114 TH E SOU, SOLUTION 



but the reaction appeared promptly when distilled water was 

 added, and further examination showed the water to contain 

 about 0.012 per cent, sodium carbonate. 1 Slosson has reported 

 similar cases in Wyoming. 2 



One "black-alkali" system has been studied with some approach 

 towards completeness. 3 In this case magnesium and potassium 

 salts are not present, the system being composed of water, car- 

 bon dioxide, chlorides, sulphates, sodium and calcium salts, 

 with the condition imposed, that the bases are present in amounts 

 more than equivalent to the sulphuric and hydrochloric acids. 

 On desiccation at 25 C. calcium carbonate first appears fol- 

 lowed by gypsum and then sodium sulphate decahydrate. Next 

 appears a double salt (2CaSO 4 .3Na 2 SO 4 ) followed by anhydrous 

 sodium sulphate, the Glauber's salt which formerly crystallized 

 being no longer stable. Sodium chloride then precipitates and 

 the concentration finally reaches a point where gypsum is no 

 longer stable, and the final group of salts in contact with the 

 evaporating solution under conditions of stable equilibrium con- 

 sists of calcium carbonate, the double sulphate of soda and lime, 

 anhydrous sodium sulphate and sodium chloride. 



The desiccation of a lake which serves as the final repository 

 of a regional drainage involves essentially the principles just 

 discussed. 4 The constituents involved are the same. A serious 



1 Application of the theory of solutions to study of soils, by F. K. 

 Cameron, Report No. 64, Field Operations of the Bureau of Soils, 1899, 

 p. 149- 



2 Alkali lakes and deposits, by W. C. Knight and E. E. Slosson, 

 Bull. No. 49, Wyoming Agr. Expt. Station, 1901, p. 108. 



3 The solubility of certain salts present in alkali soils, by Frank 

 K. Cameron, J. M. Bell and W. O. Robinson, Jour. Phys. Chem., 11, 

 396-420 (1907). 



4 It has been suggested that the fact that shales or similar geological 

 deposits are frequently to be found near alkali areas, indicates that the 

 shales are the principal sources of the alkali. It is supposed that the 

 constituents of the alkali salts were formed by the action of water 

 on the shale minerals at or about the time the shales were deposited, 

 and carried down with the latter. Subsequently the alkali has been 

 leached out to appear at the surface of soils, generally at a lower level 

 than are the shales. 



