RALPH E. OESPER University of Cincinnati, Cincinnati, Ohio
KUAN,eminent physical chemist, was born on February 6, 1899, a t Maur (Zurich), Switzerland. His father was a minister of the Gospel. His training in chemistry began in 1917 at the Eidgenijssiche Technische Hochschule in Zurich, where he gave particular attention to physical chemistry and electrochemistry. After receiving the degree Engineer-Chemist in 1921, he went to the neighboring University of Zurich, where he served as assistant to Victor Henri in the Physikalisch-Chemisches Institut. The Ph.D. mas obtained in 1923; the dissertation on the photochemical decomposition of ammonia was ranked exceptionally high. Dr. Kuhn mas granted a leave of absence in 1924 and spent the next two years a t the Bohr Institute of Theoretical Physics in Copenhagen. His work there was partly experimental (dispersion of the magnetorotation in metal vapors) and partly theoretical. The outstanding fruit of these latter studies was his (1925) quantum-theory summary of the total strength of the absorption lines coming from one steady state. This statement has played a part in the development of the newer quantum mechanics and also is of significance in wave mechanics. A grant from the International Education Board made this further training possible. Dr. Kuhn returned to Zurich again as assistant in 1926 and habilitated as Privatdozent in 1927 with a study of the strength of the anomalous dispersion in thallium and cadmium vapors. About six months later he accepted an invitation from Professor Karl Freudenberg of the University of Heidelberg to collaborate in a research in the field of natural optical activity. Though on leave from Zurich a t first, Dr. Kuhn later resigned and in 1928 habilitated at Heidelberg, where he remained until 1930. These years were occupied not only by new studies of optical activity but also by researches on the structure of high-molecular materials (especially cellulose) and studies of the atomic nucleus. In order to carry out experimental work in this latter field, Dr. Kuhn twice spent short periods in Rutherford's laboratory at the University of Cambridge. At the invitation of Georg Bredig, Dr. Kuhn habilitated (1930) a t $he Technische Hochschule in Karlsruhe. He served there until 1936, whenhe was called by the
WERNER
University of Kiel as Professor of Physical Chemistry. In 1939, he was recalled to his native country to succeed A. L. Bernoulli as Director of t,he PhysikalischChemische Anstalt of the University of Basel. At present, he is president of the Swiss Chemical Society. Professor Kuhn has an imposing list of papers to his credit. These publications (a. 150) extend over the most varied branches of physical chemistry and the adjoining sciences. A few high lights will demonstrate the calibre of his work. In 1930 he produced optically active materials by irradiation with circularly polarized light; he thus became the first to synthesize an optically active compound from inactive materials. A few years later he was able to predict the absolute configuration of optically active materials on the basis of theoretical considerations. In 1033 he carried out the first photochemital separation of isotopes. His studies in the field of high-molecular compounds began in 1934, when he showed that the "thread molecules" of these materials when in solution have the form of loose coils. With this as a foundation, he subsequently was able to elucidate the elasticity of rubber and to explain especially the viscosit,y and the streaming double refraction of high polymeric materials. In 1941 he turned his attention to the state of the earth's interior, and demonstrated that the earth's core has considerable material homogeneity and does not consist of discrete shells, as was previously assumed. Biological questions have also been considered, such as the relation of the aging of an organism and the irreversible racemisation of the optically active materials in the body. Methods of separating materials, especially dist,illation processes; photochemistry, and photochemical production of anisotropism in colloids are among the other topics which he has successfully investigated. Professor Kuhn has published the following books: "Physikalisch Chemische bunge en" (1929); "Drehung der Polarisationsebene des Lichtes" (1932) ; "Lehrbuch der Physikalischen Chemie" (4th edition, 1948). He is an inspiring teacher and has trained a goodly number of first class chemists, who have learned from him and his successes how a scientific problem should be approached.
