315 
of hydrolysis, and these OH’-ions react on the iodine which is set 
free re-forming iodide and iodate: 
Hence at the higher temperatures, less iodine seems to be formed 
from the mixture of iodic acid and potassium iodide in presence of 
concentrated sodium or magnesium sulphate. 
On the other hand, solutions of zine and ammonium sulphates 
produce H'-ions due to hydrolysis and these H'-ions are very active 
in liberating iodine according to the following equation: 
10'",+5’+6H =31,4+3H,0. 
Moreover, I have repeatedly observed that addition of acids pro- 
duces more iodine, from a mixture of iodie acid and potassium 
iodide, than in the absence of acids. ‘ 
Hence the abnormal effect of temperature on the velocity of the 
reaction between iodie acid and potassium iodide in presence of 
sodium sulphate ascribed by SkraBaL to complex formation, is really 
due to secondary changes produced by the interaction of the products 
of the hydrolysis on the reacting substances. 
A similar explanation is applicable to the small temperaturé coef- 
ficients obtained in the reaction between iodic acid and potéssium 
iodide in presence of sodium acetate, sodium phosphate and potas- 
sium fluoride; because all these salts are alkaline due to hydrolysis, 
The reaction between iodic acid and potassium iodide is extremely 
rapid even at O°. The reactions between KI and K,S,O, and KI 
and H,O, have smaller velocities than that between HIO, and KI. 
These two reactions have temperature coefficients greater than unity. 
Experiments were made on the effect of concentrated MgSO, solution 
on the influence of temperature on the reactions between HI and 
K,S,0, and HI and H‚O,. Even in presence of MgSO,, these two 
reactions have temperature coefficients greater than unity. The hot 
tubes contain much more iodine than the cold ones. 
In this connection, it is interesting to observe that the solubility 
of iodine in KI or HI is greatly diminished by the presence of MeSO 
HCl does not produce an increase in the amount of iodine libe- 
rated in the following cases: 
(a) K,S,0, + KI, (6) K,S,0, + HI, (c) Ferric nitrate + KI. 
In the following cases, HCI markedly increases the amount of iodine 
(a) H,O, + KI, (6) H,O, + HI, (c) HIO, + KI, (d) HIO, + HI, 
(e) H,Cr,O, + HI, (7) K,Fe (CN), + KI, (9) HNO, + KI. 
The last two reactions have temperature coefficients greater than 
unity even in presence of HCl. 
21 
Proceedings Royal Acad. Amsterdam. Vol. XXIII. 
