IshuttJ nitre cake AND SUPERPHOSPHATE 147 



which 3-96 per cent was water soluble), as determined by 1 per cent 

 citric acid method. This is equivalent, practically, to a 43 per cent 

 conversion. By the A.O.A.C. methods the available phosphoric 

 acid was 4-37 per cent (practically entirely water soluble), or, ex- 

 pressed otherwise, a 23 per cent conversion. 



Wet Mix: The results generally as regards the total available 

 phosphoric acid in the several mixes, and hence in the degree of 

 conversion, are considerably higher than in the corresponding dry 

 mixes. In the series 6 N.C. : 6 C.A. : 1 H2O the total available 

 phosphoric acid is 9-90 per cent by the 1 per cent citric acid method 

 and 7-02 per cent by the A.O.A.C. methods. This, respectively, 

 is equivalent to 52 per cent and 37 per cent conversion of the total 

 phosphoric acid in the mix. 



Unfortunately more pressing work necessitated at this stage the 

 postponement of further prosecution of this investigation. As 

 opportunity permits the work will be proceeded with, laboratory 

 experiments being supplemented by trials on a larger scale, to simulate 

 more closely the results that would be obtained in the factory. Though 

 of a preliminary and incomplete nature, the results here presented 

 appear to justify the conclusion that the waste product nitre cake 

 could be used advantageously in the manufacture of a superphosphate 

 containing 7 per cent to 9 per cent available phosphoric acid (A.O.A.C.) 

 employing either Florida Pebble Phosphate or Canadian Apatite, 

 the only apparatus required being the grinding machinery for reduc- 

 ing the materials. 



Summary 



1. Employing finely ground Florida Pebble Phosphate (total 

 P2O5, 32-3%) a dry mix of 1 N.C. to 1 F.P.P. yielded a superphos- 

 phate containing 15-77 per cent available phosphoric acid as deter- 

 mined by 1 per cent citric acid method or 6-81 per cent by the A. O. 

 A. C. Methods. The wet mix, 6 N.C. : 6 F.P.P. : 1 H2O gave 16-09 

 per cent, and 9 -26 per cent available phosphoric acid, respectively, by 

 the two methods of analysis. 



2. Canadian Apatite (total P2O5, 39-40%) is less readily acted 

 upon by the nitre cake than Florida Pebble Phosphate, the products 

 of the several mixes showing lower percentages of available phos- 

 phoric acid than the corresponding mixes with the latter phosphate. 



The dry mix 1 N.C. to 1 C.A. gave a product containing 8-43 

 per cent and 4-37 per cent available phosphoric acid, respectively, 

 by the 1 per cent citric acid method and the A.O.A.C. methods. 

 The wet mix product from 6 N.C. : 6 C.A. : 1 HoO contained 9-90 



