Hinsberg's method is used for the separation of primary, secondary and tertiary amines. In this test, benzene sulfonyl chloride is used as a reagent. It reacts with primary amines and secondary to give sulfonamide product. The sulfonamide product from primary amines is soluble in alkali, but the sulfonamide product of secondary amines is not soluble in alkali. The reagent, benzene sulfonyl chloride does not react with the tertiary amines.