Nickel complexes image dyes

In another application the dyes used in the dye-bleach process are not premetallized however, they contain metallizable sites so that after the bleaching step an after-bath treatment with a transition metal solution yields the metal-complexed dye. Bisazo dyes such as (35) yield greenish blue images after processing and treatment with a copper or nickel acetate solution.99 Complex-ation can and presumably does occur at more than one site in the molecule. 

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