Sir James Dewar, F. R,. S

107 February 4, 1911 SCIENTIFICAME RICAN

Famous for His Researches In Low Temperature Phenomena

By P. F. Mottelay

IR JAMES DEWAR was born at Kincardine-on known that without these peculiar vessels (called losing the entire two years' accumulation through tlw S Forth, Scotland, on the 20th of September, 1842, Dewar flasks by the scientific world) the crowning collapse of the glass vacuum vessel containing tlw received his education at Dollar Academy and Edin achievement of obtaining hydrogen in the liquid state regenerator coil, he had to begin all his experiments burgh University, and when twenty-nine years of age would scarcely have been possible. anew. Notwithstanding this, his researches, though as was married to Helen Rose, daughter of William In his presidential address to the British Associa yet necessarily incomplete, were such as to justify him Banks, Edinburgh. tion at Belfast in 1902, Prof. Dewar makes the follow in predicting the probable properties of liquid helium. He had in 1863 been appointed assistant to Sir Lyon ing reference to the liquefaction of hydrogen, next to Of these, the most important was that the liquid den· Playfair, then professor of chemistry at Edinburgh helium, the most elusive of all gases: "Compared with sity would be found about 0.14, or at least twice that University, from whom he received the principal part an equal volume of liquid air, it requires only one of liquid hydrogen. Since then this prediction has of his chemical training, and in 1868 spent the sum fifth the quantity of heat for vaporization; on the been closely verified by Prof. Kamerlingh Onnes of mer term at the University of Ghent under the cele other hand, its specific heat is ten times that of liquid Leyden, who has found 0.15 as the experimental value. brated professor Friedrich August Kekulii, continuing air or five times that of water. _ It is by far Sir William Ramsay and Mr. M. W. Travers had a research started at Edinburgh on the oxidation of the lightest liquid known, its density being only one· inferred with less truth that the liquid density of the coal-tar bases, from which originated the Dewar quarter that of water. It is by far the coldest helium would be 0.43. The critical pressure and gen Korner theory of the pyridine ring. He is the author liquid known. Reduction of the pressure by eral order of constants were what Sir James Dewar of numerous papers covering an unusually wide range an air pump brings down the' temperature to minus suggested, the boiling point being 4 deg. absolute, of chemical and physical subjects, and is now entitled, 258 deg., when the liquid becomes a solid resembling and the critical point not more than 5 deg. on the among other claims, to the distinction of being the frozen foam, and this by further exhaustion is cooled absolute scale. The results of direct obs0rvations recognized world authority on the constitution of the to minus 260 deg., or 13 deg. absolute, which is the made by Prof. Onnes were: Boiling point, 41h deg.; atmosphere. In 1875 he was appointed ,:racksonian lowest steady temperature that has ever been reached. critical temperature, 5lh deg. C. absolute; critical Professor of Natural Experimental Philosophy in the At this nadir of temperature, air becomes a rigid pressure, 2lh atmospheres. University of Cambridge, and he has occupied since inert solid. Such cold involves the solidification of One of Dewar's most important discoveries in 1877 the highly coveted other fields was that of post of Fullerian Profes cordite, made in conjunc sor of Chemistry in the tion with Sir Frederick Royal Institution. He has Abel, who also aided him besides been lecturer on in developing other ex· chemistry at the D i c k plosives accepted by the Veterinary College, chemist English government for to the Highland and Agri military purposes. Mention cultural Society, as well should be made of the fact as examiner in the univer that he was first to study sities of Edinburgh and the very important oxida· London, and is at present tion products of the quin· director of the Davy oline bases, and that much Faraday Research Labor of his attention has like· atory. wise been given to the in· The field of work with teresting study of phos which Dewar's name is phorescence. perhaps more c los ely In t h.e accompanying linked than any other is photograph Sir Jam e s that of low temperature Dewar is shown holding in research. During the year his hands a bulb of the 1891; on the occasion of type associated with his the celebration of the cen name. He is of middle tenary of Faraday's birth, height and well built. His he proved among 0 ther strong, clear·cut, rElfined facts, in a singularly in features and deep-set eyes teresting lecture at the give him an impressive Royal Institution, t hat appearance. "Whether se€'n oxygen, which is known at the experimental table, to be but feebly magnetic on the speaker's platform, at ordinary temperatures, or in his magnificent quar· becomes highly susceptible ters at the Royal Institu· to magnetism when sub tion, the impression he jected to minus 180 deg. conveys is one of great C. He had previously lec earnestness, happily com t u red notably on the bining the thoughtfulness "Liquefaction of Oxygen," of the born scientist with on the "Chemical Actions the dignity and refinement of Liquid Oxygen," and on attaching to his promi the "Production of Oxy nent associations and very gen in the Solid State," attractive home surround and these papers w ere ing s. A strongly indi- rapidly followed by others, vidual stamp is given to among which should be singled out those on the every gaseous substance but one (helium) that is at these latter by a wealth of the very rarest pictures, "Spectrum of Liquid Oxygen," on "Liquid Atmos present known to the chemist. . As we ap engravings, Benvenuto carvings, tapestries, scarce pheric Air," on '"Liquid Nitrogen," on the "Electrical proach the zero po.int of absolute temperature, we books bound in the most sumptuous fashion, etc., Resistance and Thermo-Electric Powers of Pure seem to be nearing what I can only call the death of which he and Lady Dewar have collected in the

Metals, Alloys, and Non-Metals at the Boiling Point matter. _ Its existence has long been indicated course of their travels. of Oxygen and of Liquid Air," on "Electric and by the regularly diminishing volumes of gases and the Sir James Dewar's de'livery in public is most excel Magnetic Researches at Low Temperatures," and on gradual falling off in the resistance offered by pure lent, and a certain charm is added to his well-modu the "Properties of Liquid Fluorine." In the produc metals to the passage through them of electricity un lated voice by a touch of the Scotch accent which he

tion of the last-mentioned liquid he worked in con der increasing degrees of cold. _ The liquefac still retains. The preparation of his lectures and junction with Prof. H. Moissan. tion of oxygen and air was achieved through the use reports shows great care and precise method. Indeed, It was for his investigations of the properties of of liquid ethylene as a cooling agent, which enabled were it not for this, and his propensity for a happy matter at lowest temperatures that the Rumford a temperature of minus 140 deg. to be maintained by co·ordination of facts, figures, and deductions, the medal was presented to him in 1894 by the Royal its steady evaporation in vacuo. Liquid oxygen is forceful, logical, convincing presentation with which Society, whose president at the time remarked that markedly magnetic, comparing with iron in this he always appears to impress his hearers, would be Prof. Dewar had displayed throughout his researches respect in about the ratio of 1 to 1,000. It is a non impossible. As can be easily realized, it is not an not only marvelous skill and fertility of resource, but conductor of electricity, and an induction coil which easy task, when treating of the very abstruse sub also great personal courage, and that he had not would give a long spark in the air, failed to pierce a j.ects he has dealt with, to adapt to the comprehension alone succeeded in preparing large quantities of liquid layer of liquid oxygen one-tenth of a millimeter thick." of the masses the results of explorations made in oxygen, but that he had, by his device of vacuum. The remarks made at the Belfast meeting would hitherto unknown paths such as we have called to jacketed vessels, been able to store the liquid under now, of course, have to be modified by reason of the attention. atmospheric pressure during long intervals, and thus progress since· made with helium, as shown in Sir His success has been so marked, so extraordinary, to use it as a cooling agent. During his last Friday James's papers (1907), "Studies in High Vacua and of such benefit to mankind, that we must all wish evening lecture of the 1906 season, Sir James Dewar Helium at Low Temperatures" and (1909) "Problems many more days may be spared him to enhance, as explained how, with the aid of charcoal, he had been of Helium and Radium." In the first-named, he inci he surely will, the admirable work he has alreadY able to make these vacuum-jacketed vessels out of dentally explained the very slow process of obtaining accomplished, leading him to disclose many more ' light metals, like copper, nickel, brass, etc., instead helium from gas given off by the King's Well at of the valuable secrets that Nature guards so of the brittle glass hitherto employed. It is now Bath, and alluded to the fact that, in consequence of jealously.