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For the complexes of fwo phases, the relative proportions may also 
be read off in the figure; for those of (ree or four phases it would 
be necessary to also know the relation of the volumes. 
The figure also makes it possible to ascertain what changes a 
mixture will undergo, when the temperature, pressure!) or concentration 
are changed. 
Chemistry. — “Lquiibria of phases in the system acetaldehyde + 
paraldehyde with and without molecular transformation”. By 
Prof. H. W. Baxkauis RoozrBoom. 
(Communicated in the meeting of September 27, 1902). 
The character of the equilibria of phases is exclusively determined 
by the number of independently variable constituents — components — 
of which the system is built up. 
Sometimes this is equal to the number of the different kinds of 
molecules. It may also be smaller, if there are among the molecules 
those which may pass into each other as in the case of associating, 
ionizing or isomeric substances. If these molecular changes proceed 
more rapidly than the equilibria of the phases, they exercise no 
influence on them. 
Although water, for example, is a mixture of at least two kinds 
of molecules, its freezing point is quite as sharply defined as that 
of a single substance. 
If however, the velocity of the molecular change is small, the 
system on being treated rapidly will behave like one with more 
components than it shows if treated more slowly. The effect of 
this on the phenomena of solidification has already been mentioned 
by Bancrorr in 1898 and by myself in 1899. So far, however, 
no suitable example has been found which would enable us to consider 
1) It demonstrates, for instance, in a simple manner that on compressing vapour 
mixtures with a sufficient amount of A, the component B first deposits in the 
solid state in increasing quantity, but then again completely disappears at a certain 
pressure to make room for a liquid phase, 
This phenomenon has recently been observed by Kuenen (Phil. Mag. July 1902) 
with solid CO, mixed with CjHg. 
It must always show itself with the component which in the liquid-mixtures is 
the least volatile: in this case B. When however, the liquid-surface has a maximum 
pressure as in the instance cited by Kurnen, the phenomenon will be noticed with 
both components. If the surface has a minimum pressure it can only occur with 
one of the two. 
