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‎Sur la radioactivité de l'uranium.‎

‎(Paris, Gauthier-Villars), 1901. 4to. No wrappers. In: ""Comptes Rendus Hebdomadaires des Séances de L'Academie des Sciences"", Tome 133, No 24.. Pp. (969-) 1044. (Entire issue offered). Becquerel's paper: pp. 977-980.‎

‎First appearance of this historical paper in which Becquerel relates THE FIRST EVIDENCE OF A RADIOACTIVE TRANSFORMATION. ""Nothing that Becquerel subsequently accomplished (after his discovery of radioactivity in 1896) was as important as this discovery, by which he opened the way to nuclear physics. Nevertheless, there were two other occasions on which he stood directly on the path of history: when he identified electrons in the radiations of radium (1899 - 1900) and when he published the first evidence of a radioactive transformation (1901). (The paper offered).""(DSB).""To prove his supposition that the uranium would recover its activity, Becquerel set aside some of the inactive uranium solution and its radioactive barium sulfate precipitate for a period of 18 months. Late in 1901, he found that the uranium had completely regained its activity, whereas the barium sulfate precipitate had become completely inactive. Becquerel wrote: ""The loss of activity ... shows that the barium has not removed the essentially active and permanent part of the uranium. This fact constitutes, then, a strong presumption in favor of the existence of an activity peculiar to uranium, although it is not proved that the metal be not intimately united with another very active product.""‎