( 592 ) 
p v p (calcul.) wv (caleul.) 
175 0,002263 177,6 0,002269 
150 2333 151,0 2336 
125 2432 124,6 2430 
100 2600 98,7 2587 
76,30 3090 76,25 3086 
74,50 3283 74,57 3295 
73,75 3573 73,76 3576 
73,26 547 73,34 558 
72,37 630 72,46 637 
71,42 682 71,62 693 
69,50 ‘Ee 69,76 782 
67,57 850 67,83 861 
64,63 968 64,72 972 
59,71 0,01156 59,74 0,01157 
54,77 1356 54,83 1359 
49,81 1584 49,88 1588 
44,84 1856 44,85 1856 
39,86 2187 39,86 2186 
3. The formulae I have found for the critical isothermals are purely 
empirical. I was led to using formulae of the form given above by the 
remark that it was possible to find such a value of 6 that the 
critical isothermal, drawn in a diagram with p as axis of ordinates and 
as axis of abscissae showed a centre of symmetry in the critical 
KE 
point. In the annexed figure, representing the critical isothermals of 
isopentane, this symmetry is very conspicuous. 
The marks represent the observations, the line drawn represents 
my formula. 
It may be seen that only in a very forced way a division of the 
pressure into a thermodynamical and a cohesion pressure can be 
deduced from my formula, which division is the basis of VAN DER WAALS’ 
theory. If therefore my formulae have a theoretical meaning, this seems 
to be based on a principle somewhat different from VAN DER WAALS’ 
equation of state; I did however not succeed in deducing such a 
principle. 
