52 



S. J. Plimpton — ^Recombination of Ions 



way except that the electrometer electrode was insulated before 

 the field was applied, thus receiving an induced charge which 

 distorts the field. In this instance, therefore, a smaller read- 

 ing D" was obtained owing to the distortion of the field. The 

 corrected value of V was obtained by measuring the volume 

 subtended between the electrodes and multiplying this by the 



,. D' 

 ratio jy~. 



The following table gives the average values of — (where e 



is the charge carried by the electron) between the successive 

 pairs of points A, B, C, D, E of fig. 5. 



In the case of the gases air and carbon dioxide, the curves 

 were extended to a point F where t = 1*06 seconds. 



Absolute Values of a/e. 



Gas or Vapor Pressure 



Air 768 



" 411 



C0 2 ,. 760 



" 382 



S0 2 355 



" 100 



" 37 



CH 3 I 28 



C 2 H fi Cl 100 



C 2 H 5 Br 28 



(C 2 H 5 ) 2 0... 95 



A-B 



11540 

 7150 



10000 

 7500 



12500 

 4400 

 1560 

 3440 

 4100 

 2380 

 4400 



B-C 

 6100 

 4580 

 7100 

 6100 

 7640 

 3560 

 1270 

 2540 

 4070 

 2200 

 4070 



C-D 



4680 

 3280 

 6700 

 5610 

 5150 

 2900 

 1160 

 1240 

 2870 

 1850 

 3700 



D-E 

 4600 

 2820 

 6500 

 5310 

 4600 

 2830 

 1060 

 1170 

 2830 

 1440 

 3180 



E-F 

 3960 



4880 



Effect of a Field on the Ionization. 



In order to ascertain the effect of an impressed field upon 

 the ionization, a potential of sixteen volts was applied to the 

 gas during the flash of X-rays and removed immediately after 

 the cessation of the flash, the recombination then being 

 measured in the usual way. 



The result is shown in curve X of fig. 5 for the case of air 

 at 760 millimeters pressure. Comparing this with the corre- 

 sponding curve for air without the application of this field 

 during the flash, it will be seen that the final slope is not 

 changed noticeably, but that the initial slope is lessened. This 

 result is in accord with the explanation of initial recombination 

 given above. The positive and negative ions in the initial 

 pairs would be separated more widely by the field and the 

 probabilities of collisions between them would be reduced, 

 giving a lower value of a. 



