RADIOACTIVITY 1 



BY MADAME MAEIE CUKIE 



A BRIEF RESUME OF OUR PRESENT KNOWLEDGE 



THE discovery of radioactivity is comparatively recent, 

 going back only to 1896, the year in which the radiant 

 properties of uranium were proved by Henri Becquerel. 



The development of the science since has been extremely 

 rapid, and among the numerous results obtained are some 

 whose general scope is so widely extended that radioactivity 

 constitutes to-day an independent and important branch of 

 the physico-chemical sciences occupying a precisely defined 

 field of its own. 



In the study of radioactivity the knowledge of the 

 chemist and that of the physicist find applications of equal 

 importance. 



If the methods of analytic chemistry are constantly em- 

 ployed for the extraction of radioactive substances from 

 their mineral compounds, various methods of physical 

 measurement, and in particular, of electrometry, are of 

 current usage for the study of these substances. 



It is particularly interesting to remark the close connec- 

 tion which exists between the rapid development of 

 radioactivity and the results obtained in a series of theo- 

 retical and experimental researches upon the nature of 

 electromagnetic phenomena, and upon the passage of the 

 electric current through gases. 



These researches, which have established with great pre- 

 cision the conception of the corpuscular structure of 

 electricity, comprise the study of the cathodic and positive 



1 Introduction to Madame Curie's Traite de Radio-active, pub- 

 lishers, Gauthier-Villars. Translation in Scientific American Sup- 

 plement, December, 1910, used by permission of the author. 



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