THE PHYSICAL STATE OF SUPERCRITICAL FLUIDS

The temperature dependencies of intensity in the Raman spectra of a su lfur-saturated aqueous solution show a singular behavior near the crit ical isotherm at isobaric heating or cooling. It has been suggested th at the reason for the singularity is a qualitative change in the physi cal state of a fluid as it turns supercritical. As a probe of the phys ical state of a fluid, a conditional criterion is suggested based on t he analysis of rotational molecular movement in the fluid. In the prac tically significant range of temperatures and pressures a supercritica l water fluid cannot be strictly classified as liquid-like or gas-like . It is a unique transitory state of a substance distinguished by very strong structure fluctuations. (C) 1998 Elsevier Science B.V. All rig hts reserved.