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 potentiometric 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.

[1]  C. Rigano,et al.  Analysis of thermodynamic data for complex formation : Protonation of tham and fluoride ion at different temperatures and ionic strengths , 1999 .

[2]  F. Millero,et al.  The standard potential for the hydrogen-silver, silver chloride electrode in synthetic seawater , 1993 .

[3]  C. Culberson,et al.  Acid-base properties of tris(hydroxymethyl)aminomethane (Tris) buffers in sea water from 5 to 40.degree.C , 1977 .

[4]  Jerry P. Greenberg,et al.  The prediction of mineral solubilities in natural waters: A chemical equilibrium model for the Na-K-Ca-Cl-SO4-H2O system to high concentration from 0 to 250°C , 1989 .

[5]  Robert H. Byrne,et al.  High precision multiwavelength pH determinations in seawater using cresol red , 1989 .

[6]  R. Bates,et al.  Activity and osmotic coefficients oft-butylammonium chloride; Activity coefficients of HCl in mixtures with tris hydrochloride ort-butylammonium chloride at 25°C , 1985 .

[7]  F. Millero.  The physical chemistry of natural waters , 1985 .

[8]  N. Møller,et al.  The prediction of mineral solubilities in natural waters: A chemical equilibrium model for the Na-Ca-Cl-SO4-H2O system, to high temperature and concentration , 1988 .

[9]  Robert H. Byrne,et al.  Spectrophotometric seawater pH measurements: total hydrogen ion concentration scale calibration of m-cresol purple and at-sea results , 1993 .

[10]  F. Millero,et al.  A Chemical Equilibrium Model for Natural Waters , 1998 .

[11]  T. A. DelValls,et al.  The pH of buffers based on 2-amino-2-hydroxymethyl-1,3-propanediol (‘tris’) in synthetic sea water , 1998 .

[12]  F. Millero.  The pH of estuarine waters , 1986 .

[13]  R. Byrne,et al.  Spectrophotometric determination of freshwater pH using bromocresol purple and phenol red. , 2001, Environmental science & technology.

[14]  S. Husheer,et al.  Spectrophotometric pH measurement in estuaries using thymol blue and m-cresol purple , 2004 .

[15]  F. Millero,et al.  The pK∗ of TRISH+ in Na-K-Mg-Ca-Cl-SO4 brines—pH scales , 1987 .

[16]  M. DeGrandpre,et al.  Spectrophotometric pH measurements of freshwater , 2002 .