Noun
English Wikipedia has an article on:3,3’,5,5’-TetramethylbenzidineWikipedia
tetramethylbenzidine (plural tetramethylbenzidines)
(organic chemistry) Any of several isomeric tetramethyl derivatives of benzidine, but especially 3,3’,5,5’-tetramethylbenzidine that is a chromogenic substrate used in immunohistochemistry