Comment on “correlation length and density fluctuations in supercritical states of carbon dioxide”

The interpretation of recent small-angle X-ray scattering experiments by Nishikawa et al. which indicates a λ-shaped singularity in the compressibility is critically examined based on the general scaling theory near the liquid-gas critical point. On general grounds our arguments support the results by Gray et al. [Chem Phys. Lett., 271 (1997) 185] which contradicts the interpretation by Nishikawa et al. [Chem. Phys. Lett., 244 (1995) 149; J. Phys. Chem., 100 (1996) 418].