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An experimental investigation was carried out on the influence of some hydroxylic additives (up to 30% by weight) on the thermal stability of erythrocyte carbonic anhydrase. The melting temperatures of the protein in the different media were determined by spectroscopic measurements. Xylitol and maltose stabilized the enzyme, whereas ethanol, 1-propanol, ethanediol and 1,2-propanediol caused a destabilization of the protein. In all the systems examined, the transition temperature was found to be strictly related to the surface tension of the medium. A molecular thermodynamic model was developed, based on the chemical equilibrium between the native and denatured protein forms, which enabled to interpret the observed behaviour.

A simple semiflow apparatus was designed for measuring the solubility of gases in liquids under atmospheric pressure. The experimental procedure was tested by performing measurements on some CO2-hydrocarbon systems investigated by other workers. The apparatus was then used for evaluating the solubility of carbon dioxide in cycloparaffins (cyclopentane, cyclohexane, cycloheptane and cyclooctane) at atmospheric pressure and at temperatures ranging from 283 to 303 K. The experimental data were modelled by the Peng-Robinson equation of state. Just one adaptive parameter was used to obtain a good agreement between predicted and experimental results.