628 NATURE APRIL 15, 1939, VoL. 143

Obituary Notices

Prof. H. M. Dawson, F.R.S. not only for the students of pure but also ARRY MEDFORTH DAWSON, professor of for those of the various departments of applied H physical chemistry in the University of Leeds chemistry and medicine, and in 1920 a professorship since 1920, died on March 9 at the age of sixty-three in physical chemistry was instituted, to which he was years, after an illness which had disabled him during appointed. Throughout this time he had been an the whole of the current University session. indefatigable worker, whose laboratory light was All his life, apart from three years' Continental shining on most evenings and who seemed to regard training, was spent in Leeds, first at the L!leds Modern the University vacation as a provision for minimizing School and then in turn as student, demonstrator, interruption to research work. It was only during lecturer and professor at the University of his home the last few years that warning of overstrain necessi• city. In the last year of his studentship at Leeds he tated some diminution of effort. was engaged on reseaTch work with Prof. A. Smithells, Dawson's literary output was almost entirely that and received the highest award then open to a student of his papers in the Journal of the Chemical Society, of science in his election to the 1851 Exhibition. but he also contributed the section on general and There followed three years at Berlin, Leipzig and physical chemistry to several numbers of the annual Giessen, which were all-important in bringing home report of the Society and was one of the authors to him the conviction that no work could hence• drawn upon by Abegg for his (German) treatise on forth make the first claim on his time and thought chemistry. but that of research. Dawson's departmental preoccupations left him This inspiration came at a time when the atmo• little time for the more general administrative work sphere of the German universities was permeated by of the University, nor was it with him a primary the research spirit to an extent then almost unknown interest, but he concerned himself with the award in Great Britain, when brilliant young men were of scholarships, was for a considerable period .a forming the research habit, and when new vistas representative of Leeds on the Joint Matriculation were being opened out by theories and experimental Board of the Northern Universities, and at different investigations of the first importance. In the years times was dean of the Faculty of Science and the just preceding, van't Hoff's original paper on representative of Convocation on the Council. He "Osmotic Pressure and the Thermodynamic Deduc• will also be remembered as for many years the secretary of the Priestley Club, with a membership tions for Dilute Solutions," Arrhenius's "Theory of Isohydric Solutions" and Nemst's "Electromotive drawn from inside and outside the University, and notable for its friendly informality and the wide range Activity of the " had been published and Ost• of its scientific interests. wald's text-books were presenting physical chemistry Prof. Dawson was fortunate in his family life. He in a new light. Dawson and fellow-students from married Miss Phillis Mary Barr, and she, with three Great Britain (including Donnan), were brought sons and two daughters, survives him. under vivifying influences of personal contact and JoaN W. CoBB. example and of the written word. On returning from Germany with a Ph.D. from the University of Giessen, he was appointed to a demonstratorship in Dawson's researches on solutions form a con• physical chemistry in the department at Leeds from tribution to chemical science of great significance which he had gone as a student. From then onwards and importance. His earlier work was connected in came a steady stream of papers on the mechanics of the main with various aspects of chemical equilibria chemical change in solutions, embodying the results and more particularly with the formation of complex of experimental work carried out by himself and ions. Thus he was able, by means of distribution many senior students who received in succession the experiments, to establish the existence of the complex

benefit of his training in research methods. A vast (Cu4NH3 ) + + in ammoniacal copper sulphate amount of matter was thus accumulated, and it was solutions. The other group of compounds in which his reward that after many years a more generalized he was interested was the polyiodides. Here, having treatment of the results became possible. He was confirmed J akowkin's conclusion of the existence of elected to the fellowship of the Royal Society in the tri-iodide in aqueous solutions, he extended the 1933, to the great gratification of his friends, who had observation to organic solvents such as nitrobenzene, come to fear that his devotion to work in the labora• in which he showed that, under appropriate conditions,

tory at Leeds rather than its effective exposition the higher polyiodides Kl9 , KI7 , KI6 exist in significant elsewhere might tell against that form of recognition. proportions. He had received the D.Sc. degree of Leeds many Although this work was of considerable importance, years before, in 1907. Dawson's name will be particularly associated with Meanwhile, as primarily responsible for the lectur• the kinetic measurements which were so largely ing and laboratory teaching in physical chemistry in instrumental in the successful development of the the University, Dawson had developed the subject modern theory of and bases. A commencement

© 1939 Nature Publishing Group No. 3624, APRIL 15, 1939 NATURE 629 was made in 1909, ;vhen, following Lapworth's University he soon found himself consulting chemist classical experiments on the bromination and chlor• to the Danish Naval Department's Laboratory. As ination of acetone, it was shown that iodination is the result of his work on cobalt oxalates he obtained similar in that the chemical change the speed of which the degree of doctor of philosophy in 1899. From what is measured is the conversion of the ketone into the we know of Sorensen's early activities it is scarcely enol form. This was followed by a study of the surprising to find that at the age of thirty-three years catalysis of the reaction by acids, which led in 1913 he was appointed director of the world-famous Carls• to the conclusion that both the ionized and un• berg Laboratory in , a position he held ionized portions of an exert a catalytic effect. until his lamented death in the present year. With The work was not resumed until some years after the passing of Sorensen, the Laboratory has the Great War, but then followed a rapid succession lost another of its distinguished line of workers. of papers which resulted in the establishment of the Who will forget Emil Ch. Hansen, its first director, multiple theory of catalysis. The reactions studied whose work on the cultivation of single-cell included the iodination of acetone, the hydrolysis of created such a drastic change in Continental methods ethyl acetate, the iodination of mesityl oxide and the of ; Johannes Schmidt, the eminent bio• intramolecular transformation of phorone, all of logist, or Sorensen's immediate predecessor, Job. which are catalysed by acids and bases. Dawson Kjeldahl, whose name is familiar to everyone who demonstrated that in these reactions it is necessary has ever made a determination of nitrogen? to attribute catalytic activity not only to hydrion Although primarily interested in fermentation and the hydroxyl ion, but also to undissociated acid problems, Sorensen's classic work on hydrogen ion molecules and to acid anions, and in fact to any concentration will remain as a permanent monument substance which can either receive or donate a proton, among t,hose who know little of his other work. The that is, to any substance which in the Bronsted• term 'pH' has become so much a part of scientific Lowry view is an acid or . Dawson was not literature and its influence so important a factor in content until his multiple theory was proved up to considering biological problems that one wonders the hilt, and to this end he subjected the very con• how theories of acidity and alkalinity were ever siderable amount of experimental material to an formulated without a knowledge of Sorensen's funda• exhaustive and searching analysis. A more complete mental conceptions. So far has the influence of this and convincing proof of a scientific theory has rarely famous theory spread that to-day one hears golfers been achieved. talking of the pH of their 'greens' and gardeners of An account of Dawson's work irr this field would their lawns. be incomplete without some mention of his contribu• Less spectacular perhaps, but equally important tion to our knowledge of the effect of catalytically in the region of fermentation, was Sorensen's work inert salts on the strength of acids, the effect which on the synthesis of amino-acids, his studies on the Bronsted calls the secondary salt effect. By means proteins and his detailed and comprehensive investiga• of kinetic measurements he showed that the dissocia• tion of enzyme behaviour. This latter study led him tion constant of an acid is markedly affected by the to perfect the well-known 'formal-titration' method presence of such salts. The change in dissociation for the estimation of certain types of nitrogen. constant is represented by an equation of the same Although Sorensen published from time to time in form as that to be anticipated by the application of the Journal of the Institute of Brewing, most of his the Debye-Hiickel theory of strong electrolytes, but original work appeared in the Biochemische Zeitschrift Dawson was at pains to emphasize that quantitatively and the Oomptes rendus of the Carlsberg Laboratory. the results are incompatible with this theory. Sorensen was an early member of the Royal During the last few years, Dawson was engaged Danish Academy of Science and later its chairman. in a study of the kinetics of the hydrolysis of the He enjoyed honorary membership of a very large halogenated acetates. He revealed the complex number of scientific bodies, including institutions in nature of these apparently simple processes, and by Uppsala, Stockholm, London, Paris, Boston (U.S.A.) an extremely elegant method succeeded in dis• and in other countries. He held three Danish Orders entangling the various reactions, and evaluating the in addition to the Chevalier de la legion d'honneur corresponding coefficients. and other foreign decorations. R. WHYTLAW-GRAY. I cherish .the recollection of a happy meeting with G. F. SMITH. this remarkable man in his laboratory in Copen• hagen. He was kindly, courteous, ever willing to listen to those who had not his fund of knowledge Prof. S. P. L. Ssrensen and always ready and glad to impart something from 0REN PETER LAURITZ S0RENSEN, whose his vast store of learning. S111rensen was happy in his S death, at the age of seventy-one years, was domestic life and his second wife, Margrethe H111yrup, recently announced, was the son of a farmer, Hans a woman of considerable intellectual ability, collab• Sorensen. He was born at Havrebjerg, Slagelse, on orated with him in much of his later published work. January 9, 1868. S111rensen's reputation is assured, and his name will Leaving the High School at Soro in 1886, Sorensen go down among the most illustrious of the past. With proceeded to the University, where he gained the his going the world of science loses one of its great University Gold Medal in the years 1889 and 1895. men and one of her most worthy sons. Having taken the degree of master of science at the A. J. CURTIN COSBIE.

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