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Chemical Name: Tetraethyl Orthosilicate
Synonyms: TEOS, Tetraethoxysilane
Chemical Formula: Si(OC2H5)4
CAS Number: 78-10-4
GHS Classification: Flammable liquid, Category 3; Skin irritation, Category 2; Eye irritation, Category 2A; Specific target organ toxicity (single exposure), Category 3
Main Risks: TEOS brings fire risk by flashing at temperatures lower than many expect. Direct skin or eye contact delivers irritating or painful outcomes, so care means avoiding splashes. Short-term inhalation can fog up your thinking, irritate the airways, or add to the stress of any underlying illness.
Pictograms: Flame, Exclamation Mark
Signal Word: Warning
Main Ingredient: Tetraethyl Orthosilicate, min. 99% for reagent grade
Contaminants: Trace levels of ethanol, diethyl ether
Inhalation: Out in the fresh air is best. Breathing may come easier with support. Medical attention should be sought if symptoms linger.
Skin Contact: Remove contaminated clothing and rinse skin with lots of water. Persistent irritation needs medical assessment.
Eye Contact: Open eyelids and wash with clean water for several minutes. Seek attention if discomfort or vision changes stay.
Ingestion: Rinse mouth with water, seek medical opinion. Avoid inducing vomiting as this can introduce the chemical to the lungs.
Fire Hazards: TEOS ignites easily. Air mixtures can flash. Combustion sends out toxic fumes, including silicon oxides and carbon oxides.
Extinguishing Methods: Use foam, dry chemical powder, or carbon dioxide. Avoid spraying water as it may spread the fire.
Special Protective Equipment: Firefighters carry self-contained breathing apparatus and chemical-resistant gear for any fire involving TEOS.
Precautions: Remove containers from fire if safe. Cool tanks with flooding quantities of water far from those in direct flame.
Spill Management: Evacuate unnecessary staff and control ventilation. Eliminate ignition sources. Wear protective gear and use inert absorbent material such as sand to contain any spill.
Clean-Up: Absorb with sand or other non-combustible material and store in a sealable container for disposal.
Environmental Caution: Avoid allowing product to enter drains, watercourses, or soil. Use barriers if spill risks reaching natural environments.
Handling: Only trained individuals work with TEOS because it delivers strong reactions to skin and airways. Take care to avoid direct contact and work in ventilated spaces. Don't handle near ignition sources, and use grounding and bonding for containers to sidestep static discharge.
Storage: Keep tightly sealed in a cool, dry, and ventilated area. Protect from direct sunlight, moisture, and heat. Store away from incompatible materials like strong acids, bases, and oxidizers.
Exposure Limits: No specific OSHA or ACGIH limits for TEOS, but ethanol byproduct levels have set standards.
Engineering Controls: Fume hoods or local exhaust systems help keep vapor exposure down.
PPE: Chemical-resistant gloves, goggles or face shields, flame-retardant lab coats, and, if needed, approved respirators all form part of the protocol. Remove contaminated clothing quickly.
Hygiene: Wash hands after handling. Never eat, drink, or smoke while working with TEOS.
Appearance: Clear, colorless liquid
Odor: Alcohol-like
Boiling Point: 168–169°C
Melting Point: -82°C
Flash Point: Approximately 45–49°C (closed cup)
Solubility: Slightly soluble in water, soluble in alcohols and organic solvents
Vapor Pressure: Moderate at room temperature
Density: 0.93–0.94 g/cm³
Other Information: Hydrolyzes on contact with moisture, releasing ethanol.
Chemical Stability: Stable under still, dry, and cool storage conditions.
Conditions to Avoid: Moisture, heat, open flames, static electricity sources
Incompatible Materials: Water, acids, alkalis, oxidizing agents
Hazardous Decomposition: Ethanol, silicon oxides, carbon oxides may develop if burned or hydrolyzed.
Acute Effects: Inhalation irritates the nose and lungs; overexposure brings headache, dizziness, and drowsiness. Eyes and skin feel burned or dry if splashed.
Chronic Effects: No strong evidence of long-term cancer risks but repeated overexposure dries and damages skin. Reproductive and developmental effects need more research.
Routes of Exposure: Skin, eyes, inhalation, accidental ingestion
Aquatic Toxicity: Ethanol produced during hydrolysis may contribute to toxicity in aquatic life. Bulk release should be avoided to protect water quality.
Persistence and Degradability: TEOS reacts quickly in the environment, breaking down as soon as it hits moisture, but its impact depends on quantity and dilution.
Bioaccumulation: Not expected to build up in living organisms.
Mobility in Soil: Likely to disperse if spilled onto soil, driven by rain and groundwater movement.
Waste Disposal: Dispose through licensed hazardous waste handlers. Burning in controlled incinerators handles small volumes, but must obey local laws.
Disposal of Containers: Rinse containers thoroughly, then render them unusable before handling as chemical waste.
Statutory Requirements: Follow national and regional chemical and hazardous waste regulations strictly.
UN Number: 1292
Class: Flammable liquid
Packing Group: III
Labeling: Flammable Liquid (3)
Special Considerations: Transport in tightly sealed drums or bottles, away from heat and oxidizers. Secure loads to avoid leaks and tip-overs. Emergency response guides recommend keeping spill kits and fire extinguishers handy during transit.
US Regulations: Listed on TSCA Inventory, subject to SARA Title III reporting
EU Regulations: Listed in REACH Annex, marked for flammability and health hazard
Workplace Controls: Subject to occupational chemical handling guidelines
Environmental Regulations: Spill reporting and clean-up standards set by local rules
Labelling Laws: Hazard pictograms and clear hazard statements required for all supplied volumes
