298 



REPORT — 1898, 



about 60° C. After the current has passed through the mixture for three 

 minutes, the solution is acidified with tartaric acid, and kept acid through- 

 out the operation by the addition of a G per cent, solution of tartaric acid. 



Wagner recommends that the hot solution should be electrolysed with 

 a current of 0-2 ampere for fifteen minutes ; 5 c.c. of 6 per cent, tartaric 

 acid solution are added and the current density increased to 0-5 ampere. 

 The addition of the acid is repeated at intervals of fifteen minutes. 



In the following experiments Wagner's directions were followed, with 

 the exception that the tartaric acid was slowly added from a burette 

 instead of in quantities of 5 c.c. A large excess of acid is to be avoided, 

 and its addition should not be continued up to the end of the operation. 

 The current is continued until the mixture has a neutral or feebly acid 

 reaction, in order to pi'event a small quantity of the acid tartrate of potas- 

 sium or ammonium separating out. 



Bright, firmly-adhering deposits were obtained. 



In experiments 1 to 6 potassium oxalate was used ; in 7 and 8 ammo- 

 nium oxalate was employed. In 5, G and 7 the mixture was strongly acid 

 when the electrolysis was stopped. 



V. — Deposition ^rom Solution in Potassium Cyanide. 



The solution is neutralised if necessary with potash, and a 20 per cent, 

 solution of potassium cyanide is added until the precipitate redissolves. 

 A large excess of cyanide is to be avoided. 



A bright film is obtained which leaves a small quantity of black 

 deposit undissolved when treated with acid. The re.sidue collected from 

 several analyses proved on examination to be carbon. The presence of 

 carbon no doubt accounts for the high results obtained. The platinum 

 electrodes are attacked by the cyanide in this and in the following 

 process. 



