Preparation of elemental silicon
Silicon is prepared by reduction of silica (sand) with aluminium.
The reaction, mixture consists of 90 g of dried sand, 100 g of aluminum powder and 120 g of flowers of sulfur, all thoroughly mixed and placed in a clay crucible imbedded in sand. The reaction is started with a thin layer of magnesium powder and a fuse of magnesium ribbon. Much sulfur dioxide escapes during the process: the necessary heat is generated by the reaction between the aluminum and the sulfur. The broken pieces of slag are treated with water under the hood to hydrolyze the aluminum sulfide; the hydrous aluminum oxide and crystalline alumina are easily separated from the grey-black metallic regulus and smaller globules of silicon.
The metal is allowed to stand with concentrated hydrochloric acid for several days with occasional renewal of the latter until all the excess aluminum has dissolved, leaving a loose mass of silicon leaflets. The crystalline mass is boiled for two hours with more of the acid, drained, and then transferred to a platinum or plastic beaker. The product is treated with 10 ml portions of concentrated hydrofluoric acid until no more silica dissolves and then drained, washed well with water, and dried at 100°C. Yield 20-25 g.
Inorganic laboratory preparations, by G. G. Schlessinger, 2, 1962
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SILANE, Silicane, Silicones, Silicon hydride, Silicon, isotope of mass 31, BLRPTPMANUNPDV-UHFFFAOYSA-N, EPA-E5244751, CID5461123, D012825, D012828, SI, 13825-90-6