James Dewar

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James Dewar

1842-1923

Scottish chemist and physicist known for having invented a double-walled, glass container that keeps hot liquids hot and cold liquids cold. The Dewar flask (or thermos bottle) slows the flow of heat in two ways: maintaining a vacuum between the walls prevents the conduction of heat; mirroring the glass on the vacuum side of the walls slows the radiation of heat. For Dewar, the flask provided a convenient tool for studying cold, liquefied gases. Dewar was the first to liquefy hydrogen and the first to maintain liquid oxygen long enough to discover its magnetic properties.