150th Anniversary of Mendeleev’s Proposal of the Periodic Table of Elements
From Wikipedia: The Russian chemist Dmitri Mendeleev arranged the elements by atomic mass, corresponding to relative molar mass. It is sometimes said that he played “chemical solitaire” on long train journeys, using cards with various facts about the known elements. On March 6, 1869, Mendeleev gave a formal presentation, The Dependence Between the Properties of the Atomic Weights of the Elements, to the Russian Chemical Society. In 1869, the table was published in an obscure Russian journal and then republished in a German journal, Zeitschrift für Chemie.