$\mathrm{Black} \mathrm{solid} \underset{∆}{\overset{\mathrm{KOH}+\mathrm{Air}}{\to }}\underset{\mathrm{green}}{\left(\mathrm{A}\right)}\stackrel{{\mathrm{H}}_2{\mathrm{SO}}_4}{\to } \underset{\mathrm{purple}}{\left(\mathrm{B}\right)}+\left(\mathrm{C}\right)$

(i) KI on reaction with alkaline solution of (B) changes into a compound (D).
(ii) The colour of the compound (B) disappears on treatment with the acidic solution of FeSO₄.
(iii) With cold conc. H₂SO₄, compound (B) gives (E), which being explosive decomposes to yield (F) and oxygen.(Given Atomic weight of $Mn=55,O=16,K=39,H=1,Fe=56$)