The substances which give oxygen (for oxidation) are called oxidising agents. Alkaline potassium permanganae and acidified potassium dichromate are oxidising agents because they provide oxygen for oxidising other substances. For example, when ethanol is heated with alkaline postassium permanganate solution (or acidified potassium dichromae solution) it gets oxidised to ethanoic acid:
`underset("Ethanol")(CH_(3)CH_(2)OH) +underset("From oxidising agent")underset("Nascent oxygen")(2[O]) underset("or Acidified" K_(2)Cr_(2)O_(7))overset("Alkaline" KMnO_(4):"Heat")(to) underset("Ethanoic acid")(CH_(3)COOH)+underset("Water")(H_(2)O)`
Since the oxygen required for the oxidation of ethanol to ethanoic acid has been given by alkaline potassium permanganate (alkaline `KMnO_(4))` or acidified potassium dichromate (acidified `K_(2)Cr_(2)O_(7))` so both these substances are oxidising agents.