1111 
2 Hg Cl, + (NH), C,0, = 2 He Cl + 2 CO, + 2 NH, CI. 
The above author has shown that the sensitiveness of Eprr’s 
actinometer may be increased eighty (80) times in absence of oxygen. 
Moreover, Rororr (Zeit. Phys. Chem. 18, 329 (1894)) has shown 
that carbon dioxide, which is one of the products of decomposition 
and consequently always present, largely increases the sensitiveness 
of the above form of actinometer. 
The lodine-Oxalate actinometer worked out in this investigation 
and which depends on the following reaction in presence of light 
I, + (NH,),C,O, = 2 CO, + 2 NH,I 
or 
I, + K,C,0, = 2 CO, + 2 KI 
is absolutely free from the disadvantages of the Eper Actinometer 
as has been proved by the foregoing tables that neither oxygen nor 
carbon dioxide has any influence on this actinometer. 
Moreover the estimation of iodine by standard sodium thiosulphate 
is decidedly simpler and easier than the estimation of mercurous 
chloride in the Eper Actinometer. Obviously the use of the iodine- 
oxalate actinometer is to be preferred. 
It has also been found out that iodine acts more rapidly in 
presence of light on other organic acids and their sodium salts than 
in the dark. 
The action of iodine on formates which takes place according to 
the following equation 
H.COONa + I, = Nal + HI + CO, 
is quite rapid as will be shown in the following table. 
Sodium formate and iodine. 
Time of | Amount of | Unchanged 
‚ exposure | iodine added iodine Volume of Solution 
Quality of light 
a) Sunlight | 154 0.0635 | 0.00103 40 c.c. Normal Sodium for- 
Darkness | 15/ Do 0.00295 en and 5 c.c. iodine. 
b) Sunlight 26’ Do 0.00116 20 c.c. Normal formate and 
Darkness rs 267 Do 0.00298 5 CC. x iodine. 
c) Diffused light | 40/ Do 0.00154 40 c.c. Normal Sodium for- 
Darkness 40/ Do 0.00225 mate and 5 c.c. 7 iodine. 
d) Diffused light | SOA Do 0.00142 40 c.c. Normal formate and 
pores | Gey ol Do 0.00224 | 10 cc. 2 iodine. 
| 
re 
12 
Proceedings Royal Acad. Amsterdam. Vol. XVIII. 
