THE TRANSFORMATION OF ELEMEMTS 81 



226*5, this number is y6 x io 21 . In one second therefore the 

 fraction 1*95 x io~ u of the total number of radium atoms dis- 

 integrates ; in a year, of a gram of radium about half a milligram 

 has disintegrated. The average life of radium is hence about 

 1,800 years ; its half-life period 1,300 years. 



Rutherford has more recently modified these figures, his 

 later conclusions pointing to a half-life period of more than 

 2,000 years. 



Ramsay and Soddy used somewhat similar reasoning; they 

 assumed that one atom of radium produces one atom of emana- 

 tion, and that both gases are monatomic. Applying this reasoning 

 to the figures for the volume of emanation obtained by them, 

 Ramsay and Cameron calculated that 1 gram of radium would 

 produce in one day 1*162 cubic millimetres of emanation. 

 Since 1 gram of radium, if monatomic, would occupy (2 x 1 1*2) -r 

 226*5 = ° -1 ntre = iq5 cubic millimetres, the proportion of radium 

 changing per day is 1*162 x io -5 . The average life will be the 



T O 



reciprocal of this number, days or 236 years. No ex- 



planation of these different results has yet been put forward. 



A fairly complete resume of the chemical and physical 

 properties of radium and radium emanation has now been given. 

 Their action as chemical agents is in all probability entirely due 

 to the radiations they emit. A brief mention of these effects 

 has been given in Part I. (vol. ii. pp. 537-8). A more detailed 

 statement follows. 



Giesel was the first to observe that radium salts decompose 

 the water in which they are dissolved. Davis and Edwards 

 have noted a rapid combination of hydrogen and oxygen, when 

 solid radium salt is actually placed in the mixed gases. Ramsay 

 obtained a similar effect by adding emanation to electrolytic gas. 

 When the radium salt is placed in a closed glass bulb, and this 

 immersed in the liquid or gas under observation, any action 

 which takes place must be due to /3 and 7 rays only — derived 

 from radium B and C — for all the a rays are absorbed by the 

 glass envelope. Under such conditions Ramsay has shown that 

 water is not decomposed ; Jorissen and Ringer have observed 

 no combination between hydrogen and oxygen. It therefore 

 . appears that ft rays do not produce these changes ; they are 

 probably due to a rays. 



The observed effects of rays, as shown by the action of 



6 



