Radium Emanation at Low Temperatures. 



961 



contamination by the first sweeping through of uu condensed 

 emanation. With still smaller quantities of emanation this 

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noticed, for then there is not so much uncondensed emanation 

 to contaminate the electroscope. With larger quantities o£ 

 emanation the rise o£ ionization to a maximum appears all 

 the more sudden, because the amounts of emanation vola- 

 tilizing at the lower temperatures are relatively much smaller 

 than the amounts at the temperatures corresponding to 

 maximum ionization. 



Experiments by another method will be described in a later 

 paper showing that a gradual and continuous volatilization 

 can be detected from —180° C. upwards. The fact that the 

 maximum ordinates of curves I. and II. do not fall at the 

 same temperature is explained later. 



The results of a number of experiments, using spirals of 

 the materials named and of diameter of tube 0*35 cm., are 

 given in the following tables. In these experiments, attempts 



