Specifications of Colour Changes of Complexometric Indicators in the Titration of Zirconium With Ethylenediaminetetraacetic Acid

Trichromatic colorimetry was applied for the evaluation of the colour changes of the metallochromic indicators, viz., hematoxylin, gallocyanine, Gallamine Blue, Solochrome Prune AS, Celestine Blue, Eriochrome Black T, Xylenol Orange and Catechol Violet, in the complexometric titration of zirconium( IV) with ethylenediaminetetraacetic acid (EDTA) to measure the quality of colour change at the equivalence point using the parameters, L, a* and b* as defined by La Commission Internationale de 1’Eclairage (CIE) (1976) colour space, specific colour discrimination (SCD) and standard deviation of colour matching (AS). A screened indicator hematoxylin-Methylene Blue (3 + 1) was developed in an attempt to improve the quality of colour change.