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The exothermic (heat producing) reaction between potassium permanganate (KMnO 4), a strong oxidizing agent, and glycerol (C 3 H 5 (OH) 3), a readily oxidised organic substance, is an example of an experiment sometimes referred to as a "chemical volcano". [7] [8]
The reagent is an alkaline solution of potassium permanganate. Reaction with double or triple bonds (R 2 C=CR 2 or R−C≡C−R) causes the color to fade from purplish-pink to brown. Aldehydes and formic acid (and formates) also give a positive test. [43] The test is antiquated. Baeyer's reagent reaction
Potassium permanganate will decompose into potassium manganate, manganese dioxide and oxygen gas: 2 KMnO 4 → K 2 MnO 4 + MnO 2 + O 2. This reaction is a laboratory method to prepare oxygen, but produces samples of potassium manganate contaminated with MnO 2. The former is soluble and the latter is not.
Molecular models of the different molecules active in Piranha solution: peroxysulfuric acid (H 2 SO 5) and hydrogen peroxide (H 2 O 2). Piranha solution, also known as piranha etch, is a mixture of sulfuric acid (H 2 SO 4) and hydrogen peroxide (H 2 O 2).
Similar to potassium permanganate, the two-step decomposition of rubidium permanganate leads to the formation of rubidium manganate intermediates. It breaks down into manganese dioxide, rubidium oxide and oxygen. [4] The decomposition temperature is between 200 and 300 °C. [7] Drift-away oxygen caused an 8% mass loss in the product. [7]
Historically, industrial preparation via the Reichstein process used potassium permanganate as the bleaching solution. Acid-catalyzed hydrolysis of this product performs the dual function of removing the two acetal groups and ring-closing lactonization. This step yields ascorbic acid. Each of the five steps has a yield larger than 90%. [37]
The potassium salt does not form a hydrate. Because of its hygroscopic nature, it is less useful in analytical chemistry than its potassium counterpart. It can be prepared by the reaction of manganese dioxide with sodium hypochlorite: 2 MnO 2 + 3 NaClO + 2 NaOH → 2 NaMnO 4 + 3 NaCl + H 2 O
The salt is prepared from the reaction of potassium permanganate with calcium chloride [2] or from the reaction of aluminium permanganate with calcium oxide.It can also be prepared by reacting manganese dioxide with a solution of calcium hypochlorite and a little bit of calcium hydroxide to increase the pH level.