Abstract
1. A method for the histochemical localization of protein-bound tyrosine and other ortho unsubstituted substituted phenols by the formation of a nitrosophenol-metal chelate is described. 2. The histochemical formation of a nitrosophenol confirms the postulated first step in the diazotization-coupling reaction for the histochemical demonstration of protein-bound tyrosine. 3. Though the described method is useful as a confirmatory technique for the localization of protein-bound tyrosine, its sensitivity is markedly less than that of the diazotization-coupling reaction.