390 Proceedings of Royal Society of Edinburgh. [sess. 
by T. S. Price.* In it the author gives the result of his investiga- 
tions on the rate of the reaction at different concentrations, and 
on the effects which other substances have when present in the 
solution. He finds that the reaction is one of the second degree, 
not of the third, as was anticipated. It therefore agrees with the 
equation 
KI + KS0 4 = I + K 2 S0 4 
rather than 
2KI + K 2 S 2 0 8 = I 2 + 2K 2 S0 4 
although all molecular weight determinations lead to the doubled 
formula for persulphuric acid. The solutions dealt with in Price’s 
investigation were dilute, and it is impossible to say what effect 
the liberated iodine would have on the rate of decomposition ; 
there may be a certain amount of “ catalytic action,” the iodine 
being alternately oxidised by the persulphate and reduced by 
hydriodic acid. The reaction investigated may not be the 
comparatively simple one represented by the equation 
S 2 0 8 " + 2I' = I 2 + 2S0 4 " 
but may really be the much more complex one, as represented by 
the additional equations 
I 2 + 5S 2 0 8 " + 6H 2 0 = 2I0 3 # + 10SO 4 " + 12H* 
2I0 3 ' + 10P + 12H’ = 6I 2 + 6H 2 0 
* Z&its. fur phys. Chem ., xxvi. 474 (1898). 
