alumian

[Lat. alumin (is); suff. -an.] A mineral cla ed by Dana with his Crocoite group of Anhydrous "Sulphates, Chromates, Tellurates." It is white and sub-translucent. It consists of sulphuric acid, 60-9; alumina, 39.1. It is found in Spain. al-u-min-a, tal-u-mine, s. [In Fr. alumine; from Lat. alumina, pl. of alumen = alum.] 1. Chem. The only oxide of aluminium known. Its sp. gr. is 39. It is isomorphic with ferric and chromic oxides. It occurs native in crystals, as corundum, ruby, sapphire, and le pure as emery. It is the hardest substance known except the diamond. It can be obtained by precipitating a salt of aluminium by ammonia and igniting the precipitate. It is nearly insoluble in most acids. It is a white, insoluble, tastele , amorphous powder. Three hydrates are known, Al2O3. H2O, Al2O3. 2H2O, and Al2O3.3H2O; the trihydrate is the ordinary gelatinous precipitate. It is soluble in acids and fixed alkalies. It is a weak base, many of its salts having an acid reaction. It is largely used in dyeing as a mordant. It forms insoluble compounds with vegetable colours called lakes . It occurs native as Gibbsite. The monohydrate is Dias pore. The dihydrate cannot act as a mordant; it is soluble in acetic acid. (See Watts's Dict. Chem.) Silicate of aluminium forms the basis of clays. 2. Mineralogy. Aluminium, sometimes called argil, or the argillaceous earth, is the basis of all clays, and imparts to them the plastic character for which they are distinguished. For the aspects which it presents when it occurs native, see No. 1. It enters into the composition of many minerals, the proportion in which it occurs being generally stated just after that of the silica; thus, garnet taken from the Ural Mountains has silica 36-86, and alumina 24-19. Cupreous Phosphate of Alumina : A mineral, called also A mph it halite (q.v.). Fluate of Alumine : A mineral, called also Fluellite (q.v.). Fluosilicate of Alumina : A mineral, called also Topaz (q.v.). Hydrate of Alumina : A mineral, called also Diaspore (q.v.). Hydrosulphate of Alumina : A mineral, called also Aluminite (q.v.). Hydrous Phosphate of Alumina and Lime: A mineral, a variety of A mph it halite (q.v.). Mellite of Alumina: A mineral, now called simply Mellite (q. v.). Native Carbonate of Alumina and Lime : A mineral, called also Hovite (q.v.). IMG:content-0427.png:[graphic] 174 Sub phosphate of Alumina : A mineral, called also Wavellite (q.v.). Sulphate of Alumina: A mineral, called also (1) Alumian, (2) Alunogen, and (3) Felsobanyite (q.v.).