Effects of auxiliary complex-forming agents on the rate of metallochromic indicator colour change.
The rates of colour change reactions of metallochromic indicators such as XO, PAN, PAC and TAC at the equivalence point were measured in the chelatometric titration of copper, nickel, zinc or cobalt. Hexamine buffer has strong disturbing effects on the rate of colour change of the copper or nickel XO chelate. The effects of various auxiliary complex-forming agents were also examined. Bathophenanthroline, 2,2'-bipyridyl, 8-hydroxyquinoline, TPTZ, ethylenediamine, iminodiacetic acid, acetylacetone, 1,10-phenanthroline and glycine improve the colour change of the XO and PAN chelates of copper. Some titration methods for copper or nickel with XO or PAN as indicator are proposed.
Nakagawa
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Laboratory of Analytical Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya, Japan.
Wada
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H