WORK ON EADIUM 171 



thorium preparations, equal in activity to radium, were 

 soon put on the market in Germany. In 1910 the 

 question of the chemical properties of mesothorium was 

 investigated by Professor Soddy, 1 who found that meso- 

 thorium was non-separable from radium. Consequently 

 the radium prepared from thorianite in Ramsay's experi- 

 ments contained the mesothorium. And as meso- 

 thorium gives rise in its radio-active change to radio- 

 thorium the latter becomes associated, in the process 

 of fractionation, with the thorium present from which 

 it is non-separable. The radio thorium obtained by 

 Ramsay and Hahn was therefore a new-born product 

 formed during the process of fractional crystallisation. 



1 Transaction* of the Chemical Society, 1911, p. 72. 



