62 Gooch and Beyer — Electrolytic Estimation of Lead. 



the final washings made with water, and the deposit weighed 

 after drying at 200°. The time required for the complete 

 deposition of 0*15 grm. of lead dioxide under the conditions 

 described is about two hours. 



The Determination of Manganese. 



For the electro-deposition of manganese as the dioxide 

 various processes have been described.* With stationary 

 electrodes solutions containing nitric acid, sulphuric acid, 



Fig. 2. 



* 



J 



acetic acid, formic acid with or without a formate, or ammo- 

 nium acetate alone, with chrome alum, or acetone, have been 

 employed. For use with the rotating anode, solutions contain- 

 ing ammonium acetate with chrome alum or alcohol have 

 been advocated. f In all these processes hydrated manganese 

 dioxide is deposited upon a large anode which is preferably a 

 roughened platinum dish of considerable capacity. 



The experiments to be described have been made to test 

 the utility of the electrolytic filtering cell in the determination 

 of manganese as the dioxide. The procedure adopted was the 



* Smith's Electro-analysis, edition of 1907, p. 134 et seq. 

 f Koester, Zeitsclir. Electro-chem., x, 553, 1904. 



