BUKEAU OF SOILS. 295 



this department has been continued, more especially with the Fixed 

 Nitrogen Research Laboratory. The several investigations which 

 have to do with concentrated fertilizers, nitrogen, phosphoric acid, 

 and potash will be discussed under appropriate heads. The bureau 

 has more fully equipped its laboratories and buildings at Arlington 

 Experimental Farm, and is now prepared both with facilities and 

 men to do research work on a semifactory scale. 



CONCENTRATED FERTILIZERS. 



Attention has been directed in previous reports to new develop- 

 ments in the fertilizer industry which call for the preparation of 

 fertilizer mixtures of higher concentration than those formerly used. 

 The Haber and other processes for fixing nitrogen and the volatili- 

 zation method of preparing phosphoric acid from run-of-mine phos- 

 phates all yield materials as finished products of different composi- 

 tion and higher concentration than those ordinarily used in the 

 manufacture of fertilizers. - The study of concentrated fertilizers 

 and fertilizer materials was therefore undertaken, not only as a neces- 

 sary step in the development of new sources of fertilizers, but also 

 with a view to reducing the cost of fertilizers by bringing about a 

 decrease in the cost of handling and transportation. 



The ammonia recovered in the fixing of nitrogen is not suited for 

 direct use in fertilizers, but when this is neutralized with phosphoric 

 acid a product is obtained which contains two of the three essential 

 constituents of fertilizers and of such concentration that the content 

 of both amounts to a total of 74 per cent, or four times the con- 

 centration of the average fertilizer. 



By modifying the process so as to include the use of commercial 

 potassium chloride as well as phosphoric acid and ammonia, it has 

 been found that a product of corresponding concentration may easily 

 be obtained which contains all three of the essential constituents of 

 fertilizers. The chemical and physical properties of this material, 

 which consists of a mixture of ammonium and potassium phosphate, 

 makes it admirably suited as a medium for transporting the fertiliz- 

 ing elements or for increasing the concentration of other fertilizer 

 mixtures. 



Since phosphoric acid is required in the preparation of these mate- 

 rials, it follows that the commercial possibilities in the preparation 

 of concentrated fertilizers depends on the cost of producing phos- 

 phoric acid. The methods that have been devised by the bureau for 

 the preparation of this acid yield a product of most suitable con- 

 centration for the production of concentrated fertilizers, and steps 

 are now being taken by outside concerns to test out the possibilities 

 of the processes outlined in this and other reports. Samples of mate- 

 rials already produced, together with a number that have been pre- 

 pared by the Bureau of Soils, were exhibited at the congressional 

 hearings on the Muscle Shoals propositions and attracted much 

 attention. 



Considerable difficulty was at first experienced in the course of this 

 work, owing to a lack of suitable methods of analysis. It was found 

 possible, however, to devise simple and accurate methods of special 

 application to the materials proposed for concentrated fertilizers and 

 a description of the methods has been given to the scientific press. 



25684— AGR 1923 20 



