Solvatochromic Polarity Parameters of Carbon Dioxide in the Sub- and Supercritical State

The Kamlet–Taft solvatochromic polarity parameters are determined for carbon dioxide in sub- and supercritical (SC) states at 22, 40, 60, and 80°C and 10.0–30.0 MPa. The solvatochromic indicators used to determine the parameters are 2,6-diphenyl-4-(2,4,6-triphenyl-1-pyridino)-phenolate (Reichardt’s betaine) and benzophenone for E T and 4-nitrophenol and 4-nitroanisole for b and p, respectively. It is established that the parameters characterizing the polarity and donor–acceptor properties of CO 2 are practically independent of the state parameters, as these properties are governed by the structure of a molecule.