Observation of a combined dilution and salting effect in buffers under conditions of high dilution and high ionic strength

The pH value of buffer solutions is crucially dependent on the relative concentrations of all species in solution. The addition of water or neutral salt can have a significant effect on the pH of a buffer solution. This study examines the magnitude of the 'dilution effect' and the 'salt effect' for several commonly used inorganic and biological buffers. Novel data are obtained for the change in pH observed upon dilution or addition of neutral salt to these buffers which add to, complement and extend existing literature values. The validity of considering the dilution and salt effects as a combined ionic strength effect is also considered as well as the ability of the pH measuring device to perform valid measurements in these extreme conditions.