Tennessee Valley Authority, Wilson Dam, Ala. r)iammonium phosphate, produced from anhydrous ammonia and electric-furnace phosphoric acid in a pilot plant using a new, saturator-type process, consisted of aggregates of thin tabular crystals bonded by a film of fine crystals. The product contained 0 to 5% of monoammonium phosphate, but otherwise was substantially free of impurities. Laboratory tests showed the product to be strong enough to withstand ordinary fertilizer handling without excessive degradation, satisfactorily nonhygroscopic, satisfactorily drillable, and suitably stable with r e s p r r t to loss of ammonia by volatilization under normal IllMMONIUM phosphate [(NHJPHPO~; 21.2% nitrogen D and 53.8% phosphorus pentoxide1 has not enjoyed wide usage in this country as a fertilizer; this may be attributed at least in part to the poor behavior of some diammonium phosphate mixtures that have been used in the past and to unfavorable reports on important fertilizer properties of the salt. Most of the diammonium phosphate that has been used in this country wm imported from Germany before World War I1 in the form of granulated nitrogen-phosphorus pentoxide-potassium oxide mixtures (Nitrophoska), prepared by adding a hot concentrated solution of ammonium nitrate to a dry mixture of diammonium phosphate and potassium chloride or sulfate and cooling the mixture in granulating equipment ( 4 , 80). The high initial temperature of the mixture in this procedure was thought to result in some loss of ammonia from diamnionium phosphate (80). ' Most of the Nitrophoslras were characterized by relatively high ammonium nitrate content and nitrogen-phosphorus pentoxide ratio. Therefore, they were hygroscopic and tended to cake and become undrillable unless handled with special care (80). The production of Nitrophoslra from diammonium phosphate was discontinued by the Germans several years ago because of the unsatisfactory physical properties of the product and its tendency to decompose during handling ( I S ) .The properties of diamnioniuin phosphate Chat may affect its use as a fertilizer in this country by itself or in ungranulated mixtures are not well established, although a number of miscellaneous properties of general interest have been reported (5, 6, 9-11, 16, 16, 19, 83'). It is nonpoisonous, nonexplosive, and nonflainmable (it is used as a flame-proofing agent). Several authors have referred qualitatively to the instability of the salt, Collings (8) stated that. it has not been used as extensively as the monosalt "because of its unstable nature and its poor physical condition." Ross, Mehring, and Merz (1'9) observed that it loscs ammonia when moistened with water and concluded that for this reason, and because i t is less convenient t o prepare than t,he monosalt, it would find limited application in this country unlcss mixed with acidic materials. Mehring and Cumings (1.5) reported that it lost ammonia and bcc:tnie paqty when exposed to 1 Present address. Mississippi Chemiual Corporation, Leland, Miss. * Present a...