The present research interprets various binary, ternary and quaternary interactions using a generalised liquid solution model for the Ga-In-As-Sb alloys at 973 and 1073 K. The excess free energy equations for the liquid and solid solutions are used in conjunction with the solid-liquid equilibrium data in order to express equilibrium properties including the evaluation of the quaternary interactions in the alloys. The use of the derived values of the equation enables one to interpret the phase equilibria and thermodynamic properties of the system. (C) 2004 Elsevier B.V. All rights reserved.