POTASSIC MANURES 113 



the potassium sulphate as it comes from the 

 furnace is in big lumps, it must be crushed before 

 delivery to the farmer. In the same way as the 

 price of potassium chloride is calculated on 

 the basis of an 80 per cent salt, that of potassium 

 sulphate is based on a 90 per cent salt, conse- 

 quently 100 Ib. of this product at 95 per cent 

 equals 110 Ib. at 90 per cent. 



About 90 patents have been issued by the 

 United States Government for extracting potash 

 from silicate rocks. At least four may be con- 

 sidered modifications of the J. Lawrence Smith 

 method, since the essential feature of each con- 

 sists in heating the potash bearing material 

 with calcium carbonate and some metallic chlo- 

 ride. 



The first of these, United States Patent No. 

 513,001, was issued to H. S. Blackmore in 1894. 

 To produce a soluble potassium salt according 

 to this patent, orthoclase, reduced to a fine 

 powder, is mixed with finely powdered calcium 

 chloride in about equal proportions to the po- 

 tassium silicate present. To the mixture is then 

 added an excess of calcium oxide and a sufficient 

 quantity of water to render the entire mass 

 moist. This is introduced into a sealed furnace, 

 or retort and heated to a temperature of about 

 1100 C., whereby the water mixed with the 

 mass is converted into superheated steam at 

 high pressure, which is supposed to assist ma- 

 terially in the transformation of the orthoclase into 



