two or three days, but was unable to get a more accurate value. Hahn concluded that uranium Z and uranium X2 were both the same isotope of protactinium (protactinium-234), and they both decayed into uranium II (uranium-234), but with different half lives. Uranium Z was the first example of nuclear isomerism. Walther Gerlach later remarked that this was "a discovery that was not understood at the time but later became highly significant for nuclear physics". Not until 1936 was Carl Friedrich von Weizsäcker able to provide a theoretical explanation of the phenomenon. For this discovery, whose full significance was recognised by very few, Hahn was again proposed for the Nobel Prize in Chemistry by Bernhard Naunyn, Goldschmidt and Planck. Applied Radiochemistry In 1924, Hahn was elected to full membership of the Prussian Academy of Sciences in Berlin, by a vote of thirty white balls to two black. While still remaining the head of his own department, he became Deputy Director of the Kaiser Wilhelm Institute for Chemistry in 1924, and succeeded Alfred Stock as the director in 1928. Meitner became the director of the Physical Radioactivity Division, while Hahn headed the Chemical Radioactivity Division. In the early 1920s, he created a new line of research. Using the "emanation method", which he had recently developed, and the "emanation ability", he founded what became known as "applied radiochemistry" for the researching of general chemical and physical-chemical questions. In 1936 Cornell University Press published a book in English (and later in Russian) titled Applied Radiochemistry, which contained the lectures given by Hahn when he was a visiting professor at Cornell University in Ithaca, New York, in 1933. This important publication had a major influence on almost all nuclear chemists and physicists in the United States, the United Kingdom, France, and the Soviet Union during the 1930s and 1940s. In 1966, Glenn T. Seaborg, co-discoverer of many transuranium elements, wrote about this book as follows: Hahn is referred to as the father of nuclear chemistry, which emerged from applied radiochemistry. National socialism Fritz Strassmann had come to the Kaiser Wilhelm Institute for Chemistry to study under Hahn to improve his employment prospects. After the Nazi Party came to power in Germany in 1933, Strassmann declined a lucrative offer of employment because it required political training and Nazi Party membership, and he resigned from the Society of German Chemists when it became part of the