114 MANUFACTURE OF FERTILIZING MATERIALS 



soluble potassium chloride and insoluble sili- 

 cates of calcium and aluminium. The heating 

 is continued 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 1100 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 produced at 

 this temperature. 



In 1900 United States Patent No. 641,406 

 was granted to G. J. Rhodin for obtaining sol- 

 uble potassium 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, 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 temperature 

 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 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. 869,011 

 was issued to Ralph H. McKee for a process 

 for obtaining potassium compounds from potash- 



