1108 
It will be seen that in all these cases in presence of light the 
chemical change is much more rapid than in darkness and so we 
see that light acts as a positive catalyst in all these reactions. 
Up till now practically there was no instance known in which 
light was said to have any influence on the action of free iodine 
on a reducing agent. Thus Lurner and Prornikorr (Zeit. Phys. Chem. 
61, 524 (1907)) have shown that the action of iodine on phosphor- 
ous acid is un-influenced by light. 
In the present investigation it has been proved that light has much 
influence on a number of oxidations by iodine. Thus it bas 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 study 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 concordant 
readings were obtained. 
As usual two 100 c¢.c. stoppered bottles were taken and 50 c.ec. 
N : INR ZE 
_ ammonium oxalate and 5 cc. Ti iodine were taken in each of 
5 
At 30°. 
No of observation | See one aed Uncraneed 
! ] 
Light | 6 0.0685 —-0, 00012 
2 ae 60’ Do 0.05178 
Light 60’ Do 0.00011 
2 | Darkness 60’ Do 0.05175 
Light 60’ Do 0.00012 
4 | Darkness 60’ Do 0.05169 
Light 60’ Do 0.00012 
ni | Darkness 60’ Do 0.05182 
Light 60’ Do 0.00011 
2 eu 60’ Do 0.05179 
Light 60’ Do 0.00012 
5 | Darkness | 60’ Do 0.05175 
