Tables for Chemistry

Potassium permanganate

Potassium permanganate (KMnO4 )

Potassium permanganate (CAS 7722-64-7) reacts with most reducing organic compounds. It is more reactive (less selective) in acidic solution.

Acidic solution

A 0.1M solution of potassium permanganate (1.6g in 100mL water) is acidified by the addition of sulphuric acid (1-2M, 5mL).
Many compounds appear as yellow spots against a purple background.

Basic solution

To 50mL of a 1% solution of potassium permanganate is added 50mL of a 2% sodium carbonate solution.
At first yellow spots appear against a purple background but soon they become brown and difficult to discern. Rinsing with water removes unreacted permanganate but leaves brown spots of manganese dioxide (MnO2 ) on a white background.