Using the values of water-apolar liquid, glycerol-apolar liquid, formamide-apolar liquid, and ethylene glycol-apolar liquid surface or interfacial tension taken from the. literature, the relationships between phi parameter of interfacial interactions and interfacial tensions were determined both graphically and mathematically, Next, the so-called "alpha" and "beta" values obtained in this way were used for the solution of the equation of state for interfacial tensions for liquid-liquid and polymer-liquid systems. The results obtained from the calculations have shown that the alpha and beta values are not constant, but depend on the kind of polar-apolar liquid system and the way the values are determined, The values of alpha and beta differ from 0.0075 and 1, respectively, It has been found that it is impossible to predict the interfacial tensions of polar-apolar liquids as well as polymer-liquid systems with good accuracy on the basis of alpha = 0.0075 and beta = 1, and alpha and beta values have also been determined from polar-apolar liquid interfacial tensions.