Scheikunde. — De Heer Eknst Cohen biedt eene raededeeling aan 
van den Heer Nil Ratan Dhar „Catalysis.YS.. Tkennal and 
photocheniica I reactions’ ’ . 
(Mede aangeboden door den Heer van Romburgh). 
In a foregoing paper (Dhar, Trans. Chem. Soc. 1917 111, 707) 
it Avas sliown that tlie temperatnre coëfficiënt of tlie oxidalion of 
potassinin oxalate bj iodine lias the value 7.2 for a 10° rise in the 
dark and this reaction is extremelj sensitive to light. 
It occnred to me that all reactions which iiave high temperatnre 
coefficients shonld be sensitive to light. 
I liave shown previously that most uni-molecular reactions have 
high temperatnre coefticients and I investigated the effect of tropical 
sunlight on several of these reactions, and the following resnits were 
obtained. 
Ammonium uitrite decomposes fairly readilj at abont 33° in 
snnlight, whilst at 33° in the dark, there is hardlj anj decomposition. 
The temperatnre coëfficiënt for a 10° rise in the dark is abont 4.5 
(Arndt, Zeit. Phys. Chem. 1901, 39, 64). 
The intramolecnlar transformation of acetjT chloranilide to para- 
chloracetanilide has the temperatnre coëfficiënt 3.2 in the dark. 
(Rivett, Zeit. Phys. Chem. 1913, 82 , 201' and Blanksma (Ree. trav. 
Pays. 1903, 22 , 290) has shown tliat the change is sensitive to light. 
Similaily the psendo-nnimolecnlar reactions, the hydrolysis of 
cane sngar and the decomposition of potassinin persnlphate are highly 
inflnenced by light. An aqneous solntion of cane sngar when exposed 
for several days to tropical snnlight, becomes converted into the 
invert sngars. 
Green and Masson (Trans. Chem. Soc. 1910, 97 , 2083) have 
shown that potassinin persnlphate is slowly decomposed by water 
according to the following equation 
K, ö = 2 KÜS O, + O. 
This reaction has the temperatnre coëfficiënt 5 in the dark. I fonnd 
that the reaction is very sensitive to light and the oxjgen given off 
in 24 honrs in snnlight is practical ly eqnal to that prodneed in 
abont 15 days in the dark at 27°. 
The decompositions of the snlfine bases and the tetraammoninm 
componnds stndied by Von Halban have high temperatnre coefficients 
