Benzenesulphonyl chloride ($C_6H_5SO_2Cl$) is also known as Hinsberg's reagent. The reaction of Hinsberg's reagent ($C_6H_5SO_2Cl$) with primary amine ($CH_3CH_2NH_2$) yields N-ethylbenzene sulphonamide, which is soluble in alkali. Secondary amines yield N-Ethyl-N-Methyl benzene sulphonamide which is insoluble in alkali due to absence of H-atom. 3° amine do not react with Hinsberg reagent.