Pyrolusite

Being an efficient oxidising agent, pyrolusite is directly put to several industrial uses such as 

For these purposes, the ore is graded on the basis of its oxidising capacity which is reported in terms of the percentage of Available Oxygen in pyrolusite. 

Available oxygen of pyrolusite is that part of oxygen which is available for oxidation of a reducing agent when the ore is treated with a strong acid  

A known weight of the dry ore is heated with cone. HCl. Chlorine equivalent to available oxygen is liberated as per the following equation 

The chlorine gas thus evolved is passed into a solution of K1 when an equivalent amount of iodine is liberated 

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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 ... 

Alternatively, a known weight of the pyrolusite may be heated with concentrated hydrochloric acid and the chlorine evolved passed into potassium iodide solution. The iodine liberated is titrated with sodium thiosulphate ... 

L. magnes, magnet, from magnetic properties of pyrolusite It. manganese, corrupt form of magnesia)... 

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. 

Pyrolusite, see Manganese(IV) oxide Pyrophanite, see Manganese titanate(IV)(2—) Pyrophosphate, see Diphosphate(V)... 

Pyrolusite is a black, opaque mineral with a metallic luster and is frequendy soft enough to soil the fingers. Most varieties contain several percent water. Pyrolusite is usually a secondary mineral formed by the oxidation of other manganese minerals. Romanechite, a newer name for what was once known as psilomelane [12322-95-1] (now a group name) (7), is an oxide of variable composition, usually containing several percent water. It is a hard, black amorphous material with a dull luster and commonly found ia the massive form. When free of other oxide minerals, romanechite can be identified readily by its superior hardness and lack of crystallinity. 

P-MnOj pyrolusite (8) single chains of edge-shared (MnO ) octahedra (1x1 channels)... 

The crystal stmcture of ramsdeUite [12032-73-4] is similar to that of P Mn02 except that double chains of MnO octahedra are cross-Unked to adjacent double chains through the sharing of oxygen atoms located at the corners. RamsdeUite and pyrolusite are the only manganese dioxide phases where the composition approaches the stoichiometric Mn02 formula. Heating ramsdeUite to 250°C transforms it to pyrolusite. 

Caro s acid has been used ia AustraUa as an oxidant ia the acid-leaching of uranium ores. It acts by oxidising the iron present ia the solution from Fe " to Fe ". This Fe " then oxidizes the uranium. Alternative oxidants that have been used iaclude pyrolusite and chlorate ion. These are both undesirable because their effluents, containing Mn " or CF, contaminate watercourses. 

Electrical Uses. Dry cells (see Batteries, primary cells) use graphite to render the nonconductive pyrolusite (Mn02) conductive through intimate admixture. The degree of graphitization is a factor in that graphites with the same carbon content and from the same locaUty give different results. 

Metallic manganese was first isolated in 1774 when C. W. Scheele recognized that pyrolusite contained a new element, and his fellow Swede, J. G. Gahn, heated the Mn02 with a mixture of charcoal and oil. The purity of this sample of the metal was low, and high-purity (99.9%) manganese was only produced in the 1930s when electrolysis of Mn solutions was used. 

Braunstsin, m. pyrolusite, manganese dioxide (roter) rhodochrosite (schwarzer) hausman-nite, -blende, /. alabandite. -kies, m. ala-bandite. -kiesela m. rhodonite, -rahm, -schsum, m, bog manganese, wad. braunstichig, a. brownish. 

Manganerz, n. manganese ore. — graues manganite pyrolusite. — schwarzes —, hausrnannite. 

Weich-bottich, m. steeping tub. -brand, m. soft brick, place brick, -braunstein, m. pyrolusite. -biitte, /. (Brewing) steep tank, cistern, -dauer, /. time of steeping or soaking. 

Pyrolusite. Dissolve 1.5-2 g, accurately weighed, pyrolusite in a mixture of 25 mL of 1 1 hydrochloric acid and 6 mL concentrated sulphuric add, and dilute to 250 mL. Filtration is unnecessary. Titrate an aliquot part containing 80-100 mg manganese add 200 mL freshly prepared, saturated sodium pyrophosphate solution, adjust the pH to a value between 6 and 7, and perform the potentiometric titration as described above. 

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