Perchloric acid titrations in an acetic acid medium: indicator evaluation and new screened indicators

Abstract

Metformine titrations with perchloric acid in an acetic acid medium have been carried out in order to test several recommended indicators: crystal violet, methyl violet, Tropaeolin OO, bromocresol purple and malachite green; crystal violet and methyl violet were found to be the most suitable. From these studies two mixtures are proposed as screened indicators for improving observation of the end-point: methyl violet-Neozapon yellow-thymol blue and crystal violet-Neozapon yellow-thymol blue. The studies were carried out using tristimulus colorimetry theory.