1114 
Snu = SnL—-T2n + SnkT = 0. 
If in this we introduce the entropy free from concentration, this 
equation may be written as follows : 
SnE--TEnH ar + RT Znlne + ZnRT 0. 
If we now express Ynlnc by InK,, in which therefore A, repre- 
septs the so-called equilibrium constant (in concentrations), then : 
RTnK, = Sn Lene ant 2. 
Differentiating’ this equation with respect to 7’ after division by 
RT, we easily find the well-known equation of VAN ’r Horr : 
dinK nk 
die APS 
If we now imagine Yn to be a very weak temperature function, 
which may be put practically constant over a limited temperature- 
range, equation 11 vields on integration : 
A ge 12 
tene ee oO ar ig EEA EEN 
ay 
On comparison of equation 12 with 10, it appears that on this 
supposition also the entropy free from concentration may be put 
independent of the temperature. This conclusion is moreover also 
clear when we consider that both the change of nf and that of 
YnH.—, with the temperature is exclusively determined by the value 
of Ene. If therefore really the value of 2nc, in a certain range 
of temperature is negligibly small, the observations in this range 
may be represented by equation 12, in which two constants occur: 
nk Er 
= the change of energy divided by the gas constant, and C, 
> 
which contains the change of entropy and the gas constant. 
And inversely when it appears that the constant of equilibrium 
as function of the temperature may be represented in an equation 
with two constants like 12, a measure will be found in the value 
of these constants for the change of energy and entropy during the 
reaction. If therefore in one graphical representation R/nk, is repre- 
: 1 : 
sented as function of 7 and in another 7%nX, as function of 7, and 
if the observations in the first graphical representation give a straight 
line, this is also the case in the second. The inclination of the line 
in the first representation yields the energy value, that in the 
second the value of C in equation 12, so the entropy value, at 
least if the fact is taken into account that according to equation 
10 C also contains the gas constant and Yn. If we now assume 
that the observations have been made with great accuracy, in gene- 
