Background
James Dewar was born on September 20, 1842, in Kincardine-on-Forth, Scotland. He was the youngest of six boys of Thomas Dewar, a vintner and innkeeper, and his wife Ann Eadie. His parents died when he was 15.
James Dewar was born on September 20, 1842, in Kincardine-on-Forth, Scotland. He was the youngest of six boys of Thomas Dewar, a vintner and innkeeper, and his wife Ann Eadie. His parents died when he was 15.
Dewar attended Kincardine Parish School and then Dollar Academy. He also learned the art of violin making and later said that this was the foundation for his manipulative skills in the laboratory.
He entered The University of Edinburgh in 1858. James David Forbes, professor of natural philosophy, and Lyon Playfair, professor of chemistry, directed his interest to physical science. Dewar also studied under August Kekulé at Ghent.
Dewar was assistant to Playfair (1867-1868) and to Playfair’s successor, Alexander Crum Brown (1868-1873). He became lecturer on chemistry in the Royal Veterinary College of Edinburgh (1869) and assistant chemist to the Highland and Agricultural Society (1873). He was elected Jacksonian professor of natural experimental philosophy in Cambridge (1875) and Fullerian professor of chemistry at the Royal Institution (1877) and held both chairs until his death. The Royal Institution was the chief center of his experimental activity.
He also served as a consultant to government and industry. He was a member of the government committee on explosives (1888-1891) and with Sir Frederick Abel invented the smokeless propellant cordite, a gelatinized mixture of nitrocellulose in nitroglycerin (1889).
Dewar’s earliest work (1867-1877) encompassed a wide variety of subjects in physics, chemistry, and physiology. In 1867 he invented a mechanical device to represent Crum Brown’s new graphic notation for organic compounds. Playfair sent the device to Kekule, and Kekule invited Dewar to spend the summer in his Ghent laboratory. Dewar suggested seven different structural formulas for benzene, including the diagonal formula and the formula attributed to Kekule.
In 1870 he proposed the pyridine ring formula, substituting a nitrogen atom for a CH residue in the benzene ring. He also suggested that quinoline’s structure consisted of fused benzene and pyridine rings.
Dewar’s early studies included the heats at formation of the oxides of chlorine, the temperature of the sun and of the electric spark, the atomic volume of solids, and the production of high vacua. In 1872 he determined the physical constants of Thomas Graham’s hydrogenium (Graham supposed hydrogen to be the vapor of a volatile metal, “hydrogenium”) and first used a vacuum-jacketed insulating vessel. Interspersed with these physical researches were physiological investigations on the constitution and function of cystine, the physiological action of quinoline and pyridine bases, and the changes in the electrical condition of the eye under the influence of fight.
At Cambridge and the Royal Institution, Dewar continued his varied interests. There were studies on the coaltar bases; atomic and molecular weight determinations; the chemical reactions at the temperature of the electric arc, in which he noted the formation of hydrogen cyanide in the carbon arc burning in air (1879); and the determination of the monatomicity of sodium and potassium vapor from gas density studies (1883).
The first area to be thoroughly explored was spectroscopy. He joined George Downing Liveing, professor of chemistry at Cambridge, in an attempt to correlate line and band spectra with atomic and molecular states. They published seventy-eight papers between 1877 and 1904. Dewar’s interest in spectroscopy stemmed from a fascination with Henri Sainte-Claire Deville’s work on dissociation and reversible interactions and Norman Lockyer’s controversial speculations on the dissociation of the elements at high temperatures. He contrasted Deville’s exact experimental methods with Lockyer’s conjectures, which he felt were based on insufficient evidence. Dewar and Liveing accurately determined the absorption spectra of many elements (especially metallic vapors) and compounds.
They studied the general conditions affecting the excitation of spectra and, in particular, the ultraviolet emission spectra of many metals. They noted the contrast between single spectral lines, multiplets, and bands, and they attempted to identify the emitting agents for single, multiplet, and band spectra. They classified great, intermediate, and weak intensities with the spectroscopic series as principal, diffuse, and sharp, respectively. Their studies included the differences between the arc, spark, and flame spectra of metals; the emission spectra of gaseous explosions and of the rare gases; and the effect of temperature and concentration on the absorption spectra of rare-earth salts in solution.
Dewar’s coming to the Royal Institution in 1877 marked the beginning of his work in cryogenics, his major field of study. In that year Louis Cailletet and Raoul Pictet liquefied small amounts of oxygen and nitrogen. This achievement interested Dewar because hitherto almost all the work on liquefaction of gases had been done at the Royal Institution, especially by Michael Faraday, who by 1845 had liquefied all the known gases except the six permanent ones (oxygen, nitrogen, hydrogen, nitric oxide, carbon monoxide, and methane). During a Royal Institution lecture in 1878 Dewar gave the first demonstration in Great Britain of the liquefaction of oxygen. His principal interest was not the liquefaction of gases but the investigation of the properties of matter in the hitherto uninvestigated vicinity of the absolute zero of temperature.
Dewar’s study of the properties of matter at very low temperatures was made possible by his invention in 1892 of the vacuum-jacketed flask, the most important device for preserving and handling materials at low temperatures. The insulating property of the vacuum was well known, and Dewar had used a vacuum flask in 1872 in making specific heat determinations of Graham’s hydrogenium. When he wanted to investigate the properties of liquefied gases, the idea of using a vacuum-jacketed vessel suggested itself to him.
Dewar examined a wide range of properties in pioneering explorations on the effect of extreme cold on substances. He determined the properties of all the liquefied gases. He measured the decreased chemical reactivity of substances at low temperatures. He studied the effects of extreme cold on phosphorescence, color, strength of materials, the behavior of metal carbonyl compounds, the emanations of radium (with William Crookes), and the gases occluded by radium (with Pierre Curie).
Dewar intended to explore the whole field of cryogenics. Between 1892 and 1895 he joined with John A. Fleming, professor of electrical engineering at University College, London, in an investigation of the electrical and magnetic properties of metals and alloys. They gathered accurate information on conduction, thermoelectricity, magnetic permeability, and dielectric constants of metals and alloys from 200°C to -200°C.
Another area of extensive investigation was low-temperature calorimetry (1904-1913). Dewar devised a calorimeter to measure specific and latent heats at low temperatures. He determined the atomic heats of the elements and the molecular heats of compounds between 80°K and 20°K. He discovered in 1913 that the atomic heats of the solid elements at a mean temperature of 50° K were a periodic function of the atomic weights.
World War I prohibited continuation of Dewar’s costly cryogenic research. He turned to thin films and bubbles, which had been the subject of the first of his nine courses of Christmas lectures for children at the Royal Institution (1878-1879). He studied both solid films, produced by the evaporation of the solvent from amyl acetate solutions of nitrated cotton, and liquid films from soap. He investigated the conditions for the production of long-lived bubbles and of flat films of great size, the distortions in films produced by sound, and the patterns formed by the impact of an air jet on films.
At the time of his death Dewar was engaged in studies with a delicate charcoal-gas thermoscope that he constructed in order to measure infrared radiation. From a skylight in the Royal Institution he measured the radiation from the sky by day and night and under varying weather conditions.
James Dewar is remembered as a distinguished chemist and physicist who invented the first vacuum flask (1892), now named after him, pioneered techniques in low-temperature physics, and contributed to the discovery of cordite. He also proposed various structures (including the "Dewar structures") for benzene.
In 1899 he became the first recipient of the Hodgkins gold medal Of the Smithsonian Institution, Washington.
In 1904 he was the first British subject to receive the Lavoisier medal of the French Academy of Sciences, and in 1906 he was the first to be awarded the Matteucci medal of the Italian Society of Sciences.
He was knighted in 1904, and in 1908 he was awarded the Albert medal of the Society of Arts.
A street within the Kings Buildings complex of the University of Edinburgh was named in memory of Dewar in the early 21st century.
Dewar was president of the Society of Chemical Industry (1887), the Chemical Society of London (1897-1899), and the British Association (1902).
Dewar was a superb experimentalist; he published no theoretical papers.
Dewar's career saw him involved in a number of public quarrels with fellow scientists; he was a fierce and sometimes unscrupulous defender of his rights and his claims to priority in a way that throws much light on the scientific spirit and practice of his day.
Physical Characteristics: Dewar was crippled by rheumatic fever at the age of ten.
In 1871 Dewar married Helen Rose Banks, daughter of an Edinburgh printer; they had no children.
