Iodine

Athanor · official

I₂ · 253.8089 g/mol

IUPAC name: molecular iodine

Also called diiodine, molecular iodine

Inorganic

Open in Athanor

Drawn from its SMILES with RDKit

WarningHarmful in contact with skin · Harmful if inhaled · Very toxic to aquatic life

Names and identifiers

IUPAC name: molecular iodine
Synonyms: diiodine, molecular iodine, Molecular iodine
+ 37 more
Diiodine, Iodine crystals, Iodine sublimed, Tincture iodine, Vistarin, Eranol, Iodio, Iode, Iosan superdip, Jood, Iodine tincture, Iodine colloidal, Actomar, Iodine Tincture USP, diiodane, iodium, Jodosan, Tegodyne, Iodum, Iodine strong, DTXSID7034672, NSC 42355, Iodine mild, NSC-42355, 9679TC07X4, DTXCID5014672, CHEBI:17606, CHEBI:24859, NSC42355, exceed, Iodine 127, Bovadine, Megadyne, Monodyne, Optidyne, Pentadyne, Predyne
Molecular formula: I₂
Empirical formula: I
Molecular weight: 253.8089 g/mol
Exact mass: 253.80895
CAS number: 7553-56-2
PubChem CID: 807
Canonical SMILES: II
Isomeric SMILES: II
InChI: InChI=1S/I2/c1-2
InChIKey: PNDPGZBMCMUPRI-UHFFFAOYSA-N
Molfile

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

Physical properties

TemperaturePressureDensity

Appearance: Violet solid.[6]
8 values
From Hazardous Substances Data Bank (HSDB), the most authoritative source here.
Value As written Source
– Violet-black crystals with a metallic luster and a sharp odor. Mp: 113.5 °C, bp: 185 °C. Emits toxic vapor at room conditions; vapor becomes visibly purple when its concentration builds up in a confined space. Nearly insoluble in water but very soluble in aqueous solutions of iodides. [1] CAMEO Chemicals
– Wet Solid; CBI; Large Crystals [2] EPA Chemical Data Reporting (CDR)
– BLUISH BLACK OR DARK PURPLE CRYSTALS WITH PUNGENT ODOUR. [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– Violet-black crystals with metallic luster and a sharp, characteristic odor. [4] Occupational Safety and Health Administration (OSHA)
– Violet solid with a sharp, characteristic odor. [5] The National Institute for Occupational Safety and Health (NIOSH)
– Rhombic, violet-black crystals with metallic luster [6] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J. Sax's Dangerous Properties of Industrial Materials. 10th ed. Volumes 1-3 New York, NY: John Wiley & Sons Inc., 1999., p. V3: 2095
–shown Violet solid. [6] Hazardous Substances Data Bank (HSDB)cites NIOSH. NIOSH Pocket Guide to Chemical Hazards & Other Databases. U.S. Department of Health & Human Services, Public Health Service, Center for Disease Control & Prevention. DHHS (NIOSH) Publication No. 2001-145 (CD-ROM) August 2001.
– Heavy, grayish-black plates or granules having a metallic luster [6] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J. Sr.; Hawley's Condensed Chemical Dictionary 14th Edition. John Wiley & Sons, Inc. New York, NY 2001., p. 612
Odor: Sharp characteristic odor.[6]
Melting point: 113.7 °C[7]
5 values
5 of 5 sources agree on it (most common value).
Value As written Source
113 °C 236 °F (NIOSH, 2024) [1] CAMEO Chemicals
114 °C 114 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
113 °C 236 °F [4] Occupational Safety and Health Administration (OSHA)
113.7 °Cshown 113.7 °C [7] PAC Chemical Database, U.S. Department of Energy
113 °C 236 °F [5] The National Institute for Occupational Safety and Health (NIOSH)
Boiling point: 184.4 °C @760 [mmHg][7]
5 values
5 of 5 sources agree on it (most common value).
Value As written Source
185 °C 365 °F at 760 mmHg (NIOSH, 2024) [1] CAMEO Chemicals
184 °C 184 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
185 °C 365 °F [4] Occupational Safety and Health Administration (OSHA)
184.4 °Cshown 184.4 °C @760 [mm Hg] [7] PAC Chemical Database, U.S. Department of Energy
185 °C 365 °F [5] The National Institute for Occupational Safety and Health (NIOSH)
Density: 4.933 @25 °C[7]
5 values
5 of 5 sources agree on it (most common value).
Value As written Source
– 4.93 (NIOSH, 2024) - Denser than water [1] CAMEO Chemicals
– Relative density (water = 1): 4.9 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– 4.93 [4] Occupational Safety and Health Administration (OSHA)
–shown 4.933 @25 °C [7] PAC Chemical Database, U.S. Department of Energy
– 4.93 [5] The National Institute for Occupational Safety and Health (NIOSH)
1 more value was reported but failed the checks (unreadable or out of range), so it is not shown.
Solubility in water: Solubility in water, g/100ml at 20 °C: 0.03[3]
7 values
From ILO-WHO International Chemical Safety Cards (ICSCs), the most authoritative source here.
Value As written Source
– 0.01 % (NIOSH, 2024) [1] CAMEO Chemicals
– For more Solubility (Complete) data for IODINE, ELEMENTAL (9 total), please visit the HSDB record page. [6] Hazardous Substances Data Bank (HSDB)
– 197 g/kg in carbon disulfide at 25 °C; 19.2 g/kg in carbon tetrachloride at 25 °C; 337.3 g/kg in ether at 25 °C; 164.0 g/kg in benzene at 25 °C; 27.1 g/kg in ethanol at 25 °C; 49.7 g/kg in chloroform at 25 °C; 49.7 g/kg in chloroform at 25 °C; 13.2 g/kg in n-hexane at 25 °C; 97 g/kg in butan-2-ol at 25 °C; 157 g/kg in ethyl acetate at 25 °C; 182.5 g/kg in toluene at 25 °C [6] Hazardous Substances Data Bank (HSDB)cites Gerhartz, W. (exec ed.). Ullmann's Encyclopedia of Industrial Chemistry. 5th ed.Vol A1: Deerfield Beach, FL: VCH Publishers, 1985 to Present., p. A14: 382 (1989)
– 14.6 g/100 g in bromoethane at 25 °C; 1.73 g/100 g in n-heptane at 25 °C; 9.7 g/100 g in glycerol at 25 °C; 33.7 g/100 g in diethyl ether at 25 °C; 19.7 g/100 g in carbon disulfide at 25 °C [6] Hazardous Substances Data Bank (HSDB)cites Seiler, H.G., H. Sigel and A. Sigel (eds.). Handbook on the Toxicity of Inorganic Compounds. New York, NY: Marcel Dekker, Inc. 1988., p. 330
– For more Solubility (Complete) data for IODINE, ELEMENTAL (8 total), please visit the HSDB record page. [6] Hazardous Substances Data Bank (HSDB)
–shown Solubility in water, g/100ml at 20 °C: 0.03 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– 0.01% [5] The National Institute for Occupational Safety and Health (NIOSH)
log P: 2.49[3]
2 values
2 of 2 sources agree on it (most common value).
Value As written Source
– log Kow = 2.49 [6] Hazardous Substances Data Bank (HSDB)cites Hansch, C., Leo, A., D. Hoekman. Exploring QSAR - Hydrophobic, Electronic, and Steric Constants. Washington, DC: American Chemical Society., 1995., p. 3
–shown 2.49 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
Vapor pressure: Vapor pressure, kPa at 25 °C: 0.04[3]
5 values
3 of 5 sources agree on it (most common value).
Value As written Source
0.3 mmHg 0.3 mmHg at 77 °F (NIOSH, 2024) [1] CAMEO Chemicals
0.233 mmHg 2.33X10-1 mm Hg at 25 °C [6] Hazardous Substances Data Bank (HSDB)cites Gerhartz, W. (exec ed.). Ullmann's Encyclopedia of Industrial Chemistry. 5th ed.Vol A1: Deerfield Beach, FL: VCH Publishers, 1985 to Present., p. A14: 381 (1989)
0.3 mmHgshown Vapor pressure, kPa at 25 °C: 0.04 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
0.3 mmHg 0.3 mmHg at 77 °F [4] Occupational Safety and Health Administration (OSHA)
0.75 mmHg 0.75 [mm Hg] @35.9 °C [7] PAC Chemical Database, U.S. Department of Energy
1 more value was reported but failed the checks (unreadable or out of range), so it is not shown.

Value	As written	Source
–	Violet-black crystals with a metallic luster and a sharp odor. Mp: 113.5 °C, bp: 185 °C. Emits toxic vapor at room conditions; vapor becomes visibly purple when its concentration builds up in a confined space. Nearly insoluble in water but very soluble in aqueous solutions of iodides.	[1] CAMEO Chemicals
–	Wet Solid; CBI; Large Crystals	[2] EPA Chemical Data Reporting (CDR)
–	BLUISH BLACK OR DARK PURPLE CRYSTALS WITH PUNGENT ODOUR.	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	Violet-black crystals with metallic luster and a sharp, characteristic odor.	[4] Occupational Safety and Health Administration (OSHA)
–	Violet solid with a sharp, characteristic odor.	[5] The National Institute for Occupational Safety and Health (NIOSH)
–	Rhombic, violet-black crystals with metallic luster	[6] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J. Sax's Dangerous Properties of Industrial Materials. 10th ed. Volumes 1-3 New York, NY: John Wiley & Sons Inc., 1999., p. V3: 2095
–shown	Violet solid.	[6] Hazardous Substances Data Bank (HSDB)cites NIOSH. NIOSH Pocket Guide to Chemical Hazards & Other Databases. U.S. Department of Health & Human Services, Public Health Service, Center for Disease Control & Prevention. DHHS (NIOSH) Publication No. 2001-145 (CD-ROM) August 2001.
–	Heavy, grayish-black plates or granules having a metallic luster	[6] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J. Sr.; Hawley's Condensed Chemical Dictionary 14th Edition. John Wiley & Sons, Inc. New York, NY 2001., p. 612

Value	As written	Source
113 °C	236 °F (NIOSH, 2024)	[1] CAMEO Chemicals
114 °C	114 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
113 °C	236 °F	[4] Occupational Safety and Health Administration (OSHA)
113.7 °Cshown	113.7 °C	[7] PAC Chemical Database, U.S. Department of Energy
113 °C	236 °F	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
185 °C	365 °F at 760 mmHg (NIOSH, 2024)	[1] CAMEO Chemicals
184 °C	184 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
185 °C	365 °F	[4] Occupational Safety and Health Administration (OSHA)
184.4 °Cshown	184.4 °C @760 [mm Hg]	[7] PAC Chemical Database, U.S. Department of Energy
185 °C	365 °F	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
–	4.93 (NIOSH, 2024) - Denser than water	[1] CAMEO Chemicals
–	Relative density (water = 1): 4.9	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	4.93	[4] Occupational Safety and Health Administration (OSHA)
–shown	4.933 @25 °C	[7] PAC Chemical Database, U.S. Department of Energy
–	4.93	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
–	0.01 % (NIOSH, 2024)	[1] CAMEO Chemicals
–	For more Solubility (Complete) data for IODINE, ELEMENTAL (9 total), please visit the HSDB record page.	[6] Hazardous Substances Data Bank (HSDB)
–	197 g/kg in carbon disulfide at 25 °C; 19.2 g/kg in carbon tetrachloride at 25 °C; 337.3 g/kg in ether at 25 °C; 164.0 g/kg in benzene at 25 °C; 27.1 g/kg in ethanol at 25 °C; 49.7 g/kg in chloroform at 25 °C; 49.7 g/kg in chloroform at 25 °C; 13.2 g/kg in n-hexane at 25 °C; 97 g/kg in butan-2-ol at 25 °C; 157 g/kg in ethyl acetate at 25 °C; 182.5 g/kg in toluene at 25 °C	[6] Hazardous Substances Data Bank (HSDB)cites Gerhartz, W. (exec ed.). Ullmann's Encyclopedia of Industrial Chemistry. 5th ed.Vol A1: Deerfield Beach, FL: VCH Publishers, 1985 to Present., p. A14: 382 (1989)
–	14.6 g/100 g in bromoethane at 25 °C; 1.73 g/100 g in n-heptane at 25 °C; 9.7 g/100 g in glycerol at 25 °C; 33.7 g/100 g in diethyl ether at 25 °C; 19.7 g/100 g in carbon disulfide at 25 °C	[6] Hazardous Substances Data Bank (HSDB)cites Seiler, H.G., H. Sigel and A. Sigel (eds.). Handbook on the Toxicity of Inorganic Compounds. New York, NY: Marcel Dekker, Inc. 1988., p. 330
–	For more Solubility (Complete) data for IODINE, ELEMENTAL (8 total), please visit the HSDB record page.	[6] Hazardous Substances Data Bank (HSDB)
–shown	Solubility in water, g/100ml at 20 °C: 0.03	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	0.01%	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
–	log Kow = 2.49	[6] Hazardous Substances Data Bank (HSDB)cites Hansch, C., Leo, A., D. Hoekman. Exploring QSAR - Hydrophobic, Electronic, and Steric Constants. Washington, DC: American Chemical Society., 1995., p. 3
–shown	2.49	[3] ILO-WHO International Chemical Safety Cards (ICSCs)

Value	As written	Source
0.3 mmHg	0.3 mmHg at 77 °F (NIOSH, 2024)	[1] CAMEO Chemicals
0.233 mmHg	2.33X10-1 mm Hg at 25 °C	[6] Hazardous Substances Data Bank (HSDB)cites Gerhartz, W. (exec ed.). Ullmann's Encyclopedia of Industrial Chemistry. 5th ed.Vol A1: Deerfield Beach, FL: VCH Publishers, 1985 to Present., p. A14: 381 (1989)
0.3 mmHgshown	Vapor pressure, kPa at 25 °C: 0.04	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
0.3 mmHg	0.3 mmHg at 77 °F	[4] Occupational Safety and Health Administration (OSHA)
0.75 mmHg	0.75 [mm Hg] @35.9 °C	[7] 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: 2
Rings: 0
Aromatic rings: 0
Fraction sp³ carbons (Fsp3): 0
H-bond donors: 0
H-bond acceptors: 0
Rotatable bonds: 0
TPSA (Å²): 0
Formal charge: 0
XLogP3: 1.7 PubChem
Complexity: 0 PubChem
Stereocenters: None
Double-bond geometry: None specified
Point group: D∞h of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

I100.00%

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: 1.77 Crippen (Wildman and Crippen 1999)
log S (water solubility): -2.53 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 4.77 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 253.81
log P ≤ 5 (Crippen): 1.77
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

Warning

Harmonized EU classification (CLP Annex VI). Source [8].

Harmful or irritant
Environmental hazard

H312Harmful in contact with skin
H332Harmful if inhaled
H400Very toxic to aquatic life

Precautionary statements: P261, P271, P273, P280, P302+P352, P304+P340, P317, P321, P362+P364, P391, P501

View all classifications (2)

[8] Regulation (EC) No 1272/2008 of the European Parliament and of the Council · WarningH312, H332, H400
[9] European Chemicals Agency (ECHA) · 837 reports · DangerH302+H312+H332, H302, H312, H315, H319, H332, H335, H372, H400, H410

Exposure limits

PEL-C (Ceiling): 0.1 ppm (1 mg/m³)[4]
PEL: C 0.1 ppm (1 mg/m3)[5]
TLV: 0.01 ppm as TWA; 0.1 ppm as STEL; A4 (not classifiable as a human carcinogen).[3]
TLV-TWA (Time Weighted Average): 0.01 ppm (inhalable fraction and vapor) [2007][4]
TLV-STEL (Short Term Exposure Limit): 0.1 ppm (vapor fraction) [2007][4]
IDLH: 2 ppm (NIOSH, 2024)[1]

First aid

Excerpt from NIOSH Pocket Guide for Iodine: Eye: Irrigate immediately - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately. Skin: SOAP WASH immediately - If this chemical contacts the skin, immediately wash the contaminated skin with soap and water.[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…[10]
(General first aid procedures) Eye: Irrigate immediately - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately. Skin: Soap wash immediately - If this chemical contacts the skin, immediately wash the contaminated skin with soap and water.[5]
Fresh air, rest. Half-upright position. Artificial respiration may be needed. Refer for medical attention.[3]

Storage

Separated from incompatible materials. See Chemical Dangers. Well closed. Ventilation along the floor.[3]
Materials which are toxic as stored or which 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, and should be periodically inspected. Incompatible materials should be isolated ... .[6]

Incompatibilities

The reaction between liquid chlorine and iodine is violent.[6]
Iodine and acetaldehyde interaction may be violent.[6]
Ammonia solutions react with iodine ... To produce highly explosive addition cmpd of nitrogen triiodide and ammonia.[6]
Dipropylmercury and iodine reaction is violent.[6]

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

Spectra

GC-MSNIST Mass Spectrometry Data Center · SpectraBase

Experimental spectra held by these sources; each link opens the source's own record.

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]Occupational Safety and Health Administration (OSHA) · Public domain (US DOL) · via PubChem · retrieved 2026-10-14
[5]The National Institute for Occupational Safety and Health (NIOSH) · Public domain (US CDC) · via PubChem · retrieved 2026-10-14
[6]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
[7]PAC Chemical Database, U.S. Department of Energy · Public domain (US DOE) · via PubChem · retrieved 2026-10-14
[8]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
[9]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[10]Emergency Response Guidebook (ERG) · Public domain (US DOT) · via PubChem · retrieved 2026-10-14
[11]NIST Mass Spectrometry Data Center · Linked only · via PubChem · retrieved 2026-10-14
[12]SpectraBase · Linked only · 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.