Freezing point depression in the binary NaVO3–H2O and NH4VO3–H2O Systems at p=0.1MPa

Abstract

The freezing point depressions in the

and

systems have been determined at $p=0.1MPa$ from molalities of ca. $0.005{molkg}^{-1}$ up to near saturation. The present data significantly expand the almost non-existent database of excess thermodynamic properties of binary

systems. The data could be explained within their experimental uncertainties by a thermodynamic model considering the association of the dihydrogenvanadate ion (

) to

and representing the excess Gibbs free energy ($G^{\mathrm{Ex}}$) by the Pitzer equations with two adjustable parameters. The magnitudes of the determined parameters for the second virial coefficient of

-

interaction were typical for 4-1 electrolytes. The same model could describe also the data for the

system as even the saturated solution is sufficiently dilute that the contribution of short range interactions to $G^{\mathrm{Ex}}$ is small.