350 



Sir W. Bamsay and Mr. F. Soddy. 



[Apr. 14, 



decreased, and on lowering it, the glowing gas appeared to lie on the 

 surface of the mercury for a fraction of a second, falling with the 

 falling mercury ; but it soon spread through the whole barrel by 

 diffusion. 



The bubble of gas pumped out was treated with a drop of caustic 

 potash, when a considerable fraction was absorbed. By next day the 

 volume of the bubble had increased. 



Inasmuch as all samples of emanation showed the spectrum of 



Fia. 4. 



carbon-dioxide, the presence of which was believed to be due to the 

 oxidation of the tap-grease, an apparatus was constructed in which 

 the use of taps was, as much as possible, avoided. All the emanation 

 from about 60 milligrammes of radium bromide was introduced into 

 the burette A, the only gas present being oxygen. From the burette 

 it passed through the bulb B, which contained concentrated potash 

 solution ; it then passed through C, which was charged with solid 

 potash and was deprived of moisture by contact with phosphorus 

 pentoxide in D. The level of the mercury in the trap was at E, so 

 that the emanation reached the spiral G, cooled with liquid air ; the 



