A new generalized model for predicting the density of single- and mixed-electrolyte solutions

Abstract

A new generalized method is proposed for predicting the density of single- and mixed-electrolyte solutions at 298.15 K from osmotic pressure and ionic radii. In this treatment, the electrolyte solution was modeled as a mixture of ionic hard sphere and compressible water situated in the field of an external pressure, i.e., osmotic pressure. The molar volume of the solution is considered to be the sum of both intrinsic volume of ions and apparent molar volume of water. The former is estimated from the method suggested by Conway et ai. [B.E. Conway, J.E. Desnoyers, C. Smith, Philos. Trans. R. Sec. London, Ser. A 256 (1989) 389-392], and the latter directly from the osmotic pressure. The applicability of the model was tested with 138 single- and 15 binary-electrolyte solutions. The overall average absolute relative deviations (AAD) were found to be 2.38% and 1.13% for the single-electrolyte solutions and 2.80% and 0.96% for the binary-electrolyte solutions when the Pauling radii and the maximum Shannon radii were used for the ionic radii in solutions. On the other hand, in cases where the ionic radii in solutions were treated as the ion-specific parameters that can be applied to all types of salts, the AAD were greatly improved to 0.88% for the 138 single-electrolyte solutions and 0.65% for the 15 binary-electrolyte solutions. (C) 1998 Elsevier Science B.V.