Pyridinium N-phenoxide betaines and their application to the characterization of solvent polarities. Part 23. Determination of ET (30) values of supercritical carbon dioxide at various pressures and temperatures

By using the neg. solvatochromic betaine dyes I (R = H, CMe3) the UV/VIS-spectroscopically derived empirical solvent polarity parameter ET(30) for supercrit. CO2 was detd. in the temp. and pressure ranges 40-80.degree. and 150-550 bar, resp.