DEPOSITION OF VARIOUS METALS. 193 



It is boiled, and when hot submitted to the action of an 

 electric current with an antimony anode. 



We do not insist on the deposition of this metal, for it is 

 very little used in industry. 



DEPOSITION OF ALUMINIUM. 



M. A. Bertrand deposits aluminium by means of a solution 

 of double chloride of aluminium and ammonium. He asserts 

 that he obtains on a plate of copper a brilliant deposit capable 

 of receiving a beautiful polish. But his process, when tried by 

 a few chemists, has given nothing but results insignificant as to 

 quantities and disastrous as to quality. 



Mr. Urquhart obtains white deposits by using concentrated 

 sulphate of aluminium acidulated with a little sulphuric acid. 

 The temperature is about 65 C. The electromotive force 

 varies from 3 to 8 volts. Mr. Sprague declares that it is im- 

 possible to deposit aluminium, and one would feel inclined to 

 share his opinion after perusing the specification of the patents 

 taken out upon the subject as well as the notes communicated 

 from time to time to the scientific publications by clever ex- 

 perimenters. In any case, the deposition of aluminium is not 

 industrially practised, and has therefore only a secondary in- 

 terest for us, since we are considering the practical side of the 

 question alone. 



DEPOSITION OF CADMIUM. 



According to Smee it is difficult to obtain firm and coherent 

 deposits of cadmium from solutions of either its chloride or 

 sulphate ; but it can easily be deposited from a solution of the 

 ammonio-sulphate, prepared by adding sufficient aqueous am- 

 monia to a solution of sulphate of cadmium to redissolve the 

 precipitate. 



Napier recommends the following method: 

 A solution of cadmium is easily prepared by dissolving the 

 metal in weak nitric acid, and precipitating it with carbonate 

 of soda ; then washing the precipitate and dissolving it in 

 potassic cyanide. 



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