( 106 ) 
at r— 0.65; which has never yet occurred in former experiments. 
I have not succeeded in finding a simple meaning of this; the con- 
dition for the occurrence of such a point of inflection leads to an 
intricate relation, in which also the unknown relation between za 
and 2, occurs. 
That the point of inflection really exists and that it is not due 
to an inaccurate method follows, in my opinion from the following 
considerations : 
Ist the deviation from the observed curve, required to get a curve 
_ without a point of inflection is much greater than the investigation 
of the method would give us cause to expect. 
2ud When we calculate the composition of the gas by means of 
the approximated formula 
1 A dp he d—Ly 
p de Ta) rolla) 
given by Prof. VAN DER WAALS in his „Théorie moléculaire” !) 
we find the points indicated by © in fig. 3, which points agree 
very well with the observed curve, at least at the ends; that the 
deviation is greater in the middle was to be expected, according 
to the approximations used in the deduction. 
A curve drawn through these points, shows also a point of inflection. 
If we draw a tangent at a point of the curve p= f(a»), we 
arrive by means of the former formula at the values which are 
given as calculated in Table III. 
EAB E.E TM 
he | 7 dp. Ld—2y rd 
| | dze calc. observed. calc. observed. 
0.05 85.5 | 301 | 0.167 «| «065 0.217 0.215 
0.1 99.5 | 264 0.297 0.253 0.327 0.353 
0.2 | 120.6 | 179 0.237 0.305 0.437 0.505 
0.3 | 1344 | 137 | 0.215 | 0.280 | 0.515 | 0.580 
Onder Me ff i V2 | 0.180 | 0.232 | 0.580 0.632 
Obe 15820 | 94 0.150 | 0.170 0.650 0.670 
0.6 166.7 | 74.5 0.107 0.15 0.707 0.75 
0.7 | 173.7 63 0.077 | 0.08 0.777 0.78 
0.8 179.2 50.5 0.045 0.042 | 0.845 0.842 
0.9 183.4] 3] 0.016 | 0.02 0.916 0.92 
') Arch. Néerl. 24. p. 44. 
