Volumetric properties of aqueous solutions of monoethanolamine, mono- and dimethylethanolamines at temperatures from 5 to 80 °C I

Densities of aqueous binary mixtures of monoethanolamine, monomethylethanolamine and dimethylethanolamine were measured over the whole range of compositions at temperatures varying from 5 to 80 C The density of monoethanolamine + water mixtures shows a maximum (x(2) = 0.43 at 5 degreesC). The density behavior of monoethanolamine + water and dimethylethanolamine + water mixtures is different from the monoethanolamine + water system. The composition dependence of the densities of these two mixtures was classified in two distinct zones. This separation line occurs at x(2) = 0.20 for monoethanolamine + water and x(2) = 0.12 for the dimethylethanolamine + water system. In the low concentration zone, the density values exhibit a minimum and a maximum at increasing ethanolamine concentration, while in the high concentration zone, the density values approach the density of the pure alkanolamine in a monotonic fashion. The excess molar volume of these mixtures is dependent on the structure of the ethanolamines: V-E (monoethanolamine + water) < V-E (monoethanolamine + water) < V-E (dimethylethanolamine + water). (C) 2002 Elsevier Science B.V. All rights reserved.