370 PROCEEDINGS OF SECTION A. 
: i 25 : 
according to the relation / = $ (2, me - R)o T the third from 
Vg 
the latent heat 4 according to the relation /4= fe adv 
a 
which, with appropriate reduction and approximation, gives 
M1/v, =66°5 AZX—-101 7, in terms of the megadyne, gramme 
and centimetre, where J/ is the molecular weight and 7; the 
boiling point (counted of course from absolute zero) 4 being 
measured in calories; the fourth from the equations given for 
T.and p~, whence /= 409 &’ 7?/ 400 4, The fifth method depends 
on results already established (PAz/. Mag.. July, 1887, and 
April, 1889), that the internal virial is 3 7 4 p Jog Z/a, so that, 
for compound liquids, 7= 4 7 A log L/a where Z/a isa ratio 
which is constant and the same for all compounds; and that the 
surface tension x Is given by x = wp’ Ae / (2 + vy’ 2) where e is 
like a a quantity nearly equal to the mean distance apart of the 
molecules, from these we get / = ¢c x v3 / 173 wherec is a constant 
whose value can be found. To get comparable values for ditferent 
bodies we must measure y and v always at the same fraction of 
the critical temperature. These methods enable us to calculate 
values of 7 for a large number of bodies; the following are three 
illustrative samples of the agreement of the different methods :— 
Method Second Third Fourth Fifth 
GS; 26°5 25°7 27°2 26°9 ) Values of 47° in terms 
CHC, 33°0 38°2 36°71 36°8 ~ of megamegadyne, 
God. MAD 43°] 42-7 43°8 \ gramme and cm. ~ 
Agreement such as this in a large number of cases constitutes 
the veritication of the theory so far unfolded. In s-eking for the 
law that connects the virial constant 7 of a compound with its 
chemical composition, it proved advantageous to multiply 7 by 
M*, and it was then found that J7°7 = 6S + 668° where S is 
called the dynic equivalent of the compound and is defined as the 
number of C7, groups in the normal paraftin which exerts the 
same molecular force as the compound; .S is the sum of the dynic 
equivalents of the radicals in the compound. The following are 
the values of the dynic equivalents for several radicals, along 
with their molecular refractions in terms of that for CZ, as unity 
CE we H CO OO Nise 
Dynic equivalent 1 7a) (P25 dO Gen eel 
Molecular refraction 1 54 P3vil-4) 35) chhpeeeliaee 
iO UCM Sigma SC 
2 2:85 “ 
2 
Dynic equivalent 1 
S-Ouinls 
9D. 
ad 
Molecular refraction 2° 
ee 
