用玻璃电极测定直到15m的浓盐酸体系的活度系数

DETERMINATION OF MEAN ACTIVITY COEFFICIENTS OF HYDROCHLORIC ACID IN CONCENTRATED SOLUTIONS UP TO 15m WITH GLASS ELECTRODE

本文在25℃下,对0.01844—15.02mol kg浓度范围内的盐酸体系,用自制Agl AgGl电极和氢电极,测定了Harned电池的电动势。在此基础上,以玻璃电极代替氢电极,测量上述盐酸体系的电动势,计算了HCl的平均活度系数和HO的活度。实验结果表明,玻璃电极在浓盐酸体系的“标准电势”是稳定的,且遵从Nernst响应,重现性良好,响应速度快;在高浓度和稀溶液中交替测量时,电势无明显偏差。这说明电极有较好的可复性。求得的HCl的活度系数与文献值偏差小于1.2%。玻璃电极的“标准电势”的标准偏差为0.016%。

Mean activity Coefficients of HCl in concentrated hydrochloric acid solutions are determined by measuring emf’s of following cells (A). Ag-AgCl/HCl(m)/H(P)/Pt(black) (B). Ag-AgCl/HCl(m)/pH-glass electrode for HCl molalities from 0.01844 to 15.02 tool kgat 25℃. Using observed emf data of ceils (A) and (B), mean activity coefficients of HCl are calculated, and their deviations are less than 1.2%. Within this molality range, "standard potential" E~0 of pH-glass electrode is a constant and its standard deviation is equal to 0.016%. The pH-glass electrode used has good reproducibility. Therefore, it is possible to determine the activity coefficients in high concentrated hydrochloric acid solution by using pH-glass electrode. For concentrated hydrochloric acid in molality range 0.1844—15. 02 mol kgat 25℃, the lograrithm of activity coefficients of HCl can be expressed adquately by the equation: Iog γ=-(0.5115m)/(1+1.471m)+0.1069m+7.412×10m-6.637×10m~3+1.586×10m~4 where m is the HCl concentration in molality, γis its activity coefficients.Using this equation, activities of solvent HO have been calculated.