all in a finely powdered condition. The mixture is then heated in a 

 closed vessel of iron or other material, or else in an open-hearth or 

 blast furnace, to a bright yellow heat and maintained at that tem- 

 perature for a considerable time, care being taken not to melt or fuse 

 the mixture. The cooled mass which still remains in a powder may 

 be applied directly as a manure, since the potash present is claimed 

 to be rendered available by the treatment, or it may be separated 

 from the mass by treatment with acids. 



In 1907 United States patent No. 869011 was issued to Ralph H. 

 McKee for a process for producing potassium compounds from 

 potash-bearing material containing mica by essentially the same 

 treatment as that covered by Rhodin's patent for the extraction of 

 potash from feldspar. 



United States patent No. 987436 was granted to A. S. Cushman 

 in 1911 for a method for obtaining potash from silicate rocks. 

 According to this method the feldspathic rock is reduced to as fine 

 a subdivision as possible #nd mixed with finely powdered quicklime 

 in the proportion of 100 parts of the rock to 20 parts of lime. The 

 mixture is then spread on a suitable conveyor, as belt or drum, in 

 the form of a bed having a thickness from three-eighths to one-half 

 inch. To the surface of this bed is now applied a solution of cal- 

 cium chloride in separate drops, and of such a concentration that 

 the amount of calcium chloride added should be sufficient to supply 

 chlorine in quantities at least molecularly equivalent to the total 

 alkali contained in that portion of the feldspar which becomes 

 aggregated into lumps on the addition of the solution. The aggre- 

 gates, which harden quickly at ordinary temperatures, are separated 

 from the unconverted powder by screening, and are then heated in a 

 rotary kiln at a temperature preferably, but not necessarily, below 

 the point at which a substantial part of the potassium chloride is 

 sablimed. The product is discharged continuously from the furnace 

 in lumps and may be crushed for use directly as a fertilizer; or 

 the potassium chloride may be extracted by means of water and 

 recovered from the solution, or utilized therein in any preferred way. 



From a comparative study which was made of these patents it 

 does not appear that the use of sodium chloride has any advantage 

 over calcium chloride. The latter is a by-product obtained in large 

 quantities in the manufacture of sodium carbonate, and is some- 

 what more effective than the former in bringing about complete 

 decomposition of the feldspar, but when limited amounts of the re- 

 agents are used more potash is rendered soluble with the use of 

 sodium chloride than with calcium chloride. In Table II are given 

 the percentages of the total potash in the feldspar which have 



[Cir.71] 



