NICKEL-PLATING . 119 



There results from the foregoing that, in order to operate 

 rationally without the trouble of having at every moment to 

 neutralise the baths, it would be best to have in the same vat 

 one portion of the anodes soluble and the other insoluble. 



With a sufficiently large number of anodes it is easy to 

 arrange them in such a manner that the acid layers of the 

 solution mix themselves intimately and by single contact 

 with the alkaline layers ; with a few anodes, on the contrary, it 

 will be useful from time to time to stir the solution so as to 

 obtain a bath regular in all its parts. It is therefore sufficient 

 to know the exact proportion of the two kinds of anodes in order 

 to suppress all the operations of neutralisation ; the best plan 

 is to determine this proportion by direct experiments, establish- 

 ing at the beginning twice as many insoluble electrodes as soluble 

 ones, as this is very nearly the suitable proportion for the equili- 

 brium between the two perturbations which we have mentioned. 



There then only remains the choice between platinum 

 and carbon for the insoluble anodes. Platinum is excellent, 

 but, as we have said, its price is so high that many manu- 

 facturers hesitate to incur the expense. We think that a 

 professional nickel-plater ought not to consider the expense, as 

 his cost of establishment, intelligently directed, should procure 

 him a saving of maintenance, expenditure, and time. Platinum 

 has the advantage of always preserving its weight and keeping 

 its value, and, finally, a series of platinum anodes does not 

 constitute an excessive expenditure compared to the cost of a 

 complete installation for nickel-plating. 



The use of carbon anodes entails the inconvenience of a main- 

 tenance of an elaborate kind ; the plates are, in time, eaten away 

 by the current ; they get weakened, cleaved, and finally crumble 

 into dust. This dust disturbs the bath, and, depositing itself on 

 the pieces to be plated, creates very disagreeable spots and un- 

 evenness. Some recent progress in the manufacture of carbon 

 plates may lead to the expectation that before long plates of 



is introduced into the acid bath. The bath is stirred continually, and dissolves 

 the exact proportion of the syrup required for remaining neutralised. The excess 

 of carbonate remains intact at the bottom of the bath, whence it can be extracted 

 by decantation or siphoning, so as to be used for another neutralisation. 



