NICKKI.-I'I.AI I 121 



and tlii- current regulated in such a manner that the position 

 of the said hand should vary as little as possible during the 

 tinio the operation lasts. 



The anodes and the pieces to be plated should not be too 

 near each other in the bath. The distance should be regulated 

 according to the profiles of the pieces ; when the surfaces are 

 nearly flat, 10 centimetres distance will be sufficient ; with 

 pieces having deep cavities and comparatively large reliefs, a 

 space of 15, 20, and even 30 centimetres should be left between 

 the anode and the piece to be plated. 



SURFACE OF THE ANODES. Certain operators recommend 

 that the anodes should be of the same surface as that of the 

 pieces to be coated ; some others insist on the use of much 

 larger anodes. The latter are right, especially when the in- 

 stallation is a small one, or the number and size of the pieces 

 to be plated is very irregular. Contrarily to the solutions of 

 gold and silver, the nickel solutions do not easily dissolve the 

 anodes, and if a very large surface of anodes is not used the 

 deposit is localised and its colour is dull. 



If it is proposed to act on large spherical or cylindrical 

 objects, it is found suitable to arrange all round the surfaces to 

 be plated a series of anodes connected together so as to obtain 

 a homogeneous deposit on all the parts on which it is to be 

 effected. When batteries are used for producing the electric 

 current, it is necessary that the total surface of the pieces 

 suspended in the bath should be approximately equal to the 

 surface of the zinc of the cells used. 



Mr. Sprague gives as a maximum 85 square decimetres of 

 surface of anode for every 100 litres of solution of nickel. M. 

 Perille does not in practice exceed 40 square decimetres for the 

 same capacity of bath. 



Modus Operandi. Before describing the mode of conduct- 

 ing the electrolytic operation, we beg to give the experimenter 

 one further piece of advice. As soon as the pieces have been 

 dipped into the potash bath, they must not be touched any more 

 \vith the hand. A hook specially disposed, and the copper wire 

 surrounding the pieces, allow of their being turned about, 

 displaced, suspended, &c. It is only after they have been taken 



