Formic Acid

Title: Formic Acid
CAS Registry Number: 64-18-6
Additional Names: Ameisensäure (German)
Molecular Formula: CH2O2
Molecular Weight: 46.03
Percent Composition: C 26.09%, H 4.38%, O 69.52%
Line Formula: HCOOH
Literature References: Found in the bites and stings of various insects including bees and ants; metabolite of methanol. Observed by S. Fisher in 1670 in the products resulting from the distillation of ants. Production: P. G. Jessop et al., Nature 368, 231 (1994). Acute and chronic toxicity: G. Malorny, Z. Ernaehrungswiss. 9, 332 (1969). Review of metabolism and toxicology: J. Liesivuori, H. Savolainen, Pharmacol. Toxicol. 69, 157-163 (1991). Clinical trial in treatment of warts: R. M. Bhat et al., Int. J. Dermatol. 40, 415 (2001). Reviews: A. Aguilo, T. Horlenko, Hydrocarbon Process. Int. Ed. 59, 120-130 (1980); D. J. Drury in Kirk-Othmer Encyclopedia of Chemical Technology vol. 11 (Wiley-Interscience, New York, 4th ed., 1994) pp 951-958.
Properties: Colorless liq; pungent odor. bp760 100.8°. mp 8.4°. d20 1.220. pKa (20°) 3.75. nD20 1.3714. Flash point, open cup: 59°C. Surface tension at 20°: 37.67 dyn/cm. Viscosity at 20°: 1.784 cP. Dielectric constant at 20°: 57.9. Vapor pressure at 20°: 33.55 mm Hg. Heat of fusion: 3031 cal/mole; of vaporization at 100°: 104 cal/g. Azeotropic mixture with water: 77.5 wt% formic acid, bp760 107.3°. Strong reducing agent. Misc with water, ether, acetone, ethyl acetate, methanol, ethanol. Partially sol in benzene, toluene, xylenes. LD50 in mice (mg/kg): 1100 orally; 145 i.v. (Malorny).
Melting point: mp 8.4°
Boiling point: bp760 100.8°; bp760 107.3°
Flash point: Flash point, open cup: 59°C
pKa: pKa (20°) 3.75
Index of refraction: nD20 1.3714
Density: d20 1.220
Toxicity data: LD50 in mice (mg/kg): 1100 orally; 145 i.v. (Malorny)
Derivative Type: Spirit of Formic Acid
Additional Names: Spirit of ants
Literature References: Composed of 40 ml of 25% formic acid and 225 ml water in sufficient alcohol to make one liter; corresponds to ~1% formic acid and ~70% abs alcohol by vol.
Properties: Colorless liquid. Miscible with water, alcohol.
CAUTION: Potential symptoms of overexposure are eye, skin, throat irritation; skin burns, dermatitis; lacrimation; rhinorrhea; coughing and dyspnea; nausea. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 148.
Use: Preservative in foods and silage; acidulant in dyeing of natural and synthetic fibers, leather tanning; coagulating latex in rubber production; chemical synthesis.
Therap-Cat: Caustic.
Formicin Formocortal Formoterol Formothion Formyl Fluoride

Formic acid
Skeletal structure of formic acid 3D model of formic acid
Formic acid 85 percent.jpg
CAS number 64-18-6 YesY
PubChem 284
ChemSpider 278 YesY
EC number 200-579-1
DrugBank DB01942
KEGG C00058 YesY
ChEBI CHEBI:30751 YesY
RTECS number LQ4900000
ATCvet code QP53AG01
Jmol-3D images Image 1
Molecular formula CH2O2
Molar mass 46.03 g mol−1
Appearance colorless fuming liquid
Odor pungent, penetrating
Density 1.220 g/mL
Melting point 8.4 °C; 47.1 °F; 281.5 K
Boiling point 100.8 °C; 213.4 °F; 373.9 K
Solubility in water miscible
Solubility miscible with ether, acetone, ethyl acetate, glycerol, methanol, ethanol
partially soluble in benzene, toluene, xylenes
log P −0.54
Acidity (pKa) 3.77 [2]
Refractive index (nD) 1.3714 (20 °C)
Viscosity 1.57 cP at 268 °C
MSDS External MSDS
R-phrases R10 R35
S-phrases (S1/2) S23 S26 S45
Main hazards Corrosive; irritant;
NFPA 704
NFPA 704.svg
Flash point 69 °C; 156 °F; 342 K
Autoignition temperature 601 °C; 1,114 °F; 874 K
Explosive limits 14–34%
LD50 700 mg/kg (rat, oral)
Related compounds
Related carboxylic acids Acetic acid
Propionic acid
Related compounds Formaldehyde
Supplementary data page
Structure and
n, εr, etc.
Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Formic acid (systematically called methanoic acid) is the simplest carboxylic acid. Its chemical formula is HCOOH or HCO2H. It is an important intermediate in chemical synthesis and occurs naturally, most notably in ant venom. Its name comes from the Latin word for ant, formica, referring to its early isolation by the distillation of ant bodies. Esters, salts, and the anions derived from formic acid are referred to as formates.