

Charges on Ions in Gases. 



207 



Pressure of Air 



Force in volts 



Intensity of 



NeXlO 10 . 



in mm. 



per cm. 



ionization. 



3 



1-45 



10 



1-23 



6 



•98 



8 



1-23 



6 



1-47 



16 



125 



6 



1-96 



13 



115 



6 



2-96 



17 



1-27 



12 



100 



8 



1-20 



12 



•98 



12 



1-20 



12 



1-46 



15 



1-25 



12 



275 



45 



1-26 



25* 



1-47 



33 



1-30 



25* 



300 



34 



1-29 



* At 25 mm. pressure a correction of about 10 per cent, for self-repulsion 

 has to be made which cannot be estimated very accurately. 



The order of accuracy to be expected from the theory is 

 not the same for all forces, so that a larger range of forces 

 was not used. The accuracy is highest for forces of about 

 2 volts per centimetre when N X £ = 1*23 X 10 10 . It would 

 be quite possible to alter the dimensions of the apparatus so 

 as to give good results for practically any forces, but that 

 was not considered necessary. 



With the same apparatus the mean of the values obtained 

 for positive ions was 2*4 x 10 10 , the ions being produced by 

 secondary rays from a very tarnished surface. When a 

 bright surface was used and the air ionized by non-penetrating 

 secondary rays the values of N X e were 1*26 x 10 10 and 

 1*24 x 10 10 for positive and negative ions respectively- 

 Afterwards by putting a thin layer of vaseline on the plate 

 from which the secondary rays are produced the numbers 

 found for positive and negative ions were 2*06 x 10 10 and 

 1-22 x 10 10 respectively. 



Subsequently these experiments were made with hydrogen 

 and carbonic acid, and the positive ions in these cases also 

 were found to give different values for N x e in the same 

 way, while with negative ions the same value of N x e was 

 always obtained as was found for air. 



It is not the nature of the gas obviously that determines 

 whether or not large values of N x e are obtained. The 

 principal factor that has to be considered appears to be the 

 kind of radiation that is used. The simplest explanation 

 being that positive ions with single charges are produced 

 when the rays consist of projected particles (which compose 

 the non-penetrating secondary Rontgen rays), and that posi- 

 tive ions with double charges are produced by the direct 

 action of the more penetrating secondary rays, which 



