102 ON THE HEAT EVOLVED DURING 
We have given 1°35, 1:131, and 2°188 as the 
intensities due to the separation of gaseous oxy- 
gen from hydrogen, copper, and zinc: and the 
quantities of heat corresponding to these are res- 
pectively 8°27, 6°93, and 13°41, which are 
therefore the quantities of heat per tb. of water, 
which, according to the above data, should be 
evolved by the combustion of 1 gr. of hydrogen, 
31:6 grs. of copper, and 33 ers. of zinc. To the 
first of these, however, about one sixteenth (p. 93) 
ought to be added, on account of the dissolution 
and re-combination of the gases in the electrolytic 
cell, which has the effect of diminishing the num- 
bers of column 11. On the other hand, the re- 
sults for copper and zinc are certainly somewhat 
over-stated, on account of that species of resis- 
tance to electrolysis which forms column 10. The 
error thus arising is not indeed great, and in the 
case of copper, is, as I have ascertained, no more 
than 0°13; but nevertheless it ought to be elimi- 
nated, as decidedly as we eliminated, in the case 
of water, the resistances of column 10. After 
making these corrections, the above quantities of 
heat are altered to 8°79, 6°14, and 12°°62, which 
approximate pretty closely to 8°98, 5°18, and 
10°98, the quantities of heat which Dulong 
