用汽液平衡法研究NaI在乙醇-环己烷中的活度系数

Study of Activity Coefficients for Sodium Iodide in Ethanol-hexamethylene System by Vapor-liquid Equilibrium Measurements

测定了乙醇-环己烷-NaI体系常压汽液平衡数据,采用双标准检验法对数据进行检验,检验结果全部合格.假定NaI的平均活度系数可表示为盐浓度平方根(m1/2)的幂级数,采用全部合格的汽液平衡数据拟合出幂级数中的各项参数,从而获得在双液比固定条件下盐在非水混合体系中的活度系数.计算结果表明,正常泡点温度下,在具有固定双液比的乙醇-环己烷混合溶剂中,NaI的平均活度系数随盐浓度的增加而减小.此法可推广于其他非水混合溶剂中电解质活度系数的测定.

By measuring the vapor-liquid equilibrium of ethanol-hexamethylene-NaI and verifying the data by means of ternary Gibbs-Duhem equation,the data of the vapor-liquid equilibrium of ethanol-hexamethylene-NaI were in agreement with both criterions.It is supposed that the mean activity coefficients of NaI may be represented by power of m1/2.Then each parameter of power equation was fitted.The results of calculation show that at the equilibrium temperature and pressure the activity coefficients of NaI in ethanol-hexamethylene system with fixed composition decrease as its concentration increases. This method is adapted to determination of electrolytical activity coefficients in non-aqueous solvents.