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

Abstract

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 cell Pt( s) H 2( g, p°) BH + and B in synthetic 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.