AI,KAU 113 



and sodium chloride somewhat more soluble in hot than in cold 

 water. During warm weather there would be a greater tendency 

 for anhydrite to separate and in colder weather for sodium chlo- 

 ride to be precipitated. Anhydrite at the surface would gradually 

 absorb water vapor from the atmosphere and be transformed to 

 gypsum. 1 



Besides the principal salts just described, there may 

 separate at one concentration or another other various dou- 

 ble salts including langbeinite (2MgSO 4 .K 2 SO 4 ), polyhalite 

 (K 2 SO 4 .MgSO 4 .2CaSO 4 .2H 2 O), glauberite (CaSO 4 .Na 2 SO 4 ), 

 syngenite (CaSO 4 .K 2 SO 4 .H 2 O), potassium pentasulphate 

 (K 2 SO 4 .5CaSO 4 .H 2 O, krugite (4CaSO 4 .K 2 SO 4 .MgSO 4 .2H 2 O), 

 and possibly others. These are all stable over very restricted 

 ranges of concentration, however, and if formed, probably sel- 

 dom persist, but pass over to more stable salts as the desicca- 

 tion proceeds, and have little more than a passing theoretical 

 interest. 



The addition of carbonates to the system introduces some 

 further modifications. 2 In this case lime carbonate is the first 

 salt to be precipitated, followed probably by the same order of 

 deposition as outlined above. As the mother liquor becomes 

 more concentrated, it apparently loses its alkaline character, for 

 the addition of an alcoholic solution of phenolphthalein does 

 not produce the characteristic red color. That the solu- 

 tion does actually contain dissolved carbonates is shown by the 

 appearance of the red color on diluting a portion of the mother 

 liquor with distilled water. An interesting example in nature 

 is furnished by the Great Salt Lake, Utah. A test of the water 

 of this lake in 1899 gave no alkaline reaction with phenolphthalein, 



*As examples, some of the gypsum deposits of Kansas may be cited, 

 according to Haworth, Mineral resources of Kansas, 1897, p. 61, and 

 the classical case at Bex, Switzerland, described by J. G. F. Charpentier, 

 Uber die Salz-Lagerstatte von Bex: Ann. Phys. Chim., 3, 75-80 (1825), 

 and by G. Bischof, Elements of chemical and physical geology, London, 

 1854-58, Vol. i, pp. 350-1. 



*The action of water and aqueous solutions upon soil carbonates, 

 by Frank K. Cameron and James M. Bell, Bull. No. 49, Bureau of Soils, 

 U. S. Dept. Agriculture, 1907. 



