269 
and 6 will be smaller than those which have been determined at the 
critical temperatures of the mercury-halogenides (which temperatures 
lie in the neighbourhood of 1000° abs.) is, indeed, to be expected. 
For it is known that 6 and a decrease with increasing temperature. 
But there is still something else required. If such a high critical 
temperature and pressure is to be reached, the double molecules 
must be dissociated at 7. to a slight amount. As at this dissociation 
the value of a is greatly increased (10°/a, becomes 40 per Gram- 
atom of the isolated atoms as against 10 in the double molecules), 
the calculation (which we shall give in the second part of this paper) 
shows that, even in case of a slight degree of this dissociation, in 
the formula a pretty large factor will appear for 7’. on account of 
the large value of da/dx, which will increase the value of 7. by 
abont 30°/,, and can consequently raise the value of p. to more 
than four times the amount of the original value (Cf. also § 8). 
Hence it is not because in consequence of this slight degree of 
dissociation «w the value of a, itself is appreciably increased, and 
consequently 7, and pe (which are both proportional to a,) are 
likewise increased in the same degree (for this the increase of a, at 
so slight a degree of dissociation is much too small) — but because 
in consequence of this dissociation, tz connection with the very high 
value of da/dx, the formula which expresses 7, in a, obtains a 
factor that is a function of « and da/de, and through which 7, is 
increased by the said amount of e.g. 30°/,, even though the disso- 
ciation of the double molecules is only slight. And im consequence 
of this factor in 7, the formula for 
Tedd g dc 
Vick be be 
Pe == 
will undergo such a modification that p‚ is not increased by 30 °/,, 
but by more than 300 °/. | 
Thus the extraordinary circumstances connected with the critical 
temperature and pressure of mercury have induced me to extend 
my former theory concerning the critical quantities on association *) 
for the special very important case that a is considerably increased 
1) Arch. Teyler (2) 11, 3e Partie (1908), p. 1—96; These Proc. 17 (1914), p. 598 
We remind the reader that the mere fact of the dissociation at Te (hence Ab and 
A@=0) causes the values of 7 and pc to increase considerably. Thus we found 
for x=!1/, already an increase of 10,6%, for Tc; for x="/g of 11,5 °/), and for c=?/, 
of 9,9°/, (for «=O and « =1 the factor is of course = 1), Le. for ideal snbstances. 
For “ordinary’ substances and for the cases that in the association e.g. Ab is 
not = 0, these amounts are considerably increased. And as regards pc, these 
or 
