pH是一个常见的基本概念,但由于pH定义不统一,在许多教科书以及专著中比较混乱。因为溶液中单个离子的活度是无法直接测量的,在稀溶液中,通过德拜一休克尔(Debye—Huckel)理论的计算也只能得到平均离子活度系数。那么,我们用pH计测量得到的数值将是什么值?它同真实值相比误差有多大?鉴于这些存在的问题,有必要深入地讨论一下有关pH的定义以及测量值的意义。 pH is a common basic concept, but confusion exists in many textbooks and monographs because of the inconsistent definition of pH. Because the activity of individual ions in a solution can not be measured directly, only the average ion activity coefficient can be obtained from a Debye-Huckel theory in dilute solutions. So what is the value we measure with the pH meter? What is the error compared with the real value? Given these problems, it is necessary to discuss in depth the definition of pH and the significance of the measurement.