162 ELECTROLYSIS. 



to it the quantity of hydrated oxide of copper which it 

 requires." 



M. Weil deposits all the metals, such as nickel, cobalt, 

 antimony, tin, &c., on cast iron, iron, and other metals. He 

 uses for this purpose alkalino-organic baths of an analogous 

 composition to that of his coppering bath, and the operation is 

 carried out by any of the three methods described for coppering. 



Some surprise may be created by the fact that M. Weil 

 treats the scouring of the pieces to be coppered as a matter of 

 small importance. Surfaces so irregular and heterogeneous as 

 those of rough forgings or castings cannot be scoured like the 

 copper surfaces intended for silver plating; and the experi- 

 menter knows that a coating never adheres or resists well if the 

 scouring is not well effected. However, notwithstanding this 

 little criticism, we cannot deny that this coppering system is 

 good, and that it is worked out with intelligence and profit. 



GAUDUIN'S PROCESS. M. Gauduin is the inventor of three 

 processes for coppering iron and cast iron ; the two- first being 

 based on the dry method, are out of the scope of our work ; the 

 third has been thus described by the inventor himself. 



" Many organic acids, and principally the polybasic organic 

 acids, tartaric, oxalic, succinic, citric, malic, and others pos- 

 sessing the same properties, are more or less suitable for the 

 production of a good deposit when they are combined with the 

 oxides of copper and the alkaline oxides in a state of double- 

 acid salts, as in bitartrates, bioxalates, quadroxalates, bisucci- 

 nates, bicitrates, alkaline bimalates, and with the corresponding 

 salts of copper with an excess of acid when they do not too 

 strongly attack iron. The operation is facilitated by a tem- 

 perature of 40 to 60 C. The use of an electric current pro- 

 duced by any given source is necessary when the coating is to 

 be of a great thickness. The manner in which this current is 

 used, as well as the preliminary scouring of the iron or of the 

 cast iron, do not require description, as these operations are 

 not possessed of any features special to this process. 



"Alloys of copper and tin, copper and zinc, copper and 

 aluminium (bronze, brass, aluminium bronze), can also, by 

 means of these baths, be deposited on iron, cast iron, and steel. 



