Potassium Manganate VI

Because carbonic acid is strong enough to cause immediate disproportionation of the manganate(VI), contamination of solvents by carbon dioxide must be avoided. All water and solvents should be boiled prior to use to remove any dissolved carbon dioxide. 

The product is dried over P2O5 in vacuo. Final yield 10.5 g. (85%). Anal. Calcd. for K2Mn04 K, 39.67 Mn, 27.87. Found (ranges for eight samples) K, 39.58-39.7 Mn, 27.8-27.9. If small amounts of Mn02 are detected by analysis, the product can be recrystallized from 50% KOH and isolated by the above technique. 

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Potassium manganate(VI), manganate(VII) double salt [123d2-73-l]... 

The raw potassium manganate(VI) from the secondary roaster or the Hquid-phase oxidizer contains a fair amount of insoluble material such as unreacted MnO and ore gangue. In most continuous processes, these insolubles are removed by sedimentation using thickeners or filtration and are disposed of as waste. 

Potassium iodide, 20 634 Potassium ions, 20 597, 598, 641 in soap-water system, 22 727 Potassium isotopes, 20 598 Potassium magnesium sulfate, 20 626 Potassium manganate(V), 15 592 Potassium manganate(VI), 15 594-596 Potassium metal, 20 604 production of, 20 600 reducing power of, 20 599 Potassium muds, 9 4 Potassium niobate, 17 152-153 Potassium nitrate, 20 609, 634-636 solubility of, 20 636t uses of, 20 636... 

The potassium manganate(VI) produced is then eicctrochemically oxidized, continuously or di.sconti-nuously. to potassium permanganate ... 

Fusion of a manganese compound with sodium carbonate and potassium nitrate (on porcelain) gives a green manganate(VI) (p.. 86)... 

Manganate(VI) formed in the initial oxidation process must first be dissolved in a dilute solution of potassium hydroxide. The concentrations depend on the type of electrolytic cell employed. For example, the continuous Cams cell uses 120 150 g/L KOH and 50 60 g/L K MnO the batch-operated Bitterfeld cell starts out with KOH concentrations of 150 160 g/L KOH and 200 220 g/L K MnO. These concentration parameters minimize the disproportionation of the K MnO and control the solubiUty of the KMnO formed in the course of electrolysis. 

Under extremely alkaline conditions, pH > 12, potassium permanganate reacts involving a single-electron transfer, resulting in the formation of manganate (VI). 

Ethanol can be oxidised to ethanoic acid (an organic acid also called acetic acid) by powerful oxidising agents, such as warm acidified potassium dichromate(vi), or potassium manganate(vu). 

Figure 15.5 Orange potassium dichromate(vi) slowly turns green as it oxidises ethanol to ethanoic acid. Potassium manganate(vn) turns from purple to colourless.

Sulfur dioxide (S02) Colourless (very choking smell) Red-acidic Turns acidified potassium dichromate(vi) from orange to green Turns acidified potassium manganate(vn) from purple to colourless... 

A range of salts of the anion has been described and it is known as a ligand—one notable example being (H3 0)2 [Mnlv (Mn04)6] H2 O, which is one of the products of dehydration of HMn04 in water. An X-ray analysis of the potassium and calcium salts has given Mn—O at 1.63 A—somewhat shorter, as expected, than in the manganate(VI) species. 

Oxidation of aromatic systems containing alkyl side-chains results in the formation of a carboxylic acid, irrespective of the length of the side-chain. The usual oxidizing agents are potassium permanganate [potassium manganate(VII)] or chromic acid [chromium(VI) acid]. For example, 1,4-dimethylbenzene is oxidized to benzene-1,4-dicarboxylic acid (tereph-thalic acid, 9), an important building block for polyesters. The oxidation of isopropylbenzene (cumene) to phenol is an important industrial process and is discussed in Chapter 4. 

Preparation of Manganese Oxalate (238). 4. Preparation of Manganese(II) Oxide (238). 5. Preparation of Sodium Manga-nate(V) (239). 6. Preparation of Sodium Manganate(VI) by the Solid-Phase Reaction of Manganese Dioxide with Sodium Peroxide (239). 7. Preparation of Potassium Permanganate by the... 

In this process, a mixture of finely ground MnOi minerals and a 70 to 90% potassium hydroxide solution, in a Mn07 KOH molar ratio of > l 5, is oxidized with air at 200 to 260°C under a slightly increased pressuie. The reaction time is 4 to 6 h. The manganate(VI) formed is crystallized out, the yield being 87 to 94%. 

The manganate(VI) is dissolved in a 12 to 16% potassium hydroxide solution. Depending upon the electrolysis process used, the manganate(Vl)-concentration can be 50 to 60 g/L (continuous) or 200 to 220 g/L (discontinuous). Byproducts of manganate(Vl)-production (gangue etc.) can be removed by filtration. 

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