ABSTRACT
Many anionic surfactants can react with a cationic dye such as methylene blue to form strong ion pairs that can be extracted by a suitable organic solvent and can be determined using colorimetric techniques. e anionic surfactants that respond to the methylene blue test are primarily the sulfonate +–3(RSO Na ) and the sulfate ester
– 3(ROSO N a )+ type substances.
