The Lassaigne's extract is boiled with dil \( \mathrm{HNO_3} \) before testing for halogens because,
\( \mathrm{Ag_2S} \) is soluble in \( \mathrm{HNO_3} \).
Silver halides are soluble in \( \mathrm{HNO_3} \).
\( \mathrm{Na_2S} \) and \( \mathrm{NaCN} \) are decomposed by \( \mathrm{HNO_3} \).
\( \mathrm{AgCN} \) is soluble in \( \mathrm{HNO_3} \).