born Sept. 20, 1842, Kincardine-on-Forth, Scot.
died March 27, 1923, London, Eng.
British chemist and physicist.
In 1891 he built a machine for producing liquid oxygen in quantity. His Dewar flask for storing liquefied gases
a double-walled flask has insulating vacuum between the inner and outer walls
became essential in low-temperature scientific work; its principle is used in the Thermos bottle. Dewar was the first to liquefy and solidify hydrogen, and his 1905 discovery that cooled charcoal can help create high vacuums was useful in atomic physics.