ELISHA MITCHELL SCIENTIFIC SOCIETY. 35 



Twenty-four hours after mixing, the temperature of the large pile 

 of one hundred tons, of which this was a fair sample, was 180°F 

 <82='C.), and the composition of it was as follows : 



Per cent. 



Moisture at 2I2°F 16.50 



Phosphoric acid Sol. in water 9.48 



" Insol. in water.. 3.67 



" " Reverted 2. go 



" Insol. Am. Cit. 65° .77 



" Total ...13.15 



The calculated analysis is based upon the following reaction : 



Ca3P20,+,H.SO, = CaH4P,Os-l-2CaS04. That is to say : 200 

 pounds of 53^B acid are required to render soluble all the phospho- 

 ric acid in 100 pounds bone phosphate. As pure bone phosphate 

 (CaaPoOgj contain845.81 percent, phosphoric acid, itfollows that 4. 36 

 pounds 53=^8 acid are required to render soluble 1 pound of phosphoric 

 acid in bone phosphate, or 5.02 pounds 47°, (as 1 pound 53=B = 1.15 

 pounds 47^). One pound (1 lb.) then of 47"^ acid renders soluble .20 

 lb. (two-tenths of a pound) of phosphoric acid in bone phosphate. 



Let us assume for the moment that the above reaction is the only 

 one that takes place. It is not really the only one, but for our 

 present purpose we can take it so. 



The 1200 pounds of rock used contained 273.84 pounds phosphoric 

 acid (12 X 22.82=273.84), therefore, to render the whole of it soluble 

 we should have added 1374.67 pounds 47*^ acid. We actually used 

 1050 pounds 47^. The difference then between what we should have 

 added and what we did add, multiplied by the co-efficient of solu- 

 bility (in this case .20) represents the phosphoric acid we could have 

 made soluble but did not. Thus (1374.67—1050) X .20=64.934 

 pounds phosphoric acid insoluble in water, or 2.88 per cent, as 



100 H- _2250_ _ 2 gg Qj course the difference between the total 

 64.934 



phosphoric acid and the insoluble in water gives the soluble phos- 



2250 



phoric acid, but it can also be calculated, as 100 -^ =9.33 



1050 X. 20 

 per cent. 



•The presence of so much oxide of iron in the rock probably accounts 

 for the discrepancy between the "calculated" and the "found" 

 soluble phosphoric acid. The discrepancy between the two "mois- 

 tures " arises from the fact that in the calculated moisture no allow- 

 ance is made for carbonic and hydrofluoric acids. If these three 



