SILICON (Neo-Lat., from Lat. si/ca, flint), or SILICIUM. A non-metallic element discovered by Berzelius in 1S23. Among the ancients minerals .rich in silica were used in glass-making, and Becher contended that they contained a pecu liar kind of earth, to which he gave the name terra ritreseibilis. In the seventeenth century it was found that such minerals did not change when heated by themselves, and only formed a fusible glass when brought. in contact with other bodies. In 1000 Tachenius showed that it. pos ressed acid rather than alkaline properties, as it combined with alkalies, but the true nature of silica remained unknown until Davy demon strated it in the early part of the nineteenth century. Silicon is the most abundant of all elements in the solid earth's crust, with the ex ception of, oxygen. It is never found in the iso lated state. but occurs in combination with oxy gen as silicon dioxide or silica (quartz, flint, sand, etc.). and in various minerals in the form of metallic silicates. It is also found in mineral springs and in sea water. It was originally pre pared by Berzelius by decomposing potassium silieolluoride by means of potassium in an iron tube at a red heat. When allowed to cool, the mass was treated with water, which dissolved the potassium fluoride, leaving silicon in the form of an amorphous brown powder. This method is still used. but with the substitution of sodium for potassium. The element may also be obtained by the electrolysis of a fused mix ture of potassium fluoride and silienflooride. A graphitoidal modification of silicon is recognized by some, and may be produced by heating amorphous silicon in a platinum crucible; while a third modification, known as crystalline or adamantine silicon. is formed by beating in an
earthenware crucible a mixture of three parts of potassium fluosilicate. one part of sodium in small pieces. and four parts of granulated zinc.
Silicon (symbol Si; atomic weight, 28.40), when in an amorphous condition, is a lustrous brown powder. which does not conduct electric ity and is fusible in a non-oxidizing atmosphere at a temperature between the melting-points of steel and cast iron. The graphitoidal modifica tion consists of shining metallic scales; while crystalline silicon is obtained in the form of grayish-black metal-like leaflets or needles, with a specific gravity of 2.19, and a melting-point between 1100° and 1300° C. Silicon combines directly with a number of the elements, forming silicidcs. With oxygen silicon combines to form only one oxide, the dioxide, or silica (Si0„.), which is an important constituent of the solid crust of the earth and may he artificially pre pared by burning silicon in air or oxygen. As flint and as sand it has many applications in the arts, as in the manufacture of glass, pottery, etc. Silicon unites with the halogens. Thus, with fluorine, it forms a silicon tetrafluoride, which is a colorless gas that combines with water, forming hydrofluosilicic acid, which in turn unites with bases to form salts known as silieo fluorides.