18 BULLETIN 312, U. S. DEPARTMENT OF AGRICULTURE. 
processes correct the acidity of the superphosphate which some 
farmers consider so objectionable, and at the same time enhance the 
value of the product. 
The process of Collett + consists in dissolving phosphate rock in 
dilute nitric acid, and then adding ammonium sulphate to the solu- 
tion, with the result that lime is precipitated as sulphate, and ammo- 
nium phosphate and ammonium nitrate remain in solution. After 
separating the gypsum, the ammonium salts may be crystallized out by 
concentration of the solution. The reactions may be represented 
thus: 
(1) Ca,(PO,).+4HNO,—CaH,(PO,),+2Ca(NO,)>. 
(2) CaH,(PO,).+2Ca(NO;).+3(NH,),S0,—3CaSO,+4NH,NO,+2NH,H,PO,. 
This last process is particularly interesting from a commercial 
standpoint, since it has for its object the production of a high-grade 
fertilizer containing both phosphoric acid and nitrogen in readily 
available forms. Where phosphate rock occurs in regions far from the 
fertilizer markets, the production of a highly concentrated product 
which will admit of long shipment is essential! to the successful develop- 
ment of the mining part of the phosphate industry. 
The evaporation of the solutions, however, to the point where the 
ammonium salts begin to crystallize out would entail considerable 
expense. 
PROCESSES DEALING WITH THE PRODUCTION OF AVAILABLE 
PHOSPHATES BY ELECTROLYSIS. 
Processes under this head are of two types: (1) Those in which the 
phosphate rock is fused and the electric current passed through the 
melt; and (2) those in which some water-soluble salt or acid is used 
as an electrolyte and the ground phosphate rock suspended or dis- 
solved in the solution and the electrolysis performed in the wet way. 
A list of the patents on this subject is given in Table IX, Appendix. 
The process of Palmaer and Wiborgh ? for the production of dical- 
cium phosphate is said to have been successfully practiced in Norway 
where cheap water power is available. The process is as follows: 
Perchloric acid and sodium hydrate are produced by electrolizing a 
solution of sodium perchlorate in a diaphragm cell. Phosphate rock 
is then treated with the anode solution (perchloric acid) and the 
resulting solution of phosphate filtered. One half of the cathode 
solution (sodium hydrate) is then added to this filtrate, resulting in 
the precipitation of dicalctum phosphate and the formation of sodium 
perchlorate again. The other half of the cathode solution is treated 
with carbon dioxide and added to the solution decanted from the 
dicalcium phosphate precipitate, thus precipitating the lime as carbon- 
ate and completely regenerating sodium perchlorate. 
1 United States Patent No. 1058145 (1913). 2 United States Patents Nos. 707886 (1902); 748523 (1903). 
