Acidic Dissociation Constant and Related Thermodynamic Quantities for Diethanolammonium Ion in Water From 0 to 50 °C

The dissociation constants of diethanolamine (2:2′-dihydroxydiethylamine) and its conjugate acid were determined by electromotive force measurements of the cell [Formula: see text] in the temperature range 0 to 50 °C. The acidic dissociation constant (K(bh)) of the diethanolammonium ion is given by [Formula: see text] where T, the temperature on the Kelvin scale, lies between 273.15 and 323.15°. From this equation were calculated ΔG°, the change in free energy; ΔH°, the change in heat content; ΔS° the change in entropy; and [Formula: see text] , the change in heat capacity that accompany the dissociation of 1 mole of diethanolammonium ion in the standard state. At 25 °C, −log K(bh)= 8.883; ΔG°=50,682 joule mole(−1); ΔH°=42,400 joule mole(−1); ΔS°=−27.8 joule deg(−1)mole(−1); and [Formula: see text] joule deg(−1)mole(−1).