Glycerol on treatment with excess HI gives

An aqueous solution of a metal ion (A) on reaction with Kl gives a black brownish ppt (B) and this aqueous suspension on treatment with excess Kl gives orange yellowish solution. Then A is

FeSO_4 on treatment with excess of KCN gives a product that does not give test of Fe^(2+) . The product formed is

Glycerol on treatment with oxalic acid at 110^(@)C forms