140 ELECTROLYSIS. 



then rubbed with a brush and some Spanish whiting, dipped 

 into cold water, and put in the sawdust box No. 1 (bath No. 

 10 is composed of dilute sulphuric acid; bath No. 11 is com- 

 posed of sulphuric and nitric acids with a small quantity of 

 sodic chloride). 



2. Polishing. After being dried in sawdust, the sheet of 

 zinc is nailed, by means of two suitable nails, to a board of the 

 same size, and polished by machine a, the brush being sprinkled 

 with saffron. 



When the sheet is very bright and without scratches or 

 spots containing traces of oxide, it is cleansed. 



3. Cleansing. Although very bright, the surface of the 

 sheet of zinc contains a certain quantity of oil which must 

 absolutely be removed. In order to obtain this result, the 

 sheet is rubbed with some rags impregnated with benzine, 

 then passed through sawdust, and dipped into bath No. 2, 

 giving it a to and fro motion. It is then brushed with Spanish 

 whiting and freely washed. These last operations must be con- 

 ducted with great care, as the surface to be nickeled must not 

 be touched with the hand. 



4. Coppering. The sheet, held by its hooks, is immersed in 

 the coppering bath No. 5 during the space of twenty or thirty 

 seconds, then taken out and successively dipped into No. 6 hot- 

 water tub and No. 9 cold-water tub. 



5. Nickeling. The sheet is then passed through the nickel 

 bath No. 13, where the deposition ought to be effected in five 

 minutes. The nickel anode is placed very close to the sheet of 

 zinc. The sheet is then taken out and dried. 



6. Final Polishing. The nickel-plated sheet is fixed to a 

 board and submitted to the action of brushes b or c. As soon 

 as it is sufficiently polished, it is passed through the cold 

 sawdust, then through the benzine, and finally through the hot 

 sawdust. 



When the sheets are finished, they are piled so that the 

 rough faces touch each other, a layer of thin paper being 

 intercalated between the nickeled surfaces. 



Powell's Process. Mr. Powell (of Cincinnati) has a special 

 method for obtaining nickel deposition ; instead of using 



