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Written by tom
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Wednesday, 25 June 2008 |
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A bluish-white metal, symbol Sb, having a crystalline scale-like structure. It is brittle and easily reduced to powder. It is neither malleable nor ductile and is used only in alloys or in its chemical compounds. Like arsenic and bismuth, it is sometimes referred to as a metalloid, but in mineralogy it is called a semimetal. It does not have the free cloudlike electrons that occur in metal atoms, and thus it lacks plasticity and is a poor conductor of electricity.
The chief uses of antimony are in alloys, particularly for hardening lead-base alloys. The specific gravity of the metal is 6.62, melting point 824oF (440oC), and Brinell hardness 55. It burns with a bluish light when heated to redness in the air. Antimony imparts hardness and a smooth surface to soft-metal alloys; and alloys containing antimony expand on cooling, thus reproducing the fine details of the mold. This property makes it valuable for type metals. When alloyed with lead, tin, and copper, it forms the babbitt metals used for machinery bearings. It is also much used in white alloys for pewter utensils. Its compounds are used widely for pigments. Antimony red is the common name of antimony trisulfide, Sb2S5, also known as antimony sulfide and antimony sulfuret, found in the mineral stibnite, but produced by precipitation from solutions of antimony salts. It comes in orange-red crystals with a specific gravity of 4.56 and melting point 1015oF (545oC). It is used as a paint pigment, for coloring red rubber, and in safety matches. Antimony pentasulfide, Sb2S5, an orange-yellow powder, was once used for vulcanizing rubber, and it colored the rubber red.
It breaks down when heated, yielding sulfur and the red pigment antimony trisulfide. |
