organic compounds containing a chain composed of an odd number of methine groups, =CH—, with conjugated double bonds; general formula, X (CH=CH)nCH=Y, where X and Y are groups containing atoms of N, O, or S, and n= 1–5. Some of the methine groups usually form heterocycles or aromatic residues. Polymethine dyes are fast and have bright and rich colors. They increase the photosensitivity of silver bromide and are widely used in photography. Many cationic polymethine dyes are also used in dyeing polyacrylonitrile fibers. One of the simplest polymethine dyes used in photography has the structure
REFERENCESChekalin, M. A., B. V. Pesset, and B. A. Ioffe. Tekhnologiia organiches-kikh krasitelei i promezhutochnykh produktov. Leningrad, 1972.
M. A. CHEKALIN