Thermodynamics and dissociation constants of carboxylic acids at high ionic strength and temperature

• Published in: Inorganica Chimica Acta Vol. 360; no. 12; pp. 3671 - 3680
• Main Authors: Thakur, P., Mathur, J.N., Moore, R.C., Choppin, G.R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-09-2007
• Subjects: Aminopolycarboxylic acid SIT; Carboxylic acid; Dissociation constants; Parabolic; Thermodynamics; Thermodynamics; Aminopolycarboxylic acid SIT; Parabolic; Carboxylic acid; Dissociation constants
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2007.06.002

Thermodynamic parameters and dissociation constants of carboxylic acids at high ionic strength and temperature were determined by the potentiometric titration method. The specific ion interaction theory (SIT) and the Parabolic model successfully described the ionic strength dependencies of the p
K
a values.
Dissociation constants (p
K
a) of oxalic, iminodiacetic, citric, nitrilotriacetic, ethylenediaminetetraacetic, trans-1,2 diaminocyclohexanetetraacetic acid and diethylenetriaminepentaacetic acid have been determined potentiometrically using a glass electrode at an ionic strength of 6.60
m (NaClO
4) and temperatures of 0–60
°C. The constants of iminodiacetic, nitrilotriacetic and diethylenetriaminepentaacetic acid were measured at 25
°C at ionic strengths from 0.30 to 6.60
m (NaClO
4). The thermodynamic parameters for the dissociation of these carboxylic acids were derived from the temperature dependence of the dissociation constants. The Specific Ion Interaction Theory (SIT) and the Parabolic model successfully described the ionic strength dependencies of the p
K
a values. The variation of the p
K
a values at high ionic strengths as a function of the type and concentration of supporting electrolyte is discussed and compared with literature data.