110 ELECTROLYSIS. 



In this, as in all other electro-plating operations, each 

 country, and often even each manufacturer, have their own 

 individual method. 



These methods, however, only differ in certain details, and 

 can be combined at will by the operator, according to the 

 nature of the pieces to be plated and the degree of perfection 

 which it is desired to obtain. 



The following are indications formulated by a few experi- 

 menters. 



Watt's Method. All the pieces to be nickel-plated must be 

 first dipped in a solution of caustic potash. As this solution 

 grows weaker and weaker it must be continually revived or the 

 pieces must be immersed during a longer time. Steel, iron, 

 and brass can remain in the solution until the time of rubbing 

 them with pumice-stone before they are put into the bath. 

 Tin, Britannia metal, and pieces soldered by means of tin, must 

 remain only a few minutes, as potash attacks those metals. 



The pieces must be polished before being put in the bath, 

 because it is more easy afterwards to polish the nickeled sur- 

 face. 



The polishing is done by means of a cylinder covered with 

 a piece of tanned walrus skin or of ox-neck leather, &c., and 

 very fine sand. The piece is then put through a second polisher 

 and finished with finely pulverised lime. For steel and iron a 

 small emery wheel or a leather wheel coated with emery and 

 oil is used, the finishing process being the same as above. 



Brass, after being polished, must lie for some time in the 

 potash bath ; it is afterwards dipped in a moderately concen- 

 trated solution of potassic cyanide, and, after a good rinsing, 

 rubbed with a hard brush and pumice-stone, or with fine 

 powdered brick. It is washed again, then redipped in potassic 

 cyanide, rewashed and placed in the bath. It must be ascer- 

 tained that the piece gets entirely covered after immersion ; 

 this is an essential condition of success. The pieces should not 

 be manipulated with bare hands, but by means of an inter- 

 mediary wet cloth. 



Pfanhauser's Method. Manufacturers who have no practice 

 in electro-plating readily believe that rough metallic surfaces 



