Buffers are solutions that are made up of equal concentrations of a weak base and its conjugate acid (or a weak acid and its conjugate base) that resist changes in pH when small amounts of strong acid (such as hydrochloric acid) or base (such as sodium hydroxide) are added. They are important in natural systems and play an important role in the operation of many biological, industrial and environmental processes. In this experiment it introduces the glass pH electrode - the standard instrumental technique for the measurement of pH.