Benzene sulphonyl chloride is the reaction used in Hinsberg's test which distinguishes between primary, secondary and tertiary amines. It reacts with dimethyl amine to give N,N-dimethyl benzene sulphonyl amide which lacks any H attached to N. Hence, N,N-dimethyl benzene sulphonyl amideis not acidic and and does not dissolve in aqueous KOH. It also does not dissolve in acid.