ION PAIR EFFECTS IN THE REACTION BETWEEN POTASSIUM FERROCYANIDE AND POTASSIUM PERSULFATE

Abstract

The rate of the reaction between potassium ferrocyanide and potassium persulfate has been measured over a range of conditions. The rate is dependent on the potassium ion concentration, and it is shown that this is explained if it is assumed that KFe(CN) 6 3− and KS 2 O 8 − are the reacting species. The equilibrium constants governing the formation of these ion pairs were measured with a cation-sensitive glass electrode. Similar constants for the products KFeCCN 6 ) 2− and KSO 4 − , and also for KNO 3 , were measured. From these equilibrium constants, the true rate constants of the reaction can be obtained, and it is shown that these vary with ionic strength in the manner predicted by Brönsted's equation.