Density, viscosity, and electrical conductance of concentrated H 2 SO 4 /H 2 O systems (above 66 wt % H 2 SO 4) were measured in the subambient temperature region. The lowest temperature of measurement was 198 K. Density varied linearly with temperature. Viscosity and conductance data were fitted to the Vogel-Tammann-Fulcher (VTF) equation and also to the power-law equation, the latter being a better functional form to describe the temperature dependence of transport properties. Concentration dependences of viscosity, conductance, expansivity, and ideal glass transition temperature indicate the occurrence of structural changes in the H 2-SO 4 /H 2 O system in the regions 83-85 and 92-94 wt % H 2 SO 4 which are attributed to the formations of H 2 SO 4 ‚H 2 O (at 84.48 wt% H 2 SO 4) and the eutectic between H 2 SO 4 ‚H 2 O and H 2 O (at 93.8 wt % H 2 SO 4), respectively. Above ∼75 wt % H 2 SO 4 a direct correlation exists between the viscosity-concentration curve and the phase diagram of the H 2 SO 4 /H 2 O system.

Electrical Conductance and Viscosity of Concentrated H2SO4/H2O Binary Systems at Low Temperatures: Correlation with Phase Transitions.-The temp. and concentration dependence of the density, electrical conductivity, and viscosity of concentrated H2SO4/H2O systems containing above 66 wt.% H2SO4 are determined in the subambient temp. region. The temp. dependence of the transport properties can be adequately described by the power-law equation. Structural changes in the H2-SO4/H2O system observed around 83-85 and 92-94 wt.% H2SO4 corresponds to formation of H2SO4·H2O (at 84.48 wt.% H2SO4) and the eutectic between H2SO4·H2O and H2SO4 (at 93.8 wt.% H2SO4), respectively. A direct correlation between the viscosity-concentration curve and the phase diagram of the H2SO4/H2O system exists above . apprxeq.75 wt% H2SO4. -(DAS, A.; DEV, S.; SHANG-PLIANG, H.; NONGLAIT, K. L.; ISMAIL, K.; J.