Warwick.] 



114 



MANGANESE (DETERMINED ELECTROLYTICALLY). 



[Nov. 



The platinum dish was made the anode, the wire spiral serving as the 

 negative pole. With small quantities of free acid, (1) and (2), consider- 

 able peroxide of manganese, separated on both poles, with larger quan- 

 tities, (3) (4), only very slight traces were found on the kathode. The 

 deposition in (4) was not complete. The peroxide formed a black, lus- 

 trous coating on the dish, adherent while moist, but scaling off upon being 

 heated. 



The manganese which separated on the kathode was removed by means 

 of a small piece of filter paper, which was ignited and the ash added to 

 the contents of the dish, which was then raised to an intense heat in 

 order to convert the peroxide of manganese into Mn 3 O 4 , in which form 

 it was finally weighed. Traces of Mn were found in solution (3;. 



ELECTROLYTIC SEPARATIONS. 

 CADMIUM FROM MANGANESE. 



In the preliminary experiments on manganese alone, it was found that 

 the presence of 20 c.c. of free acid was sufficient to prevent the deposition 

 of any peroxide on the kathode, except in the very slightest traces ; but 

 the presence of cadmium in the solution seemingly had a contrary effect, 

 as the presence of even 40 c.c. of acid failed to prevent the separation of 

 traces of manganese on the negative pole (7). In (5), to which 5 c.c. of 

 free acid had been added, the deposit of peroxide of manganese upon the 

 negative pole was almost five times greater than in a solution of manga- 

 nese to which no cadmium had been added, all the other conditions being 

 the same. In all the above experiments the platinum dish was used as 



