What is Hinsberg reagent?

Benzenesulphonyl chloride $(C_{6}H_{5}SO_{2}Cl)$ is known as Hinsberg's reagent.
It is used to distinguish between primary,secondary,and tertiary amines.
Primary amines react with Hinsberg's reagent to form $N$-alkylbenzenesulphonamide,which is soluble in alkali.
Secondary amines react with Hinsberg's reagent to form $N,N$-dialkylbenzenesulphonamide,which is insoluble in alkali.
Tertiary amines do not react with Hinsberg's reagent.
The reaction of diethylamine (a secondary amine) with benzenesulphonyl chloride is shown below:
$C_{6}H_{5}SO_{2}Cl + HN(C_{2}H_{5})_{2} \rightarrow C_{6}H_{5}SO_{2}N(C_{2}H_{5})_{2} + HCl$