1901.] 



PUBLIC DOCUMENT — Xo. 33. 



69 



Analyses of PJiospJiatic Slag (Per Ce7it.). 



[I., bouslit for field experiments, 1894 ; II., sent on from Hatfield, Mass., 1893 ; III., 

 sent on from Marslifield, Mass., 1893 ; IV., sent on from Amberst, Mass., 1893; 

 v., sent on from Manslield, Mass., 1900.] 



The analyses of phosphatic slag in earlier years, as a rule, 

 show lower percentages of ammonium citrate soluble phos- 

 phoric acid "vvhen subjected to the same current mode of treat- 

 ment as other phosphatic fertilizers, — a circumstance due to 

 the presence of a varying quantity of caustic lime, which 

 caused a decomposition of the citrate of ammonia, and thus 

 affected more or less seriously its power to dissolve the avail- 

 able phosphoric acid present. The recognition of this fact 

 on the part of chemists has caused the adoption of a modifi- 

 cation in the character and the concentration of the citrate 

 of ammonia solution proposed by Dr. P. Wagner, which aims 

 at a neutralization of the free lime. The determination of 

 available phosphoric acid in phosphatic slag, by Wagner's 

 method, for trade purposes is to-day generally adopted. As 

 our above-stated analyses of phosphatic slag extend over a 

 period of more than twelve years, the main interest in our 

 results consists in the statement of the amount of total phos- 

 phoric acid found present. 



Aside from these recent changes in the current modes of 

 analyzing these phosphates, there has l)een introduced an 

 important change in the manufacture of phosphatic slag for 

 manurial purposes. As in the fertilizer trade, the valuation 



