Chemiluminescence is the emission of light from chemical reactions at ordinary temperatures. The reactions of chemiluminescence produce a reaction intermediate or product in an electronically excited state, and radiative decay of the excited state is the source of the light. Chemiluminescence relates to fundamental molecular interactions and transformations and its study provides access to basic elements of reaction mechanisms and molecular properties, efficient chemiluminescence can provide an emergency or portable light source, chemiluminescence provides means to detect and measure trace elements and pollutants for environmental control or clinically important substances, and classification of the bioluminescent relationship between different organisms defines their biological relationship and pattern of evolution.
Liquid‐phase, gas‐phase, and solid‐phase chemiluminescence are discussed as well as bioluminescence, which is characteristic of numerous marine and a few land organisms. The applications of chemical light include marking and illumination and several types of analyses such as flow injection, hplc, direct metal, titration indicators, immunoassay, bacteria and biomass determination, and air pollution.