680 Hon. R. J. Strutt on Radioactivity 



oxidizing nitrogen upon a large scale * the mixed gases were 

 absorbed at the rate of 20 litres per hour. 



In the alternative method the nitrogen is absorbed by 

 magnesium or preferably by calcium formed in situ by heating 

 a mixture of lime and magnesium as proposed by Maquenne f. 

 In this case it is necessary first to remove the oxygen ; but 

 oxygen is so much more easily dealt with than nitrogen that 

 its presence, even in large proportion, is scarcely an objection. 

 On this view, and on the supposition that liquid air is 

 available in large quantities, it is advantageous to allow the eva- 

 poration to proceed to great lengths. A 20 per cent, mixture 

 of argon and nitrogen (experiment 5) is easily obtained. 

 Prof. Dewar has shown me a note of an experiment executed in 

 1899, in which a mixture of argon and nitrogen was obtained 

 containing 25 per cent, of the former. In the 6th experiment 

 33 per cent, was reached, and there is no theoretical limit. 



P.S. — I see that Sir W. Ramsay (Proc. Roy. Soc. 

 March 1903) alludes to an experiment in which the argon 

 content was doubled by starting from liquid air. 



LXXIV. Radioactivity of Ordinary Materials. By the Hon. 

 R. J. Strutt, Fellow of Trinity College, Cambridge %. 



IT is now well recognized that the air in any ordinary 

 vessel possesses the power of conducting electricity, 

 under electromotive forces insufficient to produce luminous 

 discharge, although only to a very slight extent. It has 

 been usual to refer to this effect as the " spontaneous ioniza- 

 tion " of the air. This name suggests that the conductivity 

 is in some way an essential property of the air, just as the 

 electrical conductivity of metals is inseparably connected with 

 the nature of those bodies. 



Mr. C. T. R. Wilson, however, has found (Proc. Roy. Soc. 

 vol. lxix. p. 277) that when other gases ara substituted for 

 air, the relative ionizations are in nearly the same ratio as 

 those which I observed (Phil. Trans. 1901, p. 507) for the 

 same gases under the action of Becquerel radiation. Further, 

 Mr. J. Patterson has found (Proc. Camb. Phil. Soc. xii. p. 44) 



* Chem. Soc. Journ. lxxi. p. 181 (1897) ; Scientific Papers, yol. iv. p. 270. 



t I employed this method successfully in a lecture before the Royal 

 Institution in April 1895 (Scientific Papers, vol. iv. p. 188). In a 

 subsequent use of it I experienced a disagreeable explosion, presumably on 

 account of the lime being iusufBciently freed from combined water. 



\ Communicated by the Author. Part of the above was published in 

 ' Nature,' Feb. 19, 1903. It appeared afterwards that some of the results 

 had been anticipated by Prof. MacLennan and also by Prof. Rutherford 

 and Mr. Cook, in papers read before the American Physical Society in 

 Dec. 1902, although no account of their experiments had then appeared in 

 print. I have thought it best to confine myself to the description of my 

 own results, so as to give an independent view of the subject. 



