Computation of Equilibrium Partial Vapor Pressures of Aqueous Ammonia Solutions

This report evaluates all available vapor-liquid equilibria VLE data from low-to-moderate pressures over the normal liquid water temperature range for the highly non-ideal aqueous ammonia solutions spanning nearly a century. The evaluation relies on all complete VLE data comprised of pressure-temperature-liquid and vapor compositions published over the last century to develop a temperature dependent model for the coefficients of the Wilson equation. The computations derived from the temperature dependent model are described by means of the program flowcharts and listings. Graphs of computed minima of the best Wilson coefficient pairs illustrate the statistical analysis of the experimental data. Tables of calculated deviations for three sets of Wilson coefficients corresponding to the individual and combined data sets demonstrate the utility of the model equations. Excellent agreement between the experimental and calculated liquid and vapor compositions is found for all but two data sets over the region of rapidly changing vapor composition up to 90 mole of ammonia. This temperature dependent Wilson model offers a succinct representation of 100 years of what appear to be disparate pressure- temperature-composition VLE data.