( 646 ) 
9. Now, that we have sufficiently characterised the three general types, 
and have brought some harmony into the multiplicity of the phenomena, 
the question arises, whether there is a still farther synthesis, a still higher 
unity. More than once the occasion presented itself in the treatment of 
the different general types to remark striking agreements and continuous 
transitions, often accompanied with great differences. Equally the 
fact, that with a higher alcohol or a higher hydrocarbon, suddenly a 
quite different type often appears, must certainly draw attention in 
a high degree. All this induces us to look for the one fundamental 
type, of which the three types, treated above, are special cases. 
Also the analytical consideration of the question suggests that idea 
to us. Indeed, the coexistence of two liquid phases and one gaseous 
phase, or of two liquid phases, or finally of one liquid phase and 
one gaseous phase, is determined by one and the same equation of 
state, and it must consequently always be possible to reduce all the 
different cases, which may occur to #vo fundamental proportions : 
that of the critical temperatures and that of the critical pressures of 
the two components — entirely in the same way as I have formerly 
deduced al/ the different types in the case of mixed crystals, where 
appear two solid phases by the side of one liquid phase, from two 
fundamental proportions: that of the meltingtemperatures and that 
of the latent heats of melting of the two components. 
In a following communication it will be shown theoretically, that 
the three types may be deduced from the ordinary equation of state 
of Prof. vaN per Waals, even in the case of normal components. In 
connexion with this we must not forget, that in the neighbourhood 
of the eritical points of each of the components the influence of 
anomaly vanishes nearly always. In the case of C,H, + H,O for 
instance the water will be in the neighbourhood of 365° C. already 
normal long before, and in the neighbourhood of 32° C. the liquid 
phase, which consists nearly entirely of ethane, will contain the water 
in such a dilute state, that this will be passed for the greater part 
into the state of simple molecules. 
Chemistry. — “An exact expression for the course of the spinodal 
curves and of their plaitpoints for all temperatures, in the 
case of mixtures of normal substances.” By J. J. van Laar. 
(Communicated by Prof H. A. Lorentz). 
(Communicated in the meeting of March 25, 1905.) 
1. It is well-known, that the points of the ¢-surface, corresponding 
to points of the spinodal curve on the y-surface, are given by the 
simple relation 
