18 Wellisch — Motion of Ions and Electrons through Gases, 



With regard to the nature of the sink which is gradually 

 formed in the vapor of petroleum ether, nothing at all definite 

 can be said. We may imagine that polymers or small aggre- 

 gates of pentane or hexane are formed gradually under the 

 influence of the radiation from the polonium ; such systems 

 would probably be able to form stable negative ions for large 

 electron velocities and unstable ions for small velocities. Initi- 

 ally, when the vapor is pure, the negative carriers are for the 

 most part electrons ; as the sinks appear, the velocity of the 

 electrons would be reduced through the formation of unstable 

 ions. The fact that ultimately the carriers consist entirely 

 of negative ions may be explained by ascribing to a polymer 

 the property of being able to effect occasionally a union between 

 an electron and a molecule of the vapor. 



(D) Ions in Gases and Vai^ors. 



Gases. — The law j?^'= const, was verified for both the posi- 

 tive and the negative ions in dry air over a wide range of 

 pressures. Some of the values obtained experimentally for K 

 at the lower pressures have been given in the previous paper 

 and should be sufficient to illustrate the unchanging nature of 

 the negative ion. A set of values obtained for the mobility of 

 the positive ion in air at low pressures is given below ; the first 

 table refers to values obtained by means of determinations of the 

 critical potential Y^, while the values given in the second table 



d^n i 

 were determined by means of the formula ^' = -=^ • - — r, • 



Press 



Vo 



/ 



Freq. 



h. 



K, 



mm. 



volts 











8-31 



53^0 



•546 



864-3 



119-5 



1-31 



1-66 



11-5 



•540 



834^2 



537-5 



1-17 



1-64 



10-2 



•540 



850-9 



618-0 



1-33* 



1-01 



6-0 



•574 



851-7 



989-0 



r3i 



•563 



3-0 



•574 



836-5 



1944 



1-44 



•410 



2-5 



•584 



862^1 



2363 



1-29 i 



•321 



1-75 



•585 



833-3 



3254 



1-37 1 



Mean value of Ki : 1*32 

 * a = 8 volts {v. fig. 2) ; for the otlier determinations a — 20. 



