Chromium trioxide

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Description

Dark, violet-red deliquescent crystals. Chromium trioxide is normally used as an aqueous solution which is commonly called chromic acid. Chromic acid is made by mixing potassium dichromate and an acid such as hydrochloric acid or sulfuric acid. It is an extremely strong oxidizing agent that will react violently with any organic compound. For many years, chromic acid was used in chemical laboratories cleaning baths to remove all traces of organic residues from glassware (see Beckmann mixture). Chromic acid is also used for chrome plating baths, engraving etching, tanning, and as a colorant in glass and ceramics.

Synonyms and Related Terms

chromic acid; chromic anhydride; chromium (VI) oxide; anhydride chromique (Fr.); anidride cromica (It.); Chromsaeureanhydrid (Deut.); Chromtrioxid (Deut.); chroomtrioxyde (Ned.);

Chemical structure

Chromium trioxide.jpg


Other Properties

Soluble in water, ethanol, mineral acids.

Composition CrO3
CAS 1333-82-0
Melting Point 197
Density 2.70
Molecular Weight mol. wt. = 100.01
Boiling Point 250 (dec)

Hazards and Safety

Powerful oxidizing agent, may explode on contact with reducing agents.

Toxic by ingestion. Contact will corrode skin and membranes. Carcinogenic. Hygroscopic. Corrodes steel, copper and alloys. Dcomposition produces toxic fumes.

LINK: International Chemical Safety Card

Sources Checked for Data in Record

  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 192
  • 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 2283
  • Website address 1 Comment: www.hants.org.uk/museums - conservation termlist
  • Susan E. Schur, Conservation Terminology: A review of Past & Current Nomenclature of Materials, Technology and Conservation, Spring (p.34-39); Summer (p.35-38); Fall (p.25-36), 1985
  • Michael McCann, Artist Beware, Watson-Guptill Publications, New York City, 1979