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Vol. 33 No. 5
September-October 2011

Stamps International |

See also www.iupac.org/publications/ci/indexes/stamps.html


Avogadro’s True Legacy

The centennial of Marie Curie’s Nobel Prize in Chemistry, which she received in 1911 for the discovery of radium and polonium, has been extensively (and deservedly) publicized during the International Year of Chemistry. Many other scientific anniversaries are also worth remembering this year, such as the 50th anniversary of the first successful generation of the element lawrencium by a team led by Albert Ghiorso at the Lawrence Berkeley National Laboratory. The year 2011 also marks the 100th anniversary of the discovery of superconductivity by the Dutch physicist Heike Kamerlingh Onnes (1853–1926), who was rewarded with the Nobel Prize in Physics for his seminal work only two years after the phenomenon was first observed. And the American chemist Melvin Calvin (1911–1997) ought to be remembered this year for the centenary of his birth but, more importantly, for the 50th anniversary of the Nobel Prize in Chemistry with which he was honored for his influential work on the assimilation of carbon dioxide in plants.

The stamp illustrated herein was issued back in 1956 to commemorate the 100th anniversary of the death of Amedeo Avogadro (1776–1856), the Italian savant whose name is most commonly associated with the number of elementary entities or particles in a mole (i.e., Avogadro’s number or constant) but who had nothing to do with the experimental determination of such value. Instead, Avogadro’s key contribution, stated in an insightful essay published exactly 200 years ago, consisted of suggesting that “equal volumes of gases at the same temperature and pressure contain equal numbers of molecules” and implied that the ratio of the densities of two gases is directly related to the ratio of their molecular weights. Avogadro’s law, as it is now known, written in his native language, is shown together with his portrait and signature on the stamp above. Significantly, Avogadro’s ability to ascertain the difference between atoms and molecules also helped solve the problem of assigning the correct molecular formulas to pure substances, which had afflicted the theories of his contemporaries Joseph Louis Gay-Lussac and John Dalton, and thus played a key role in the development of the modern concepts of atomic structure and molecular bonding.

Written by Daniel Rabinovich <drabinov@uncc.edu>.


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