Triads, Triads, Everywhere
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Johann Wolfgang Döbereiner (1780-1849), a professor of chemistry at the University of Jena, was the first to recognize that several groups of three elements, such as lithium, sodium, and potassium, or chlorine, bromine, and iodine, had similar chemical properties. In addition, he noticed that the atomic weight of the middle element in these triads was roughly the average of those of the other two. These observations led to his Law of Triads (1829), which firmly established his reputation as a pioneer in the development of the modern periodic table some 40 years before Mendeleev’s masterpiece was published.
However, the stamp illustrated in this note, issued in East Germany (DDR) on 26 February 1980 to commemorate the 200th anniversary of Döbereiner’s birth (which was actually on 13 December 1780), does not mention his seminal contribution to the organization of the elements but features instead his “other” claim to fame. The stamp shows a schematic drawing of his renowned lighter, in which a stream of hydrogen gas, generated from zinc and sulfuric acid, spontaneously ignites upon contact with finely divided platinum. This novel chemical reaction received a lot of attention since it was first described by Döbereiner in the summer of 1823 and was swiftly reproduced by others. Within months the discovery was reported in multiple European scientific journals, which ushered in an era of interest in catalysis that continues to this day.
For a recent discussion of triads in the periodic table, see: Scerri, E. J. Chem. Educ. 2008, 85, 585-589.
Written by Daniel Rabinovich <drabinov@uncc.edu>.
Page last modified 5 June 2008.
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