20 U. S. COAST AND GEODETIC SURVEY 



of laboratory work and of computation, described by Mr. Cummings 

 in his paper, " makes it possible to run about 30 samples and to 

 correct each specific gravity to the value corresponding to 0° all 

 within one hour." 



SALINITY BY EVAPORATION TO DRYNESS 



According to Sir John Murray and Dr. Johan Hjort, in The 

 Depths of the Ocean, " the direct determination of salinity by evap- 

 orating a known volume of water to dryness does not give accurate 

 results, unless the amount of chlorine is carefully determined before 

 and after the evaporation, because in the last stages of evaporation 

 and in drying the residual salt uncertain amounts of chlorine are 

 disengaged in the form of hydrochloric acid." 



Clarke, in The Data of Geochemistry, states that it is principally 

 the magnesium chloride that breaks down during evaporation. In 

 any case this method is not to be recommended, although at first 

 thought it seems to be most straightforward. 



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