PARTITION-COEFFICIENTS OF ORGANIC-SUBSTANCES IN 2-PHASE MIXTURES OF WATER AND CARBON-DIOXIDE AT PRESSURES OF 8 TO 30 MPA AND TEMPERATURES OF 313 TO 333 K

A new apparatus is described for easy and quick determination of parti tion coefficients in a system containing an aqueous and a supercritica l phase, and an organic substance, The partition coefficient in this c ase is defined as the ratio of molar fractions of a substance in two d ifferent phases in equilibrium. The apparatus consists of a high-press ure cell of 200-mL volume. Equilibrium is attained by recirculation of the fluid phases. Samples can be taken from either phase by using six -way sampling valves, Quantitative analysis is carried out either by U V-spectroscopy or by gas chromatography. In the measurements, carbon d ioxide was used as the supercritical fluid. in studies of partitioning behavior of the organic compounds, phenol, benzoic acid, benzyl alcoh ol, 2-hexanone, vanillin, and caffeine. The experiments were carried o ut at temperatures ranging from 313 to 333 K and pressure of 8 to 30 M Pa. Partition coefficients between 0.2 and 1.5 were found for phenol w hich roughly match the data previously reported by other authors. Part ition coefficients of benzyl alcohol and benzoic acid were found to be in a similar range, whereas tl-lose of 2-hexanone turned out to be be tween 10 and 140. The partition coefficients obtained ranged from 0.02 to 0.25 for caffeine and 0.2 to 3 for vanillin.