J116 
specific heats many gas equilibria can be accounted for by means 
of two constants, not only over a small temperature range, «but 
sometimes even over a very large one, at least if the observations 
are not particularly accurate. The dissociation constant of the nitrogen 
tetroxide can e. g. be expressed by an equation or the form 12 
(ScHREBER’S equation), and also the dissociation equilibrium of car- 
bonic acid, the errors of observation being comparatively large here, 
can be accounted for by equation 12 over a temperature range of 
hundreds of degrees. 
These considerations teach us accordingly that observations of 
equilibrium constants with comparatively large energy and entropy 
values enable us to calculate them pretty accurately, but that gene- 
rally no conclusion can be drawn about the influence of the tempe- 
rature on energy and entropy, the errors of observation being 
generally too great for this. Thus the above formula of SCHREBER 
enables us to find a mean value for the heat of dissociation of the 
nitrogen. tetroxide and for the “kritische Raum” of the NO,-mole- 
cule’), but the influence of the temperature on either is not to be 
derived from the measurements of the equilibrium. 
3. If we now return to the reaction velocities, we can also apply 
the considerations mentioned in the preceding paragraph here mutatis 
mutandis. Equation 6, which indicates the dependence of the velocity 
constant with the temperature, presents great analogy with VAN ’T 
Horr’s equation of equilibrium (equation 11). If er—e is a very 
weak temperature function, equation 6 yields on integration: 
E/— El 
RT 
in which as appears from equation + B does not contain any 
constants depending on the nature of the substances, except the 
difference of entropy. So in this case too the difference of entropy 
between initial and transitional state is practically independent of 
the temperature. Here too we can therefore graphically represent 
in k = EB AA Sr Sen 
ans, 
1 
Rink as function of = and determine the differences of energy 
between initial and transitional state. It seems therefore natural to 
examine whether the material of facts referring to the reaction velo- 
cities can be represented by equations of the form 13, where ¢;—., 
and B are considered as constants. 
In his Etudes de dynamique chimique van “rt Horr for the first 
time gave an expression for the dependence of the velocity con- 
1) BOLTZMANN. Gastheorie II. § 66. 
