RICHARDS, COLLINS, AND HEIMROD. 



COPPER AND SILVER. 125 



even in large 



6. As usual, the speed of these reactions is increased hy increase of 

 temperature ; and moreover, the amount of cuprous sulphate which de- 

 termines equilibrium is greater in a hot solution than in a cold one. 



7. The addition of such substances as cane sugar, 

 amounts, produces no important effect, for obvious reasons 



8. The addition of much sodic 

 sulphate diminishes the action, evi- 

 dently by diminishing the number 

 of cupric ions present, according to 

 the law of mass action. In one 

 case the loss was diminished to half 

 its normal amount. 



Many of these conclusions are to 

 be found, either implicitly or expli- 

 citly, in the older accounts, but the 

 interpretation of the facts is now 

 more illuminating because of the 

 assistance of the dissociation hypoth- 

 esis. The only authority who denies 

 the solubility of copper in cupric 

 sulphate is Schuster,* whose experi- 

 ments involved only a very small 

 amount of solution, which evidently 

 required oidy unimportant amounts 

 of copper for its saturation. 



Foerster and Seidel have shown 

 that it is possible to dissolve copper 

 in a hot solution, and crystallize the 

 metal by cooling. With the same 

 idea in mind, we constructed an ap- 

 paratus somewhat different from 

 theirs, arranged so that this opera- 

 tion may take place continuously, 

 with the production of very pure 

 copper in beautiful minute crystals. 



Figure 1. — Apparatus for recrys- 

 tallizing Metallic Copper. 



A, steam-jacket for heating copper. 

 B, copper wires to be dissolved. C, re- 

 ceptacle for crystallized copper. D, cold 

 A ring-shaped tube was fixed in a bath. 



vertical plane, one side of the ring 



being surrounded by a steam-jacket, and the other by cool water. This 



arrangement naturally kept the liquid filling the tube in constant circula- 



* Proc. Roy. Soc, 55, 84 (1894). 



