The Effect of Pressure on the Dissociation of Carbonic Acid from Measurements with Buffered Glass Electrode Cells

Abstract

The effect of pressure on the dissociation of carbonic acid has been investigated over a wide range of pH and ionic strength (0–1.0) in and , using junctionless glass electrode cell measurements. At and for the first and second ionization steps, respectively. The directly measured or shifts induced by pressure in sea water between are explained by the enhanced dissociation of , , , and , the effect of and the interference of boric acid . Values of the ionization functions and of carbonic acid, valid in natural seawater, have been determined at 22 °C, at 1 atm and at 1000 bars together with the apparent dissociation constants ( and used in oceanography to calculate , from in situ values. Corrections are given for different types of reference half‐cells, and an approach toward the absolute values of and in sea water is indicated.