UNDER TEIE INFLUENCE OF CHEMICAL ACTION. 
31 
Fig. 16 shows some similar data for COCl 2 , except that the photo-electric and chemical 
curves were not taken simultaneously. The photo-electric curves, with the mercury 
lines A 4046 to A 4077, were taken the day before the chemical data, and no doubt 
there was some alteration in the contact potential between the electrodes in the interval 
between the experiments. The chemical data shown by crosses are a replot of those 
similarly indicated in fig. 12. The photo-electric data, shown thus ©, are actual 
currents in scale divisions per minute, with a capacity of 0-01053 mfd. and an electro¬ 
meter sensitiveness of 1100 divisions per volt. The saturation current was 130 in the 
same units in these photo-electric experiments. These curves again show quite clearly 
the reality of the small currents with relatively large opposing voltages for the chemical 
emission. The actual data for fig. 16 are shown on the next page. 
The second, third and fourth rows in this table and the last but one refer to the chemical 
emission, the fifth, sixth and seventh and the last to the photo-electric. The corrections 
for the electrometer drift in the fourth and seventh rows have been reduced respectively 
to the same units as the corresponding deflections in the second and fifth. Assuming 
that the determinations are liable to errors of the same magnitude as this drift, an 
assumption which is certainly conservative, the small chemical current at + 0-12 volt 
should be reliable to within 30 per cent, and the errors in the others are comparatively 
trifling. The same test applied to the photo-electric data shows that the value at — 1-0 
should be correct to 16 per cent-., the value at — 0 -4 meaningless and the others reliable. 
With regard to the small electrometer deflections recorded in some of these experiments, 
it should be pointed out that these can be measured with considerable confidence when 
the large capacities employed are added to the instrument. The pressure during these 
chemical measurements varied between the limits of 0 -002 and 0 -004 mm., and during 
the photo-electric between 0 -.0015 and 0 -0025 mm. 
