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Page:Popular Science Monthly Volume 44.djvu/410

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THE POPULAR SCIENCE MONTHLY.

and this, in turn with its earthy appearance, is oxide of aluminum. This metal, therefore, constitutes nearly a sixth part of the soil on which we spend our lives. The most abundant of all the metals, it is at the same time the one that is nearest to us. Thus alumina, and consequently aluminum, is literally under our feet—clay, of which it is the principal component, being found nearly everywhere. Rarely, and scattered in the masses of the rocks, precious gems may be found—emeralds, amethysts, sapphires, rubies, and topazes—which are only alumina, nearly pure in corundum, but alloyed with a little magnesia or lime in spinel.

It was not till modern chemistry was born that it became possible to separate aluminum from its earth. Carbon, which had been the chief agent for isolating the known metals from oxygen, was not effective in separating the elements of alumina; and even the electrical process with which Sir Humphry Davy produced sodium and potassium failed here. A roundabout process was devised. Oersted converted the intractable oxides of aluminum and magnesium, also not yet conquered, into chlorides, and Woehler decomposed them with potassium, taking advantage of the superior affinity of that metal for chlorine. Applying potassium to chloride of aluminum in the crucible, he obtained metallic aluminum and chloride of potassium. It appeared as a grayish dust, with a few globules, the largest of which was not bigger than a pinhead. From this small quantity only an incomplete determination of the properties of the element could be made. A more exact description was reserved for Henri Sainte-Claire Deville, who repeated Woehler's experiment in 1854. For the rare, expensive, difficult, and somewhat dangerous potassium he substituted sodium, which he found a simple method of extracting from sea salt; and instead of clay, the use of which required a preliminary separation of the silica and the alumina, he employed hydrated alumina, known as bauxite, of which considerable beds were worked in France for the manufacture of alum. Under the direct action of chlorine, a mixture of bauxite and sea salt became a double chloride of sodium and aluminum. The addition to this mixture, at the melting point, of the proper quantity of sodium, caused a separation of the aluminum, which collected in the bottom of the crucible. By remelting, the metal was cleared of most of its impurities and greater cohesion was given to its molecules, so that it could be cast into ingots. All this involved great expense, and the investigation could not have been effectively continued had not Napoleon III come to the chemist's aid with some of the unlimited funds of which he had the control. The next year, June 18, 1855, Jean Baptiste Dumas presented to the Academy of Sciences the first ingot of aluminum made in an industrial shop.