REPRESENTATION OF PHASE-EQUILIBRIA IN QUATERNARY SYSTEMS

In this paper, a review of the basic principles of construction of qua ternary phase diagrams is presented. The tie-tetrahedron representing univariant equilibrium and the merger of several tie-tetrahedra during a quaternary invariant reaction are discussed. The use of the law of adjoining phase regions and the cross-rule to check the correctness of construction of quaternary diagrams is illustrated. The applicability of the Schreinemakers' rule to all multicomponent systems at points w here four phase boundaries meet is demonstrated. Recommendations are m ade for an uniform nomenclature for invariant reactions in quaternary systems.