( 590 ) 
6 = C(1 — my 
is intimately connected with the form of the isothermals near the 
critical point, by means of which also the formula for the densities 
of liquid and vapour (with the aid of the MAXxWELL-CLAUSIUS 
theorem) must be determined. 
It now appears that in the place of the exponent !/p in the 
difference of liquid and vapour density a less simple fraction must 
be substituted. Hence as according to VAN DER WAALS’ simple 
supposition the isothermal is a curve of the third degree, I have 
investigated whether the critical isothermal could not be expressed 
in an analogous way by means of a fractional exponent. The result 
I arrived at, was that the observations of S. Young on the form 
of the critical isothermal of isopentane are well expressed by the 
formulae: 
ve — b 
p = pe— pe(1— Je for”. =o > Us 
vu—b 
and 
Ve — 
b n 
p= pet pe (5 ~1), for oves 
in which p,.=32,92 atm., 1.=4,266 c.c. (specific volume), 2=0,518 cc, 
and n= 4,259. The following table shows that these formulae are in 
good harmony with the observations: 
EAB ae AT, 
v p (observ.) p (calcul.) 
19,41 19,90 20,06 
16,91 21,95 21,99 
14,40 24,13 24,27 
11,91 26,84 26,86 
9,440 29,69 29,65 
4,505 32,92 32,92 
3,160 33,70 33,73 
3,050 34,59 84,35 
2,939 35,49 35,56 
2,829 37,49 37,32 
2,718 40,51 40,37 
2,608 45,49 45,27 
2,497 53,51 53,08 
2,431 60,59 60,42 
2,394 65,24 65,60 
2361... “s/s 90s 70,87 
