Suppose, now, that the temperature is that of the transition point.
In the case of sulphur, the transition point of rhombic into monoclinic sulphur was found by Reicher to lie at 95.5.
There is, therefore, no transition point, and transformation of the crystalline forms can be observed only in one direction.
In such cases the transition point could be reached only at higher pressures.
The triple point S-S-V is not precisely the same as the transition point, but is very nearly so.
For β- and γ-ferrite, the transition point is about 870, the γ- form being the stable modification above this temperature.
If the two single salts have identical solubility at the transition point, the transition interval diminishes to nought.
This diagram explains very clearly the phenomenon of the decomposition of a double salt at the transition point.
Below the transition point, therefore, the solubility of the racemate is less than that of the mixed tartrates.
The point X, therefore, does not correspond with a eutectic point, but with a transition point.