134 Transactions oj the Boyal Society of South Africa. 
Table VII. 
Inversion Curve: Modified Equation. 
Too- 
Too- 
^. 
Too- 
0-496 
1-066 ! 
0-725 
1-099 
0-892 
1-088 
0-549 
1-075 i 
0-762 
1-100 
1-920 
1-073 
0-598 
1-083 
0-797 
1-099 
0-948 
1-060 
0-643 
1-090 1 
0-830 
1-096 
0-975 
1-043 
0-685 
1-095 
0-861 
1-090 
1-000 
1-000 
To obtain the experimental inversion curve, isopentane was again taken 
as a typical normal substance and equation (26) was applied to it in the 
unreduced form — 
y..-i- . . . • (26') 
T 
The second term of the denominator has already been evaluated by 
DiETERici " for isopentane, and his values have been used. The other 
term, which occurs only as a small correction, was evaluated by means of 
the Kamerlingh Onnes mean reduced equation.! According to that 
equation the product, ttw, is expressed as a finite series of inverse powers 
of the reduced volume— 
.a(i + B^ + c- 
(30) 
where B, C, D, etc., are expressed as polynomial functions of the 
temperature. The complete equation has five such " virial-coefficients," 
but for the present purpose the three given above were sufficient. 
EiT 
h is the critical constant 
We now find, to the degree of approximation required — 
/•Dc>N , ^3 d: 
and from this we easily obtain the correctional term 
(31) 
) L. 
» C. DiETERici: Ann. d. Phys. 12, 602 (1903). 
t Kamerlingh Onnes and Keesom : ojj. dt. p. 729. 
