Inventor and pioneer of cryogenics. Dewar was born in Kincardine (Fife) and educated at the University of Edinburgh. He was appointed Professor of Natural Philosophy at Cambridge (1875) and, two years afterwards, Fullerian Professor of Chemistry at the Royal Institution, later becoming the Director of their Davy-Faraday Research Laboratory.
His main contribution was in low-temperature work. Most famously he invented the vacuum flask, or Dewar flask (1892), which he built to maintain liquids at low temperatures, but is equally effective at keeping liquids hot. He was also involved in the invention of the explosive cordite (1889), used widely today as the propellant in bullets. He built a machine for producing liquid oxygen (1891), was the first to produce liquid hydrogen (1898) and solidify it (1899). Dewar was also the first to demonstrate that metals conduct electricity better at very low temperatures, a discovery which led eventually to the use of superconductors in the computing industry.
Dewar was knighted in 1904 and died in London.