James Dewar Biography

World of Chemistry on James Dewar

James Dewar was born in Kincardine, Fife, Scotland, on September 20, 1842. He attended the University of Edinburgh and developed a wide range of interests, including electricity, chemistry, spectroscopy, and the measurement of high temperature. He was served as professor at both Cambridge University and the Royal Institution in London, England.

In 1874, Dewar published two papers: The Latent Heat of Liquid Gases and A New Method of Obtaining a Very Perfect Vacua. He had discovered that when charcoal was cooled it became extremely efficient at absorbing molecules. That meant that after a vacuum had been created with an air pump, charcoal could be used to absorb any remaining molecules, creating a better vacuum. This improved vacuum would come in very handy for Dewar in the future.

With George D. Liveing, Cambridge professor of chemistry, Dewar published 78 papers on spectroscopy between 1877-1904. They discovered the absorption spectrum of many elements and compounds. By comparing the spectra of known objects with that of the stars, it was possible to identify the elements in the stars.

Dewar became interested in the nature of materials at extremely low temperatures after Louis Paul Cailletet and Raoul Pictet had created small amounts of oxygen and nitrogen in nearly liquid form in 1877. They had been able to attain a temperature of eighty degrees above absolute zero.

Dewar, however, was more concerned with studying the characteristics of liquified gasses. He built a cooling device and, in 1885, became the first person to produce a quantity of liquid oxygen which, he later discovered, was influenced by a magnet. He eventually reached a temperature of 14° above absolute zero, becoming the first person to create solid oxygen and hydrogen.

The biggest impediment to Dewar's work was in keeping the gases cold enough to remain liquid. To better insulate the gases, he created a double-walled flask in 1872 that kept liquids cold by keeping out the warm surrounding air. Unfortunately, Dewar did not patent the idea and the Dewar flask was eventually adapted for use as an insulated beverage container better known as a Thermos ^TM brand bottle.

Dewar and his colleague Frederick Abel (1827-1902) did patent their discovery of cordite, a form of smokeless gunpowder. This discovery had come about following long discussions with Alfred Nobel, who sued them and lost.

Intending to explore the entire field of cryogenics , Dewar joined forces with John A. Fleming, professor of electrical engineering at London's University College, who would later invent the vacuum tube. They studied the electrical and magnetic properties of metals and alloys at low temperatures. They discovered that as temperature dropped, electrical resistance dropped as well. At absolute zero resistance would vanish completely. This paved the way for the science of superconductivity. Creating a calorimeter to measure specific and latent heat at low temperatures in 1913, Dewar determined the atomic heats of elements and molecular heats of compounds.

Dewar was knighted in 1904. While many of his discoveries came about through the collaboration of colleagues, Dewar did not work well in a team situation; he could be brusque and individualistic at times. He was indifferent as a teacher, but excellent as a public lecturer. At the time of his death, on March 27, 1923, the 80-year-old was still experimenting, using a charcoal-gas thermoscope to measure infrared radiation from the sky.