272 
The “calculated” values of D, have been determined from v, = 
RT 
= RT: p tor 1 Gr-atom, henee wr THS 22415 em’ for 1 Gr., 
when p is given in atm. and R=1: 2738.1. Hence we have: 
p 200,64 Ps 200,64 
D', == X a = 
ie 
Le == K ——_ = — 2,444, 
on ae tae 2D 82,08. 2 X 
It appears from the value at 1000° that at this temperature the 
vapour is still mon-atomic, and the deviation from the law of Borre 
is still very slight. The deviation increases more and more, and 
close to the critical temperature the vapour will be almost bi-molecular 
like the liquid. As D(calc): D(found) is about 2,6 at 7, the 
deviation from the law of MariortE would be there about 2,6 : 2=—=1,3. 
In an ideal substance s = 2,67; in an ordinary substance s = 3,8 
to 4+. We see therefore, that the normal value of s is very consider- 
ably decreased in consequence of the greatly increased value of p‚ 
through the small dissociation of the double molecules at 7,. Also 
the values of v, and 7, are modified by this, but not in the same 
degree as p‚. The result is accordiugly that, whereas p, is more than 
four times greater than the normal value in case of non-dissociation 
of the double molecules, s will be about 3 times smaller than the 
normal value 3,8 to 4, i.e. 1,3. 
We shall discuss this more at length in ó 8. 
5. The values of D, and D, + D,. 
We now proceed to the values of D,, i.e. those of the liquid 
densities. At the same temperatures (to which three more tempe- 
ratures below 100° C. have been added) the following values are 
found. The “found” values of D, + D, (see table following page) 
have been obtained by addition of the above found values of D, to 
those of D,. 
The “found” liquid densities D, above 350° C. are graphically 
interpolated from the following values determined by Miss Brenner. 
500° 600° 800° 900° 1000° 1100° 1130° 1200° 1270° 1320°C. 
DD, = 12,5) 12,15: 11,6511,15;, 10,55 1050. 79:40 TPS eon aoe 7,8 
As regards the “calculated” values of D, + D,, they were calcu- 
lated from O° to 350° from 
D, + D, = 13,5956 —0,0024507 t + 0,0,2089#2, . . . (a) 
in which the coefficients of ¢ and t° were calculated from the 
observations at 150° and 300° C. The calculated and the found 
