2 Rutherford, Souic Properties of the Radium Enuxnation. 



collected and afterwards measured by the 7 raj- method. 

 At - 50' C. the amount of unabsorbed emanation was less 

 than yV per cent of the total. Above -40° C, the 

 emanation commenced to escapes rapidly, and half had 

 been pumped off at a temperature of 10° C. About 19 

 per cent, remained in the charcoal at 100° C, but prac- 

 tically all was released at a temperature of the softening 

 of glass. It is seen from these results, that at 10' C. the 

 charcoal absorbs about 03 cubic mm. of emanation per 

 gram, and at —40" C. about "06 cubic mm. per gram. 



An experiment was shown to illustrate the rapidity 

 of condensation of pure emanation contained in an 

 exhausted vessel when one point was cooled to the 

 temperature of liquid air. 



