THE TRANSFORMATION OF ELEMENTS 



PART II. RADIUM AND ITS EMANATION 



By A. T. CAMERON, M.A., B.Sc. 

 University College, London 



The first part of this paper contained a brief account of the 

 methods by which the radioactive elements had been discovered, 

 and of their known properties. The fact that radium compounds 

 have been isolated in a state of comparative purity, and in 

 amounts much larger than those of the other active elements, 

 has led to a more complete study of this element. The data 

 have accumulated to such an extent as to demand separate 

 treatment. 



The amount of radium salts actually prepared in any state 

 approaching purity is probably about five grams. It is in exist- 

 ence chiefly as bromide and chloride. Twenty or thirty tons of 

 pitchblende — from the mines at Joachimsthal in Bohemia — were 

 worked up in order to obtain this extremely small quantity. Only 

 three or four investigators have quantities of half a gram or 

 more ; most of the radioactive experiments have been carried 

 out with quantities of from two or three to fifty or sixty milli- 

 grams. It is impossible to obtain an}' appreciable quantity, 

 not only on account of its price — at present about £15 a 

 milligram — but especially because of the limited amount which 

 has as yet been prepared. The output of the Joachimsthal 

 mine is controlled by the Vienna Academy of Science, to whom 

 much credit is due for its loans of large quantities of radium 

 preparations to several of the most distinguished workers in 

 this line of research, whereby much important work has been 

 accomplished. 



The chloride, bromide, sulphate, and carbonate are known. 

 The metal has not yet been isolated ; this is due both to the 

 necessary minuteness of the operations and the great risk of 

 loss. The salts strongly resemble those of the alkaline earths, 

 especially barium, and are given corresponding formulae. The 

 sulphate, RaS0 4 , is even more insoluble than barium sulphate ; 



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