Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

Apparent molar volumes /V and viscosity B-coefficients for caffeine in (0.00, 0.03, 0.05, and 0.07) mol dm 3 aqueous thorium nitrate, Th(NO3)4, solutions were determined from solution density and viscosity measurements over the temperature range (298.15 to 318.15) K as function of concentration of caffeine and the relation: phiV = a0 + a1T + a2T2, have been used to describe the temperature dependence of the standard partial molar volumes phiV . These results have been used to deduce the standard volumes of transfer delta phiV and viscosity B-coefficients of transfer deltaB for caffeine from water to aqueous Th(NO3)4 solutions for rationalizing various interactions in the ternary solutions. The structuremaking or breaking ability of caffeine has been discussed in terms of the sign of the second temperature derivative of phiV. The Friedman-Krishnan co-sphere model was used to explain the transfer volume of caffeine with increasing Th(NO3)4 molarity. The activation parameters of viscous flow for the ternary solutions were also discussed in terms of transition state theory.