on the first anniversary of his death. University professors were forbidden to attend, so they sent their wives in their place. Hahn, Planck and Joseph Koeth attended, and gave speeches. The aging Planck did not seek re-election, and was succeeded in 1937 as president by Carl Bosch, a Nobel Prize winner in Chemistry and the Chairman of the Board of IG Farben, a company which had bankrolled the Nazi Party since 1932. Ernst Telschow became Secretary of the KWS. Telschow was an enthusiastic supporter of the Nazis, but was also loyal to Hahn, being one of his former students, and Hahn welcomed his appointment. Hahn's chief assistant, Otto Erbacher, became the KWI for Chemistry's party steward (Vertrauensmann). Rubidium–strontium dating While Hahn was in North America, his attention was drawn to a mica-like mineral from Manitoba that contained rubidium. Some years before he had studied the radioactive decay of rubidium-87, and had estimated its half life at 2 x 1011 years. It occurred to Hahn that by comparing the quantity of strontium in the mineral (which had once been rubidium) with that of the remaining rubidium, he could measure the age of the mineral, assuming that his original calculation of the half life was reasonably accurate. This would be a superior dating method to studying the decay of uranium, because some of the uranium turns into helium, which then escapes, resulting in rocks appearing to be younger than they really were. Jacob Papish helped Hahn obtain several kilograms of the mineral. From 1,012 grams of the mineral, Strassmann and Ernst Walling extracted 253.4 milligrams of strontium carbonate, all of which was the strontium-87 isotope, indicating that it had all been produced from radioactive decay of rubidium-87. The age of the mineral had been estimated at 1,975 million years from uranium minerals in the same deposit, which implied that the half life of rubidium-87 was 2.3 x 1011 years: quite close to Hahn's original calculation. Rubidium–strontium dating became a widely used technique for dating rocks in the 1950s, when mass spectrometry became common. Discovery of nuclear fission After James Chadwick discovered the neutron in 1932, Irène Curie and Frédéric Joliot irradiated aluminium foil with alpha particles, they found that this results in a short-lived radioactive isotope of phosphorus. They noted that positron emission continued after the neutron emissions ceased. Not only had they discovered a new form of radioactive decay, they had