120 ELECTROLYSIS. 



artificial carbon, capable of resisting the action of the current, 

 will be sufficiently perfected to be advantageously used instead of 

 platinum anodes. As soon as this has become an accomplished 

 fact there will be no longer reason for using platinum anodes. 



The soluble anodes of nickel naturally grow thinner and 

 thinner ; they must be replaced before they are reduced into im- 

 palpable fragments, as there would be a risk of stopping an opera- 

 tion in full work, which is always detrimental to the coating. 



The suspension of the anodes in the bath should be effected 

 by means of nickel wires about two millimetres diameter, in 

 the shape of hooks ; if copper wires were used, care should be 

 taken not to completely immerse the anodes in the liquid, as 

 any portion of the attachment which is immersed in the bath 

 would get dissolved with the anode. 



The vats should be of such a depth that the pieces to be 

 plated should not, when completely immersed, reach, at a 

 maximum, more than the two-thirds of their depths. 



In principle, the pieces to be plated should never be 

 immersed in the bath when the electric current is not acting, 

 as otherwise the surface of the pieces might be slightly 

 attacked by the bath, and an oxidation might arise which 

 would prevent the close association of the coating with the 

 underlying metal. 



It is a generally acknowledged fact that the nickel bath 

 with soluble anodes and iron pieces, for example, develops a 

 secondary current which runs in a contrary direction and 

 reduces the strength of the main current ; it may even occur 

 that the latter may be counterbalanced, destroyed and re- 

 versed by polarisation, which action interrupts or destroys the 

 deposition of nickel. It is, therefore, important to use a 

 sufficient electromotive force of current, and to be careful that 

 the current always travel in the same direction. To that effect 

 a galvanometer should always be inserted in the circuit, as it is 

 the only means of really ascertaining what takes place in a 

 bath. With the help of that instrument, not only will the 

 inconvenience of a reversal of the current be avoided, but also 

 the irregularity in the thickness of the deposit. At the time 

 of starting, the position of the hand should be observed, 



