Buffers

Rather than simply measuring the pH of a solution, you may wish to control the pH, during EDTA complexation titrations or preparative experiments involving carbonyl compounds, and one of the most effective ways to control pH is to use a buffer solution.

A buffer solution is usually a mixture of a weak acid and its conjugate base. Added protons will be neutralized by the anionic base while a reduction in protons, e.g. due to the addition of hydroxyl ions, will be counterbalanced by dissociation of the acid (eqn [7.2]); thus the conjugate pair acts as a 'buffer' to pH change.

The British standard for the pH scale is an aqueous solution of potassium hydrogen phthalate (0.05 M), which has a pH of 4.001 at 20°C and is often used as a calibration solution for pH meters.