THE TRANSFORMATION OF ELEMENTS. 



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



University College, London 



PART III 



SECTION PAGE 



i. The Production of Helium during Radioactive Changes . 222 



2. Recent Attempts at Transmutation 226 



3. Chemical Evidence of Transformation 236 



Section I. — The Production of Helium during Radioactive 



Changes 

 Mention has been made already of the change of radium 

 emanation into helium, predicted by Rutherford and Soddy, 

 and actually observed by Ramsay and Soddy. The apparatus 

 employed was in great part similar to that shown in fig. 1, 

 Part II. (p. 74). The initial observation, of which an account 

 was published in 1903, was made with the gases evolved from 

 20 milligrams of pure radium bromide, dissolved in water. 

 The hydrogen and oxygen were removed by contact with a 

 red-hot spiral of copper wire, partially oxidised, and the re- 

 sulting water vapour by a tube of phosphorus pentoxide. The 

 remaining gas was forced into a small spectrum tube connected 

 with a U-tube. It showed the spectrum of carbon dioxide ; but 

 on cooling the U-tube in liquid air most of the carbon dioxide 

 condensed, and the yellow line (D 3 ) of helium became visible in 

 the spectrum. This was conclusively identified. 



A second experiment with 30 milligrams of bromide gave a 

 better result : the carbon dioxide was removed completely, and 

 most of the lines in the helium spectrum were observed. Several 

 further experiments were carried out with similar results. 



Attempts were made, which have already been described 

 (p. 76), to measure the volume of the emanation. The capillary 

 tube used for measurement had a very fine platinum electrode 

 fused in at the upper end. As the gas was confined over 

 mercury, the capillary itself could be used as a spectrum tube. 



In this experiment the emanation was condensed at liquid air 



222 



