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MANGANESE (symbol Mn; atomic weight, ...

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Originally appearing in Volume V17, Page 571 of the 1911 Encyclopedia Britannica.
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MANGANESE (See also:symbol Mn; atomic See also:weight, 54.93 (0=16)], a metallic chemical See also:element. Its dioxide (pyrolusite) has beenknown from very See also:early times, and was, at first mistaken for a magnetic See also:oxide of See also:iron. In 1740 J. H. See also:Pott showed that it did not contain iron and that it yielded a definite See also:series of salts, whilst in 1774 C. See also:Scheele proved that it was the oxide of a distinctive See also:metal. Manganese is found widely distributed in nature, being generally found to a greater or less extent associated with the See also:carbonates and silicates of iron, See also:calcium and See also:magnesium, and also as the minerals braunite, hausmannite, See also:psilomelane, See also:manganite, manganese spar and hauerite. It has also been recognized in the See also:atmosphere of the See also:sun (A. See also:Cornu, Comptes rendus, 1878, 86, pp. 315, 530), in See also:sea See also:water, and in many See also:mineral See also:waters. The metal was isolated by J. G.

Gahn in 1774, and in 1807 J. F. See also:

John (Gehlen's Jour. chem. phys., 1807, 3, p. 452) obtained an impure metal by reducing the carbonate at a high temperature with See also:charcoal, mixed with a small quantity of oil. R. See also:Bunsen prepared the metal by electrolysing manganese chloride in a porous See also:cell surrounded by a See also:carbon crucible containing hydrochloric See also:acid. Various reduction methods have been employed for the See also:isolation of the metal. C. See also:Brunner (Pogg. See also:Ann., 1857, 101, p. 264) reduced the fluoride by metallic See also:sodium, and E. Glatzel (Ber., 1889, 22, p.

2857) the chloride by magnesium, H. See also:

Moissan (Ann. Chim. Phys., 1896 (7) 9, p. 286) reduced the oxide with carbon in the electric See also:furnace; and H. See also:Goldschmidt has prepared the metal from the oxide by means of his " thermite " See also:process (see See also:CHROMIUM). W. H. See also:Green and W. H. Wahl [See also:German patent 70773 (1893)] prepare a 97% manganese from pyrolusite by See also:heating it with 30% sulphuric acid, the product being then converted into manganous oxide by heating in a cur-See also:rent of reducing See also:gas at a dull red See also:heat, cooled in a reducing atmosphere, and finally reduced by heating with granulated See also:aluminium in a See also:magnesia crucible with See also:lime and fluorspar as a See also:flux. A purer metal .is obtained by reducing manganese See also:amalgam by See also:hydrogen (O.

Prelinger, Monats., 1894, 14, P. 353). Prelinger's manganese has a specific gravity of 7.42, and the variety obtained by distilling pure manganese amalgam in vacua is pyrophoric (A. Guntz, See also:

Bull. See also:Soc. [3], 7, 275), and See also:burns when heated in a current of See also:sulphur dioxide. The pure metal readily evolves hydrogen when acted upon by sulphuric and hydrochloric acids, and is readily attacked by dilute nitric acid. It precipitates many metals from solutions of their salts. It is employed commercially in the manufacture of See also:special steels. (See IRON AND See also:STEEL.) COMPOUNDS Manganese forms several oxides, the most important of which are manganous oxide, MnO, trimanganese tetroxide, Mn3O4, manganese sesquioxide, Mn2Os, manganese dioxide, MnO,, manganese trioxide, MnO,, and manganese heptoxide, Mn2O2. Manganous oxidz, MnO, is obtained by heating a mixture of anhydrous manganese chloride and sodium carbonate with a small quantity of ammonium chloride (J. v. See also:Liebig and F.

See also:

Wohler, Pogg. Ann., 183o, 21, p. 584) ; or by reducing the higher oxides with hydrogen or carbon monoxide. It is a dark coloured See also:powder of specific gravity 5.09. Manganous hydroxide, Mn(OH)2, is obtained as a See also:white precipitate on adding a See also:solution of a See also:caustic See also:alkali to a manganous See also:salt. For the preparation of the crystalline variety identical with the mineral pyrochroite (see A. de Schulten, Comptes rendus, 1887, 105, p. 1265). It rapidly oxidizes on exposure to See also:air and turns See also:brown, going ultimately to the sesquioxide. Trimanghnese tetroxide, MnsO4, is produced more or less pure when the other oxides are heated. It may be obtained crystalline by heating manganese sulphate and See also:potassium sulphate to a See also:bright red heat (H. Debray, Comptes rendus, 1861, 52, p. 985).

It is a reddish-brown powder, which when heated with hydrochloric acid yields See also:

chlorine. Manganese sesquioxide, Mn20s, found native as the mineral braunite, may be obtained by igniting the other oxides in a mixture of See also:nitrogen and See also:oxygen, containing not more than 26% of the latter gas (W. Dittmar, Jour. Chem. Soc., 1864, 17, p. 294). The hydrated See also:form, found native as the mineral manganite, is produced by the spontaneous oxidation of manganous hydroxide. In the hydrated See also:condition it is a dark brown powder which readily loses water at above too° C., it dissolves in hot nitric acid, giving manganous nitrate and manganese dioxide: 2MnO(OH) + 2HNOs = Mn(NO3)2 + MnO, + 2H2O. Manganese dioxide, or pyrolusite (q.v.), MnO2, the most important oxide, may be prepared by heating crystallized manganous nitrate until red fumes are given off, decanting the clear liquid, and heating to 15o° to 16o° C. for 40 to 6o See also:hours (A. Gorgen, Bull. Soc., 1890 [3], 4, p. r6), or by heating manganese carbonate to 260° C. in the presence of air and washing the See also:residue with very dilute See also:cold hydrochloric acid. It is a hard See also:black solid which readily loses oxygen when strongly heated, leaving a residue of Mn3O4.

When heated with concentrated hydrochloric acid it yields chlorine, and with concentrated sulphuric acid it yields oxygen. It is reduced to the monoxide when heated in a current of hydrogen. It is a strong oxidizing See also:

agent. It dissolves in cold concentrated hydrochloric acid, forming a dark brown solution which probably contains manganic chloride (see R. J. See also:Meyer, Zeit. anorg. Chem., 1899, 22, p. 169; G. See also:Neumann, Monats., 1894, 15, p. 489). It is almost impossible to prepare a pure hydrated manganese dioxide owing to the readiness with which it loses oxygen, leaving residues of the type xMnO•yMnO2• Such mixtures are obtained by the See also:action of alkaline hypochlorites on manganous salts, or by suspending manganous carbonate in water and passing chlorine through the mixture. The solid See also:matter is filtered off, washed with water, and warmed with 10 i'o nitric acid (A.

Gorgen). It is a dark brown powder, which reddens See also:

litmus. Manganese dioxide combines with other basic oxides to form manganites, and on this See also:property is based the See also:Weldon process for the recovery of manganese from the See also:waste liquors of the chlorine stills (see CHLORINE). The manganites are amorphous brown solids, insoluble in water, and decomposed by hydrochloric acid with the See also:evolution of chlorine. Manganese trioxide, MnO3, is obtained in small quantity as an unstable deliquescent red solid by dropping a solution of potassium permanganate in sulphuric acid on to dry sodium carbonate (B. Franke, Jour. prak. Chem., 1887 [2], 36, p. 31). Above 50° C. it decomposes into the dioxide and oxygen. It dissolves in water forming manganic acid, H2MnO4. Manganese heptoxide, M n207, pre-pared by adding pure potassium permanganate to well cooled, concentrated sulphuric acid, when the oxide separates as a dark oil (H. Aschoff, Pogg.

Ann., 1860, 111, p. 217), is very unstable, continually giving off oxygen. It decomposes violently on heating, and explodes in contact with hydrogen, sulphur, See also:

phosphorus, &c. It dissolves in water to form a deep red solution which contains permanganic acid, HMnO4. This acid is also formed by decomposing See also:barium or See also:lead permanganate with dilute sulphuric acid. It is only known in aqueous solution. This solution is of a deep See also:violet-red See also:colour, and is somewhat fluorescent; it decomposes on exposure to See also:light, or when heated. It is a monobasic acid, and a very powerful oxidizing agent (M. M. P. See also:Muir, Jour. Chem.

Soc., 1907, 91, P.1 485)- Manganous Salts.—The anhydrous chloride, MnCl2, is obtained as a See also:

rose-red crystalline solid by passing hydrochloric acid gas over manganese carbonate, first in the cold and afterwards at a moderate red heat. The hydrated chloride, MnC12.4H2O, is obtained in rose-red crystals by dissolving the metal or its carbonate in aqueous hydrochloric acid and concentrating the solution. It may be obtained in at least two different forms, one isomorphous with NaCI.2H2O, by concentrating the solution between 15° C. and 20° C.; the other, isomorphous with FeCl2.4H2O, by slow evaporation of the See also:mother liquors from the former. It forms See also:double salts with the chlorides of the alkali metals. The bromide MnBr2.4H2O, iodide, Mn12, and fluoride, MnF2, are known. Manganous Sulphate, MnSO4, is prepared by strongly heating a See also:paste of pyrolusite and concentrated sulphuric acid until acid fumes cease to be evolved. The ferric and aluminium sulphates See also:present are thus converted into insoluble basic salts, and the residue yields manganous sulphate when extracted with water. The salt crystallizes with varying quantities of water, according to the temperature at which See also:crystallization is effected: between -4° C. and +6° C. with 7 H20, between 15° C. and 20° C. with 5H2O, and between25° C. and 31 ° C, with 4H2O. It crystallizes in large See also:pink crystals, the colour of which is probably due to the presence of a small quantity of manganic sulphate or of a See also:cobalt sulphate. It combines with the sulphates of the alkali metals to form double salts. Manganous Nitrate, .Mn(NO3)2.6H2O, obtained by dissolving the carbonate in nitric acid and concentrating the solution, crystallizes from nitric acid solutions in See also:long colourless needles, which melt at 25.8° C. and See also:boil at 129.5° C. with some decomposition. Manganous Carbonate, MnCO3, found native as manganese spar, may be prepared as an amorphous powder by heating manganese chloride with sodium carbonate in a sealed See also:tube to 150° C., or in the hydrated form as a white flocculent precipitate by adding sodium carbonate to a manganous salt.

In the moist condition it rapidly turns brown on exposure to air. Manganous Sulphide, MnS, found native as manganese glance, may be obtained by heating the monoxide or carbonate in a See also:

porcelain tube in a current of carbon bisulphide vapour. R. See also:Schneider (Pogg. Ann., 1874, 151, 449) obtained a crystalline variety by melting sulphur with anhydrous manganous sulphate and dry potassium carbonate, extracting the residue and drying it in a current of hydrogen. Four sulphides are known; the red and green are anhydrous, a See also:grey variety contains much water, whilst the pink is a mixture of the grey and red (J. C. Olsen and W. S. Rapalje, Jour. Amer. Chem.

Soc., 1904, 26, p. 1615). Ammonium sulphide alone gives incomplete precipitation of the sulphide. In the presence of ammonium salts the precipitate is dirty white in colour, whilst in the presence of See also:

free See also:ammonia it is a See also:buff colour. Thisform of the sulphide is readily oxidized when exposed in the moist condition, and is easily decomposed by dilute mineral acids. Manganese Disulphide, MnS2, found native as hauerite, is formed as a red coloured powder by heating manganous sulphate with potassium polysulphide in a sealed tube at 16o°—170° C. (H. v. See also:Senarmont, Jour. prak. Chem., 1850, 51, p. 385). Manganic Salts.—The sulphate, Mn2(SO4)2, is prepared by gradually heating at 138° C. a mixture of concentrated sulphuric and manganese dioxide until the whole becomes of a dark green colour. The excess of acid is removed by spreading the See also:mass on a porous See also:plate, the residue stirred for some hours with nitric acid, again spread on a porous plate, and finally dried quickly at about 130° C.

It is a dark green deliquescent powder which decomposes on heating or on exposure to moist air. It is readily decomposed by dilute acids. With potassium sulphate in the presence of sulphuric acid it forms potassium manganese See also:

alum, K2SO4•Mn2(SO4)3.24H2O. A. Piccini (Zeit. anorg. Chem. 1898, 17, p. 355) has also obtained a manganese See also:caesium alum. Manganic Fluoride, MnF3, a solid obtained by the action of See also:fluorine on manganous chloride, is decomposed by heat into manganous fluoride and fluorine. By suspending the dioxide in carbon tetrachloride and passing in hydrochloric acid gas, W. B. See also:Holmes (Abst.

J.C.S., 1907, ii., p. 873) obtained a black trichloride and a reddish-brown tetrachloride. Manganese See also:

Carbide, Mn3C, is prepared by heating manganous oxide with See also:sugar charcoal in an electric furnace, or by fusing manganese chloride and calcium carbide. Water decomposes it, giving methane and hydrogen (H. Moissan) ; Mn3C+6H2O = 3Mn(OH)2+See also:CH4+H2. Manganates.—These salts are derived from manganic acid H2MnO4. Those of the alkali metals are prepared by fusing manganese dioxide with sodium or potassium hydroxide in the presence of air or of some oxidizing agent (See also:nitre, potassium chlorate, &c.) ; MnO2+2KHO+0=K2MnO4+See also:H2O. In the See also:absence of air the reaction proceeds slightly differently, some manganese sesquioxide being formed; 3MnO2+2KHO=K2MnO4+Mn2O3+H2O. The fused mass has a dark See also:olive-green colour, and dissolves in a small quantity of cold water to a green solution, which is, however, only See also:stable in the presence of an excess of alkali. The green solution is readily converted into a pink one of permanganate by a large dilution with water, or by passing carbon dioxide through it: 3K2MnO4+2CO2= 2K2CO3+2KMnO4+MnO2. Permanganates are the salts of permanganic acid, HMnO4. The potassium salt, KMnO4, may be prepared by passing chlorine or carbon dioxide through an aqueous solution of potassium manganate, or by the electrolytic oxidation of the manganate at the anode [German patent 101710 (1898)].

It crystallizes in dark See also:

purple-red prisms, isomorphous with potassium perchlorate. It acts as a powerful oxidizing agent, both in acid and alkaline solution; in the first See also:case two molecules yield five atoms of available oxygen and in the second, three atoms: 2 KM nO4+3 H2SO4 = K2SO4+2M nSO4+3H2O+50 ; 2KMnO4+3H2O =2MnO2•H2O+2KHO+3O. It completely decomposes hydrogen peroxide in sulphuric acid solution 2K 1\4 n04+5H2O2+3H2SO4 = K2SO4+2 M nSO4+8H2O+502. It decomposes when heated to 200° — 240°C.: 2KMnO4=K2MnO4+MnO2+02; and when warmed with hydrochloric acid it yields chlorine: 2KMnO4+16HC1=2KCl+2MnCl2+8H2O+5C12. Sodium Permanganate, NaMnO4.3H2O (?), may be prepared in a similar manner, or by precipitating the See also:silver salt with sodium chloride. It crystallizes with See also:great difficulty. A solution of the crude salt is used as a disinfectant under the name of " Condy's fluid." Ammonium Permanganate, NH4•MnO4, explodes violently on rubbing, and its aqueous solution decomposes on boiling (W. Muthmann, Ber., 1893, 26, p. Io18); NH4•MnO4=MnO2+N2+2H2O. Barium Permanganate, BaMn2O8, crystallizes in almost black needles, and is formed by passing carbon dioxide through water containing suspended barium manganate. Detection.—Manganese salts can be detected by the See also:amethyst colour they impart to a See also:borax-See also:bead when heated in the Bunsen See also:flame, and by the green mass formed when they are fused with a mixture of sodium carbonate and potassium nitrate. Manganese may be estimated quantitatively by precipitation as carbonate, this salt being then converted into the oxide, Mn3O4 by ignition; or by precipitation as hydrated dioxide by means of ammonia and See also:bromine water, followed by ignition to Mn3O4• The valuation of pyrolusite is generally carried out by means of a See also:distillation with hydrochloric acid, the liberated chlorine passing through a solution of potassium iodide, and the amount of See also:iodine liberated being ascertained by means of a See also:standard solution of sodium thiosulphate.

The atomic weight of manganese has been frequently determined. See also:

Berzelius, by See also:analysis of the chloride, obtained the value 54.86; K. v. See also:Hauer (Sitzb. Akad. Wien., 1857, 25, p. 132), by See also:conversion of the sulphate into sulphide, obtained the value 54'78; J. See also:Dewar and A. See also:Scott (Chem. See also:News, 1883, 47, p. 98), by analysis of silver permanganate, obtained the value 55.e38; J. M. Weeren (See also:Stahl. u.

Eisen, 1893, 13, p. 559), by conversion of manganous oxide into the sulphate obtained the value 54.883, and of the sulphate into sulphide the value 54.876 (H = i), and finally G. P. See also:

Baxter and Hines (Jour. Amer. Chem. Soc., 1906, 28, p. 1360), by analyses of the chloride and bromide, obtained 54.96 (0 = i6).

End of Article: MANGANESE (symbol Mn; atomic weight, 54.93 (0=16)], a metallic chemical element. Its dioxide (pyrolusite)

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