When lassaigne's extract `(Na_(2)S)` is acidified with acetic acid and then lead acetate solution is added to it, the colour of the precipitate is

When acetic acid and potassium ferrocyanide are added to copper salt, the colour of the precipitate is

The sodium extract on acidification with acetric acid and then adding lead acetate solution gives a black precipitate. The organic compound contains.

The sodium extract of an organic compound on acidification with acetic acid and addition of lead acetate solution gives a black precipitate . The organic compound contains ________.