Chromium

Description

Hard, brittle metallic element that takes a high polish. Chromium was discovered as an element in 1797 by Louis-Nicholas Vauquelin of France. It has an abundance of 122 parts per million in the earth's crust. It is primarily found as the ore chromite. Chromium is added to steel alloys to increase hardness and corrosion resistance (see Stainless steel). It is also used for plating other metals since it readily forms a thin oxide surface layer that resists corrosion (see Chrome plate). Chromium salts are used as pigments in paint and glass, as mordants for dyeing textiles, for tanning leather and as wood preservatives. Some chromium salts, such as chromium acetate, exhibit an alexandrite effect where there appear red in concentrated solutions and green in dilute solutions.

Synonyms and Related Terms

Cr; Chroom (Ned.); chrome (Fr.); Chrom (Deut.); cromo (It., Esp.); crómio (Port.); Krom (Sven.) 

Other Properties

Soluble in alkalis and acids except for nitric. Insoluble in water. Body-centered cubic structure.

Diphenylcarbazide solution is used for the colorimetric detection of chromium in metals, tanned leathers and pigments (Odegaard et al 2000)

Composition	Cr (atomic no. 24)
CAS	7440-47-3
Mohs Hardness	9.0
Melting Point	1903
Density	7.14
Molecular Weight	atomic wt = 51.996
Boiling Point	2642

Hazards and Safety

Toxic by inhalation of dust. Skin contact may cause irritation. Chromium salts are toxic by ingestion. Carcinogenic.

LINK: International Chemical Safety Card

Additional Information

° N.Odegaard, S.Carroll, W.Zimmt, Material Characterization Tests for Objects of Art and Archaeology Archetype Publications, London, 2000, p.44.

° Web Elements: Website

Authority

• Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976

• Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997

• The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998

• N.Odegaard, S.Carroll, W.Zimmt, Material Characterization Tests for Objects of Art and Archaeology, Archetype Publications, London, 2000

• Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993

• The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 2288

• G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 193

• Dictionary of Building Preservation, Ward Bucher, ed., John Wiley & Sons, Inc., New York City, 1996

• Hermann Kuhn, Conservation and Restoration of Works of Art and Antiquities, Butterworths, London, 1986

• Tom Rowland, Noel Riley, A-Z Guide to Cleaning, Conserving and Repairing Antiques, Constable and Co., Ltd., London, 1981

• Michael McCann, Artist Beware, Watson-Guptill Publications, New York City, 1979