1222 
= 27:4, (f’—1): s? = 27: 642. Compare moreover the table on 
p. 819 of the first of the cited articles, and that on p. 1052 of 
the third paper. 
For the quantities 7% and pz we find then perfectly accurately: 
8 az U : 
RT, >= — A — B Pii 
27 br 27 bp 
at least for normal substances which are not assoaciated at 7. In 
. 27 2 NE 
this (see loc. cit.) the factor À is given by 4 = —— {| —— | For sub- 
Pag, y+1 
stances with a particularly beberer critical temperature y has the 
limiting value 4 and 2 becomes =e, — 01964. Rorstordinarvan 
lo herd 
substances y—=0,9 and 4 becomes = 0,977 ; for argon, wher 
4 becomes = 0,992; for H, with y=0,6, 4 =0,999; while for He, 
where y = 0,55, 4 will be = 0,999. For ideal substances, where 4 
is constant, y approaches 0,5 and 4 approaches 1. 
We see from this that the correction factor 2 deviates about 
2,3°/, from unity for ordinary substances, so that in the second of 
the relations: 
1 RT; 7 (RT%)' 
ke == 9 == 
Dik 642 pr 
the value of a, must then be augmented by this amount; and by a 
smaller amount when the critical temperature, as for argon, O,, N,, 
H,, ete, is particularly low. We have always taken this factor 
into account. 
When the substances at 7% are still associated, the above simple 
formulae must be replaced by much more intricate ones. ') For the 
few abnormal substances, however, which occur in the following 
tables, we have calculated the values of a, and 5, on the supposi- 
tion that these substances are normal at 7} and then added that 
the accurate values are smaller. (Always in reference to a single ~ 
molecular quantity.) 
For R we have put the value 0,0036618 — 1 : 273,09, so that 
the values a, and bj are expressed in the ordinary ‘‘normal” unities, 
Le. 6 in the normal volume v, = 22412 cm° (the volume of 1 gr. 
mol. of substance at 1 atm. and O° C. in the Avocapro state), and 
a in atm., when 1 gr. mol. has the volume »v,. 
Want of room obliges me to omit the extensive table of 74 sub- 
stances, in which 7%, pk, by, dx, Waz, and 4 have been given; there- 
fore the values of 7; and p, have been added in the following 
sae tables for 6,. These values have been taken from the best 
NG Arch. Teyter 1908. and also These Proc. of Nov. 7, 1914, p. 598. 
