J347 
Chem. Soc. 91 , (1907), 1641) lias again attacked tlie same reactioii 
and lias fouiid ont tliat the reaction is uiiimolecnlai- witli respect to 
hypophosphoroiis acid, biit it is cataljtically accelerated by liydrogen 
ions. Nobody has exarained the action of liglit on tliis reaction. 
It has now been fonnd ont tliat the action of iodine on the acid 
as well as its salts is catalytically accelerated by snnlight as will 
be evident from the following tables, tliough Lcther and Plotnikofe 
(Zeit. Phys. Chem. 61 , 524 (1907)) have shown tliat light is without 
any influence on the action of iodine on phosphorous aiud. (See p. 1346). 
Evidently light markedly accelerates the action of iodine on hypo- 
phosphorons acid as well as hypophosphites. Here light plays the 
same part as hydrogen ions do in these oxidations. 
D.wv.son and his papils (Trans. Chem. Soc. (1909), 95 , 1860; 
(1913) 103 , 2135) have shown that iodine acts slowly on an aqueoiis 
soliition of acetone and that the action is catalytically accelerated 
by hydrogen ions. According to the above authors the reaction takes 
place according to the following scherae 
I CH 3 COCH,;^ CH, : C(OHjCH 3 
II CH, : C fOH) CH. + I, ^ OH. IC<' . CH, 
UH 
. III CH, . IC . CH, CH JCOCH, + Hl . 
. ^OH 
Now it has been found ont that light acts as a positi\e catalysor 
in the above reaction. In the absence of an acid, the interaction 
between iodine and aqueous acetone proceeds very slowly ; so at 
the beginning equal amount of acid was added to each of the bottles 
in order to accelerate the reaction. 
Acetone and iodine. 
Quality of light j 
i 
Time of 
exposure 
Amount of 
iodine added 
Unchanged 
iodine 
Volume of solution 
1) Sunlight 
360' 
0.00635 
0.00145 
N 
1 5 c.c. iodine and 5 c.c. 
Darkness 
360' 
Do 
0.00248 
) acetone and 5 c.c. HCl 
2) Sunlight 
420' 
Do 
0.00121 
j Do 
Darkness 
420' 
Do 
0.00225 
3) Diffused light 
365' 
Do 
0.00197 
Do 
Darkness 
365' 
Do 
0.00242 
) 
4) Diffused light 
425' 
Do 
0.00162 
Do 
Darkness 
425' 
1 Do 
1 0.00219 
ii 
