726' Mr. A. S. Eve on the Amount of Radium Emanation 



piece. Rubber tubing connected the side opening of the 

 filter flask to a bulb containg phosphoric pentoxide ; and 

 between this and a three-way tap was a capillary tube, useful 

 in preventing any violent inrush of air, which would destroy 

 the gold-leaf. The three-way tap led to the water-pump, and 

 to the vessel containing the gas to be introduced into the 

 electroscope. 



The first series of observations made with a single tube of 

 charcoal gave uncertain results, and some of the charcoal 

 contained a small quantity of radium. Fresh coconuts 

 were procured, and charcoal was prepared free from radium. 

 The whole of the work was done in the Chemistry Building, 

 which has been kept free from contamination by strong radio- 

 active preparations. The air tested was obtained from out- 

 side, drawn through clean glass tubes passing through a hole 

 in the window-frame. A manometer was used to test the 

 velocity of the air- currents employed. This was calibrated 

 by the help of an air-tight iron boiler, one-tenth of a cubic 

 metre in volume, which could be exhausted by the water- 

 pump. 



Three glass tubes, each 1*2 cm. in diameter, containing 

 7 grams of charcoal, were placed in parallel, so that the air- 

 current was divided. A comparison was made between the 

 emanation obtained from the tubes (1) after the air-current 

 had run for the number of days specified, (2) after the tubes 

 had rested. The experiments were made in February and 

 March, under winter conditions, in Canada. The results are 

 given in scale-divisions of the observing microscope per 

 minute. The natural leak of the electroscope was, and still 

 is, '065 division a minute. 



No. of days. Eun. Rest. 



8 -147 



7 -10 



4 -136 



3 -095 



3 '118 



3 -085 



3 *10 



3 ... -084 



4 ., -11 



3 ... -083 



The average speed of the air-current was about 3' 7 cm./sec. 

 A solution containing 10~ 10 gram of radium was then placed 

 in a flask, and the emanation from it carried for three days 

 at the same speed as before through the carbon tubes. These, 



