ELECTROTYPING. 



229 



ready for the warehouse. The gilding process is performed in the same 

 manner, a gold plate being substituted for the silver. 



ELECTROTYPING may be briefly explained as follows : Take two 

 vessels, A and B, and in one, A, put some dilute sulphuric acid and two plates, 

 one of zinc, Z, the other of copper, D, but be sure they are not touching each 

 other ; each of these plates must have a piece of wire fastened, by solder- 



34. Medico-galvanic Battery. 



ing, to their upper parts. In the vessel, B, put some solution of sulphate of 

 copper and a small quantity of dilute sulphuric acid, and attach another 

 copper plate to the wire which comes from the copper plate in the acid ; 

 this second copper plate is to be immersed in the solution of sulphate of 

 copper, and to the wire from the zinc plate is to be fixed the object to be 

 coated. If a medallion or other object in plaster, it should be soaked in 



Fig. 235.-- Battery in case. 



very hot wax and then brushed over with blacklead until the surface is per- 

 fectly blackened and bright ; the wire should be bound all round the margin 

 and soldered (as it were) with melted wax to the medallion, taking care that 

 this wax also is well coated with blacklead. If the object be now immersed 

 in the sulphate of copper solution and kept at a short distance from the 

 plate (it must not touch it), a coating of copper will soon cover the surface 

 and form a perfect cast, which, when of sufficient thickness, may be removed 



