Static Relative Permittivities of Water + Propane-1,2-diol and Water + Propane-1,3-diol under Pressures up to 300 MPa at 298.15 K

Static relative permittivities (εr) of water + propane-1,2-diol and water + propane-1,3-diol were measured at four mole fractions under pressures up to 300 MPa at 298.15 K. A Tait-type equation was used to represent εr with pressure (P) for each composition. Values of (∂ ln εr/∂P) T and εr -2(∂εr/∂P) T at 0.1 MPa for both aqueous propanediol systems were determined by use of the static relative permittivity at 0.1 MPa, εr(0.1 MPa), and the Tait-type parameters, A and B. Values of (∂ ln εr/∂P) T and the isothermal compressibility (κ T ) at 0.1 MPa over the entire composition range are compared for both aqueous propanediol systems. A relationship between (∂ ln εr/∂P) T and κ T at 0.1 MPa was derived from the density dependence of εr. Furthermore, composition dependence of εr -2(∂εr/∂P) T at 0.1 MPa was examined for the present systems.