sentences:  Anionic and cationic surfactants can be determined thermometrically by titrating one type against the other.For instance, benzalkonium chloride (a quaternary type cationic surfactant) may be determined in cleaners and algaecides for swimming pools and spas by titrating with a standard solution of sodium dodecyl sulfate.Alternatively, anionic surfactants such as sodium lauryl sulfate can be titrated with cetyl pyridinium chloride.