Why is it necessary to use acetic acid and not sulphuric acid for acidification of sodium extract for testing sulphur by lead acetate test?

(N/A) The $Na_2S$ present in the sodium extract reacts with lead acetate to form lead sulphide $(PbS)$ precipitate.
If $H_2SO_4$ is used for acidification,it reacts with lead acetate to form lead sulphate $(PbSO_4)$ precipitate,which interferes with the test.
Acetic acid is a weak acid and does not form a precipitate with lead acetate,thus allowing the specific detection of sulphur as $PbS$.