PHOSPHATE ROCK: UTILIZATION AS FERTILIZER. 19 



The reactions taking place at various stages of the process may be 

 represented thus: 



(1) NaC10 4 +H 2 0+Electric current=HC10 4 +NaOH. 



(2) 6 HC10 4 +Ca 3 (P0 4 ) 2 =2H 3 P0 4 +3Ca(C10 4 ) 2 . 



(3) 2H 3 P0 4 +3Ca(C10 4 ) 2 +4NaOH=2CaHP0 4 + lNaC10 4 +Ca(C10 4 ) 2 +4H 2 0. 



(4) 4NaC10 4 +Ca(C10 4 ) 2 4-Na 2 C0 3 =6NaC10 4 +CaC0 3 . 



This process was designed to treat low-grade phosphates which are 

 not suitable for the manufacture of acid phosphate. Cheap electric 

 power is essential for the commercial success of the process. 



PROCESSES FOR THE ENRICHMENT OF PHOSPHATES. 



The list of patents given in Table X, Appendix, includes processes 

 for the enrichment of raw or natural phosphates, as well as those 

 which have been chemically treated. 



While the writers have placed but five processes under this head, 

 a number of patents classified under other heads could have been 

 included here as well. 



The processes of both Ottolengin 1 and Coates 2 have for their object 

 the enrichment of phosphate rock or phosphatic limestone. 



Ottolengin advocates the grinding of the phosphate and then effect- 

 ing the separation of the phosphate particles from the impurities by 

 the difference in their specific gravities, such a separation being 

 made either by a blast of air or by suspending the material in 

 moving water. 



Unfortunately, in many of the natural deposits of phosphate, the 

 impurities contained therein have a specific gravity so nearly equal 

 to that of the phosphate rock that a separation on the above basis is 

 usually very incomplete. In the case of the brown-rock phosphate 

 of Tennessee, however, such a scheme is practiced with great success. 



By burning, slaking, and subsequently screening phosphatic lime- 

 stone Coates effects a segregation of the coarser and more phos- 

 phatic particles. This process, however, is intended primarily to 

 produce a finely divided sterile phosphatic material for subsequent 

 treatment. 



Pratt's 3 process for the enrichment of acid phosphate consists, 

 first, in adding sufficient lime to the superphosphate to convert the 

 monocalcium phosphate to dicalcium phosphate, then leaching out 

 the gypsum contained therein with some suitable solvent. The sol- 

 vent recommended by Pratt is sea water. 



' United States Patent No. 86674 (1809). 

 ' United States Patent No. 971830(1910). 

 1 ■'•■•■ i Btati Patents Nob. 1014264, 1014265 (1912). 



