Aluminium or Aluminum

ALUMINIUM or ALUMINUM, a metallic element which owes its name to the Romans, who called certain salts, now be lieved to be the mixed sulphates of iron and aluminium, alumen. These salts were found in the volcanic districts washed by the Mediterranean and were much used in medicine and the dyer's art. In the 18th century it was first recognized that a salt with similar properties could be produced from clays by the action of sulphuric acid ; and the base contained in clay, from which it was realized that this salt must be derived, was, in France, at first called terre argilleuse, but later alumine. In England this became alumina, whilst the Germans adhered and still adhere to the word Thonerde. Sir Humphry Davy, although he failed to isolate the metal of which it had been recognized that alumina was the oxide, suggested aluminum as a suitable name for it, a name still used in America, but elsewhere converted to the more euphonious aluminium (symbol Al, atomic number 13, atomic weight 27.1).

Occurrence and Ores.

Aluminium is not found in a metallic state in nature, a fact sufficiently explained by its great affinity for oxygen. Combined, however, it is one of the most widespread of the elements, only oxygen and silicon being more abundant in the earth's crust, of which it is computed that aluminium f orms a 13th part. Its compounds exist in many forms, from moun tainous masses to rare gems. Of these may be named the oxides, corundum, ruby and sapphire ; their hydrates, gibbsite and baux ite ; and their compounds with magnesium and beryllium, spinell and chrysoberyl respectively. The double fluoride of aluminium and sodium, cryolite or "ice-stone" is found in southern Green land as a vast dyke in porphyritic granite. The sulphate of aluminium occurs in many volcanic districts, whilst, in combina tion with the sulphates of the alkali metals, it forms the natural alums. Of the phosphates only turquoise need be cited, whereas the silicates include such diverse materials as the micas and clays, garnets, topaz, the felspars, etc. Many natural waters con tain alumina, sometimes in considerable proportions, whilst it is found in the ash of numerous plants.

Despite this wide distribution the ore from which the metal is to-day derived is, with few exceptions, the hydrate bauxite, itself a decomposition product of silicate containing rocks, such as the granites, basalts, syenites, etc. Vast deposits of this material, suitable for the extraction of the metal, have now been located in every continent, so that a shortage is unlikely for many years to come. Yet continuous efforts (and some apparently on the point of success) are directed to making such silicates as felspar, china clay and the leucites available for the purpose. Finally, we must note that cryolite, either natural or artificial, though not an ore, is indispensable in the present commercial production of the metal.