Spectrophotometric determination of dissociation constants for propionic acid and 2,5-dinitrophenol at elevated temperatures

Using the temperature dependence of pK_a for acetic acid, the pK_a for 2,5-dinitrophenol have been spectrophotometrically determined in acetate buffer at elevated temperatures under the saturation vapor pressures. For 2,5-dinitrophenol {Mathematical expression} where T is in Kelvin. Similarly, pK_a values of propionic acid were obtained at temperatures from 25°C to 175°C producing {Mathematical expression} From this result, several thermodynamic functions of propionic acid were calculated and compared with those obtained from emf measurement.