An aqueous solution of salt (A), gives white crystalline precipitate (B) with NaCl solution. The filtrate gives a black precipitate (C) when H2S is passed through it. Compound (B) is dissolves in hot water and the solution gives a yellow precipitate (D) on treating with NaI and cooling. The compound (A) does not give any gas with dilute HCl but liberates reddish brown gas on heating.