Manchester Memoirs, Vol. I. (1906), No, 13. 5 



HNO3 reduced to 

 NH3 in 45 minutes. 



*Lead kathode ... ... ... ... 0*22 grm. 



Zinc ,, ... ... ... ... o"2i ,, 



Graphite „ ... ... ... ... o'lo ,, 



This shews that the rate of decomposition was about 

 the same with lead and zinc kathodes, whilst the graphite 

 kathode only exerted about one half the reducing action. 



Influence of \ c.c. HNO on the detection of arsenic in the 

 form of AS2O5, by the electrolytic apparatus when 

 using kathodes of different substances. 



A solution was prepared containing O'O0O,O0O,83 grms. 

 of AsjOg in each cubic centimetre, i c.c. is equivalent to 

 yjjVgth of a grain of As^Oe per gallon when using 50 c.c. 

 of the liquid; 10 c.c. of this solution were mixed with 

 \ c.c. of HNO3 and introduced into the apparatus, using 

 kathodes of different substances. The kathodes used 

 were graphite, lead, cadmium, zinc, and iron. 



After the current (3 amperes) had run for 45 minutes 

 the arsenic mirrors obtained were approximately equiva- 

 lent to the following c.c. of the standard solution : — 



(The mirrors obtained when HNOa is present are very 

 irregular, and only admit of an approximate estimation. 

 In each case the number of c.c. is given as the nearest 

 whole number, and the figures represent averages from a 

 number of experiments.) 



c.c. of standard 

 solution. 



Graphite ... ... ... ... ... i"o 



60 



tLead 

 Cadmium.. 

 Zinc 

 Iron 



2"0 

 4-0 

 2"0 



• This lead kathode was made and kindly given to me by Mr. J. E. 

 Hackford, of Nottingham. The lead u.sed having been purified from traces 

 of arsenic and antimony by him by fusing with sodium, and afterwards stirring 

 up with pure fused sodium chloride while the lead is still at a high temperature. 



t Another lead kathode made by ourselves gave practically the same 

 result, although the results shewed some difference. 



