Substance profile
Molybdenum trioxide
Molybdenum trioxide is white or slightly yellow to slightly bluish powder or granules with a none odor.
01 · Identification
What Molybdenum trioxide is
Molybdenum trioxide is white or slightly yellow to slightly bluish powder or granules with a none odor. Its molecular formula is MoO3 and its molecular weight is 143.95 g/mol. It boils at 1155 °C, melts at 795 °C.
Under the GHS it carries the signal word Warning.
02 · Identifiers
Molybdenum trioxide identifiers and molecular data
Molybdenum trioxide CAS number and EC number
Molybdenum trioxide molecular formula and molecular weight
03 · GHS classification
Molybdenum trioxide hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
Molybdenum trioxide pictograms and signal word
Molybdenum trioxide hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| Serious eye damage/eye irritation GHS chapter 3.3 | Category 2A | H319 | GHS07 |
| Carcinogenicity GHS chapter 3.6 | Category 2 | H351 | GHS08 |
| Specific target organ toxicity - single exposure GHS chapter 3.8 | Category 3 | H335 | GHS07 |
Molybdenum trioxide 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>. |
| H335 | May cause respiratory irritation. |
| H319 | Causes serious eye irritation. |
This page lists only the codes assigned to Molybdenum 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 Molybdenum 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 Molybdenum 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
Molybdenum trioxide precautionary statements
CLP Annex VI assigns 8 precautionary statements to Molybdenum 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.
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
Molybdenum 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 | молибденов триоксид |
| Spanish español | Trióxido de molibdeno |
| Czech čeština | oxid molybdenový |
| Danish dansk | molybdentrioxid |
| German Deutsch | Molybdäntrioxid |
| Estonian eesti | molübdeentrioksiid |
| Greek ελληνικά | τριοξείδιο του μολυβδαινίου |
| English English | molybdenum trioxide |
| French français | trioxyde de molybdène |
| Croatian hrvatski | molibdenov trioksid |
| Italian italiano | triossido di molibdeno |
| Latvian latviešu | molibdēna trioksīds |
| Lithuanian lietuvių | molibdeno trioksidas |
| Hungarian magyar | molibdén-trioxid |
| Maltese Malti | triossidu tal-molibdenu |
| Dutch Nederlands | molybdeentrioxide |
| Polish polski | tritlenek molibdenu tlenek molibdenu(VI) |
| Portuguese português | trióxido de molibdénio |
| Romanian română | trioxid de molibden |
| Slovak slovenčina | oxid molybdénový |
| Slovenian slovenščina | molibdenov trioksid |
| Finnish suomi | molybdeenitrioksidi |
| Swedish svenska | molybdentrioxid |
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
Molybdenum trioxide GHS label elements
Everything CLP Annex VI fixes for Molybdenum trioxide, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Warning
Molybdenum trioxide
- Suspected of causing cancer <state route of exposure if it is conclusively proven that no other routes of exposure cause the hazard>.
- May cause respiratory irritation.
- Causes serious eye irritation.
- Obtain special instructions before use.
- Wash … thoroughly after handling.
- Wear protective gloves/protective clothing/eye protection/face protection/hearing protection/…
- IF IN EYES:
- IF exposed or concerned:
- Get medical advice/attention.
- If eye irritation persists:
- Remove contact lenses, if present and easy to do. Continue rinsing.
Supplier name, address and telephone number· Product identifier·Nominal quantity
Need this as an actual label? Open Molybdenum trioxide in the GHS label constructor →
07 · Health hazards
Molybdenum trioxide health hazards and exposure limits
Molybdenum trioxide hazard summary
An eye, mucous membrane, and upper respiratory tract irritant; [HSDB] Serious health risk by ingestion or prolonged inhalation; [eChemPortal: ESIS] Carcinogenicity in man cannot be assessed conclusively because of insufficient data (Group 3B); [MAK] An irritant; [MSDSonline] See Molybdenum.
Source: Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
Molybdenum trioxide carcinogenicity classification
Under the conditions of these 2-year inhalation studies, there was equivocal evidence of carcinogenic activity of molybdenum trioxide in male F344/N rats based on a marginally significant positive trend of alveolar/bronchiolar adenoma or carcinoma (combined). There was no evidence of carcinogenic activity of molybdenum trioxide in female F344/N rats exposed to 10, 30, or 100 mg/m3. There was some evidence of carcinogenic activity of molybdenum trioxide in male B6C3F1 mice based on increased incidences of alveolar/bronchiolar carcinoma and adenoma or carcinoma (combined). There was some evidence of carcinogenic activity of molybdenum trioxide in female B6C3F1 mice based on increased incidences of alveolar/bronchiolar adenoma and adenoma or carcinoma (combined).
Source: US National Toxicology Program · TR-462: Toxicology and Carcinogenesis Studies of Molybdenum Trioxide (CASRN 1313-27-5) in F344 Rats and B6C3F1 Mice (Inhalation Studies) (1997 )
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.
Molybdenum trioxide occupational exposure limits
| Limit | Value | Source |
|---|---|---|
| PEL | 5.0 [mg/m3], as Mo | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| IDLH | 1000 mg Mo/m3 (NIOSH, 2024) | CAMEO Chemicals |
| IDLH | 1000.0 [mg/m3], as Mo | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
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
Molybdenum 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.
Molybdenum trioxide boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | 1155 °C (2111 °F) | at 760 mmHg | DOE PAC |
| 1155 °C (2111 °F) | sublimes | HSDB | |
| 1155 °C (2111 °F) | sublimes, at 760 mmHg | CAMEO |
Molybdenum trioxide melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | 795 °C (1463 °F) | HSDB | |
| 802 °C (1475.6 °F) | DOE PAC |
Molybdenum trioxide density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 4.69 g/cm³ | at 20 °C | CAMEO |
| 4.696 g/cm³ | at 25 °C | DOE PAC | |
| 4.69 g/cm³ | at 26 °C | HSDB |
Molybdenum trioxide solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | After strong ignition it is very slightly sol in acids | HSDB | |
| Sol in concentrated mineral acids | HSDB | ||
| Sol in soln of alkali hydroxides and soln of potassium bitartrate | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Handling and storage
Molybdenum trioxide storage and handling
Molybdenum trioxide incompatible materials
/Incompatible with/ alkali metals; sodium, potassium, molten magnesium. /Molybdenum, sol compounds, (as Mo)/
Source: Hazardous Substances Data Bank (HSDB)
Molybdenum trioxide reactivity
MOLYBDENUM TRIOXIDE reacts violently with chlorine trifluoride, lithium, potassium and sodium. Readily combines with acids and bases to form a series of polymeric compounds. Incompatible with interhalogens and metals. A violent detonation occurs when heated with molten magnesium. (NTP, 1992)
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check Molybdenum trioxide in the storage compatibility matrix →
10 · Questions
Molybdenum trioxide — frequently asked questions
What is the CAS number of Molybdenum trioxide?
The CAS number of Molybdenum trioxide is 1313-27-5. Its EC number is 215-204-7.
What is the chemical formula of Molybdenum trioxide?
The molecular formula of Molybdenum trioxide is MoO3 and its molecular weight is 143.95 g/mol.
What does a Molybdenum trioxide label have to show?
Under CLP Annex VI the label for Molybdenum trioxide carries the pictograms Health hazard and Exclamation mark and the signal word is Warning.
Is Molybdenum trioxide flammable?
CLP Annex VI assigns Molybdenum 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 Molybdenum trioxide a carcinogen?
CLP Annex VI assigns Molybdenum trioxide H351 — suspected of causing cancer. That is category 2: the evidence points that way but is not conclusive. IARC places it in Group 2B: possibly carcinogenic to humans.
What is the exposure limit for Molybdenum trioxide?
The US occupational exposure limit reported for Molybdenum trioxide is 5.0 [mg/m3], as Mo (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 Molybdenum trioxide?
The boiling point reported for Molybdenum trioxide is 1155 °C (2111 °F), at 760 mmHg (DOE PAC).
What is the melting point of Molybdenum trioxide?
The melting point reported for Molybdenum trioxide is 795 °C (1463 °F) (HSDB).
Nearby
Substances next to Molybdenum trioxide
Keep going: substances starting with M, or search the whole database by name, CAS number, pictogram or signal word.