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本文用玻璃电极和氢电极,与Ag/AgCl电极分别构成两个电池,测定了HCl-NH_4Cl-H_2O体系在25℃,总浓度在0.1～3.0mol·kg~(-1)范围内的电动势。结果表明,玻璃电极电势不遵从Nernst方程,按离子交换平衡原理,讨论了铵离子对玻璃电极不对称电势的影响,导出了电极电势表达式为,式中为纯盐酸中玻璃电极的不对称电势,a_A为H~+的活度,Y_B为NH_4Cl的摩尔分数,S为Nernst斜率,K为离子交换平衡常数,α、β为实验参数。
In this paper, two electrodes were composed of glass electrode, hydrogen electrode and Ag / AgCl electrode respectively. The electromotive force of HCl-NH_4Cl-H_2O system at 25 ℃ and the total concentration of 0.1 ~ 3.0mol · kg -1 was measured. The results show that the potential of the glass electrode does not follow the Nernst equation, and the effect of ammonium ion on the asymmetric potential of the glass electrode is discussed according to the principle of ion exchange equilibrium. The expression of the electrode potential is derived as follows: where the asymmetric potential of the glass electrode in pure hydrochloric acid , a_A is the activity of H ~ +, Y_B is the mole fraction of NH_4Cl, S is the slope of Nernst, K is the ion exchange equilibrium constant, and α and β are the experimental parameters.