649 
the reacting substances themselves would be subjected to new 
decompositions, and the realization of the phenomenon would be 
excluded. 
8. Conclusions. 
At the present state of our knowledge of the gas equilibria 
every gas reaction may be represented by the two-constant formula 
ee a : ; 
log K = Ae 6. There are no reasons to add more terms with 7’ 
to this expression in the second member, as the experimental errors 
are always greater than the change that can be effected by these 
7-terms in the formula. If the addition of these terms is necessary, 
and if they, therefore, bring about an appreciable modification in 
the curve, we have to do either with a wrong interpretation or 
with errors of observation. 
In contradiction with what is recorded in the literature, the 
oe dlog K : \ 
transition case of en — 0 has not been found with any certainty 
for a single reaction, and it will not be easy to realize either in 
my opinion. This case might be found for a reaction that has a 
very small heat of conversion over a very great range of temperature ; 
an example of this is, however, not known. 
Physics. — “Comparison of the Utrecht Pressure Balance of the 
VAN ’r Horr Laboratory with those of the VAN DER WAALS 
Fund at Amsterdam.” By Mrs. E. I. Hoogensoom—Smip. 
Van per Waars fund researches N°. 9. (Communicated by 
Prof. P. ZEEMAN). 
(Communicated in the meeting of Sept. 30 1916). 
Introduction. In the former half of 1915 a comparison was made 
of the small Amsterdam pressure balance with the open standard 
manometer at Leiden from 20 to 100 atmospheres’). The result of 
this was that the effective area appeared to be not equal to the 
real area; a constant value was not even found, but a value 
dependent on the pressure. 
To be able to make accurate determinations of the pressure in 
spite of this it is required to study the theory of the instrument. 
1) See GC, A. GROMMELIN and Miss E. I. Smip, Comparison of the pressure balance 
of S. and B. etc. These Proceedings XVIII, p. 472. 
