Ammonium hexanitratocerate(IV) as an oxidising agent—II: Potentiometric titration of oxalic and mandelic acids at room temperature

Abstract

Conditions have been established for the accurate titration of oxalic and mandelic acids with ammonium hexanitratocerate(IV) at room temperature in a hydrochloric or nitric acid medium with a potentiometric end-point. It has been shown that 0.1 N or 0.01 N solutions of the oxidising agent can be standardised very conveniently, using sodium oxalate as a primary standard. The very rapid reaction now observed between cerate and oxalic acid in a hydrochloric acid medium (where the redox potential of cerate is about 1.28 V) is of fundamental significance, because it shows, unambiguously, that the ease of reaction between ammonium hexanitratocerate(IV) and oxalic acid in a nitric or perchloric acid medium is not caused by the higher oxidation potentials of the cerate obtaining in these acid media, as assumed by previous coworkers.