Dielectric constants (epsilon), densities (rho), and refractive indices (n(D)) were measured for binary blend of tetramethylensulfone (TMS) or sulfolane and N-methyldiethanolamine (MDEA) at temperatures ranging from 293.15 to 328.15 K and atmospheric pressure over the whole mole fraction range. From these experimental data, the excess molar volume (V-m(E)), and deviations in refractive indices (Delta n(D)), and relative permittivities (Delta epsilon), were calculated. These quantities were fitted to the Redlich-Kister polynomial equation to derive the binary adjustable parameters and standard errors. The effective dipole moment of pure liquid was calculated by using of Kirkwood-Frohlich equation. (C) 2012 Elsevier B.V. All rights reserved.