TJie Phosphates of America. 



131 



The finished liquid at 45 B. should contain nearly forty-five 

 per cent, of phosphoric anhydride, with only a mere trace of lime. 

 It will probably be contaminated to some extent by magnesia and 

 iron and alumina, but neither of these, provided it is not present 

 in any great quantity, will be a source of serious difficulty for the 

 purpose in view. 



We are now in possession of an acid body, which can take 

 the place of sulphuric acid in the manufacture of soluble and 

 assimilable phosphates, and we have only to come back to the old 

 superphosphate mixers, and use the same modes of manipulation 

 and the same system of calculation as -in superphosphate manu- 

 facture. All that is needed is to change the numbers, in order 

 to accord with the different composition of the two acids. 



A raw phosphate of about the following composition may be 

 taken as a typical material for economical treatment : 



Moisture and organic matter 3 . 00 



Phosphate of lime 75 . 00 (equal to 34.40 P.,O 5 ) 



Carbonate of lime 7.50 



Alumina and iron oxides (combined) 3 . 00 



Fluorides, silicates and sand 11 .50 



100 



The quantity of phosphoric acid of 45 B. required to trans- 

 form this insoluble phosphate into a "soluble" or readily "avail- 

 able " form may be taken from the annexed table. In calculating 

 it we have assumed in a practical way, and without pretension 

 to absolutely theoretical accuracy, that an acid solution of 45 B. 

 "factory test" will contain, say, forty-two per cent, of phosphoric 

 anhydride (P 2 O 5 ) or about fifty-eight per cent, of phosphoric acid 

 (H 3 P0 4 ). 



TABLE FOR USE IN THE MANUFACTURE OF HIGH-GRADE SUPERPHOSPHATES 

 FROM PHOSPHORIC ACID OF 45 B. 



We therefore proceed to ascertain that : 



