Densities and partial molar volumes of supercooled aqueous solutions

Density measurements of aqueous solutions of ethanol, t-butanol, and hydrazine in the temperature range from 50 °C down to nucleation are presented. From these data, solute partial molar volumes and temperatures of maximum density are determined. The partial molar volumes of the alcohol solutions at low concentration become small below −30 °C, and the characteristic minimum in the partial molar volume vs concentration curve vanishes. The hydrazine solutions display similar behavior except no minimum is observed. It is also found that the temperature of maximum density washes out at finite concentrations and solutions with higher concentration do not seem to nucleate but may be forming glasses. These results are discussed in terms of a liquid clathrate structural model of water which becomes multiply connected to fill all space as the water is supercooled.