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CAS Number: 100-97-0
Synonyms: Hexamine; Methenamine; Urotropine; E239; Hexamethylenetetramine; HMTA; HMT; Aminoform; Formin; Hexa; 1,3,5,7-Tetraazaadamantane
Physical Properties:
Appearance: White to colorless crystalline solid (odorless or slight fishy/amine odor when moist).
Solubility: Freely soluble in water (approx. 850 g/L at 20°C); soluble in ethanol, chloroform, methanol; insoluble in diethyl ether, petroleum ether.
Melting point: 280°C (sublimes without melting under atmospheric pressure; decomposes at 260°C under vacuum).
Density: 1.33 g/cm³ (solid).
pH (10% solution): 8.4–9.0 (basic).
Vapor pressure: Very low at room temperature; sublimes gradually.
Flash point: 250°C (solid combusts but not readily flammable).
Hygroscopicity: Slightly hygroscopic (absorbs moisture from air).
Applications:
Food preservative (E239) – formerly used: Caviar and fish roe (banned in many jurisdictions; restricted in EU to certain fish products at maximum 250 mg/kg expressed as HCHO). Used as a slow-release source of formaldehyde.
Medical (human): Urinary tract antiseptic (methenamine hippurate – Hiprex®, methenamine mandelate – Mandelamine®) for chronic suppression of recurrent urinary tract infections (UTIs); requires acidic urine (pH < 5.5) to hydrolyze to formaldehyde.
Industrial (major use): Production of phenolic and melamine resins (as curing agent or hardener), rubber vulcanization accelerator (hexamine), explosive manufacturing (RDX – cyclotrimethylenetrinitramine from hexamine + nitric acid + ammonium nitrate).
Chemical intermediate: Synthesis of pharmaceutical compounds (e.g., chlorpheniramine), fungicides, corrosion inhibitors.
Fuel tablets: Camping stove fuel "hexamine fuel tablets" (Esbit) – clean-burning, smokeless solid fuel.
Metal treatment: Corrosion inhibitor in pickling baths, coolants, and cutting fluids.
Textile and paper: Crosslinking agent for finishing treatments.
Analytical chemistry: Buffer component and fixing agent in histology.
Description:
Hexamethylene tetramine (E239) is a heterocyclic organic compound with a cage-like adamantane structure consisting of four nitrogen atoms and six methylene bridges. It is produced industrially by the condensation of formaldehyde (formalin) with ammonia in the gas or liquid phase. In the food context, E239 is not a direct preservative by itself; rather, it slowly hydrolyzes in acidic conditions to release formaldehyde (a potent antimicrobial agent) and ammonium salts. The mechanism is: C₆H₁₂N₄ + 6H₂O → 4NH₃ + 6HCHO (formaldehyde). Formaldehyde denatures proteins, crosslinks nucleic acids, and inhibits bacterial and fungal growth. Historically, E239 was used to preserve caviar (fish roe) for long-distance transport and storage without refrigeration. However, the release of free formaldehyde (a known carcinogen and irritant) in food raised serious safety concerns. JECFA has not established an ADI for formaldehyde; the presence of any detectable formaldehyde from food additives is generally not permitted. Consequently, E239 was banned as a direct food additive in the European Union (EU) in 2005 (Directive 2005/34/EC). It is also banned in the US (FDA does not approve hexamine as a food preservative; any formaldehyde-releasing agents are excluded from direct food use) and many other countries. Currently, only limited exemptions exist for certain fish products (e.g., caviar) in some non-EU jurisdictions. In stark contrast, hexamine is widely used in medicine as an oral urinary antiseptic because the acidic urine environment (pH < 5.5) ensures that formaldehyde is released only within the bladder lumen, not systemically. The formaldehyde concentration achieved (typically 10–30 ppm) is sufficient to inhibit most uropathogens (E. coli, Proteus, Klebsiella, Enterococcus) without damaging the bladder epithelium. Nevertheless, the medical dose (1–2 g/day) is far above any food residue level. Toxicologically, hexamine itself has low acute oral toxicity (LD₅₀ in rats ~ 9 g/kg), but the formaldehyde released is a potent protein crosslinker, irritant, and carcinogen (Group 1 carcinogen by IARC). Chronic dietary exposure to formaldehyde has been associated with nasopharyngeal cancer and gastrointestinal effects. For this reason, the food use of E239 is now almost entirely obsolete, replaced by safer preservatives (e.g., sodium benzoate, potassium sorbate, natamycin). In industrial settings, hexamine remains invaluable due to its high nitrogen content, thermal stability, and ability to form coordination complexes with metals (corrosion inhibition) and resins (curing). Its combustion produces non-toxic gases (N₂, H₂O, CO₂ under complete combustion), making it safe as a fuel tablet. However, the legacy of E239 in caviar preservation remains a cautionary tale regarding formaldehyde release from food additives.
SAFETY INFORMATION ABOUT HEXAMETHYLENE TETRAMINE
First aid measures:
Description of first aid measures:
General advice:
Consult a physician.
Show this safety data sheet to the doctor in attendance.
Move out of dangerous area:
If inhaled:
If breathed in, move person into fresh air.
If not breathing, give artificial respiration.
Consult a physician.
In case of skin contact:
Take off contaminated clothing and shoes immediately.
Wash off with soap and plenty of water.
Consult a physician.
In case of eye contact:
Rinse thoroughly with plenty of water for at least 15 minutes and consult a physician.
Continue rinsing eyes during transport to hospital.
If swallowed:
Do NOT induce vomiting.
Never give anything by mouth to an unconscious person.
Rinse mouth with water.
Consult a physician.
Firefighting measures:
Extinguishing media:
Suitable extinguishing media:
Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
Special hazards arising from the substance or mixture
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas
Advice for firefighters:
Wear self-contained breathing apparatus for firefighting if necessary.
Accidental release measures:
Personal precautions, protective equipment and emergency procedures
Use personal protective equipment.
Avoid breathing vapours, mist or gas.
Evacuate personnel to safe areas.
Environmental precautions:
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Methods and materials for containment and cleaning up:
Soak up with inert absorbent material and dispose of as hazardous waste.
Keep in suitable, closed containers for disposal.
Handling and storage:
Precautions for safe handling:
Avoid inhalation of vapour or mist.
Conditions for safe storage, including any incompatibilities:
Keep container tightly closed in a dry and well-ventilated place.
Containers which are opened must be carefully resealed and kept upright to prevent leakage.
Storage class (TRGS 510): 8A: Combustible, corrosive hazardous materials
Exposure controls/personal protection:
Control parameters:
Components with workplace control parameters
Contains no substances with occupational exposure limit values.
Exposure controls:
Appropriate engineering controls:
Handle in accordance with good industrial hygiene and safety practice.
Wash hands before breaks and at the end of workday.
Personal protective equipment:
Eye/face protection:
Tightly fitting safety goggles.
Faceshield (8-inch minimum).
Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
Skin protection:
Handle with gloves.
Gloves must be inspected prior to use.
Use proper glove
removal technique (without touching glove's outer surface) to avoid skin contact with this product.
Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices.
Wash and dry hands.
Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
Splash contact
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
It should not be construed as offering an approval for any specific use scenario.
Body Protection:
Complete suit protecting against chemicals, The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
Respiratory protection:
Where risk assessment shows air-purifying respirators are appropriate use a fullface respirator with multi-purpose combination (US) or type ABEK (EN 14387) respirator cartridges as a backup to engineering controls.
If the respirator is the sole means of protection, use a full-face supplied air respirator.
Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
Control of environmental exposure
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Stability and reactivity:
Chemical stability:
Stable under recommended storage conditions.
Incompatible materials:
Strong oxidizing agents:
Hazardous decomposition products:
Hazardous decomposition products formed under fire conditions.
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas.
Disposal considerations:
Waste treatment methods:
Product:
Offer surplus and non-recyclable solutions to a licensed disposal company.
Contact a licensed professional waste disposal service to dispose of this material.
Contaminated packaging:
Dispose of as unused product
