Radio-Active Substances

Radio-Active Substances is a thesis presented to the Faculté des Sciences de Paris, reprinted from the Chemical News. The text asks whether the emission of Röntgen rays necessarily accompanied the production of fluorescence, whatever might be the cause of the latter.

According to the text, M. Becquerel made similar experiments on the salts of uranium, some of which are fluorescent, and obtained photographic impressions through black paper with the double sulphate of uranium and potassium. Becquerel is said to have at first believed that the salt, which is fluorescent, behaved like the sulphides of zinc and calcium, but that the conclusion of his experiments showed the phenomenon observed was in no way related to the fluorescence. Polonium is described as emitting rays which are readily absorbed and which can only pass through extremely thin screens. A heated radium salt is said to show a greatly increased external emission of the emanation.