电势法测定KI在CH_3OH-H_2O混合溶剂中的活度系数

用无液接电势电池测定了303.15 K时,KI在甲醇-水混合溶剂中的电动势,用扩展的Debye-Hückel方程及Pitzer方程关联不同溶剂组成下电动势的实验值,得到电池的标准电动势E°和KI在混合溶剂中的活度系数.结果表明,在一定的溶剂比例下,随KI浓度的增大,其平均活度系数先随它的浓度增加而下降,经过一个最低点后又上升;或者随浓度增加而单调递减.当KI浓度固定时,它的平均活度系数随溶剂中甲醇的含量增加而下降.表明KI在甲醇中有微弱的缔合.

Activity Coefficients of Potassium Iodide in Methanol-Water Mixed Solvents by Electromotive Force Measurements

The electromotive force of a galvanic cell composed of K selective electrode and I-selective electrode pair dipping in a mixed solution of CH3OH-H2O was detected at 303.15 K.By using the Nernst equation and measured electromotive force data,the corresponding mean activity coefficients of KI and interaction parameters were obtained.The weak association of KI in methanol was discussed.At each fixed solvent composition,the mean activity coefficients of KI decrease at first and then increase with KI molality increases.At each fixed KI molality,the activity coefficients decrease with an increase of methanol in solvent mixtures.