ivor and olive lewis on wed 2 nov 11
The obvious thing to ask is "Which came first, the chicken or the egg".
In a strict sense, the compounds you name have to pre-exist in your assembl=
of materials (the "egg" situation) to activate a eutectic reaction.
Otherwise they must form during cooling from a homogenous melt as it change=
from liquid to solid. (The "Chicken" event). A composition now exists which
has the potential to melt at a eutectic temperature point.
A simple classic example is the 1170 deg C Eutectic in the system
CaO-Al2O3-SiO2.. A formulation based on Whiting, Quartz and Aluminium
Hydrate will not melt when raised to 1200 deg C but a mixture of
Wollastonite, Anorthite and Tridimite might, if you could persuade the
Quarts to change phase to Tridimite! !