antimony

antimony [Lat. antimoneum ], semimetallic chemical element; symbol Sb [Lat. stibium, =a mark]; at. no. 51; at. wt. 121.75; m.p. 630.74°C; b.p. 1,750°C; sp. gr. (metallic form) 6.69 at 20°C; valence 0, +3, -3, or +5. Antimony exists in two allotropic forms (see allotropy ); the more common is silvery blue-white and has a rhombohedral crystalline structure. It is a poor conductor of heat and electricity and is brittle and easily powdered. It is primarily used in alloys and chemical compounds. It is a member of Group 15 of the periodic table . Antimony rarely occurs free in nature, but its ores are widely distributed. The principal ore is stibnite , a sulfur compound known since early times; there are extensive deposits in China. Antimony is often found in other ores as well, e.g., silver, copper, and lead. The pure element antimony is produced from the ore by roasting it to form the oxide, then reducing the oxide with carbon or iron; often a flux of sodium sulfate or sodium carbonate is used to prevent loss of molten antimony by evaporation. Antimony does not react with air or water at room temperature; it does react with fluorine, chlorine, or bromine and is soluble in hot nitric or sulfuric acid; at higher temperatures, antimony will ignite and burn in air. It unites with hydrogen to form stibine, a poisonous gas. In combination with metals antimony forms alloys that are hard and brittle and have low melting points. The alloys of antimony include britannia metal , type metal , Babbitt metal , and sometimes pewter ; these alloys expand on cooling, thereby retaining fine details of a mold. Alloys and compounds of antimony are used in bearings, storage batteries, safety matches, and as a red pigment in paint. Although antimony and many of its compounds are toxic, tartar emetic (potassium antimonyl tartrate) is used as a medicine. Small concentrations of antimony can be detected by a method similar to the Marsh test for arsenic. Antimony is mixed with soot and other substances to make kohl, used for centuries by women in some countries as an eye cosmetic. A method for the extraction of antimony from stibnite was first described c.1600 by Basilius Valentinus. Although known to the ancients, the element was first adequately described by Nicolas Lémery in 1707.

antimony Toxic metal of no known metabolic function, and therefore not a dietary essential. Antimony compounds are used in treatment of some parasitic diseases.

antimony XV. — medL. antimōnium.