Chromogenic development

Chromogenic development process, 1, 369-373 Chromogens donor-acceptor, 1, 329 Chromoglycic acid sodium salts... 

The common term used for the colour forming process in colour photography is chromogenic development. The colours are formed by a chemical reaction between... 

Chromogenic development is the dye-coupling process in colour photography. 

In the chromogenic development process the exposed silver halide oxidizes a chemical reagent, the colour developer , to a species which in turn reacts with another reagent, the colour coupler , to give a dye. 

If desired, wash membrane in two 15-min washes of 50 ml TBS and process for chromogenic development (see Support Protocol I). 

The developing agents used for chromogenic development are generally members of the p-phenylenediamine class. Quinonediimines formed by oxidation of the developer react with the couplers, which are often precursors of indophenol or azomethine dyes. Although removal of the oxidation products of the developer by sulfite is not desired in chromogenic development, a little sulfite is usually still added to protect the developer from oxidation by air. As in b/w development, alkali and antifoggant materials are also present. 

The pyrazolone dye 16 may serve as an example of the use of pyrazolones as couplers in color photography, which react with the developer (e.g., N,N-diethyl-p-phenylenediamine) in an oxidative coupling process during the chromogenic development. 

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