52 ELECTROTYPE PROCESSES. 



Copper. Zinc, 



deposited dissolved, 



oz. dwt. oz. dwt. 



M , u . (24 hours . 12 9 12 17 



21b. common salt in one U hours . 17 13 20 17 



gallon of water ( 60 hours . 24 15 34 3 



-> , , . . . (24 hours 9 13 9 18 



21b.sulphateof zinc m one ^ 48hours 16 4 17 10 



gallon of water J 60 hours . 23 10 24 8 



lib. sulphuric acid to 24 J 24 hours . 15 17 17 15 



of water (48 hours . 27 16 32 3 



From these results it is evident that the best and most economical 

 manner of treating the solution and the zinc would be to renew the 

 solution every 24 hours, as the second 24 hours does not give half 

 the deposit of the first 24 hours without renewal. 



The next series of experiments was with the same zinc and the 

 same kind of solutions, but the zinc was taken out every 24 hours, 

 and brushed, but not re-amalgamated, and put back again with new 

 solution in the porous cell. 



Copper Zinc 



deposited. dissolved, 

 oz. dwt. oz. dwt. 



Salt and water . 4 days of 24 hours . 49 16 51 8 

 Sulphate of zinc . 4 days of 24 hours . 47 14 48 9 

 Acid and water . 3 days of 24 hours . 48 13 53 7 



These results give the most ample reply to the question so often 

 put, and will guide the manufacturer as well as the student in his 

 operations, whether time or material be .of the greatest consequence 

 to him, and who must be regulated by the circumstance. 



We may remark that the sulphate of zinc solution does not require 

 renewal, but simply that we half empty the cell and refill it with 

 water. The sulphate of zinc poured out being nearly saturated, 

 may be crystallized, and will serve other electro-metallurgical 

 operations. 



Making of Moulds. The directions given for obtaining a mould 

 from a penny piece, by deposition, are applicable to taking moulds 

 from any metallic medal, engraving, or figure, that is not undercut ; 

 and for depositing within the moulds so produced. On the first 

 discovery of this art, the electrotypist was confined to metallic 

 moulds, as the deposition would not take place except upon metallic 

 surfaces ; but the discovery that polished plumbago, or black lead, 

 had a conducting power similar to that of metal, and that the deposit 

 would take place upon its surface with nearly the same facility as 

 upon metal, freed the art at once from many of its trammels, and 

 enabled the operator to deposit upon any substance wood, plaster 



