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CHEMINFO Record Number: 344
CCOHS Chemical Name: n-Butyric Acid

Butanic acid
n-Butanoic acid
Butyric acid (non-specific name)
Ethylacetic acid
1-Propanecarboxylic acid
Propylformic acid
Acide butyrique

CAS Registry Number: 107-92-6
UN/NA Number(s): 2820
RTECS Number(s): ES5425000
EU EINECS/ELINCS Number: 203-532-3
Chemical Family: Saturated aliphatic carboxylic acid / saturated aliphatic monocarboxylic acid / alkanoic acid / butyric acid
Molecular Formula: C4-H8-O2
Structural Formula: CH3-CH2-CH2-C(=O)-OH


Appearance and Odour:
Colourless, oily liquid; unpleasant, penetrating, rancid, butter-like odour.(12,13,14,15)

Odour Threshold:
1 ppb (16); 0.278 ppb (low); 2.5 ppm (high) (17); 20 ppb (100% recognition) (18)

Warning Properties:
GOOD - detectable by odour at very low concentrations which are unlikely to be harmful.

n-Butyric acid may contain small amounts of acrylic acid.(15)

Uses and Occurrences:
Chemical intermediate for cellulose derivatives in lacquers and plastics, for pharmaceuticals, emulsifiers and disinfectants; manufacture of esters used as flavouring agents; in varnish manufacture; as a food additive in butter, cheese, butterscotch, caramel, fruit and nut flavours; in animal feed; leather tanning agent for deliming and swelling hides; sweetening agent in gasolines; in the preservation of high moisture wheat grains against fungal deterioration in India.(3,13,15)


Colourless, oily liquid with an unpleasant, penetrating, rancid, butter-like odour. COMBUSTIBLE LIQUID AND VAPOUR. CORROSIVE to the eyes and skin. Can cause permanent eye damage, including blindness, or permanent scarring of the skin.


Effects of Short-Term (Acute) Exposure

Inhalation of vapours or mists will likely result in mild to severe irritation of the nose, throat and lungs, depending on the airborne concentration. Symptoms would include nasal irritation, sore throat, coughing, hoarseness and, in extreme exposures, difficulty breathing. Propionic acid is acidic and similar effects have been observed in animal studies at high aerosol concentrations. There is no human information available.

Skin Contact:
n-Butyric acid can likely cause moderate to severe skin irritation depending upon the concentration of chemical and the duration of contact. Direct contact can cause irritation, redness and pain. Repeated or prolonged exposures to concentrated solutions may produce more serious effects such as corrosive skin injury.
Mild burning and very slight redness and swelling were observed 52 minutes after application of undiluted n-butyric acid to human skin for 1 hour. This was followed within 24 hours by slight scaling of the skin.(1) Based on animal studies, the acid can result in moderate to severe irritation.
Based on unconfirmed animal information, n-butyric acid may be absorbed through the skin and may cause toxic effects by this route.

Eye Contact:
Contact with vapour, mist or splashes of dilute solutions can likely cause moderate to severe irritation. Based on animal information, direct contact with concentrated solutions can cause corneal burns. Depending on the concentration of the solution and the duration of contact, eye damage may be permanent, including blindness. There is no human information available.

n-Butyric acid is used as a food additive. Animal information indicates that oral toxicity is low. It is a corrosive liquid and ingestion of concentrated solutions can cause severe irritation or corrosive injury to the mouth, throat and stomach, based on animal information. Permanent injury or death could result.
There is no human information available. Ingestion is not a typical route of occupational exposure.

Effects of Long-Term (Chronic) Exposure

SKIN: Repeated or prolonged skin contact may cause dermatitis (redness, dryness, and itching of the skin).

INHALATION: Based on limited animal information, long-term inhalation of n- butyric acid vapours can cause irritation of the lungs. There is no human information available.


There is no animal or human information available.

The International Agency for Research on Cancer (IARC) has not evaluated the carcinogenicity of this chemical.

The American Conference of Governmental Industrial Hygienists (ACGIH) has no listing for this chemical.

The US National Toxicology Program (NTP) has not listed this chemical in its report on carcinogens.

Teratogenicity and Embryotoxicity:
There is no animal or human information available.

Reproductive Toxicity:
There is no animal or human information available.

Negative results have been obtained in in vitro tests using bacteria and mammalian cells. Positive results (reversible DNA inhibition) were obtained in one in vitro test using human cells.(2) No in vivo mammalian studies or human information is available.

Toxicologically Synergistic Materials:
There is no specific information available.

Potential for Accumulation:
n-Butyric acid does not accumulate in the body. It is readily absorbed from the gastrointestinal tract and rapidly broken down (metabolized) in the body. It is metabolized to ketone bodies and acetic acid, which may be excreted in the urine or incorporated into normal processes in the body. Butyrates are normally present in the body.(3)


If symptoms are experienced, remove source of contamination or have victim move to fresh air. Obtain medical advice immediately.

Skin Contact:
Avoid direct contact with this chemical. Wear chemical protective gloves, if necessary. As quickly as possible, flush contaminated area with lukewarm, gently flowing water for 20-30 minutes, by the clock. DO NOT INTERRUPT FLUSHING. If necessary, keep emergency vehicle waiting. Under running water, remove contaminated clothing, shoes, and leather goods (e.g., watchbands, belts). If irritation persists, repeat flushing. Transport victim to an emergency care facility immediately. Completely decontaminate clothing, shoes and leather goods before re-use or discard.

Eye Contact:
Avoid direct contact with this chemical. Immediately flush the contaminated eye(s) with lukewarm, gently flowing water for 20-30 minutes, by the clock, while holding the eyelid(s) open. Neutral saline solution may be used as soon as it is available. DO NOT INTERRUPT FLUSHING. If necessary, keep emergency vehicle waiting. Take care not to rinse contaminated water into the non-affected eye or onto the face. Quickly transport victim to an emergency care facility.

NEVER give anything by mouth if victim is rapidly losing consciousness, or is unconscious or convulsing. Have victim rinse mouth thoroughly with water. DO NOT INDUCE VOMITING. Have victim drink 240 to 300 mL (8 to 10 oz.) of water. If milk is available, it may be administered AFTER the water has been given. If vomiting occurs naturally, have victim rinse mouth and repeat administration of water. Quickly transport victim to an emergency care facility.

First Aid Comments:
Provide general supportive measures (comfort, warmth, rest).
All first aid procedures should be periodically reviewed by a doctor familiar with the material and its conditions of use in the workplace.


Flash Point:
72 deg C (161 deg F) (closed cup) (14)

Lower Flammable (Explosive) Limit (LFL/LEL):
2% (14)

Upper Flammable (Explosive) Limit (UFL/UEL):
10% (14)

Autoignition (Ignition) Temperature:
Lowest reported value: 425 deg C (797 deg F) (13)

Sensitivity to Mechanical Impact:
Probably not sensitive. Stable material.

Sensitivity to Static Charge:
Specific information not available. Probably does not accumulate static charge, since the electrical conductivity is probably high (less than 1 x 10(6) pS/m).(19) /FTD/Carbon monoxide and carbon dioxide.(20) Incomplete combustion may also produce irritating fumes and acrid smoke.

Fire Hazard Summary:
Combustible liquid. Can form explosive mixtures with air at, or above, 72 deg C. During a fire irritating/toxic gases may be formed. Closed containers may rupture violently when exposed to fire or excessive heat for sufficient time.

Extinguishing Media:
Carbon dioxide, dry chemical powder, "alcohol resistant" foam, polymer foam, water spray or fog.(14,20)

Fire Fighting Instructions:
Evacuate area and fight fire from a safe distance or protected location. Approach fire from upwind to avoid hazardous vapours and toxic decomposition products.
Closed containers may rupture violently when exposed to heat of fire. If possible, isolate materials not yet involved in the fire, and move containers from fire area if this can be done without risk, and protect personnel. Otherwise, fire-exposed containers or tanks should be cooled by application of hose streams. Application should begin as soon as possible and should concentrate on any unwetted portions of the container. If this is not possible, use unmanned monitor nozzles and immediately evacuate the area.
If a leak or spill has not ignited, use water spray in large quantities to disperse the vapours, protect personnel attempting to stop a leak and to dilute the spill to a nonflammable mixture. Water spray may be used to flush spills away from ignition sources. Solid streams of water may be ineffective and spread material.
For a massive fire in a large area, use unmanned hose holder or monitor nozzles. If this is not possible, withdraw from fire area and allow fire to burn. Stay away from ends of tanks. Withdraw immediately in case of rising sound from venting safety device or any discolouration of tank due to fire.
n-Butyric acid and its decomposition products are hazardous to health. Do not enter without wearing specialized protective equipment suitable for the situation. Firefighter's normal protective clothing (Bunker Gear) will not provide adequate protection. Chemical resistant clothing (e.g. chemical splash suit) and positive pressure self-contained breathing apparatus (MSHA/NIOSH approved or equivalent) may be necessary.


NFPA - Health: 3 - Short exposure could cause serious temporary or residual injury.
NFPA - Flammability: 2 - Must be moderately heated or exposed to relatively high ambient temperatures before ignition can occur.
NFPA - Instability: 0 - Normally stable, even under fire conditions, and not reactive with water.


Molecular Weight: 88.11

Conversion Factor:
1 ppm = 3.6 mg/m3; 1 mg/m3 = 0.28 ppm at 25 deg C (calculated)

Physical State: Liquid
Melting Point: -8 to -5.5 deg C (17.6 to 22.1 deg F) (18)
Boiling Point: 164 deg C (327.2 deg F) (3,12,13)
Relative Density (Specific Gravity): 0.96 at 20 deg C (water = 1) (3,12,18,21)
Solubility in Water: Soluble in all proportions.(3,12,19)
Solubility in Other Liquids: Soluble in all proportions in ethanol and diethyl ether (3)
Coefficient of Oil/Water Distribution (Partition Coefficient): Log P (oct) = 0.79 (22)
pH Value: 2.9 (0.1 M solution in water); 2 (about 58% solution) (calculated)
Vapour Density: 3.0 (air = 1) (19)
Vapour Pressure: 0.057 kPa (0.43 mm Hg) at 20 deg C (18); 0.133 kPa (1 mm Hg) at 25.5 deg C (21)
Saturation Vapour Concentration: 566 ppm (0.0566%) at 20 deg C; 1316 ppm (0.132%) at 25.5 deg C (calculated)
Evaporation Rate: Not available
Critical Temperature: 355 deg C (671 deg F) (21)

Other Physical Properties:
ACIDITY: Weak acid. pKa = 4.81 (Ka = 1.54 x 10(-5)) at 20 deg C (21); 4.823 (Ka = 1.50 x 10(-5)) at 25 deg C (12)
VISCOSITY-DYNAMIC: 1.54 mPa.s (1.54 centipoises) at 20 deg C (12,21)
VISCOSITY-KINEMATIC: 1.604 mm2/s (1.604 centistokes) at 20 deg C (calculated)
SURFACE TENSION: 26.74 mN/m (26.74 dynes/cm) at 20 deg C (16); 26.0 mN/m (26.0 dynes/cm) at 25 deg C (21)
CRITICAL PRESSURE: 5269 kPa (52 atmospheres) (21)


Normally stable

Hazardous Polymerization:
Does not occur

Incompatibility - Materials to Avoid:

NOTE: Chemical reactions that could result in a hazardous situation (e.g. generation of flammable or toxic chemicals, fire or detonation) are listed here. Many of these reactions can be done safely if specific control measures (e.g. cooling of the reaction) are in place. Although not intended to be complete, an overview of important reactions involving common chemicals is provided to assist in the development of safe work practices.

OXIDIZING AGENTS (e.g. chromium trioxide, nitric acid, peroxides, permanganates) - may react violently or explosively. Increased risk of fire.(19,20,23)
BASES (including alkalis, such as sodium hydroxide) - vigorous or violent reaction may occur, yielding heat and pressure.(19,20)
REACTIVE METALS (e.g. powdered aluminum, zinc) - may produce flammable hydrogen gas.(16)
PHOSPHORUS TRICHLORIDE - may form spontaneously flammable phosphine and explode.(23)
POTASSIUM t-BUTOXIDE - may ignite.(23)

Hazardous Decomposition Products:
None reported

Conditions to Avoid:
Temperatures above 72 deg C, open flames

Corrosivity to Metals:
Corrosive to steel, cast iron, and lead.(24) Aluminum is resistant at room temperature and is widely used for handling n-butyric acid. It may be attacked at elevated temperatures. n-Butyric acid is not corrosive to copper, bronze and brass, and can be used for handling, provided acid solutions are free of oxidants. Type 304 and 316 stainless steels are resistant to n-butyric acid at room temperature.(25)


LD50 (oral, rat): 2000 mg/kg (4); 2940 mg/kg (5); 8790 mg/kg (6)

LD50 (dermal, rabbit): 510 mg/kg (7, unconfirmed); 6083 mg/kg (6)

Eye Irritation:

Application of in excess of a 5% solution of butyric acid caused severe injury in rabbits (graded 9/10; scored over 5 where 5 is severe injury).(6)

Skin Irritation:

Application of 0.01 mL of undiluted n-butyric acid produced severe irritation (strong redness, swelling or slight tissue destruction) (graded 5/10) in rabbits.(6) Moderate irritation was observed in rabbits two other tests.(7, unconfirmed)

Effects of Short-Term (Acute) Exposure:

Severe respiratory inflammation (signs of bronchial and capillary dilation and emphysema) was observed following exposure of rabbits to extremely high airborne concentrations (40000 mg/m3) of n-butyric acid aerosols for 90 minutes.(3) Blood changes (massive increase in circulating lymphocytes and neutrophils), assumed to result from irritation, were observed in rats, mice and rabbits after inhalation of 100-200 mg/m3 n-butyric acid aerosols for an unspecified length of time.(3) No deaths resulted following exposure of rats to air saturated with n-butyric acid vapour for 8 hours.(5)

Evidence of damage to the lining of the stomach (including cellular proliferation and ulcers in rats only) was observed in rats, mice and hamsters following feeding of high concentrations (4% n-butyric acid) in the diet for 7 days.(8)

Effects of Long-Term (Chronic) Exposure:

Some effects on the spleen (splenic hyperemia) and mild lung (bronchiolar) inflammation were observed following exposure of rats to 0.0076, 0.018 or 0.144 mg/m3 n-butyric acid vapour for 90 days. No statistical evaluation of the data is reported.(9)

Tissue damage in the stomach was observed after rats were fed a diet containing a very high concentration (25%) n-butyric acid for up to 35 weeks.(10) Ulcers and benign growths in the stomach were observed in rats fed 5-10% n-butyric acid in the diet for 51-500 days.(11)


Selected Bibliography:
(1) Oettel, H. Effect of organic liquids on the skin. Archiv fuer Experimentelle Pathologie. Vol. 83 (1936). p. 641-696. (English translation: NIOSHTIC Control Number: 00071872)
(2) Hagopian, H.K., et al. Effect of n-butyrate on DNA synthesis in chick fibroblasts and HeLa cells. Cell. Vol. 12 (November, 1977). p. 855-860
(3) Katz, G.V., et al. Aliphatic carboxylic acids. In: Patty's industrial hygiene and toxicology. 4th edition. Edited by G.D. Clayton et al. Volume II. Toxicology. Part E. John Wiley and Sons, 1994. p. 3525, 3528, 3538-3541
(4) Izmerov, N.F., et al. Toxicometric parameters of industrial toxic chemicals under single exposure. Centre of International Projects, GKNT, 1982. p. 30
(5) Smyth, Jr., H.F., et al. Range-finding toxicity data: list IV. A.M.A. Archives of Industrial Health. Vol. 4 (1951). p. 119-122
(6) Smyth, Jr., H.F., et al. Range-finding toxicity data: list V. A.M.A. Archives of Industrial Hygiene and Occupational Medicine. Vol. 10 (1954). p. 61-68
(7) RTECS record for butyric acid. Last updated: 9601
(8) Harrison, P.T.C., et al. Early changes in the forestomach of rats, mice and hamsters exposed to dietary propionic and butyric acid. Food and Chemical Toxicology. Vol. 29, no. 6 (1991). p. 367-371
(9) Sergeev, A.N. et al. Effect of low concentrations of synthetic fatty acids on experimental animals (pathomorphological investigations). Gigiena i Sanitariya Vol. 35, nos 7,8,9 (1970). (English Translation: Hygiene and Sanitation. Vol. 35, nos 7,8,9 (1970))
(10) Salmon, W.D., et al. The occurrence of gastric lesions in the rat as a result of feeding tributyrin. Journal of the National Cancer Institute. Vol. 10 (1949). p. 361-373
(11) Mori, K. The production of gastric lesions in the rat by acetic acid feeding. Gann. Vol. 43 (December, 1952). p. 443-447
(12) Bagby, M.O. Carboxylic acids: survey. In: Kirk-Othmer encyclopedia of chemical technology. 4th edition. Volume 5. John Wiley and Sons, 1993. p. 147-168
(13) Riemenschneider, W. Carboxylic acid, aliphatic. In: Ullmann's encyclopedia of industrial chemistry. 5th completely revised edition. Vol. A 5. VCH Verlagsgesellschaft, 1985. p. 235-245
(14) Fire protection guide to hazardous materials. 13th ed. Edited by A.B. Spencer, et al. National Fire Protection Association, 2002. NFPA 325; NFPA 49
(15) HSDB record for butyric acid. Date of last revision: 96/01/19
(16) Weiss, G., ed. Hazardous chemicals data book. 2nd edition. Noyes Data Corporation, 1986. p. 209
(17) Ruth J.H. Odor thresholds and irritation levels of several chemical substanstances: a review. American Industrial Hygiene Association Journal. Vol. 47 (March, 1986). p. A-142 to A-151
(18) Verschueren, K. Handbook of environmental data on organic chemicals. 3rd edition. Van Nostrand Reinhold, 1996. p. 30, 396-399
(19) Chemical safety sheets: working safely with hazardous chemicals. Kluwer Academic Publishers, 1991. p. 165
(20) The Sigma-Aldrich library of chemical safety data. Edition II. Volume 1. Sigma-Aldrich Corporation, 1988. p. 654C
(21) Weast, R.C., ed. Handbook of chemistry and physics. 66th edition. CRC Press, 1985-1986. p. C-180, D-161, D-199, F-33, F-38, F-63
(22) Leo, A., et al. Partition coefficients and their uses. Chemical Reviews. Vol. 71, no. 6 (December, 1971). p. 563
(23) Urben, P.G., ed. Bretherick's handbook of reactive chemical hazards. 5th edition. Volume 1. Butterworth-Heinemann Ltd., 1995. p. 558, 567, 1350, 1378
(24) Corrosion data survey: metals section. 6th edition. National Association of Corrosion Engineers, 1985. p. 26-4 to 27-4
(25) Elder, G.B. Corrosion by organic acid. In: Process industries corrosion. National Association of Corrosion Engineers, 1975. p. 247-254
(26) Forsberg, K., et al. Quick selection guide to chemical protective clothing. 4th ed. Van Nostrand Reinhold, 2002
(27) European Economic Community. Commission Directive 93/72/EEC. September 1, 1993
(28) Industrial Bio-Test Labs Inc. Primary skin irritation tests with eighteen materials in albino rabbits with cover letter dated 061589. Date produced: July 28, 1972. Hoechst Celanese Corp. EPA/OTS 86-890001277. NTIS/OTS0520783.

Information on chemicals reviewed in the CHEMINFO database is drawn from a number of publicly available sources. A list of general references used to compile CHEMINFO records is available in the database Help.

Review/Preparation Date: 1997-04-30

Revision Indicators:
US transport 1998-03-01
Resistance of materials 1998-04-01
Bibliography 1998-04-01
Emergency overview 2000-08-01
Acute exposure (ingestion) 2000-08-01
First aid (ingestion) 2000-08-01
Bibliography 2003-04-16
Bibliography 2004-04-05
Bibliography 2006-03-30

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