of Kentucky, New Jersey, Tennessee, and other States. Like the 

 minerals of the third group it is a refractory silicate, and the potash 

 which it contains is not readily available. 



The potash-bearing silicates are among the most widely dis- 

 tributed minerals and occur as constituents of nearly all rocks. The 

 principal minerals of this class from the point of view of the potash 

 which they contain are orthoclase, or microcline, muscovite, and 

 leucite. Millions of tons of rock containing one or more of these and 

 related minerals with a potash content in the neighborhood of 10 per 

 cent are to be found widely distributed all over the globe. It is for 

 this reason that the igneous minerals, particularly the potash feld- 

 spars, are most often spoken of as a source of potash salts. 



In Table I is given sample analyses of the most important potash- 

 bearing minerals : 



TABLE I. Analyses of potash-bearing minerals. 



(1) Alunite from Marysvale, Utah. Selected specimen. Analysis by W. T. Schaller, Bui. U. S. Geol. 

 Survey, No. 511, p. 8. 



(2) Glauconite from greensand marl. Hanover Co., Virginia. Analysis by M. B. Corse and C. 

 Baskerville, Am. Chem. Jour., 14, 627. 



(3) Ground commercial feldspar from quarry of J. B. Richardson & Sons, Bedford, Ont. Analysis by 

 George Steiger, Bui. U. S. Geol. Survey, No. 420, p. 9. 



(4) Muscovite from Auburn, Maine. Analysis by R. B. Riggs, Bui. U. S. Geol. Survey, No. 419, p. 286. 



(5) Leucite-bearing rock, Wyoming. Analysis by W. F. Hillebrand, Bui. U. S. Geol. Survey, No. 512, 

 p. 11. 



The desirability of finding some economical way of extracting pot- 

 ash from these minerals has long attracted the attention of various 

 investigators, and numerous patents have been issued covering proc- 

 esses which are claimed to solve this difficult problem. 



The increasing yearly demand for potash salts in connection with 

 artificial fertilizers has of late renewed interest in this direction, and 

 in some cases companies have been organized for the purpose of 

 manufacturing potash by one or other of the various processes which 

 have been proposed, but up to the present no potash prepared in 

 this way has been placed on the market. 



Practically all methods yet proposed, in principle at least, have been 

 covered by patents. A comparative study was therefore undertaken 



[Cir. 711 



