Glossary of Terms for Phase Equilibria Diagrams
- Heterogeneous Equilibrium
A system is heterogeneous and is in heterogeneous equilibrium when it consists of two or more
homogeneous portions (phases) in equilibrium with each other.
In the usual consideration of the phase rule, changes in equilibrium due to electrical, magnetic, capillary,
and gravitational forces are not considered; but only those changes due to temperature, pressure, and concentration.
Reference: Levin, E.M., McMurdie, H.F., and Hall, F.P., Phase Diagrams for Ceramists: Volume 1,
The American Ceramic Society, Columbus, Ohio, p. 6, 1956.
- Homogeneous Equilibrium
A system is homogeneous and is in homogeneous equilibrium when it consists of one
phase and all processes or reactions occurring within it are in reversible equilibrium.
A homogeneous phase need not consist of one atomic or molecular species, e.g., in the single
phase system sodium chloride solution, Na+, Cl-, H3O+,
OH-, H2O, and associated molecules may all be present but the reactions
involving them are at equilibrium.
Reference: Levin, E.M., McMurdie, H.F., and Hall, F.P., Phase Diagrams
for Ceramists: Volume 1, The American Ceramic Society, Columbus, Ohio, p. 6, 1956.