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Substance Name: Hydrogen Iodide, anhydrous
Chemical Formula: HI
Common Synonyms: Hydroiodic acid (but only in its aqueous form, anhydrous form is a separate hazard)
CAS Number: 10034-85-2
Hydrogen iodide stands out for its sharp, pungent odor and its reputation as a suffocating, non-flammable gas under room temperature. Its uses are usually tied to both laboratory synthesis and some industrial processes, particularly in areas dealing with organic chemistry. Recognizing this compound’s identity matters in practice, because confusion with hydroiodic acid or other hydrogen halides could result in dangerous decisions for both safety practices and medical treatment.
Acute Risks: Rapid, severe irritation to eyes, skin, and lungs, even with brief exposure
Chronic Risks: Prolonged contact leads to bronchitis, teeth and gum issues, and long-term respiratory problems
Hazard Symbols: Corrosive, Toxic, Irritant
Key Dangers: Breathing the gas can damage tissue along respiratory pathways. Moist areas like eyes, nose, and throat react harshly on contact. Direct skin exposure may cause burns. Exposure above safety limits can bring headaches, dizziness, chest tightness, or worse.
Safety Factor: Failing to recognize urgency during a leak or spill could cost someone dearly—prevention depends on knowing the specific risks tied to hydrogen iodide, not casually grouping it with other acids or halogen gases.
Main Component: Hydrogen iodide gas (HI), often near 100 percent purity in commercial settings
Impurities: Traces of water vapor and iodine possible depending on storage and transport
Some chemical stocks may absorb moisture from air, so gaseous and liquid properties can overlap slightly, with risks changing along with composition shifts. Safety data only remain relevant if the material is stored and handled to avoid unintended chemical changes.
Inhalation: Get affected person to fresh air at once, support breathing, and call emergency care. Avoid breathing vapors during rescue. Oxygen or artificial respiration can save lives if breathing is difficult.
Skin Contact: Rinse thoroughly with large amounts of water; do not scrub. Remove any clothing splashed with the gas. Burns or blisters call for immediate medical attention.
Eye Contact: Rinse eyes under running water for at least fifteen minutes, lifting eyelids occasionally. Ophthalmologic care is needed—eye injury from hydrogen iodide can escalate without prompt treatment.
Ingestion: Not a likely route because it’s a gas, but if swallowed, do not induce vomiting—seek medical help straight away.
Treating exposure quickly and decisively can mean the difference between mild irritation and severe injury, so education of all personnel before an incident occurs is just as important as emergency procedures.
Flammability: Not considered flammable, but decomposes to release iodine vapors at high temperatures, which pose their own risks.
Suitable Extinguishing Media: Use agents appropriate for combustibles around the gas—hydrogen iodide itself does not ignite, but containers may explode if heated.
Special Hazards: Reaction with certain metals or oxidizers forms toxic and corrosive fumes.
Protection for Firefighters: Full-body chemical suits and self-contained breathing apparatus. Water mist can help disperse vapors.
Fire crews must look beyond whether the chemical burns and focus instead on containment, vapor dispersion, and protecting against secondary hazards, including toxic smoke and corrosive runoff.
Small Leaks: Ventilate the area, use local exhaust, and evacuate unnecessary personnel.
Large Releases: Seal off the space and contact specialized emergency response teams.
Personal Protection: Chemical-resistant gloves, face shield, protective clothing, and respiratory protection as a baseline.
Environmental Protection: Prevent entry into drains or watercourses. Notify environmental authorities if a significant quantity escapes.
Quick judgment makes a difference. Training all hands to recognize a vapor release, rapidly leave the area, and report it right—those steps keep everyone safer than relying on wishful thinking or luck.
Safe Handling: Avoid direct contact. Use only in well-ventilated locations or inside chemical hoods designed for highly reactive gases.
Storage Conditions: Store in tightly closed pressurized containers built for corrosive gases. Keep away from water, bases, oxidizers, and metals.
Temperature Concerns: Do not allow storage tanks to overheat or freeze.
Storage rooms need solid alarms and regular inspections—complacency about containers, seals, or monitoring equipment invites disaster. Chemical compatibility charts must get checked, and anything that isn’t compatible with HI doesn’t go on the same shelf.
Engineering Controls: Positive ventilation, gas detectors, automatic shutoffs
Respiratory Protection: Full-face air-purifying respirator for small exposures, supplied-air respirators or SCBA for high-risk jobs
Gloves: Heavy-duty chemical-resistant gloves
Eye Protection: Chemical splash goggles plus a face shield
Skin Protection: Full-body suits resistant to gas penetration
Setting up layered protection ensures workers aren’t relying on a single line of defense, especially where a surprise vapor release can cause instant harm. Routine fit checks for respirators and gloves really do make the difference between temporary discomfort and a trip to the ER.
Appearance: Colorless to pale yellow gas with a strong, choking odor
Molecular Weight: Roughly 128 g/mol
Boiling Point: -35°C
Melting Point: -51°C
Solubility: Extremely soluble in water, forming hydroiodic acid
Vapor Pressure: Substantial at room temperature
These characteristics shape storage, use, and emergency approaches—rapid evaporation and high solubility make spills and leaks immediately hazardous and tough to contain unless plans anticipate them.
Chemical Stability: Stable under recommended storage, but decomposes at elevated temperatures to release iodine and hydrogen
Incompatibilities: Reacts violently with moisture, strong bases, metals, oxidizing agents
Hazardous Decomposition: Iodine, hydrogen, and other toxic vapors
Once the tank or pipe leaks, chemical instability speeds up. Even trace moisture in the air can accelerate dangerous reactions, so having everything dry and properly sealed isn’t just about efficiency—it’s a non-negotiable safety matter.
Acute Effects: Severe eye, nose, throat, and lung irritation, cough, trouble breathing, headaches
Chronic Effects: Potential for dental erosion, skin burns, ulceration, chronic bronchitis
Routes of Exposure: Inhalation remains most common, but eye and skin absorption matter too
Exposure to hydrogen iodide rarely produces just mild symptoms—most cases trigger fast, harsh effects. Workers should know what overexposure feels like because prompt decision-making can literally save someone from life-changing injuries.
Aquatic Toxicity: High—harmful to fish and invertebrates if released untreated
Bioaccumulation: Not likely to build up in food chains, as it reacts quickly with ambient moisture and substances
Environmental Fate: Converts to hydroiodic acid instantly when in contact with water, lowering aquatic pH and increasing threat to habitats
Whenever hydrogen iodide gets into waterways, local populations and ecosystems may face real, lasting damage. This isn’t an ‘out of sight, out of mind’ waste. Emphasizing containment and spill-prevention over cleanup shifts the conversation from damage control to protection.
Preferred Disposal: Controlled neutralization in specialized treatment facilities
Prohibited Disposal: No dumping into drains or water systems
Container Disposal: Decontaminate before recycling or disposal
Any waste handling goes hand-in-hand with ethical responsibility. Cutting corners by pouring leftovers outside leads directly to environmental harm and health threats. Companies and labs need ongoing training, third-party oversight, and clear chains of custody for any waste connected to hydrogen iodide.
UN Number: 2197 (Hydrogen Iodide, Anhydrous)
Hazard Class: Corrosive gas
Packing Group: II
Transportation means moving a severe inhalation and environmental hazard through populated areas. Containers need intensive checks for leaks, and workers need to double-check labels to avoid accidental mixing or misrouting. Strict rules exist for a reason—the risks from a truck or tank car spill don’t stop at the plant gate.
Occupational Limits: OSHA: 2 parts per million (skin)
SARA/Title III: Classified as an extremely hazardous substance
Other Policies: Covered under local and national reporting rules
Regulations serve as a floor, not a ceiling, for best practice. True safety comes from exceeding minimum requirements. Regular reviews of chemical hygiene plans, thorough training, and fostering a culture where compliance is the starting point—not the only goal—provides real protection for workers, neighbors, and the environment alike.
