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{{More citations needed|date=February 2022}}{{Short description|Chemical compound that can be converted into a dye or pigment}}
In [[chemistry]], the term '''chromogen''' refers to a colourless (or faintly coloured) [[chemical compound]] that can be converted by chemical reaction into a compound which can be described as "coloured" (a [[chromophore]]).<ref name="Burkinshaw2016">{{cite book|last1=Burkinshaw|first1=Stephen M.|url=https://books.google.com/books?id=4SjdCQAAQBAJ&q=chromogen+chemistry&pg=PA75|title=Physico-chemical Aspects of Textile Coloration|date=2016|publisher=John Wiley & Sons|isbn=9781118725696|page=75|language=en|oclc=1038053293|access-date=2020-11-05|archive-date=2022-02-24|archive-url=https://web.archive.org/web/20220224103523/https://books.google.com/books?id=4SjdCQAAQBAJ&q=chromogen+chemistry&pg=PA75|url-status=live}}</ref><ref name="Cain1905">{{cite book |last1=Cain |first1=John Cannell |last2=Thorpe |first2=Jocelyn Field |title=The Synthetic Dyestuffs and the Intermediate Products from which They are Derived |date=1905 |publisher=C. Griffin, limited |pages=[https://archive.org/details/syntheticdyestuf00cainuoft/page/38 38]-40 |url=https://archive.org/details/syntheticdyestuf00cainuoft |quote=chromogen classification. |access-date=2 September 2018 |language=en}}</ref> There is no universally agreed definition of the term. Various dictionaries give the following definitions:
* A substance capable of conversion into a pigment or dye.
* Any substance that can become a pigment or coloring matter, a substance in organic fluids that forms colored compounds when oxidized, or a compound, not itself a dye, that can become a dye.
* Any substance, itself without color, giving origin to a coloring matter.
In [[biochemistry]] the term has a rather different meaning. The following are found in various dictionaries.
* A precursor of a biochemical pigment
* A pigment-producing microorganism
* Any of certain bacteria that produce a pigment
* A strongly pigmented or pigment-generating organelle, organ, or microorganism.{{Citation needed|date=February 2022}}
==Applications in chemistry==
*In [[chromogenic photography]], [[photographic film|film]] or [[photographic paper|paper]] contains one or many layers of [[silver halide]] (AgX) emulsion, along with [[Dye coupler|dye couplers]] that, in combination with processing chemistry, form visible [[dyes]].
==Applications in biochemistry and medicine==
*The [[Runyon classification]] classifies [[mycobacteria]] by chromogenic properties.
==References==
{{Reflist}}
[[Category:Color]]
[[Category:Chemistry]]
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