WHO/Food Add./24.65
    FAO Nutrition Meetings
    Report Series No. 38A


    The content of this document is the result of the deliberations of the
    Joint FAO/WHO Expert Committee on Food Additives which met 8-17
    December 1964a


    a Eighth Report of the Joint FAO/WHO Expert Committee on Food
    Additives, Wld Hlth Org. techn. Rep. Ser., 1965, 309; FAO
    Nutrition Meetings Report Series 1965, 38.


    CHEMICAL NAMES           Formic acid; methanoic acid




    MOLECULAR WEIGHT         46.03

    DEFINITION               Formic acid contains not less than 88.0% of
                             CH2O2 and conforms to the following

    DESCRIPTION              Formic acid is a clear, colourless, highly
                             corrosive liquid with a characteristic pungent

    USE                      As a preservative and as a flavour adjunct.


    A.    Solubility:  Miscible with water, ethanol, ether, glycerol.

    B.    Neutralize 1 ml of formic acid with sodium hydroxide TS and add 2
          drops of the acid in excess; then add about 1 ml of ferric
          chloride TS: a deep reddish orange colour results which turns to
          yellowish orange on the addition of mineral acids.

    C.    Place 2 ml of formic acid in a test-tube, add 5 ml of sulfuric
          acid and test the gas evolved with a lighted splinter: a blue
          flame characteristic of carbon monoxide is produced.


    Acetic acid: Not more than 0.4%.

    Dilute 1 ml (1.2 g) of formic acid to 100 ml.  To 50 ml of this
    solution contained in a 250-ml boiling flask add 5 g of yellow
    mercuric oxide.  Boil the solution under total reflux for 2 hours,
    stirring the mixture continuously.  Cool, filter and wash the residue
    with about 25 ml of water.  Add 0.10 ml of phenolphthalein indicator
    solution to the combined filtrate and washings and titrate with 0.02
    N sodium hydroxide.  Not more than 2.0 ml of the 0.02 N sodium
    hydroxide should be required to produce a pink colour.

    Arsenic: Not more than 3 mg/kg.

    Sulfite: Dilute 25 ml of formic acid with 25 ml of water and add
    0.1 ml of 0.1 N iodine solution.  The solution should retain a
    distinct yellow colour.

    Heavy metals: Not more than 5 mg/kg.

    To 3.3 ml (4 g) add about 10 mg of sodium carbonate and evaporate to
    dryness on a steam bath.  Dissolve in 1 ml of 1 N acetic acid and
    dilute to 25 ml.


    Weigh accurately a 125-ml glass-stoppered flask containing 15 ml of
    water.  Quickly introduce 1.0 to 1.5 ml of formic acid and reweigh.
    Dilute to about 50 ml, add 3 drops of phenolphthalein and titrate with
    1 N sodium hydroxide. 1 ml of 1 N sodium hydroxide is equivalent
    to 46.03 mg of CH2O2.

    Biological Data

    Biochemical aspects

    Formate is an intermediate in normal metabolism.  It takes part in the
    metabolism of one-carbon compounds and its carbon may appear in methyl
    groups undergoing transmethylation.  It is eventually oxidized to
    carbon dioxide.1  When formate is administered it could also be
    expected to enter one-carbon metabolism.  However, there is a species
    difference in the extent of this metabolism, for in rabbits no
    administered formate is excreted, whereas in dogs about half the
    administered formate is excreted unchanged in the urine.2  Its
    metabolism in human beings is probably somewhere between that in dogs
    and that in rabbits, judging from the relative amounts of formate
    excreted by man, dogs and rabbits receiving methanol.3,4  Formic acid
    (or formate) is apparently more toxic than other fatty acids, possibly
    owing to its enzyme-inhibiting activity.5  However, no cumulative
    toxic effects are known.

    Acute toxicity

    Exact LD50 values are not available.  In dogs, sodium formate in oral
    doses of 4000 mg/kg and intravenous doses of 3000 mg/kg body-weight
    produced toxic effects such as methaemoglobinaemia and heart
    congestion.6  About 50 mg/kg in 10% aqueous solution given orally to
    dogs or 6 mg/kg given subcutaneously to rabbits produced
    methaemoglobinaemia which lasted about 10 days.2

    This slow disappearance may be due to the inhibition of catalase by
    formic acid.7  4.6 mg per kg intravenously given to 6 dogs produced
    no ill effect and 13.8 mg per kg only slight hypertension.8

    Short-term studies

    Dog.  0.5 g of formic acid daily in the food has been tolerated by
    dogs without effect.9

    Man.  2-4 g of sodium formate daily did not produce toxic
    manifestations in human subjects, even if they were suffering from
    kidney disease.  It has been stated that a daily intake of 2.4 g for
    therapeutic purposes could be tolerated for months without untoward

    Comments on experimental studies reported

    Since long-term toxicity studies are lacking, it is not possible to
    give guidance on an unconditional acceptable daily intake level in


    Level causing no significant toxicological effect 

    Short-term studies in dogs and man indicate that formic acid has no
    significant toxicological effect at a dosage of about 50 mg/kg
    body-weight per day.

    Estimate of acceptable daily intake for man

                             mg/kg body-weight

    Conditional acceptance           0-5

    Further Work Considered Desirable

    Long-term toxicity studies in animals and metabolism studies in man.


    1.  Williams, R. T. (1959) Detoxication mechanisms, London, Chapman &

    2. Croner, P. & Selligmann, E. (1907) Z. Hyg. Infekt.-Kr., 56, 387

    3. Lund, A. (1948) Acta pharmacol. (Kbh.), 4, 99

    4. Lund, A. (1948) Acta pharmacol. (Kbh.) 4, 108

    5. Bleyer, B., Diemair, W. & Leonhard, K. (1933) Arch. Pharm.
    (Weinheim), 271, 539

    6. Fleig, C. (1907) Arch. int. Pharmacodyn., 17, 147

    7. Lück, H. (1957) Biochem. Z., 328, 411

    8. Erra, U. (1958) Fol. med. (Napoli), 41. 366

    9.Dick (1909) Hygienische Rundschan, 14, 313

    10. Rost, E. (1917) Arb. Reichsgesundh.-Amte, 50, 405

    See Also:
       Toxicological Abbreviations
       Formic acid (ICSC)
       Formic acid (WHO Food Additives Series 5)
       FORMIC ACID (JECFA Evaluation)