637 
varies at changing temperature. The dependence on the temperature 
is expressed by vaN ’r Horr’s well known expression: 
dln ae E 
ee 
in which A represents the constant of equilibrium, 7’ the absolute 
temperature, £ the energy of conversion, and F the gas constant’). 
If one wants to apply this equation to definite cases, it must be 
integrated; for this purpose we should know / as function of the 
temperature. 
If one takes a constant for /, in other words if the change of 
energy in the reaction is independent of the temperature, if therefore, 
the sum of the specific heats of the substances of the first member 
of the reaction equation is equal to that of the substances of the 
second member, we get by integration of equation 1 an expression 
of the form: 
nK= tots. eee ee 
in which « and 6 represent constants. 
If we assume that the algebraic sum of the specifie heats of the 
reacting substances is not zero, as was supposed in (2), but has a 
value that does not vary with the temperature, the change of energy 
is linearly dependent on 7’; then equation 1 gives on integration: 
Km dgtl $e, ne U 
in which a, 6, and ¢ indicate again constants. 
If the specifie heats vary linearly with 7, we obtain a quadratic 
expression for /; integration of (1) then yields: 
a 
nk ee ieee A 
I have already pointed out before that equation (2) is sufficiently 
in agreement with the measurements of the equilibrium for many 
gas reactions”). As was said above, this expression holds perfectly 
accurately only when the algebraic sum of the specific heats of 
the reacting substances is zero at all temperatures. This is certainly 
not the case in general; the influence of the specific heats is, however, 
so small for almost all equilibria that the mistake made by neglecting 
it, is much smaller than the inevitable errors of observation. Hence 
1) If in K the concentrations of the second member are in the numerator, then 
E is the loss of energy at the reaction. 
2) These Proc. XV, p. 1116. 
