236 Research Staff of the G. E. C, London, on the 



proportional to the number of ions present and, within 

 limits, to the pressure ; if (3) is correct it would vary with 

 the number of ions and with the pressure. 



7. Accordingly, experiments were made to determine how 

 the absorption varies with the positive ionization, under the 

 provisional assumption that i g is a measure of the positive 

 ionization, when V' is such that i g is a maximum. A triode- 

 with cylindrical electrodes was first used, which will be 

 termed vessel 2. A gauze grid surrounded the single loop 

 filament which formed the cathode, and was surrounded in 

 its turn by a cylindrical anode. The length of the loop and 

 the anode were 1*5 cm., the diameters of the grid and anode 

 cylinders 1*2 and 3*5 cm. The electrodes were contained in 

 a nearly spherical bulb 7*5 cm. in diameter. The vessel was 

 connected through a liquid-air trap to pump, gauge, and 

 filling arrangements. The volume, r, in which absorption 

 took place, was measured by Boyle's law, and thus uncer- 

 tainty was avoided concerning the temperature of the trap 

 and bulb ; it was about 750 c.c. Measurements of the 

 pressure, p, and the time gave the rate of absorption. The 

 first experiments showed that, when p w 7 as the same, — p, the- 

 rate of decrease of pressure, was very approximately pro- 

 portional to ig, when this was varied either by changing V 

 or by changing the cathode temperature. (V was always- 

 made such that ig was a maximum.) It thus appeared that 

 of the alternatives given only (2) was tenable, and that the- 

 reaction producing C0 2 (which disappeared in the cooled 

 trap) must be one between a positive ion and a neutral 

 molecule. 



For the expression of the further results, the quantity a. 

 will be used, suggested by Faraday's electrolytic law. a is 

 the number of molecules disappearing when one electronic 

 charge (carried by a positive ion) arrives at the grid. If JST 

 is the number of molecules in 1 c.c. of gas at N.T.P., and if 

 v is reduced to N.T., then 



« = -£-•"• 760 (1) 



If ig is measured in milliamps., volume in c.c, and time in 

 seconds, Ne = 4300, and 



a==5-65. v 



■(-£) w 



If assumption (2) is correct, if every ion undergoes the 

 reaction, and if the positive charge on the carrier remaining 

 after the reaction arrives at the grid, then » should be 2 ; for 



