

1903.] Effect of Extreme Cold on the Emanations of Radium. 71 



more marked with the pure compound than had been formerly 

 observed with the diluted mixtures containing large quantities of 

 barium salts. 



Professor Kutherford and Mr. Soddy have made the important 

 discovery that a condensible emanation is diffused into gases from 

 solutions of radium salts, which is capable of condensation from the 

 gas mixture at the temperature of liquid air. As it was important to 

 ascertain what was taking place in this respect with the anhydrous 

 radium bromide when isolated in the highest vacuum, the following 

 experiment was arranged : 



A glass apparatus of the shape represented in fig. 3 was constructed. 

 The part marked C is a fine capillary drawn .,.,_ 



out tube some 5 or 6 inches in length, the B 

 portion, about 2 inches long, being filled 



with hard-pressed purified asbestos. The 



radium salt was located at A, and the whole 



was most carefully heated, exhausted to the 



limit of the mercurial pump, and sealed off. 



In the dark no trace of phosphorescence could 



be seen in any part of the apparatus unless 



from the pieces of the radium bromide. The 



fine tube C was now immersed in liquid air in 



a large flask, so that distillation might pro- 

 ceed undisturbed for days. After 24 hours 



of this operation, on looking at the part C 



while covered with the liquid air, a marked 



phosphorescence was recognisable owing to 



some condensed emanation. The luminosity 



became naturally more marked the longer the 



time the action was allowed to proceed, and 



it is our intention to continue the experiments 



for a lengthened period of time, and then 



seal off the fine capillary part so that the con- 

 densed product may be thoroughly examined. 



