Hoffmann's carbylamines test/ Isocyanide test:
Aliphatic or aromatic primary amines on heating with chloroform and alcoholic KOH give foul smelling alkyl isocyanides or carbylamines. This test is not given by secondary or tertiary amines.
Ph−NH2+CHCl3+3KOHΔ−→Ph−NC+3KCl+3H2O