234 



ELECTROLYSIS. 



form a scoria which is treated by hot water ; the sodic arse- 

 niate dissolves, and it is crystallised ; the sodic antiraoniate 

 is reduced by the fire ; the iron and copper which it may contain 

 are not reducible. 



The actual treatment of the base bullion by the dry method 

 costs about 30 francs per ton ; Professor Barker, of Philadelphia, 

 estimates that by using the Keith process the cost would not 

 exceed 10 francs. The saving would, therefore, amount to 20 

 francs per ton. Dr. Hampe, speaking on this process, records 

 the fact that the lead deposited upon the cathode is not 

 absolutely pure, and contains in particular a certain proportion 

 of bismuth. The following are the results which he has ob- 

 tained when electrolysing 6 litres of plumbic acetate containing 

 77*92 grammes of lead per litre, and acidulated with 4 per 

 cent, of acetic acid. 



The surfaces of the electrodes were 13,000 square milli- 

 metres. 



In his pamphlet, Mr. Keith says that his cost price will be 

 still more reduced, as Mr. Weston has undertaken to supply 

 him with a dynamo-electric machine for 1000 francs (40Z.), 

 which will precipitate 40 tons of lead in twenty-four hours. 

 We have seen previously that 10 tons in twenty-four hours re- 

 quired 12 horse-power, the power required for this machine for 

 40 tons will therefore be 48 horse-power. But we know by 

 experience that such a dynamo costs to the manufacturer at 

 least 7500 francs (300Z.), exclusive of general expenditure. Mr. 



