Remarque à propos de la découverte du gallium in Comptes Rendus Hebdomadaires des Séances de L'Academie des Sciences 81, 1875, pp. 969-972

Paris: Gauthier-Villars, 1875. 1st Edition. FIRST EDITION OF THE FIRST OF MENDELEEV'S PREDICTED ELEMENTS TO BE IDENTIFIED, thereby confirming "the validity of the periodic system of elements" Mendeleev had designed (Niaz, Critical Appraisal of Physical Science, 62). "The confirmation of this prediction may certainly be called the culminating point in the history of the periodic system" (ibid).

In 1869 "Mendeleev published a periodic table. Mendeleev also arranged the elements known at the time in order of relative atomic mass, but he did some other things that made his table much more successful. He realised that the physical and chemical properties of elements were related to their atomic mass in a 'periodic' way, and arranged them so that groups of elements with similar properties fell into vertical columns in his table.

"Sometimes this method of arranging elements meant there were gaps in his horizontal rows or 'periods'. But instead of seeing this as a problem, Mendeleev thought it simply meant that the elements which belonged in the gaps had not yet been discovered. He was also able to work out the atomic mass of the missing elements, and so predict their properties. And when they were discovered, Mendeleev turned out to be right.

"The discovery of the three elements predicted by Mendeleev was of decisive importance in the acceptance of his law. In 1875 Lecoq de Boisbaudran, knowing nothing of Mendeleev's work, discovered by spectroscopic methods a new metal, which he named gallium. Both in the nature of its discovery and in a number of its properties gallium coincided with Mendeleev's prediction for eka-aluminum, but its specific weight at first seemed to be less than predicted...

"Although Lecoq de Boisbaudran objected to this interpretation, he made a second determination of the specific weight of gallium and confirmed that such was indeed the case. From that moment the periodic law was no longer a mere hypothesis, and the scientific world was astounded to note that Mendeleev, the theorist, had seen the properties of a new element more clearly than the chemist who had empirically discovered it. From this time, too, Mendeleev's work came to be more widely known" (Dictionary of Scientific Biography). CONDITION & DETAILS: Complete volume. Ex-libris bearing only a deaccessioned stamp on the back of the title page and slight ghosting at the spine where a spine level has been removed. 4to (11 x 8 inches; 275 x 200mm). [6], 1450, [2]. Bound in clean full blue cloth, gilt-lettered at the spine. Solidly and tightly bound. Very occasional toning, otherwise clean and bright throughout.