RALPH E. OESPER University of Cincinnati, Cincinnati, Ohio T H E internationally known inorganic chemist, Wilhelm Karl Klemm, was born on January 5, 1896, a t Guhrau in eastern Germany. He entered the nearby Uoiversity of Breslau in 1919 and received the Ph.D. degree in 1923. His dissertation, which dealt with uric acid, was prepared under the guidance of Heinrich Biltz (1865-1943), who sent the promising young man to the Technische Hochschule a t Hannover for further training under his brother Wilhelm Biltz (1877-1943).' Dr. Klemm was assistant until 1927 when he became Privatdozent and then Associate Professor in 1929. He headed the inorganic laboratory a t Danzig from 1933 until 1945, when the conquest of the city by the Soviets made flight necessary. He was at the University of Kiel in a like capacity, from 1947 to 1951, when he came to his present post, Director of the Institut fiir anorganische Chemie a t the University of Miinster. Professor Klemm's researches have been many and varied. His first studies were in collaboration with W. Biltz and dealt with the conductivity of fused salts. They found that the high-melting halides are good conductors, in contrast to the low-melting ones, which conduct poorly; clear relationships t o the periodic system of the elements were brought to light. The investigations were extended to the study of the molvolumes and the coefficients of expansion of the fused halides, and the data obtained likewise gave insights into the molecular states obtaining in the melts. Furthermore, the expansion coefficients of the solid halides were measured and again systematic relationships were uncovered. As a supplement to these studies, the halogen and chalcogenic compounds of several uncommon elements (indium, gallium, rare earths, germanium, rhenium) were investigated in detail; the heats of formation and the reactivity toward ammonia were determined. Study of the compounds of the rare earths led to the discovery of bivalent ytterbium. Moreover, a new method for classifying the rare earths was evolved, a system that has now been quite generally adopted. The decisive factor was recognized t o be the stability not only of the completely filled but also the "half-filled" electron configuration, such as is found in Gd+3. Subsequently, this systematization was applied to the transition elements, and the special properties of Mn++ compounds were explained. The new classification of the rare earths, which at the start held only for the ions, was found to be valid also for the metals themselves. The latter were prepared, with the collaboration of H. Bommer, by means of the react,ion: MeC4 3K = 3KCI Me, and studied roentgenographically and
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magnetically. The atomic volume curves of the rare earths, which could then be constructed for the first time, show distinct maxima in the case of ytterbium and europium and flat minima for cerium, praseodymium, and terbium. Like gadolinium, practically all the other yttria earths are ferromagnetic a t low temperatures. Magnetic measurements, which had been employed in the above investigations, were used, from 1930 on, to a much greater degree for the solution of chemical problems. In addition to other compounds of the rare earths, numerous complex compounds were measured, particularly simple compounds of the transition elements, including those with semimetallic character. The importance of atomic bonding between the cations (antiferromagnetism) was recognized independently of other workers, and applied liberally to account for the experimental findings. A classification system was developed also for the diamagnetism of ions. Studies of alkali metal compounds led to, among other things, the discovery that the 0%ion occurs not only in dioxides but also in the oxides Rb203 and Cs208,whose structures were thus elucidated. In the field of intermetallic systems, studies were made of the behavior of the alkali and alkaline earth metals toward each other, and toward magnesium, and many systems with semimetals were also investigated. For the transition from the true metals to the semimetals it was proposed that the following categories be adopted: true metals, metametals, semimetals, nonmetals. The decrease in volume when gallium, silicon, germanium, and bismuth melt was explained. The volume-temperature curve of tellurium was found t o have a minimum. I n another important series of researches, definite evidence was obtained for the existence of gaseous compounds of univalent aluminum with all halogens, sulfur, and selenium. Numerous studies were devoted to fluorine compounds. For example, measurements were made of the refractive power of SF6 etc.; CeF. and the fluorides of gallium and indium were prepared. Complex fluorides which have abnormal valenre, such as K3[Cu(ITI)Fe], Kz[Ni(IV)Fe],K2[Cr(IV)F6],etc., were produced by the action of fluorine on various appropriate compounds 01 mixtilrps --. ..
I n addition to his many papers, Professor Klemm has authored or collaborated on a number of books. These include: "Magnetochemie" (1937), which was reprinted at Ann Arbor in 1944 as Volume I of "Physik und Chemie und ihre Anwendungen"; and "Chemische Binding als electrostatische Erscheinung"
JULY, 1952
(1931) which is his translation of A. E. van Arkel and J. H. de Boer's "Chemische Binding als elektrostatische Verschynsel." He collaborated with W. Biltz on the latter's "Raumchemie der festen Stoffe," which likewise mas reprinted at Ann Arbor in 1944. For student use he published an L'Introductionto Inorganic Chemistry" (5th edition, 1952). Together with Werner Fischer, he issued several revisions of the Biltz "Experimentelle Einfiihrung in die anorganische Chemie," which has now gone through more than 40 editions.
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Professor Klemm is one of the three chief editors of the Zeitschrijt jfiir anorganische und allgemeine Chemie. Furthermore, he edited the six volumes of the inorganic section of the "Fiat Review," and also "The Review of Analytical Chemistry in Germany 193G1946," an important record of German chemistry during the World War I1 era. His honors include the Justus von Liebig Medal of the Gesellschaft Deutsche~.Chemiker (1951), whose presidency he holds for 1952 and 1953.
