128 



The Phosphates of America. 



method would open up a channel for the use of many low-grade 

 phosphates, which now, for lack of a market, are practically of no 

 value. The only essential conditions to be fulfilled are : 



A. That the material shall contain a minimum of carbonate of 

 lime, in order that no unnecessary excess of sulphuric acid need be 

 used. 



B. That it shall contain as small a percentage as possible of any 

 combination of iron and alumina, both of which, besides being diffi- 

 cultly soluble, contribute to the formation of a gelatinous mass that 

 seriously interferes* with the proper carrying out of the operations. 



In order to ascertain the quantity of sulphuric acid necessary to 

 insure the desired reaction, it is of course essential that the exact 

 composition of the raw material be first determined by a reliable 

 analysis. Supposing ourselves to be in possession of this informa- 

 tion, we may imagine that we are called upon to deal with a 

 mineral phosphate containing : 



Moisture and organic matter 4.00 



Phosphate of lime 55.00 



Carbonate of lime 3.50 



Phosphates of iron and alumina . 6.50 



Carbonate of magnesia 0.75 



Fluoride of lime 2.25 



Sandy and siliceous matters 28.00 



100 



The quantity of oil of vitriol of various strengths required for 

 the complete liberation of all the phosphoric acid, and the satisfac- 

 tion of all the bases in such a sample as this, is very readily calcu- 

 lated from the figures in the following table : 



TABLE SHOWING THE AMOUNT OF CHAMBER SULPHURIC ACID OF VARIOUS 

 STRENGTHS REQUIRED IN THE MANUFACTURE OF PHOSPHORIC ACID FROM 

 NATURAL PHOSPHATES. 



