ON THE 
HEAT EVOLVED 
DURING THE 
ELECTROLYSIS OF WATER. 
By JAMES P. JOULE, Esq. 
(Read January 24th, 1843. ) 
In former papers I have endeavoured to prove 
that the heat evolved by Voltaic Electricity is 
proportional to the resistance to conduction and 
the square of the quantity of current,—during 
electrolysis, and in the cells of the battery, as 
well as in metallic conductors. The heat, how- 
ever, which is liberated in cases of electrolysis, 
was very uniformly found to exceed the product 
of resistance and the square of the current; and 
I attributed this to the solution of oxide of zine 
and to other actions which are regarded as secon- 
dary. The circumstance is evidently of great im- 
portance to the whole subject of Voltaic Heat. I 
N 
