Technikatörténeti szemle 25. (2001-02)
Papers of the Third International Conference on the History of Chemistry and Chemical Industry (Budapest, 2–4 July, 1999) – First Part - Tansjö, Levi: Mendelejev and the Nobel Prize in chemistry
said that he didn't think that its density was about 3 grams/cm 3 as de Boisbaudran had found it to be. It should instead, according to Mendelejev, who had not seen the new element, be more than 5 grams/cm 3 - and he was right. The density was leter om found to be 5,9 grams/cm 3 . Four years later, in 1879, Fredrik Nilson at the University of Uppsala isolated from a mineral found in Norway the oxide of an unknown metal which turned out to be Mendelejev's eka-boron. It was given the name Scandium after Scandinavia. In 1886 Clemens Winkler at the Freiberg School of Mines in Saxony discovered in the mineral argyrodite a new element which he gave the name germanium after Germany. I turned out to be Mendelejev's eka-silicon. The Belgian chemist Stas had found that so many of the atomic weights were so far from whole numbers that he threw away William Prout's hypothesis from 1815 that all atomic weights were whole number multiples of the atomic weight of hydrogen. But there was something mysterious. About one third of Stas' atomic weights were in fact very close to whole numbers and there was no good explanation for that until the 1920s. Then it was found with mass-spectrometry that for 19 of the elements only one isotope occurs in nature and that for about the same number of elements one isotope is so dominant that the atomic weight again comes close to a whole number. Because of that many chemists continued after Stas to believe in Prout's hypothesis. That Lord Rayleigh in the late 1880s so carefully studied the densities of oxygen and nitrogen was probably because he thought that he would find oxygen exactly 16 times as heavy as hydrogen and nitrogen exactly 14 times as heavy as hydrogen in agreement with Prout's hypothesis. During that study he found that nitrogen isolated from air was a little heavier than nitrogen gas obtained from ammonia. William Ramsay joined him in this research and in 1894 they could at the meeting of the British Association for the Advancement of Science in Liverpool together announce that air beside oxygen and nitrogen contains about one % of another element, an inert gas, which they called argon (the lazy one). Until 1898 Ramsay and his co-worker Travers discovered in the air four more gaseous new elements, all of them inert gases. They got the names helium, neon, krypton and xenon. These new elements could easily be placed in the Periodic Table in their own group between the most electronegative elements, the halogens, and the most electropositive ones, the alcalimetals. This was of course a new great triumph for Mendelejev. Important discoveries were made in the 1890s. On a Friday evening in October 1895 Conrad Wilhelm Röntgen discovered the mysterious rays he called X-rays until they in Germany, Russia, Scandinavia and some other countries got the name Röntgen-rays. A few months later on in 1896 Henri Becquerel in Paris discovered that also uranium and its compounds gave a radiation which just like Röntgen-rays ionized air and other gases making them to conductors of electricity. In 1887 Joseph John Thomson at the Cavendish laboratory in Cambridge discovered the electron. The chemists then could say: The electron is presumably the atom of electricity, we are
