The compound formed in the positive test for nitrogen with the Lassaigne solution of an organic compound is (RPMT 2010) (a) 6 3 Fe Fe(CN) (b) Na Fe(CN) (c) Fe(CN) (d) Na Fe(CN) COS Ans. (a) Sol. 3Na Fe(CN) 4Fe → 6 3 Prussian blue iron(III) hexacyanoferrate(II) F e Fe(CN) Na Appearance of blue or green colour by using Lassaigne's extract indicates the presence of nitrogen.