Chemistry. — “Catalysis. IX. Thermal and photochemical reactions” 
By Nit Ratan Duar. (Communicated by Prof. Ernst COHEN). 
(Communicated at the meeting of September 25, 1920). 
In a foregoing paper (Duar, Trans. Chem. Soc. 1917 111, 707) 
it was shown that the temperature coefficient of the oxidation of 
potassium oxalate by iodine has the value 7.2 for a 10° rise in the 
dark and this reaction is extremely sensitive to light. 
It occurred to me that all reactions which have high temperature 
coefficients should be sensitive to light. 
[ have shown previously that most uni-molecular reactions have 
high temperature coefficients and | investigated the effect of tropical 
sunlight on several of these reactions, and the following results were 
obtained. 
Ammonium nitrite decomposes fairly readily at about 33° in 
sunlight, whilst at 33° in the dark there is hardly any decomposition. 
The temperature coefficient for a 10° rise in the dark is about 4.5 
(ARNDT, Zeit. Phys. Chem. 1901, 39, 64). 
The intramolecular transformation of acetyl chloranilide to para- 
chloracetanilide has the temperature coefficient 3.2 in the dark. 
(Riverr, Zeit. Phys. Chem. 1913, 82, 201) and Branxsma (Ree. trav. 
Pays. 1903, 22, 290) has shown that the change is sensitive to light. 
Similarly the pseudo-unimolecular reactions, the hydrolysis of 
cane sugar and the decomposition of potassium persulphate, are highly 
influenced by light. An aqueous solution of cane sugar when exposed 
for several days to tropical sunlight, becomes converted into the 
invert sugars. 
Green and Masson (Trans. Chem. Soc. 1910, 97, 2083) have 
shown that potassium persulphate is slowly decomposed by water 
according to the following equation 
KS: Od HO oe ASO): 
This reaction has the temperature coefficient 5 in the dark. I found 
that the reaction is very sensitive to light and the oxygen given off 
in 24 hours in sunlight is practically equal to that produced in 
about 15 days in the dark at 27°. 
The decompositions of the sulfine bases and the tetraammonium 
compounds studied by Von Hasan have high temperature coefficients 
