Substance profile
Arsenic Trioxide
Arsenic Trioxide is white cubic crystals (Arsenolite) and is odorless.
01 · Identification
What Arsenic Trioxide is
Arsenic Trioxide is white cubic crystals (Arsenolite) and is odorless. It boils at 460 °C, melts at 313 °C, is soluble in water.
Under the GHS it carries the signal word Danger. It is classed as carcinogens.
02 · Identifiers
Arsenic Trioxide identifiers and molecular data
Arsenic Trioxide CAS number and EC number
Arsenic Trioxide molecular formula and molecular weight
Other names for Arsenic Trioxide
- diarsenic trioxide
03 · GHS classification
Arsenic Trioxide hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
Arsenic Trioxide pictograms and signal word
Arsenic Trioxide hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| Acute toxicity - oral GHS chapter 3.1 | Category 1 or 2 | H300 | GHS06 |
| Skin corrosion/irritation GHS chapter 3.2 | Category 1A or 1B or 1C | H314 | GHS05 |
| Carcinogenicity GHS chapter 3.6 | Category 1A or 1B | H350 | GHS08 |
| Hazardous to the aquatic environment - acute GHS chapter 4.1 | Category 1 | H400 | GHS09 |
| Hazardous to the aquatic environment - chronic GHS chapter 4.1 | Category 1 | H410 | 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.
Arsenic Trioxide hazard statements (H-codes)
| Code | Hazard statement |
|---|---|
| H350 | May cause cancer <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>. |
| H300 | Fatal if swallowed. |
| H314 | Causes severe skin burns and eye damage. |
| H400 | Very toxic to aquatic life. |
| H410 | Very toxic to aquatic life with long lasting effects. |
This page lists only the codes assigned to Arsenic Trioxide. 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 Arsenic Trioxide
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 Arsenic Trioxide 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
Arsenic Trioxide precautionary statements
CLP Annex VI assigns 13 precautionary statements to Arsenic Trioxide. 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
Arsenic Trioxide 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 | диарсенов триоксид арсенов триоксид |
| Spanish español | Trióxido de diarsénico trióxido de arsénico |
| Czech čeština | oxid arsenitý |
| Danish dansk | diarsentrioxid arsentrioxid |
| German Deutsch | Diarsentrioxid Arsentrioxid |
| Estonian eesti | diarseentrioksiid arseentrioksiid |
| Greek ελληνικά | τριοξείδιο του διαρσενικού τριοξείδιο του αρσενικού |
| English English | diarsenic trioxide arsenic trioxide |
| French français | trioxyde de diarsenic trioxyde d'arsenic |
| Croatian hrvatski | diarsenov trioksid arsenov trioksid |
| Italian italiano | diarsenico triossido arsenico triossido |
| Latvian latviešu | diarsēna trioksīds arsēna trioksīds |
| Lithuanian lietuvių | diarseno trioksidas arseno trioksidas |
| Hungarian magyar | diarzén-trioxid arzén-trioxid |
| Maltese Malti | triossidu tad-diarseniku triossidu tal-arseniku |
| Dutch Nederlands | diarseentrioxide arseentrioxide |
| Polish polski | tlenek arsenu(III) tritlenek arsenuarszeniktlenek arsenawy |
| Portuguese português | trióxido de diarsénio trióxido de arsénio |
| Romanian română | trioxid de diarsen trioxid de arsen |
| Slovak slovenčina | oxid arzenitý |
| Slovenian slovenščina | diarzenov trioksid arzenov trioksid |
| Finnish suomi | diarseenitrioksidi arseenitrioksidi |
| Swedish svenska | diarseniktrioxid arseniktrioxid |
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
Arsenic Trioxide GHS label elements
Everything CLP Annex VI fixes for Arsenic Trioxide, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Danger
Arsenic Trioxide
- May cause cancer <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>.
- Fatal if swallowed.
- Causes severe skin burns and eye damage.
- Very toxic to aquatic life.
- Very toxic to aquatic life with long lasting effects.
- Obtain special instructions before use.
- Do not breathe dust/fume/gas/mist/vapours/spray.
- Do not eat, drink or smoke when using this product.
- Avoid release to the environment.
- Wear protective gloves/protective clothing/eye protection/face protection/hearing protection/…
- IF SWALLOWED:
- IF exposed or concerned:
- Immediately call a POISON CENTER/doctor/…
- Get medical advice/attention.
- Rinse mouth.
- Do NOT induce vomiting.
- Collect spillage.
- Dispose of contents/container to …
Supplier name, address and telephone number· Product identifier·Nominal quantity
Need this as an actual label? Open Arsenic Trioxide in the GHS label constructor →
07 · Health hazards
Arsenic Trioxide health hazards and exposure limits
Arsenic Trioxide hazard summary
A corrosive substance that can cause injury to the skin, eyes, and respiratory tract; Can cause arsenic poisoning; [ICSC] Extremely toxic with an oral lethal dose of less than 5 mg/kg, or just a taste (less than 7 drops) for a 150-lb. person; [CAMEO] A corrosive substance that can cause injury to the skin, eyes, and respiratory tract; Inhalation may cause chemical pneumonitis and pulmonary edema; May cause respiratory sensitization after prolonged contact; Effects in high-dose animal studies include acute pulmonary edema, cardiac arrhythmias, abnormal liver function tests, fatty liver degeneration, and depressed renal function tests; [MSDSonline] See Arsenic and the linked occupational diseases.
Source: Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
Arsenic Trioxide carcinogenicity classification
Classification of carcinogenicity: 1) evidence in humans: sufficient; 2) evidence in animals: limited. Overall summary evaluation of carcinogenic risk to humans is Group 1: Carcinogenic to humans. NOTE: This evaluation applies to the group of chemicals as a whole and not necessarily to all individual chemicals within the group. /Arsenic and arsenic compounds/
Source: Hazardous Substances Data Bank (HSDB)
Evaluation: There is sufficient evidence in humans that arsenic in drinking-water causes cancers of the urinary bladder, lung and skin ... Overall evaluation: Arsenic in drinking-water is carcinogenic to humans (Group 1). /Arsenic in drinking water/
Source: Hazardous Substances Data Bank (HSDB)
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.
Arsenic Trioxide occupational exposure limits
| Limit | Value | Source |
|---|---|---|
| PEL | 0.01 [mg/m3], as As | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| IDLH | 5 mg As/m3 ; A potential occupational carcinogen. (NIOSH, 2024) | CAMEO Chemicals |
| IDLH | 5.0 [mg/m3], as As | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| IDLH | 5 mg/cu m (as AS); NIOSH considers arsenic (inorganic cmpd, as As) to be a potential occupational carcinogen. /Arsenic (inorganic cmpd, as As)/ | 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
Arsenic Trioxide 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.
Arsenic Trioxide boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | 460 °C (860 °F) | HSDB | |
| 465 °C (869 °F) | at 760 mmHg | CAMEO |
Arsenic Trioxide melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | 313 °C (595.4 °F) | claudetite | HSDB |
| 274 °C (525.2 °F) | DOE PAC | ||
| 252.53 °C (486.6 °F) | range, midpoint shown | CAMEO |
Arsenic Trioxide density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 3.865 g/cm³ | cubes | HSDB |
| 3.738 g/cm³ | CAMEO | ||
| 3.86 g/cm³ | at 25 °C | DOE PAC |
Arsenic Trioxide solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | SOL IN DIL HYDROCHLORIC ACID, IN ALKALI HYDROXIDE; SOL IN CARBONATE SOLN; PRACTICALLY INSOL IN ALC; PRACTICALLY INSOL IN CHLOROFORM, ETHER. | HSDB | |
| Soluble in glycerol | HSDB | ||
| Solubility in water, g/100ml at 20 °C: 1.2-3.7 | at 20 °C | ICSC |
Arsenic Trioxide vapor pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor pressure | 0.000247 mmHg | at 25 °C | HSDB |
| 66.1 mmHg | at 312 °C | CAMEO | |
| 0.000247 mmHg | Haz-Map |
Arsenic Trioxide lower explosive limit (LEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Lower explosive limit (LEL) | Not flammable | HSDB | |
| Not flammable. (EPA, 1998) | CAMEO |
Arsenic Trioxide upper explosive limit (UEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Upper explosive limit (UEL) | Not flammable. (EPA, 1998) | CAMEO |
Arsenic Trioxide critical temperature and pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Critical temperature and pressure | 927 °C (1700.6 °F) | HSDB |
Arsenic Trioxide corrosivity
| Property | Value | Conditions | Source |
|---|---|---|---|
| Corrosivity | Corrosive to metals in the presence of moisture. | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Handling and storage
Arsenic Trioxide storage and handling
Arsenic Trioxide safe storage
Provision to contain effluent from fire extinguishing. Separated from combustible substances, reducing agents and food and feedstuffs. Well closed. Store only in original container. Store in an area without drain or sewer access.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
Arsenic Trioxide storage conditions
Store in a cool, dry, well-ventilated location. Separate from acids, halogens, and iron salts.
Source: Hazardous Substances Data Bank (HSDB)
Arsenic Trioxide incompatible materials
A mixture of arsenic trioxide with excess zinc filings will explode on heating.
Source: Hazardous Substances Data Bank (HSDB)
Arsenic Trioxide reactivity
ARSENIC TRIOXIDE reacts vigorously with fluorine at ordinary temperatures [Mellor 9:34 1946-47]. Dissolves in aqueous acids. Incompatible with tannic acid, infusions of cinchona and other vegetable astringent infusions and decoctions, and with iron in solution [Merck].
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check Arsenic Trioxide in the storage compatibility matrix →
10 · Transport
Arsenic Trioxide 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.
Arsenic Trioxide under UN 1561 — shipping name, class and packing group
Europe · ADR 2025, Table A
| Proper shipping name (3.1.2) | Class | Classification code | PG | Labels (column 5) |
|---|---|---|---|---|
| ARSENIC TRIOXIDE | 6.1 | T5 | II | |
Source: ADR 2025, Table A of Chapter 3.2 · ECE/TRANS/352 Vol. I (UNECE). Class 6.1 is “Toxic substances” (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) |
|---|---|---|---|
| Arsenic trioxide | 6.1 | II | |
Source: 49 CFR 172.101 Hazardous Materials Table · eCFR, revision 2026-08-03. Class 6.1 is “Poisonous materials” (49 CFR 173.2).
11 · Questions
Arsenic Trioxide — frequently asked questions
What is the CAS number of Arsenic Trioxide?
The CAS number of Arsenic Trioxide is 1327-53-3. Its EC number is 215-481-4.
What does a Arsenic Trioxide label have to show?
Under CLP Annex VI the label for Arsenic Trioxide carries the pictograms Skull and crossbones, Health hazard, Corrosion and Environment and the signal word is Danger.
Is Arsenic Trioxide flammable?
CLP Annex VI assigns Arsenic Trioxide 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 Arsenic Trioxide a carcinogen?
Yes. CLP Annex VI classifies Arsenic Trioxide as a category 1A or 1B carcinogen and assigns it H350: may cause cancer.
What is the exposure limit for Arsenic Trioxide?
The US occupational exposure limit reported for Arsenic Trioxide is 0.01 [mg/m3], as As (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 Arsenic Trioxide?
The boiling point reported for Arsenic Trioxide is 460 °C (860 °F) (HSDB).
What is the melting point of Arsenic Trioxide?
The melting point reported for Arsenic Trioxide is 313 °C (595.4 °F), claudetite (HSDB).
How should Arsenic Trioxide be stored?
Store in a cool, dry, well-ventilated location. Separate from acids, halogens, and iron salts. (Hazardous Substances Data Bank (HSDB))
Nearby
Substances next to Arsenic Trioxide
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