Pyrolusite in oxidation

Pyrolusite, in oxidation of sulfurous acid to dithionate ion, 2 168 Pyrophosphates, determination of, in mixtures of phosphates, 3 93 Pyrophosphoric acid, 3 96, 97 Pyrosulfites, alkali metal, 2 162 Pyrosulfuryl chloride, 3 124, 126... 

Pizzigallo et al. (1998) investigated the reaction of 4-chloroaniline with ferric oxide and two forms of manganese dioxide [birnessite (5-Mn02) and pyrolusite (Mn02)] within the pH range of 4-8 at 25 °C. The reaction rate of 4-chloroaniline was in the order birnessite > pyrolusite > ferric oxide. At pH 4.0, the reaction with birnessite was so rapid that the reaction could not be determined. Half-lives for the reaction of 4-chloroaniline with pyrolusite and ferric oxide were 383 and 746 min, respectively. The reaction rate decreased as the pH was increased. The only oxidation compounds identified by GC/MS were 4,4 -dichloroazobenzene and 4-chloro-4 -hydroxydiphenylamine. 

Manganese is mainly present as manganese (II) carbonates, but in some sediments and on weathering surfaces it is present as higher oxides such as manganite and pyrolusite. In some pelagic sediments the amount... 

Manganese is the 12th most abundant element on the earth s surface. Its most important ore source is pyrolusite (Mn02). The preparation and uses of manganese and its compounds (which range up to +7 in oxidation state) are intimately bound up with electrochemistry. 

The Mn ion in pyrolusite (Mn02) is rather inert in oxidation reactions, evidently because the one-electron Mn — Mn reduction step is not a very favorable reaction. 

Our objectives for this research were to (1) use XANES spectroscopy to quantify subtle changes in solid-state geochemistry after hydrodynamic flow (2) determine if geochemical reduction of structural Mn(IV) or Fe(III) in oxide minerals occurred by surface-associated Co(II)EDTA (3) identify the source of Co(II) oxidation inhibition in pyrolusite and ferrihydrite media. 

The subsequent story of manganese is associated with T. Bergman who by that time had already confirmed the discovery of nickel. He characterized pyrolusite in the following way the mineral called black magnesium is a new earth it should not be confused either with roasted lime or with magnesium alba (i.e. magnesium oxide). However, T. Bergman failed to separate the metal from pyrolusite, in contrast to I. Kaim. 

G. Scheele was the third chemist who tried to separate a new element from this mineral. In 1774 he submitted his paper On Manganese and Its Properties to the Stockholm Academy of Sciences in it he summed up the three years of studies of pyrolusite. In this extremely informative paper he reported the discovery of two metals (barium and manganese) and described two gaseous elements (later identified as chlorine and oxygen). Scheele established that manganese oxide differed from all earths known at the time. 

In addition to the pillared manganese oxide materials, birnessite itself also has been widely used as a catalyst. The catalytic activity of birnessite for liquid-phase decomposition of acetone, methanol, and 2-propanol has been reported [67]. Sodium-, potassium-, bismuth-, lead-, and zinc-exchanged birnessite materials have shown superior catalytic activities compared to pyrolusite in the decom-... 

Manganese is the third most abundant transition metal, and is widely distributed in the earth s crust. The most important ore is pyrolusite, manganese(IV) oxide. Reduction of this ore by heating with aluminium gives an explosive reaction, and the oxide Mn304 must be used to obtain the metal. The latter is purified by distillation in vacuo just above its melting point (1517 K) the pure metal can also he obtained by electrolysis of aqueous manganese(II) sulphate. 

Manganese(IV) oxide is the only familiar example of this oxidation state. It occurs naturally as pyrolusite, but can be prepared in an anhydrous form by strong heating of manganese(II) nitrate ... 

An oxidation which can be used to estimate the amount of man-ganese(IV) oxide in a sample of pyrolusite is that of ethanedioic acid ... 

Most manganese today is obtained from ores found in Russia, Brazil, Australia, Republic of S. Africa, Gabon, and India. Pyrolusite and rhodochrosite are among the most common manganese minerals. The metal is obtained by reduction of the oxide with sodium, magnesium, aluminum, or by elctrolysis. 

Manganese Mn, at wt 54.94, brittle, silvery metal, mp 1245°, bp 2097°, d 7,44g/cc, Mohs hardness 5 decomps in w, readily dissolved in dil mineral acids. Usually associated with Fe ores in sub-marginal concns. Important ores of Mn are pyrolusite, manganite, psilomelane rhodochrosite. Prepd by reduction of the oxide with Al or C. Pure Mn is obtained electrolyti-cally from sulfate or chloride sain. It is used, in powd form, in the manuf of delay powds and in some pyrotechnic mixts. The requirements of the USA Armed Forces are covered by... 

A rich supply of manganese lies in nodules of ore that litter the ocean floors (Fig. 16.9). These nodules range in diameter from millimeters to meters and are lumps of the oxides of iron, manganese, and other elements. However, because this source is technically difficult to exploit, manganese is currently obtained by the thermite process from pyrolusite, a mineral form of manganese dioxide ... 

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