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BAUXITE

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Originally appearing in Volume V03, Page 543 of the 1911 Encyclopedia Britannica.
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BAUXITE , a substance which has been considered to be a See also:

mineral See also:species, having the See also:composition Al20(OH)4 (corresponding with alumina 73.9, See also:water 26.1%), and thus to be distinct from the crystallized See also:aluminium hydroxides, See also:diaspore (AlO(OH)) and gibbsite (= hydrargillite, Al(OH)3). It was first described by P. See also:Berthier in 1821 as " alumine hydratee de See also:Beaux," and was named beauxite by P. A. Dufrenoy in 1847 and bauxite by E. H. Sainte-Claire Deville in 1861; this name being derived from the See also:original locality, the See also:village of See also:Les Baux (or Beaux), near See also:Arles, dep. Bouches-du-See also:Rhone in the See also:south of See also:France, where the material has been for many years extensively See also:mined as an ore of aluminium. It is never found in a crystallized See also:state, but always as earthy, See also:clay-like or concretionary masses, often with a pisolitic structure. In See also:colour it varies from See also:white through yellow and See also:brown to red, depending on the amount and the degree of hydration of the See also:iron See also:present. The specific gravity also varies with the amount of iron; that of the variety known as wocheinite (from near See also:Lake Wochein, near Radmannsdorf, in See also:northern See also:Carniola) is given as 2.55. The numerous chemical analyses, which have mostly been made for technical purposes, show that material known as bauxite varies very widely in composition, the maximum and minimum percentages of each constituent being as follows: alumina (Al203) 33.2—76.9; water (H20) 8.6—31.4; iron See also:oxide (Fe2O3) 0.1—48.8; See also:silica (SiO2) o•3—37.8; titanic See also:acid (TiO2) up to 4.

The material is thus usually very impure, being mixed with clay, See also:

quartz-See also:sand and hydroxides of iron in variable amounts, the presence of which may be seen by a microscopical examination. Analyses of purer material often approximate to diaspore or gibbsite in composition, and See also:minute crystalline scales of these minerals have been detected under the See also:microscope. Bauxite can therefore scarcely be regarded as a See also:simple mineral, but rather as a mixture of gibbsite and diaspore with various impurities; it is in fact strikingly like See also:laterite, both in chemical composition and in microscopical structure. Laterite is admittedly a decomposition-product of igneous or other crystalline rocks, and the same is no doubt also true of bauxite: The deposits in Co. See also:Antrim occur with pisolitic iron ore inter-bedded with the See also:Tertiary basalts, and similar deposits are met with in connexion. with the basaltic rocks of the Westerwald in See also:Germany. On the other See also:hand, the more extensive deposits in the south of France (departments Bouches-du-Rhone, See also:Ariege, See also:Herault, See also:Var) and the See also:southern See also:United States (See also:Georgia, See also:Alabama, See also:Arkansas) are often associated with limestones; in this See also:case the origin of the bauxite has been ascribed to the chemical See also:action of solutions of aluminium sulphate on the limestones. Bauxite is of value chiefly as a source of metallic aluminium (q.v.); the material is first purified by chemical processes, after which the aluminium hydroxide is reduced in the electric See also:furnace. Bauxite is also largely used in the manufacture of See also:alum and other aluminium salts used in See also:dyeing. Its refractory qualities render it available for the manufacture of See also:fire-bricks and crucibles. (L. J.

End of Article: BAUXITE

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