88 
character. It might be expected that also a true proportionality would 
exist between the time of exposure and the amount of decomposed 
substance, if the initial concentrations were the same in all cases. 
However, experience only partially confirms this conclusion; at least 
we found, for instance, the following data in a series of experiments: 
rime of Ex- | ‚Corr. Weight o of Corr. Weight o of | | percentawe | 
Temper posure in | the Cobalti-Salt | the metallic Co.' of the Salt 
in °C. | minutes: in 50 ccm.: found: decomposed: 
| 
2392 0. 0803 Gr. 0. 0310 Gr. 26. 4 0/6 
23.9 0. 9017 0. 0357 33. 2 
24 0. 9902 0.0511 44,7 
| 
This divergence becomes somewhat intelligible if we remember 
that the medium is continually changing chemically and physically 
during the reaction; therefore, because it changes gradually as well 
in absorptive power as in concentration of the cobalti-salt or potas- 
sium-oxalate, the action of the light in 60 minutes e.g., can not be 
equivalent to twice the action in 30 minutes, ete. On the contrary, 
there is rather a cause for astonishment at the fact that the results 
of the first series of experiments were really so regular, while the 
initial concentrations in these experiments differed so appreciably 
from each other, and thus the same was true for the absorptive 
power of the solutions used. It may be, that the slight increase of 
the first four numbers mentioned above, finds its explanation also in 
this particular circumstance. 
§ 4. Afterwards the experiments described above were again 
repeated, and now a specially purified salt, free from all cobalto- 
ovalate was made use off. It was freshly prepared and immediately 
used in the experiments, in which a lamp of somewhat smaller 
intensity was applied as source of light. For the numbers obtained, 
see the table on the following page. 
From these measurements it appears that the speed of reaction is 
relatively greater with the smaller, than it is with the greater con- 
centrations; that also in the most favourable circumstances disturbing 
influences seem to play a rôle, which have as a consequence some 
uncertainties of the analysis; and that, at least with respect to the 
last four numbers, the total decomposition may be supposed as in- 
dependent of the original concentration. It must be remarked, that 
