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Chemical Name: Sulfurous Acid
CAS Number: 7782-99-2
Molecular Formula: H2SO3
Synonyms: Dihydrogen Trioxosulfate, Aqueous sulfur dioxide
Recommended Use: Reducing agent, disinfectant, preservative in food and beverage processing, and in bleaching industries
Supplier/Manufacturer Details: Information available upon direct inquiry with chemical distributor
Emergency Contact: National Chemical Emergency Hotline, regional Poison Control Center
Classification: Corrosive to skin and eyes, hazardous to aquatic environment, respiratory irritant
GHS Label elements: Danger symbol (exclamation mark), corrosion pictogram
Signal Word: Danger
Hazard Statements: Causes severe skin burns and eye damage, possible respiratory tract irritation, may cause allergic reactions in sensitive individuals, harmful to aquatic life with long-lasting effects
Precautionary Statements: Avoid breathing mist, wear protective gloves/clothing/eye protection, use only outdoors or in well-ventilated areas, wash skin thoroughly after handling
Sulfurous Acid: H2SO3, solution in water, typically under 6% by weight
Impurities: Trace SO2 (sulfur dioxide), possible minor quantities of sulfate ion
Stabilizers/Preservatives: May contain trace amounts of anti-oxidants or acid scavengers from manufacturing
Inhalation: Move to fresh air, keep person at rest, seek medical advice if symptoms develop (coughing, sore throat, difficulty breathing)
Skin Contact: Remove contaminated clothing, rinse skin with water for at least 15 minutes, seek medical attention for persistent irritation or burns
Eye Contact: Rinse eyes cautiously with water for several minutes, remove contact lenses if present, continue rinsing, get immediate medical advice
Ingestion: Rinse mouth, do not induce vomiting, seek medical attention immediately; risk of corrosive burns to mucous membranes
Important Symptoms/Effects: Burning sensations, coughing, chest tightness, severe eye pain, red or blistered skin, ingestion may lead to gastrointestinal burns or perforation
Suitable Extinguishing Media: Use water spray, alcohol-resistant foam, dry chemical, or carbon dioxide; avoid direct streams that may cause spatter
Specific Hazards: Decomposition releases toxic and irritating sulfur oxides (SO2)
Special Protective Equipment: Firefighters should wear self-contained breathing apparatus, full protective gear to prevent contact with skin/eyes or inhalation of fumes
Firefighting Instructions: Keep containers cool with water spray; contain runoff to prevent environmental contamination
Unusual Fire Hazards: Heat or fire exposure may cause pressurization and rupture of containers
Personal Precautions: Wear chemical-resistant gloves, protective eyewear, and suitable respiratory protection, ventilate area
Environmental Precautions: Prevent entry to sewers or waterways, inform authorities if significant spills reach watercourses
Cleanup Methods: Neutralize with dilute alkaline solution (like sodium bicarbonate), absorb with inert material (sand, earth), collect in chemical waste containers, ventilate area well
Decontamination: Rinse area with large amounts of water after absorption and removal of residue, monitor for lingering vapors
Safe Handling: Only use in well-ventilated areas, avoid contact with eyes, skin and clothing, do not breathe vapors or mists, wash thoroughly after use
Storage Conditions: Store in cool, dry, well-ventilated place, keep container tightly closed, segregate from oxidizing agents, bases, and strong acids
Incompatible Materials: Bases, oxidizing agents, metals susceptible to acid corrosion
Special Precautions: Use non-metallic tools and equipment where feasible to prevent hazardous reactions, monitor for vapor buildup, segregate from incompatible substances
Engineering Controls: Use local exhaust ventilation, eyewash stations, and safety showers in chemical handling areas
Exposure Limits: Occupational exposure limit for sulfur dioxide (SO2), generally set at 2 ppm (ACGIH TLV); consult local occupational safety regulations
Personal Protection: Chemical-resistant gloves (nitrile, neoprene), splash goggles or face shield, acid-resistant apron or full suit, use properly fitted NIOSH-approved respirator if exposure exceeds limits or ventilation inadequate
Hygiene Measures: No eating, drinking, smoking in work area, remove contaminated clothing and launder before reuse
Appearance: Clear, colorless watery solution
Odor: Pungent, sharp, sulfurous smell (like burning match or struck flint)
pH: 1–2 (strongly acidic)
Boiling Point: Decomposes below 100°C, cannot be isolated as pure liquid
Melting Point: Unstable as pure compound
Solubility: Completely miscible with water
Vapor Pressure: Not determined for solution (high for SO2 component)
Density: Approximately 1.03–1.05 g/cm³ (dependant on concentration)
Decomposition: Readily decomposes to water and sulfur dioxide gas
Flash Point: Not applicable (non-flammable solution)
Chemical Stability: Unstable in concentrated form, decomposes rapidly releasing sulfur dioxide
Possible Reactions: Reacts strongly with bases and oxidizing agents, can cause hazardous pressure buildup in closed containers
Conditions to Avoid: High temperatures, exposure to air over time, contamination by metal ions
Hazardous Decomposition Products: Sulfur dioxide gas, sulfur trioxide at high temperatures
Polymerization: Will not occur under normal handling
Exposure Routes: Inhalation, skin and eye contact, ingestion
Acute Effects: Severe eye and skin irritation or burns, respiratory irritation, burning of mouth and throat on ingestion
Chronic Effects: Prolonged exposure can cause bronchitis, chronic cough, possibly increased risk of asthma attacks in vulnerable individuals
LD50 (Oral, Rat): No definitive data available for solution; SO2 gas toxicity data indicates moderate hazard
Carcinogenicity: Not classified as carcinogen by IARC or NTP, chronic exposure to SO2 has been associated with respiratory effects
Aquatic Toxicity: Toxic to aquatic organisms, may cause long-term adverse effects in aquatic environments
Persistence and Degradability: Breaks down quickly in water, forms sulfate and sulfur dioxide which lower pH and cause acidification
Bioaccumulation Potential: Low potential for bioaccumulation
Soil Mobility: Highly mobile in water, behaves as a strong acid, may leach into groundwater
Other Environmental Effects: Can cause rapid decline in dissolved oxygen and disrupt sensitive aquatic habitats, risk of fish kills in case of accidental discharge
Waste Disposal Methods: Neutralize remaining solutions using dilute sodium bicarbonate before disposal, collect and treat effluent in accordance with regional and national regulations
Container Disposal: Rinse containers thoroughly, dispose of as hazardous waste if contaminated, or recycle if appropriate and in compliance with local regulations
Precautions: Never dispose into sewage or natural water sources without proper treatment and permits, avoid uncontrolled releases
UN Number: UN2699
Shipping Name: Sulfurous Acid Solution
Transport Hazard Class: 8 (Corrosive Substance)
Packing Group: III
Label: Corrosive (Class 8)
Special Transport Requirements: Use corrosion-resistant containers; secure upright during transport; keep cool and well ventilated; make sure emergency response information available; report leaks or spills in transit immediately to relevant authorities
OSHA Status: Considered hazardous under Hazard Communication Standard
SARA Title III: Not subject to section 313 reporting, may be subject to community right-to-know
TSCA Status: Listed
WHMIS Classification (Canada): D1B (Poisonous and Infectious), E (Corrosive), D2B (Other Toxic Effects)
REACH (EU): Registered
Other Regulations: Subject to state and regional workplace safety, environmental protection and reporting requirements, consult local regulatory bodies for disposal and handling guidance
