Warning: This experiment deals with very high temperatures in glass equipment. Face shields and protection against shattering glass is required. In addition small quantities of toxic gases are produced. This experiment should be performed outside or in a fume hood.
Make a vial with a mixture of 7 grams of potassium nitrate and 1 gram of manganese dioxide.
Using a torch carefully heat the mixture so they melt together. Smoke and fumes should be liberated as the potassium nitrate oxidizes any contaminants in the manganese dioxide.
Keep the mixture molten for a few minutes.
Now add 2 grams of potassium hydroxide and heat the mixture again thoroughly. It will boil and turn green as the reactants generate potassium manganate. Keep it on a gentle boil for several minutes.
Let the vial cool and then smash it apart with a hammer. Obtain the green solid and pulverize it into a powder. Mix this powder with 50 mL of water and dissolve the green potassium manganate. Let it settle and then pour off the solution.
The solution can be converted to potassium permanganate by adding drops of either sulfuric acid or sodium bicarbonate. Just keep adding and stirring until the solution turns purple. If you go too far it will turn light pink indicating the permanganate has been destroyed.
Let the byproduct of brown manganese dioxide settle out and the liquid is a weak solution of potassium permanganate.
A demonstration you can do is to add the solution to another solution of half a gram of sugar and sodium hydroxide. The purple/red solution of permanganate will go to a green and then to a yellow color as the permanganate ion is reduced.
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