Reductimetric Determination of Nitroso-R-Salt with Iron(II) in Phosphoric Acid Medium

Abstract

Reductimeric titration methods involving potentiometric, visual (10-40 mg) and spectrophotometric (1-3 mg) techniques have been developed for the determination of nitroso-R-salt (NRS) using iron(II) as a reductant in phosphoric acid medium. The reduction of nitroso-R-salt by iron(II) is slow in phosphoric acid medium and found to be catalyzed by resorufin (RSF) which also functions as an excellent redox indicator. In this determination nitroso-R-salt is rapidly and quantitatively reduced to its amino compound by iron(II) in a four electron reduction step. The accuracy and precision of each of the method have been given. The formal redox potentials of [NRS]/[reduced NRS] couple, iron(III)/iron(II) couple, the transition potential of the indicator have been measured at the optimum titration conditions. Based on these potentials data, an explanation for the conditions needed for a satisfactory titration of the nitroso-R-salt has been given. The interference due to diverse ions has been studied.