The ternary solubilities of solid isomers of nitrobenzoic acid (NBA) were experimentally determined at 308, 318 and 328 K over a pressure range of 12-18 MPa in supercritical carbon dioxide (SCCO 2). Compared to its binary solubility, the ternary solubilities of m-NBA increased at 308 K while it decreased at 328 K. However, the ternary solubilities of p-NBA increased at all temperatures and pressures except at 13 MPa and 328 K. A new model was developed by applying solution model and activity coefficient model for the ternary solubilities of pharmaceutical and non-pharmaceutical solid mixtures in terms of temperature, density and cosolute composition. The model equation involves four temperature independent constraint-free parameters. The model equation correlates the ternary solubilities of seven pharmaceutical solid mixtures along with current data with an average AARD around 9.5% and sixteen non-pharmaceutical solid mixtures with 9% AARD. © 2012 Elsevier B.V.