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Chemical Name: Tetramethylammonium Hydroxide Pentahydrate
Common Names: TMAH, Tetramethylammonium hydroxide, TMAH·5H2O
CAS Number: 10424-65-4
Manufacturer or Supplier: Chemical manufacturing companies, research suppliers
Recommended Use: Photoresist developer, organic synthesis, laboratory reagent, electronics processing
Contact Information for Emergency: Available from supplier’s Safety Officer or 24-hour health emergency contact number
Synonym: TetraMethylAmmonium Hydroxide solution (pentahydrate form)
Classification: Corrosive to skin and eyes, Acute oral toxicity, Environmentally hazardous for aquatic life
Signal Word: Danger
Hazard Statements: Causes severe burns to skin and eyes, fatal if swallowed, causes respiratory irritation, harmful to aquatic life
Pictogram: Corrosion, Skull and Crossbones, Environment
Precautionary Statements: Wear chemical resistant gloves, safety goggles, face protection; handle in ventilated area; do not eat, drink, or smoke near material; avoid release to the environment
Routes of Exposure: Inhalation, ingestion, skin contact, eye contact
Symptoms of Exposure: Burning sensation, shortness of breath, abdominal pain, blurred vision, dermatitis, irreversible tissue damage
Substance: Tetramethylammonium Hydroxide Pentahydrate
Molecular Formula: C4H13NO·5H2O
Purity: Greater than 98% (as typically supplied)
Other Components: Water (as hydrate); may contain minor levels of impurities from production process
Concentration: 100% for solid pentahydrate, often found dissolved (e.g., 25% wt aqueous solutions)
Relevant Impurities: Residual trimethylamines, inorganic salts in trace amounts
Inhalation: Remove to fresh air immediately; seek medical attention if breathing difficulty or irritation persists; administer artificial respiration in severe cases
Skin Contact: Remove contaminated clothing; flush skin with plenty of running water for at least 15 minutes; seek immediate medical attention
Eye Contact: Rinse cautiously with water for at least 15 minutes, holding eyelids apart; remove contact lenses if present; obtain medical help without delay
Ingestion: Rinse mouth carefully with water; do not induce vomiting; never give anything by mouth to unconscious victim; get emergency medical care directly
General Medical Advice: Observe for delayed symptoms; burns or respiratory effects may worsen over time; symptomatic treatment and medical observation required
Suitable Extinguishing Media: Use dry chemical, carbon dioxide (CO2), alcohol-resistant foam, or water spray for large fires
Hazards from Combustion: Emits toxic and irritating fumes of nitrogen oxides, methylamines and potentially carbon monoxide under fire conditions
Protective Equipment: Wear full protective turnout gear, self-contained breathing apparatus (SCBA), chemical resistant gloves
Firefighting Tips: Approach from upwind, avoid inhalation of vapors or combustion products, cool tanks with water spray if exposed to fire
Explosion Hazards: Material may react violently with strong oxidizers or acids; dusts can be explosive in air if dried
Personal Precautions: Evacuate area, use full chemical protection (gloves, goggles, face shield, impervious clothing), avoid breathing vapors or dust
Environmental Precautions: Prevent entry into sewers, surface or ground waters; notify authorities if spillage occurs in large quantity
Cleanup Methods: Absorb with inert material (dry sand, earth, vermiculite), collect in chemical waste containers, neutralize residue with dilute acetic acid or citric acid; ventilate area thoroughly
Decontamination: Wash spill site with large amounts of water after material pick-up is complete; avoid runoff into storm drains
Handling: Use only in well ventilated laboratory or process area with emergency shower and eyewash access; avoid skin and eye contact; never pipet by mouth
Storage Conditions: Store in tightly closed original containers made of compatible materials (HDPE, glass); keep away from acids, oxidizers, and metals; maintain at room temperature or cooler, protect from direct sunlight
Special Precautions: Label containers clearly; secondary containment trays recommended; rotate stocks to prevent aging; emergency spill kit present
Incompatible Materials: Strong acids, halogenated solvents, organic anhydrides, oxidizers, certain metals
Threshold Limit Value (TLV): ACGIH: no established limit, severe toxicity at low concentrations
Engineering Controls: Chemical fume hood required; local exhaust strongly recommended
Personal Protective Equipment: Nitrile or butyl rubber gloves, chemical splash goggles, face shield, chemical resistant apron and long sleeves
Respiratory Protection: NIOSH/MSHA-approved respirator for vapor or dust hazards, especially during spills or large-scale use
Hygiene: Do not eat, drink, or smoke when handling; wash hands and skin thoroughly after use; remove and wash contaminated clothing
Appearance: White crystalline solid or colorless liquid when dissolved
Odor: Ammonia-like pungent odor
Molecular Weight: 181.25 g/mol (pentahydrate form)
pH (5% solution): Over 13.5 (strong base)
Melting Point: 37 to 56°C (depends on hydration state)
Boiling Point: Decomposes before boiling (releases toxic vapors)
Solubility: Readily soluble in water and alcohol
Vapor Pressure: Not significant at room temperature for the hydrate
Density: Around 1.016 g/cm³ (solution)
Decomposition Temperature: Above 100°C, releases methylamine and other gases
Flash Point: Not applicable
Evaporation Rate: Negligible for hydrate/solid
Partition Coefficient (n-octanol/water): Not available
Chemical Stability: Stable under dry, ambient conditions; absorbs moisture from air readily
Reactivity: Strong base, reacts rapidly with acids, evolves heat and possible splattering
Hazardous Reactions: Violent exothermic reaction with acids; reacts with organic halides; ammonium salt formation
Hazardous Decomposition Products: Methylamine, ammonia, nitrogen oxides, carbon monoxide
Conditions to Avoid: Exposure to acids, strong oxidants, extreme heat, metal surfaces
Polymerization: Will not polymerize
Acute Toxicity: Oral LD50 (rat): 25-50 mg/kg (extremely toxic by ingestion)
Skin Corrosion/Irritation: Causes rapid and severe burns, potential for deep tissue injury
Eye Damage: Causes permanent blindness, corneal injury, tissue destruction
Inhalation Toxicity: Toxic effects on central nervous system, respiratory tract and possibly fatal pulmonary edema
Chronic Toxicity: No reliable studies in chronic low exposure, repeated contact may cause dermatitis
Sensitization: Not known as a skin sensitizer
Other Effects: Ingestion and systemic absorption lead to respiratory collapse, muscle paralysis, and fatal organ damage
Ecotoxicity: Highly toxic to aquatic organisms at low concentrations; LC50 value for fish is below 1 mg/L
Persistence: Strong basicity persists in environment until neutralized or diluted
Bioaccumulation: Potential for bioaccumulation considered low due to high water solubility and instability in aerobic conditions
Degradability: May degrade slowly in environment, depending on pH and presence of natural acids
Other Environmental Hazards: Spillage may raise pH of natural waters drastically, lethal for aquatic plants and animals
Waste Treatment Methods: Neutralize with dilute acid under controlled conditions, then dilute with large amounts of water
Disposal Containers: Use compatible, impervious containers clearly labeled for hazardous waste
Regulatory Disposal: Dispose via licensed hazardous waste contractor, according to local, state, and federal regulations
Prohibited Disposal: Do not pour into drains, surface waters, or normal trash
Unused Material and Residues: Treat as hazardous waste; follow institutional protocols for strong bases
UN Number: UN 2430
Proper Shipping Name: Tetramethylammonium Hydroxide, solid (or solution, depending on form), corrosive
Hazard Class: 8 (Corrosive substances)
Packing Group: II (medium danger)
Marine Pollutant: Yes
Special Precautions for Transport: Secure against movement and leakage during transit, segregate from acids and foodstuffs
Labels: Corrosive, Marine Pollutant
OSHA Status: Regulated as hazardous, subject to Hazard Communication standard
EPA: Toxic substance under TSCA guidelines
SARA Title III: Classified as an immediate and delayed health hazard; listed in SARA 302 (extremely hazardous) and SARA 313 (toxic chemical release inventory)
WHMIS (Canada): D1A (very toxic), D2A (carcinogenic, mutagenic), E (corrosive)
REACH (Europe): Registration required for handling, substance of high concern under ECHA
Other Local Requirements: Subject to regulations restricting use, storage, and disposal at state or provincial level
Label Statements: Warning: Fatal on absorption, ingestion, contact, or inhalation; proper training before handling
