Which of the following compound is added to the sodium extract before addition of silver nitrate for testing of halogens?

Step-by-step solution

For testing of halogens, Nitric acid is added to the sodium extract because if CN - or S 2 - are present then they will be oxidised and removed before the test of halides. NaCN + HNO 3 → NaNO 3 + HCN ↑ Na 2 S + HNO 3 → NaNO 3 + H 2 S ↑ Nilnic acid decomposed NaCN   &   Na 2 S , else they precipitate in test & misquite the resolve