ELTSHA MITCHELL SCIENTIFIC SOCIETY. 23 



The charge was : 



Rock, ♦ 1,200 lbs. 



Sulphuric Acid 47° B, 1,050 " 



The temperature of the acid was 60° C. (140° F.), the tem- 

 perature in the mixer 82° C. (180° F.). The mixture was 

 stirred vigorously for three minutes, sampled, and dumped. The 

 sample was put into a tightly-corked bottle, cooled at once, and 

 analyzed. The analytical method throughout was that of the 

 Association of Official Chemists for 1884. For the 'determina- 

 tion of free phosphoric acid the following method was employed : 

 Two grams (2 grms.) substance were extracted with 200 c. c. 80° 

 alcohol, and the phosphoric acid estimated in the filtrate. The 

 calculation was : 



X=free P 2 5 . 

 Y=P 2 5 as CaH 4 P 2 O s . 

 P=P 2 5 extracted by water. 

 Q=P 2 5 extracted by 80° alcohol. 



Th 



en 



P=X+Y. 



Q=X+iY. 

 X=2Q— P. 

 Y=2(P— Q). 



After finding, by several careful determinations, that the dry- 

 basis total P 2 () 5 was 15.84 per cent., for convenience of compari- 

 son the following table was constructed : 



