ia Particles from Polonium. 



curves as measured with a planimeter and l'ecorded in column 

 3, Table I, by the values of c for the corresponding gases, 

 the values recorded in column 4 were obtained and, as can be 

 seen, are approximately constant. 



The areas under the ionization curves being the measures of 

 the relative ionizations produced in the gases, the ratios of the 

 total ionization produced in the gases to that produced in air 

 were determined by finding the ratio under each curve to the 

 area under the corresponding comparison air curve. After 

 the determination of the ionization curve in each gas, the ioni- 

 zation curve was always obtained in air to be used as a basis of 

 comparison. The ratios of the ionizations produced in the 

 different gases to that produced in air are recorded in column 

 5 of Table I. Bragg,* by a less direct process, determined the 

 ratio of the total ionizations in gases to that in air and his values 

 are recorded in column 6. There is a fairly good agreement 

 between the values as found by Bragg and those found by a 

 more direct process of measurement of the area enclosed by 

 the axes of references and the ionization curve for each gas. 



Since the energy of the alpha particle is entirely consumed 

 before it ceases to produce ions, the energy required to pro- 

 duce an ion in any given substance will vary inversely as the 

 ratio of the total ionization in the substance to the total ioniza- 

 tion in air if the energy required to produce an ion in air is 

 always taken as the basis of comparison. The values of col- 

 umn 5 of the table are the ratios of the total ionizations pro- 

 duced 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 pro- 

 duce anion in air. The values recorded in column 7 are these 

 reciprocals of the values in column 5, and hence are the rela- 

 tive 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 molecules being in a less 

 stable arrangement than they are in the lighter and less com- 

 plex molecules and hence more readily drawn out. 



In conclusion, I wish to express my thanks to Professor 

 Bumstead for his valuable suggestions in connection with the 

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

 to Professor Boltwood for furnishing me the preparation of 

 polonium. 



* Bragg, Phil. Mag., vol. xiii, pp. 333-357, March, 1907. 



