Hydroiodic acid

Athanor · official

HI · 127.9124 g/mol

IUPAC name: iodane

Also called hydrogen iodide

Inorganic

Open in Athanor

Drawn from its SMILES with RDKit

DangerCauses severe skin burns and eye damage

Names and identifiers

IUPAC name: iodane
Synonyms: hydrogen iodide, Hydriodic acid, HYDROGEN IODIDE
+ 36 more
iodane, Hyriodic acid, Acido yodhidrico, Acide iodhydrique, Hydrogen iodide (HI), Anhydrous hydriodic acid, Hydrogen iodide, anhydrous, Iodure d'hydrogene anhydre, Yoduro de hidrogeno anhidro, 694C0EFT9Q, CHEBI:43451, EPA Pesticide Chemical Code 046912, DTXSID2044349, RefChem:789094, DTXCID0024349, 233-109-9, Jodwasserstoff, hydroiodide, MFCD00011347, HI, hydriodide, Hydriotic acid, Iodine, isotope of mass 125, Caswell No. 482C, Acide iodhydrique [French], Acido yodhidrico [Spanish], UNII-694C0EFT9Q, Hydrogeniodid, Iodwasserstoff, Wasserstoffiodid, HSDB 2155, iodure d'hydrogene, 53I, EINECS 233-109-9, Iodure d'hydrogene anhydre [French], organoiodine compound
Molecular formula: HI
Empirical formula: HI
Molecular weight: 127.9124 g/mol
Exact mass: 127.91230
CAS number: 10034-85-2
PubChem CID: 24841
Canonical SMILES: I
Isomeric SMILES: I
InChI: InChI=1S/HI/h1H
InChIKey: XMBWDFGMSWQBCA-UHFFFAOYSA-N
Molfile

Names, InChI and the identifiers from PubChem, retrieved 2026-10-14.

Physical properties

TemperaturePressureDensity

Appearance: Hydriodic acid appears as a colorless to yellow liquid with a pungent odor. Consists of a solution of hydrogen iodide in water. Fumes irritate the eyes and mucous membranes. Corrosive to metals and to tissue.[1]
4 values
From CAMEO Chemicals, the most authoritative source here.
Value As written Source
–shown Hydriodic acid appears as a colorless to yellow liquid with a pungent odor. Consists of a solution of hydrogen iodide in water. Fumes irritate the eyes and mucous membranes. Corrosive to metals and to tissue. [1] CAMEO Chemicals
– Hydrogen iodide, anhydrous appears as a colorless to yellow/brown gas with an acrid odor. Nonflammable. Toxic by inhalation. Strongly irritates skin, eyes and mucous membranes. Long-term inhalation of low concentrations or short-term inhalation of high concentrations may result in adverse health effects. Prolonged exposure to fire or intense heat may cause the container to rupture and rocket. [1] CAMEO Chemicals
– CBI; Liquid [2] EPA Chemical Data Reporting (CDR)
– COLOURLESS COMPRESSED LIQUEFIED GAS WITH PUNGENT ODOUR. [3] ILO-WHO International Chemical Safety Cards (ICSCs)
Melting point: -50.8 °C[3]
2 values
2 of 2 sources agree on it (most common value).
Value As written Source
−50.8 °Cshown -50.8 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
−50.8 °C -50.8 °C [5] PAC Chemical Database, U.S. Department of Energy
Boiling point: -35.38 °C @760 [mmHg][5]
2 values
2 of 2 sources agree on it (most common value).
Value As written Source
−35.5 °C -35.5 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
−35.4 °Cshown -35.38 °C @760 [mm Hg] [5] PAC Chemical Database, U.S. Department of Energy
Density: 5.66 @25 °C[5]
Solubility in water: Solubility in water, g/100ml at 20 °C: 42 (freely soluble)[3]
Vapor pressure: 5,938 mmHg at 25 °C[4]
3 values
2 of 3 sources agree on it (most common value).
Value As written Source
5938 mmHgshown 5,938 mm Hg at 25 °C [4] Hazardous Substances Data Bank (HSDB)cites Daubert, T.E., R.P. Danner. Physical and Thermodynamic Properties of Pure Chemicals Data Compilation. Washington, D.C.: Taylor and Francis, 1989.
5500 mmHg Vapor pressure, kPa at 20 °C: 733 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
5940 mmHg 5940 [mm Hg] @25 °C [5] PAC Chemical Database, U.S. Department of Energy

Value	As written	Source
–shown	Hydriodic acid appears as a colorless to yellow liquid with a pungent odor. Consists of a solution of hydrogen iodide in water. Fumes irritate the eyes and mucous membranes. Corrosive to metals and to tissue.	[1] CAMEO Chemicals
–	Hydrogen iodide, anhydrous appears as a colorless to yellow/brown gas with an acrid odor. Nonflammable. Toxic by inhalation. Strongly irritates skin, eyes and mucous membranes. Long-term inhalation of low concentrations or short-term inhalation of high concentrations may result in adverse health effects. Prolonged exposure to fire or intense heat may cause the container to rupture and rocket.	[1] CAMEO Chemicals
–	CBI; Liquid	[2] EPA Chemical Data Reporting (CDR)
–	COLOURLESS COMPRESSED LIQUEFIED GAS WITH PUNGENT ODOUR.	[3] ILO-WHO International Chemical Safety Cards (ICSCs)

Value	As written	Source
−50.8 °Cshown	-50.8 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
−50.8 °C	-50.8 °C	[5] PAC Chemical Database, U.S. Department of Energy

Value	As written	Source
−35.5 °C	-35.5 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
−35.4 °Cshown	-35.38 °C @760 [mm Hg]	[5] PAC Chemical Database, U.S. Department of Energy

Value	As written	Source
5938 mmHgshown	5,938 mm Hg at 25 °C	[4] Hazardous Substances Data Bank (HSDB)cites Daubert, T.E., R.P. Danner. Physical and Thermodynamic Properties of Pure Chemicals Data Compilation. Washington, D.C.: Taylor and Francis, 1989.
5500 mmHg	Vapor pressure, kPa at 20 °C: 733	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
5940 mmHg	5940 [mm Hg] @25 °C	[5] PAC Chemical Database, U.S. Department of Energy

Each value as its source reports it, with the source's number after it (listed under References). Where several sources report a property, the row shows the value most of them agree on, the rule the app uses; open the values to see every one.

Calculated

Heavy atoms: 1
Rings: 0
Aromatic rings: 0
Fraction sp³ carbons (Fsp3): 0
H-bond donors: 0 computed here · PubChem 1
H-bond acceptors: 0
Rotatable bonds: 0
TPSA (Å²): 0
Formal charge: 0
XLogP3: 0.9 PubChem
Complexity: 0 PubChem
Stereocenters: None
Double-bond geometry: None specified
Point group: C∞v of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

H0.79%
I99.21%

Isotope pattern

Each peak is a nominal mass with its abundance-weighted exact mass, as a percentage of the tallest, from IUPAC natural isotope abundances.

Computed from the structure with RDKit 2026.09 when this page was built, beside PubChem's own computed values from its record; where the two differ, both are shown.

Predicted

log P: 0.62 Crippen (Wildman and Crippen 1999)
log S (water solubility): -1.02 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 7.08 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 127.91
log P ≤ 5 (Crippen): 0.62
H-bond donors ≤ 5: 0
H-bond acceptors ≤ 10: 0

Passes all four rules.

Predictions, not measurements; each names its method. A measured log P, where a source reports one, is under Physical properties.

Safety

Danger

Harmonized EU classification (CLP Annex VI). Source [6].

Compressed gas
Corrosive

H314Causes severe skin burns and eye damage

Precautionary statements: P260, P264, P280, P301+P330+P331, P302+P361+P354, P304+P340, P305+P354+P338, P316, P321, P363, P405, P501

View all classifications (2)

[6] Regulation (EC) No 1272/2008 of the European Parliament and of the Council · DangerH314
[7] European Chemicals Agency (ECHA) · 391 reports · DangerH280, H314, H318, H331

Exposure limits

TLV: 0.01 ppm as TWA; A4 (not classifiable as a human carcinogen).[3]
MAK (Maximale Arbeitsplatz Konzentration): Skin absorption (H)[3]

First aid

Excerpt from ERG Guide 154 [Substances - Toxic and/or Corrosive (Non-Combustible)]: Refer to the "General First Aid" section. Specific First Aid: For corrosives, in case of contact, immediately flush skin or eyes with running water for at least 30 minutes. Additional flushing may be required. (ERG, 2024)[1]
Excerpt from ERG Guide 125 [Gases - Toxic and/or Corrosive]: Refer to the "General First Aid" section. Specific First Aid: In case of contact with liquefied gas, only medical personnel should attempt thawing frosted parts. In case of skin contact with hydrogen fluoride, anhydrous (UN1052), if calcium gluconate gel is available, rinse 5 minutes, then apply gel. Otherwise, continue rinsing until medical treatment is available. (ERG, 2024)[1]
General First Aid: · Call 911 or emergency medical service. · Ensure that medical personnel are aware of the material(s) involved, take precautions to protect themselves and avoid contamination. · Move victim to fresh air if it can be done safely. · Administer oxygen if breathing is difficult. · If victim is not breathing: -- DO NOT perform mouth-to-mouth resuscitation; the victim may have ingested or inhaled the substance. -- If equipped and pulse detected, wash face and mouth, then give artificial respiration using a proper respiratory medical device (bag-valve mask, pocket mask equipped…[8]
General First Aid: · Call 911 or emergency medical service. · Ensure that medical personnel are aware of the material(s) involved, take precautions to protect themselves and avoid contamination. · Move victim to fresh air if it can be done safely. · Administer oxygen if breathing is difficult. · If victim is not breathing: -- DO NOT perform mouth-to-mouth resuscitation; the victim may have ingested or inhaled the substance. -- If equipped and pulse detected, wash face and mouth, then give artificial respiration using a proper respiratory medical device (bag-valve mask, pocket mask equipped…[8]

Storage

Fireproof if in building. Separated from metals and oxidants. Keep in a well-ventilated room.[3]
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.[4]
Materials THAT ARE toxic AS stored OR THAT CAN decompose INTO toxic components ... Should BE stored IN A COOL WELL ventilated place, OUT OF THE direct RAYS OF THE SUN, AWAY FROM areas OF HIGH FIRE hazard, & should BE periodically inspected. Incompatible materials should BE isolated. ...[4]
Keep protected from light and air, preferably not above 3 °C.[4]

Incompatibilities

Reacts WITH water OR steam TO produce toxic & corrosive fumes.[4]
Magnesium burns momentarily IN hydrogen iodide.[4]
Molten potassium chlorate ignites IN hydrogen iodide.[4]
WHEN hydrogen iodide IS passed through fuming nitric ACID, EACH bubble produces A RED flame WITH separation OF iodide.[4]

Always read the supplier’s safety data sheet before working with it.

Literature

Reading PubChem, OpenAlex and GSRS…

Bioactivity

Reading ChEMBL…

References

[1]CAMEO Chemicals · Public domain (NOAA) · via PubChem · retrieved 2026-10-14
[2]EPA Chemical Data Reporting (CDR) · Public domain (US EPA) · via PubChem · retrieved 2026-10-14
[3]ILO-WHO International Chemical Safety Cards (ICSCs) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
[4]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
[5]PAC Chemical Database, U.S. Department of Energy · Public domain (US DOE) · via PubChem · retrieved 2026-10-14
[6]Regulation (EC) No 1272/2008 of the European Parliament and of the Council · EU reuse policy, CC BY 4.0 · via PubChem · retrieved 2026-10-14
[7]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[8]Emergency Response Guidebook (ERG) · Public domain (US DOT) · via PubChem · retrieved 2026-10-14
·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
·Literature on PubChem

Data last updated 2026-10-14.