638 
it appears in the application of equation 2 that almost all the 
chemical equilibria may be just as well represented by this expression 
as by the more complicated expressions 3,4 ete., which are pretty 
well universally used in the literature. This fact justifies in my 
opinion the preference of equation 2 to the others on account of its 
simplicity. 
In perfect harmony with this appears also the fact that the 
observations of chemical equilibria have never been executed accurately 
enough to make calculations of the specific heats of the reacting 
substances possible. 
If now the specific heats were well known through direct measure- 
ment, it would be rational to take them into account when 
drawing up the equation of equilibrium. For this purpose we want, 
however, the specific heats of a// reacting substances, as only the 
algebraic sum plays a part in the equation of equilibrium. Generally, 
however, the specifie heats of only a few substances are sufficiently 
known, and that at temperatures which deviate from those at which 
the measurements of the equilibrium have been carried out. Besides, 
for dissociating substances a direct measurement of the specifie heat 
is impossible exactly in consequence of this decomposition. Generally 
no sufficient data are therefore available for the specific heats to 
justify the drawing up of an equation of equilibrium which contains 
more terms than equation 2. 
That the influence of the specific heats is so small that equation 
2 can just as well be used as 3, 4 ete., may seem astonishing at 
first sight. I explained the reason of this already before’); in the 
following paragraph I shall elucidate this question in a somewhat 
different and perhaps more intelligible way. 
But it is not only for the sake of ifs simplicity that [ prefer 
equation 2 to all the others. In the literature many equilibria have 
been described which are indicated by expressions which are more 
complicated than equation 2. Now there are two cases possible. 
Either the observations can just as well be represented by the 
formula with two constant quantities, or they cannot. In the latter 
ease we have to do with very great errors of observation. The 
ereat advantage of 2 is that it draws our attention to these errors. 
If equation 2 cannot be used, the observations must be repeated. 
I will demonstrate in the following pages by a number of 
examples that equation 2 is just as suitable as the more complicated 
equations and at the same time I shall show of some other equilibria 
1) These Proc. XV, p. 1114 et seq. 
