Recombination of Ions in Gases. 



219 



The reason for the insertion of the last curve will be given 

 later. 



The other points in the diagram are Langevin's experi- 

 mentally found values of e. Those for air are shown thus : 

 X , and those for carbon-dioxide, thus : o. In order to 

 compare the results, the scale of the abscissae has been chosen 

 so as to make the observed values coincide as nearly as pos- 

 sible with the curve C ( = c 3 ). The pressures corresponding 

 to any point are therefore different for the two gases ; for 

 the air points, x , they are obtained from the abscissa? by the 

 relation p(mms.) = 691 x, for the carbon- dioxide points, o, 

 they are given by p(mms.) = 438 x. 



In the case of air the experimental points all appear to be 

 sufficiently close to the curve C or y — c^ but a slight devia- 

 tion from the curve can be detected at the two lowest 

 pressures. The agreement with the curve 



2/ = c 4 + -75(c 3 -c 4 ) + -17(c 2 -c 3 ) 



seems to be exact, or at any rate within the experimental 

 error, as the following numbers testify : — 



1 



p mms. 



Values of e. 



Experimental. 



Calculated. 



152 



375 



760 



1550 



2320 



380l» 



•01 

 •06 



•27 

 •62 

 •80 

 •90 



:009 

 '072 

 •27 

 •62 

 •80 

 ■90 



The values for carbon-dioxide do not seem to be capable of 

 being represented by the formula with the same degree of 

 accuracy as those for air. If the scale of x is adjusted so 

 that observations at low pressures come nearly on to the 

 curve C, then the values at high pressures deviate considerably, 

 the last but one being as much as 20 per cent, too high. It 

 looks as though the experimental values were too large — 

 there would be a tendency this way in the case of a strongly 

 absorbing gas-like carbon-dioxide at high pressures, when 

 the ionization would be large — although it is possible that 

 there is some inherent complication in this case, of which 

 the theory does not take account. 



