Substance profile
1,4-dihydroxybenzene
1,4-dihydroxybenzene is white crystals and is odorless.
01 · Identification
What 1,4-dihydroxybenzene is
1,4-dihydroxybenzene is white crystals and is odorless. Its molecular formula is C6H6O2 and its molecular weight is 110.11 g/mol. It boils at 285 °C, melts at 173 °C.
Under the GHS it carries the signal word Danger. It is classed as hazardous Air Pollutants (HAPs).
02 · Identifiers
1,4-dihydroxybenzene identifiers and molecular data
1,4-dihydroxybenzene CAS number and EC number
1,4-dihydroxybenzene molecular formula and molecular weight
Other names for 1,4-dihydroxybenzene
- hydroquinone
- quinol
03 · GHS classification
1,4-dihydroxybenzene hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
1,4-dihydroxybenzene pictograms and signal word
1,4-dihydroxybenzene hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| Acute toxicity - oral GHS chapter 3.1 | Category 4 | H302 | GHS07 |
| Serious eye damage/eye irritation GHS chapter 3.3 | Category 1 | H318 | GHS05 |
| Skin sensitisation GHS chapter 3.4 | Category 1 or 1A or 1B | H317 | GHS07 |
| Germ cell mutagenicity GHS chapter 3.5 | Category 2 | H341 | GHS08 |
| Carcinogenicity GHS chapter 3.6 | Category 2 | H351 | GHS08 |
| Hazardous to the aquatic environment - acute GHS chapter 4.1 | Category 1 | H400 | GHS09 |
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.
1,4-dihydroxybenzene hazard statements (H-codes)
| Code | Hazard statement |
|---|---|
| H351 | Suspected of causing cancer <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>. |
| H341 | Suspected of causing genetic defects <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>. |
| H302 | Harmful if swallowed. |
| H318 | Causes serious eye damage. |
| H317 | May cause an allergic skin reaction. |
| H400 | Very toxic to aquatic life. |
This page lists only the codes assigned to 1,4-dihydroxybenzene. 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 1,4-dihydroxybenzene
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 1,4-dihydroxybenzene 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
1,4-dihydroxybenzene precautionary statements
CLP Annex VI assigns 17 precautionary statements to 1,4-dihydroxybenzene. 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.
Disposal
What has to happen to the contents and the empty container.
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
1,4-dihydroxybenzene 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 | 1,4-дихидроксибензен хидрохинонхинол |
| Spanish español | 1,4-Dihidroxibenceno hidroquinonaquinol |
| Czech čeština | 1,4-benzodiol hydrochinonchinol |
| Danish dansk | 1,4-dihydroxybenzen hydroquinonquinol |
| German Deutsch | 1,4-Dihydroxybenzol HydrochinonChinol |
| Estonian eesti | 1,4-dihüdroksübenseen hüdrokinoonkinool |
| Greek ελληνικά | 1,4-διυδροξυβενζόλιο υδροκινόνηκινόλη |
| English English | 1,4-dihydroxybenzene hydroquinonequinol |
| French français | 1,4-dihydroxybenzène hydroquinonequinol |
| Croatian hrvatski | 1,4-dihidroksibenzen hidrokinonkinol |
| Italian italiano | 1,4-diidrossibenzene idrochinonechinolo |
| Latvian latviešu | 1,4-dihidroksibenzols hidrohinonshinols |
| Lithuanian lietuvių | 1,4-dihidroksibenzenas hidrochinonaschinolis |
| Hungarian magyar | 1,4-dihidroxibenzol hidrokinonkinol |
| Maltese Malti | 1,4-diidrossibenżen idrokinonkinol |
| Dutch Nederlands | 1,4-dihydroxybenzeen hydrochinonchinol |
| Polish polski | 1,4-dihydroksybenzen hydrochinonchinol |
| Portuguese português | 1,4-di-hidroxibenzeno hidroquinonaquinol |
| Romanian română | 1,4-dihidroxi benzen hidrochinonăchinol |
| Slovak slovenčina | benzén-1,4-diol hydrochinónchinol |
| Slovenian slovenščina | 1,4-dihidroksibenzen hidrokinonkinol |
| Finnish suomi | 1,4-dihydroksibentseeni hydrokinonikinoli |
| Swedish svenska | 1,4-dihydroxibensen hydrokinonkinol |
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
1,4-dihydroxybenzene GHS label elements
Everything CLP Annex VI fixes for 1,4-dihydroxybenzene, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Danger
1,4-dihydroxybenzene
- Suspected of causing cancer <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>.
- Suspected of causing genetic defects <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>.
- Harmful if swallowed.
- Causes serious eye damage.
- May cause an allergic skin reaction.
- Very toxic to aquatic life.
- Obtain special instructions before use.
- Avoid breathing dust/fume/gas/mist/vapours/spray.
- Do not eat, drink or smoke when using this product.
- Contaminated work clothing should not be allowed out of the workplace.
- Avoid release to the environment.
- Wear protective gloves/protective clothing/eye protection/face protection/hearing protection/…
- IF SWALLOWED:
- IF IN EYES:
- IF exposed or concerned:
- Immediately call a POISON CENTER/doctor/…
- Call a POISON CENTER/doctor/… if you feel unwell.
- Get medical advice/attention.
- Rinse mouth.
- If skin irritation or rash occurs:
- Remove contact lenses, if present and easy to do. Continue rinsing.
- Collect spillage.
- Dispose of contents/container to …
Supplier name, address and telephone number· Product identifier·Nominal quantity
Need this as an actual label? Open 1,4-dihydroxybenzene in the GHS label constructor →
07 · Health hazards
1,4-dihydroxybenzene health hazards and exposure limits
1,4-dihydroxybenzene hazard summary
Hydroquinone is used as a developing agent in photography and as an antioxidant in rubber and food. Tinnitus (ringing in the ears), dizziness, headache, nausea, vomiting, dyspnea, erosion of the gastric mucosa, edema of internal organs, cyanosis, convulsions, delirium, and collapse may result from the ingestion of a large amount of hydroquinone in humans. Hydroquinone is also a skin irritant in humans. Chronic (long-term) occupational exposure to hydroquinone dust can result in eye irritation, corneal effects, and impaired vision. No information is available on the reproductive, developmental, or carcinogenic effects of hydroquinone in humans. There was some evidence of carcinogenic activity in orally-exposed rodents. Increased skin tumor incidence has been reported in mice treated dermally. EPA has not classified hydroquinone for carcinogenicity.
Source: EPA Hazardous Air Pollutants
1,4-dihydroxybenzene carcinogenicity classification
Under the conditions of these 2-year gavage studies, there was some evidence of carcinogenic activity of hydroquinone for male F344/N rats, as shown by marked increases in tubular cell adenomas of the kidney. There was some evidence of carcinogenic activity of hydroquinone for female F344/N rats, as shown by increases in mononuclear cell leukemia. There was no evidence of carcinogenic activity of hydroquinone for male B6C3F1 mice administered 50 or 100 mg/kg in water by gavage. There was some evidence of carcinogenic activity of hydroquinone for female B6C3F1 mice, as shown by increases in hepatocellular neoplasms, mainly adenomas.
Source: US National Toxicology Program · TR-366: Toxicology and Carcinogenesis Studies of Hydroquinone (CASRN 123-31-9) in F344/N Rats and B6C3F1 Mice (Gavage Studies) (1989 )
Evaluation: There is inadequate evidence in humans for the carcinogenicity of hydroquinone. There is limited evidence in experimental animals for the carcinogenicity of hydroquinone. Overall evaluation: Hydroquinone is not classifiable as to its carcinogenicity to humans (Group 3).
Source: Hazardous Substances Data Bank (HSDB)
The authors of this detailed review cover hydroquinone's potential for carcinogenicity and its possible mode of carcinogenic action. They proposed and evaluated a nongenotoxic mode of action that involves the exacerbation of chronic progressive nephropathy (CPN), a spontaneously occurring rodent renal disease. Their conclusion is that the increased incidence of renal tubule adenomas in hydroquinone-dosed male rats is without human consequence.
Source: Pertti (Bert) Hakkinen's Toxicology and Other Annotations
An IARC group and a CLP classification answer different questions. IARC judges whether the evidence for cancer in humans is strong enough; CLP Annex VI is the legally binding EU classification. A substance can carry one and not the other.
1,4-dihydroxybenzene occupational exposure limits
| Limit | Value | Source |
|---|---|---|
| PEL | 2.0 [mg/m3] | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| PEL | 2 mg/m³ | Occupational Safety and Health Administration (OSHA) |
| PEL | TWA 2 mg/m3 | The National Institute for Occupational Safety and Health (NIOSH) |
| REL | 2 mg/m³ [15 minutes] | Occupational Safety and Health Administration (OSHA) |
| REL | C 2 mg/m3 [15-minute] | The National Institute for Occupational Safety and Health (NIOSH) |
| IDLH | 50 mg/m3 (NIOSH, 2024) | CAMEO Chemicals |
| IDLH | 50.0 [mg/m3] | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| IDLH | 50 mg/cu m. | Hazardous Substances Data Bank (HSDB) |
These are United States values. The European Union sets its own indicative and binding limits, and the figure that applies at a given workplace is the one in the local regulation — not the one shown here.
08 · Physical and chemical properties
1,4-dihydroxybenzene 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.
1,4-dihydroxybenzene boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | 285 °C (545 °F) | NIOSH | |
| 287 °C (548.6 °F) | ICSC |
1,4-dihydroxybenzene melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | 173 °C (343.4 °F) | HSDB | |
| 170 °C (338 °F) | NIOSH | ||
| 172 °C (341.6 °F) | ICSC |
1,4-dihydroxybenzene density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 1.33 g/cm³ | NIOSH | |
| 1.3 g/cm³ | ICSC | ||
| 1.33 g/cm³ | at 20 °C | HSDB |
1,4-dihydroxybenzene solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | In water, 72,000 mg/L at 25 °C | at 25 °C | HSDB |
| 7% soluble in water at 25 °C | at 25 °C | HSDB |
1,4-dihydroxybenzene vapor pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor pressure | 0.00001 mmHg | NIOSH | |
| 0.0009001 mmHg | at 20 °C | ICSC | |
| 0.000019 mmHg | at 25 °C | HSDB |
1,4-dihydroxybenzene flash point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Flash point | 165 °C (329 °F) | HSDB | |
| 165 °C (329 °F) | Closed cup | HSDB |
1,4-dihydroxybenzene autoignition temperature
| Property | Value | Conditions | Source |
|---|---|---|---|
| Autoignition temperature | 515.56 °C (960 °F) | HSDB | |
| 515 °C (959 °F) | ICSC |
1,4-dihydroxybenzene lower explosive limit (LEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Lower explosive limit (LEL) | Dust cloud may explode if ignited in an enclosed area. | HSDB | |
| Combustible Solid; dust cloud may explode if ignited in an enclosed area. | NIOSH | ||
| Potentially explosive reaction with oxygen at 90 °C/ 100 bar...Slight explosion hazard when exposed to heat. | at 90 °C, at 75006.2 mmHg | HSDB |
1,4-dihydroxybenzene vapor density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor density | 3.81 (air = 1) | HSDB | |
| 3.8 (air = 1) | ICSC |
1,4-dihydroxybenzene critical temperature and pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Critical temperature and pressure | 549 °C (1020.2 °F) | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Fire and explosion
1,4-dihydroxybenzene 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.
1,4-dihydroxybenzene fire potential
Fire hazard: slight, when exposed to heat or flame; can react with oxidizing materials.
Source: Hazardous Substances Data Bank (HSDB)
Solubility
In water, 6.72 g/L at 20 °C. Also water solubility = 3.85 g/L at 0 °C; 5.12 g/L at 10 °C; 5.40 g/L at 15 °C; 8.76 g/L at 30 °C; 11.5 g/L at 40 °C; 25/9 g/L at 60 °C; 46.8 g/L at 80 °C; 66.4 g/L at 100 °C
Source: HSDB
10 · Handling and storage
1,4-dihydroxybenzene storage and handling
1,4-dihydroxybenzene safe storage
Separated from strong bases and food and feedstuffs.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
1,4-dihydroxybenzene storage conditions
Keep well closed and protected from light.
Source: Hazardous Substances Data Bank (HSDB)
1,4-dihydroxybenzene incompatible materials
Strong oxidizers, alkalis.
Source: Hazardous Substances Data Bank (HSDB)
1,4-dihydroxybenzene reactivity
HYDROQUINONE is a slight explosion hazard when exposed to heat. Incompatible with strong oxidizing agents. Also incompatible with bases. It reacts with oxygen and sodium hydroxide. Reacts with ferric salts (NTP, 1992). Hot and/or concentrated NaOH can cause hydroquinone to decompose exothermically at elevated temperature. (NFPA Pub. 491M, 1975, 385)
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check 1,4-dihydroxybenzene in the storage compatibility matrix →
11 · Questions
1,4-dihydroxybenzene — frequently asked questions
What is the CAS number of 1,4-dihydroxybenzene?
The CAS number of 1,4-dihydroxybenzene is 123-31-9. Its EC number is 204-617-8.
What is the chemical formula of 1,4-dihydroxybenzene?
The molecular formula of 1,4-dihydroxybenzene is C6H6O2 and its molecular weight is 110.11 g/mol.
What does a 1,4-dihydroxybenzene label have to show?
Under CLP Annex VI the label for 1,4-dihydroxybenzene carries the pictograms Corrosion, Health hazard, Exclamation mark and Environment and the signal word is Danger.
Is 1,4-dihydroxybenzene flammable?
CLP Annex VI assigns 1,4-dihydroxybenzene 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. The flash point reported for it is 165 °C (329 °F) (HSDB).
Is 1,4-dihydroxybenzene a carcinogen?
CLP Annex VI assigns 1,4-dihydroxybenzene H351 — suspected of causing cancer. That is category 2: the evidence points that way but is not conclusive. IARC places it in Group 3: not classifiable as to its carcinogenicity to humans.
What is the exposure limit for 1,4-dihydroxybenzene?
The US occupational exposure limit reported for 1,4-dihydroxybenzene is 2.0 [mg/m3] (Haz-Map, Information on Hazardous Chemicals and Occupational Diseases). Limits differ by country: the EU sets its own indicative and binding values, and the figure that applies at a given workplace is the one in the local regulation.
What is the boiling point of 1,4-dihydroxybenzene?
The boiling point reported for 1,4-dihydroxybenzene is 285 °C (545 °F) (NIOSH).
What is the melting point of 1,4-dihydroxybenzene?
The melting point reported for 1,4-dihydroxybenzene is 173 °C (343.4 °F) (HSDB).
How should 1,4-dihydroxybenzene be stored?
Keep well closed and protected from light. (Hazardous Substances Data Bank (HSDB))
Nearby
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