FERTILIZERS. 125 



soluble phosphoric acid (superphosphate-gypsum, plain sui)erphos- 

 ])hate, etc.) when au excess of nitrogen as free ammonia or carbonate of 

 ammonia is X)resent, and (2) in what form the ])hosphoric acid is after 

 the action of the amuumia in either case. The method employed in the 

 latter investigations was in general as follows: Four grams of the 

 phosphate (with or without gypsum) was shaken up with a little water 

 in a liter tlask, decomposed either with ammonia water or a solution of 

 carbonate of ammonia or a mixture of the two, and sufticient water 

 added to make the volume 300 cc. After standing 24 hours the tiask 

 was tilled to the liter mark, digested for 2 hours, and liltered. The 

 phosphoric acid, sulphuric acid, and lime in the filtrate were determined. 

 Five portions of 100 cc. each of the tiltrate were evaporated to dryness 

 in platinum dishes, and after heating one half hour at 100'^ C. (which 

 expelled excess of carbonate of ammonia and moisture) tlie residues 

 were weighed. Two of these residues were taken u])in watcn-, distilled 

 with soda solution, and the ammonia in the distillate determined by 

 titration with sulphuric acid. The total amount of ammonia present 

 in the tiltrate was determined by direct distillation of 100 cc. of the 

 filtrate with soda solution. The other three residues were heated over 

 the naked flame at a temperature below glowing. The residue was 

 again weighed and its content of phosphoric acid and sulphuric acid 

 determined. Finally, 10 to 20 cc. of the filtrate was evaporated and the 

 residue examined under the microscope. 



The object of these operations was to determine (1) how much of 

 the ammonia present in the filtrate was combined with phosphoric 

 acid and how much with suli)huric acid, (2) how much of the phos- 

 phoric acid was in the form of monocalcium phosphate and how much 

 in the form of phosphate of ammonia, and (3) whether gypsum was 

 present and to what extent. 



These objects, it is claimed, were attained (I) by determining the sul- 

 phuric acid, phosphoric acid, and lime in the above filtrate; (2) by 

 making the same determinations in the evaporated residue, in which 

 there could only be sulphuric acid, phosphoric acid, ammonia, and lime, 

 possibly combined in hydrated monocalcium phosphate, the three phos- 

 Ijhates of ammonia, gypsum, and suli)hate of ammonia, and (3) by driv- 

 ing oft' over the flame the phosphates of ammonia, sulphate of ammonia, 

 the water of crystallization of the gypsum, and the water of constitu- 

 tion of the monocalcium phosphate.^ 



This method was employed in numerous experiments testing the 

 influence of ammonia or ammonium carbonate on (1) free and water- 



' Immendorf argues that under the treatment to whicli the residues are subjected 

 quite a different series of salts is formed; that the reaction under these conditions 

 is much more couiplex, and that it is impossible to draw any conclusions from the 

 composition of the ignited residue as to that of the dried residue or from the compo- 

 sition of the latter as to that of the filtrate (p. 129). 



