Potassium permanganate, either alone or mixed with sulphuric acid, is the Mallory bleach. This is commonly used as a general oxidation step which can either block or enable staining depending on the target tissue.
A simple potassium permanganate solution, can also be used to remove melanin from sections, thus enabling the nuclei to be examined in subsequent stains. A 1% aqueous potassium permanganate solution, applied for 30 minutes to one hour then bleached with 1% aqueous oxalic acid for a few minutes and washed, will usually be successful. The treatment may affect the adhesion of the section to the slide, so care must be taken in subsequent washing and staining. An adhesive is recommended.
It has also been used as an oxidant for converting hematoxylin to hematein at the rate of 0.177 grams permanganate for each gram of dye, although it is not a popular choice for that.