Ferric chloride

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A hygroscopic, brown solid used as an etchant in photoengraving as a mordant to produce a clean vertical edge. Ferric chloride is also used as a mordant in textile dyeing and as a brown pigment in paints and inks. An acidified solution of iron chloride is also used as a reagent to qualitatively test for the presence of arsenic or phosphorus in copper alloys (Odegaard et al 2000).

Synonyms and Related Terms

iron (III) chloride; ferric trichloride; ferric perchloride; iron chloride; iron trichloride; iron perchloride; Flores Martin; Eisen(III)chlorid (Deut.); chlorure de fer (III) (Fr.);



Chemical structure

Ferric chloride.jpg

Other Properties

Soluble in water, ethanol, ether, acetone. Insoluble in ethyl acetate. Solid is deliquescent forming hexahydrate compound. Dissolution in water is exothermic and produced an acidic solution.

Composition FeCl3
CAS 7705-08-0
Melting Point 306
Density 2.90
Molecular Weight mol. wt. = 162.21
Boiling Point 315-316

Hazards and Safety

Noncombustible. Toxic by ingestion and inhalation. The corrosive, acidic compound will causes burns on contact. Decomposes in heat to form hydrogen chloride gas.

Mallinckrodt Baker: MSDS

Additional Information

N.Odegaard, S.Carroll, W.Zimmt, Material Characterization Tests for Objects of Art and Archaeology Archetype Publications, London, 2000, p. 42.

Sources Checked for Data in Record

  • Ralph Mayer, A Dictionary of Art Terms and Techniques, Harper and Row Publishers, New York, 1969 (also 1945 printing)
  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • Michael McCann, Artist Beware, Watson-Guptill Publications, New York City, 1979
  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 4061
  • N.Odegaard, S.Carroll, W.Zimmt, Material Characterization Tests for Objects of Art and Archaeology, Archetype Publications, London, 2000