EXPERIMENTS IN RADIO-ACTIVITY AND THE PRODUC- 

 TION OF HELIUM FROM RADIUM/' 



Bv Sir William Ramsay and Mr. Frederick Soddy. 



(1) EXPERIMENTS ON THE RADIO-ACTIVITY OP THE INERT GASES OP THE 



ATMOSPHERE. 



Of recent years many investigations have been made }\v Elster and 

 Geitel, Wilson, Strutt, Rutherford, Cooke, Allen, and others on the 

 spontaneous ionization of the gases of the atmosphere and on the 

 excited radio-activity obtainable from it. It became of interest to 

 ascertain whether the inert monatomic gases of the atmosphere bear 

 any share in these phenomena. For this purpose a small electroscope 

 contained in a glass tube of about 20 cubic centimeters capacity, cov- 

 ered in the interior with tin foil, was employed. After charging, the 

 apparatus if exhausted retained its charge for thirty-six hours without 

 diminution. Admission of air caused a slow discharge. In similar 

 experiments with helium, neon, argon, krypton, and xenon, the last 

 mixed with oxygen, the rate of discharge was proportional to the 

 density and pressure of the gas. This shows that the gases have no 

 special radio-activity of their own, and accords with the explanation 

 alread}^ advanced by these investigators, that the discharging power 

 of the air is caused by extraneous radio-activity. 



Experiments were also made with the dregs left after liquetied air 

 had nearly entirely evaporated, and again with the same result; no 

 increase in discharging power is produced by concentration of a possi- 

 ble radio-active constituent of the atmosphere. 



(2) EXPERIMENTS ON THE NATURE OP THE RADIO-ACTIVE EMANATION FROM 



RADIUM. 



The word emanation, originally used by Boyle ('\substantial emana- 

 tions from the celiNstial bodies'"), was resuscitated by Rutherford to 

 designate definite substances of a gaseous nature continuously pro- 

 duced from other sul)stances. The term was also used by Ru.ssell 

 ("emanation from hydrogen peroxide") in much the same sense. If 



« By Sir William Ramsay, K. C. B., F. R. S., and Mr. Frederick Soddy. Received 

 at the Royal Society July 28. Reprinted from Nature, London, August 13, 1903, No. 

 1763, vol. 68, pp. 354, 355. 



203 



