578 Ionization of Gases by Alpha Particles from Polonium. 



ionization in air if the energy required to produce an ion in 

 air is always taken as the basis of comparison. The values 

 of column 5 of the Table are the ratios of the total ionizations 

 produced in the gases as compared with the total ionization 

 produced in air. Consequently the reciprocals of these ratios 

 are the relative amounts of energy required to produce an 

 ion in the substance as compared with the energy required 

 to produce an ion in air. The values recorded in column 7 

 are these reciprocals of the values in column 5, and hence 

 are the relative amounts of energy required to produce an 

 ion in the gases as compared with that required to produce 

 an ion in air. These values indicate a considerable variation 

 of the energy required to produce an ion. The heavier and 

 more complex molecules are apparently more readily ionized 

 than the lighter and less complex ones. This is probably 

 due to the electrons in the heavier and more complex mole- 

 cules being in a less stable arrangement than they are in the 

 lighter and less complex molecules, and hence more readily 

 drawn out. 



In conclusion I wish to express my thanks to Professor 

 Bumstead for his valuable suggestions in connexion with 

 the work and for loaning me the apparatus. I am also 

 indebted to Professor Boltwood for furnishing me the 

 preparation of polonium. 



Results. 



1. The ionization curve obtained in various gases and 

 vapours with polonium as the source of rays is of the general 

 form 



c 



w 



(r— *)V»' 



here I is the ionization ; c is a constant for any one gas 

 depending upon the total ionization produced, and conse- 

 quently upon the energy required to produce an ion in the 

 given gas ; r is the average range of the alpha particles in 

 the cone of rays ; and x is the distance from the source of 

 rays. 



2. The agreement between the theoretical and the experi- 

 mental curves confirms the assumption made in previous 

 papers by the writer* and by Geigerf, that the ionization 

 produced by the alpha particle is proportional to the energy 

 consumed. 



3. The values of the ratio of the total ionization produced 

 by the alpha particle in different gases to the total ionization 



* Loc. cit. t Loc. cit. 



