Anderson. — Electrical Deposition of Nickel. 



503 



From the known value of the E.M.F. of the Weston standard cell that 

 of the composite cell could be calculated ; and, taking 0-613 as the P.D. at 

 the calomel electrode, it was possible to deduce the variation in the single 

 P.D. Ni-NiS0 4 at the cathode as deposition continued (figs. 2 and 3) in 

 the absence and in the presence of ammonium nitrate. 



Rate of Deposition.- — -It was noticed that when using the sulphate in 

 the ordinary manner 80 per cent, of the nickel was deposited during the 

 first hour of the electrolysis. The quantity of electricity and the time 



Fig. 1. 



B' — storage cells, giving a uniform fall of potential along the bridge wire XY ; 

 B' — adjustable resistance ; K' — key. 



B — battery connected to terminals of electrolytic cell M. By means of B, an 

 adjustable rheostat, the current as indicated by the ammeter A is main- 

 tained at a constant value. K — key. 



C — calomel electrode (N/10 KC1) dipping into connecting vessel N, containing 

 ammonium sulphate. A siphon, also containing ammonium sulphate, 

 serves to connect N and the electrolytic cell M, one arm being placed in the 

 immediate vicinity of the cathode. 



V — voltmeter placed across the terminals of the electrolytic cell M. 



E — Lippmann capillary electrometer ; T — short-circuiting key ; S — switch. 



W — Weston standard cadmium cell. 



necessary to remove the final traces of nickel from the solution are out of 

 all proportion to the amount of metal actually present. 



On the basis of Faraday's quantitative law, W = yqt (where W = weight 

 in grammes of metal deposited, y = current in amperes, r) = electro- 

 chemical equivalent of metal, t = time in seconds), the theoretical amount 

 of nickel was computed on the assumption of perfect efficiency, and on 

 comparison with the experimental values the working efficiency was found 

 to be 25-30 per cent. 



