igos-] KOLLOCK-SMITH — ELECTRO-ANALYSIS. 13^ 



[Contribution from the John Harrison Laboratory of Chemistry.] 



THE USE OF THE ROTATING ANODE AND MERCURY 

 CATHODE IN ELECTRO-ANALYSIS. 



BY LILY G. KOLLOCK AND EDGAR F. SMITH. 



( Read April 13, iqos- ) 



First Paper. 



Several investigations made in this laboratory have shown that 

 when in electro-analysis the anode is rotated high currents can be 

 used and metals be precipitated completely in very short periods 

 of time ; further, by the use of mercury cathodes most interesting 

 determinations and separations of metals are possible. 1 In the 

 latter case, however, the anode has been stationary, and the elec- 

 trolyte consequently not agitated. Then, of course, the precipi- 

 tation of the metal has been comparatively slow. Observing 

 the splendid results got with the rotating anode, when platinum 

 was the cathode, we determined to use a combination of rotating 

 anode and mercury cathode. This was accordingly done, and in 

 some preliminary trials made last August (1904), the results of 

 which were briefly alluded to in a communication published in 

 the Jour. Am. Chem. Soc, 26, 16 14, mention was made that 

 0.4810 gram of copper could be precipitated in twenty-five 

 minutes, and that this success could be had with other metals. 

 Since then we have made additional experiments which we desire 

 to record here. Not only is the time factor reduced for the metals 

 studied, but the plan of combining a mercury cathode with the 

 rotating anode gives an inexpensive form of apparatus which will 

 eliminate the platinum dish, cone or cylinder from electro-analysis 

 and thus remove an expensive factor. 



Apparatus. — The decomposition cell is a tube 3.5 cm. in 

 diameter and 7.5 cm. in height, made from a test tube. Soften 

 the bottom of the tube in a blast lamp flame, then push through it 

 a platinum wire two centimeters in length, so that its end projects 

 0.5 cm. into the tube. Flatten the bottom of the tube on an 

 asbestos plate and anneal it in the ordinary way. 



x Jour. Am. Chem. Soc, 25, 884: 26, 1 124. 



