentration of molecules in Grams Cyanam/e/e app/tea per lOO grams So//. Fig- 4- the limiting stratum between the solution and the surface of the solid soil particles. Along with and subsequent to this absorption process there is a chemical conversion of cyanamide molecules, by catalytic action of soil colloids, as we shall show later, the products of the reaction being removed continually and being replaced by new molecules of cyanamide in the limit- ing stratum. CYANAMID — MANUFACTURE, CHEMISTRY AND USES 43 That bacteria could take no part in the present experiment is evident, since micro-organisms cannot live in the very con- centrated solutions employed. INFLUENCE OF TEMPERATURE. Experiments carried out in a similar manner with 100 grams of soil and 20 cc. of solution containing 4.2 per cent, cyanamide at various temperatures gave the following results : At o° At 12° At 30 Initial quantity of cyananiide- • • . 84 tug. 84 nig. 84 mg Quantity present after 2 days. • . 77 69 5i " 4 " ••• • 73 59 23 " 6 " ... . 69 44 18 " 11 " ... - 53 33 trace The velocity of the reaction increases with the temperature, but even at o°, where micro-organic life is practically at a standstill, there is a conversion of about 3.5 mg. of cyanamide per 120 grams of damp soil per day. INFLUENCE OF SOIL AT 100° C. Two flasks, one containing ioo cc. of a solution with 21 per cent, cyanamide, the other 100 cc. of 21 per cent, cyanamide solution and 500 grams of soil, were heated in a Koch's oven at ioo° C. for six hours. After cooling, 400 cc. of water was added to each, and after agitation and filtering, analyses were made. In the flask without soil there was still a large quantity of cyanamide present and considerable dicyandiamide. In the flask with soil, however, there was no cyanamide or dicyandia- mide remaining after the treatment, but abundant quantities of urea. Under these conditions it is probable that the conver- sion to urea is quantitative. The reaction must be one of hydrolysis in accordance with the equation. ,NH„ CN. NH 2 + H.,0 — OC \ NH, 44 CYANAMID — MANUFACTURE, CHEMISTRY AND USES NATURE OF PRODUCTS FORMED IN SOIL AT ORDINARY TEMPERATURES. The formation of dicyandiamide is always accelerated by the action of heat, whether in solutions of cyanamide, or in solu- tions of cyanamide treated with lime, ammonia or other weak bases. Since there is no formation of dicyandiamide when cyanamide is heated with soil, as shown in the experiment on page 43, there will evidently be none formed at ordinary tem- peratures. This is verified in the following two experiments. Four kg. of soil in a balloon flask was sterilized on three successive days by heating for an hour each day in an auto- clave at ioo° ; then was introduced into the flask 800 cc. of a solution containing 4.2 per cent, cyanamide. The flask was stoppered and kept in a thermostat at 25 for 18 days. After agitation with 3,200 cc. water for an hour, and filtering with suction, total nitrogen and cyanamide nitrogen were deter- mined. The results were as follows : Grams Initial nitrogen 2.492 Nitrogen absorbed in soil 1.154 Nitrogen in solution as cyanamide 0.671 " " not cyanamide 0.667 " " as dicyandiamide none After the removal of the cyanamide, and concentration on the water bath, addition of nitric acid produced an abundant pre- cipitate of nitrate of urea, which on recrystallization showed a melting point of 140 . This experiment shows that under sterile conditions the product of cyanamide conversion is prob- ably entirely urea. Under natural conditions, there is little doubt but that the urea is rapidly converted in the soil into ammonium com- pounds. It was desirable therefore to learn how closely the action of cyanamide resembled that of ammonium carbonate in the soil. In a balloon flask containing 11 kg. of soil was added 200 cc. of solution containing 4.2 per cent, pure cyana- mide ; and in another flask with 1 1 kg. of soil was added 200 cc. of solution containing 9.6 per cent, ammonium carbonate, CYANAMID — MANUFACTURE, CHEMISTRY AND USES 45 equivalent to the amount of cyanamide used. Each flask was equipped with connections permitting a current of air to pass through the flask, and then through a bottle of dilute sulphuric acid to catch any ammonia evolved in the flask. The balloon flasks were held in a thermostat at 25 ° for 22 days, at the end of which time 800 cc. water was added. After shaking and standing an hour and filtering with suction, tests showed that there was no cyanamide or dicyandiamide present in the flask to which cyanamide had been added. Determinations were made for total nitrogen, ammoniacal nitrogen and nitric nitro- gen in the solution. The following values were obtained : Soil plus Soil plus ammonium cvanamide carbonate nig. mg. Iuitial nitrogen 560 560 Final nitrogen absorbed by soil. 450 420 Final nitrogen remaining in solution : Ammoniacal 60 70 Nitrate 9 70 Cyanamide o — Dicyandiamide o Undetermined 41 o The sulphuric acid in the bottles, through which bubbled the air leaving the flasks, was unchanged, hence, no ammonia escaped from the soil. Since the 41 mg. of undetermined nitrogen in the solution from the cyanamide flask was not cyanamide, dicyandiamide, ammonia or nitrate nitrogen, it must have been urea, in accord- ance with the previous experiment. The conversion of the urea to ammonium salts was therefore not quite complete. The conversion of ammonium salts to nitrates was also less than the conversion in the case of ammonium carbonate. The amount of ammoniacal nitrogen in solution is practically equal in the two flasks. It is evident, therefore, that in both cases the absorbed nitrogen exists in the soil in the state of am- monium salts, and these are in equilibrium with the ammonium salts in the solution. Since the soil was not sterilized and low 46 CYANAMID — MANUFACTURE, CHEMISTRY AND USES concentrations of cyanamide were used, and large quantities of ammonia were formed, it is very likely that bacteria partici- pated in the decomposition by reacting upon the urea and determining its hydrolysis to ammonium salts. EFFECT OF CHANGING RATIO OF LIQUID TO SOIL. When 100 grams of air-dried earth was covered with 20 cc. of cyanamide solution practically all of the soil was wetted, only a little at the bottom of the tube remaining dry. In this condition the mass of water may be considered as being at its maximum distension, each solid particle of the soil being sur- rounded by a thin film of liquid. This liquid film on the in- side, is in contact with a solid phase, and on the outer surface with a gaseous phase, since the interstices of the soil were not filled with liquid. When 100 grams of soil was covered with 50 cc. of cyanamide solution the interstitial spaces were filled with liquid. There was therefore practically no gaseous phase present. One hundred grams of soil covered with 100 cc. of cyanamide solution was completely submerged. Series III in the table was thoroughly shaken twice a day during the test. Series IV was not disturbed in any way. The results obtained were as follows : Series I Series II Series IV 20 cc. not shaken 50 cc. not shaken Series III 100 cc. shaken 100 cc. not shaken nig. nig. mg. rag. Initial quantity Cyanauiid • 84.O 84.O 84.O 84.O Quantity after 1 day • 65.9 68.O 71.9 73-° (i " 5 days • 40.9 53-7 58.1 60.0 n " 9 days . 22.6 47-8 54-6 57-i " " 15 days • IO. O 34-8 46.2 49-5 n " 21 days • OO.O 26.7 35-7 44.1 1 1 " 31 days . O.O 11. 7 35-2 36.9 " " 41 days • O.O 8.4 18.6 33-6 Here again we must exclude bacterial participation, since if bacteria were present they should grow better in the dilute solutions than in the solution of 4.2 per cent, cyanamide in CYANAMID — MANUFACTURE, CHEMISTRY AND USES 47 Series I, yet in the dilute solutions the transformation is very slow. The above experiment shows that the cyanamicle does not react with other soluble substances of the soil, for in such case the maximum activity should occur in dilute solutions ; but its conversion is at a maximum when the greatest amount of cyanamide is enabled to come in contact with the solid sur- faces of the soil particles. This condition is obtained when for a given quantity of cyanamide the amount of liquid is a minimum, for then the liquid film about the solid soil particles is its thinnest, the cyanamide is closest to the soil, and the forces of surface tension are at their maximum. INFLUENCE OF AERATION. In order to determine whether oxidation plays any part in the phenomena, an apparatus was arranged so that a current of air in one case and a current of hydrogen in another could be conducted over the samples of soil treated as before with 4.2 per cent, cyanamide solution. The treatment lasted for six days, a portion of the sample being withdrawn in three days. The following: results were obtained : Quantity cyanamide present Initial r- — ' > Per cent. quantity after after Cyanamide converted in cyanamide 3 days 6 days , " > Mg. Mg. Mg. 3 days 6 days Air 168.0 no.o 22.0 34.0 86.0 Hydrogen.. 168.0 114.0 46.0 32.0 72.0 There is practically no difference in the amounts of conver- sion in 3 days, and not a great deal of difference between the amounts of conversion in 6 days. The results do not differ enough so that it can be said that oxidation plays any appreci- able part in the change. The fact, therefore, that in all of the preceding experiments the tubes were stoppered with cork and sealed with paraffin to prevent evaporation of water could not at any rate increase the conversion. 48 CYANAMII>— MANUFACTURE, CHEMISTRY AND USES INFLUENCE OF ELECTROLYTES. To determine the effect of the presence of various reagents on the course of the conversion, an experiment was made with solutions of cyanamide in balloon flasks without addition of soil, but with various electrolytes. The concentration of cyanamide in the solution was 0.554 per cent. ; the other reag- ents were in the proportion of two equivalents to one cyanamide. The following table shows the amounts of cyanamide remaining in solution. 554 mg. cyanamide plus After — Ca(OH) 2 KOH HN0 3 KN0 3 — weeks 554.0 557.0 556.0 451.0 558.0 3.3 weeks 554-° 413.0 420.0 254.0 422.0 8.3 weeks 554.0 369.0 382.0 — 369.0 13.3 weeks 554.0 331.0 340.0 — 303.0 28.3 weeks 554-Q 182.0 trace — trace The very slow course of the reactions as compared with the action of soil shows that it is probably not the soluble salts in the soil that are responsible for the hydrolysis of cyanamide but the solid soil particles. This confirms the conclusion drawn on page 42. NATURE OF EFFECTIVE SOIL CONSTITUENTS. In order to determine whether the conversion of cyanamide is caused by the gross solid particles of mineral matter in the soil, or whether it is due to colloids, or various organic debris, the following experiment was made. Soil was allowed to stand a week in contact with concentrated hydrochloric acid, and was then washed free of acid. A portion of soil so treated was saturated with sodium carbonate solution and then washed free of alkaline reaction. A fresh portion of soil was calcined by heating in a combustion furnace in a current of oxygen until carbon dioxide no longer escaped. These samples were treated with cyanamide solutions as in previous experiments, with the following results: CYANAMID — MANUFACTURE, CHEMISTRY AND USES 49 Final cyanamide Initial after after after cyanamide 3 days 6 days 9 days mg. mg. mg. mg. Ordinary soil 83.8 52.0 36.0 19.5 Soil treated with HC1 S3.8 63.5 49.1 36.0 Soil treated with H CI and Na 2 CO s .. 83.8 55.5 43.2 46.0 Soil calcined 83.8 77.6 Each of the above treatments has diminished the ability of the soil to convert cyanamide to other forms. The calcined soil has very little power of decomposition. It is evident, therefore, that it is not the gross, solid, mineral particles of the soil that have this power, but certain constituents of the soil mass that are destroyed by heat. These constituents belong to the class of chemical compounds that form colloids or disperse systems in the soil. We will now examine the results of experiments made with various materials that are known to form part of practically all soils. EFFECT OF ZEOLITES. According to Van Bemmelen 1 the colloids of agricultural soil consist principally of amorphous zeolites (amorphous hydrated silicates). These remain for an indeterminate time in suspension in pure water, are coagulated by electrolytes, can be dried into hard compact masses, have in the highest degree the properties of hydrogels, and to their presence is probably due the greater part of the absorptive powers of the soil. Since these substances could not be isolated in their natural state it was necessary to use certain crystallized zeolites, as follows : Natrolite of Bohemia, hydrated metasilicate of aluminium and sodium. Scolecite of Ireland, hydrated metasilicate of aluminium and calcium. 1 Landw. Ver. Staz. Bd. XXXV, (1888) p. 69. 50 CYANAMID — MANUFACTURE, CHEMISTRY AND USES Analcimite of Tyrol, hydrated trisilicate of aluminium and sodium. Cabasite of Nova Scotia, hydrated trisilicate of aluminium and calcium. Each zeolite was ground in a mortar and made to pass a screen of fineness Kahl. oo. One hundred grams of each zeolite was placed in glass tubes moistened with 20 cc. of a 4.2 per cent, solution of cyanamide (2.8 per cent, nitrogen). A fifth tube without zeolite was used as a control. After 12 days in a thermostat the solutions were analyzed with the following results : Cyanamide Initial after cyanamide 12 days grams grams Solution alone 0.0840 0.0836 " natrolite 0.0840 0.0235 " scolecite 0.0840 0.0148 " analcimo 0.0840 0.0158 ' ' cabasite 0.0840 0.0168 This experiment shows that the crystalline zeolites possess to a high degree the ability to transform the cyanamide, from which we may conclude that the colloidal zeolites as they exist in the soil must have a still greater ability. The crystalline zeolites, according to Zambonini, 1 have a structure analogous to that of the hydrosols, and according to Von Weimarn 2 may act like colloidal substances. EFFECT OF CARBON. Ulpiani next desired to learn what effect would be obtained with a material exposing a large surface, but of no chemical activity towards cyanamide. For this purpose a commercial animal carbon was washed with hydrochloric acid and then with water until free from acid, and was dried in an oven at no° C. In order to obtain a wetting comparable to that in the experiments with soil, 50 grams of carbon was moistened 1 Atti. R. Ace. Lincei, XVIII. fasc. II, 1st Sem, 1909. 2 Koll. Zeit. Vol. VI, No. 1, 1910. CYANAMID — MANUFACTURE, CHEMISTRY AND USES 5 I with 50 cc. of 4.2 per cent, cyanamide solution. The tubes were kept in a thermostat at 25 for different lengths of time. Just before the analysis 200 cc. of water was added, stirred for exactly one hour, filtered with suction, and cyanamide was determined in the filtrate. The results were as follows: Cvanamide present Total nitrogen in solution mg. Per cent. nig. Per cent. Beginning 210.0 100 140 100 After 1 hour 161. 7 77 112 80 " 6 hours 153.3 73 io 5 75 " 1 day 132.3 63 102 73 " 3 days 107.6 51 87 62 " 5 " 96.6 46 89 64 " 7 " 75-6 36 89 64 " 9 " 59-3 2S S3 59 " 15 " 8.4 4 64 46 " 22 " 0.0 o 77 55 On the 22nd day the solution was distilled with magnesia, giving up 66 per cent, of its nitrogen as ammonia. Hence, of the 55 per cent, remaining in the solution on the 22nd day 22 per cent, was ammoniacal and 33 per cent, ureic nitrogen. A test with nitric acid gave characteristic crystals of urea nitrate. The experiment was repeated, sterilizing both the carbon and the cyanamide solution. After 2 months the following results were obtained : Mg. Initial nitrogen 560 After 2 months, ammoniacal nitrogen 8 Cyanamide " o Dicyandiamide " o A test for urea showed the presence of abundant quantities. These experiments with carbon show that the decomposition of cyanamide is an hydrolysis which is greatly accelerated by the addition of catalysers of various kinds. EXPERIMENTS WITH NATURAL COLLOIDS. The experiments of H. Kappen 1 confirm in general the results obtained by Ulpiani. The following experiment of 1 Zentr. f. Kunstdtinger-Industrie, XVII, 234-236, 248-251, 1912. 52 CYANAMID MANUFACTURE, CHEMISTRY AND USES Kappen shows the relative decomposing ability of some well- known constituents of ordinary soils. These materials were selected so as to differ as widely as possible from one an- other, so that the effect of individual constituents might stand out. Each substance was used in its natural condition, with- out being sterilized, but ground to a fine powder. They are all in the class of compounds that form gels in the soil. i. Meadow iron ore from Guben, Niederlausitz; contain- ing considerable manganese. 2. Meadow iron ore from Otrotschin, Bohemia; contains no manganese. 3. Earth of Siena, yellow natural product containing iron oxide. 4. Umber, brown natural product containing iron and man- ganese oxides. 5. Laterite earth from Kamerun. 6. Manganese ore, principally manganese hydroxide. 7. Manganese dioxide. 8. Red Bauxite, aluminum hydroxide gel containing iron oxide. 9. White Bauxite, without iron oxide. 10. Kaolin from Meissen. 11. Sandy Kaolin from Tiirkismuhl. 12. Glass sand. Of the above minerals No's 1, 2, 3, 4, 6, 7, 8, 9 and 12 were used alone, while No.'s 5, 10 and n were mixed with an equal quantity of glass-sand. One hundred grams of each was placed in an Erlenmeyer flask and treated with 10 cc. of a 0.5 per cent, cyanamide solution, containing 33 mg. cyanamide- nitrogen. Immediately after the addition of cyanamide, and at the end of various periods of time the content of cyanamide- nitrogen was determined, with the following results: CYANAMID — MANUFACTURE, CHEMISTRY AND USES 53 Cyanamide nitrogen 1. Iron ore 2. Iron ore 3- Earth of Siena 4- Umber 5- L,aterite 6. Manganese hydroxide 33- 00 33-°° 33-oo 33-°o 33-Oo After y z hour- •- 22.96 33- is 33-51 31-75 34.02 8.00 " 1 day- - • O.OO 0.00 32.04 20.03 19.40 0.00 " 2 days - • .. — — 30.87 13-27 II. 17 — " 3 days • • — — 27.3S 5-92 — — " 6 days • - •• — 27.04 0.00 4-37 — " 7 days - - — — 26.57 — 2.82 — Cyanamide nitrogen 7- Manganese dioxide 8. Red bauxite 9- White bauxite 10. Kaolin 11. Sandy kaolin 12. Glass sand 33-oo 33-oo 33-00 33-00 33-oo After y z hour- •• 30-49 32.48 33-04 32.04 32.00 32.00 ' ' 1 day - - - •• II.76 29.40 32.04 32.04 26.16 32-34 " 2 days - - O.OO 27-34 30.86 31.16 21-75 32-34 ' ' 3 da g s • • — 25.28 30.57 30.57 — 32-34 " 6 days • • .. — 19.82 30.28 30.28 1352 32.34 " 7 days - - •• — 17.68 29.98 29.98 11.76 32.24 Of the greatest activity is manganese hydroxide; second, iron hydroxide containing manganese hydroxide ; and third, iron hydroxide free of manganese. The activity of the next most active materials can properly be ascribed to their con- tents of iron oxide. The difference in the activity of red and white bauxite is very likely due to the difference in iron con- tent. The greater activity of sandy kaolin as compared with kaolin is probably due to the presence in the former of zeolitic substances, which, as Ulpiani found, have a high activity. The low activity of the kaolin, considering the large specific surface it possesses, suggested that the properties of the vari- ous substances are not merely surface phenomena, but that their specific chemical nature is of importance. Manganese hydroxide and the two iron ores were mixed with glass sand in the proportion of 1 gram to 100 grams sand, and a sample of 0.1 gram manganese hydroxide with 100 grams glass sand. These mixtures moistened as before with cyanamide solution containing 33 mg. nitrogen, gave the following results, as com- pared with the kaolin of the preceding experiment : 54 CYANAMID — MANX JFACTURE, CHEMISTRY AND U SES Glass-sand plus Cyanamide nitrogen milligrams Kaolin 1 per cent, manganese hydroxide 1 per cent. 1 iron ore No. 1 per cent, iron ore No. 2 0.1 percent, manganese hydroxide • 33-oo 33- 00 33- 00 33- 00 33-°° ^.fter 15 hours. . • — 5.06 25-25 30.80 — " 2 days- • • • 31-16 0.00 14.78 26.48 30.18 " 3 " ••■ •• 30.57 — 8.62 22.79 28.33 " 6 " ... . 30.28 — 4.00 17.24 25-25 It has been shown in the preceding experiment that glass sand has practically no activity. Hence, 0.1 grams of man- ganese hydroxide is more effective than 100 grams of kaolin. The surface exposed by the kaolin is clearly much greater than that exposed by the smaller quantities of iron and manganese hydroxides, and the catalytic activity of the latter is therefore essentially connected with their chemical properties. Another experiment was made to compare the activity of iron hydroxide, aluminium hydroxide and silicic acid. The iron and aluminium hydroxides were prepared by precipita- tion ; a sample of each was mixed in the undried condition with 4 times its weight of glass sand, the mixture then containing 2.6 per cent, iron oxide in the one case and 1.6 per cent, alumina in the other. The aluminium hydroxide and the pre- cipitated silicic acid were dried and applied separately to twice their weight of glass sand. One hundred grams of each of the above mixtures was treated with 20 cc. of cyanamide solu- tion containing 33 mg. of cyanamide nitrogen. The sub- sequent analyses are as follows : Glass -sand plus Cyanamide nitrogen in milligrams Iron hydroxide undried 2.6 # Fe 2 3 Aluminium hydroxide undried 1.654 A1 2 3 Aluminium hydroxide Dried Silicic acid Dried 33-°° 33-oo 33- 00 33- 00 After y z hour • 3I-52 32.48 32.04 32.92 " 1 day • • O.OO 32.34 3I.I6 32.63 " 3 days .. — 29.56 29.69 31-94 " 6 days . . — — 25-87 31.08 Silicic acid has a slight ability to convert cyanamide; and aluminium hydroxide has somewhat more. CYANAMID — MANUFACTURE, CHEMISTRY AND USES 55 To determine the effect of varying quantities of iron hydroxide gel, the precipitated undried hydroxide was mixed with glass sand in different proportions, and treated as above with the following results : Cyanamide Glass-sand plus iron hydroxide gel containing nitrogen in , ■ ■ milligrams 2.6£ Fe 2 3 i.3# Fe ; 3 0.65 £ Fe : 3 0.26$ Fe 2 3 Applied 33.00 33.00 33.00 33.00 After 1 day 0.00 4.31 12.32 23.11 " 2 days — 0.00 3.69 13-55 " 3 " — — trace 9.85 " 4 " .... — — 0.00 8.00 " 5 " •••• 5-37 The amount of conversion, therefore, varies with the amount of iron oxide present. The same iron hydroxide gel was treated in different ways to see what effect would be obtained by changing the form of the material : Precipitated iron hydroxide Cyanamide Dried Heated in nitrogen in 5 hrs. at steam for Ignited milligrams Untreated io5°C 2^ hrs. for % hrs. Applied 33.00 33.00 33.00 33.00 After y 2 day — 4.31 12.32 — After 1 day 0.00 0.00 6.46 14-47 " 2 days — — 1.57 6.16 " 3 " — — 0.00 4.00 " 4 " — — 1-84 " 5 " — °-°° The untreated iron hydroxide has the most activity, which is decreased somewhat by steaming and greatly decreased by ignition. To determine the effect of iron oxide in the condition of a hydrosol, 250 cc. of iron oxide sol containing 0.8 per cent, iron oxide was treated with 1.25 grams cyanamide. The solution remained clear and fluid during the course of the experiment. For the determination of cyanamide, 10 cc. of the clear solu- tion was pipetted off, flocculated with ammonium nitrate and after dilution and filtration, treated in the usual manner. The following results were obtained : 5 56 CYANAMID — MANUFACTURE, CHEMISTRY AND USES Cyanamide nitrogen in Iron oxide sol. milligrams (0.8 per cent. Fe 2 O3) Applied 33.04 After 18 hours 27.77 " 2 days 22.40 " 4 days 10.08 The condition of sol is favorable to the conversion, but not as favorable as the condition of gel since the dilution of the cyanamide hinders the reaction. In order to determine whether or not calcium cyanamide reacts as readily as cyanamide, a quantity of lime-nitrogen con- taining 33 mg. of cyanamide nitrogen was added to ioo g of a mixture of sand with equal weights of manganese hydroxide, and iron ores No. I and 2, (see page 52). After 24 hours the quantities of cyanamide nitrogen remaining were : Milligram Manganese 0.00 Iron ores No. 1 and No. 2 0.00 Glass-sand 29. 18 With cyanamide, glass-sand left 32.34 mg. in solution after 1 day. The presence of the lime in the lime-nitrogen evidently hastens the decomposition of the cyanamide. The effect of pure, calcined iron oxide, Fe 2 3 , on cyanamide was determined by mixing glass sand with 5 per cent, of its weight of iron oxide, and treating with cyanamide solution as in the previous experiments. Milligram Cyanamide applied 33-oo " after 1 day 32.42 " 3 days 30.63 " 5 days 28.07 " " 8 days 26.56 Iron oxide therefore has a slow action as compared with the metal hydroxides used. EXPERIMENT WITH STERILIZED SOIL. All of the above experiments of Kappen were made with unsterilized materials; they therefore do not differentiate between physico-chemical and bacterial processes. In this CYANAMID — MANUFACTURE, CHEMISTRY AND USES 57 experiment, soil was sterilized by being held several days in an atmosphere of chloroform vapor, and was compared with untreated soil as in the previous experiments, with the follow- ing results : With chloroform Without chloroform mg. nig. Cyanamide nitrogen applied 33-°° 33-°° Cyanamide nitrogen after 2 days • • • 23.00 0.00 The addition of chloroform to the soil therefore greatly hin- ders the decomposition of the cyanamide, but does not prevent it. It is quite probable that in all of the experiments made by Kappen, except those where high temperatures were employed, bacteria participated in the decomposition of the cyanamide by converting the urea into ammonium salts, thus hastening the hydrolysis of the cyanamide. CONCLUSIONS. From the above experiments on the conversion of cyanamide the following conclusions can be drawn : I. Calcium cyanamide in contact with moist soil undergoes a decomposition to the form of ammonium salts in three inde- pendent stages. The first stage is a complete hydrolytic sepa- ration of the calcium from the cyanamide, induced by the selective absorption of calcium by the soil, and its probable precipitation as calcium carbonate. (Seep. 37). The second stage is a hydrolysis of cyanamide entirely to urea; the third stage is a transformation of urea to ammonium salts. II. The cyanamide disappears from the soil solution by two processes : (a) Absorption and concentration of cyanamide molecules in the limiting stratum between the soil solution and the soil particles. This takes place during the first few moments of contact. (See pp. 37 and 38). (b) Removal of the cyanamide molecules from the limiting stratum by hydrolysis to urea under conditions of high surface pressure and concentration. (See p. 40). III. The greatest velocity of hydrolysis occurs when the 58 CYANAMID MANUFACTURE, CHEMISTRY AND USES ratio of soil solution to soil is the least; that is, when the liquid film about the soil particles reaches its maximum dis- tension, and the cyanamide molecules are in closest contact with the soil particles (See p. 42). IV. The hydrolysis to urea is brought about in the soil by the catalytic action of certain colloidal substances, of which the most effective are the hydroxides of manganese and iron, and certain natural zeolites (hydrated meta- and tri-silicates of aluminium and sodium or calcium (pp. 48-56). Other colloids occurring naturally in the soil have less ability of transformation. Animal carbon is about as active as soil (P- 51). V. The soil loses its power of effecting the transformation when it is calcined or when it is treated with acids and alkalies ; that is, when the colloids are destroyed. Upon addition of the colloids again, it reacquires the property of transformation. VI. The conversion of cyanamide in sterile conditions is entirely to the form of urea. The urea was isolated and iden- tified (pp. 43, 44, 50- VII. In the hydrolysis of cyanamide to urea, micro-organ- isms do not participate, because : (a) The transformation proceeds most rapidly at high con- centrations of cyanamide and at concentrations far above those that support life (pp. 40, 43, and 46). (b) The transformation takes place with greatly increased velocity at ioo° C. (p. 43). (c) The transformation takes place in the presence of anti- septics and sterilized materials (pp. 44, 50, and 56). VIII. Unless the greatest care is taken to have perfectly sterile conditions, the urea is converted into the form of ammonium salts. In ordinary soil this change is very rapid (pp. 40, 44, and 57). IX. The conversion of the urea to ammonium salts hastens the hydrolysis of cyanamide to urea by removing the end- product of the hydrolysis (p. 57). CYANAMID — MANUFACTURE, CHEMISTRY AND USES 59 X. While cyanamide itself is not directly utilized by ordi- nary bacteria, this fact is of relatively little importance, since the soil bacteria grow in the presence of cyanamide if urea or some other nutrient substance is present ; the urea being formed by physico-chemical means from the cyanamide. (See pp. 34, 36, 44,45. and 57). XL The retention by the soil of the nitrogen formed from cyanamide is under the form of ammonium salts (p. 45). CHAPTER VI. Retention of Cyanamid Nitrogen in Soil. The absorption and retention of Cyanamid nitrogen by vari- ous soil constituents has been investigated by only a few workers, and very little has been reported that can be regarded as of practical interest. Such tests to be of value should be made with natural soils, and not with pure constituents, such as ignited glass-sand, as has been done by some investigators. The period permitted for absorption should be at least one or two days, and the proportion of aqueous solvent should not exceed that likely to occur in agricultural practice, nor should larger quantities of nitrogen be applied than are likely to be used by the farmer. The retention of nitrogen is doubtless due to physical pro- cesses, as well as to chemical reaction with both the mineral and organic constituents of the soil. (See pp. 39 and 45). Physically, Cyanamid nitrogen is retained in the soil by pro- cesses of absorption in the same way as sodium nitrate, or other salts which do not form insoluble compounds by chem- ical reaction with the soil. By chemical and biological pro- cesses, however, Cyanamid nitrogen is quickly converted to the form of ammonium salts, and these are retained in the soil in the form of humic and zeolitic compounds of ammo- nium. According to, A. D. Hall, the weaker the solutions of ammonium salts applied the greater is the percentage of ammonium absorbed by the soil. 1 In the field the amount of soil is so enormously in excess that the absorption of ammo- nium salts is practically complete. While plants undoubtedly have the power of directly assimi- lating the urea 2 that is formed as a transition product during the conversion from cyanamide to ammonium salts, the dura- tion of the urea stage is probably very short in the soil, and 1 A. D. Hall, The Soil, New York, 1910, p. 215. 2 Jour. Agr. Sci., Vol. IV, Part 3, p. 282. CYANAMID — MANUFACTURE, CHEMISTRY AND USES 6l the practical consequences of its brief existence are probably very slight. Hutchinson and Miller have shown that ammo- nium salts, also, are directly assimilated by plants, 1 but just how effective such processes are it is difficult to estimate. Practically there can be no doubt but that most of the ammonium salts are converted to nitrates prior to their absorp- tion by the plant. 1 Jour. Agr. Sci., Vol. IV, Part 3, p. 2S2. CHAPTER VII. Nitrification of Cyanamid Nitrogen. While some of the fertilizing effect of Cyanamid may be due to the presence of urea and ammonium salts, nitrification of cyanamide and its decomposition products may take place very readily in the soil under favorable conditions, providing the concentration of nitrogen is not too great. This is shown in an experiment by Wagner, which was carried out as follows : a Two hundred and fifty grams of sandy-loam soil was mixed with 5 grams of marl and the quantity of nitrogen salts shown in the table below. Each salt was well mixed with 2 grams of gypsum before application in order to facilitate distribution. The mixtures were placed in cylindrical glass vessels 6 l /> cm. in diameter and 17 cm. high, moistened with 75 cc. water, and covered with 50 grams unfertilized earth. The vessels were allowed to stand at room temperature and the evaporated water was replaced from time to time. After 12, 20, and 33 days respectively samples were drawn from each series and analyzed for nitrate nitrogen. After subtracting the figures obtained in the unfertilized control vessels the following results were obtained: With the sodium nitrate Nitrate nitrogen as NO at ioo, the other fertilizers (ccm.) gave as nitrate nitrogen After After After After After After Fertilizer 12 20 33 12 20 33 application days days days days days days 0.05 grams nitrogen as sodium nitrate 23.7 23.9 24.7 100 100 100 0.05 grams nitrogen as sulphate of am- monia 20.8 22.5 — 88 94 — 0.0125 grams nitrogen as Cyanamid 3.9 5.9 5-9 66 99 9^ 0.025 grams nitrogen as Cyanamid 4.1 9.9 II. 2 35 83 91 0.05 grams nitrogen as Cyanamid 0.3 6.3 14.9 1 26 60 1 Landw. Vers. Stat. Vol. 66, No. 4 and 5, 1907. CYANAMID — MANUFACTURE, CHEMISTRY AND USES 63 0.0125 grams nitrogen per 250 grams of soil is equivalent to a fertilization of about 90 pounds of nitrogen per acre. With this large application, even, nitrification of the Cyanamid is complete in twenty days. Larger applications require a longer period, but are of no practical interest. The above results must be considered relatively to each other and not as absolute values, since the conditions were probably very favor- able to nitrification. A similar experiment is reported by Muntz and Nottin. 1 They found that when 0.25 grams of nitrogen per kilogram of soil was used, the relative amount of nitrification in 5 months for different fertilizers was as follows: Per cent. Ammonium sulphate 100 Calcium cyanamide 88 Dried blood 66 Roasted leather 26 The above fertilization is equivalent to about 450 pounds of nitrogen per acre, and has no significance to practical agricul- ture. When, however, smaller amounts of Cyanamid were applied, nitrification was very rapid, and further, the bacteria rapidly adjusted themselves to the changed environment and enorm- ously increased their ability to nitrify Cyanamid nitrogen, even when successively increasing doses were applied. This is shown in the following table : Amount cyanamid Amount nitrogen applied nitrogen present Nitrate nitrogen each time at analysis before per kg. of earth Date applied grams new application by analysis January 17 0.06 — — January 26 0.06 0.06 — February 7 0.10 0.12 0.01 March 3 0.12 0.22 0.18 April 2 0.22 0.34 0.37 April 25 0.40 0.56 0.58 May 23 — 0.96 0.81 1 Annales de l'lnstitut National Agronomique, 2nd Series, Vol. VI, No. 1, 1907. 64 CYANAMID — MANUFACTURE, CHEMISTRY AND USES The rate of nitrification of Cyanamid is somewhat less than that of sulphate of ammonia when both are applied in large doses. In doses such as would be used in practical agriculture there is probably not much difference. The rate of nitrification must vary greatly in different soils and individual experiments can show but little of general application. As a general average of observations made in Germany, it appears that the duration of Cyanamid nitrogen in the soil is about 70-80 days. In very active soils it is probably less, in cold soils of low bacterial activity it is probably more. Its duration is there- fore about midway between that of ammonium sulphate and dried blood. CHAPTER VIII. Toxicity of Fertilizers. A review of the numerous agricultural experiments that have been reported since 1902, indicates that Cyanamid is not equally efficient as a fertilizer in all the conditions in which it has been applied. Cases have been noted where there was ap- parently an unfavorable action on germination of seeds, unless the fertilizer were mixed with the soil several days before the seed was sown. It is also said to be poorly adapted for use on acid moor soils or on very poor sand soils of low activity. Various explanations have been given of the cause of these undesirable effects. In some cases the occasional harmful action on germination has been attributed to the evolution of acetylene from a crude lime-nitrogen containing free calcium carbide; in other cases the causticity of the lime has been blamed, but usually the unfavorable action on acid moor soils or very poor sand soils is charged to the formation of dicyan- diamide by the acids in such soils. Meaning of "Poison." — It is well to agree at once upon what is meant by the term "toxin" or "poison." Dr. Paul Wagner 1 says "poison, as is known, is a very relative idea, for poisons in great dilution are harmless, and non-poisons in great con- centrations are harmful." It is obvious that the term "poison" could be applied to almost any substance if we do not limit the amount which is understood to be used. Unless, therefore, the amount which is said to be toxic is distinctly specified, it is necessary to assume that the amount used is small and popularly regarded as a safe dose. It is also desirable to agree upon the amount of injury that can be sustained before the effect can be pronounced as harmful. Some substances produce temporary exhilaration, followed by serious depression; other substances produce temporary depression, but leave the subject 1 Arbeit, der Deut. Landw. Ges., No. 129, p. 267, 1907. 66 CYANAMID — MANUFACTURE, CHEMISTRY AND USES in the long run better than before. Practically, from the stand- point of plant physiology, it seems necessary to define a poison as a substance which, administered in quantities ordinarily con- sidered small, produces functional disturbances ending ulti- mately in permanent injury or death. 1 In this connection it may be well to quote entire the con- clusions of Dr. Paul Wagner after seven years of experi- menting with lime-nitrogen, both in pot cultures and in the field. 2 CONCLUSIONS OF DR. PAUL WAGNER. "i. The statement 'lime nitrogen is a plant poison and must be converted by soil bacteria into ammonia and nitric acid in order to act as a fertilizer' has led to many faulty conceptions and is practically not correct. Poison, as is known, is a very relative term, for poisons in great dilution are unharmful, and non-poisons in great concentration are harmful. For instance, perchlorate occurring in nitrate of soda is a decided poison. If one sows 3 kg of perchlorate on a hectare of rye, there will be a poisonous action. Chile saltpeter should therefore contain not more than one-tenth of a per cent, of perchlorate; it should be rejected if it con- tains more than 1 per cent, of this poison. Likewise, ammonium sulphocyanate is a real plant poison. In the year 1873, in No. 38 of the Hessian Agricultural Journal, I com- municated a marked example of sulphocyanate poisoning. On the Rudigheimer estate at Hanau a grain field of 4 hectares was poisoned by an application of 100 kilograms of ammonium superphosphate with 10 per cent, nitrogen, which later in- vestigation showed to contain sulphocyanate. Therefore, this extremely slight amount of sulphocyanate was sufficient to cause a characteristic poisoning and to decrease the yield to about one-third. It has also been learned that ammonium sulphocyanate applied a greater or less time before sowing of 1 See also Pfeffer's Physiology of Plants, Ewart, Vol. II, 258. * Arbeit. Deut. L,andw. Ges., Heft 129, 1907, p. 267. CYANAMID — MANUFACTURE, CHEMISTRY AND USES 6j the seed, can under certain conditions be decomposed into ammonia, so that is no longer poisonous. Nevertheless, the sulphocyanates to the extent that they remain undecomposed in the soil are decided plant poisons and cannot be applied as fertilizers. "On the contrary, nitrate of soda, sulphate of ammonia, nitrate of ammonia, and carbonate of ammonia contained in manure, are known as very favorable nitrogen fertilizers and they are still regarded as such, although it is known that under certain conditions they can act disadvantageous^. Very con- centrated solutions of these nitrogen fertilizers, especially car- bonate of ammonia, can, as is evident from our contribution in Volume 66 of the Agricultural Experiment Station Reports, have a depressing action upon the development of plants, and under certain circumstances (which indeed do not occur in agricultural practise) they can produce complete destruction of the plant. No one, however, designates nitrate of soda, sulphate of ammonia or manure as plant poisons. In a similar manner it is known that fertilization with quicklime must be carried out with great care. Professor Tacke has determined by researches upon moor soils a very disadvan- tageous action of lime fertilization, and I, and others, have found that lime can act harmfully on ordinary soils if the lime is applied in too large quantities or at the wrong time. No one will, however call quicklime, which is known as a highly valuable fertilizer material, a plant poison. "In just the same way Cyanamid, or so-called lime nitrogen, is to be regarded not as a plant poison, but as a fer- tilizer, although it, exactly like quicklime and other fertilizers under some conditions, can act harmfully upon the growth of plants. Cyanides, sulphocyanates and similar nitrogen com- pounds are plant poisons ; they act poisonously in very great dilution and cannot serve as fertilizers under any conditions. Cyanamid, however, does not belong to this class, for this compound can act harmfully or poisonously upon plants only in case of very wrong methods of application. 68 CYANAMID — MANUFACTURE, CHEMISTRY AND USES "When Prof. Frank requested me six years ago to test Cyanamid as to the conditions under which it could be used as a fertilizer and its relative fertilizing value, I had already been preparing to undertake the test; but I had ex- pected, on the ground of observations made with cyanides and sulphocyanates, a completely negative result from the experi- ments. "Our experiments carried out in the laboratory and on small experimental plots have not confirmed my previous assump- tion. Our field experiments have shown that the application of lime nitrogen as a fertilizer was attended with less difficulties than one could directly conclude from the experi- ments carried out in the laboratory and on small experimental plots. Very concentrated solutions of lime nitrogen or ex- ceptionally large applications of this fertilizer act harmfully upon the plants, as is clearly seen from our pot experiments (see page yi and Fig. 5). Under the normal conditions of agricultural practice, however, a disadvantageous action does not occur, if one follows the directions given for the applica- tion of Cyanamid, and these consist essentially in this that the lime nitrogen must not be applied in excessive quantities and further must not be applied upon acid soils or soils which tend to become acid ; that it must be distributed as uniformly as possible upon the surface of the field, and must then be worked into the ground, when it is not used as a top dresser, by deep acting tools, or be plowed under. "To illustrate, it should be noted that in our experiments (see page 71) an application of 1 gram of nitrogen in the form of lime-nitrogen upon 7 kilograms of soil contained in a vessel 20 cm. in diameter did not act harmfully, but acted favorably from the beginning to the end upon the plant growth even when the lime nitrogen was mixed with the soil im- mediately before planting of the seed. Upon a circumference of 20 cm. diameter, however, one does not apply in agricultural practice 1 gram, but only one-tenth or at the highest two-tenths of a gram of nitrogen. It is therefore clear that one can CYANAMID — MANUFACTURE, CHEMISTRY AND USES 69 uoyoo -Ifdcfo fiyi/9U/M9^$) u/0^6 j.o PI 9)1 /O CYANAMID — MANUFACTURE, CHEMISTRY AND USES regard the disadvantageous action of lime nitrogen, such as happens under applications of exceptionally large quantities in pot experiments as either not occurring in agricultural practice or as immediately disappearing. Practically, one cannot there- fore regard lime nitrogen as a plant poison. It is to be regarded as a fertilizer applicable in agricultural practice and having a favorable action, although as is necessary with barn manure, green fertilizers, bone-meal, horn meal, etc., the nitro- gen contained in it must be converted by bacterial activity into ammonia and nitric acid in order that it may serve as plant food. "2. If lime nitrogen is applied in normal quantities, as com- pared with other fertilizer materials, distributed as uniformly as possible upon the soil, and worked in well with deep-acting tools, it exerts no harmful influence even when applied im- mediately before sowing of the seed. The idea that lime- nitrogen must be completely, or at least to a great extent, converted into ammonia or nitric acid before it comes into con- tact with the seed is wrong, although it is possible that the action of lime nitrogen in many cases can be increased if it is applied 8 or 14 days before sowing of the seed. "3. Lime nitrogen in ordinary field practice can act harm- fully only when conditions are such that a part of the calcium cyanamide suffers an unnormal decomposition. Conditions under which this can happen are present especially in acid moor soils or in soils which tend to become acid, or soils very rich in humus, and therefore very poor in lime. It is known that moor soils acts otherwise than normal towards other nitrogen fertilizers as well. Sulphate of ammonia has an unfavorable action upon acid soils. In order to avoid these unfavorable conditions of acid soils previous liming is necessary. "4. Like all organic nitrogen fertilizers, green substances, barn manure, horn meal, etc., the conversion into ammonia and nitric acid is necessary in order to yield nitrogen assimilable by plants, and like ammonia (although many plants take it up and use it as such), for most plants it has its full effect only CYANAMID — MANUFACTURE, CHEMISTRY AND USES Jl when it is converted into nitric acid ; so the nitrogen of the lime-nitrogen must be converted into ammonia and nitric acid before it will yield nitrogen that the plants can assimilate. "5. It is known that the conversion of Cyanamid and the organic forms of nitrogen into ammonia and nitric acid is brought about by the activity of certain soil bacteria and that this conversion, according to the special activity of the soil, sometimes proceeds more rapidly and sometimes more slowly. Upon so-called medium soils in good condition the organic fertilizers as a rule act more completely than upon light dry sandy soils or upon heavy clay soils. The medium loam soils in good condition seem to offer comparatively the best con- ditions for the action of lime nitrogen. Whether the con- version of calcium cyanamide into ammonia proceeds by an intermediate formation of urea is unproved." The above was written by Dr. Wagner before the mechanism of the conversion of Cyanamid in the soil had been worked out. These later researches show that the conversion is both physico-chemical and biological, as has been set forth in Chapter V. The experiments on the effect of concentration to which Dr. Wagner refers were made in vegetation pots with a variety of nitrogenous compounds, on various types of soil, and with various crops. All the results point to the same general conclusion, which is illustrated in Fig. 5. This test was made with oats planted on a sandy-loam soil, in pots 20 cm. high and 20 cm. in diameter. The seed was planted on the day of fertilizing, May 9, 1905, and the grain harvested on July 14, 1905. The lime-nitrogen contained 20.06 per cent, nitrogen, and the calcium nitrate (commercial grade) con- tained 11.65 P er cen t. nitrogen. 1 The yields of grain are plotted against the amounts of nitrogen applied to the soil (Fig- 5). Each of these curves is an illustration of the Law of Diminishing Returns. For the smaller applications of nitro- 1 Landw. Vers. Stat., 66, IV-V (1907), p. 346. 6 J2 CYANAMID — MANUFACTURE, CHEMISTRY AND USES gen, the increased yield is almost proportional to the amount of nitrogen applied, but the rate of increase drops off rapidly until a point is reached where further applications not only do not increase the yield but tend to decrease it. If too much fertilizer is applied the plant may even be killed. The "burn- ing" and occasional destruction of vegetation by excessive applications of fertilizer salts is well known to agriculturists. A similar phenomenon has been investigated by Headden and Sackett 1 in Colorado, where it was shown that the formation of excessive quantities of nitrates has caused in some cases the total destruction of all plant life, often over areas miles in extent. Toxicity, therefore, is a question of the amount of fertilizer applied. All of the common, nitrogenous, mineral fertilizers may have a toxic action if too much is used, but with the ordinary applications of practical agriculture none of these materials is toxic. Experience has determined the maximum quantities of nitrogen that can be economically utilized by the various crops under various soil conditions, and the possible effects of larger quantities than this maximum economical quantity in each case have little interest to the practical farmer. Cotton, corn, wheat, oats, and similar crops seldom economically utilize more than 15 to 25 pounds of nitrogen per acre. Sugar beets and sugar cane may utilize as high as 40 to 50 pounds. Potatoes, truck crops, some fruits, and tobacco may utilize as high as 60 to 70 pounds of nitrogen per acre. With such applications it is doubtful if any of the mineral fertilizers in question would exert a toxic action on the plant, even if they were applied alone, provided the time and method of applica- tion were suitable. As a matter of fact, however, when large applications of nitrogen are desired, it is customary to mix several kinds of nitrogenous materials together and to apply the mixture in several portions, instead of all at one time. Moreover, agri- 1 Colorado Exp. Sta. Bulletiu 179, 191 1. CYANAMID — MANUFACTURE, CHEMISTRY AND USES /3 cultural experience has shown that nitrogenous fertilizers are not utilized as economically when applied alone as when they are used in conjunction with phosphates and potash salts; the presence of phosphorus and potassium seems to greatly modify the ability of the plant to assimilate nitrogen. As a general rule, it is seldom, indeed, that more than 25 pounds of nitro- gen, derived from a single source, is applied at one time, unaccompanied by phosphates and potash. In normal agri- cultural practice, therefore, the question of toxicity of the common nitrogenous fertilizers may be disregarded. If the farmer wishes to depart from the normal practice, it is usually best to follow the instructions issued by fertilizer manufac- turers for the use of their products. Such instructions usually designate 20 to 25 pounds of nitrogen per acre as the maximum application, and recommend that the material be applied during the preparation of the soil a week or more before the seed is sown. They also caution against the danger of direct contact of the undiluted fertilizer with the leaves or roots of the plant. OTHER EXPLANATIONS OF TOXIC ACTION. Whether or not acetylene, which may be generated by the action of moisture on a lime-nitrogen containing calcium car- bide, is harmful to plant life, is of little interest to the Cyanamid industry, since the material prepared for use as a fertilizer does not contain calcium carbide. The lime-nitrogen made in Europe in former years, sometimes contained slight amounts of carbide but it is extremely doubtful if there were any harmful effects from this ingredient. H. Kappen 1 and E. Haselhoff 2 claim that they could observe no harmful effects of acetylene on plant growth. No reports have been found which show that acetylene may be harmful. The free lime in the German "kalkstickstoff" or lime- nitrogen is in the form of calcium oxide, while in the Ameri- 1 Fuhling's Landw. Zeit, Apr. 1908, 286. 2 Landw. Vers, stat., 68, 1908, Nos. 3 and 4. 74 CYAN AMID — MANUFAC CHEMISTRY AND USES is the i ■ of calcium hydroxide and . . »cts of the lime in either form upon plant :". - .r'.y by Wagner in the extract quoted ie anion::: : ... calcium in Cyananiid. ex- ... 5 about 55 ied to the s s ne :essarily lim ted : E nitrog an hardly reach such an amount that it 1th plant g regard to the on of Cyananiid on es that the same a - mium sulphate, and that the bad effects the a i ma - to aj E the Eertilizer. Soils which are acid is rule unfit for : igr :ulture, and should be ato g - judicious liming. Fer- le harmful ^uc;:? of dons stitute the limiting factor in a a . nditions must . :or- recte f .mamid, O.ould not be ap: soils with the ex:. _ rofit unless : . unfavorable con- tions > liming The quantity of Cyana 2 of some assisl - nsufifi- -. which require Erequently as much tons slaked lime in them to anamid on -. I soils has uted to the possible formation of dicyan- r.anamide. That there is no chem- sis for this ill be shown DICYA^-DIAXTDE. ..ndiamid: :::uch discussed in ture tt - ssary, in order il understa g El • - xt i rom the mass CYANAMID — MANUFACTURE, CHEMISTRY AND USES 75 of experimental data that have been reported the results that are consistent with all the known facts, and then to reconcile the apparent disagreements with the consistent facts. Formation. — The researches of Ulpiani 1 show without doubt that acids do not determine the formation of dicyandiamide from calcium cyanamide. Acids acting on calcium cyana- mide produce calcium salts and free cyanamide. By the further action of the acids, from the weakest to the strongest, there is formed first urea, and secondly, especially in the case of weak acids, ammonium salts. (See also p. 12). F. Lohnis and R. Moll 2 found that even humic acid, in excess, acting upon lime-nitrogen for 8 days at 40° C. produced not the slightest trace of dicyandiamide. There is no evidence of any kind to show that acids ever produce dicyandiamide from cyanamide. Neither do strong alkalies produce dicyandiamide, but always produce urea and free ammonia. Weak alkalies, however, and especially calcium hydroxide, readily effect the polymerization, although in this case also there is formed con- siderable urea. The formation of dicyandiamide in lime- nitrogen is brought about by the combined action of moisture, which causes the hydrolysis of calcium cyanamide to cyan- amide, and lime which determines its polymerization to dicyan- diamide. These reactions take place at ordinary temperatures very slowly, as shown below, but proceed very rapidly above yo° C. At about 100 9 C. other reactions begin with formation of ammonia and small amounts of other derivatives. Water and heat alone do not cause the polymerization to dicyandi- amide; Ulpiani boiled a pure solution of cyanamide 50 hours without any change. 3 Decomposition. — In a solution of lime-nitrogen, dicyan- diamide forms and decomposes simultaneously. This is seen 1 Gaz. Chim. Ital., 1908, II, No. 4, 358.417. ? Centl. Bakt. XXII, 276. '■'' Rend. Soc. Chim. di Roma. p. 4 1906. /6 CYANAMID — MANUFACTURE, CHEMISTRY AND USES in the following table by G. Liberi, 1 showing the content of cyanamide and dicyandiamide nitrogen in solutions of lime- nitrogen made by extracting with cold water and filtering and maintaining at 27 ° C. The figures are given as percentages of the original lime-nitrogen. Dilute solution i per cent, lime Concentrated solution 5 per cent, nitrogen • lime nitrogen Time elapsed in days Nitrogen as cyanamide per cent. Nitrogen as dicyandiamide percent. Nitrogen as cyanamide per cent. Nitrogen as dicyandiamide per cent. O 18.63 — 18.63 — I 16.38 O.46 14.56 O.70 2 14.42 O.56 II.76 i-54 6 12.74 O.62 9.IO 2.84 II I0.22 O.50 5.18 2.24 18 7.42 o-39 i-75 1.71 31 3.OI 0.38 0.00 1-25 45 O.OO o.34 — 0.84 58 — 0.28 — o.53 76 — 0.22 — 0.23 The maximum amount of dicyandiamide occurs in each case at the end of 6 days' standing. The decomposition of the dicyandiamide is very slow, as is seen in the concentrated solution after the 31st day, when all the Cyanamid has been removed, and no more dicyandiamide can form. Its rate of formation is somewhat faster, and is undoubtedly determined by the concentration of both nitrogen and calcium. The per- centage of the total nitrogen transformed to dicyandiamide is about five times as great in the concentrated as in the dilute solution. With the removal of the cyanamide it was observed that crystals of pure calcium hydroxide settled out on the walls of the vessel. The rapid disappearance of the cyanamide shows that the formation of other derivatives of cyanamide in this solution is much more rapid than the formation and decomposition of dicyandiamide, and it is therefore evident that most of the cyanamide decomposes directly to these other derivatives, and not through the dicyandiamide form. The largest part of 1 Annali Staz Chim. Agrar. Sper di Roma Series II, V, 191 1. CYANAMID MANUFACTURE;, CHEMISTRY AND USES JJ these other derivatives is urea, and the balance is amidodi- eyanic acid, melamine and ammeline. (See also p. 29). Conversion in Soil. — The chemical behavior of dicyandiamide in the soil has not been studied in the thorough manner in which that of cyanamide has been studied, and much of the data at hand is invalidated by the fact that enormous quanti- ties of nitrogen were used. It is necessary to draw our con- clusions solely from the vegetation tests that have been reported. A review of these culture tests will show that they fall into two classes ; one, in which chemically pure dicyandiamide was used, and the other in which home-made dicyandiamide was used. Among the prominent investigators who used pure dicyan- diamide are Wagner, Kappen, Sabaschinkoff, Lohnis, Brioux, and C. J. Milo. Their results show that chemically pure dicyandiamide has practically no fertilizing value but on the other hand may have slight toxic action if more than 45 pounds of dicyandiamide nitrogen per acre is applied. The results are in such agreement that it will not be necessary to quote them here. Among those who used dicyandiamide prepared in their own laboratories are Perotti, Ulpiani, R. Inouye and K. Aso. They found that home-made dicyandia- mide has a fertilizing value equal to that of ammonium sul- phate provided it is not used in quantities exceeding 100 pounds of nitrogen per acre. Perotti, 1 for instance, in pot tests with wheat, grown to maturity, obtained the maximum crop with 75 pounds of nitro- gen per acre in the form of home-made dicyandiamide. The increase in yield over the control pot without nitrogen was about 100 per cent. With buckwheat the maximum crop was obtained with 150 pounds of nitrogen per acre, and the in- crease in yield was about 200 per cent. With flax the maximum yield was with 300 pounds of nitrogen, and the increase in yield was about 60 per cent. 1 Cent. Bakt. XVIII, 55, 1907- Pounds nitrogen from ammou. sulphate Pounds nitrogen from dicyandiamide Average \ of one p green rape. — — 5-o 240 160 80 59-4 62.6 160 80 64.0 — 240 8.4 78 CYAN AM ID — MANUFACTURE, CHEMISTRY AND USES R. Inouye 1 made pot tests with rape and barley, fertilizing with a dicyandiamide made by himself from lime-nitrogen, and and analyzing 46.7 per cent, nitrogen. The rate of fertiliza- tion was equivalent to 2,400 pounds superphosphate per acre, 1,200 pounds potassium carbonate and the amounts of nitrogen shown in the table below, which gives also the yield obtained : it Average weight of one plant green rape. Grams air-dry, barley. Grams 1.8 8-3 9.0 9.0 2-5 The dicyandiamide in the fourth pot was applied as a top- dressing. Although the fertilization was very heavy there is no doubt that the results are very good when 80 pounds of nitrogen from impure dicyandiamide is used with ammonium sulphate, although 240 pounds of nitrogen from dicyandiamide alone is little better than no fertilizer. This is clearly an ex- cessive amount of dicyandiamide. K. Aso 2 made some toxicity tests with a dicyandiamide made by himself from lime-nitrogen, and analyzing 59.88 per cent, nitrogen. Buckwheat and oat plants were grown to a height of about 10 cm. in ordinary soil and were then trans- ferred to flasks containing solutions of different concentrations of dicyandiamide. When the solutions contained less than 0.01 per cent, of nitrogen from dicyandiamide the plants con- tinued growing normally and developed better than in the control flasks. When larger concentrations were used the plants showed the characteristic effects of dicyandiamide poisoning; that is, for increasing doses, first, appearance of a brown color on the tips of the leaves, then drying of the tips, although usually followed by recovery and increased growth ; finally, with very large concentrations, curling and drying up of the leaves and destruction of the plant. Here, as with 1 Jour. Coll. Agr. Imp. Univ. Tokyo, Vol. I, No. 2, 1909, p. 193. 2 Jour. Coll. Agr. Imp. Univ. Tokyo, Vol. i, No. 2, 1909, p. 211. CYANAMID — MANUFACTURE, CHEMISTRY AND USES /9 Cyanamid and other fertilizers, toxicity is a question of con- centration, although the specific toxicity of pure dicyandiamide is considerably larger than that of impure dicyandiamide. Some tests were also made with rice transplanted to field plots (0.83 qm.) manured alike with superphosphate, potassium carbonate and nitrogen compounds at the rate of 90 pounds per acre each of phosphoric anhydride, potash and nitrogen (except control). The nitrogenous substances were am- monium sulphate containing 21.2 per cent, nitrogen, lime-nitro- gen with 12.47 P er cent - nitrogen, and dicyandiamide with 46.7 per cent, nitrogen. They were applied at different periods be- fore the transplanting of the rice clumps. The total weight in grams of the plants obtained in the air dried state were : Fertilized days before planting Fertilized with o 7 14 21 28 35 No manure 229 — — No nitrogen 436 — Ammonium sulphate • • 764 — — — Lime-nitrogen 614 767 7S6 807 788 744 Dicyandiamide 507 575 572 670 652 609 The yield of clean grain was as follows : Fertilized days before planting Fertilized with 7 14 21 28 35 • 75 149 — — — — Ammonium sulphate.. 266 Lime-nitrogen 197 259 260 258 280 257 ■ 183 20S 209 238 244 239 This experiment shows a somewhat lower result with lime- nitrogen than with ammonium sulphate applied at the time of planting, but a somewhat larger yield when the lime-nitrogen is applied 7 days before planting. The dicyandiamide is more effective when applied two or three weeks before planting than when applied at the planting, but it is never as effective as the ammonium sulphate, being at the best about 89 per cent, as effective in producing grain. In the cultivation of rice in America the maximum utilizable application of nitrogen does 80 CYANAMID — MANUFACTURE, CHEMISTRY AND USES not exceed 10 pounds per acre. Hence, the above quantities are many times larger than any met in agricultural practice. A similar experiment was made in pots containing 8 kg. of soil, manured with double superphosphate, potassium sulphate and nitrogen at the rate of 120 pounds of P 2 5 , K^O and N per acre respectively. The lime-nitrogen contained 11.8 per cent. N and the dicyandiamide 59.9 per cent .N. The yields in grams of air-dry plants were as follows : Fertilized days before planting Fertilized with o 7 14 21 Ammonium sulphate •••67.5 — — — Lime-nitrogen 65.6 69.6 70.6 74.8 Dicyandiamide 66.6 74.3 73.8 71.5 The yields of grain were : Fertilized days before planting Fertilized with o 7 14 21 Ammonium sulphate • • • 29.5 Lime-nitrogen 28.3 30.0 29.5 33.2 Dicyandiamide 30.5 33.5 31.7 33.7 In this experiment the highest results were obtained with dicyandiamide applied a week before planting. When applied at the time of planting the results are about the same as those with ammonium sulphate. PURE SUBSTANCES AND TOXICITY. There are several observations reported in the literature that may help us to understand why a chemically pure dicyandia- mide should be toxic, while an impure dicyandiamide may have a fertilizing value equal to that of ammonium sulphate. It has been noted by Sabaschnikoff 1 that a fertilization with chemically pure calcium cyanamide, in comparison with lime- nitrogen containing the same amount of nitrogen, gives only from one-third to one-half as large an increase in yield as is obtained from the lime-nitrogen, both being applied under exactly the same conditions. C. J. Milo 2 made some experiments on sugar cane, in which 1 Mitt. Landw. Inst., Univ. Leipzig, Vol. IX 1908, p. 106. 2 Archief voor de Suikerindustrie in Nederlandsch-Indie, 20, 482-539. CYANAMID — MANUFACTURE, CHEMISTRY AND USES 8l the sugar cane, in baskets, was watered one month and two months respectively after planting, with solutions of lime- nitrogen (6 per cent, calcium carbide), pure cyanamide, CN.NHo, basic calcium cyanamide, urea and dicyandiamide. The solutions contained each an amount of nitrogen equivalent to an application of 75 pounds per acre. The pure cyanamide proved very toxic and two out of three plants were killed after the second application. About two weeks after the second application, probably when the cyanamide had been converted to other forms, the remaining plants in this basket began to grow luxuriantly. The basic calcium cyanamide caused the plants to look sick temporarily, and they remained inferior. The dicyandiamide (98.5 per cent, pure) was not as intense in its action as pure cyanamide, causing no destruction, but the bad effects lasted longer than those of pure cyanamide, and the plant seemed to lack nitrogen nourishment. The urea caused luxuriant growth from the time of application, and was slightly better than the sulphate of ammonia and lime-nitrogen applications. The lime-nitrogen and sulphate of ammonia solutions produced full grozvth and zvere equally effective. It appears therefore, that the fertilizing value of lime- nitrogen, decidedly can not be judged from the fertilizing action of pure cyanamide or pure calcium cyanamide, and that the fertilizing value of impure dicyandiamide is quite different from the fertilizing value of pure dicyandiamide. It seems that the plant is unable to utilize these pure compounds of nitrogen, but that in lime-nitrogen there are some substances that neutralize such toxic compounds, or help remove them, or that act upon the plant in such a way as to enable it to with- stand the toxic properties until they are destroyed by the con- version of the cyanamide and its polymers by the catalytic action of the soil. It is quite possible for instance, that the lime and the extremely finely divided carbon in lime-nitrogen may play a part in the rapid decomposition of the cyanamide. It is also possible that the urea, and other derivatives that are so easily formed from cyanamide, furnish the plant with 82 CYANAMID — MANUFACTURE, CHEMISTRY AND USES nourishment that enables it to withstand otherwise toxic effects that might check growth if such nourishment were not avail- able (see also page 34). Conclusion. — Toxicity of Cyanamid is simply a question of concentration. Under normal soil conditions and with the normal applications of practical agriculture there are no un- usual effects on the germination of the seed or on the growth of the plant. This is verified constantly in the extensive use of Cyanamid in agriculture. CHAPTER IX. Agricultural Use of Cyanamid. Fertilizer Tests.— In the selection of the most economical fertilizer it is necessary to consider, among other things, the nature of the crop, the qualities desired in the plant grown, the type of soil, the effect of long-continued use of the fer- tilizer, the cost and the relative yields. Thus, the rice-plant seems to be unable to assimilate nitrates easily, but readily assimilates ammonium compounds. 1 The quickly acting forms of nitrogen usually produce rank, heavy growth of the green parts of the plant, with little fiber, while the slowly acting forms produce thinner leaves, and stems with greater strength. For forcing purposes, the nitrates are ideal ; for slow, steady growth, the organic forms of nitrogen, Cyanamid, ammonium sulphate, etc., are to be preferred. Soil conditions are often a determining factor. Thus, loose, open soils in regions that receive a great deal of rain do not readily retain nitrates. Soils of low lime content may become acid by the addition of ammonium sulphate year after year: the sulphate radical enters into combination with the lime of the soil and carries away the calcium in the drainage waters. 2 Very acid soils are not economically fertilized with substances like Cyanamid, ammonium sulphate and other materials requir- ing nitrification, since nitrifying bacteria are notably deficient in acid soils, especially acid sandy soils. Such soils should be put into productive condition by proper judicious liming, some time previous to the fertilization. On light, sandy soils where heavy liming may damage the crop the yearly addition of a small amount of lime as a part of the fertilizer is of great assistance in overcoming the tendency towards acidity. The relative yields per unit of money invested in the different fer- tilizers is often the controlling factor in their selection, but 1 Hawaiian Agr. Exp. Sta. Bulletin 24. 2 A. D. Hall, Fertilizers and Manures, p. 62, 1909. 84 CYANAMID — MANUFACTURE, CHEMISTRY AND USES since prices vary, it is customary to express the yields on the basis of equal applications of nitrogen. There is therefore a large number of factors that affect the selection of the most economical fertilizers. The statistical method of merely averaging the yields of a large number of experiments regardless of their character, does not give very much practical information. The errors of experimentation with Cyanamid are usually in one direction, and hence do not offset one another. One of the most common errors is the use of quantities of nitrogen far in excess of what would be applied in practical agriculture, as indicated on page 69. It is shown in Fig. 5 that the relative efficiency of utilization, of the nitrogen in various compounds is not the same at all applications. The relative values at an application of 1 gram per pot are entirely different from the relative values at 0.5 grams, or at lower applications. Moreover, the order of superiority may be different at different applications, as shown on the calcium nitrate curve. At the lower concentrations, such as obtain in practical agriculture, under favorable soil conditions, all of the common nitrogenous mineral fertilizers have about the same efficiency of utilization, in this experiment. Not only is it a mistake to assume that results obtained at one concentration will hold true for other concentrations, but it is. of course, equally wrong to assume that an average of the results at various concentrations will hold true for a particular concentration. The relative effi- ciencies also vary with the nature of the soil and with the crop. Results obtained on sand may not hold on clay, and vice versa. Acid soils may act differently from neutral or alkaline soils. A nitrogenous fertilizer applied alone usually gives entirely different results when mixed with other nitro- genous fertilizers, or with phosphates, acid or basic, or with potash salts. A source of error that has probably vitiated many of the reported experiments is the readiness with which unhydrated lime-nitrogen changes in weight, by absorption of moisture CYANAMID — MANUFACTURE, CHEMISTRY AND USES 85 and carbon dioxide, especially when stored in small quantities. It is possible that a great many investigators have purchased lime-nitrogen at a certain analysis, have allowed the material to remain exposed to the atmosphere several months, and have then weighed out the fertilizer for the test, assuming that its analysis is practically the same as when it was bought. The error introduced by the weighing up of the fertilizer one month after analysis may amount to 5 to 8 per cent, of the total nitrogen, in the case of a single bag exposed in a damp climate. In America, where the Cyanamid is completely hydrated, the error is much less (see p. 27), but it is still large enough to make it desirable to have the fer- tilizer weighed out shortly after the analysis is determined. Another error is the application of Cyanamid only a short time before the harvest. Since Cyanamid may take 70 to 80 days 1 to be completely utilized, it is obvious that the maximum efficiency is obtained only when the application is made not less than 70 to 80 days before the harvest. The main purpose of a fertilizer test is to determine the rela- tive profits that can be made by the use of different fertilizers. In view of the difficulties of experimentation, and the danger of drawing unwarranted conclusions from insufficient or irrelavant data, as pointed out above, probably the only fair test of a fertilizer is obtained zvhen it is applied under the con- ditions that prevail where the consumer uses it. All other methods require special proof that the results obtained experi- mentally would also be obtained practically, and such proof is not always available. To illustrate the considerable variation in the results obtained with different materials in different conditions, a few of the results of prominent investigators are give here. Thus, Strohmer, with sugar beets, obtained as an average of 7 fields, 100 pounds of sugar when sodium nitrate was used, to 104 1 Dr. A. Frank, private communication. 86 CYANAMID — MANUFACTURE, CHEMISTRY AND USES pounds of sugar when lime-nitrogen was used. 1 J. Kloppel 2 obtained yields of sugar beets with no fertilizer, sodium nitrate and lime-nitrogen respectively of ioo, 127, and 149, while the yields of sugar were 100, 99, and 130. As an average of 10 cereal and root crops in 29 field experiments, Steglich 3 assigned the following values to the various materials : no fertilizer, 81 ; sodium nitrate, 100; ammonium sulphate, 95; and lime-nitro- gen, 96. Schneidewind, 4 as an average of 5 cereal and root crops reports that the increase in yield over the fields un- fertilized with nitrogen were comparatively, sodium nitrate, 100; ammonium sulphate, 88; and lime-nitrogen, 73. Wagner, Director of the Experiment Station at Darmstadt, 5 as a sum- mary of 11 field tests on cereals with 27 pounds or less of nitrogen per acre, reports the increased yield over the fields without nitrogenous fertilizer, comparatively as follows : Sodium nitrate, 100; ammonium sulphate, 87; and lime-nitro- gen, 94. Miintz and Nottin, as an average of 11 field tests with wheat report the following comparative yields obtained: Cyanamid, 100; ammonium sulphate, 94; dried blood, 96. ° USE AS A WEED DESTROYER. In Germany, lime-nitrogen is used to a considerable extent for the destruction of obnoxious weeds, such as wild mustard, occurring in grain crops, particularly oats. The fine, dry, lime- nitrogen is scattered either by hand or by machine early in the morning when the leaves are wet with dew, or after a rain, at the rate of 60 to 90 pounds per acre. The lime-nitrogen readily clings to the rough, hairy, almost horizontal leaves of the wild mustard, and forms a concentrated solution in the moisture on the leaves. This tends to dilute itself by osmosis and brings 1 Oesterr-Ungar., Zeit. fur Zuckerindustrie und Landwirtschaft, XXXV, No. VI, 1906, 676. 2 Fuhling's Landw. Zeit., 56, No. 15, 1907, p. 539. 3 Fuhling's Landw. Zeit., 56, No. 22, 1907, p. 780. 4 Arbeit. Deut. Landw. Ges., No. 146, 1908, p. 116. 5 Arbeit. Deut. Landw. Ges., No. 129, 1907. 6 Annales de l'lnstitut National Agronomique, 2nd Series, Vol. VI, No. 1. See also pp. 45-47- CYANAMID — MANUFACTURE, CHEMISTRY AND USES 87 about the destruction of the mustard within a few days. The application is made when the mustard plant is young, best when it has only four or six leaves. The more leaves it has the more lime-nitrogen will be required. The grain crop may be affected a little immediately after the application, and may turn somewhat brown at the tips of the leaves, but it will quickly recover and become much greener than the grain in untreated fields. The leaves of the grain crops, especially oats, stand almost vertical and are comparatively smooth and waxy, so that very little lime-nitrogen clings to them and no permanent damage is done. Practically, this method of de- stroying wild mustard is quite economical, since the nitrogen applied in this way seems to have as full fertilizing effect as if it were applied under the crop. The mustard, on the other hand, is practically eradicated. DIRECTIONS FOR APPLICATION AS FERTILIZER. Very little of the Cyanamid made in this country is applied alone, practically all of it being used as a part of mixed fertilizers. For the guidance of those who wish to use it with- out admixture with other materials, the following suggestions are offered, although it should be recognized that a true test of the efficiency of the Cyanamid used in this country is made only under the conditions in which it is usually applied, that is, as a part of a mixture containing phosphoric acid, potash, and frequently other forms of nitrogen. Cyanamid is least efficient when applied as a top-dressing. This is probably due to the quick reaction and fixation in the soil, so that much of the nitrogen is retained in the upper layers of soil where the plant roots do not reach it readily. The application should be made in such a way that the Cyanamid will be buried about where the plant roots are expected to grow. It should be scattered through the lower layers of cultivated soil as much as possible, so as to favor the greatest spreading of the roots. In the event of a dry season, the larger the root system, the better will be the ability of the 88 CYANAMID — MANUFACTURE, CHEMISTRY AND USES plant to withstand drouth. Dropping the fertilizer in narrow rows favors the development of bunched root systems, which will do very well as long as the supply of fertilizer lasts and the water supply is good, but are insufficient for the demands of the plant in dry weather. If the application is large broad- casting one-half or two-thirds of the fertilizer before plowing, or after plowing and before harrowing, with the application of the remainder in the row before seeding, or along the row after the plants are up, will be found to produce the best results. Care should be taken that the fertilizer is well mixed with the soil and that pure fertilizer and seed are not in direct contact, thereby avoiding the so-called "burning" of young plants. When the fertilizer is applied alongside the rows after the plants are up, it should be well worked in with the cultiva- tor or with hoes. Care should be taken not to get highly con- centrated fertilizers on the leaves of the plant, especially if the plant is wet. Since Cyanamid is a medium-slow-acting fer- tilizer, it should be applied to the crop not less than 70 to 80 days before the harvest, in order that the nitrogen may be completely utilized by that crop. The quantity of Cyanamid that can be economically applied at one time is preferably limited to 150 pounds per acre. Experience has shown that the most economical utilization of a nitrogenous fertilizer is obtained when it is used in con- junction with the other fertilizing elements, phosphorus and potassium. For this reason, it is recommended that Cyanamid be used as a part of a fertilizer mixture, rather than that it be applied alone. If Cyanamid is to be applied to very acid soils, such soils should be put in productive condition by thorough judicious liming some time before the application of the fertilizer. The application of barnyard manure will help to establish the bacteria that are deficient in such soils. When Cyanamid is applied alone, better results will be ob- tained if it is applied several days before the seed is sown, especially if the applications are large. For small applications, CYANAMID — MANUFACTURE, CHEMISTRY AND USES 89 when care is taken to mix the fertilizer well with the soil, the seed may be planted directly after the fertilizer is spread. Even distribution of the Cyanamid is facilitated by previously mixing it with two to three times its weight of damp earth. USE OF COMPLETE FERTILIZER MIXTURES. Since most of the Cyanamid used in this country comes to the farmer as an ingredient of mixed fertilizers, it is as a rule not necessary to have special instructions for its use. From the known chemistry of calcium cyanamide it is very probable that when Cyanamid is mixed with acid phosphate, the phos- phoric acid causes a considerable conversion of Cyanamid nitrogen to the form of urea, (page 12). At any rate, the ordi- nary practice in the use of mixed fertilizers is such that the presence of Cyanamid nitrogen will not require any modifica- tion of the usual practice. CHAPTER X. Making Fertilizer Mixtures with Cyanamid. MIXTURES WITH AMMONIUM SALTS. Cyanamid contains about 55 per cent. CaO, of which about 30 per cent, is present as CaCN„, 21 per cent, as Ca(OH) 2 , and 4 per cent, as CaC0 3 and other forms. Most of the calcium, therefore, dissociates readily and can react when brought into contact with certain bodies. In the presence of ammonium sulphate for instance, a double decomposition takes place as follows: Ca(OH) 2 + (NH 4 ) 2 S0 4 — CaSO, + 2 NH 3 + 2 H 2 0. Hence, if Cyanamid and ammonium sulphate are mixed alone there will be a large loss of ammonia. The same kind of reaction takes place with other ammonium salts. If, however, as is practically always the case, there is present an adequate amount of acid phosphate or other acid material, the acid of the acid phosphate immediately fixes the free ammonia and prevents its escape. The ammonia is com- bined probably as ammonium phosphate or as calcium ammo- nium phosphates, or both. To prevent loss of ammonia, there- fore, it is only necessary to have a sufficient amount of acid material present so that the resulting mixture will be acid in reaction. This condition is obtained when the amount of Cyanamid does not exceed 100 pounds of powdered Cyanamid or 200 pounds of granulated Cyanamid per 800 pounds of ordinary acid phosphate containing 14 or 16 per cent, of available phosphoric acid. Such mixtures have been tested in practical fertilizer manufacturing and show no losses of ammonia. The quantity of ammonium sulphate present is practically immaterial. Acid fish contains some nitrogen as ammonium sulphate, and should be mixed in accordance with the above rule. CYANAMID — MANUFACTURE, CHEMISTRY AND USES 91 MIXTURES WITH ACID PHOSPHATE. In ordinary acid phosphate analyzing 16 per cent, available phosphoric acid, there is usually found about 5 per cent, as free phosphoric acid, 9 per cent, as mono-calcium phosphate, and 2 per cent, as di-calcium phosphate. When such a phos- phate is mixed with Cyanamid there is obviously a neutraliza- tion of free acid, and of acid hydrogen of the mono- and di- calcium phosphate, the extent of the reaction depending upon the amount of active lime introduced by the Cyanamid. The neutralization is, of course, attended by evolution of heat, and this heat is the cause of the unfavorable results of mixing large quantities of Cyanamid with acid phosphate. In America, phosphates are sold on the basis of their con- tent of phosphoric acid soluble in ammonium citrate solution of standard strength, since it has been shown that there is no appreciable difference in the agricultural value of the water- soluble and the citrate soluble part of the phosphate. It is to the interest of mixers of commercial fertilizers to prevent the neutralization of the acid phosphate beyond the di-calcium or citrate soluble stage. With increasing quantities of CaO the following reactions should take place successively, but with relatively decreased velocity: (a) H 6 P 2 8 + CaO — CaH 4 P.A + H,0, Phos. Acid. Water Sol. (b) CaH 4 P 2 O s + CaO — Ca 2 H 2 P 2 8 + H 2 0, Water Sol. Citrate Sol. (c) Ca 2 H 2 P 2 H + CaO — Ca s P 2 8 + H 2 0. The last reaction would require a vast excess of CaO, since CaoH 2 P 2 8 is practically insoluble in water, and is practically undissociated. This reaction does not apply in the practical mixing of Cyanamid and acid phosphate. There is, however, a further reaction, that may take place with prejudicial results. (d) 2Ca 2 H 2 P 3 s + Heat — Ca s P 2 8 + CaH 4 P 2 0„ Citrate Sol. Cit. Insol. Water Sol. It has been found that with a constant quantity of lime, 92 CYANAMID — MANUFACTURE, CHEMISTRY AND USES above a certain minimum, the proportion of citrate insoluble phosphate formed is approximately a logarithmic function of the temperature. The quantity of Cyanamid that can be safely mixed with acid phosphate varies greatly with the nature of the acid phosphate, particularly its content of free acid and of iron and alumina. For some grades of acid phosphate it may be as much as 120 pounds of powdered Cyanamid, for the poor grades of acid phosphate as low as 70 pounds of pow- dered Cyanamid to 1,000 pounds acid phosphate in a ton of complete mixture. By the process of granulation, in which the powdered Cyanamid is formed into particles which pass through 15-mesh and over 50-mesh standard screens, the chemical activity of the Cyanamid with acid phosphate is greatly decreased. This is mainly due to the fact that the specific surface exposed by particles of different sizes varies inversely as their diameters. The number of particles per unit of weight varies inversely as the cubes of the diameters. One thousand particles one- hundredth of an inch in diameter, for instance, would be required to make one granule one-tenth of an inch in diameter, and the total surface exposed would be one-tenth as much as before granulation. Since chemical action can take place only on the exposed surface of the solid Cyanamid (the acid phos- phate having very little fluidity) it is evident that the localiza- tion in a few places of a comparatively large number of widely scattered small particles will greatly decrease the amount of action that can take place. Practically, it has been found that the chemical activity of the granulated Cyanamid now being manufactured is about one-half the activity of the powdered Cyanamid; hence, about twice as much granulated Cyanamid can be used in acid phosphate mixtures to produce the same effect as a given quantity of powdered Cyanamid. With improve- ments in the process of granulation the safe amount will be probably further increased. CYANAMID — MANUFACTURE, CHEMISTRY AND USES 93 OTHER MIXTURES. With other materials commonly used in fertilizer mixtures Cyanamid can be mixed in any quantities, without prejudicial effect on the valuable constituents. ADVANTAGES OF CYANAMID IN FERTILIZER MIXTURES. Drying Action. — The free acids in acid phosphate are fre- quently the cause of dampness and poor mechanical condition in mixed fertilizers, causing caking in the bags and making the fertilizer difficult of application through drills. To cor- rect this undesirable condition it is customary to add to the mixture various drying and neutralizing agents. Since the particles of Cyanamid are soft and porous and usually con- tain less than 1 per cent, moisture they readily absorb free moisture from the acid phosphate or other damp materials with which they come in contact. More important is the action of the lime on the free acids, calcium phosphates tak- ing the place of the sticky phosphoric acid, while the heat generated by the neutralization aids in dissipating the mois- ture uniformly throughout the mixture. This drying action is very valuable to the fertilizer compounder. Preventing Loss of Nitric Nitrogen. — It has long been known by fertilizer manufacturers, and has been demonstrated in the laboratory, 1 that when sodium or calcium nitrate is mixed with acid phosphate, without the further addition of neu- tralizing agents, there is a loss of nitrogen amounting to from 6 to 10 per cent, of the total nitrate nitrogen added. The loss is due to the action of the free acids in the acid phosphate upon the nitrate salts. Thus, with sodium nitrate the reaction probably is : 2NaN0 3 + H 3 P0 4 — Na.HPO, + 2HNO,. The nitric acid either volatilizes as such or is decomposed to nitrogen peroxide and oxygen and escapes from the mixture. This loss is prevented by Cyanamid in two ways ; the free 1 C. S. Cathcart, Jour. Ind. and Eng. Chein., Vol. 3, No. 1, 191 1. 94 CYANAMID — MANUFACTURE, CHEMISTRY AND USES phosphoric acid is neutralized by the lime of the Cyanamid, and again, the free nitric acid or nitrogen peroxide is neu- tralized by the Cyanamid lime immediately after its forma- tion. Whatever the mechanism, it has been shown by careful experiments that Cyanamid prevents this otherwise serious loss of nitrate nitrogen. Preventing Bag-rotting. — A similar loss of hydrochloric acid gas occurs when potassium chloride, or commercial muriate of potash, is mixed with acid phosphate : 2KCI + H 3 P0 4 — K,HP0 4 + 2HCI. This loss does not decrease the commercial value of the mixture, but the passage of the acid gases through the cloth of which the bag is made decomposes the bag fiber and causes so-called "bag-rotting." This destructive action is prevented by the addition of Cyanamid to the mixture, causing the neu- tralization of the hydrochloric acid gas, or the phosphoric acid producing it. To the fertilizer manufacturer, the drying and neutralizing properties of Cyanamid are decided advantages, since these are not possessed by any other high-grade mineral fertilizer, and no extra charge is made for them in the selling price of Cyanamid. Since the cost of drying and neutralizing agents and the extra mixing expense is saved if the nitrogenous ingredient possesses these properties, Cyanamid has been received with much favor by fertilizer manufacturers. Prac- tically the entire output of the American Cyanamid Company is sold in this way. CHAPTER XI. Permanganate Availability of Cyanamid. In order to have a ready means of determining the agricul- tural availability of the nitrogen in various organic compounds, certain chemical methods have been adopted that approxi- mately measure this property. The permanganate availability methods are in general use for this purpose. It is generally assumed that nitrogen compounds soluble in water are readily utilized as plant food, but it is also recognized that nitrogen compounds insoluble in water may be utilized by the plant in the course of growth. It seems to be generally true of organic nitrogenous compounds that the solubility in water, together with the relative ease with which the insoluble parts are de- composed by potassium permanganate bears a regular relation to the agricultural availability of the fertilizer. It is interest- ing to examine whether Cyanamid takes its proper place in the permanganate availability series of values as compared with its agricultural availability, and which of the permanganate methods gives the truest results. The following experiments on the solubility of Cyanamid nitrogen in water, and its behavior under the influence of potassium permanganate, were made under the direction of the author in October, 1912. The Cyanamid used was a low grade, granulated material analysing as follows : Nitrogen 13.58 per cent. Lime (CaO) 50.57 Moisture • 1 .83 " Carbon dioxide 4.00 " Size of granules 15 to 50 mesh EXPERIMENT I. Solubility on Filter. — Samples of 1 gram, 2 grams, 4 grams and 8 grams of granulated Cyanamid were placed on filter papers and washed with successive portions of distilled water at 25 C. until the volume of filtrate reached 250 cc. The g6 CYANAMID — MANUFACTURE, CHEMISTRY AND USES nitrogen content of each nitrate was determined with the fol- lowing results : Sample Grams of Grams of Per cent, of grams N. in sample N. in filtrate total N. in filtrate J O.1358 O.1227 90.4 2 0.2716 0.2357 86.8 4 0.5432 0.4729 87.1 S 1.0864 0.8x03 74.6 EXPERIMENT II. Solubility in Flasks. — Samples of 2, 4, 8, 17 and 32 grams of granulated Cyanamid were placed in Erlenmeyer flasks and each covered with 400 cc. of distilled water at 25 C. The flasks were stoppered, and allowed to stand 24 hours, with occasional shaking. They were filtered through dry niters without washing and nitrogen was determined in each filtrate, with the following results : Sample Grams of Grams of Percent, of grams N. in sample N. in filtrate total N. in fillrate 2 O.2716 O.2548 93.9 4 O.5432 O.5102 93.9 8 I.0864 I. OI 19 93.I 16 2.1728 2.0087 92.5 32 4-3456 3-9588 91. 1 EXPERIMENT HI. Rate of Solution in Flasks. — In each of five flasks was placed 2 grams of granulated Cyanamid and 250 cc. distilled water at 25 C. Each flask was shaken for 10 minutes continuously, after addition of the sample, and then only occasionally. After filtration without washing, nitrogen was determined in the filtrate. The following results were obtained : Gram of Gram of Per cent, of Time N. in sample N. in filtrate total N. dissolved 10 minutes 0.2716 0.2055 75-6 30 " 0.2716 0.2298 84.6 2 hours 0.2716 0.2403 88.5 6 " 0.2716 0.2433 89.6 24 " 0.2716 0.2480 91.3 Neutral Permanganate Method. — One of the permanganate availability methods formerly much used is the neutral CYANAMID — MANUFACTURE, CHEMISTRY AND USES 97 permanganate method described in Bureau of Chemistry, U. S. Department of Agriculture, Bulletin 107, page 10. In this method a sample of fertilizer containing about 0.075 grams of nitrogen is digested for 30 minutes on a water or steam bath with 125 cc. of potassium permanganate solution containing 2 grams of potassium permanganate. It is then diluted with 100 cc. cold water and filtered and washed until the total filtrate amounts to 400 cc. The nitrogen is determined in the residue ; the percentage of nitrogen removed is called the availability. To obtain the effect of the potassium permanganate this method was used, first, with 125 cc. of distilled water in place of the permanganate, and second, with the 125 cc. of perman- ganate solution. Per cent. Availability with water in place of permanganate 94-34 Availability with permanganate 87.54 Since the only difference in the above experiments was the absence of the 2 grams of potassium permanganate in the first run, it is evident that potassium permanganate has the effect of converting about 7 per cent, of the total nitrogen into in- soluble compounds. Alkaline Permanganate Method. — In this method the avail- ability is measured by the amount of ammonia that is formed and distilled from an alkaline permanganate solution. An amount of sample containing 0.045 grams of nitrogen is digested below the boiling point with 100 cc. of solution con- taining 15 grams of sodium hydroxide and 1.6 grams of potassium permanganate, for thirty minutes. It is then boiled and the distillate collected until 85 cc. is obtained. The per- centage of nitrogen distilled over as ammonia represents the availability. In order to learn the effect of each reagent a run was made by this method using, first, 100 cc. of distilled water in place of the alkaline permanganate solution; second, a run was made with 15 grams of sodium hydroxide in 100 cc. of solution, and a third run was made with both sodium hydroxide and potassium permanganate in 100 cc. solution. The results were as follows : 98 CYANAMID — MANUFACTURE, CHEMISTRY AND USES Per cent. Availability with water alone 13-79 Availability with water and sodium hydroxide 53-9° Availability with water and sodium hydroxide and potassium permanganate 4.75 This experiment shows that the nitrogen in Cyanamid is only slowly converted into ammonia by the action of boiling water alone, and that it is much more rapidly converted into ammonia in the presence of sodium hydroxide. By the action of potassium permanganate, however, the formation of ammonia is almost completely prevented, even in the presence of sodium hydroxide. Hence, in the above methods the addition of potassium per- manganate has the opposite effect from what was intended to be the function of potassium permanganate, namely to make insoluble compounds soluble and to convert complex com- pounds to the ammonia form. In the case of Cyanamid, the neutral permanganate method makes some water-soluble com- pounds insoluble, and the alkaline permanganate method practi- cally prevents the formation of any ammonia. The method which is lately coming into favor is the modified alkaline permanganate method adopted by the Agricultural Experiment Stations of New York, New Jersey and the New England States on March 4, 191 1. Modified Alkaline Permanganate Method. — This differs from the other methods in that an amount of sample equivalent to 0.050 grams of nitrogen is first washed on a filter with distilled water at room temperature until 250 cc. of filtrate is obtained. This is intended to remove all the water-soluble nitrogen. As a matter of fact, it removes about 87 per cent, out of a possible 94 per cent, of water soluble nitrogen in a low-grade Cyanamid, ■jv.d about 89 per cent, out of a possible 96 per cent, in a high- grade Cyanamid. The "insoluble" residue is digested for thirty minutes in a flask with 120 cc. of solution containing 2.5 grams potassium permanganate and 1.5 grams sodium hydroxide, and the ammonia is then distilled by boiling until 95 cc. of distillate is obtained. The sum of the percentage of water soluble nitro- CYANAMID — MANUFACTURE, CHEMISTRY AND USES 99 gen and of nitrogen in the distillate represents the availability. By this method the sample used in these experiments gave 90.20 per cent, availability. C. S. Cathcart, State Chemist at the New Jersey Agricultural Experiment Station, made some experiments with samples of powdered Cyanamid, using the regular modified alkaline per- mangate method, with the following results. Sample number 2S4 2S5 294 295 30S Per cent. Per cent. Per cent. Per cent. Per cent. Qualitative test for nitrates, none none none none none Total nitrogen. 15-76 1357 13-29 14.00 16.40 Nitrate and a mm o n i a c a 1 (Ulsch-Street) 6.98 5.53 3.50 4.72 7.32 Ammonia salts (magnesia) - - 0.92 0.57 0.45 0.55 0.91 Water soluble (total) 14-15 U-93 12.23 12.88 14-67 Water insoluble 1.25 1.64 1.06 1. 12 1.73 Active insoluble (distilled from alkaline permanga- nate) 0.17 0.17 0.25 0.32 0.33 Inactive insoluble 1.08 1.47 0.81 0.80 1.40 Total nitrogen as water solu- ble and active insoluble. 93.1 89. 2 93.4 94.3 91.5 It is interesting to note that as much as 40 per cent, of the Cyanamid nitrogen is converted to ammonia by the reducing action of the iron and sulphuric acid used in the Ulsch-Street method. 1 The amount of ammoniacal nitrogen originally pre- sent is shown by magnesia distillation to be from 3 to 6 per cent, of the total nitrogen. The qualitative test showed no nitrates present. The water-soluble nitrogen with one washing of 250 cc. distilled water is from 87 to 92 per cent, of the total, the average being 90.6 per cent. By treatment with alkaline per- manganate the available nitrogen is found to be 92.5 per cent. as an average of the five samples. In order to determine the effect of a more thorough initial washing, Cathcart repeated the availability experiments wash- 1 For Ulsch-Street Method see U. S. Dept. of Agr. Bureau of Chem., Bui. 107., or Wiley's Principles and Practice of Agricultural Analy- sis, Vol. 1, p. 445. 28 4 'er cent. 285 Per cent. 294 Per cent. 295 Per cent. 30S Per cent. 15-76 13-57 13-29 14.00 16.40 14.71 12.13 II.89 12.78 14.50 0.08 O.32 O.32 0.32 O.49 O.I2 O.I2 O.I2 0.08 0-33 14.91 12.57 12.32 13.18 15-32 0.14 O.22 O.23 0.22 0.31 0.71 O.78 0-73 0.60 0.77 IOO CYANAMID — MANUFACTURE, CHEMISTRY AND USES ing each sample three times with 250 cc. water each time. The following results were obtained : Sample number Total nitrogen Soluble nitrogen, 1st 250 cc. " " 2nd " . 3rd " . Total soluble nitrogen .... Active insoluble nitrogen. Inactive " " Total nitrogen as water sol- uble and active insoluble 95.5 94.3 94.5 95.7 95.3 It is seen that with this change in the procedure the water- soluble nitrogen averages 93.5 per cent, and the total available 95.1 per cent. The percentage of available nitrogen revealed by the modified alkaline permanganate method is practically a ques- tion of the solubility and the rate of solution of Cyanamid nitrogen in the initial washing with distilled water. The in- fluence of size of sample and of rate of solution is shown in the preliminary experiments on page 96. It is evident that to determine the true amount of water-soluble nitrogen in Cyanamid by the modified alkaline permanganate method a longer period of contact should be allowed between sample and solvent in the initial washing, or more solvent should be used. The simplest way would be to let the sample stand in a flask with distilled water for 24 hours and filter, or to agitate on a shaking machine for about three hours. Whether or not the availability determined by the perman- ganate methods corresponds with the fertilizer efficiency of Cyanamid is a question principally of determining what the fertilizing efficiency is, since the permanganate methods are easily carried out in the laboratory. The concensus of opinion seems to be that Cyanamid has about the fertilizing value of sulphate of ammonia, and this is about 95 per cent, of the efficiency of nitrate of soda, as an average of all kinds of conditions, favorable and unfavorable, that might occur in CYANAMID — MANUFACTURE, CHEMISTRY AND USES 101 agricultural practice. Both sulphate of ammonia and nitrate of soda, however, show an availability of ioo per cent, by the permanganate methods, while Cyanamid shows about 87 to 89 per cent, by the neutral permanganate method, 4 to 8 per cent, by the alkaline permanganate method, 90 to 94 per cent, by the modified alkaline permangante method, and 94 to 96 per cent, by simple solution in water for 24 hours. The neutral and the modified alkaline methods therefore approximate to a certain extent the values that they should represent, the straight alkaline method is wholly unsuitable, while the simple solution in water gives the most significant results. CHAPTER XII. Fire and Water Hazard of Cyanamid. The combustibility of Cyanamid and its susceptibility to damage by fire and water have been thoroughly investigated by the Underwriters' Laboratories of Chicago, 111. The fol- lowing results were obtained through the courtesy of Mr. A. H. Nuckolls, Chemical Engineer, of the Underwriters' Laboratories, and are a part of the report prepared for the information of fire insurance companies : "The object of the investigation was to determine the nature of recommendations to be made relative to issuance of an opinion upon the fire hazard of the product. This report does not deal with the hazards of mixtures of this product with other fertilizers." "Test for Flammable Gases. — Tests for flammable gases were conducted by placing about 5 pounds of the product in a large bottle, about 6 inches internal diameter by 16 inches in height, and adding an excess of water. The bottle was pro- vided with a loose fitting stopper to which wires were attached for producing an electric spark inside of the bottle. The spark was produced at intervals of about 15 minutes at the beginning of the test. The bottle was allowed to stand for 10 days, the spark being produced about every 3 to 4 hours except during the night. The test was repeated employing a gas testing flame instead of the electric spark and also varying the proportions of gas and air. "No analysis of the gas evolved was conducted. . . . Mixtures of air with gases evolved when test samples were treated with water did not ignite or burn when brought into contact with electric spark and gas flame." "Spontaneous Heating Tests. — Acceleration Test. — This test was conducted by means of an apparatus consisting essentially of a wire gauze cylinder about i J / 2 inches in diameter and 6 inches long, which is surrounded by a double- jacketed CYANAMID — MANUFACTURE, CHEMISTRY AND USES 103 copper water-bath provided with a tight fitting top or lid, a thermometer and inlet and outlet tubes to admit air. The sample was placed in the wire gauze cylinder, and the ther- mometer inserted so that its bulb was within the sample near its center. The temperature of the bath was maintained at ioo° C. for 4 weeks. For the first 6 hours of the test, tem- perature readings were taken every half hour. Afterwards, readings were taken twice daily until the test was concluded. "The thermometer showed that the internal temperature of the sample remained at approximately ioo° C. during the tests." "Test with Water. — About 10 pounds of the product were placed in a wooden cylinder, approximately 10 inches in height, and 10 inches internal diameter, the walls of the cylinder being about 1 inch in thickness. The temperature of the sample was allowed to become the same as that of the room, and then about 4 pounds of water, the temperature of which was observed, were added with stirring. The mixture was then allowed to stand and its temperature observed for a period of about a week. Test started at 10.30 A. M. Degrees C. Temperature of room during test, about 18 " " water at start 18 '• " test sample of product at start 17 " " mixture at 11.00 A. M., about 20 "No material rise in the temperature of the mixture was observed." "Acid Tests. — One pound samples of the product were treated with concentrated hydrochloric, sulphuric, and nitric acids and the results observed. "The acids reacted readily with the samples with consid- erable evolution of heat, compounds of these acids and lime being produced, and the Cyanamid (CaCN 2 ) was also attacked and decomposed. No combustion or explosive action took place." 104 CYANAMID — MANUFACTURE, CHEMISTRY AND USES "Behavior of Product when Heated. — Two 20-gram test samples were heated in a large porcelain dish by means of a Bunsen burner. The heat was gradually increased until the temperature of the samples was above a bright red heat. During the test a small gas-testing flame was constantly applied to the samples. "At the start oil vapors were given off but not in sufficient quantity to form a flame. The samples were decomposed but no material amount of combustion occurred." "Test with the Oil Used. — A sample of oil employed in the manufacture of Cyanamid was obtained directly from the manufacturer. Small samples of the oil were also obtained from the product by extraction with petroleum ether. "Specific Gravity. — Specific gravity was obtained roughly by means of a Be. hydrometer. The specific gravity was found to be approximately 30 Be. at 19 C. "Flashing Point. — The flashing point was determined with the Pensky-Martens tester, the standard method of test with this apparatus being followed. The flashing point was found to be 150 C. (221 F.) closed cup. "Evaporation. — An evaporation test was conducted by heat- ing about ]/ 2 gram of a sample of the soil, spread out on a watch-glass, for 5 hours at ioo° C. in an ordinary oven and determining the loss of weight of the sample. The loss by evaporation was found to be 1.1 per cent, by weight in 4 hours. "Spontaneous Heating. — This test was conducted by heating 14 grams of the oil, disseminated over 7 grams of cotton, at a temperature of ioo° C. for 48 hours in an apparatus con- sisting essentially of a wire gauze cylinder, about \ l / 2 inches in diameter and 6 inches long, surrounded by a double-jacketed copper water-bath provided with a tight fitting top, thermom- eter, inlet and outlet tubes to admit air. The oiled cotton was placed in the wire gauze cylinder, and the thermometer in- CYANAMID — MANUFACTURE, CHEMISTRY AND USES I05 serted so that its bulb was within and near the center of the oiled cotton. Observations were made to note if any differ- ence between the temperature of the sample and the water- bath occurred. "The internal temperature of the test sample remained slightly below ioo° C. during the first 5 hours of heating, and never exceeded ioo° C. the temperature of the surrounding bath." "General Behavior when Treated with Water. — A stream of water at about 75 pounds pressure from a l / 2 inch nozzle was applied to a bag for 15 minutes, the stream being directed so as to wet the entire external surface of the bag. The bag was then allowed to stand about a week, and an average sample was analyzed according to the method of Gunning. "The sample did not readily absorb water, owing to the presence of oil which retarded immediate contact of the water with the lime-nitrogen compound. Water was, however, gradually absorbed with a very slow evolution of gas in small quantity. A marked odor of ammonia was noted. When allowed to dry in air, the sample hardened to some extent, or in other words 'caked.' This 'caking' was in a measure due to absorption of carbon dioxide from the air. Per cent. Nitrogen in sample before wetting 1444 Nitrogen in sample after wetting 13. 10 Apparent loss of nitrogen 1 .34 The following conclusions were drawn with regard to the fire and water hazard of Cyanamid : "It is readily decomposed by high temperatures, and also by mineral acids which attack it somewhat violently with the evolution of considerable heat. Its decomposition by water is not accompanied by a material rise in temperature or the formation of hazardous products in dangerous quantity. It is not liable to spontaneous ignition. "The product is non-flammable, and is not combustible to 106 CYANAMID — MANUFACTURE, CHEMISTRY AND USES a material extent. The product is decomposed by high tem- peratures such as are produced in burning buildings. It will be noted that a relatively small amount of oil (4.2 per cent.) and carbon 13.25 per cent.) are present. The high tempera- ture to which the free carbon is subjected in the electric furnace renders it sufficiently graphitic to be difficulty com- bustible. "The product is susceptible to damage to a material extent by fire or water. The product does not readily take up water, and is not a good conductor of heat. In case of fire it will, therefore, probably be only partially damaged by the heat and water. "The product is considered non-hazardous except in respect to susceptibility to damage by fire and water." In the process of manufacture, the cans containing the crude calcium cyanamide are withdrawn from the nitrifying ovens at a temperature of more than i,ooo° C, and are allowed to cool in the open air, without noticeable injury to the calcium cyanamide. INDEX Absorption of cyanamide in soil, 39-42, 60. Acetic acid, action on cyana- mide, 12. Acetylene, 73. Acid fish, in Cyanamid fertilizer mixtures, 90. Acid phosphate, mixtures with Cyanamid, 91-94. Acids, action on cyanamide, 12, 13, 103, 104, 106. Acid soils, fertilizers on, 70, 74, 83. Activity of Cyanamid with potas- sium permanganate, 95-101. Addition compounds of cyana- mide, 13. Aeration, influence on cyanamide conversion, 47. Air, effect on cyanamide decom- position, 47. Alkaline permanganate method, 97-101. Aluminium hydroxide, effect on cyanamide decomposition, 52, 53, 54- American Cyanamid Co., capacity of factories, 3. Amidodicyanic acid, 15 ; identi- fication of, 23. Ammelide, 12. Ammeline, 12 ; identification, 23. Ammonia from Cyanamid, 8, 12 ; loss in storage, 24-31. Ammonia, loss of in fertilizer mix- tures, 90. Ammonium compounds, formation in cyanamide decomposition, 45, 46. Ammonium salts in Cyanamid fer- tilizer mixtures, 90. Ammonium sulphate, excessive ap- plications, 69 ; use in Cyanamid mixtures, 90. Analysis of typical Cyanamid, 8. Analysis— see analytical methods. Analytical methods : total nitro- gen, 19, 20 ; cyanamide, nitro- gen, 20-22 ; dicyandiamide nitro- gen, 20-22 ; amidodicyanic acid, 23 ; ammeline, 23. Application of excessive quantities of Cyanamid, 69-S4 ; normal quantities, 73, 87, 89. Ashby, 36. Aso, K, 77, 78. Availability of Cyanamid — perman- ganate methods, 95-101. Available phosphoric acid, in Cyanamid mixtures, 91-92. Bacteria — effect on decomposition of cyanamide, 32-36 ; not neces- sary in decomposition of cyana- mide to urea, 40, 43, 44, 45, 50, 56, 58, 59- Bags, storage of Cyanamid in, 25. Bag-rotting, prevention of, 94. Barium carbide, 2. Barium cyanamide, 2. Bases, action on cyanamide, 12, 13. Basic calcium cyanamide, 16. Bauxite, effect on cyanamide de- composition, 52, 53. Behrens, 36. Bineau, 10. Brioux, Ch. Decomposition pro- ducts in exposed Cyanamid, 29, 30 ; modified Caro method for analysis of cyanamide and di- cyandiamide, 21 ; pot tests, 77. Bun sen, 1. Calciocianamide, definition, 4. Calcium acid cyanamide, 14. ioS INDEX Calcium — effect on decomposition of cyanamide in soil, 33. Calcium carbide, analysis, 6 ; effect of in fertilizer, 73 ; manufacture of, 2, 4. Calcium Cyanamid, definition of, 4. Calcium cyanamide, definition of, 4 ; formation, 2 ; properties, 14 ; temperature of formation, 2 ; volatility, 6. See also Cyanamid. Calcium cyanamide carbonate, 16, 17, 38. Calcium cyanamide, definition, 4. See also calcium cyanamide and Cyanamid. Calcium hydroxide, effect on cyana- mide decomposition, 48. See al- so calcium, lime. Calcium nitrate, excessive appli- cations, 69. Carbide. See calcium carbide, ba- rium carbide. Carbon, effect on cyanamide de- composition, 50. Carbon dioxide, action on calcium cyanamide, 16 ; action in soil, 37, 38 ; effect on Cyanamid in storage, 24-28. Cannizzare, 10. Caro, Dr. Nicodem, 1, 2, 6, 11, 17; method of analysis, 20. Catalytic agents, in cyanamide de" composition, 42, 48-56, 5S. Cementing powders, 9. Cereal crops, 86. Chloroform — as sterilizing agent, 33. 57- Cladosporium, in decomposition of cyanamide, 34-36. Climate, effect on Cyanamid in storage, 24-31. Cloez, 10. Colloids — effect on cyanamide de- composition, 48-59. Commercial Cyanamid. See Cyana- mid. Commercial derivatives, 8. Complete fertilizer mixtures, 89-94. Conversion of available phosphoric acid in Cyanamid mixtures, 91-92. Copper oxide process, 5. Concentration of cyanamide, effect on decomposition, 40, 42, 46, 47. Cyanamid: Agricultural use, 83-89; analysis, 7, S ; analytical meth- ods, 19-22 ; availability, 95-101 ; decomposition in soil, 32-59; de- finition of term, 4 ; derivatives, S-18 ; development of industry, 1-8; excessive applications, 69; fertilizer mixtures, 90-94 ; fire and water hazard, 102-106; manu- facture, 4-7 ; nitrification, 62-64 \ retention in soil, 60-61 ; solu- bility, 95-96; storage, 24-31; toxicity, 65-82. See also cyana- mide. Cyanamide: Action of acids, 12; alkalies, 12; heat, 11; oxidizing and reducing agents, 13, 95-101 ; analysis of, 19-21 ; decomposition in soil, 32-59 ; definition of term, 4; derivatives, 13-17; discovery, 10; properties, 11. See also Cyanamid. Cyanides : Absent in Cyanamid, 2, 8 ; manufacture, 8 ; part in de- velopment of Cyanamid indus- try, 1. Cyanuric acid, 12. Decomposition of Cyanamid in soil, 32-59 ; effect of — aeration, 47 ; aluminum hydroxide, 52-54 ; bauxite, 52-53 ; colloids, 48-59 ; concentration of solution, 40, carbon, 50; electrolytes, 48; glass sand, 52-54 ; heat, 43 ; iron oxide, 52-54, 56; iron hydrox- ide, 54, 55 ; kaolin, 52-53 ; silicic acid, 54 ; soil, 32-49 ; sterile soil, 44. 5°. 56; umber, 52 ; tempera- ture, 43 ; zeolites, 49; products formed, 43-45, 51 ; stages in, 37, 38, 57- INDEX IO9 Decomposition of Cyanamid in stor- age, 28, 29. Definitions of terms used in Cyan- amid industry, 3-4. Derivatives of Cyanamid, 8-18. Di-calcium phosphate in Cyanamid mixtures, 91-92. Dicyaudiamide ; commercial pro- duction, 9; conversion in soil, 77; decomposition, 75, 76; formation in Cyanamid, n, 43,44, 51, 75; method of treating subject, 74; properties, 17, 18; pure versus impure, 77-82 ; toxicity, 77-82. Dicyandiamidine, analysis, 21 ; properties, iS. Dimetal salts of cyanamide, 13. Discovery of Cyanamid, 1. Drying action of Cyanamid in fer- tilizer mixtures, 93. Duration of Cyanamid nitrogen in soil, 64. Dye industry, use of/licyandiamide in, 9. Efficiency of utilization of nitrogen in fertilizers, 69, 84. Electric furnace, 1, 4. Electrolytes, effect on cyanamide decomposition, 47. Equilibrium, temperature, 6 ; pres- sure, 6. Errors in fertilizer experiments, 84, 85- Excessive applications, effect of, 69, 72, 82, 84. Experimenting with fertilizers, 69, 83-86. Explosives, Cyanamid derivatives for use in, 9. Exposure of Cyanamid, effect of, 25-31- Factory storage of Cyanamid, 24. Ferrodur, 9. Fertilizer : excessive application of, 69-73, 84 ; mixtures with Cyana- mid, 89-94; preparation of Cyana- mid as material for, 7 ; use of Cyanamid as, 73, 87, 89. Fineness of Cyanamid, 7. Fire and water hazard of Cyanamid, 102-106. First stage of decomposition of cal- cium cyanamide, 37, 38. Florida, storage test in, 24, 31. Frank, Dr. Albert R., 3, 85. Frank, Prof. Adolph, 1. Freudenberg, Herman, 3. Fungi —in decomposition of cyana- mide, 35, 36. Germination, effect of Cyanamid on, 82. Glass sand, effect on cyanamide decomposition, 52, 53, 54. Glucose — effect in decomposition of cyanamide, 34-36. Granulated Cyanamid, 7 ; activity compared with that of powdered Cyanamid, 92, availability of, 96-99; solubility of, 95-96. Guanidine, 9. Gunning method in Cyanamid an- alysis, 19. Hall, A. D., 60. Haloid acids, 12. Hardening powders, 9. Haselhoff, E., 73. Hazard, fire and water, of Cyana- mid, 102-106. Headden, 72. Heat, effect of on Cyanamid, 102- 106. Heat, effect on conversion of dical- cium to tricalcium phosphate 91, 92. Heating soil, effect on cyanamide decomposition, 49. Henschel, G., 11, 22 — decomposi- tion products in exposed Cyana- mid, 30, 31. no INDEX History of Cyanamid industry, I. Hutchinson, 61. Hydrogen, effect on cyanamide conversion, 47. Hydrogen sulphide, action on cyan- amide, 12. Hydrolysis of cyanamide salts, 14. Increase in weight during storage, 24-31. §5- Intensit, 9. Inouye, R., 77, 78. Iron hydroxide, effect on cyana- mide decomposition, 54, 55. Iron ore, effect on cyanamide de- composition, 52, 53, 54. Iron oxide, effect on cyanamide de- composition, 52, 53. Jacksonville, Fla., storage test at, 24, 3i- Jacob}', 10. Kalkstickstoff, definition, 4. Kaolin, effect on cyanamide de- composition. 52, 53. Kappen, H., 32 ; experiments with soil, 34 ; experiments with col- loidal substances, 51-59; effect of acetylene, 73; value of dicyandia- mide, 77. Kjeldahl method, suitable for Cyanamid nitrogen determina- tion, 19. Kloppel, J., 86. Large applications of fertilizer, 69, 72. Laterite earth, effect on cyanamide decomposition, 52, 53. Liberi, G., 76. Lime, action on cyanamide, 13, 36. See also Calcium, calcium hy- droxide. Lime-nitrogen, definition, 3. Liquid air, source of nitrogen, 5. Lohnis, 77. Manganese dioxide, effect on cyan- amide decomposition, 52, 53. Manganese hydroxide, effect on cyanamide decomposition, 54. Mehner, Prof. H., 1. Melamine, 12, 15. Mellon, 12. Metallurgy, use of Cyanamid in, 9. Methylamine from cyanamide, 13. Miller, N. H. J., 61. Milo, C. J., 77, So, 81. Mixed fertilizers, Cyanamid in, 89-94. Modified alkaline, permanganate method, 98-101. Moissan, 1. Moisture, effect on Cyanamid in storage, 24-31. Moor soils, fertilizers on, 70, 74. Miintz, 63, 86, Mustard, destruction with lime- nitrogen in oat fields, 86. Neutralizing properties of Cyana- mid, 91-94. Neutral permanganate method, 96- 101. Niagara Falls, Ontario, storage test at, 25-27. Nitrate nitrogen — preventing loss by use of Cyanamid, 93. Nitrates, effect on analysis of Cyan- amid, 19 ; effect on cyanamide decomposition, 48. Nitric acid, action on cyanamide, 12 ; effect on cyanamide decom- position, 48; manufacture from lime-nitrogen, 8 ; preventing loss of in fertilizer mixtures, 93, 94. Nitrification, in acid soils, 83 ; of Cyanamid compared with am- monium sulphate, dried blood, etc., 62-64. Nitrites, action on cyanamide, 13. Nutritive substances, effect of pres- ence in cyanamide decomposi- tion, 32-36, Si. INDEX I I I Nitrogen, analysis of in Cyanamid, 19, 20 ; duration of Cyanamid in soil, 64 ; excessive applications of, 69-73; fixation of as Cyanamid, 1-8 ; prevention of loss as nitrate nitrogen, 93. Nitro-guanidine, 9. Nitrolim, definition, 4. Nomenclature, 3. Nottin, 63, 86. Nuckolls, A. H., 102. Oat-fields- destruction of wild mus- tard in, 86. Oats, excessive applications of ni- trogen on, 69. Oil in Cyanamid, 7, 104. Old Cyanamid, compounds in, 28. Ostwald Process, 8. Oxidizing agents, action on cyana- mide, 13. Patents, Cyanamide, 3. Penicillum brevicaule, in decom- position of cyanamide, 35, 36. Permanganate ; potassium — effect on Cyanamid, 95-101. Perotti, 77. Phosphates -mixtures with Cyana- mid, 91-94. Phosphoric acid, action on cyana- mide, 12. Play fair, I. Poison, definition of, 65. Potassium hydroxide, effect on cyanamide decomposition, 48. See also alkalies. Potassium permanganate, effect on Cyanamid, 95-101. Power consumption, in Cyanamid manufacture, 7. Preparation of cyanamide, 10. Pressure of nitrogen in Cyanamid formation, 6. Properties of cyanamide, 10-18. Pure substances and toxicity, 80. Quantity of Cyanamid to apply as fertilizer, 88. Rate of removal of cyanamide from soil solution, 39. Reducing agents, action on cyana- mide, 13, 99. Reis, 36. Retention of Cyanamid nitrogen in soil, 60. Reversion in acid phosphate — Cyanamid mixtures, 91. Root crops, 86. Rothe, F., 2. Sabaschnikoff, 77, 80. Sackett, 72. Sand, effect on cyanamide decom- position, 52, 53. Schiick, 10. Schneidewind, 86. Second and third stages of Cyana- mid decomposition in soil 38. "Secondary products," effect on cyanamide decomposition, 33, 34, 81. Sidgwick, 11. Siemens & Halske, 1. Silicates, effect on cyanamide de- composition, 49, 50. Silicic acid, effect on cyanamide decomposition, 54. Silver cyanamide, 17. Sodium acid cyanamide, 13. Sodium cyanamide, 10, 13. Sodium nitrate, excessive applica- tions, 69. Soil, decomposition of Cyanamid in- 3 2 -59- Soil solution, rate of removal of cyanamide from, 39. Sol, iron oxide, effect on cyana- mide decomposition, 56. Solubility of Cyanamid, 95-101. Solution of cyanamide, changes in, 14, 15, 16, 76; rate of solution of Cyanamid, 96. Steglich, S6. 112 INDEX Sterile conditions and cyanamide decomposition, 33, 40, 43, 44, 50, 51, 56, 57- Sterilization of soil, effect on cyana- mide decomposition, 44, 50, 56, 57- Stickstoffkalk, definition, 4. Storage of Cyanamid, variation of nitrogen during, 24-31. Strohmer, 85. Stutzer, 36. Substitution compounds of cyana- mide, 13. Sugar beets, 85, 86. Sulphuric acid, action on cyana- mide, 12. Summary on cyanamide decom- position in soil, 57-59. Surrogate, 8. Temperature, effect on cyanamid decomposition in soil, 43, 44 ; re- action temperature, barium cy- anamide, 2 ; calcium cyanamide, 2, 6. Tempering powders, 9. Thio-urea, 12. Top-dressing, use of Cyanamid as, 87. Toxicity : of cyanamide, 34-36 ; of fertilizers, 65-82. Tri-calcium phosphate in Cyanamid mixtures, 91, 92. Tricyantriamide, 12. Ulpiani, C, chemistry of cyana- mide, 12, 14, 16, 22, 23; decom- position of Cyanamid in soil, 3 2_ 5 r > 57> 59; dicyandiamide, 34, 77- Umber, effect on cyanamide decom- position, 52, 53. Underwriters' Laboratories, 102-106. Urea, assimilation of, 60 ; deter- mination of, 22 ; formation from cyanamide, 12, 15, 37, 43, 44, 51, 89 ; manufacture, 9 ; transforma- tion by bacteria, 40, 44, 57. Volatility of calcium cyanamide, 6. Water : Effect on Cyanamid in storage, 24-31 ; hazard of in fires, 103, 105, 106 ; hydrolysis of cyanamide salts in, 14 ; solu- bility of Cyanamid, 95-101. Weeds, destruction with lime-ni- trogen, 86, 87. Weight, increase during storage of Cyanamid, 24-31, 85. Wheat, 86. Willson, 1. Zeolites, effect on cyanamide de- composition, 49, 50. SCIENTIFIC BOOKS PUBLISHED BY THE CHEMICAL PUBLISHING CO., EASTON, PA. ARNOLD— The Motor and the Dynamo. 8vo. Pages VI + 178. 166 Figures , $1-5° BENEDICT— Elementary Organic Analysis. Small 8vo. Pages VI + 82. 15 Illustrations $1.00 BERGEY— Handbook of Practical Hygiene. Small 8vo. Pages 164.. $1.50 BILTZ — The Practical Methods of Determining Molecular Weights. (Translated by Jones). Small 8vo. 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