THE MEASUREMENT OF SEA-WATER PH

This paper reviews the thermodynamic basis of two approaches that are used to measure the total hydrogen ion concentration of sea water, potentiometry using a glass electrode and spectroscopy using an indicator dye. Both of these methods depend ultimately on measurements made using the classical hydrogen/silver-silver chloride cell for their calibration and thus provide equivalent pH scales. As a result of recent advances in measurement techniques and calibration, we should expect to see a revival in the popularity of pH measurements and a renewed understanding of the importance of this parameter in interpreting acid-base processes in sea water; particularly those involving the geochemically important carbon dioxide system.