title: Viscosity measurements of water at high temperatures and pressures using dynamic light scattering.
abstract: The application of dynamic light scattering to measure viscosity of water at high temperatures and pressures is demonstrated. Viscosity was obtained from the translational diffusion coefficient of probe particles dispersed in the medium by the Einstein-Stokes relationship. Measurements were carried out with polystyrene latex, colloidal silica, and colloidal gold. Under a constant pressure of 25 MPa, good agreement was found between the measured and calculated viscosities up to 275 degrees C with the polystyrene latex, 200 degrees C with the colloidal silica, and 297 degrees C with the colloidal gold. It was found that failure of the measurements at high temperatures is ascribed to change in either the dispersion stability or chemical stability of the probe particles. The present results indicate that the technique could also be used for other supercritical fluids having high critical temperature and pressure, such as methanol (T(c) = 239.4 degrees C, P(c) = 8.1 MPa) and ethanol (T(c) = 243.1 degrees C, P(c) = 6.4 MPa).
authors.affiliation: Extremobiosphere Research Center, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka 237-0061, Japan. shigeru.deguchi@jamstec.go.jp
authors.forename: Shigeru
authors.initials: S
authors.lastname: Deguchi
authors.forename: Swapan K
authors.initials: SK
authors.lastname: Ghosh
authors.forename: Rossitza G
authors.initials: RG
authors.lastname: Alargova
authors.forename: Kaoru
authors.initials: K
authors.lastname: Tsujii
mesh_terms: D002627:Chemistry, Physical / Q000379:methods*; D003102:Colloids / Q000737:chemistry; D004058:Diffusion; D006046:Gold; D006358:Hot Temperature; D007840:Latex / Q000737:chemistry; D008027:Light; D011137:Polystyrenes / Q000737:chemistry; D011312:Pressure; D012542:Scattering, Radiation; D013696:Temperature; D013816:Thermodynamics; D014783:Viscosity; D014867:Water / Q000737:chemistry*
chemical_list: D003102:Colloids; D007840:Latex; D011137:Polystyrenes; D014867:Water; D006046:Gold