580 Prof. E. Rutherford and Mr. F. Soddy on 



measured. Fig. 2 expresses the results. The decay- curve 

 is merely approximate, for it is not easy to accurately take 

 the emanating power of a liquid without special arrangements 

 to assure the constancy of the air-current and the shaking of 

 the solution. 



Fio-. 2. 



























































80 

















V^V 

















\ 





A 

























N 



V 



f 

























/ 



A 



^ 



















40 







/ 







^ 



s 

















/ 

























20 



/ 



/ 















X 



> 









/ 



























( 



/ 









•Time 



inOc 



us- 















The experiments, although only of a preliminary character, 

 bear out the conclusion that emanating power decays and 

 recovers according to the same law and at the same rate as 

 the radioactivity of ThX, and that it is therefore one of the 

 properties of the latter and not of thorium. The decay-curve 

 given, so far as it can be relied upon, shows that the eman- 

 ating power of ThX at any instant is proportional to its 

 radioactivity. 



VI. The Chemical Nature of the Emanation. 



The following work has reference to the emanation itself, 

 and not to the material producing it, and was designed to see 

 whether the emanation possesses chemical properties which 

 would identify it with any known kind of matter. It had 

 been noticed at the time of its discovery that it passed 

 unchanged through concentrated sulphuric acid. The same 

 holds true of every reagent that has been investigated. 



The effect of temperature was first tried. The air con- 

 taining the emanation, obtained in the usual way by passage 

 over thoria, was led through the platinum tube heated 



