Potassium permanganate: finely powdered

Suspend in a round-bottomed flask 1 g. of the substance in 75-80 ml. of boihng water to which about 0 -5 g. of sodium carbonate crystals have been added, and introduce slowly 4 g. of finely-powdered potassium permanganate. Heat under reflux until the purple colour of the permanganate has disappeared (1-4 hours). Allow the mixture to cool and carefully acidify with dilute sulphuric acid. Heat the mixture under reflux for a further 30 minutes and then cool. Remove any excess of manganese dioxide by the addition of a little sodium bisulphite. Filter the precipitated acid and recrystallise it from a suitable solvent (e.g., benzene, alcohol, dilute alcohol or water). If the acid does not separate from the solution, extract it with ether, benzene or carbon tetrachloride. 

Potassium permanganate is dangerous when it is in the form of fine powder. Almost all the reactions below involve this form. 

The oxidant was prepared from 130 g of crystalline potassium permanganate (KMnO, ) and 25 g of CUSCV5H2O by grinding them together in a mortar until a fine powder was obtained. 

Halsey and Savage Explosives. Several smokeless powders, containing Ammonium Picrate, were patented in the US in 1896. They were prepd by adding finely pulverized Ammonium Picrate to an aqueous solution of potassium dichromate in such a manner as to form a plastic mass and then slowly adding a coned aqueous solution of potassium permanganate. 

The more finely divided the manganese dioxide the more rapid will be the reaction, so that the precipitated reagent is better than finely powdered pyrolusite. It is still better to prepare the precipitated hydroxide Mn(OH)4, by reducing the necessary quantity of potassium permanganate in neutral solution with alcohol and washing the precipitate from soluble potassium salts by decantation. 

Preparation of oxidative system Finely ground potassium permanganate (50 g) dissolved in water (100 mL) was added to alumina (acidic or neutral, Merck activity I, 63-200 nm 200 g). After shaking for 15 min, the majority of the water was removed by evaporation under reduced pressure and the obtained powder was dried under microwave irradiation for 5 min. 

Oxidation of toluene-o-sulphonamide to saccharin. In a 600-ml beaker, mounted on an electric hot plate and provided with a mechanical stirrer, place 12 g (0.07 mol) of toluene-o-sulphonamide, 200 ml of water and 3g of pure sodium hydroxide. Stir the mixture and warm to 34-40 °C until nearly all has passed into solution (about 30 minutes). Introduce 19g (0.32 mol) of finely powdered potassium permanganate in small portions at intervals of 10-15 minutes into the well-stirred liquid. At first the permanganate is rapidly reduced, but towards the end of the reaction complete reduction of the permanganate is not attained. The addition occupies 4 hours. Continue the stirring for a further 2-3 hours, and then allow the mixture to stand overnight. Filter off the precipitated manganese dioxide at the pump and decolourise the filtrate by the addition of a little sodium metabisulphite solution. Exactly neutralise the solution with dilute hydrochloric acid (use methyl orange or methyl red as external indicator). Filter off any o-sulphonamidobenzoic acid (and/or toluene-o-sulphonamide) which separates at this point. Treat the filtrate with concentrated hydrochloric acid until the precipitation of the saccharin is complete. Cool, filter at the pump and wash with a little cold water. Recrystallise from hot water. The yield of pure saccharin, m.p. 228 °C, is 7.5 g (58%). 

Magnesium carbonate V Manganese carbonate P. 70 Manganese dioxide, powder IV, XI Nickel carbonate XI Phosphorus, red II, X Porcelain chips, unglazed E. 5, P. 56 Potassium carbonate IX Potassium chlorate III, VIII Potassium dichromate IV Potassium hydroxide II, III Potassium iodate VIII Potassium iodide IV, VIII Potassium nitrate IV, XI Potassium permanganate IV, VIII Potassium sulphate Q. 3 Silicon dioxide, precipitated IX Silicon dioxide, coarse sand P. 66, 67 Silicon dioxide, fine sand P. 8, 43 Sodium bicarbonate P. 55 Sodium bromide IV Sodium carbonate, anhydrous III, IX, XI... 

Manganese dioxide, Mn02> is a commercially available, dark-brown powder prepared by the simultaneous addition of a 42.5% aqueous solution of manganese sulfate tetrahydrate and a 40% solution of sodium hydroxide to a hot stirred 14% aqueous solution of potassium permanganate. The brown precipitate is collected and washed with water until the washings are colorless, dried at 100-120 °C, and ground to a fine powder before use... 

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