wells: fractional precipitation 



21 



Electrolytic thermoelectromotive forces were measured also 

 and showed a linear relation over a range of temperatures as much 

 as 25 or 30°. 



We have constructed two calomel cells, one with a positive 

 temperature coefficient and the other with an equal negative 

 one. The two cells are identical except that the former is set 

 up with a 10 per cent zinc amalgam, and the latter with one of 

 about 0.8 per cent. When the two cells are joined in series, the 

 sum of their electromotive forces is independent of temperature 

 through at least the range 8° to 34° C. 



INORGANIC CHEMISTRY.— The Fractional Precipitation of 

 Carbonates. Roger C. Wells. Geological Survey. Com- 

 municated by F. W. Clarke. 



In a recent paper I described experiments upon the fractional 

 precipitation of sulphides and pointed out that the results were 

 in accord with what would be expected from our knowledge of 

 the solubilities of the sulphides in water. 1 In the experiments 

 with the sulphides fractionations were carried out with mixtures 

 of two metallic salts in various proportions. Similar experiments 

 are now being conducted with carbonates. Some preliminary 

 results are presented here for mixtures containing equivalent 

 quantities of each metallic salt. Full data and discussion are 

 reserved for a later paper. 



The procedure in these experiments was simple. A dilute solu- 

 tion containing two metallic salts in equivalent quantities was 



^con. Geol. 5; 1. 1911. 



