How is potassium permanganate manufactured from `MnO_(2)` (pyrolusite)?

Explanation

Potassium permanganate is prepared by fusion of `MnO_(2)` with potassium hydroxide in presence of oxidising agent `KNO_(3)` to get potassium manganate `[K_(2)MnO_(4)]`.
`2MnO_(2)+4KOH+O_(2)rarr2K_(2)MnO_(4)+2H_(2)O`
potassium manganate on acidification gives potassium permanganate
`3MnO_(4)^(2-)+4H^(+)rarr2MnO_(4)+MnO_(2)+2H_(2)O`.