[satterly] natural GASES OF CANADA 155 



"leak" is first observed when the vessel is filled with pure dry air. 

 If now the vessel is filled with dry air containing radium emanation 

 the increase of leak is taken as a measure of the radium emanation 

 present. If the emanation is in some gas other than air the pro- 

 cedure is much the same. A measured quantity of gas is introduced 

 by an aspirator system into the vessel — it may be enough to fill the 

 vessel or the balance may be made up with air — and the leak found 

 as before. A correction may be necessary on account of the effect 

 of the gas on the current produced by the emanation. This will be 

 taken up later. A more important effect is caused by the changes 

 which radium emanation undergoes and produces. On account of 

 the decay of the emanation and the production of the successive 

 products of disintegration on the sides of the vessel the leak varies 

 with time. It increases for three hours and then diminishes. For 

 purposes of comparison the leaks should always be taken at the 

 same interval after filling the vessel with the gas. The leak taken 

 about ten minutes after filling is usually the best to observe.^ In 

 some cases the leak was also taken after the three hour interval. The 

 ratio of these two leaks serves as a sure identification of the active 

 substance and as a test of the accuracy of the work. In all cases 

 of course the "air" leak must be deducted from the measured leak to 

 get the leak due to the emanation. 



The Radium Solutions. In order to express the emanation 

 content in terms of radium a standard solution must be employed. 

 The one used came from the Bureau of Standards at Washington 

 and contained 1-22x10"' gm. radium. To extract the emanation 

 from the solution the latter is boiled in a closed flask. Air is then 

 rapidly drawn through the solution into an aspirator. This sweeps 

 out all the emanation. The emanation-charged air is then sent into 

 the ionisation vessel and the leak read. 



By comparison the quantity of radium emanation in the gas 

 sample can then be expressed in terms of the quantity of radium 

 with which it would be in equilibrium. 



Effect of the Nature of the Gas on the Leak Produced by a Given 

 Quantity of Radium Emanation. In order to find the relative ionis- 

 ations produced by a given quantity of radium emanation in 

 dry air and in natural gas of known composition, experiments were 

 performed in which the emanation was swept out of the solution with 

 the gas in question instead of air. In one particular case the gas 

 from the Calgary Pipe Line was used. This contains 91-3% of 

 methane and other hydrocarbons, 8 • 5% of nitrogen and • 2% of oxygen 



iSatterly. Phil. Mag., Oct., 1908. 



