Electrical conductances of solutions of sodium dodecyl sulfate (SDS) and cetylpyridinium chloride (CPC) in acetamide melt were measured at 89°C as a function of concentration. The dependence of molal conductance of SDS and CPC on concentration has been compared with that of normal electrolytes in acetamide melt. Both SDS and CPC are found to micellize in acetamide melt. A mixed electrolyte model has been used to compute the micellization parameters, viz., critical micelle concentration, aggregation number, and counterion binding constant, from the conductance data. Surface potentials of the micelles were computed by solving the nonlinearized Poisson-Boltzmann equation. The free energy terms for micellization were also evaluated.

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.

No abstract

The specific conductivity of sodium dodecyl sulfate, cetyl pyridinium chloride, and sodium nitrate in acetamide melt was measured at 89°C up to (2.067, 1.599, and 3.705) mol‚kg-1 , respectively. The specific conductivity maximum has been observed for sodium nitrate as well as for the two ionic surfactants. This is the first report on the observation of a specific conductivity maximum for any ionic surfactant, which is otherwise a general feature of a normal electrolyte in aqueous or nonaqueous media. In acetamide melt, the concentrations of sodium dodecyl sulfate and cetyl pyridinium chloride corresponding to their conductivity maxima are found to be less than that of sodium nitrate, which is probably due to micellization of ionic surfactants.

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.