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it was supposed that this substance would always behave in a unary 
way. Experiment has fully confirmed this conjecture. Whether mer- 
cury was suddenly cooled by water in vacuo from + 300’, and 
then by solid carbonic acid and alcohol, or whether it was rapidly 
heated from 80, the point of solidification, resp. melting-point always 
remained the same, and the substance perfectly behaved as a unary 
one, from which we may therefore draw the conclusion that when 
the substance is complex the internal transformations must proceed 
with extraordinarily great rapidity, or what is more probable that 
mercury really consists of one kind of molecules. 
The third substance examined by us, for which in view of its 
transition points, the same was expected as for the phosphorus, 
was tin. 
Though the investigation made bears as yet still a preliminary 
character, we may yet communicate that tin of particularly great 
purity ean solidify entirely as a unary substance, but that it 
betrays its complex character when the experiment is made very 
rapidly, just as phosphorus does. In a following communication we 
hope briefly to communicate the result of the final investigation. 
Amsterdam, December 23" 1910. 
Anorg. Chem. Lab. of the University. 
Chemistry. “On the determination of threephase pressures in the 
system hydrogen sulphide + water.” By Dr. F. E. C. Scuerrer. 
(Communicated by Prof. A. F. HOrLRMAN). 
|. In the investigation of the systems in which hydrogen sulphide 
is one of the components, the difficulty presents itself that a chemical 
action can affect the mercury that shuts off the mixture, when it is 
not sufficiently purified from admixtures. This action will chiefly be 
due to the presence of slight quantities of air. By excluding the 
presence of air (and water), as completely as was possible in the 
methods used, | succeeded before in determining the situation of the 
three-phase curves in the system hydrogen sulphide + ammoniac. 
The methods used in the investigation, had to be adapted to 
high pressures, as it was my principal aim to determine the points 
of intersection of the critical line and the three-phase curves, the 
critical end-points. In this T have at the same time found an oppor- 
tunity to determine the shape of the spacial figure of the mentioned 
system at lower temperature; the observations at these low tempe- 
