Question

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

• A. Nitric acid
• B. Sodium hydroxide
• C. Hydrochloric acid
• D. Ammonia

Answer 1

The correct option is A Nitric acid

If nitrogen or sulphur is also present in the compound, the sodium fusion extract is first boiled with concentrated nitric acid to decompose cyanide or sulphide of sodium formed during Lassaigne’s test. These ions would otherwise interfere with silver nitrate test for halogens. Hence, the sodium fusion extract is acidified with nitric acid and then treated with silver nitrate.