( 288 ) 
equilibrium surface which was at first continuous will become dis- 
continuous and break up into an equilibrium surface for the vapour 
state and another for the liquid state. 
The lines of intersection of these two surfaces with the surface of 
two sheets are the lines PJ and PA HE in fig. 1. To these must, 
of course, also be added lines of intersection with the other gas- 
and liquid surfaces, which have been mentioned in the previous 
communication. f 
In this manner, it appears that special equilibria, which occur 
when transformation between the two components is possible, may 
be always considered to originate from the intersection of the general 
space figure for the equilibria of phases with the surface of equilibrium 
for the molecular equilibria in each phase. 
Chemistry. — “On the action of sulphur on toluene and xylene.” 
By L. ARONSTEIN and A. S. van Nierop. (Communicated by 
Prof. J. M. vAN BEMMELEN). 
(Communicated in the meeting of September 27, 1902.) 
The researches on the molecular weight of sulphur according to 
the boiling point method of L. ARONsTEIN and S. H. Mernuizen *) 
showed that this molecular weight was found to agree with the 
formula S, and this in liquids the boiling point of which varied 
from 45° to 214°. But when toluene and xylene were used as solvents 
for sulphur the determination of the molecular weight had given 
values which corresponded with those calculated from formulae ranging 
between S, and S,. It was then suspected that this difference might 
be due to chemical causes. In the following lines we will communicate 
the results of our efforts to trace those causes. 
Action of sulphur on toluene. It had already been noticed that on 
boiling a solution of sulphur in xylene hydrogen sulphide was given 
off which was shown by means of lead acetate. A similar evolution 
of hydrogen sulphide was not noticed on boiling sulphur with toluene. 
As the chemical action of sulphur on toluene at the usually observed 
boiling point could probably not amount to much, a preliminary 
experiment was made by heating a solution of sulphur in toluene in 
sealed tubes at 250°—300° so as to accelerate the action until on 
1) Proc. Kon. Akad. Wetensch. 1898. First section VI, 3. 
