Title: Diamond
CAS Registry Number: 7782-40-3
Literature References: A crystalline form of carbon. Mined as a mineral, principally in South Africa. (Non-commercial) synthesis from other carbon compds (e.g., lignin) by means of elevated temperatures (about 2700°) and pressures (about 800,000 lbs/sq inch): Desch, Nature 152, 148 (1943); Neuhaus, Angew. Chem. 66, 525 (1954); Hall, Chem. Eng. News 33, 718 (1955); Bridgman, Sci. Am. 1955, 46; Hall, J. Chem. Educ. 38, 484 (1961); Bundy, Ann. N.Y. Acad. Sci. 105, 951-982 (1964). Books: S. Tolansky, History and Use of Diamond (London, 1962) 166 pp; R. Berman, Physical Properties of Diamond (Oxford, 1965) 442 pp.
Properties: Face-centered cubic crystal lattice. Burns when heated with a hot enough flame (over 800°, oxygen torch). d425 3.513. nD20 2.4173. Hardness = 10 (Mohs' scale). Sp heat at 100 K: 0.606 cal/g-atom/K. Entropy at 298.16 K: 0.5684 cal/g-atom/K. Band gap energy: 6.7 ev. Dielectric constant 5.7. Electron mobility: ~1800 cm2/v-sec. Hole mobility: 1200 cm2/v-sec. Can be pulverized in a steel mortar. Attacked by laboratory-type cleaning soln (potassium dichromate + concd H2SO4). In the jewelry trade the unit of weight for diamonds is one carat = 200 mg. Ref: Wall Street J. 164, no. 36, p 10 (Aug 19, 1964).
Index of refraction: nD20 2.4173
Density: d425 3.513
Use: Jewelry. Polishing, grinding, cutting glass, bearings for delicate instruments; manuf dies for tungsten wire and similar hard wires; making styli for recorder heads, long-lasting phonograph needles. In semiconductor research. |