CHAP. IX.] 



ELECTRO-PLATING. 



7i3 



on a metal sash which communicates with the negative pole of 

 the electric battery. Another sash, insulated from the first, carries 

 rods to which are hung the sheets of gold or silver forming the 

 soluble anodes. 



The force of the current must be regulated so a's to' give a per- 

 fectly adherent deposit. The thickness of the layer deposited depends 

 in other respects on the duration of the operation. By weighing the 

 cleaned objects before putting them into the bath and weighing again 

 after they come out, the exact weight of the precious metal deposited 



FTG. 460. Compound apparatus for gold and silver electro-plating. 



can be ascertained, and thus the thickness of the gilding and silvering 

 be determined. 



An apparatus may even be employed which automatically regulates 

 the continuance of the operation when it is required to cover the 

 objects with a determinate weight of the precious metal, gold or silver. 

 This apparatus, invented by Roseleur, is simply a balance arranged as 

 indicated in Fig. 461. 



On the left is seen the apparatus placed beneath the beam, so that 



