Abstract
The dissociation constants of diethanolamine (2:2′-dihydroxydiethylamine) and its conjugate acid were determined by electromotive force measurements of the cell Pt; H2(g, 1 atm), (HOC2H4)2NH2Cl(m1), (HOC2H4)2NH(m2), AgCl(s); Ag in the temperature range 0 to 50 °C. The acidic dissociation constant (K(bh)) of the diethanolammonium ion is given by −log Kbh = 1830.15/ + 4.0302 − 0.0043261 T, 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 ΔCp°, 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 ΔCp° = 49 joule deg(−1)mole(−1).