CHEMISTS PHYSICISTS A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site Dewar, James (1842-1923) Scottish chemist and physicist who invented the first vacuum flask, now named after him, and contributed to the discovery of cordite. Dewar was born at Kincardine and trained both in Britain and continental Europe before becoming a professor at Cambridge. At the same time, he carried out most of his experimental work at the Royal Institution in London. Dewar became interested in turning gases into liquids at low temperatures. In 1898, for example, he succeeded in liquefying hydrogen by cooling and compressing it. In the course of his experiments he found the need for a device to keep liquid air cool and prevent it from boiling away. Since liquid air begins to turn back into gas at about minus 200°C, there was a very considerable problem in storing it. The flask that Dewar devised for the purpose was quite a simple affair. It was merely a double-walled glass vessel. All the air was drawn out of the space between the two walls by a pump, so that any liquid in the flask was surrounded, to all intents and purposes, by a vacuum. The most important ways in which the liquid would normally gain heat – by thermal conduction through the surrounding air – was therefore eliminated. Heat in the form of waves – thermal radiation – is not stopped by a vacuum. Later flasks had their walls silvered to cut down the amount of thermal radiation (see Dewar flask. James Dewar also contributed, together with Frederick Abel (1827-1902), to the development of cordite, a smokeless propellant explosive. He received among other honors, the Rumford Medal of the Royal Society. Related categories    • CHEMISTS    • PHYSICISTS Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP