Abstract: A new geometric asymmetric model for predicting the thermodynamic properties of ternary system from three sub-binaries is presented in this paper.Its analytical expression with good calculating ac- curacy is most simple in all asymmetric models.The new model was applied to predict the enthalpies of mixing of the Bi-Ga-Sn.Au-Ag-Sn and NaCl-KCl-CaCl_2 ternary systems which were in good agreements with experimental data.Based on thermodynamic principles,the importance of the choice of asymmetric component is also discussed.The error analysis indicates that in the case of judging the asymmetric component in ternary system according to the thermodynamic criterion the deviation is minimum.It is of great significance to improve the calculating accuracy for predicting thermodynamic properties of ternary solution phase from the sub-binary ones.

Key words: thermodynamic properties, ternary system, geometric asymmetric model