362 



PRINCIPLES OF STRATIGRAPHY 



These soda lakes also deposit crystals of gaylussitc( CaCOg-NasCOg- 

 5H2O), although the analysis of the water shows no calcium, the 

 minute quantities of this element brought in by springs, etc., prob- 

 ably combining at once to form this mineral (Clarke-ioi/pz; 22"/). 

 The carbonates deposited by these lakes are probably three in num- 

 ber: thennonatrite (NagCOg.HaO), natron (Na2C03.ioH20), and 

 trona or urao (Na2CO3.NaHCO3.2H2O). The proportion of these 

 varies, but the third is the most important. This is the first salt 

 crystallizing out on fractional crystallization of the waters of Owens 

 Lake, Inyo County, California, where sodium carbonate is manu- 

 factured on a commercial scale. The following analysis shows the 

 composition of the salts of successive crystallizations which took 

 place during the experiments (Chatard, quoted by Clarke-io:/p^; 

 228) : 



Table shoiving successive crystallization, resulting from the evap- 

 oration of the waters of Owens Lake. 



Stage of Crystallization 



Specific gravity of water or 



mother liquor 



At temperature (C) 



Salinity in permille 



Volume 



Composition: 



H2O 



NajCOs 



NaHCOa 



Na.SOi 



NaCl 



Na2B407 



NaBOa 



KCI 



(CaMgi'cbs....'^ 



(AlFe)203 



SiO^ 



Organic matter 



Insoluble 



Total . 



Nat'l 

 Waters 



1 .062 



25° 



77.098 



1 .00 



34-95 

 7.40 



1438 



38.16 



0.63 



First 

 Crop 



4.07 

 0.08 

 0.05 

 0.28 



1. 31: 



27.9° 



385-49 

 0.20 



14 51 

 43-75 

 30.12 



3-18 

 7-44 



1.07 



o. 14 



0.01 



0.055 



0.032 



0.078 



100.385 



Second 

 Crop 



1. 31: 



25° 



4-33 

 22.84 

 10.53 



25-44 

 35-06 



0.09 



99.41 



Third 

 Crop 



1-315 



26.25° 



3-43 

 18.19 



4.06 

 26.70 

 45-59 



1. 14 

 0.06 



99.17 



Fourth 

 Crop 



1.327 



35-75° 



2 .24 

 12.51 



3-88 

 19.01 

 60.99 



o.oi 

 0.05 



99.90 



Fifth 

 Crop 



30 



-9° 



11.03 



55-04 

 4.09 

 5-70 



19. 16 



2.01 

 2.93 



0.02 

 o. 16 



1 00 . 1 4 



In Egypt there are 9 soda lakes, the largest 10 km. long, 3 km. 

 broad, and 6 meters deep (Walther-6i '.790). The salt forming on 



