106 THE ROYAL SOCIETY OF CANADA 



in the air a large tube was prepared which contained a considerable 

 quantity of ammonium nitrate crystals held between plugs of cotton 

 wool. Preparatory to sealing up the tubes containing the minerals 

 air was drawn through the ammonium nitrate tube and then through 

 the tube containing the mineral. A fairly constant humidity of the 

 air in contact with the mineral could, therefore, be assured. 



The emanation tubes were sealed and kept at definite tempera- 

 tures for times varying from one to thirty days. Having partially 

 exhausted the electroscope the emanation tube was connected with it, 

 the tips broken and air was sucked through carrying with it into the 

 electroscope the emanation, which had accumulated in a known time 

 under the particular conditions. At the end of three hours the 

 activity of the emanation was determined. The activity determined 

 in this manner is a measure of the emanation which has accumulated 

 during the time and under the given conditions. Assuming that the 

 emanation continues to be evolved at the same rate for a prolonged 

 period then the maximum or equilibrium value which would be 

 ultimately attained is given by the expression 



where Iq is the equilibrium value and It is the value of the activity 

 measured. 



Results 



The value of the equilibrium quantity of emanation evolved 

 from the carnotite at different temperatures is shown graphically by 

 curve 1, the abscissae representing temperatures centigrade and the 

 ordinates divisions per minute movement of the gold-leaf. In this 

 case different tubes* were maintained at the definite temperatures for 

 periods of approximately twenty hours, and from the values of the 

 activity measured, the equilibrium quantity was calculated. It was 

 found that when the tubes were heated for more than twenty hours, 

 at the higher temperatures especially, the value of the equilibrium 

 quantity of emanation as calculated by the above expression was 

 smaller the longer the tube was heated. This means that the emana- 

 tion is evolved at a rate which depends on the time the tube has been 

 heated. The amount of emanation evolved was found to depend on 

 the previous history of the mineral as Kolowrat^ found to be the case. 

 If the tube was heated to a fairly high temperature and the emanation 



"•The activities of the different tubes of carnotit maintained at the same temper- 

 ature for the same length of time did not vary by more than 2 per cent, at the most, 

 which indicates that the material was quite homogeneous. 



