The excess Cibbs energy of liquid mixtures may be predicted using group contribution models (f.ex. UNIFAC and ASOG), or it may be correlated using molecular models such as UNIQUAC. Group contribution models and the UNIQUAC model contain a combinatorial contribution which accounts for size‐ and shape‐effects and a residual contribution which accounts for interactions among groups or molecules. A new expression for the combinatorial contribution is given which yields much improved predictions of the excess Gibbs energy of systems where the residual contribution may be expected to be zero (e.g., mixtures of aliphatic hydrocarbons). It is shown that it is advantageous to incorporate the new combinational expression into future modifications of the UNIFAC model.

Supercritical fluid extraction is a potential technique for the purification of pharmaceutical products containing residual solvents. The solubilities of the drugs in supercritical carbon dioxide are being measured as part of a program in which the potential applications of this technology are being investigated. The solubilities of three inhibitors of inflammatory activity, Ketoprofen, Piroxicam, and Nimesulide, in supercritical CO2, measured using a dynamic saturation technique, are reported at pressures between 100 bar and 220 bar and at two temperatures:  312.5 K and 331.5 K. These chemicals have relatively high solubilities with values ranging from 4 × 10-6 to 15 × 10-4 mole fraction. The solubilities exhibit a clear dependence on the solvent density, and this has been used to provide a simple and precise correlation of the data.

High-pressure partition chromatography, a modification of the inverse gas chromatography technique, is presented as suitable technique for the study of the plasticization effect of carbon dioxide on the following polymers: poly(methyl methacrylate), polystyrene, and bisphenol A-polycarbonate. Polymers in the presence of a compressed gas or a supercritical fluid become plasticized; this means that their glass-transition temperatures (T g 's) can be lowered by 10s of degrees, which causes changes in their mechanical and physical properties. CO 2 -induced plasticization has an important impact on many polymer processing operations in which the T g depressions of the polymers can be evaluated. The experimental results are discussed and compared with data available from literature for each polymer we considered.

The most important effect of sorption of compressed gases and supercritical fluids into glassy polymers is the reduction of the glass transition temperature (T g). This plasticization effect causes changes in mechanical and thermophysical properties of the polymers. In this work, a thermodynamic study based on experimental and theoretical results is addressed. New data were carried out for poly(2,6-dimethylphenylene oxide) (PPO), poly(acrylic acid) (PAA), and the copolymer vinylpyrrolidone−vinyl acetate [P(VP−VA)] using an inverse gas chromatographic technique. To model the T g behavior of diluent−polymer systems, a model that couples the lattice-fluid equation of state and the Gibbs−DiMarzio criterion was used. A parametric study of the influence of the physical properties (lattice coordination number, molecular weight, and binary interaction parameter) on the T g behavior is presented. The thermodynamic model fairly describes the experimental data measured in this work and gives a phenomenological representation of the retrograde vitrification for the systems PPO−CO2, PVP−CO2, and P(VP−VA)−CO2.