48 S. J. Plimpton — Recombination of Ions 



the ordinates electrometer readings in scale divisions. It will 

 be seen that each curve beginning at the left has a marked 

 curvature but eventually becomes a straight line and that these 

 two straight lines, if produced, will intersect the vertical axis 

 in a common point. 



From this it is concluded that the air curve OAB is the sum 

 of two curves, OCD and OE, where OE is parallel to PB and 

 OCD approaches a line through PD parallel to the pressure 

 axis. In a similar way the curve OFG is the sum of the curves 

 OJ parallel to PG and OHD which also approaches PD. Curves 

 OE and OJ are due to ionization produced by the Rontgen 

 rays in the gas, and the curves OCD and OHD are due mainly 

 to corpuscular radiation from the plates, which is completely 

 absorbed at a definite pressure. After replacing the lead 

 screens MM' and NN"' so as to confine the X-rays between the 

 electrodes A and B, the series of readings was repeated and 

 found to give the straight lines OE and O J. Throughout the 

 rest of the investigation the rays were restricted between the 

 electrodes so as to avoid corpuscular radiation. 



Experimental Results. 



There is reason to believe that certain peculiar conditions 

 are present in the initial stages of recombination. On this 

 account it was thought advisable not to use formula (2) which 

 involves the number of ions initially present, but to modify 

 the formula in the following manner : 



a = 



(i) 



dt 



In this way the determinations of a are rendered independent 

 of the initial conditions. 



In fig. 5 the reciprocals of the deflections are plotted for the 

 various time intervals. The slope of these curves should be 

 proportional to a. 



For short intervals of time, however, there is a marked cur- 

 vature indicating that a is relatively large for the initial stages 

 of recombination, but diminishes, becoming in most cases 

 nearly constant for (t) greater than about one-third of a second. 

 The curve for air is nearly straight at the end. In the case of 

 carbon dioxide the curve is surprisingly steep at the end, indi- 

 cating a very large value of a as compared with air, and one 

 would suppose that it must ultimately become more nearly 

 horizontal. It was, therefore, desirable to further extend the 

 curve for air and carbon dioxide. In order to do this, the 

 pendulum was arranged to operate the keys on the return 



