In this case the freezing point may rise (as in the case of silver and zinc), and one of the eutectic points will be absent.
From our curve we should expect a eutectic mixture with about 35 per cent.
The point X, therefore, does not correspond with a eutectic point, but with a transition point.
C is the eutectic point at which the two solid isomerides can exist side by side in contact with the solution.
A “eutectoid” is to such a transformation in solid metal what a eutectic is to freezing proper.
At the eutectic point (15.6), these two solid phases could co-exist with the liquid phase.
If the initial composition of the magma is represented by a point between the two eutectic points, orthoclase will separate first.
The length of time during which the temperature remains constant at the point c, depends, of course, on the eutectic solution.
It is known as the cryohydric point, or, generally, the eutectic point.
In this way we get the freezing point curve Ak1B for the binary system; k1; being an eutectic point.