1128 Abnormally long Free Paths of Electrons in Argon. 



at 5'1 millimetres pressure and argon at 20 millimetres 

 pressure. 



z. 



w A xio- 5 . 



w mX io- 5 . 



^Xl0-<\ 



w m xio-7. 



17 



21 



191 



5-15 



5-3 



8-5 



15-1 



14 



41 



42 



4-1 



10-9 



102 



3-2 



3-1 



The addition o£ the argon to the hydrogen does not reduce 

 the velocity of agitation, under these conditions, by an 

 appreciable amount, as the figures in the last two columns 

 are the same within the limits of experimental errors. 

 The proportion in which the velocity in the direction of 

 the electric force is reduced, by adding the argon to the 

 hydrogen, is small, and diminishes with the force. 



Since the velocities u are not appreciably different in 

 the pure hydrogen and in the mixture, the ratio of the 

 mean free path l h in the hydrogen to the mean free path l m 

 in the mixture is l h /l m = ~Wk/Wm. The mean free path l a in 

 argon at 20 millimetres pressure in terms of 4 is obtained 

 from the relation l/l m =l/l h -t-l/l a . 



Taking the results of the experiments with a force of 

 8' 5 volts per centimetre it is seen that, with a velocity of 

 agitation of 4*2 x 10 7 cm. per second, the mean free path in 

 argon is about 60 times the mean free path in hydrogen at 

 the same pressure. 



For this velocity the mean free path, previously obtained, 

 in hydrogen at one millimetre pressure is 0*26 millimetre, 

 so that the mean free path in argon at one millimetre pressure 

 is about 15 millimetres, or fifty times the mean free path 

 deduced from the atomic radius which is obtained from the 

 viscosity. 



The experiments show that the reduction of the velocity W 

 in hydrogen by adding argon having four times the pressure 

 of the hydrogen, is too small to permit of an accurate deter- 

 mination of the mean free path in argon. 



We intend to make further experiments on this principle 

 using mixtures in which the pressure of the hydrogen is 

 about 5 per cent, of that of the argon, and to determine the 

 free paths for velocities of agitation much below 4*2 x 10 7 cm. 

 per second. 



