1335 
The tenor of this theory may be summarized under the four 
following points: 
1. Every allotropic substance belongs to a pseudo-system and 
the different kinds of molecules of this substance are the pseudo- 
components, which are more or less miscible in the solid state. 
2. An arbitrary three-dimensional spacial figure of a unary system, 
in which the concentration is plotted along one of the axes, consists 
of a number of internal equilibrium surfaces, which are necessarily 
situated’ in the corresponding spacial figure of the corresponding 
pseudo system. 
At the place where these surfaces of internal equilibrium intersect 
the surfaces for the stable and metastable heterogeneous equilibria 
of the pseudo system, coexistence takes place between different 
phases of the nnary system which differ from each other in concen- 
tration. Hence in the unary system the conversion of one coexisting 
phase to the other will always be attended with a chemical reaction. 
3. The phenomena of monotropy and enantiotropy appear here 
in a new light; they are closely allied phenomena, and it appears 
at the same time that the difference in crystalline form between 
the modifications of one and the same substance are in causal con- 
nection with the difference in situation of the internal equilibrium. 
4. The changes in properties which may be found under certain 
circumstances when a wnary system is made to pass through an 
arbitrary process with a comparatively great velocity (variation of 
temperature, variation of pressure, evaporation, solution etc.) must 
be ascribed to a disturbance of the internal equilibrium of the 
considered system. 
In the development of this theory use has been made of GrBBs’s 
principle of equilibrium, which says that every system of substances 
at constant temperature and pressure tends to that state the thermo- 
dynamical potential of which is a minimum. When applying this 
principle, we arrive at the result that when e.g. the property of 
transformation into each other is assigned to the components of a 
system which was before thought to be binary, in consequence of 
which the system becomes unary, the thermodynamic potential of 
a certain state of aggregation, which is now a unary phase, must 
lie at a definite temperature and pressure in the minimum of the 
S,x-line, which relates to the binary mixtures of the same state of 
ageregation as the unary phase mentioned just now. 
This can be elucidated in the following way: 
The total differential of the thermodynamic potential of a binary 
mixture is; 
