1870.] BROOME — ON CANADIAN PHOSPHATES. 259 



Apart from all associated matters, the apatite employed at 

 the Brockville works may be said to contain 92 per cent, of 

 phosphate of lime, and 7.2 per cent, of fluoride of calcium. 

 When such a mineral, commingled with its gangue of calcite, 

 is digested with a proper proportion of sulphuric acid, three 

 separate reactions result : — 



(a.) The tribasic phosphate yields up two- thirds of its 

 lime to the free acid, the remaining atom forming, with the 

 whole of the phosphoric acid present, the super-phosphate of 

 lime (acid phosphate of lime) . 



(5.) The calcite is wholly converted into gypsum, with 

 evolution of carbonic acid. 



((?.) The fluoride is decomposed, with formation of hydro- 

 fluoric acid and gypsum,* 



These reactions may be represented as follows : — 



(a.) 3 Ca 0, P0,+ 2 HO, S03=2 Ca 0, SO, + Ca 0, 

 HO, PO,. 



(5.) Ca 0, CO.-^HO, SO.^Ca 0, SOs + HO-f C^. 



(c.-) CaF + HO, S03=:Ca 0, S03 4-HF^ 



From the consideration of the atomic weights of these 

 substances, it will appear that 100*00 parts of phosphate of 

 lime (tribasic) will require 51 '61 parts of anhydrous acid 

 (SO.,), to convert it completely into the acid phosphate ; 

 that lOO'OO parts of fluoride of calcium requires 99*00 parts 

 of the same anhydrous acid (or, in round numbers, an equal 

 amount) to produce the reaction shewn in equation (c); and 

 that 100*00 parts of calcspar will require 66*00 parts of acid 

 for its complete decomposition. 



One part of apatite, of the percentage indicated as repre- 

 senting the pure mineral of the Brockville works, will require 

 •92-1- (*5161x*07.)=*545 parts of anhydrous sulphuric acid 

 exactly to effect the desired changes. 



The following table (Table No. vii.), compiled from these 



This iiTitates the -workmen's lungs so greatly that they are in the 

 habit of using rude respirators, formed of sponge. It is much more 

 obnoxious in foggy, still Treather, than M'hen any breeze is bloTrin"-, 

 Tvhich soon freet» the works from the most penetrating and disagreeable 

 odour. 



