SOURCES OF PHOSPHORIC ACID. 139 



bones usually cost, in their rough state, from $20 

 to $25 per ton ; the grinding costs about $5. 

 The above value of $40.02 given to a ton of 

 ground bones, allows a profit of from $10 to $15 

 per ton to the manufacturers. 



There are only two available sources of phos- 

 phoric acid: First, the bones of animals; Second, 

 mineral guanos, known as Phosphorite, Apatite, 

 and Coprolites. The use of bones as a source 

 of phosphoric acid is limited; the trouble and 

 expense of collecting them, and the general 

 ignorance of their value, will at all times render 

 them an uncertain supply, as raw material for 

 the manufacture of fertilizers. But with the 

 second source mineral phosphates the case is 

 different. There seems to be scarcely any limit 

 to the amount. 



As a raw material for the manufacture of 

 soluble phosphoric acid or superphosphate of lime, 

 it is very valuable. If it is as free from the car- 

 bonates of lime and magnesia, and of other foreign 

 matter, as bones are, equal amounts of sulphuric 

 acid will liberate the same amount of soluble phos- 

 phoric acid from it, as from bones. Hence, other 

 things being equal, this mineral guano is fully 

 as valuable as bones for preparing soluble phos- 

 phates. As before remarked, there is scarcely 

 any limit to the supply of these mineral phos- 

 phates. The largest known deposit on this 

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