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THE ROYAL SOCIETY OF CANADA 



numbers plotted the uraninite was reduced to the same uranium basis 

 as the carnotite. 



The fact that the temperature coefficient of the emanating power 

 was so much decreased by a previous heating of the mineral was 

 suggestive. It was thought possible that by a more drastic treatment 

 of this sort a product might be produced whose emanating power 

 would have a very small and permanent temperature coefficient. 

 Two grams of the carnotite were heated to a temperature of approxi- 

 mately 400°C in a crucible for half an hour and the material was 

 sealed up as described. The emanating power at 18°C was reduced by 

 this treatment from 16.2 per cent, to 5.4 per cent. Curve 3 graphically 

 indicates the result of a series of measurements made for this tube and 

 shows that the temperature coefficient has been reduced to a very small 

 value. To find how the emanating power of this tube was affected 

 by increasing the humidity of the air contained in it, a tube filled with 

 cotton wool was attached to one end of the emanation tube and air 

 was sucked over the wet wool through the emanation tube for about 

 five minutes. The latter was then sealed and measurements of the 

 activity of the evolved emanation, made at the end of a few days, 

 showed that the emanating power was increased by 15 per cent. 

 However, if the air which enters the emanation tube is always passed 

 through the ammonium nitrate tube, any variations in the emanating 

 power due to the moisture effect Avere found to be eliminated. The 

 following determinations of the equilibrium amount of emanation 

 evolved by eight grams of this material which has been strongly 

 heated indicate its constancy over considerable ranges of laboratory 

 temperature. 



By treating the uraninite in the same manner, similar results 

 were obtained. This shows that by heating the minerals for a short 

 time to a temperature above 400°C the temperature coefficient of the 

 emanating power is reduced to such a small \'alue that for ordinary 

 ranges of laboratory temperature it may be neglected. Therefore if 

 the equilibrium amount of emanation evolved from a tube of carnotite, 



