78 GEOLOGICAL HISTORY OF LAKE LAHONTAN. 



A water sample collected from the south side of the lake in August, 

 1867, and analyzed by Prof 0. D. Allen, had a specific quantity of 1.0975, 

 and gave a fixed residue of 114.7 parts per thousand, and on spectroscopic 

 examination was found to contain lithia in addition to the elements given in 

 the above analyses.'^ 



In obtaining carbonate of soda from the waters of the larger lake two 

 methods are in use. One is known as the "cold weather" and the other as 

 the " warm weather" process. In the former the water of the lake is con- 

 ducted into vats along its shore, and has a density of about 12° of Beaume's 

 areometer As it evaporates beneath the heat of the summer sun its density 

 increases until it approaches 30° B. At this point more water is added from 

 the lake. This process is continued until cold weather approaches; the vats 

 are then so adjusted as to have a density approaching 30° B. The lowering 

 of the temperature on the approach of winter causes sodium carbonate and 

 sodium sulphate to be precipitated at the bottom of the vats in a liard 

 crystalline layer, which, when removed to the drying sheds, crumbles 

 to a fine white powder. The "soda" formed by this process contains about 

 equal portions of sulphate and carbonate, as shown by the following anal- 

 ysis by Dr. F. W. Taylor of a sample of the material as it is sent to the 



market: 



Per cent. 



Silica 0. 449 



Irou aud aluiuimim . OIJ 



Calcium sulphate 038 



Magnesium sulphate . 040 



Sodium chloride 2. 193 



Sodium sulphate 49. 437 



Sodium carbouate 40.714 



Water 7.118 



100. 000 



While concentrating the waters in the soda vats during the summer, if 

 the density increases beyond about 30° B., carbonate of soda and sulphate of 

 soda are precipitated, and, if concentration continues, is soon followed by the 

 deposition of common salt. In this process the water is conducted from vat 

 to vat, becoming gradually concentrated as it progresses. When in the last 



■"' U. S. Geological Exploration of tho Foitietli Piuallol, Vol. II. p. 747. 



