126 



The Phosphates of America. 



soon becomes extremely hot, generally attaining a temperature of 

 from 230 to 240 F. When properly composed it commences to 

 "set" almost at once, and at the end of the second day is suffi- 

 ciently hard to be dug out of the "den" with picks and shovels. 



In this state it is loaded into automatic dumping-cars and piled 

 up in heaps, all large lumps being broken down by a blow from 

 the shovel. In a couple of days it is ready to pass through a dis- 

 integrator and may then be put up in bags. 



The average superphosphate manufactured in this country con- 

 tains about thirteen to fourteen per cent, of "available" P 2 O 5 , 

 but the rapid development of the industry during the past few 

 years has led to the introduction of what are known as "high- 



AUTOMATIC DUMPING CAR FOR SUPERPHOSPHATE WORKS. 



grade supers," containing about forty-five per cent, of phosphoric 

 anhydride (P 2 O 5 ) in a "water" and "citrate" soluble form. The 

 plan upon which these goods are produced is perfectly scientific 

 and rational, much more so, in fact, than the one we have just 

 described, for it consists in using phosphoric acid as the solvent in 

 lieu of the oil of vitriol. 



The theory of the action of phosphoric acid upon pure phos- 

 phate of lime may be explained by either of the two following 

 simple equations, or, to speak more correctly, by a combination 

 of both of them : 



Ca 3 P 2 8 + 4(H 3 P0 4 ) + 6H 

 1 insoluble tri- + 4 phosphoric + 6 water 

 calcic phos- 

 phate 



= 3 CaH 4 (P0 4 )2(H 8 0)2 

 = 3 crystallized "acid'* 

 or "soluble" phos- 

 phate. 



