Azure A is an organic chloride salt having 3-amino-7-(dimethylamino)phenothiazin-5-ium as the counterion. It is used in making azure eosin stains for blood smear staining.
Azure A is a basic cationic dye.The combination of azure A and silver staining is used for the quantification of glycosaminoglycans in agarose gels. It is a main component of the azure B/polychromed methylene blue – eosin stains family, also referred to as the Romanowsky stain.