﻿Motion of Electrons in Argon and in Hydrogen. 1041 



Two quantities of argon were thus prepared, one having 

 had the traces of nitrogen removed by sparking for 120 hours 

 and the other for 70 hours. These specimens of argon will 

 be referred to as the first and second respectively. 



The velocities n and W were determined with both 

 specimens over large ranges of electric forces and pressures. 

 With the smaller pressures from 2 to 30 millimetres, where 

 Z/p is large there was not much difference between the two 

 specimens, but with the largt r pressures from 30 to 150 

 millimetres, where the range of the ratio Z/p was from 

 •1 to 8, there was a considerable difference. With these 

 values of the ratio Z/p the velocities of agitation were greater, 

 and the velocities in the direction of the electric force were 

 smaller, in the first specimen than in the second. These 

 results indicate the presence of a small trace of impurity in 

 the second specimen. From our previous experiments we 

 found that the loss of energy of an electron in a collision 

 with a molecule of argon is much less than in a collision with 

 a molecule of nitrogen or of any other impurity that the 

 gas might be likely to contain. Small traces of impurities 

 have therefore the effect of reducing the velocit}^ of agitation 

 of the electrons, with the result that the velocities in the 

 direction of the electric force are increased. 



8. The following table gives examples of the experiments 

 made with the first specimen of argon. The pressures p of 

 the gas are given in millimetres of mercury, the electric 

 force Z in volts per centimetre, and the velocity in the 

 direction of the electric force W in cm. per sec. The 

 quantity k is the factor by which the energy of agitation 

 of an electron exceeds the energy of a molecule of a gas 

 at l. r )°C. 



The velocities W and the factors k for electrons moving 

 in argon and in hydrogen may be compared by the curves 

 in figs. 4, 5, and 6. 



The curves (fig. 4) give the velocities W in argon and in 

 hydrogen corresponding to the lower values of the ratio Z/p 

 from *1 to 2. The velocities corresponding to the larger 

 values of Z/p are given in fig. 5 for argon, hydrogen, and 

 a mixture of hydrogen and argon in the proportion by 

 pressure of one of hydrogen to 24 of argon. In the ratio 

 Z/p for the mixture, p is the partial pressure of the 

 hydrogen. 



The values of k are given in fig. 6. There are tw T o curves 

 for each gas, the lower curves I giving k for the smaller 

 values of Z/p from '06 to 1*6, as indicated by the scale at the 

 foot of the diagram, and the upper curves II for the larger 



