Abstract
Exact relations between pH and concentrations of water solutions of acids, bases, and simple ampholytes are presented in the form of computer‐created curves. These are mathematically analysed with respect to linearity and inflexion points. The extreme invariance of pH in the immediate vicinity of the isoelectric points of ampholytes is demonstrated in curves of the logarithm of molarity as a function of the logarithm of | pH − pI |. These considerations include a discussion of the suitability of ampholytes as pH standards.