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THE ROYAL SOCIETY OF CANADA 



constant. An aspirator bottle B (Figs. 1 and 2) filled with warm 

 distilled water (50-60°C), was connected to the higher end of M. 

 A tube I closed by a clip penetrated the bung and reached nearly to 

 the bottom of P, when it was sure that all the joints were air tight 

 and the sample was boiled. After half an hour's boiling the tap 

 to B and the clip I were opened and as the water in B ran out a vigorous 

 stream of air was drawn through the boiling solution and all the eman- 

 ation expelled by the boiling was collected in the air which now fills B. 

 Two aspirator bottles of volume about two litres were filled with air 

 in this manner. This ensures a complete sweeping out of the expelled 



^^^ 



Fig. 2 



emanation. Meanwhile the insulated system of the electroscope 

 and ionisation vessel was charged to the usual potential and obser- 

 vations^ of the normal rate of discharge or "air leak" made. 



When the air has been in the vessel ten minutes observations of 

 the leak are taken. 



Most experimenters in carrying out similar determinations allow 

 the gas to stay in the ionisation vessel three hours before taking 

 readings of the rate of leak of the charged gold leaf. It is known that 



^ A delay of 10 minutes or so was always made after charging before measure- 

 ments of the steady value of the "air leak" were taken. This is on account of absorp- 

 tion of the charge by the insulation. The ionization vessel is exhausted to a pressure 

 of about one centimetre of mercury and the air in the aspirators is allowed to pass in 

 through a drying tube containing calcium chloride. (See fig. 1). 



