SODA INDUSTRY. 79 



of the series it has readied the desired density, sodium carbonate, tosfeiher 

 with sodium sulphate, is deposited. The -mother liquor is afterward returned 

 to the lake. The soda thus obtained is called "summer soda," and has 

 about the composition given in the above analysis, as is indicated by qual- 

 itative tests. The vats in which the evajioration is conducted are formed 

 by levees built along the shallow border of the lake, and are usually about 

 80 feet long by 50 feet broad; the Avater when evaporation commences is 

 usually from 12 to 14 inches deep. (Plate XVI.) 



When the waters of the lake are evaporated until a density of al)out 

 15° B. is reached, they assume a reddish tint, which increases as the con- 

 centration is carried forward, until at 30° B. they become of a bright cherry- 

 red color. Chemical tests show that this color is not due to the presence of 

 manganese or iron, but is probably produced by organic substances. 



The manufacture of soda at the larger lake was commenced in 1875, 

 and is yet in its experimental stage, although two or three hundred tons of 

 impure soda carbonate have been produced. The smaller lake when first 

 discovered is reported to have been dry, and presented the appearance of 

 an ordinary mud-playa. Excavations carried to the depth of about 25 feet 

 have shown that the material filling the basin is composed of layers of soda 

 salts, separated by strata of dust and mud. As the layers of soda in these 

 beds have the character of the "summer soda'' now formed in the vats, it 

 is evident that the crater has served as a natural evaporating pan, in which 

 the water accumulated during the wet season was entirely evaporated before 

 the dry season had passed. 



For the manufacture of soda in this basin, vats have been excavated in 

 the material composing its bottom. They are filled by water seeping from 

 its sides, which, as it enters the vats, has a density of from 10° to 15° B. 

 Concentration is carried on until the carbonate of soda begins to crystallize, 

 when a new supplj' of brine is added, and the process carried forward until 

 cold weather sets in, when an abundant crop of beautiful soda crystals is 

 formed during the first cold nights of autumn. After all the soda is pre- 

 cipitated that a lowering of temperature will produce, the mother liquor is 

 conducted back into lower depressions, and allowed to leach through the 

 soda-bearing strata once more The crust of soda obtained at the bottom 



