84 Kansas Academy of Science. 



NOTE ON MERCUROUS SULFATE FOR STANDARD 

 CELLS. 



By H. P. Cady, University of Kansas, Lawrence. 



CARHART and Hullet have recently recommended that the 

 mercurous sulfate used in the preparation of Clark or cadmium 

 standard cells be prepared electrolytically by using an anode of 

 pure mercury, a cathode of platinium and sulfuric acid as the elec- 

 trolyte. The mercurous sulfate prepared in this way is crystalline 

 in character and gives very uniform results when made up into cells. 

 It is, however, somewhat troublesome to make and the process is a 

 rather slow one. 



A sample of mercurous sulfate, a so-called C. P. article, which 

 gave cells differing from the true value by nearly a millevolt, was 

 rubbed up with a lit.tle mercury and kept on a hot plate under di- 

 lute sulfuric acid for some hours. At the end of this treatment the 

 sulfate was crystalline and gave cells which agreed almost exactly 

 with those prepared from the electrolytically prepared sulfate. It 

 is easier to buy mercurous sulfate and purify it by the above 

 process than to prepare it by the electrolysis, and the product seems 

 to be as good. 



