If the temperature is altered, the vapour pressure and also, in general, the concentration will undergo change.
It is possible that at some temperature the vapour pressure curve of a lower hydrate may cut that of a higher hydrate.
At this transition temperature two vapour pressure curves cut, viz.
In general, when the substance to be distilled has a vapour pressure of only 10 mm.
In the case of this system the vapour pressure increases as the temperature rises, as represented by the curve FG.
Thus, at any given temperature, the vapour pressure of the system and the concentration of the components have a definite value.
This is the curve of vapour pressure, or the vaporization curve of water.
When the components are completely immiscible, the vapour pressure of the one is not influenced by the presence of the other.