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

Explanation

For testing sulphur, the sodium extract is acidified with acetic acid because lead acetate remanis soluble in acetic acid medium and hence does not interface with the test. If `H_(2)SO_(4)` be used, lead acetate itself will react with `H_(2)SO_(4)` to from white precipitate of lead sulphate.
`Pb(OCOCH_(3))+H_(2)SO_(4)-underset("White ppt.")(PbSO_(4))darr+2CH_(3)COOH`
This white precipitate of `PbSO_(4)` interfares with the test of sulphur, which involes the following reaction :
`Pb(OCOCH_(3))_(2)+Na_(2)Srarrunderset("Black ppt.")(PbSdarr+)2CH_(3)COONa`