Thomson, Notes on Arsenic. 



It is remarkable that the arsenic acid was reduced by 

 each of the different kathodes to the condition of arseniu- 

 retted hydrogen in presence of nitric acid or some nitrous 

 compounds, some of which remained intact after the 

 experiment, and that lead was the most efficient. 



Influence nf different kathodes on arsenious acid. 



For this series of experiments a standard solution 

 was prepared containing 0000,000,715,4 grm. of AS4O6 

 per c.c. I c.c. is equivalent to yoVoth of a grain per gallon 

 when working on 50 c.c. of the solution, and 10 c.c.'s of 

 the standard solution were used for each experiment, which 

 was carried out during 45 minutes, in each case with a 

 current of 3 amperes. 



The mirrors obtained during 45 minutes were equiva- 

 lent to the following c.c. of the 10 c.c. of the standard 

 solution taken — the mirrors obtained with a pure zinc 

 kathode during 45 minutes being taken as the standard : — 



Graphite 



Lead 



Cadmium 



Zinc 



Iron 



c.c. of standard 

 solution. 



9 

 10 



3 

 10 



Influence of different kathodes on arsenic acid solution. 



Each c.c. of the standard solution used contained 

 0"000,ooo,83 grm. AsoOj (=TTro7th of a grain of arsenic 

 trioxide per gallon when using 50 cc). 



The experiments were made as before with 10 c.c. of 

 standard solution, and the time and electrical current as 

 above mentioned. The resulting mirrors obtained were 

 as follows in equivalents of c.c. of the standard arsenic 

 trioxide solution : 



