Determination of water activities, osmotic and activity coefficients of the system NH 4NO 3–LiNO 3–H 2O at the temperature 298.15 K

Abstract

The water activities of the mixed aqueous electrolyte {( y) NH 4NO 3+(1− y) LiNO 3)}(aq) are measured at total molalities from 0.2 mol kg −1 to about saturation for different ionic-strength fractions y of NH 4NO 3 with y = 0.20 , 0.50 , 0.80 . The results allow the deduction of osmotic coefficients. The experimental results are compared with the predictions of the Zdanovskii–Stokes–Robinson (ZSR), Robinson and Stokes (RS), Lietzke and Stoughton (LS II), Reilly–Wood–Robinson (RWR) mixing rules and the Pitzer model. From these measurements, the Pitzer mixing ionic parameters are determined and used to predict the solute activity coefficients in the mixture. The excess Gibbs energy is also determined.