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 (x2=0.43 at 5 °C). 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 x2=0.20 for monoethanolamine+water and x2=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: VE (monoethanolamine+water)