Densities and excess molar volumes of aqueous solutions of some diethanolamines

Densities of aqueous diethanolamine (DEA), methyldiethanolamine (MDEA), ethyldiethanolamine (EDEA) and n-butyldiethanolamine (BDEA) solutions were determined from 303.15 to 323.15K at different compositions in the range 0 <= x(1) <= 1, where x(1) is the mole fraction of alkanolamines. The densities of the diethanolamines are assumed to be related to the strength of association. Excess molar volumes have been calculated from the density data. The V-m(E) values have been found to be negative for all systems in the whole range of composition at all temperatures, and less negative with increasing temperature. Negative values of V-m(E) can be explained by the large difference in the molar volumes. For all systems, minima occur at about 0.35-0.40 mole fraction of diethanolamines. The depth of minima varies as EDEA+W > MDEA+W > BDEA+W > DEA+W. All the data have been correlated with six-degree polynomial equations.