Volumetric properties of some water+monoalkanolamine systems between 303.15 and 323.15K
Abstract Density (ρ) of aqueous solutions of monomethylethanolamine (MEA), monoethylethanolamine (EEA), dimethylethanolamine (DMEA), dimethylpropan-1-olamine (DMPA-1) and dimethylpropan-2-olamine (DMPA-2) is measured at a 5 K interval between 303.15 and 323.15 K in the range of 0 ≤ x2 ≤ 1, where x2 is the mole fraction of alkanolamines. The ρ of the monoalkanolamines is assumed to be related to respective strength of association. Excess molar volumes ( V m E ) were negative for all systems in the whole range of composition and at all temperatures with minima occurring at x2 ~ 0.35 to 0.40. The depth of minima varied as, W + DMPA-2 > W + DMEA > W + DMPA-1 > W + EEA > W + MEA. Negative V m E were explained by large size difference as well as hydrophobicity effects. Thermal expansivity (α) followed as, W + DMPA-2 > W + DMEA > W + DMPA-1 > W + EEA > W + MEA, while its excess values were found to form distinct minima. The ρ vs. x2 isotherms have been correlated with polynomials, while V m E and αE were fitted to the Redlich–Kister equation. In addition to intermolecular H-bonding, interstitial accommodation, steric effects etc. ‘hydrophobicity’ of the alkanolamines is suggested to play the most vital role for the systems under investigation.