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Chemical Name: Selenious Acid
Synonyms: Selenium dioxide solution, Selenium(IV) oxide hydrate, Selenic acid
CAS Number: 7783-00-8
Molecular Formula: H2SeO3
Molecular Weight: 128.98 g/mol
Recommended Use: Manufacture of chemicals, laboratory reagent, glass manufacturing, catalyst
Supplier Details: Chemical manufacturer’s address, emergency contact telephone, and responsible department
Classification: Acute toxicity oral (Category 2), Acute toxicity inhalation (Category 2), Acute toxicity dermal (Category 2), Skin corrosion/irritation (Category 1B), Serious eye damage/irritation (Category 1), Specific target organ toxicity
Pictograms: Skull and crossbones, Corrosive
Signal Word: Danger
Hazard Statements: Fatal if swallowed, Fatal in contact with skin, Fatal if inhaled, Causes severe skin burns and eye damage
Precautionary Statements: Do not breathe fumes, wash hands thoroughly after handling, use only outdoors or in a well-ventilated area, avoid release to the environment, wear protective gloves, protective clothing, and eye/face protection
Substance: Selenious Acid
Purity: Typically >95%
Ingredient: Selenious acid
CAS Number: 7783-00-8
Concentration: 100% for pure samples, lower concentrations in aqueous solution
Impurities: Trace amounts of selenium dioxide possible depending on manufacturing process
General Advice: Remove contaminated clothing and shoes, seek medical advice immediately, rinse contaminated clothing with water before re-use
Inhalation: Move person to fresh air, keep at rest, provide artificial respiration if breathing stops, consult a physician
Skin Contact: Rinse skin immediately with plentiful water for at least 15 minutes, remove contaminated clothing, get medical attention quickly
Eye Contact: Rinse eyes with water for 15 minutes or longer, lift eyelids occasionally, obtain medical care without delay
Ingestion: Do not induce vomiting, rinse mouth with water, seek emergency medical attention immediately
Suitable Extinguishing Media: Use dry chemical, carbon dioxide, water spray, or alcohol-resistant foam
Unsuitable Extinguishing Media: Avoid concentrated water jet on the substance
Combustion Hazards: Releases toxic selenium oxides, hydrogen selenide, irritating or corrosive vapors
Protective Equipment for Firefighters: Use self-contained breathing apparatus (SCBA), full protective gear, keep containers cool with water spray
Specific Methods: Evacuate area, contain water used for extinction to prevent environmental contamination
Personal Precautions: Evacuate non-essential personnel, ventilate area, avoid breathing vapors or aerosols, wear suitable PPE
Environmental Precautions: Prevent run-off into sewers and waterways, inform environmental authorities
Spill Response: Use inert absorbents like sand or vermiculite, avoid direct contact, collect and place in containers for proper disposal, decontaminate area, avoid raising dust or aerosols
Handling: Avoid contact with skin, eyes, and clothing, use only in fume hood or well-ventilated space, prevent inhalation of vapors or dust, keep away from incompatible materials such as strong reducing agents or organics, wash thoroughly after handling
Storage: Store in tightly closed, corrosion-resistant containers, keep in cool, dry, well-ventilated area, segregate from food and incompatible substances, label storage area clearly, provide secondary containment to manage leaks
Occupational Exposure Limits: Selenious acid TWA (OSHA): 0.2 mg Se/m³, ACGIH TLV: 0.2 mg Se/m³
Engineering Controls: Chemical fume hood, eye wash station, safety shower, handle under local exhaust ventilation
Personal Protective Equipment: Chemical-resistant gloves (neoprene, nitrile), splash goggles or face shield, lab coat or chemical-resistant apron, respiratory protection if exposure limits may be exceeded, avoid eating, drinking, or smoking in work area
Appearance: Colorless to pale-yellow crystalline solid or syrupy solution
Odor: Odorless
Odor Threshold: Not available
pH: Approximately 1 (strongly acidic aqueous solution)
Melting Point: Solid decomposes, solution remains liquid
Boiling Point: Decomposes (does not boil intact)
Solubility in Water: Highly soluble
Vapor Pressure: Not measurable at ambient temperature
Flash Point: Not applicable
Upper/Lower Flammability Limits: Not flammable
Density: Approximately 2.5 g/cm³ for solid
Partition Coefficient (log Kow): Not determined
Evaporation Rate: Not relevant for stable solutions
Auto-ignition Temperature: Not self-igniting
Chemical Stability: Selenious acid remains stable under recommended storage conditions, but decomposes at elevated temperatures or in the presence of sunlight
Reactivity: Reacts violently with strong reducing agents, metals in powder form, and organic materials
Condition to Avoid: Excessive heat, moisture, incompatible substances, light
Hazardous Decomposition Products: Releases toxic selenium oxides, selenium dioxide, hydrogen selenide, and other corrosive gases
Polymerization: Does not undergo hazardous polymerization
Acute Toxicity: Extremely toxic by ingestion, skin contact, and inhalation; oral LD50 (rat): 7-10 mg/kg
Symptoms of Exposure: Severe irritation, burning pain, nausea, vomiting, headache, garlic odor on breath, metallic taste, convulsions, collapse
Chronic Effects: May cause selenosis, symptoms include hair loss, nail brittleness, fatigue, irritability, and neurological effects
Carcinogenicity: Not listed as a carcinogen by IARC, NTP, or OSHA; evidence insufficient for human cancer risk
Mutagenicity/Reproductive Effects: Data limited; high exposures may damage reproductive organs in experimental animals
Routes of Exposure: Inhalation, skin and eye contact, ingestion
Toxicity: Highly toxic to aquatic life, both acute and chronic effects on fish, invertebrates, and algae
Persistence and Degradability: Selenium compounds are not readily biodegradable; persist in ecosystems
Bioaccumulation: Selenium accumulates in living organisms and moves up the food chain, risking biomagnification
Mobility in Soil: Mobile under some environmental conditions, may leach to groundwater
Effects on the Environment: Harmful even at low concentrations, disrupts growth, feeding, and reproduction of aquatic and terrestrial organisms; long-term contamination possible
Disposal Methods: Collect as hazardous chemical waste, deliver to authorized hazardous waste treatment or incineration facility, prevent release to the environment
Contaminated Packaging: Treat empty containers as hazardous waste, rinse thoroughly, then dispose in accordance with regulatory requirements
Special Precautions: Avoid direct disposal into sewage, landfill, or natural waters; follow local, national, and international rules for hazardous waste
UN Number: 3283
Proper Shipping Name: Selenious acid
Transport Hazard Class: 6.1 (Toxic substances)
Packing Group: I (great danger)
Label: Toxic, Corrosive
Environmental Hazards: Marine pollutant, must not be transported with foodstuffs; shipment requires documentation, warning placards, and trained personnel
Global Regulations: Listed on TSCA Inventory (US), EINECS/ELINCS (Europe), DSL (Canada), AICS (Australia), and other major chemical registers
OSHA Status: Hazardous substance under 29 CFR 1910.1200
SARA Title III: Section 313 toxic release inventory listed
RCRA Status: Characteristic hazardous waste (EPA Hazardous Waste Number: P102)
Right to Know: Pennsylvania, New Jersey, and Massachusetts have Selenious acid listed as a hazardous substance
International: Transport regulated under ADR/RID, IMDG Code, IATA/ICAO standards; must comply with proper labeling, documentation, and emergency response planning
