Substance profile
Hydrogen iodide
Hydrogen iodide is a colorless gas; fumes in moist air with an acrid odor.
01 · Identification
What Hydrogen iodide is
Hydrogen iodide is a colorless gas; fumes in moist air with an acrid odor. Its molecular formula is HI and its molecular weight is 127.912 g/mol. It boils at -35.1 °C, melts at -50.8 °C.
Under the GHS it carries the signal word Danger. It is classed as corrosives.
02 · Identifiers
Hydrogen iodide identifiers and molecular data
Hydrogen iodide CAS number and EC number
Hydrogen iodide molecular formula and molecular weight
03 · GHS classification
Hydrogen iodide hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
Hydrogen iodide pictograms and signal word
Hydrogen iodide hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| Skin corrosion/irritation GHS chapter 3.2 | Category 1A or 1B or 1C | H314 | GHS05 |
Where two values are shown with “or”, the hazard statement is shared by more than one category or by more than one class, and the code alone does not say which. H272, for example, belongs to oxidising liquids and to oxidising solids — the physical state decides. The binding answer for a specific entry is in the CLP Annex VI table itself.
Hydrogen iodide hazard statements (H-codes)
| Code | Hazard statement |
|---|---|
| H314 | Causes severe skin burns and eye damage. |
This page lists only the codes assigned to Hydrogen iodide. The full reference lives on the hazard statements hub, the precautionary statements hub and the GHS pictograms hub.
Safety Data Sheet
Getting an SDS for Hydrogen iodide
A Safety Data Sheet is written for a product, not for a substance: the supplier of the grade you actually buy issues it, so two suppliers of Hydrogen iodide issue two different sheets. That is why there is no single authoritative SDS for a substance to download — what there is, is the job of collecting the sheets for the products you hold and keeping them current as suppliers revise them.
04 · Precautionary statements
Hydrogen iodide precautionary statements
CLP Annex VI assigns 5 precautionary statements to Hydrogen iodide. They are grouped the way a label groups them: what to do before handling, what to do when something has already happened, how to store it and how to dispose of it.
Prevention
What to do before and during handling so the hazard never happens.
Response
What to do once exposure, spillage or fire has already happened.
Reading the notation. … is a blank the supplier fills in — not a truncated sentence.· [square brackets] mark a part printed only when it applies.
05 · Names in the regulation
Hydrogen iodide name in 23 EU languages
CLP Annex VI Part 3 is published in every language edition of the regulation, and the identification column is written out in each of them. Nothing below is translated by us: each line is the name as that edition prints it. Under Art. 18(2) the substance name from Annex VI is a lawful product identifier, so this is the wording to put on a label going to that market — and where the cell lists several designations, any one of them qualifies.
| Language | Name in CLP Annex VI Part 3 |
|---|---|
| Bulgarian български | водороден йодид |
| Spanish español | Yoduro de hidrógeno |
| Czech čeština | jodovodík |
| Danish dansk | hydrogeniodid |
| German Deutsch | Hydrogeniodid Iodwasserstoff |
| Estonian eesti | vesinikjodiid |
| Greek ελληνικά | υδροϊώδιο |
| English English | hydrogen iodide |
| French français | iodure d'hydrogène |
| Croatian hrvatski | vodikov jodid |
| Italian italiano | ioduro di idrogeno |
| Latvian latviešu | ūdeņraža jodīds |
| Lithuanian lietuvių | vandenilio jodidas |
| Hungarian magyar | hidrogén-jodid (gáz) |
| Maltese Malti | jodur tal-idroġenu |
| Dutch Nederlands | waterstofjodide |
| Polish polski | jodowodór |
| Portuguese português | iodeto de hidrogénio |
| Romanian română | iodură de hidrogen |
| Slovak slovenčina | jodovodík |
| Slovenian slovenščina | vodikov jodid |
| Finnish suomi | jodivety, vedetön |
| Swedish svenska | vätejodid |
All 23 language editions of Annex VI carry this entry. Irish is the twenty-fourth official EU language and has no line here for a different reason: no consolidated CLP text has ever been published in Irish, so there is no Irish edition of Annex VI to quote a name from. Source: consolidated CLP, CELEX 02008R1272, language editions. © European Union, https://eur-lex.europa.eu — only the electronic Official Journal of the European Union is authentic.
06 · Label elements
Hydrogen iodide GHS label elements
Everything CLP Annex VI fixes for Hydrogen iodide, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Danger
Hydrogen iodide
- Causes severe skin burns and eye damage.
- Do not breathe dust/fume/gas/mist/vapours/spray.
- Wear protective gloves/protective clothing/eye protection/face protection/hearing protection/…
- IF SWALLOWED:
- Immediately call a POISON CENTER/doctor/…
- Do NOT induce vomiting.
Supplier name, address and telephone number· Product identifier·Nominal quantity
Need this as an actual label? Open Hydrogen iodide in the GHS label constructor →
07 · Physical and chemical properties
Hydrogen iodide properties
Every value is shown with the conditions it was measured under and the source it came from. Where sources disagree, all values are listed rather than one being picked — the difference is usually a different form of the substance, not an error.
Hydrogen iodide boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | -35.1 °C (-31.2 °F) | at 760 mmHg | HSDB |
| -35.5 °C (-31.9 °F) | ICSC | ||
| -35.38 °C (-31.7 °F) | at 760 mmHg | DOE PAC |
Hydrogen iodide melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | -50.8 °C (-59.4 °F) | HSDB |
Hydrogen iodide density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 5.66 g/cm³ | at 25 °C | DOE PAC |
| 0.0057 g/cm³ | at 0 °C | HSDB | |
| 1.7 g/cm³ | at 127 °C | HSDB |
Hydrogen iodide solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | Solubility in water, g/100ml at 20 °C: 42 (freely soluble) | at 20 °C | ICSC |
| Extremely soluble in water; 234 g/100 g water at 10 °C; 900 g/100 g water at 0 °C | at 10 °C | HSDB |
Hydrogen iodide vapor pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor pressure | 5498 mmHg | at 20 °C | ICSC |
| 5938 mmHg | at 25 °C | HSDB | |
| 5940 mmHg | at 25 °C | DOE PAC |
Hydrogen iodide vapor density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor density | 4.4 (air = 1) | HSDB |
Hydrogen iodide critical temperature and pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Critical temperature and pressure | 151 °C (303.8 °F) | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
08 · Fire and explosion
Hydrogen iodide fire and explosion behaviour
These are descriptions rather than measured values, so they are kept out of the table above and quoted here with the source that reported them.
Hydrogen iodide fire potential
Ignites on contact with magnesium; perchloric acid; potassium + heat; potassium chlorate + heat; oxidants.
Source: Hazardous Substances Data Bank (HSDB)
09 · Handling and storage
Hydrogen iodide storage and handling
Hydrogen iodide safe storage
Fireproof if in building. Separated from metals and oxidants. Keep in a well-ventilated room.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
Hydrogen iodide storage conditions
Hydroidic acid must be stored to avoid contact with strong acids (such as hydrochloric, sulfuric and nitric), chemically active metals (such as potassium, sodium, magnesium and zinc), and strong oxidizers (such as chlorine, bromine, and fluorine) since violent reactions occur. Store in tightly closed containers in a cool, well vented area away from heat and moisture. Protect storage containers from physical damage. Procedures for the handling, use and storage of cylinders should be in compliance with OSHA 1910.101 and 1910.169 as with the recommendations of the Compressed Gas Association.
Source: Hazardous Substances Data Bank (HSDB)
Hydrogen iodide incompatible materials
REACTS WITH WATER OR STEAM TO PRODUCE TOXIC & CORROSIVE FUMES.
Source: Hazardous Substances Data Bank (HSDB)
Planning storage for a mix of chemicals? Check Hydrogen iodide in the storage compatibility matrix →
10 · Transport
Hydrogen iodide UN number and transport classification
Transport classification is a separate system from the GHS classification above. It decides how a package is marked and how a load may be carried; it does not follow from the workplace label, and the workplace label does not follow from it. The entries below are linked by CAS number, never by name.
Hydrogen iodide under UN 2197 — shipping name, class and packing group
Europe · ADR 2025, Table A
| Proper shipping name (3.1.2) | Class | Classification code | PG | Labels (column 5) |
|---|---|---|---|---|
| HYDROGEN IODIDE, ANHYDROUS | 2 | 2TC | — | |
Source: ADR 2025, Table A of Chapter 3.2 · ECE/TRANS/352 Vol. I (UNECE). Class 2 is “Gases” (ADR 2.1.1.1).
United States · 49 CFR 172.101 Hazardous Materials Table
| Proper shipping name (column 2) | Class or division | PG | Labels (column 6) |
|---|---|---|---|
| Hydrogen iodide, anhydrous | 2.3 | — | |
Source: 49 CFR 172.101 Hazardous Materials Table · eCFR, revision 2026-08-03. Class 2.3 is “Poisonous gas” (49 CFR 173.2).
11 · Questions
Hydrogen iodide — frequently asked questions
What is the CAS number of Hydrogen iodide?
The CAS number of Hydrogen iodide is 10034-85-2. Its EC number is 233-109-9.
What is the chemical formula of Hydrogen iodide?
The molecular formula of Hydrogen iodide is HI and its molecular weight is 127.912 g/mol.
What does a Hydrogen iodide label have to show?
Under CLP Annex VI the label for Hydrogen iodide carries the pictograms Gas cylinder and Corrosion and the signal word is Danger.
Is Hydrogen iodide flammable?
CLP Annex VI assigns Hydrogen iodide no flammability hazard class. That is not a statement that it cannot burn: the harmonised list only records the hazards that were assessed for it.
Is Hydrogen iodide a carcinogen?
CLP Annex VI records no harmonised carcinogenicity classification for Hydrogen iodide. Annex VI is a list of agreed classifications, not a list of substances found safe, so this is an absence of a classification rather than a clean bill of health.
What is the boiling point of Hydrogen iodide?
The boiling point reported for Hydrogen iodide is -35.1 °C (-31.2 °F), at 760 mmHg (HSDB).
What is the melting point of Hydrogen iodide?
The melting point reported for Hydrogen iodide is -50.8 °C (-59.4 °F) (HSDB).
How should Hydrogen iodide be stored?
Hydroidic acid must be stored to avoid contact with strong acids (such as hydrochloric, sulfuric and nitric), chemically active metals (such as potassium, sodium, magnesium and zinc), and strong oxidizers (such as chlorine, bromine, and fluorine) since violent reactions occur. Store in tightly closed containers in a cool, well vented area away from heat and moisture. Protect storage containers from physical damage. Procedures for the handling, use and storage of cylinders should be in compliance with OSHA 1910.101 and 1910.169 as with the recommendations of the Compressed Gas Association. (Hazardous Substances Data Bank (HSDB))
Nearby
Substances next to Hydrogen iodide
Keep going: substances starting with H, or search the whole database by name, CAS number, pictogram or signal word.