We have made electrochemical measurements with a glass electrode that have yielded pKvalues atT = 298.15 K for monothanolamine (MEA), triethanolamine (TEA), diisopropanolamine (DIPA), and methyldiethanolamine (MDEA) relative to the already well-known pKfor diethanolamine (DEA), with all pKvalues referring to equilibria of the type AmH+(aq) = Am(aq) + H+(aq) in which Am(aq) represents an alkanolamine in aqueous solution and AmH+(aq) represents the corresponding protonated alkanolamine. We have also made calorimetric measurements leading to ΔH0values for dissociation of the protonated species of all five of these alkanolamines in aqueous solution atT = 298.15 K. These pKand ΔH0values have led to ΔG0and ΔS0values for the corresponding dissociation reactions of all five AmH+(aq) species.