POTASSIUM FERTILIZERS 171 



was one bushel more than when sulphate of potash alone 

 was used, so that it is clear that the sulphates of soda and 

 magnesia are really beneficial, whether potash is supplied 

 or not. For the purpose of converting the potassium minerals 

 into useful fertilizers for crops, it is a mistaken process to 

 attempt to prepare a pure potash salt, and it is a far greater 

 mistake to leave chlorine in if it can be avoided. It would 

 therefore be very much better to treat crude potash salts 

 with sulphuric acid and obtain the sulphates than to attempt 

 the removal of the sodium and magnesixim. The sodium 

 and magnesium are useful ; it is the chlorine that is objec- 

 tionable. On p. 134, when dealing with the superphosphate 

 industry, the problem of the consumption of sulphuric 

 acid in the future has been discussed. There is a possibility 

 that there may be too much sulphuric acid, and it is necessary 

 to find some useful purpose to which this surplus acid can 

 be put. The treatment of crude potash salts with sulphuric 

 acid is certainly one valuable way of disposing of surplus 

 sulphuric acid. No plant beyond that used in the I^eblanc 

 process is necessary ; sulphuric acid is generally made on the 

 spot at those works ; the hydrochloric acid produced would 

 be absorbed by exactly the same plant that is already there, 

 and the only difference would be that the resulting salt cake 

 would be sold directly for fertilizer purposes, instead of being 

 subsequently worked up for sodium carbonate and the 

 recovery of sulphuric acid. 



REFERENCES TO SECTION IV. 



Cresswell, " Possible Sources of Potash," Journ. Soc. Chem. Ind., 

 April, 1915, p. 387. 



Russell, " How can Crops be Grown without Potash ? " Journ. Bd t 

 Agric., 1915-16, p. 393. 



Cranfield, " A New Source of Potash," Journ. Bd. Agric., 1917-18, 

 p. 526 ; Journ. Soc. Chem. Ind., 1917, p. 1006. 



Haber and Peath, " Leaching Flue Dust from Cement Kilns," Journ. 

 Soc. Chem. Ind., 1917, p. 503. 



Treanor, " Potash from Cement," Journ. Soc. Chem. Ind., 1917, p. 961. 



" Potash Recovery at Blast Furnaces and Cement Works," Journ. Soc. 

 Chem. Ind., 1917, p. 327. 



" American Potash in 1917," Journ. Soc. Chem. Ind., 19*9, P- 2 4 8 R - 



Rossiter and Dingley, "Some Chemical Aspects of the Potash Industry 

 in Great Britain," Journ. Soc. Chem. Ind., 1919, p. 383 T. 



