ELECTRICAL CONDUCTANCE AND VISCOSITY OF CONCENTRATED H2SO4 H2O BINARY-SYSTEMS AT LOW-TEMPERATURES - CORRELATION WITH PHASE-TRANSITIONS/

Density, viscosity, and electrical conductance of concentrated H2SO4/H 2O systems (above 66 wt% H2SO4) were measured in the subambient temper ature 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 po wer-law equation, the latter being a better functional form to describ e the temperature dependence of transport properties. Concentration de pendences of viscosity, conductance, expansivity, and ideal glass tran sition temperature indicate the occurrence of structural changes in th e H2SO4/H2O system in the regions 83-85 and 92-94 wt % H2SO4 which are attributed to the formations of H2SO4 H2O (at 84.48 wt% H2SO4) and th e eutectic between H2SO4 . H2O and H2O (at 93.8 wt % H2SO4), respectiv ely. Above similar to 75 wt % H2SO4 a direct correlation exists betwee n the viscosity-concentration curve and the phase diagram of the H2SO4 /H2O system.