Manganese dioxide, and

Oxidation of aniline with a mixture of manganese dioxide and sulfuric acid has been used commercially for production of -benzoquinone [106-51-4] (35). 

The precipitated manganese dioxide and sulfur are discarded. The solution is used until it becomes spent or so low in potassium permanganate that it is no longer effective and is discarded and replaced. It is customary to place two scmbbers in series, with the Hquid flow countercurrent to the gas flow, to more efficiendy use the permanganate solution. When the solution in the first scmbber is spent, with respect to the gas, the positions of the scmbbers are... 

Oxidation. Citric acid is easily oxidized by a variety of oxidizing agents such as peroxides, hypochlorite, persulfate, permanganate, periodate, hypobromite, chromate, manganese dioxide, and nitric acid. The products of oxidation are usually acetonedicarboxyhc acid (5), oxaUc acid (6), carbon dioxide, and water, depending on the conditions used (5). 

Chemical Properties. Potassium cyanide is readily oxidized to potassium cyanate [590-28-3] by heating in the presence of oxygen or easily reduced oxides, such as those of lead or tin or manganese dioxide, and in aqueous solution by reaction with hypochlorites or hydrogen peroxide. 

Purpurin [81-54-9] (179) is a usefiil iatemiediate for preparing acid-mordant dyes, and is prepared by oxidation of alizarin with manganese dioxide and sulfuric acid (145). 

If the solution is allowed to flow through a granular bed such as sand, the larger particulate matter remains on the surface, while the smaller material is collected in the thickness of the granular bed. Pressurization of the filter accelerates the process. Besides sand, other materials used as filtering media are anthracites, manganese dioxide, and activated carbon. 

Laudanosine contains four methoxyl groups. By exhaustive methyla-tion it yields trimethylamine and laudanosene (tetramethoxy-o-vinyl-stilbene), CH2=CH—C6H2(OCH3)2—CH=CH—C6H3(OCH3),. On oxidation with manganese dioxide and sulphuric acid it furnishes, in addition to the interesting by-product 2 3 6 7-tetramethoxy-9 10-dihydroanthracene, veratraldehyde and 4 5-dimethoxy-2 )3-methyl-... 

Commercially available hydrogen fluoride usually is not suitable for catalytic hydrogenation because of its sulfur dioxide content An oxidative treatment with manganese dioxide and distillation are needed for the preparation of hydrogena tion-grade hydrogen fluoride [d, 4]... 

The procedure is experimentally simple, and the workup involves only the destruction of the traces of hydrogen peroxide with manganese dioxide and evaporation of the hexamethyldisiloxane. Pyridine additives serve to buffer the highly acidic rhenium species and to shut down the detrimental acid-catalyzed epoxideopening pathways. The scope of this transformation is best appreciated through the examples presented in Table 12.2 [28],... 

Structural Chemistry of Manganese Dioxide and Related Compounds... 

At the end of the reaction time there was no unreacted amine as shown by the following test A 10-ml. aliquot was filtered through Supercel to remove the manganese dioxide, and the filtrate was added to a mixture of 25 ml. of benzene and 25 ml. of water. Extraction of the benzene layer with 10% hydrochloric acid, followed by the addition of sodium hydroxide, gave no oil layer or characteristic odor of the free amine. 

It is used to make oxygen in laboratories. One has to heat a mixture of manganese dioxide and an alkaline chlorate. This reaction, which is known for not being dangerous and often used in lectures, gives rise to anhydrous manganese dichloride which reacts explosively with potassium or zinc. Detonation of the mixture is known to have led to several accidents. 

Violence of reaction depends on concentration of acid and scale and proportion of reactants. The following observations were made with additions to 2-3 drops of ca. 90% acid. Nickel powder, becomes violent mercury, colloidal silver and thallium powder readily cause explosions zinc powder causes a violent explosion immediately. Iron powder is ineffective alone, but a trace of manganese dioxide promotes deflagration. Barium peroxide, copper(I) oxide, impure chromium trioxide, iridium dioxide, lead dioxide, manganese dioxide and vanadium pentoxide all cause violent decomposition, sometimes accelerating to explosion. Lead(II) oxide, lead(II),(IV) oxide and sodium peroxide all cause an immediate violent explosion. 

Many metal sulfides when mixed intimately with metal halogenates form heat-, impact- or friction-sensitive explosive mixtures [1], That with antimony trisulfide can be initiated by a spark [2] and with silver sulfide a violent reaction occurs on heating [3], For the preparation of oxygen mixture , antimony trisulfide was used in error instead of manganese dioxide, and dining grinding, the mixture of sulfide and chlorate exploded very violently [4],... 

Red phosphorus reacts vigorously on heating with copper oxide or manganese dioxide and on grinding with lead oxide, mercury oxide or silver oxide, ignition may occur. Red phosphorus ignites in contact with lead peroxide, potassium peroxide or sodium peroxide, while white phosphorus explodes, and also in contact with molten chromium trioxide at 200°C. 

Shao-Hom Y., Hackney S. A., Comilsen B. C., Structural characterization of heat-treated electrolytic manganese dioxide and topotactic transformation of discharge products in the Li-Mn02 cells, J. Electrochem. Society, (1997) 144, 3147-3153. 

It is considered that hydrous manganese dioxides and their derivatives used as sorbents belong to the crystallographic group of a-Mn02, where the atomic ratio 0 Mn<2, and the presence of side ions is a prerequisite of the very existence of this type of the crystalline lattice. For example, in various synthetic samples, the 0 Mn ratio can vary from 1.95 to 1.70. This means that the oxidation state of manganese in synthetic manganese oxides is seldom equal to 4. 

To determine 63 Ni in seawater the nickel was adsorbed on to hydrous manganese dioxide and the precipitate dissolved in hydrochloric acid. The nickel was then extracted with diethyldithiocarbamate in chloroform and determined by liquid scintillation counting [527]. 

Gandon and Guegueniat [587] investigated the recovery of tin from seawater using manganese dioxide and using125 Sr as a tracer. Enrichment factors of 103 to 105 were found. 

Aldehyde 244 reacts with manganese dioxide and sodium cyanide in ethanol to give ethyl ester 245 (Scheme 19), while oxidation of alcohol 12 with sodium peroxodisulfate in the presence of a catalytic amount of ruthenium chloride furnishes the carboxylic acid 246 (Scheme 19) <1998CPB287>. 

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