Gases hy the Alpha Particles from Polonium. 577 



the total area under this theoretical curve is a measure o£ 

 Ihe total ionization produced by the alpha particle in the gas. 

 If A t represents the area under the theoretical curve, then 



Jo t. o v lL ) 



= 3/2 c(V) 2 / 3 = 7-33 c 



(/• being equal to 10*8 centimetres). 



Hence c is 3/22 of the area under the theoretical curve 

 when the average range of the alpha particle is 10*8 centi- 

 metres in any gas whatever. The values of c recorded in 

 column 2 of Table I. are then 3/22 of the area under the 

 theoretical ionization curves in the respective gases. 



The areas under the ionization curves being proportional 

 to the energies consumed in the production of ions in the 

 respective gases, the value of c in any one gas depends upon 

 the total ionization produced in the gas, and consequently 

 upon the energy required to produce an ion in the gas. 

 Then the ratio of the area under the experimental curve to c 

 should be a constant. By dividing the areas under the 

 experimental curves as measured with a planimeter and 

 recorded 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 are:is 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 ionization 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 raiio of the total ionization in the substance to the total 

 * Br.agg, v Phil, Mag. vol. xiii. pp. 333-357, -March 1007. 



