Use of the pitzer equations to examine the dissociation of TRIS in NaCl solutions

The TRIS buffer system is frequently used to calibrate electrodes and indicators that are used to determine the pH of natural waters. Most of the potentiometrie and spectrophotometric systems used to measure the pH are calibrated with TRIS buffers. Since most natural waters contain high concentrations of NaCl, it is useful to be able to determine the pK of TRIS using ionic interaction models. In this paper, the dissociation constants of TRIS in NaCl solutions from (0 to 100) °C and (0 to 5) mol·kg ^-1 have been fitted to Pitzer equations. This allows one to estimate the values of the pH for TRIS buffers for natural brines over a wide range of conditions.