Dewar, James (1842–1923)

Scottish chemist and physicist who invented the vacuum flask (Thermos) in 1872 during his research into the properties of matter at extremely low temperatures. He was knighted in 1904.

Working on the liquefaction of gases, Dewar dicsovered, in 1891, that both liquid oxygen and ozone are magnetic. In 1895 he became the first to produce liquid hydrogen, and then in 1899 succeeded in solidifying hydrogen at a temperature of −259°C/−434°F. He also invented, jointly with Frederick Abel, the explosive cordite in 1889.

Dewar was born in Kincardine, Fife, and studied at Edinburgh. He became professor of chemistry at Cambridge 1875, as well as at the Royal Institute in London 1877.

Every gas had now been liquefied and solidified except one – helium. Dutch physicist Heike Kamerlingh Onnes managed to liquefy helium using Dewar's techniques in 1908, and Dewar was then able to achieve temperatures within a degree of absolute zero (−273°C/−459°F) by boiling helium at low pressure.

Dewar also carried out work in spectroscopy, particularly concerned with the absorption spectra of metals. He investigated properties such as chemical reactivity, electrical resistance, strength, and phosphorescence at low temperature. Feathers, for example, were found to be phosphorescent at these temperatures.