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本文利用近十几年内发展起来的Pitzer方程表达配合平衡中各个电解质的活度系数,假设支持电解质的离子强度可近似地代表平衡体系的离子强度,并把Pitzer方程中的因子exp(-βμ~(1/2))展成级数,忽略高次项,从而使Pitzer参数B,B’皆与离子强度无关,于是得到: logK_μ+((0.39211△z~2)/(ln10))[((μ~(1/2))/(1+1.2μ~(1/2))+(5/3ln(1+1.2μ~(1/2))]=logK_0+A_1μ+A_2μ~2 (1)式中K_μ和K_0分别为配合物在一定离子强度μ下的逐级稳定常数和逐级热力学稳定常数,△z~2为配合反应中产物和反应物的电荷平方差,A_1,A_2为经验参数.根据方程式(1),利用曲线回归技术可以得logK_0.为了校正本公式推演过程中的两点假设,式(1)右边加上三次项,得到三次曲线方程式;考虑到计算和外推方便,舍去式(1)右边二次项,得到线性方程式.用本文的三种方法处理了前人的实验数据,与传统的方法相比,本文所提供的三种方法都可得到满意的结果.
In this paper, the Pitzer equation developed in recent ten years is used to express the activity coefficients of each electrolyte in the equilibrium. Assuming that the ionic strength of the supporting electrolyte can approximately represent the ionic strength of the equilibrium system, the factor exp (-βμ ~ (1/2)), ignoring the higher order terms, so that Pitzer parameters B and B ’are independent of the ionic strength, thus obtaining: logK_μ + (0.39211 Δz ~ 2) / (ln10) (μ ~ (1/2)) / (1 + 1.2μ ~ (1/2)) + (5 / 3ln (1 + 1.2μ ~ (1/2)]] = logK_0 + A_1μ + A_2μ ~ 2 ) Where K_μ and K_0 are the step-by-step stability constants and the stepwise thermodynamic stability constants of the complex at a certain ionic strength μ, respectively, Δz ~ 2 is the charge-squared deviation of the products and reactants in the reaction, A_1 and A_2 are empirical Parameter. According to equation (1), using curve regression technique can get logK_0. In order to correct the two-point hypothesis in the process of deducing this formula, add the cubic term to the right of equation (1) to get the cubic curve equation. Considering the convenience of calculation and extrapolation , And the right quadratic term of (1) is discarded to get the linear equation.Three methods of this paper are used to deal with the experimental data of our predecessors. Compared with the traditional methods, all the three methods provided in this paper can get Satisfied with the result.