971 
temperature (with a view to determining which the experiments of 
KAMERLINGH OnnES and PERRIER were undertaken (see Comm. N°. 116 
§ 1) would be given by a series of similar lines, differing for the 
different densities. 
We must not forget that it is by no means established that in 
the case of oxygen the divergence from Curiz’s law is determined 
by a A’ which changes with the density, and that it obviously may 
be due to an association of molecules into complexes with a dimi- 
nution of the number of magnetons. 
However this may be, our attention is again drawn to the im- 
portant question whether the divergences from Corie’s law depend 
upon a peculiarity of the atom within the single molecule or from 
the approach of the molecules up to a very small distance. 
In § 3 of Comm. N°. 122a by KAMERLINGH Onnes and PERRIER, 
it is said that preliminary experiments with mixtures of liquid oxygen 
and nitrogen, which will soon be replaced by better final ones and 
which were based on the above mentioned association hypothesis, 
seemed to indicate that bringing the molecules to a greater distance 
by dilution in the liquid state has no influence of importance upon the 
divergences from Curtr’s law. Here the question is raised in 
this form: whether A’ is a quantity which as peculiar to the atom 
in the single molecule can also be found in the gaseous state or 
whether it can only. be developed by bringing the molecules into 
immediate vicinity of each other. Further experiments *) with oxygen, 
already planned, must decide this. 
(To be continued). 
Physics. — “The law of corresponding states for different substances.” 
By Prof. J. D. van DER Waals. 
(Communicated in the meeting of December 28, 1912). 
In the following pages I shall give an account of the result of 
the researches which I have made of late about the properties of 
the equations of state for different substances. And I shall commu- 
nicate in them the simple conclusion at which [ have arrived for 
all the substances for which a chemical combination does not take 
place, and the molecules continue to move separately, either really 
isolated, or perhaps joined to groups, if this aggregation (quasi 
association) behaves in the same way. 
1) As this communication is going to press, these experiments have advanced 
so far, that we may accept with great probability as the result of them, that 
gaseous oxygen of 90 mes the normal density obeys Curte’s law down to — 130° C, 
