Formic acid

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A colorless, fuming liquid with a strong pungent odor. Formic acid occurs naturally in the poison of stinging ants and in stinging nettles. In air, Formaldehyde will oxidize slowly to form formic acid. Formic acid is a strong reducing agent and will react quickly with most materials. It is deleterious to metals and may harm oil paintings, watercolors, drawing, and sketches. Formic acid is sold commercially as an aqueous solution. It is used industrially in animal feeds, textile dyeing, leather tanning and in the production of insecticides, rubber, and refrigerants. In textile dyeing, formic acid is used to assist in the absorption of Chromium mordants. Formic acid may evolve from wood products, linoleum, and any coatings formed by oxidative polymerization (Tétreault 2017).

  • See Pollutant record for a comparison table of aerosols and collection risks.

Synonyms and Related Terms

hydrogen carboxylic acid; methanoic acid; aminic acid; formylic acid

Personal Risks

  • Combustible. Flash point = 69 C.
  • Inhalation and skin contact will cause irritation and burns.
  • ThermoFisher: SDS

Collection Risk

  • Will corrode metals.
  • Reacts with daguerreotypes
  • Darkens lead white pigments
  • May yellow porous materials such as paper and fabrics

Physical and Chemical Properties

Miscible with water, ether, acetone, ethyl acetate, methanol, ethanol. Partially soluble in benzene, toluene, xylenes.

pH (0.1 N aqueous solution) = 2.3

Composition HCOOH
CAS 64-18-6
Melting Point 8.4 C
Density 1.220 g/ml
Molecular Weight mol. wt. = 46
Boiling Point 100.8 C


Properties of Common Solvents

Resources and Citations

  • Jean Tétreault, 'Products used in Preventive Conservation' Technical Bulletin #2, CCI, 2017. Link
  • 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 #4268
  • Matt Roberts, Don Etherington, Bookbinding and the Conservation of Books: a Dictionary of Descriptive Terminology, U.S. Government Printing Office, Washington DC, 1982
  • S.R.Trotman, E.R. Trotman, Textile Analysis, J.B. Lippincott Company, Philadelphia, 1932 Comment: specific gravity = 1.241
  • John and Margaret Cannon, Dye Plants and Dyeing, Herbert Press, London, 1994
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
  • 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
  • CRC Handbook of Chemistry and Physics, Robert Weast (ed.), CRC Press, Boca Raton, Florida, v. 61, 1980 Comment: pH (0.1 N aqueous solution) = 2.3