Volumetric properties of hexamethyleneimine and of its mixtures with water

Densities of pure hexamethyleneimine and of its aqueous solutions have been measured at atmospheric pressure, using an Anton Paar digital vibrating tube densimeter, from 273.16 to 363.15 K and from 283.15 to 353.15 K, respectively. Acceptable representations of experimental data are found using a general correlation from Dauber et al. for pure hexamethyleneimine and using a general correlation from Bettin and Spieweck for pure water; thus indicating consistency of newly measured data. In this paper, we show the Redlich–Kister equation leads to incorrect data treatment particularly at low concentrations for systems presenting hydrophobic interactions. Thermal expansion coefficients (α*) for the pure hexamethyleneimine (HMI) and excess thermal expansion coefficient (αE) of the binary mixture: HMI + water at 283.15 and 298.15 K over the whole mole fraction range of water are presented and discussed in terms of the structural changes in the mixtures.