260 



THE CANADIAN NATURALIST. 



[Sept, 



data, exhibits the amounts of anhydrous acid, and also of 

 acid, of specific gravity 1.712 (i.e.^ of the usual chamber 

 strength), necessary for the complete conversion of one hun- 

 dred parts, by weight, of mineral containing various percent- 

 ages of apatite, of the above composition, vrith a wholly 

 calcareous matrix : — 



TABLE VII. 



Acid required to change Apatites to " Superphosphates." 



The use of this table is that it ought to prevent any danger 

 of having free sulphuric acid in the product, or of proceeding 

 further than the complete conversion of apatite into soluble 

 phosphate. By means of a table of specific gravities, the 

 quantity of acid, of any required strength, may be easily 

 estimated for treatment of a given mineral. 



The conversion of apatite into acid phosphate of lime may 

 may also be effected by the use of hydrochloric acid, and, 

 under certain circumstances, this method may be preferable 

 to the use of the oil of vitriol. For 36-5 parts of hydro- 



