1335 
It will be seen that in all these cases in presence of light the 
Chemical change is much more rapid tlian in darkness and so we 
see that light acts as a positive cataijst in all these reactions. 
üp till now practically there was no instance known in which 
light was said to have any influence on the aciion of free iodine 
on a reducing agent. Thus Luther and Plotnikoef i^Zeit. Phys. Chem. 
61 , 524 (1907)) have shown that the action of iodine on phosphor- 
ous acid is un-influenced bj’ light. 
In the present investigation it has been proved that light has much 
influence on a number of oxidations by iodine. Thus it has been 
found that oxalic acid and oxalates are acted upon by iodine much 
more rapidly in light than in darkness. 
The action of iodine on the free acid is rather slow but the action 
on oxalates is fairly rapid. Hence a closer stiidy was undertaken 
and it has been found out that the action of iodine on ammonium 
oxalate is quite regular. Thus a dozen observations were made in 
the month of March under exactly similar conditions and concordaat 
readings were obtained. 
As usual two 100 c.c. stoppered bottles were taken and 50 c.c. 
N N 
— ammonium oxalate and 5 c.c. — iodine were taken in each of 
5 10 
At 30°. 
No of observation 
Time of | 
exposure 
Amount of 
iodine added 
in grams 
Unchanged 
iodine 
( 
1 Light 
60' 
j 0.0635 
1 
0.00012 
1) ' 
1 
^ Darkness 
60' 
i Do 
0.05178 
1 
1 Light 
60' 
' Do 
0.00011 
2) 
i 
1 
' Darkness 
60' 
Do 
0.05175 
3) j 
1 Light 
60' 
Do 
0.00012 
[ Darkness 
60' 
Do 
0.05169 
4) j 
1 Light 
60' 
Do 
0.00012 
! Darkness 
60' 
Do 
0.05182 
5, j 
1 Light 
60' 
Do 
0.00011 
1 Darkness 
60' 
Do 
0.05179 
6) 1 
1 Light 
60' 
Do 
0.00012 
1 Darkness 
60' 
Do 
0.05175 
