A black coloured compound (A) on reaction with dilute `H_(2)SO_(4)` gives a gas (B) which on passing in a solution of an acid (C ) gives a white turbidity (D). Gas (B ) when passed in an acidified solution of a compound (E ) gives a precipitate (F) soluble in dil `HNO_(4)` . After boiling this solution when an excess of `NH_(4)OH` is added, a blue coloured compound (G) is formed. To this solution on addition of acetic acid and aqueous `K_(4)[Fe(CN)_(6)]` a chocolate precipitate (H) is obtained. On addition of an aqueous solution of `BaCl_(2)` to an aqueous solution of `(E)`, a white precipitate insolution in `HNO_(3)` is obtained. Identify (A) to (H).