Comparative study of metallochromic indicators for magnesium

The performances of common metallochromic indicators for the complexometric titration of Mg were evaluated by comparing the results obtained in titration with EDTA, using the following indicators: Methylthymol Blue, Eriochrome Black T, Metalphthalein, Thymolphthalein Complexone, Pyrocatechol Violet, Eriochrome Blue-Black B, Calmagite, Antipyryl-p-Arsenazo I and Antipyryl-o-Arsenazo l. Tristimulus colorimetry theory was applied to the chromatic transitions of the indicators. As a result, Eriochrome Black T and Antipyryl-o-Arsenazo I are proposed as being the most suitable indicators for the complexometric titration of Mg with EDTA.