296 ANNUAL EEPORTS OF DEPARTMENT OF AGRICULTURE. 



NITROGEN FIXATION. 



One of the chief difficulties in the operation of the Haber process 

 has been the complete removal of ammonia from- the gaseous mixture. 



The bureau's work on this phase of the problem has developed a 

 method that, it is believed, is superior to any of the methods em- 

 ployed heretofore. A small unit designed for this process has been 

 constructed and is being operated in connection with the catalyst 

 testing plant of the Fixed Nitrogen Research Laboratory. A further 

 improvement on the process has been projected and is being tried out 

 on an independent unit. These improvements, if successful, will not 

 only remove the ammonia more completely from the gases, but can 

 be adapted to the character of catalyst being used, so that even very 

 sensitive catalysts will not deteriorate through the presence of 

 poisonous substances in the return gases. The success of the method 

 will mean a longer life for the catalyst and greater efficiency in 

 operation. 



PHOSPHATE INVESTIGATIONS. 



During the year investigations have been continued on the vola- 

 tilization of phosphoric acid from run-of-mine and low-grade phos- 

 phates, using a fuel-fed furnace and collecting the acid by means of 

 the Cottrell electrical precipitator. Considerable progress has been 

 made in this investigation and a number of reports antl papers have 

 been published in the scientific and technical press. The feasibility 

 of briquetting phosphates from various phosphate deposits for use in 

 this furnace process has been given close study, and experiments show 

 that many deposits of phosphate formerly considered unfit for fer- 

 tilizer manufacture are of an almost ideal composition for the smelt- 

 ing or furnace process of manufacture, wherein advantage is being 

 taken of certain of these impurities to further the chemical reactions 

 involved. A furnace plant of semicommercial size more fully 

 equipped and with better auxiliary apparatus has been preoted at 

 Arlington Experimental Farm, and the numerous mechanical prob- 

 lems encountered are gradually being worked out. The changes in 

 design and construction of certain units in this plant which must be 

 made from time to time involve careful study and make progress 

 somewhat slow, but the results so far obtained hold out great promise 

 of eliminating much waste, utilizing more fully our phos|)hate re- 

 sources, and of lowering the price of fertilizer to the ultimate con- 

 sumer. Phosphate miners, fertilizer manufacturers, and farm or- 

 ganizations are following this work with keen interest. 



It has been found that when the phosphoric acid obtained by the 

 volatilization process is collected at an elevated temperature phos- 

 phoric acid of such high concentration is obtained that, on cooling, it 

 crystallizes to a solid mass. By centrifuging these crystals and re- 

 crystallizing, if necessary, a product can easily be obtained of much 

 greater purity than any heretofore offered on the market. This fact 

 suggested the possibility of manufacturing a high-grade acid as a by- 

 product which would contribute to the economy of producing lower 

 grade phosphoric acid for fertilizer purposes. A study has been 

 made of the best conditions for the production of both grades of acid, 



