Contents |
History
(Gr. chroma: color) Discovered in 1797 by Vauquelin, who prepared the metal in the following year, chromium is a steel-gray, lustrous, hard metal that takes a high polish.[1]
Sources
The principal ore is chromite, which is found in Zimbabwe, Russia, New Zealand, Turkey, Iran, Albania, Finland, Democratic Republic of Madagascar, and the Phillippines. The metal is usually produced by reducing the oxide with aluminum.[1]
Properties
| General |
|---|
| Name : chromium |
| Symbol : Cr |
| Atomic Number : 24 |
| Chemical Series : Transition Metal |
| Block, Period : 6, 4 |
| Appearance : silvery |
| Atomic Properties |
| Atomic Weight : 51.9961 |
| Covalent Radius (pm) : 127 |
| Physical Properties |
| Matter : presumably a solid (antiferromagnetic) |
| Density (kg/ |
| Hardness : 8.5 |
| Melting Point (K) : 2130 |
| Boiling Point (K) : 2945 |
| Evaporation Heat (kJ/mol) : 344.3 |
| Fusion Heat (kJ/mol) : 16.9 |
| Specific Heat (J/(kg*K) ) : 450 |
| Miscellaneous |
| Electrical Conductivity ( |
| Thermal Conductivity (W/(m*K) ) : 93.7 |
Uses
Chromium is used to harden steel, manufacture stainless steel, and form many useful alloys. It is mostly used in plating to produce a hard, beautiful surface and to prevent corrosion. Chromium gives glass an emerald green color and is widely used as a catalyst.
The refractory industry uses chromite for forming bricks and shapes, as it has a high melting point, moderate thermal expansion, and stability of crystalline structure.[1]
Compounds
All compounds of chromium are colored. The most important chromates are those of sodium and potassium, the dichromates, and the potassium and ammonium chrome alums. The dichromates are used as oxidizing agents in quantitative analysis, also in tanning leather.
Other compounds are of industrial value; lead chromate is chrome yellow, a valued pigment. Chromium compounds are used in the textile industry as mordants, and by the aircraft and other industries for anodizing aluminum.[1]
Handling
Chromium compounds are toxic and should be handled with proper safeguards.[1]
Notes
[1] From Los Alamos National Laboratory's Chemistry Division Website
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