Evaluation of Screened Indicators by Tristimulus Colorimetry

Abstract

Three acid-base indicators methyl red, ethyl red and dimethyl yellow are screened with appropriate inert dyes to improve the quality of colour change. The trichromatic parameters for the screened indicators are determined by weighted ordinate method and the colour transition curves are drawn in accordance with RUCS system and CIE Lab 1976 system. Of the studied combination, the screened indicator Methyl red + Methylene blue (3: 1) is found to be more superior due to its rapidity of colour change and achievement of grey colour at the end point.