Naphthalene on oxidation with potassium permanganate or potassium dichromate gives phthalic acid. Potassium dichromate is an oxidising agent in organic chemistry, and is milder than potassium permanganate. The reaction with alkaline potassium permanganate solution affords 2,3-dihydroxybutyric acid. Sodium oxalate is used to standardize potassium permanganate solutions. Sodium permanganate behaves similarly to potassium permanganate. The reaction of permanganate with concentrated hydrochloric acid gives chlorine. The reagent is an alkaline solution of potassium permanganate. A dilute solution of potassium permanganate is an effective melanin bleach. Oxidants such as ozone, hydrogen peroxide, and potassium permanganate have been used. Potassium permanganate, sodium permanganate, and barium permanganate are all potent oxidizers. Oxidation can also be effected using conventional stoichiometric chromate or permanganate reagents. Potassium permanganate poses risks as an oxidizer. For example, a mixture of potassium permanganate and glycerol or pulverized glucose ignites readily. The breath sample was then pumped through an acidified potassium permanganate solution.