. Radio-activity : an elementary treatise from the standpoint of the disintegration theory . ter part of the radio-activity of the original for weight, the radium compounds are at least amillion times more active than the compounds of uraniumand thorium. This numerical comparison hardly conveys atrue impression of the relative activities. A clearer idea isgiven by a concrete example. If a radium compoundproduced a given effect, for example, on a photographicplate, in one second, a similar weight of uranium com-pound would take several weeks to produce the same is ill
. Radio-activity : an elementary treatise from the standpoint of the disintegration theory . ter part of the radio-activity of the original for weight, the radium compounds are at least amillion times more active than the compounds of uraniumand thorium. This numerical comparison hardly conveys atrue impression of the relative activities. A clearer idea isgiven by a concrete example. If a radium compoundproduced a given effect, for example, on a photographicplate, in one second, a similar weight of uranium com-pound would take several weeks to produce the same is illustrated by Figs. 3 and 4. The first illustratesa radiograph of an aluminium medal taken with uraniumrays in which probably several grammes of a uraniumcompound were employed, and the exposure given was14 days. The second illustrates a negative obtained bymerely writing slowly on a photographic plate with atube containing a few thousandths of a gramme of a pureradium preparation. The use made by M. and Mme. Curie of the property ofradio-activity as a means of detecting and separating new. Fig. 3.—Eadiograph of an Aluminium Medal taken by M. Becquerel with the Uranium Eays. Exposure: A fortnight. (From Rapports du Coagres International de Physique, 1900, Tome III., p. 51.)
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