552 Rate of Transformation of the Radium Emanation. 



two vessels were separated at B, care being taken to protect 

 the other parts o£ the vessels from radiation from the flame. 

 The air in the smaller vessel V 1 was now transported into 

 the electroscope. The arrangement used is shown in fig. 2. 



Fig.2. 



TO PUMP 



-Tin 



/\ 



By means of rubber tubing, connexions were made to allow 

 a current of steam to pass through V x into a receiving- 

 vessel R containing water, after the narrow ends of the vessel 

 had been opened inside the rubber connexions. The steam 

 was passed through the vessel for some time, in order to 

 completely transfer the emanation into the gasometer R. 

 The electroscope was then exhausted and the collected gas 

 in R allowed to pass in through a tube B containing phos- 

 phorus pentoxide and plugs of cotton-wool. Air was then 

 introduced by means of a stopcock at A, which swept the 

 residual emanation in the tube into the electroscope, and 

 brought the air in the latter to atmospheric pressure. 



Immediately before the introduction of emanation the 

 natural leak was determined and the leak due to the radium 

 standard. The sensibility of the electroscope used was such 

 that 10~ 8 gram radium in equilibrium gave about 8 divisions 

 per minute movement of the gold-leaf on the scale of the 

 reading microscope. The actually measured amounts of 

 radium emanation were in most cases 1*5-4 times larger. 



Three hours after the introduction of the emanation, the 

 readings were taken, and then the emanation removed. The 

 larger vessel V 2 was dealt with in exactly the samewaya suitable 

 time later. The volumes of the glass vessels were determined 

 before the emanation was introduced ; the uncertainty due 

 to the sealing off at B (fig. 1) was certainly less than 1/300 

 of the volume of the smaller vessel. 



