(i) An inorganic compound (A) is formed on passing a gas (B) through a concentrated liquor containing sodium sulphide and sodium sulphite.
(ii) On adding (A) in to a dilute solution of silver nitrate, a white ppt. appears which quickly changes into black coloured compound (C).
(iii) On adding two or three drops of ferric chloride into the excess of solution of (A), a violet coloured compound (D) is formed. This colour disappears quickly.
(iv) On adding a solution of (A) into the solution of cupric chloride, a white ppt. is first formed which dissolves on adding excess of (A) forming a compound (E). Identify (A) to (E) and give chemical equations for the reactions at steps (i) to (iv).
