Correlation lengths and density fluctuations in supercritical states of carbon dioxide

Small-angle X-ray scattering intensities from several thermodynamic states of supercritical CO2 were measured. The correlation lengths and density fluctuations of the states obtained by Ornstein-Zernike plots are found to form a ridge along the extension of the coexistence curve of gas and liquid to the supercritical region, corresponding to the critical isochore. The states where these parameters take maxima are shown to be closely related to the solubility of the supercritical fluid and the reactivity of the solute in it.