SECTION IV. POTASSIUM FERTILIZERS 



Blast Furnace Potash. The blast furnace dust referred 

 to on p. 61 can be used directly as a manure, or it can be 

 worked up for concentration and purification. Much of 

 the blast furnace dust produced up to the present has been 

 used as the raw material for the preparation of potassium 

 compounds such as chlorate, permanganate, etc. Blast 

 furnace dust provides a very excellent source of high-grade 

 potassium chloride. Pure salts can be prepared more 

 easily from blast furnace dust than from mineral potash 

 compounds, consequently it is highly probable that blast 

 furnace potash will be largely used for industrial purposes ; 

 but just as there are large residues from the potash minerals, 

 so doubtless there will be residues from dusts also. Where 

 sodium chloride is added to the furnace for the purpose of 

 increasing the yield of potash, most of the potash is obtained 

 as chloride, and can be easily washed out of the dust by water, 

 and recovered from solution by crystallization. It will be 

 necessary to set up central factories to deal with this work 

 efficiently and make Great Britain self-supporting. 



Potassium Sulphate from Cement. The potash content 

 of clays and shales suitable for cement manufacture may be 

 as high as 2\ %. By adding fluorspar equal to 80 % of the 

 total potash present, 90 % of the potash is volatilized in a 

 cement kiln as potassium fluoride. The presence of sulphur 

 in the fuel produces sulphuric acid, which reacts with the 

 potassium fluoride and lime compounds present to form 

 calcium fluoride and potassium sulphate according to the 

 equation 2KF + CaSO 4 = CaF 2 + K 2 SO 4 . On washing the 

 resulting dust with water, potassium sulphate dissolves and 

 calcium fluoride is left in an insoluble form. By filtering 

 and washing at temperatures of 85 C. (185 F.), or 

 slightly over, the double salt CaSO 4 . K 2 SO 4 . H 2 O is prevented 



