17 
value for all. This is, however, not the case; yet the critical pres- 
sures do not diverge so much that log pp moves within a wide 
margin: in most cases the values of pj lie between 40 and 60 atm., 
hence log px between 1,60 and 1,78. This would cause 7% :’7’, (with 
f, on an average 2,9) to lie between 1,55 and 1,61. Only in extreme 
cases will p, ascend to 100 atm. or descend to 20 atm. Then /og px 
would become resp. = 2 and 1,30, hence 7%: 7, resp. == 1,69 and 
1,45, so that then too the values of this last ratio comparatively do 
not lie far apart. Practically the said ratio can only vary between 
1,45 and 1,69 — though fog py, can lie between 1,3 and 2; in 
most cases it will vary even between the still narrower limits 1,55 
and 1,61. As mean value 1,60 can be given, so that — and strictly 
speaking this holds only for normal substances, or such associated 
substances as no longer change in the neighbourhood of 7; as far 
as their molecular state*is concerned — one can conclude in many 
eases to the critical temperature from the temperature of the bovling 
point. (See following table.) 
The mean value of the ratio PT: 7s for the 49 anorganic sub- 
stances, for which we could calculate this ratio, amounts to 
1+ (327 : dj) = 1,638 = 1,64. 
‘That for the osganic substances is somewhat lower; we found 
for the 58 substances, for which 7}: 7; was calculated: 1 + 
+ (3244 : 58) — 1,559 = 1,56. 
The mean of all the 107 substances amounts to 1 + 6371 : 107) = 
= poe a= 1,60: 
The ratio 7: 7, does not exhibit any perceptible regularity ; the 
cause of the great difference, which often exists for closely allied 
substances with respect to this ratio, has not yet been explained. 
We need only think of 1,40 for CO,, 3,58 for CS, 
With regard to the application of the rule 7): : 7, — 1,60 for 
substances as As, Sb, Al, Hg, ete., we should bear in mind that these 
and suchlike substances can be greatly associated, and that the 
state of association between the boiling point and the critical poiut 
can still vary pretty considerably. Accordingly we shall often find 
values deviating more or less considerably from the mean value. 
Thus the ratio 7: 7, is even 2,00 for mercury. 
IV. The critical values of Antimonium. 
In the formula (Aa) the value of m at the ordinary temperature, 
referring to the critical temperatures of the compounds SbCl,, SbBr,, 
SbI,, will be about */, or '/,, so that hj, 51,67 », or 1,75 7. 
2 
Proceedings Royal Acad. Amsterdam, Vol. XIX. 
