In Lassaigne's test for nitrogen in an organic compound, the blue colouration is due to the formation of

Question

In Lassaigne's test for nitrogen in an organic compound, the blue colouration is due to the formation of (A) ferrous ferricyanide (B) ferric ferrocyanide (C) potassium ferricyanide (D) potassium ferrocyanide

Tardigrade Admin · Accepted Answer

To a part of sodium extract, FeSO 4 solution is added and the contents are warmed. A few drops of FeCl 3 solution are then added and resulting solution is acidified with conc. HCl. The appearance of bluish green or Prussian blue colouration confirms the presence of nitrogen. The reactions that occur during this test are as 2 NaCN + FeSO 4 longrightarrow Na 2 SO 4+ Fe ( CN )2 Fe ( CN )2+4 NaCN longrightarrow underset textSodium ferrocyanideNa 4[ Fe ( CN )6] 3 Na 4[ Fe ( CN )6]+4 FeCl 3 longrightarrow underset textFerric ferrocyanide (Prussian blue)Fe 4[ Fe ( CN )6]3+12 NaCl

Q. In Lassaigne's test for nitrogen in an organic compound, the blue colouration is due to the formation of

ferrous ferricyanide

ferric ferrocyanide

potassium ferricyanide

potassium ferrocyanide