PHOSPHATE ROCK: UTILIZATION AS FERTILIZER. 19 
The reactions taking place at various stages of the process may be 
represented thus: 
(1) NaClO,+H,O+ Electric current=HC1O,+ NaOH. 
(2) 6 HC1O,--Ca,(PO,),=2H;P0,+3Ca(C10,)>. 
(3) 2H,PO,+3Ca(C10,).+4NaOH=2CaHPO,+ 4NaClO,+Ca(Cl0,),+4H,0. 
(4) 4NaCl0,+-Ca(C10,).+Na,CO,—6NaClO,+CaCO,. 
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 ' and Coates ? have for their object 
the enrichment of phosphate rock or phosphatic limestone. 
Ottolengin advocates the grinding of the phesphate 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* 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. 
1 United States patent No. 86574 (1869). 
2 United States Patent No. 971830 (1910). 
2 United States Patents Nos. 1014254, 1014255 (1912). 
