Oscillation of the freezing potential of aqueous lithium chloride solutions containing ethanol

Abstract

The freezing potential (E_f) of water–ethanol mixtures containing lithium chloride has been recorded with a temporal resolution of 1 ms. Two sharp peaks (E_f1 and E_f2) and a subsequent maximum (E^m_f) appeared on the E_f-time curves. Addition of 0.001% v/v ethanol caused oscillation of E_f after E^m_f. Further addition of ethanol (0.1–1%) led only to the first peak, E_f1, and subsequent exponential relaxation, followed by the delayed oscillation of the electrical potential after 70 s. The peak positions and their relaxation depended strongly on ethanol content and cooling rate. The positive potential decreased steeply beyond 0.03% ethanol to become negative at 1% ethanol. The LiCl concentrations at which the FP appeared were in the region of 10^–6–0.1 mol dm^–3 LiCl, depending on the ethanol content. The structure of the ice deposited from any solution on a glass plate was of /_h type, with some variation of crystallite size and orientation with ethanol content. A. mechanism for the occurrence of E_f and the effects of ethanol on E_f are discussed.