I-\;DUSTRIAL A N D EhTGINEERINGCHEMISTRY
January, 1931
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Recent Developments in the Preparation and Use of Fertilizers' William H. Ross FERTILIZER A N D FIXEDN I T R O G B N
Ammoniated Superphosphates
INVESTIGATIOIS,
BUREAUO?
SOILS,
WASHINGTON,
D.
c.
A review is given of certain new and improved methods for the preparation of fertilizer materials and mixtures. The granulation of fertilizer mixtures is discussed as a means of reducing caking, preventing segregation, and greatly improving the drillability of the mixture. The efficiency of fertilizers as affected by their drillability and placement in the soil with respect to the seed is also discussed, together with the cause and prevention of the apparent toxic action of certain synthetic fertilizer mixtures which consist chiefly of alkali salts.
H E most interesting of the recent developments in the fertilizer industry is the ammoniation of superphosphates. The absorption of a m m o n i a by superphosphate is not a new discovery, but it is only recently that the cheap production of synthetic ammonia makes its direct use in fertilizer mixtures containing superphosphate an economic possibility. The chemistry of the reactions involved in the absorption of ammonia by superphosphates has been studied by Jacob, Hill, Ross, and Rader (6) of the Bureau of Chemistry and Soils and by Keenen (7) of the Du Pont Ammonia Corporation. The work of these investigators shows that a superphosphate that has been treated with ammonia contains ammonium sulfate, monoammonium phosphate, such iron and aluminum phosphates and undecomposed rock as may be present in the original superphosphate, and one or more of the phosphates of calcium. Thus, an ammoniated superphosphate having 2 per cent of ammonia uniformly absorbed throughout the entire mass will contain mono- and dicalcium phosphates but little or no tricalcium phosphate; one having 4 per cent of ammonia will contain di- and tricalcium phosphates with little or no monocalcium phosphate; and one having the maximum of about 6 per cent of ammonia will consist largely of tricalcium phosphate with possibly some calcium hydroxyphosphate but little or no mono- and dicalcium phosphates. The solubility of an ammoniated superphosphate in the official ammonium citrate solution decreases but little, as its composition would indicate, up to an absorption of about 2 per cent of ammonia, but the solubility gradually decreases with increase in ammonia content up to the maximum possible absorption of 6 per cent when the citrate-insoluble phosphoric acid may approach or even exceed 6 per cent. Howes and Jacobs ( 5 ) have shown that the values obtained for the citrate-insoluble phosphoric acid in highly ammoniated superphosphates vary greatly with the weight of the sample taken for analysis, the acidity of the ammonium citrate solution, and the time of digestion. The change in solubility with the weight of the sample taken for analysis is of special significance in this determination. Thus, the value obtained for the citrate-insoluble phosphoric acid in a highly ammoniated superphosphate may be decreased to less than one-half by the simple variation in the method of analysis of reducing the weight of the sample from 2 grams to 1 gram. Reducing the weight of the sample from 2 grams to 1 gram, or even to 0.5 gram, has no significant effect, however, on the citrateinsoluble phosphoric acid in superphosphates that have not been ammoniated or otherwise reverted. The average mixed fertilizer contains about 50 per cent of superphosphate and the quantity of this material in a 2-gram
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CHEMISTRY A N D
1 Received September 22, 1930. Presented before t h e Division of Fertilizer Chemistry a t t h e 80th Meeting of the American Chemical Society, Cincinnati, Ohio, September 8 to 12, 1930.
sample of such a mixture will be only 1 gram. When the phosphoric acid is supplied in the form of an amm o n i a t e d superphosphate, analysis of a mixed fertilizer will show a lower ratio of c i t r a t e - i n s o l u b l e to total phosphoric acid than that found in the o r i g i n a l amm o n i a t ed superphosphate, and the ratio will change in proportion as the ammoniated superphosphate in the mixture is changed. The method is therefore an unsatisfactory one as applied to this type of material. Vegetative tests (8) made a t several of the state agricultural experiment stations during the past season indicate that the citrate-insoluble phosphoric acid in ammoniated superphosphates, as determined by the official method, has a true availability of about 75 as compared with 100 for monocalcium phosphate. This is in agreement with the known availability of other materials of similar solubility and composition. It would thus seem that the present official method for measuring the availability of phosphates not only gives varying results with the proportion of ammoniated superphosphate in a fertilizer mixture, but also gives values in the analysis of such materials which are not in good agreement with vegetative tests. It has, therefore, been proposed to change the official method so that it ~wllcorrectly evaluate, not only superphosphates, but also their ammoniated products and other materials of similar composition. A collaborative study of the problem is now in progress. Preparation of Ammonium Phosphates
The use of ammonia in the preparation of soluble salts such as the ammonium phosphates has also received considerable attention during the past few years. The process most extensively used in this country for the preparation of crude monoammonium phosphate is a very simple one and consists in first treating phosphate rock with sulfuric acid, then neutralizing the acid with ammonia in open vessels and evaporating the resulting slurry to dryness in a rotary kiln. I n a process recently developed in England (4) somewhat less than one-third of the sulfuric acid used in treating the rock is replaced by ammonium sulfate, so as to obtain a solution of monoammonium phosphate in sulfuric acid. Thc reaction taking place when the rock is treated with one equivalent of ammonium sulfate to two of sulfuric acid may Le represented as follows: Caa(PO& ("&SO4 2HzSO4 = 3CaS04 ~ S L L H Z P O ~ The solution is filtered from the calcium sulfate sludge and treated with ammonia to neutralize the free acid present. The precipitate of iron and aluminum phosphates that settles out is filtered off and the filtrate is concentrated to crystallize out monoammonium phosphate or a mixture of this salt with ammonium sulfate. The proportions of these two salts in the mixture may be varied a t will by changing the quantities of the reagents used in treating the rock. The precipitated iron and aluminum phosphates are dis-
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posed of as a fertilizer material, while the calcium sulfate sludge is made into a slurry and treated with ammonia and carbon dioxide to form calcium carbonate and ammonium sulfate, which is re-used in the process. The precipitated calcium carbonate is used in preparing Nitro-Chalk and for other purposes. New processes, in addition to those outlined in a recent paper by Ross, Mew, and Jacob (9), have recently been developed in this country and abroad for the commercial preparation of diammonium phosphate, but information on the subject is held confidential pending the outcome of certain patent applications which relate to these processes.
the treatments so far proposed consists in mixing about 1 part of precipitated calcium carbonate, or powdered limestone, with 2 parts of a hot saturated solution of the salt and spraying the mixture into a granulating chamber. The product prepared by this method in Germany is known as Tal-Nitro” or “Kalkammonsalpeter ;” that prepared in England is known as “Nitro-Chalk;” while the American product is called “Ammonium Nitrate-Limestone.” The German product is colored green to simplify identification. Different grades of Nitrophoska intended for shipment to oriental countries are colored black, blue, red, green, and brown. The practice of giving a distinctive color to certain grades of well-known products seems to be a popular one and New Methods for Preparation of Potassium Nitrate is likely to be extended in the fertilizer industry as new mixThe low cost of synthetic ammonia has led to a correspond- tures come on the market. ing reduction in the cost of ammonia oxidation products such Ammonium nitrate dissolves in about one-fourth its weight as nitrogen peroxide and nitric acid. Much attention has of anhydrous ammonia at 35” C. to give a clear solution havaccordingly been given of late to the production of potassium ing an ammonia vapor pressure of 1.6 atmospheres. The nitrate by treating potassium chloride with nitrogen peroxide vapor pressure of anhydrous ammonia of the same temperaor nitric acid rather than by double decomposition with ture is 13 atmospheres. Anhydrous ammonia has certain sodium nitrate. advantages over aqueous ammonia in the ammoniation of I n a process developed by Thorssell and Kristensson (IO), superphosphates, but the risk attending its storage is much of the Kali-Industrie Aktiengesellschaft, potassium chloride greater. . A solution of ammonium nitrate in ammonia has is dissolved in an equivalent quantity of 35 per cent nitric therefore been proposed as a substitute for anhydrous amacid at 40” C. and the solution is then cooled to -10” C. or monia in the ammoniation of superphosphates. Although below to crystallize out potassium nitrate. The mother the vapor pressure of anhydrous ammonia can be greatly reliquor is heated to 80-70” C. and treated with an appropriate duced by the addition of ammonium nitrate, it cannot be quantity of ferrous chloride to reduce the nitric acid in solu- reduced in this way below atmospheric pressure a t normal tion to nitric oxide: temperatures, and storage under pressure is still necessary if rapid loss of ammonia is to be avoided. HNOt 3FeC12 3HC1 = NO 3FeCla 2H20 Complete Fertilizer Mixtures The solution is heated to boiling by the direct action of steam to expel the nitric oxide, which is recovered for reconversion A number of processes have recently been developed for into nitric acid. The ferric chloride in the residual liquor is the preparation of complete fertilizer mixtures which do not reduced with iron turnings to ferrous chloride and re-used involve a separate preparation of any of the components of in the process. I n one of these processes (1) phosphate rock I n a modification (11) of this process the mother liquor the mixture, is decomposed with a mixture of potassium sulfate and nitric obtained on crystallizing out the potassium nitrate is neutralacid in suitable proportions to form calcium sulfate, potassium ized with ammonia and concentrated to recover ammonium nitrate and free phosphoric acid as represented in the equation: chloride. This process does not seem to offer much promise where the market for both products is limited to the fertilizer Caa(P0,)I 3K~S04 6HNOs = 3CaSO,+ 6KNOs 2H&’O4 industry, but it should prove economical in those localities The concentration of the nitric acid used in the reaction where the ammonium chloride can command a price in exshould be such that the potassium nitrate formed will remain cess of its fertilizer value. in solution, The insoluble residue, which includes the calWhat appears to be the most promising of the methods cium sulfate formed in the reaction, is filtered off and washed, proposed for the preparation of potassium nitrate is one d e and the filtrate is treated with ammonia to give a thick slurry veloped by Whittaker and Lundstrom of the Bureau of Chemof 3 mols of potassium nitrate to 1 of monoammonium phosistry and Soils. The first step in the process consists simply phate. The slurry may be evaporated to dryness or, preferin passing nitrogen peroxide through a column of solid poably, spray-dried as practiced in the study that is now being tassium chloride. The reaction is represented as follows: made of this process in the Fertilizer and Fixed Nitrogen KC1 2N01= KNOs NOCl Laboratory of the Bureau of Chemistry and Soils. The nitrogen of the nitrosyl chloride formed in the reaction Granulation of Fertilizer Mixtures may be changed into nitric oxide for re-use in the process by The granulation of fertilizers is another important recent thermal decomposition, catalytic oxidation, or reaction with various products such aa metallic iron or other treatment. development in the fertilizer industry. A study of this subThe process does not involve the use of a solution in any step ject was first undertaken in the Fertilizer Laboratory of the and the corrosion of the apparatus is thereby greatly reduced. Bureau of Soils about seven years ago. This work, which was first limited to the treatment of fusible materials such Treatment of Ammonium Nitrate as urea, has since been extended to the granulation of comInasmuch as ammonia and nitric acid are the cheapest plete fertilizer mixtures. Easily fusible materials can be forms of ammoniacal and nitrate nitrogen, respectively, the granulated most conveniently by spraying a melt of the cost of preparing ammonium nitrate, the product formed by material into a cooling tower. Most fertilizer materials the simple combination of these two materials, should be less and mixtures, however, cannot be fused without decomposithan for any other material or mixture containing these two tion, and the most successful methods for granulating prodforms of nitrogen. The hygroscopicity of this material, ucts of this kind involve a dehydration of the moistened however, is a serious handicap to its use in fertilizers, and no material by graining, rotary drying, or by allowing it to fall treatment has yet been devised which will give a drillable in a dispersed condition in a drying tower. Processed ferproduct under humid conditions. The most successful of tilizer materials are ordinarily dried before being placed on
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the market, and if they are produced a t the same plant in which they are made into mixtures no addition of water for the granulating treatment should be necessary. Dehydration by spraying and by rotary drying are claimed to be the cheapest methods of drying, and if this is so, then the granulation of fertilizer mixtures under these conditions should add little if anything to the cost of their manufacture. The granulation of fertilizer mixtures prevents segregation, improves their drillability, and greatly reduces their tendency to cake or become sticky. The extent to which mixed fertilizers segregate increases with the difference in the size and specific gravity of the individual particles. Fertilizer mixtures that have not been granulated may therefore segregate differently according to the materials used in the mixture. A powdered fertilizer is not so drillable as a granular one, and the uniformity with which it can be distributed is likely to change much more rapidly from day to day with changes in relative humidity.
The efficiency of certain synthetic mixtures that have recently been placed on the market has frequently been too low to be explained by irregular distribution or the placement of the fertilizer. The poor results were always obtained on sandy soils and were limited to mixtures containing alkali salts only. A careful investigation of the subject by the Office of Tobacco and Plant Nutrition, Bureau of Plant Industry (S), has demonstrated that the poor results obtained with fertilizers of this kind are due to an inadequate supply of calcium to counteract the toxic action of the alkali salts and to a deficiency of both calcium and magnesium below the normal requirements of the plants. When these were supplied, normal crop yields were invariably obtained. The addition of certain other elements now known to be essential to crops, such as manganese and sulfur, has also been found to increase the effectiveness of synthetic fertilizer mixtures when used in soils deficient in these elements. The efficiency of fertilizers may thus be increased by (1)increasing the uniformity with which they are distributed in Factors Affecting Efficiency of Fertilizers the field; (2) adjusting the position of the fertilizer in the That the uniform distribution of the plant-food constitu- soil with respect to the seed, so as to secure the optimum ents of a fertilizer is essential for best crop yields was clearly balance between its burning effects and its availability to demonstrated in a recent cooperative inrestigation by the the roots of the plant; and (3) improving the quality of the Fertilizer and Fixed Kitrogen Unit of the Bureau of Chemistry fertilizer by supplying suitable proportions of all necessary and Soils, the Division of Agricultural Engineering, Bureau ingredients. of Public Roads, the South -Carolina Experiment Station, The many changes which are now taking place in the ferand a Joint Committee on Fertilizer Application appointed tilizer industry make the most effective use of fertilizers a by a number of fertilizer and agricultural agencies ( 2 ) . matter of special importance a t this time, and it is possible These experiments were made with cotton during the sum- that further investigations in this field may bring about mer of 1929. Plantings were made in which a 4-84 and greater economic savings in the use of fertilizers than is likely a 12-24-12 fertilizer were applied by twenty-two different to result from further reductions in manufacturing costs. types of commercial distributors and also in a uniform manner Literature Cited by hand. All the distributors applied the fertilizer more or less irregularly along the row. When other conditions were Chemieverfahren Gesellschaft, British Patent 302,148 (1927). equal, the uniformly distributed fertilizer produced from 20 Cumings, Mehring, and Sachs, Agr. Eng., 11, 149-60 (1930). Garner, McMurtrey, and Bowling, J . Agr. Research, 40,145-68 (1930). to 50 per cent more cotton than that applied on an average Gordon, British Patent 316,428 (1928). by the machines in each of six tests and the more irregular Howes and Jacobs, IND. ENG.CHEM.,Anal. Ed., in press. the distribution the lower were the yields. Jacob, Hill, Ross, and Rader, IND. END. CHBM.,22, 1385 (1930). These and field tests by others have shown that the efKeenen, I b i d . . 22, 1378 (1930). Ross and Jacob, Report presented a t the 46th Annual Convention, fectiveness of a fertilizer also depends on its position with A. 0. A. C., Oct. 20, 1930. respect to the seed. The results indicate that it should be Ross, Merz, and Jacob, IND. ENG.CHEM.,21, 286-9 (1929). more or less localized rather than being widely distributed Thorssell and Kristenson, British Patent 287,133 (1927). through the soil and that it should be placed within a certain U. S. Dept. Com., World Trade Notes on Chemicals and Allied Prodmaximum distance from the seed but not in contact with it. ucts, 3, No. 49, 3 (1QP9).
Effect of Sunlight on Ephedrine Solutions' Edmond E. Moore and Marjorie B. Moore SWAN-MYERS COMPANY, INDIANAPOLIS, IXD,
Solutions of ephedrine alkaloid were found to be apparently stable for yeam if H E stability of soluunstable in sunlight. Oxygen is necessary for this left in the original package, tions of ephedrine salts has been pointed out decomposition. Benzal-ephedrine is one of the chief but occasionally they +cornby Chen and Schmidt (2) and decomposition Products of the aqueous solution. pose after they have been in other investigators. This is Ephedrine carbonate has been isolated and its Properthe possession of the patient the probable cause of the reties determined. for some time. This decompeated appearance, in articles p o s i t i o n is indicated by a and reviews on ephedrine, of the statement that solutions slight turbidity and an unpleasant odor. of ephedrine are stable toward air, heat, and light. An investigation was undertaken to determine the cause During the past few years solutions of ephedrine alkaloid of this decomposition, the products formed, and possible in mineral oil, oil-water emulsions, or water have become protective agents. Natural sunlight was used in this inrather widely used in medicinal work. These solutions are vestigation because of its importance from a practical point of view. 1 Received September 16, 1930. Presented before the Division of Medicinal Chemistry a t the 80th Meeting of the American Chemical soSamples of 1Per cent aqueous SOhtiOnS Of ephedrine alkaloid were exposed under a variety of conditions-in transparent ciety, Cincinnati, Ohio, September S t o 12, 1930.
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