( 305 ) 
“When the heat developed by the combination of 7” simple mole- 
cules to a complex one is so great, that it far exeeeds the quantity 
(n—1)7 Ti, — as is the case for acetic acid — then the saturated 
vapour will at higher temperature be associated in a lower degree. 
If on the other hand that quantity of heat is much smaller than 
(n—1) 7 7. then the reverse will take place.” 
When we proceed to saturated vapours of greater density and when 
we approach the critical temperature, then this difference in the 
course will no longer exist. 
If we consider in the equation: 
ET B de, r 1 n da A 
n— 1) ——- — + — ——= —.. 
v—baT © ap l—w/) dT i! 
ek) 
the value of — Sa PT for the saturated vapour at all temperatures 
vd A 
between O and 7, we see that this quantity has a minimum value 
for a certain value of 7. For very low temperatures it may be 
7 
ie 
equated to 7 an and for the absolute zero it is therefore infinite. 
But also for 77=T.,. it will be infinite, for by is infinite in the 
critical point. The value of 7’ for which this minimum value occurs, 
would for normal substances be the same fraction of 7. For sub- 
stances with molecular transformation we find a different value for 
this fraction. It may be calculated for many substances from the 
experiments of SIDNEY Youne at least approximately. 
Ed A 
RT iT 
Above the temperature for which — for acetic acid 
also see is again positive. For substances which behave as acetic 
di 
acid therefore a minimum value of wv occurs. The fig. (1) of Bakuuts 
ROOZEBOOM presents in fact such a minimum for paraldehyde, and 
from this would follow, that this transformation is of the same type 
as that of acetic acid. Yet it seems possible to me that an accurate 
direct investigation would prove this minimum not to exist. If it 
really exists, then it will probably occur at a much higher value 
of 7% 
But even if this transformation would also prove to be of the 
same type as that of acetic acid, vet it seems not superfluous to 
me to point out, that also the other type may possibly oceur. 
The abnormality of substances as the alcohols, water, etc. is ascribed 
to a possible molecular transformation, and yet the saturated vapour 
