NICKEL-PLATING. 



123 



objects to be coated ; this vigorous action must cease as soon as 

 the surface is completely whitened. The current is then re- 

 duced, and continued until a few bubbles of gas are seen to 

 ascend to the surface of the bath. 



According to the thickness of the deposit which it is sought 

 to obtain, the pieces must remain from five minutes to a 

 few hours in the bath. During the operation, care must be 



FIG. 20. 



Arrangement of the Anodes and Cathodes. 



taken to ascertain that the coating takes place everywhere, and 

 that certain parts are not black or rough. In the latter case, 

 the pieces should be at once taken out of the bath and the 

 defective parts rubbed with polishing powder, or in the lathe 

 with a steel wire scratch brush, and the current should be 

 reduced to avoid a repetition of the defect. 



An excellent precaution is to frequently stir all the objects 

 placed in the bath. M. Pfanhauser recommends the operator 

 to unceasingly stir his bath so that the latter should not be still 

 for one instant. It is perhaps going a little far, but it is easy 



