Primary, secondary and tertiary amines are distinguished by a chemical test called as the Hinsbergs test.

In this test, the amines are allowed to react with Hinsbergs reagent which is benzenesulphonyl chloride (C₆H₅SO₂Cl). The three types of amines react differently with Hinsbergs reagent. Therefore, they can be easily identified using Hinsbergs reagent.

1. Primary amines react with benzenesulphonyl chloride to form N-alkylbenzenesulphonyl amide which is soluble in alkali.

Due to the presence of a strong electron-withdrawing sulphonyl group in the sulphonamide, the H-atom attached to nitrogen can be easily released as proton. So, it is acidic and dissolves in alkali.

2. Secondary amines react with Hinsbergs reagent to give a sulphonamide which is insoluble in alkali.

There is no H-atom attached to the N-atom in the sulphonamide. Therefore, it is not acidic and insoluble in alkali.

3. On the other hand, tertiary amines do not react with Hinsbergs reagent at all.

There is one more way, though a less popular method, to distinguish between the three types of amines. If the mixture of amines is treated with diethyloxalate, which forms a solid oxamide with primary amine, a liquid oxime ester with secondary amine. The tertiary amine does not react.