476 The Spectrum of the Radium Emanation. [May 18, 



in 1900, it was suggested that no element should receive a name until 

 its spectrum had been mapped. Of course, the converse does not 

 follow, that, after the spectrum of an element has been mapped, it 

 should receive a name. The " emanation from radium," however, is a 

 cumbrous expression, and sufficient evidence has now been accumu- 

 lated that it is an element, accepting that word in the usual sense. It 

 is true that it is only a transient element, and ought in justice to be 

 called a compound ; but of what 1 It stands on a wholly different 

 plane to any known compound in the amount of heat with which it 

 parts during its spontaneous change, and in the peculiar electrical 

 phenomena which accompany its transformation. It is a gas ; it 

 follows Boyle's law ; as Eutherford and Soddy have shown, it 

 resembles the gases of the argon series in its indifference to chemical 

 reagents, for it not merely withstands the prolonged action of mag- 

 nesium-lime at a red heat, but also, as Ramsay and Soddy have 

 proved, prolonged sparking with oxygen in presence of caustic potash. 

 Its molecular weight has been found to be nearly 200, and, if it is 

 monatomic, that number would also express its approximate atomic 

 weight. Now, it appears advisable to devise a name which should 

 recall its source, and, at the same time, by its termination, express the 

 radical difference which undoubtedly exists between it and other 

 elements. As it is derived from radium, why not name it simply 

 " exradio " ? Should it be found that the emanation, which is sup- 

 posed to be evolved from thorium, is really due to that element, and 

 not to some other element mixed with thorium in exceedingly small 

 amount, a similar name could be given, namely, "exthorio." If the 

 existence of actinium as a definite element is established, its emana- 

 tion would appropriately be named " exactinio." It is unlikely that 

 others will be discovered, but, if they are, the same principle of nomen- 

 clature might be applied. 



It should be stated, in conclusion, that Mr. Soddy collaborated in 

 the experiments preliminary to this successful mapping of the 

 spectrum ; had he not been obliged to leave England, he would, no 

 doubt, have shared whatever credit may attach to this work. 



