Electrical Conductivity Measurements of Some Supercooled Aqueous electrolyte solutions

Abstract

The properties of supercooled water and supercooled aqueous solutions are reviewed. The mechanism of proton mobility in water is reviewed and Halle and Karlström’s model for the mechanism of proton mobility in water is described in detail. A continuous flow capillary conductivity cell is developed for measuring the conductivity in corrosive solutions such as the one studied in this project, namely, aqueous KOH (of concentrations 0.8734 M, 0.0875 M, 0.00853 M and 0.00175 M). Pyrex and quartz capillaries are used in order to determine which type gives the most reproducible resistivity results. With both the standard capillary conductivity cell and the continuous flow capillary conductivity cell, the quartz capillaries are found to produce the most reproducible resistivity results. The KOH conductivity values (spanning a temperature range of 45 to -25 °C) fit a power law (or critical) type of equation as has been found for the conductivity in various other aqueous electrolyte solutions by previous workers. However, the hydroxide ion mobility was not found to exhibit a simple linear temperature dependence (i.e. with the exponent in the critical equation being unity) as has been observed for the mobility of the proton by previous workers. Possible reasons for this difference are discussed with reference to Halle and Karlström’s model for the mechanism of proton mobility. The electrical conductivity of aqueous CsI solutions (1 M, 0.1 M and 0.01 M) are measured in to the supercooled region. These conductivity values also fit a critical equation. The CsI conductivity data has strongly indicated that there could be a violation of the Onsager limiting law in the supercooled region. As expected, it is found that the cross point, beyond which the conductivity increases with concentration, occurs at a higher temperature for CsI than for KCl due to the greater depression of Ts in aqueous CsI solutions than in aqueous KCl solutions.