HAHN, O. (OTTO). - THE DISCOVERY OF RADIOTHORIUM.

Über ein neues, die Emanation des Thoriums gebendes radioaktives Element.

Leipzig, S. Hirzel, 1905. No wrappers. Issued in "Jahrbuch der Radioaktivität und Elekronik", 2. Bd., Heft 3. Hahn's paper: pp. 233-264. Enntire issue: pp. 233-262 (= entire "Heft 3"). Fine and clean.

First printing of this paper, which is Hahn's Habilitation paper, announcung his discovery of a new element in residues from a Ceylon mineral called Thorianite. He later showed that it is an intermediate disintegration product.

"Because the sample (thorianite) was small, Ramsay proposed that Hahn confirm Marie Curie's determination of the atomic weight of radium by preparing it in some organic compounds (thereby greatly increasing the total amount being examined) and calculating the atomic weight from the measured molecular weights. Chance sometimes favors the unprepared mind, and Hahn, who familiarized himself with only the basic of radioactivity, followed the prescribed separationss technique and found himself the discovere of a new radioelement: radiothorium. The explanation was that the material given him came from an ore which contained a large percentage of thorium in addition to the radium. Thus, upon completion of the chemical procedure, not all the activity was confined in the radium-containg fraction; indeed the nes subsyance in the remainder was several hundred thousand times more active than thorium and ultimately yielded the characteristic one.minute halflife of thorium emanation."(DSB VI, p. 15). - Weeks, Discovery of the Elements,p. 308 ff.).

Order-nr.: 42829