of all the processes for which patents have been allowed, with a view 

 to finding what methods, if any, give promise of being practicable 

 commercially. It is thought advisable to publish some of the results 

 thus far obtained. 



The most convenient way of determining the alkalies in silicate 

 rocks is the well-known J. Lawrence Smith method. According to 

 the directions usually given for this method, 0.5 gram of the ground 

 material is mixed with an equal weight of pure ammonium chloride 

 and 4 grams of calcium carbonate. On igniting the mixture gently 

 at first, the ammonium chloride is volatilized and part of the calcium 

 carbonate is converted into calcium chloride. These two compounds 

 of calcium when heated at a temperature of about 1,000 C. with feld- 

 spar, or other silicate rock, bring about its decomposition, and any 

 potash present is converted quantitatively into potassium chloride. 

 The same result is obtained if the proper amount of calcium chloride 

 is used instead of ammonium chloride in the first place. 



Of the many patents which have been issued for extracting potash 

 from silicate rocks, at least four may be considered modifications of 

 the J. Lawrence Smith method, since the essential feature of each 

 consists in heating the potash-bearing material with calcium car- 

 bonate and some metallic chloride. 



The first of these, United States patent No. 513001, was issued to 

 H. S. Blackmore in 1894. To produce a soluble potassium salt accord- 

 ing to this patent, orthoclase, reduced to a fine powder, is mixed 

 with finely powdered calcium chloride in about equal proportions 

 to the potassium 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 1,100 C., whereby 

 the water mixed with the mass is converted into superheated steam 

 at a high pressure, which is supposed to assist materially in the 

 transformation of the orthoclase into .soluble potassium chloride and 

 insoluble silicates of calcium and aluminum. The heating is con- 

 tinued for about two hours, and, after cooling, the mass is placed 

 in vats and lixiviated. 



The part of the process as patented which requires the moist 

 mass to be heated in a sealed furnace to a temperature of 1,100 C. 

 could obviously not be carried out on a large scale, for it would not 

 be feasible to make a furnace which would stand the pressure pro- 

 duced at this temperature. 



In 1900 United States patent No. 641406 was granted to G. J. 

 Rhodin for obtaining soluble potassium salts from feldspar. In 

 carrying out the process according to this invention, 1 part of 

 feldspar is mixed with 1 part of lime and 0.2 part of sodium chloride, 



[Cir. 71] 



