204 ELECTROLYSIS. 



1st. One gramme of copper was dissolved in nitric acid 

 and completely transformed into a sulphate. Three hours and 

 fifteen minutes were required for depositing it with insoluble 

 platinum anodes. 



2nd. One gramme of silver, transformed into a sulphate and 

 submitted to the action of the same current with an anode, also 

 insoluble, was completely deposited in one hour. 



3rd. Finally the same experiment took place with 1 gramme 

 of copper and a soluble anode ; 1 37 gramme was deposited in 

 one hour, an amount which corresponds to 1 gramme in forty- 

 three minutes. 



It may be concluded from the foregoing, that in the con- 

 ditions under which M. Mascart operated, the use of insoluble 

 anodes requires, for effecting the sarnie deposition, a current, 

 or, what amounts to the same, an electromotive force four 

 times greater than that of soluble anodes. We shall see that 

 this proportion of 1 to 4 has nothing definite, and that the use 

 of insoluble anodes always entails a considerable expenditure 

 of current. 



INSTALLATION AT FRANKFORT. M. Andre, of Frankfort, 

 has for some years carried out refining operations by means of 

 Gramme machines. We do not believe that his processes, 

 although ingenious, are used in practical installations. 



His system was based on the electrolytic extraction of metals 

 from mattes, speisses, &c., containing some nickel, cobalt, and 

 copper, and on the introduction of a frame containing metal 

 shots between the anode and the cathode. When a metal con- 

 tained in an alloy is precipitated by electrolysis, the most 

 positive metal contained in the frame precipitates a metal of 

 the solution used. 



The inventor also used conical revolving cathodes in order 

 to avoid the polarisation. 



M. Andre used sulphate of ammonium for the simultaneous 

 precipitation of copper and nickel ; dilute sulphuric acid for 

 the separation of metals in old coins, and sodic chloride for the 

 extraction of tin in old tin wares. 



In the electrolysis of old coins the coins themselves were the 

 anodes. Between the anodes and the cathodes a frame, covered 



