Rilbe H
Electrophoresis. 1993 Dec;14(12):1271-7. doi: 10.1002/elps.11501401194.
A general theory for buffers consisting of one weak acid and one weak base is developed, particular interest being devoted to the special case of doubly weak salts. The pH course as it varies with the acid/base concentration ratio is presented in equations and graphs. The influence of delta pK' = pK'b-pK'a, which can be negative as well as positive, is discussed and visualized in graphs. The buffer capacity is deduced as a function of pH. The buffer range is, at a maximum, 2.67 times that of a monovalent weak protolyte for delta pK' = 2.7 pH units. The buffer capacity curve has two maxima for delta pK' values bigger than 0.77. For negative delta pK' values the buffer capacity curve has only one maximum, and the buffer range is not better than that of a monovalent protolyte. A general equation for the ionic concentrations is deduced, and as a corollary the degree of hydrolysis of the doubly weak salt is obtained as a function of delta pK'. For solutions of this salt, the relation between concentration and pH is elucidated by equations and graphs.
本文建立了一种由一种弱酸和一种弱碱组成的缓冲剂的通用理论，特别关注了双弱盐的特殊情况。通过公式和图表展示了pH值随酸/碱浓度比变化的过程。讨论了δpK' = pK'b - pK'a（其可为正也可为负）的影响，并通过图表进行了直观展示。推导出了缓冲容量作为pH值的函数。对于δpK' = 2.7个pH单位，缓冲范围最大为单价弱质子转移体的2.67倍。当δpK'值大于0.77时，缓冲容量曲线有两个最大值。对于负的δpK'值，缓冲容量曲线只有一个最大值，且缓冲范围不优于单价质子转移体。推导出了离子浓度的通用方程，并由此得出双弱盐的水解度作为δpK'的函数。通过公式和图表阐明了该盐溶液中浓度与pH值之间的关系。
