A Working Model for the System Alumina-Magnesia.

For treatment of internal explosions in the presence of both Mg and Al metals, it was necessary to devise a working model for the system magnesia-alumina. From the parameters of the model it was then possible to estimate equilibrium and internal-energy data for the various chemical species present in the oxide system, both in solid and liquid phases, for use in the blast computations. The solid phases, in agreement with published phase diagrams, consist of a magnesia phase, in which a small amount of spinel magnesium aluminate dissolves a spinel phase in which either magnesia or alumina is soluable to a considerable extent and a pure alumina phase. The solid phases were treated by the methods of the thermodynamics of non-ideal solutions. The melt was assumed to contain chemically reasonable ions, plus unionized MgO, and to behave as an ideal solution. The parameters of the model were adjusted to give the most satisfactory fit to the known phase diagram. It is emphasized that the model does not purport to be an actual explanation of the structure of the system. Author