This study allowed us to establish a procedure for determining the pH of seawater by the primary method using cell without junction (Harned cell) in artificial seawater without sulfate ASW-SO4 which is taken as a reference buffer solution featuring the natural seawater at salinity 35 and an ionic strength equal to 0.6731 mol kg-1. The determination of the coefficient average activity (γ ± HCl) of HCl was taken from two approaches. The first one is an experimental approach in which we introduced the potential standard value (E°) calculated in dilute media. In the second approach, we applied and adapted the Pitzer model in function of the temperature (15, 25 and 35 °C) taking into account all the parameters of the solution in ionic interactions and we demonstrated its feasibility for the solution ASW-SO4. The choice was made for the first option which was preferred because of its simpler implementation.
Achour M. B., Guesmi F., Marzouk I. & Hannachi C., in press. Toward a primary measurement procedure for pH in seawater: comparison of mean activity coefficients in saline aqueous matrices. Accreditation and Quality Assurance. Article.
