A new physical property model for the calculation of the density of solutions of aqueous electrolytes has been developed for the ASPEN process simulator as part of the simulation of the Great Plains Coal Gasification Plant. The model developed recently by Jay S. Dweck, Consultant, Inc. is an extension of the Debye-Huckel limiting law. The Debye-Huckel limiting law allows the predictions of the density of dilute solutions of dissolved salts by providing a relationship for the molar volume of the salt as a function of ion strength. The relationship is linear in the square root of ionic strength, with the slope dependent only upon the charges of the ions which constitute the salt. When combined with data for the infinite dilution molar volume of the salts, solution density can be calculated. The new model preserves the linear relationship with the square root of ionic strength, but introduces ion dependent parameters for the determination of the slope. The solution density is calculated in terms of the molar volumes of the individual ions, instead of a mixture of pseudo salts. Preliminary tests of the model have shown it to be far more accurate than the original limiting law, and applicable to more concentrated solutions (greater than 10 molar).