Osmotic and Activity Coefficients of Lithium Nitrate in Ethanol Under High Pressures

The pressure dependences of the osmotic and activity coefficients of lithium nitrate (LiNO 3 ) in ethanol at 298.15 K up to 40 MPa and 3.0 mol·kg −1 have been estimated from literature volumetric data on LiNO 3 solutions in ethanol using the Pitzer ion-interaction or virial coefficient approach. In particular, the volumetric Pitzer ion-interaction parameters ( β MX 0 V , β MX 1 V , and C MX V ) have been evaluated from a mathematical fit of literature apparent molar volume data to the appropriate Pitzer equation. These were then expressed as polynomials in pressure, which were used to calculate the change in the osmotic and activity coefficients in going from an initial pressure of p 1 to a final pressure of p 2 . These pressure dependences have subsequently been coupled with the osmotic and activity coefficient values of ethanolic LiNO 3 solutions at atmospheric pressure obtained from the literature to yield a comprehensive set of osmotic and activity coefficients for LiNO 3 solutions in ethanol at 298.15 K, pressures of 5, 10, 15, 20, 25, 30, 35, and 40 MPa, and molalities to 3.0 mol·kg −1 . The approximation as to the pressure dependence of the dielectric constant of ethanol estimated using the isothermal compressibilities has been tested for pressures above 0.1 MPa. The results demonstrate that this approximation becomes poorer with the increase in pressure as far as ethanol is concerned.