ACCUMULATORS. 695 



If the electromotive force is 2'i volts, the disposable energy for 

 a kilogramme of lead is 



467,000 X 2'I 



= 100,000 kgm. 



9'8i 



The work of a horse-power-hour requires therefore that the 

 reaction takes place on 27 kilos, of lead. 



It is useful to make the same calculation for the zinc used in 

 batteries. The electrochemical equivalent of zinc being 33 x 0-01035 

 or 0-3416 mgr., the solution of a kilo, of zinc produces 



1,000,000 



= 2,927,000 coulombs. 



0-3416 



For an electromotive force of i'8 volts, as in Bunsen's element, the 

 disposable work is 



2,927,000 x i'8 



= 537, 



901 



For an equal weight, the zinc of Bunsen's batteries produces thus 

 5 times as much work as the lead of the accumulators. 



The acids and vessels which are necessary in both cases, and 

 the carbon of the Bunsen's element, must clearly be taken into 

 account. 



1251. The principal property of an accumulator, besides the 

 retention of its charge, is the quantity of energy which it can furnish 

 for a given weight. 



From experiments made by a Commission of the Exhibition,* 

 35 Faure's accumulators, arranged in series, and each weighing 

 43 "i kilos., gave a useful effect of 619,600 coulombs, with an 

 electromotive force of 2-1 volts per cell. The expenditure per kilo. 

 is thus 



619,600 



= 14,179 coulombs. 

 43*7 



* ALLARD, JOUBERT, POTIER, and TRESCA. Comptes rendus, Vol. xciv., 

 p. 603. 1882. 



