We continue to review some of the most important materials in heat treatment and metallurgy.
Antimony (chemical symbol: Sb)
Antimony is a brittle, bright, shiny metalloid. Metalloids have properties of both metals and nonmetals and are electrical semiconductors. As such, antimony is a weak conductor of heat and electricity. Compounds of antimony have been known since ancient times, and powdered versions were used in medicine as a laxative and for use in cosmetics (i.e., ancient eyeliner, known as khol). Today, antimony is used in many commercial and consumer products, including paint, batteries, bullets, clothing, glass, children's toys and plastic bottles.
Italian metallurgist Vannoccio Biringuccio was the first to identify antimony. He was an influential figure considered by many to be the father of the foundry industry. He published “De la Pirotechnia,” the first printed record of proper foundry practice. The document also explains the mining and refining of brass, silver, gold and many other metals. In 1540, Biringuccio wrote a paper titled "Concerning Antimony and Its Ore," in which he describes antimony sulfide (stibnite) for the first time. He notes that upon heating the antimony sulfide it produces a substance that "although this is very white and almost more shining than silver, it is much more brittle than glass." This is a clear description of the element antimony.
The name antimony is derived from two Greek words: “anti” (not) and “monos” (alone). It is so named because antimony is seldom found in its elemental form. It is typically combined with sulfur or with heavier metals such as copper, lead and silver. Antimony’s periodic element symbol of Sb is derived from stibnite, a common compound of antimony and sulfur.
Antimony’s most valuable metallurgical use is as an alloying agent of lead, to which it imparts increased hardness and yield strength. In fact, lead is almost always alloyed with antimony to some extent. In lead–acid batteries it improves lead plate strength and charging properties. It is used in antifriction bushings (such as Babbitt metal), pewter, lead shot/bullets, solder and electrical-cable sheathing to name a few. Non-metallurgical uses for antimony are in flame-retardants for children's clothing, toys, aircraft and automobile seat covers. Antimony is also important in glass processing and pigment production, and it has been used since the 1950s as a dopant for semiconductors.
Here are a few important facts about antimony.
- Atomic number: 51
- Atomic weight: 121.760
- Melting point: 903.78 K (630.63°C or 1167.13°F)
- Boiling point: 1860 K (1587°C or 2889°F)
- Density: 6.685 grams per cubic centimeter
- Phase at room temperature: Solid
- Element classification: Semi-metal
- Period number: 5
- Group number: 15
- Group name: Pnictogen
- Vannoccio Biringuccio, The Pirotechnia of Vannoccio Biringuccio, translated by Cyril Stanley Smith and Martha Teach Gnudi, (1990) p. 201, Dover Publications
- Jefferson Lab (https://www.jlab.org)