299 
(see I). The value 125,5 for 10° bj. tor chlorine has been calculated 
from PriLavon’s critical data, 113 following from those of Dewar. 
When pj is unknown the values of a; for 1 atom can be cal- 
culated from the formula R7',=°/,, 4. me. (an: Or), in which nz 
represents the number of atoms in the molecule at Te Kor if 19 
distinguish between a, and bp (which now refer to the whole mole- 
cule), we denote the values referring to 1 atom by az, and bp, evi- 
dently ap = nt. ap and br =n. Or, If in the formula mentioned 
the factor 4 is in the neighbourhood of */,, for substances with 
comparatively high critical temperature (when namely y= 1), then, 
as we already saw before, this formula reduces to 7%, = 78,03 nj. 
(ar: bm). But as soon as y differs considerably from unity, it is 
8y—1 
Thus we calculate for ay, the value 5,47. 10, hence Vai, = 
= 9 34). 10-2, for B, with m= 2,7, = 152 abs., bp == bbr. 
This value is considerably lower than that found for compounds, 
namely about 2,9.10 ?. 
For Cl, we calculate directly the value Waz, — 5,15 .10-? from 
Tr and px, when we use the critical data of PrrLaArToN, but 5,43 . 10 
with those of Dewar. In compounds on an average 5,4 . 10—? was found. 
For Br, and I we find in the same way for aj, resp. the values 
60,4.10-4 and 111,2.10-4, when namely nj, = 2 is taken. This 
would give Waz, = 7.77 .10~%, resp. 10,55 .10-2.-But-these values 
are much greater than the normal values 7, resp. 9 found for com- 
pounds, so that from this we can draw the conclusion that in con- 
nection with what we shall find later concerning the so much greater 
attraction for the isolated atoms, which for the present we may put 
at about 30.10 2 — the two elements Br, and I, at the critical 
temperature have already been dissociated for a small part into 
atoms Br, and I, '), where therefore the full attraction of these atoms 
begins to make itself felt. But on account of this 77 will no longer 
be —2, hence we should reconsider our calculation of War, 
If we namely assume that the above formula for A77, continues 
to hold by approximation, when instead of with a simple substance 
we have to do with a mixture of two substances (e.g. I, and 1), *) 
9 
better to use the general formula, in which 4= — (4) 
1) As far as I, is concerned, this dissociation at 512° C. cannot astonish us, 
as it is known that the dissociation I, > 21, is already complete at about 1500° C. 
2) In reality (cf. Arch. Teyler 1808 and These Proc. of May 30. 1914, p. 601) Tr will 
not depend linearly on the degree of association nj.,but it can deviate from it 61/5 0/, 
as a maximum (for «= 2/g). If, however, w is slight, e.g. 0,1, the deviation is so 
insignificant that it may be neglected. 
