High precision measurements of alkalinity and total carbon dioxide in seawater by potentiometric titration. 2. Measurements on standard solutions

Abstract

We have prepared standard solutions identical to those of Hansson for the validation of titration procedures used to determine the alkalinity and total carbon dioxide content of seawater. We show that both titrimetric and gas extraction (coulometry) procedures yield virtually identical results of 2140.5 ± 2.7 μm CO 2 kg −1 for such solutions. In an earlier work we reported that measurements on natural seawaters yielded discrepancies of 21 μm CO 2 kg −1, which we tentatively ascribed to the presence of unknown organic acids masquerading as CO 2 in the titration scheme, and generally unrecognized in thermodynamic models of the proton condition of seawater. The results presented here tend to confirm this hypothesis.