290 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



sorbents has been constructed, and a sliidj' of them is now being 

 carried on with tlie use of this apparatus. 



The method of i>:ranu]atin<i: cyanamid was studied and improve- 

 ment indicated in the prej)aration of a product less objectionable for 

 fertilizer use. 



Work on the silent electric discharge has been largely of a theo- 

 retical and scientific nature, involving the energy requirements of 

 fixing nitrogen by this method. The progress of these lines of work 

 has been announced in the scientific press from time to time during 

 the 3^ear. 



PHOSPHORIC ACID INVESTIGATIONS. 



The regular investigations of the resources, production, consump- 

 tion, and movement of phosphates and phosphatic fertilizers were 

 continued throughout the year. The bureau kept in close touch 

 with recent developments and newly reported discoveries of phos- 

 phate minerals and as far as possible examined the merits of new 

 processes proposed and patented for producing phosphatic fertil- 

 izers. Much of this work is included in a paper published annually 

 in one of the technical journals. 



The broad phosphate problem, however, on Avhich the bureau ex- 

 pended most of its time and energy was the investigation of furnace 

 processes for volatilizing and collecting phosphoric acid in the con- 

 centrated form. These processes, which were devised mainly as the 

 means of conserving the immense quantities of phosphatic material 

 annually lost in preparing Florida rock for the market, have reached 

 the stage where they hold out promise not only as a possible means 

 of eliminating great losses of phosphoric acid incident to present 

 mining methods, but also as an economical way of utilizing large 

 deposits of relatively low-grade phosphates now regarded as of little 

 commercial value. In addition highly concentrated phosphates can 

 be produced by these methods, which will tend to offset the greatly 

 increased cost of handling and transporting fertilizer materials. 



The bureau has already shown that the electric furnace can be 

 successfully employed in bringing about volatilization of phosphoric 

 acid and was the first to demonstrate by actual experiment the feasi- 

 bility of using the Cottrell precipitator as a means of collecting the 

 phosphoric acid thus evolved. This work was carried to the point 

 where private enterprise Avas convinced of its value and a number of 

 installations are now in successful operation. 



Efforts are now being made to lower materially the cost of produc- 

 tion and thus greatly widen the use of furnace processes by showing 

 the feasibility of employing fuel instead of the electric current for 

 bringing about the volatilization of phosphoric acid. 



Much progress has been made on these investigations during the 

 year. Many of the chemical reactions involved have been worked out 

 and the problem of briquetting finely divided phosphates and thus 

 rendering them suitable for furnace treatment has been successfully 

 solved. Both laboratory experiments and those conducted on a semi- 

 commercial scale have definitely established the fact that a nearly 

 complete volatilization and recovery of phosphoric acid from mix- 

 tures of phosphate rock, sand, and coke can be brought about at the 

 temperatures attained and under the conditions existing in a fuel- 



