680 
NaCl ete. the difficulty with regard to the valence would disappear, 
but then there would be no atoms, but ions, in the lattice points, 
and a chemical binding would not occur. Accordingly, the 
replacement of the atoms by ions in Brage’s image would already 
be an important modification for the said substances in the right 
direction. 
Of late Desir’) has published results that seem to prove that 
this is really the case with LiF. 
It is hardly necessary to observe that for all other compounds, 
which are. built up of more than two elements, and yield compound 
ions, the valency must find expression, because also on complete 
dissociation in the solid state this compound ion must be present as 
a group. But also for a compound composed of two elements, as 
Hel,, the assumption of complete dissociation into ions cannot lead 
to a solution, because this does not account for the existence of 
internal equilibria. 
I will, however, not continue this train of reasoning any further 
here; it only served to call attention once more to the fact that 
from a chemical point of view, the action of the valency in the 
solid substance cannot be disregarded; hence it is clear that it is 
desirable to find other methods which may teach us something about 
the internal condition of the crystallized substance. 
Some years ago I had already formed the plan to examine whether 
Nernst’s law of partition is valid for the coexistence of a mixed 
crystal phase with a solution. 
It is clear that Nernst’s law of partition can only be valid for 
this case, when the ordinary thermodynamic considerations, which 
lead to this law in equilibria between a gas and a liquid phase or 
between two liquid phases, may also be applied to the solid sub- 
stance. This is the fundamental question ! 
Van ’t Horr’), who was the first to point out in 1890 that there 
are states which may be designated by the name of solid solutions, 
embraced the opinion that the theory of diluted liquid solutions 
might be applied to these states. 
BakHuis Roozesoom ®), who started his important experimental 
researches on mived crystals a year later, practically treated the 
mixed crystals thermodynamically already in the same way as the 
liquid solutions had been treated, and it might be said that the 
experiment has justified this procedure, as the derived types were 
1) Phys. Zeitschr. 19, 474 (1918). 
1) Z. f. Physik, Chem. 5, 322 (1890). 
3) Z. f. Physik. Chem. 8, 504 (1891). 
