REFINING OF COPPER AND LEAD. 233 



cess is the Electro-Metal Kefining Co., of New York ; its capital 

 is 2,500,000 francs (100,000*.). 



The lead to be refined is melted in plates, and these are 

 suspended to metallic cross-bars connected with the positive 

 pole of a magneto-electric machine ; between these plates are 

 placed cathodes of pure lead connected with the negative pole. 



The bath is a solution of plumbic sulphate in sodic acetate. 

 The metals acting as positive towards lead, such as iron and 

 zinc, remain almost entirely in the solution, and are pre- 

 cipitated in a state of oxide only, easy to separate when the 

 metal is being melted afresh. 



The plumbic sulphate is decomposed by the action of the 

 current, the lead going to the cathode and the acid on the 

 anode, where it dissolves the lead, the iron, and the zinc of the 

 metal to be refined. The gold, the silver, and the antimony 

 remain on the anode, where they are gathered in muslin 

 bags. 



The following are, according to Mr. Keith's experiments, the 

 results obtained when operating on a few tons of base bullion. 



With 48 wooden vats, containing each 50 plates of base 

 bullion weighing 16 kilogrammes each, and 12 horse-power, the 

 production reaches 10 tons per 24 hours. 



The plates are of the following dimensions : 



Length 1*22 metre. 



Width 0-38 



Thickness 0'003 



This is the composition of the lead before and after re- 

 fining : 



Before refining. After refining. 



Lead 96 '36 per 100 99 '9 per 100 



Silver 0'5544 0-000068 per 100 



Copper 0*315 O'O 



Antimony .. .. 1'070 traces 



Arsenic .. .. 1*22 traces 



Zinc, iron, &c. .. 0'4886 O'O 



The sediments gathered in the muslin bags are dried 

 and melted in a crucible, with sodic nitrate and borax. The 

 silver remains in a metallic state ; the arsenic and antimony 



