288 
vee ee (1 ova oe 
Te cs = v RTv 
da 
Ee vb A) Sl EET a 
—b 
; v(t ya. Ava) 
Vv 
Gebs (Q—«) RTv — 4a (le) (A Va 
because 1 + '/, 2 (1—x): (1+) is = 1—'/, «. If we put for brevity: 
we have finally : 
dar: il x (le) (RTv—4a A) 
dv), v—b (2—a) RTv—4x (1—a) A? 
(1) 
When A =O, or may be neglected, as in all cases of dissociation 
which do not eventuate in isolated atoms, then (5) = en nj 
dv}, v—b I--« 
the already known expression, which is always positive, and which 
becomes =O for z=0O and «= 1. 
But if A is large, as with Hg, — 2 Hg, then in consequence 
of RTv—4eh=RT0—4°—* ya. AVa=o| RIAS | 
5 v Va 
the quantity 4/7, can become negative at lower temperatures or 
comparatively small values of v. In mercury, where Va = */, Va, + 
+a.A Vais = (10+ 302r).10-, Aa: Va willapproach 30:10 = 3 
with small values of «, so that then the transition from positive to 
av—b 
negative is reached, when R7’= If v = ve, then with 
Ve = 1,86,, and a about =*/, a,b =*/, be, this temperature will 
0,75 a-1,8—0,75 35a, 
be given by RT? =12 x —— And as in mer- 
AB ibaa LER 
cury. Alias ~ = “>< 2x (about 1,25) = a, (compare the first part 
in these Proc), 7’ becomes about = "*/,, Zi, 
T~ 4 T, (at v =v), 
so that with a volume =v, the quantity ?/g, becomes positive 
again only above about 6700° abs. 
