DEPOSITING BY SEPARATE BATTERY. 



65 



protect it from the action of the atmosphere ; but they should also 

 be protected by a glass, which may be fixed on in the manner 

 pointed out in another section. The most successful operators that we 

 have known in this and in every other department of electrotyping 

 are Dr. Thomas Paterson, of Glasgow, and Mr. Bawtree, of London. 



Depositing by separate Battery. Having described, so far as we 

 know them, the best and most simple means of obtaining moulds, 

 and their preparation for receiving the deposit of the metal, we 

 return again to the management of solutions and batteries, and 

 the application to other metals besides copper. 



Though in our account of the porous, or single cell system (page 

 47, we have recommended it as the best and most economical for 

 electrotyping, still many eminent electro-metallurgists prefer using the 

 battery system; and indeed there are solutions of copper and of other 

 metals to which the porous cell system cannot be applied, from the na- 

 ture of the solution and the necessity of intensity to decompose them. 



While depositing upon a mould by the single cell, let the wire 

 which connects them be cut in the middle, and a mould be attached 

 to the end of the portion remaining upon the zinc plate, and a small 

 plate of copper to the end of the wire remaining upon the mould in 

 the copper solution, and let these two be put into a second vessel 

 containing a solution of sulphate of copper. The action between the 

 zinc and medal in the double or first cell will go on as before 

 namely, the electricity passing through the porous cell and the 

 solution to the medal; but on returning to the zinc it must pass 

 through the copper solution, which is in the second vessel, between 

 the moul$ and copper plate, where it produces the same effects as 

 in the first cell. The sulphuric acid is liberated at the copper plate 

 and dissolves it, and the copper is deposited upon the mould, so that 

 the solution in this cell is maintained at one strength : hence there is 

 no necessity for hanging crystals of sulphate of copper in this solution. 



It will be observed, 

 that the electricity having 

 to pass through a second 

 solution, is made to per- 

 form double duty, and 

 must consequently be 

 much more economical. 

 We found the results to 

 be these: A single cell, 

 with a mould, was placed 

 two inches from the 

 porous cell, and of the same size as the zinc plate, and another, 

 similarly arranged, but connected with a metal mould and copper 

 plate of similar size to the zinc and copper, was placed one inch 



F 



