ELECTROTYPE PROCESSES. 



Single-Cell Operations. We shall now proceed to detail the pro- 

 cess of electrotyping, the materials for which are of the most 

 simple nature. Let us suppose that the object of the student is 

 to copy a copper medal for example, the side of a penny-piece. 

 Dissolve a quantity of the crystals of sulphate of copper in any 

 convenient vessel ; if distilled water can be had, the better. This 

 is conveniently done by suspending the crystals in a coarse cloth 

 on the surface of the water, or the crystals may be put into the 

 water, and well stirred till dissolved: crushing the crystals facili- 

 tates their solution. The water should be kept cold and be fully 

 saturated with the salt, and the solution allowed to stand untouched 

 for several hours. This last precaution is not always essential, but 

 only necessary when the copper solution is not perfectly clear and 

 transparent. 



The sulphate of copper of commerce has often a large quantity 

 of iron in it, a portion of which becomes per-oxidized, and will pre- 

 cipitate or fall to the bottom of the solution on standing ; indeed, 

 when it is known that the salt contains much iron, it is best to 

 crush the salt very fine, and expose it to the air for some tune ; 

 when dissolved, after this exposure, a great quantity of iron will 

 settle at the bottom of the solution, which should be carefully 

 decanted and the last portion filtered. The clear solution should 

 now have about one-fourth of its quantity of water added to it, as 

 a completely saturated solution is not the best. A newly-formed 

 solution does not deposit so freely as one that has been in use for 

 some time. The addition of a few drops of sulphuric acid, or, what 

 we have found better, a little sulphate of zinc about one ounce 

 to the pound of sulphate of copper improves the condition of a 

 new solution. 



Next, put the solution of sulphate of copper into the vessel in- 

 tended for use, say it is a large jelly-pot, in which let a vessel of 

 unglazed porcelain (porous vessel) be placed, filled to within half 



