The Deeper Freeze

If teacher says flatly that fresh water always freezes at 32DEG F. under normal atmospheric pressure, she is wrong. Before it can turn to ice, water needs nuclei--minute particles, usually of some other substance, e.g., dust. Last week, General Electric Research Laboratory announced that its scientists had succeeded in supercooling water to 39DEG below zero--71DEG lower than its normal freezing point. At that temperature, nuclei seemed to form spontaneously and the supercooled water finally became ice.

Metals act the same way. Mercury thermometers are of little use in Arctic winters because they freeze at 37.7DEG below zero. G.E. researchers kept mercury, free of foreign nuclei, in a liquid state down to an unearthly 109.7DEG below. Tin, which normally "freezes" in a hot oven at 449.4DEG, was kept molten down to 251DEG.

Nature long ago beat G.E. to the trick. Clouds often contain water which is below the freezing point, unfrozen because of the lack of nuclei. G.E. was trying to learn more about controlling the weather (supplying nuclei to turn such clouds into snow) when it made its discovery.

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