The pH of buffers based on 2-amino-2-hydroxymethyl-1,3-propanediol (‘tris’) in synthetic sea water

E.m.f. measurements were made over the temperature range 273.15–318.15 K, and at five salinities from 20 to 40, using the cellPt(s) H2(g, p°) BH+ and B insynthetic sea water AgCl(s) Ag(s) Pt(s)where p°=101.325 kPa, and BH+ and B are the conjugate acid–base pair of 2-amino-2hydroxymethyl-1,3-propanediol (‘tris’) – each present at a concentration of 0.04 mol kg-1. The results were used to assign pH values based on the ‘total’ hydrogen ion scale to such buffer solutions based on this acid–base pair. Additional measurements were made over a range of buffer concentrations at a salinity of 35; these were used to calculate the stoichiometric (ionic medium) dissociation constant for ‘tris–H+’ in synthetic sea water.