In view of that polyesterification reactions of diols with some aryl diacids consists of the non homogeneous and homogeneous reaction stages

two equations were proposed for calculation of the solubilities of aryl diacids in reaction mixtures and of the “clear points” of reactions

respectively.On the basis of the two equations

the kinetic model proposed by Chen and Wu for self catalyzed polyesterification reactions was modified into two rate equations which were used for the non-homogeneous and homogeneous reaction stages

respectively.The two rate equantions fitted the exoerimental data well

as was confirmed by the reaction of bis(4-carboxyphenyl) phenyl phosphine oxide with ethylene glycol under constant reaction temperatures of 180～197℃ and at different ratios of diol to diacid

whose rate constant and activation energy were calculated.The reaction rate constant was affected by temperature according to Arrhenius'law.The results of application of the two calculation equations of solubility and clear point and of the two rate equations shows that these equations were reasonable.