(A) Give a blue solution in `H_(2)O`. On passing `H_(2)S`, a black precipitate (B) is formed which is soluble in `HNO_(3)`. On addition of NaOH, the solution gives glue precipitate (C ) which becomes black on boiling in NaOH. On passing ammonia into solution of (A) in water, a deep blue precipitate is ofrmed, which dissolves in excess of `NH_(3)` giving deep blue colouration (D). Treatment of KCN with aqueous solution of (A) gives a yellow ppt. (E) which dissloves in excess of KCN giving a colourless solution.

Explanation