UNDER THE INFLUENCE OF CHEMICAL ACTION. 
15 
clear indication of a change in the contact potential difference between the surfaces 
taking place during the course of a single set of observations. 
§ 3.— The Characteristic Curves for Chlorine. 
The manipulation in the case of chlorine was very similar to that in the case of COCl 2 
and the results are of the same general character. Two typical characteristics as 
actually determined are shown in fig. 6. The curves show a flat saturation part for 
accelerating voltages exceeding about four. There is the same tendency to haphazard 
displacements of the curves parallel to the voltage axis as in the case of C0C1 2 . 
The magnitude of this displacement seems, however, to tend to be smaller with 
chlorine, the maximum separation I have observed in six characteristics taken 
with this gas being 0 *95 volt. The fact that the two curves shown in fig. 6 
do not appear to be parallel is due to the distortion caused by the different vertical 
scales. The standard current has the arbitrary value 1 -09 in one case and 0 -95 in 
the other. 
As in the case of C0C1 2 , the various series have been reduced to unit saturation current 
and displaced by varying amounts along the vertical axis to form a composite curve. 
The various data referring to the relevant experimental series are given in the following 
table and remarks :— 
