Why is it necessary to use acetic acid and not sulphuric acid for acidification of sodium extract for testing sulphur by lead acetate test?
Although the addition of sulphuric acid will precipitate lead sulphate, the addition of acetic acid will ensure a complete precipitation of sulphur in the form of lead sulphate due to common ion effect. Hence, it is necessary to use acetic acid for acidification of sodium extract for testing sulphur by lead acetate test.
For testing sulphur sodium extract is acidified with acetic acid because lead acetate is soluble and does not interfere with the test
`Pb(OCOCH_3)_2 + H_2SO_4 -> PbSO_4 "↓" + 2CH_3COOH`