In
chemistry, the term chromogen refers to a colourless (or faintly coloured)
chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
that can be converted by chemical reaction into a compound which can be described as "coloured".
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
Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology and ...
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.
Applications in chemistry
*In
chromogenic photography,
film or
paper
Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, rags, grasses or other vegetable sources in water, draining the water through fine mesh leaving the fibre evenly distrib ...
contains one or many layers of
silver halide (AgX) emulsion, along with
dye couplers
Dye coupler is present in chromogenic film and paper used in photography, primarily color photography. When a color developer reduces ionized (exposed) silver halide crystals, the developer is oxidized, and the oxidized molecules react with dye ...
that, in combination with processing chemistry, form visible
dyes.
Applications in biochemistry and medicine
*The
Runyon classification classifies
mycobacteria by chromogenic properties.
References
{{Reflist
Color
Chemistry