Ammonium Permanganate, NH4·MnO4, explodes violently on rubbing, and its aqueous solution decomposes on boiling (W. Muthmann, Ber., 1893, 26, p. 1018); NH4·MnO4 = MnO2 + N2 + 2H2O.
Barium Permanganate, BaMn2O3, 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 amethyst colour they impart to a borax-bead when heated in the Bunsen 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 bromine water, followed by ignition to Mn3O4. The valuation of pyrolusite is generally carried out by means of a distillation with hydrochloric acid, the liberated chlorine passing through a solution of potassium iodide, and the amount of iodine liberated being ascertained by means of a standard solution of sodium thiosulphate.
The atomic weight of manganese has been frequently determined. J. Berzelius, by analysis of the chloride, obtained the value 54.86; K. v. Hauer (Sitzb. Akad. Wien., 1857, 25, p. 132), by conversion of the sulphate into sulphide, obtained the value 54.78; J. Dewar and A. Scott (Chem. News, 1883, 47, p. 98), by analysis of silver permanganate, obtained the value 55.038; J. M. Weeren (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 = 1), and finally G. P. Baxter and Hines (Jour. Amer. Chem. Soc., 1906, 28, p. 1360), by analyses of the chloride and bromide, obtained 54.96 (O = 16).
MANGANITE, a mineral consisting of hydrated manganese sesquioxide, Mn2O3·H2O, crystallizing in the orthorhombic system and isomorphous with diaspore and göthite. Crystals are prismatic and deeply striated parallel to their length; they are often grouped together in bundles. The colour is dark steel-grey to iron-black, and the lustre brilliant and submetallic: the streak is dark reddish-brown. The hardness is 4, and the specific gravity 4.3. There is a perfect cleavage parallel to the brachypinacoid, and less perfect cleavage parallel to the prism faces m. Twinned crystals are not infrequent. The mineral contains 89.7% of manganese sesquioxide; it dissolves in hydrochloric acid with evolution of chlorine. The best crystallized specimens are those from Ilfeld in the Harz, where the mineral occurs with calcite and barytes in veins traversing porphyry. Crystals have also been found at Ilmenau in Thuringia, Neukirch near Schlettstadt in Alsace (“newkirkite”), Granam near Towie in Aberdeenshire, Upton Pyne near Exeter and Negaunee in Michigan. As an ore of manganese it is much less abundant than pyrolusite or psilomelane. The name manganite was given by W. Haidinger in 1827: French authors adopt F. S. Beudant’s name “acerdèse,” (Gr. ἀκερδής, unprofitable) because the mineral is of little value for bleaching purposes as compared with pyrolusite.
(L. J. S.)
MANGBETTU (Monbuttu), a negroid people of Central Africa living to the south of the Niam-Niam in the Welle district of Belgian Congo. They number about a million. Their country is a table-land at an altitude of 2500 to 2800 ft. Despite its abundant animal life, luxuriant vegetation and rich crops of plantain and oil-palm, the Mangbettu have been some of the most inveterate cannibals in Africa; but since the Congo State established posts in the country (c. 1895) considerable efforts have been made to stamp out cannibalism. Physically the Mangbettu differ greatly from their negro neighbours. They are not so black and their faces are less negroid, many having quite aquiline noses. The beard, too, is fuller than in most negroes. They appear to have imposed their language and customs on the surrounding tribes, the Mundu, Abisanga, &c. Once a considerable power, they have practically disappeared as far as the original stock is concerned; their language and culture, however, remain, maintained by their subjects, with whom they have to a large extent intermixed. The men wear bark cloth, the art of weaving being unknown, the women a simple loin cloth, often not that. Both sexes paint the body in elaborate designs. As potters, sculptors, boatbuilders and masons the Mangbettu have had few rivals in Africa. Their huts, with pointed roofs, were not only larger and better built, but were cleaner than those of their neighbours, and some of their more important buildings were of great size and exhibited some skill in architecture.