An aqueous solution of salt (A) gives a white crystalline precipitate (B) with NaCl solution. The filtrate gives a black precipitate (C) when H2S gas is passed through it. Compound (B) dissolves in hot water and the solution gives yellow precipitate (D) on treatment with KI and cooling or orange precipitate with K2CrO4 or white precipitate with dilute H2SO4 solution which is insoluable in C2H5OH. The compound (A) does not evolve any gas with dilute HCl, liberates a reddish brown gas on heating. Identify the compounds (A) to (D).
