Freezing of Supercooled Water

Rau has claimed that, by repeated freezing and thawing, the temperature to which a drop of water supercools before freezing can be lowered and, with special care, the freezing temperature can be reduced to -72° C. This is claimed to be the temperature of spontaneous nucleation of ice. At that temperature the ice forms in rectangular crystals which also melt at -72° C. This note describes a careful attempt to repeat Rau's work. Like Cwilong, we have been unable to do so except by deliberate contamination, and it is presumed that Rau's apparatus was faulty and his drops were contaminated by his cooling fluid. Information is given concerning the reproducibility of the freezing temperature of individual drops when repeatedly frozen and thawed. Rau's rectangular crystals have been observed in strong alcohol solutions but no information concerning their nature has been obtained