CHAP. IX.] 



ELECTRO-PL A TING. 



717 



Gold and silver are not the only metals which are applied in thin 

 layers by electricity. Deposits can now be obtained of platinum, 

 tin, iron, and nickel by employing suitable solutions of these metals. 

 For platinum, a solution of the double phosphate of platinum and 

 soda is used. Objects of iron are plated with tin in a bath of 

 pyrophosphate of soda and protochloride of tin. Lead and zinc can 

 be galvanized in the same way. 



FIG. 463. Workshop or copper electro-plating in Oudry's manufactory. 



An important application of electro -plating consists in covering 

 copper-plates with iron. The surface of the engravings thus acquire 

 a durability which preserves them from all alteration during printing. 

 When the thin coating of iron thus deposited is worn out and the red 

 tint of the copper-plate beneath is visible, a fresh coating of iron pre- 

 vents any further alteration. 



Another recent industry, based on the same processes, has acquired 

 in the hands of its inventor, M. Oudry, considerable development. It 

 consists in covering objects of great dimensions, such as vases, statues, 

 candelabra, &c. ; with copper. Among the practical difficulties to be 



