SILVER AND GOLD PLATING. 143 



This is no proof that nickel-plating has attained a commercial 

 development to be compared with that of silver-plating far from 

 it ; if the silver-plating establishments are few, they are 

 nearly all of considerable importance, whereas the nickel- 

 plating establishments are generally installed for operating on 

 a small quantity of nickel at a time. 



" One single silver-plating establishment in Paris," said M. 

 Bouilhet before the Congress of Electricians, " that of Messrs. 

 Chri^tofle & Co., annually deposits more than 6000 kilogrammes 

 of silver, and since the date of its foundation in 1842, it has 

 not used less than 169,000 kilogrammes of silver deposited upon 

 an incalculable number of objects, at a thickness suitable and 

 sufficient for insuring to each object lasting properties ap- 

 propriated to the use for which they are intended. 



" The average thickness of these deposits is that which corre- 

 sponds to 3 grammes per square decimetre, or 300 grammes 

 per square metre. You will therefore see that the surface 

 which this factory alone has covered with silver is not less than 

 563,000 square metres, over 56 hectares (140 acres.) 



" I am only giving you here the work of one single factory ; 

 but from certain authentic information which we have been 

 enabled to gather, we estimate at 25 tons the yearly quantity 

 of silver used in Paris alone for silver-plating purposes. 



" We have no analogous documents giving us means of ascer- 

 taining with the same degree of approximation what are the 

 quantities of silver used in electro-deposition by other countries; 

 but if we estimate their producing powers which are well known, 

 and compare them with our own, it is not rash to suppose that the 

 quantity of silver annually deposited by electrolysis in Europe 

 and America can be computed at 125,000 kilogrammes (125 

 tons), which represents an intrinsic value of over 25 millions of 

 francs (one million sterling)." 



Composition of Silver Baths. The various authors which 

 we have consulted upon the subject do not all agree upon the 

 question as to the best composition of a silver bath. Watt 

 recommends a solution of argentic nitrate, or a solution formed 

 by an electrolytic deposit of silver in potassic cyanide ; JRose- 

 leur, a dilute mixture of argentic and potassic cyanide; 



