Substance profile
Potassium
Potassium is a soft, silvery-white metal; body centered cubic structure.
01 · Identification
What Potassium is
Potassium is a soft, silvery-white metal; body centered cubic structure. Its molecular formula is K and its molecular weight is 39.098 g/mol. It boils at 759 °C, melts at 63.5 °C.
Under the GHS it carries the signal word Danger. It is classed as flammable agents - 3rd degree.
02 · Identifiers
Potassium identifiers and molecular data
Potassium CAS number and EC number
Potassium molecular formula and molecular weight
03 · GHS classification
Potassium hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
Potassium pictograms and signal word
Potassium hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| In contact with water emits flammable gases GHS chapter 2.12 | Category 1 | H260 | GHS02 |
| Skin corrosion/irritation GHS chapter 3.2 | Category 1A or 1B or 1C | H314 | GHS05 |
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.
Potassium hazard statements (H-codes)
| Code | Hazard statement |
|---|---|
| H260 | In contact with water releases flammable gases which may ignite spontaneously. |
| H314 | Causes severe skin burns and eye damage. |
Potassium supplemental EU statements (EUH)
| Code | Statement |
|---|---|
| EUH014 | Reacts violently with water. |
This page lists only the codes assigned to Potassium. 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 Potassium
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 Potassium 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
Potassium precautionary statements
CLP Annex VI assigns 5 precautionary statements to Potassium. 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
Potassium 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 | калий |
| Spanish español | Potasio |
| Czech čeština | draslík |
| Danish dansk | kalium |
| German Deutsch | Kalium |
| Estonian eesti | kaalium |
| Greek ελληνικά | κάλιο |
| English English | potassium |
| French français | potassium |
| Croatian hrvatski | kalij |
| Italian italiano | This edition prints another entry’s name here. The Italian edition prints "diossido di cloro", the name of entry 017-026-01-0, for this entry. The EC and CAS numbers in the same row, 231-119-8 and 7440-09-7, are potassium and are correct. Regulation (EU) 2018/669, OJ L 115, 4.5.2018, p. 88 diossido di cloro . . .% |
| Latvian latviešu | kālijs |
| Lithuanian lietuvių | kalis |
| Hungarian magyar | kálium |
| Maltese Malti | potassju |
| Dutch Nederlands | kalium |
| Polish polski | potas |
| Portuguese português | potássio |
| Romanian română | potasiu |
| Slovak slovenčina | draslík |
| Slovenian slovenščina | kalij |
| Finnish suomi | kalium |
| Swedish svenska | kalium |
One or more lines above are flagged. In those language editions the Regulation as published in the Official Journal prints something that the rest of the same row contradicts — a name belonging to a different entry, or the qualifier of a paired entry. Each flag cites the amending act and the Official Journal page, so the wording can be checked at source. The lines are reproduced as printed, because Art. 18(2) points at Annex VI and not at our reading of it; the note beside each one says what the row’s own EC and CAS numbers identify.
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
Potassium GHS label elements
Everything CLP Annex VI fixes for Potassium, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Danger
Potassium
- In contact with water releases flammable gases which may ignite spontaneously.
- Causes severe skin burns and eye damage.
- Reacts violently with water.
- Do not breathe dust/fume/gas/mist/vapours/spray.
- Wear protective gloves/protective clothing/eye protection/face protection/hearing protection/…
- IF SWALLOWED:
- Immediately call a POISON CENTER/doctor/…
- Do NOT induce vomiting.
Supplier name, address and telephone number· Product identifier·Nominal quantity
Need this as an actual label? Open Potassium in the GHS label constructor →
07 · Health hazards
Potassium health hazards and exposure limits
Potassium hazard summary
Skin contact can cause severe burns. [CHRIS]
Source: Haz-Map, Information on Hazardous Chemicals and Occupational Diseases
08 · Physical and chemical properties
Potassium 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.
Potassium boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | 759 °C (1398.2 °F) | HSDB | |
| 773.89 °C (1425 °F) | at 760 mmHg | CAMEO | |
| 765.5 °C (1409.9 °F) | ICSC |
Potassium melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | 63.5 °C (146.3 °F) | HSDB | |
| 62.78 °C (145 °F) | CAMEO | ||
| 63.2 °C (145.8 °F) | ICSC |
Potassium density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 0.856 g/cm³ | ICSC | |
| 0.862 g/cm³ | at 20 °C | HSDB | |
| 0.86 g/cm³ | at 20 °C | CAMEO |
Potassium solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | Soluble in liquid ammonia, ethylenediamine, aniline; soluble in several metals; forms liquid alloys with other alkali metals | HSDB | |
| SOL IN ACID, MERCURY | HSDB | ||
| Solubility in water: reaction | ICSC |
Potassium vapor pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor pressure | 8 mmHg | at 432 °C | HSDB |
| Vapor pressure at 20 °C: negligible | at 20 °C | ICSC |
Potassium flash point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Flash point | Not Applicable. Combustible solid. (USCG, 1999) | CAMEO |
Potassium vapor density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor density | 1.4 (air = 1) | HSDB |
Potassium corrosivity
| Property | Value | Conditions | Source |
|---|---|---|---|
| Corrosivity | Direct contact with metal may be corrosive and cause skin and eye burns | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Fire and explosion
Potassium 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.
Potassium fire potential
Extremely dangerous in contact with moisture or water, releasing hydrogen with sufficient heat to cause ignition or explosion. May ignite spontaneously in air or oxygen. Burns violently, accompanied by explosions which cause spattering...
Source: Hazardous Substances Data Bank (HSDB)
Fire and explosion
Mixture of solid forms of potassium & carbon dioxide (as dry ice) explodes when subjected to shock. ... Potassium & its alloys form explosive mixtures with carbon tetrachloride /and/...chlorinated hydrocarbons.
Source: HSDB
EXPLOSION HAZARD: MODERATE, BY CHEMICAL REACTION. K METAL WILL FORM PEROXIDE (K2O2) & SUPEROXIDE (KO2 & K2O4) @ ROOM TEMP EVEN WHEN STORED UNDER MINERAL OIL. METAL WHICH HAS OXIDIZED ON STORAGE UNDER OIL MAY EXPLODE VIOLENTLY WHEN HANDLED OR CUT.
Source: HSDB
10 · Handling and storage
Potassium storage and handling
Potassium peroxide formation
A: Compounds that form explosive levels of peroxides without concentration
Source: Lab and Research Safety, University of Minnesota
Potassium safe storage
Fireproof. Keep under mineral oil. Dry. Well closed.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
Potassium storage conditions
PROTECT AGAINST PHYSICAL DAMAGE. KEEP AWAY FROM WATER OR LOCATION WHERE WATER MAY BE NEEDED FOR FIGHTING FIRE... AVOID HIGH TEMP. STORE UNDER NITROGEN OR KEROSINE. NEVER STORE UNDER HALOGENATED HYDROCARBONS. DETACHED FIRE-RESISTIVE BUILDING RECOMMENDED FOR QUANTITY STORAGE.
Source: Hazardous Substances Data Bank (HSDB)
Potassium incompatible materials
Reacts violently with water, carbon dioxide or carbon tetrachloride.
Source: Hazardous Substances Data Bank (HSDB)
Planning storage for a mix of chemicals? Check Potassium in the storage compatibility matrix →
11 · Transport
Potassium 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.
Potassium under UN 2257 — shipping name, class and packing group
Europe · ADR 2025, Table A
| Proper shipping name (3.1.2) | Class | Classification code | PG | Labels (column 5) |
|---|---|---|---|---|
| POTASSIUM | 4.3 | W2 | I | |
Source: ADR 2025, Table A of Chapter 3.2 · ECE/TRANS/352 Vol. I (UNECE). Class 4.3 is “Substances which, in contact with water, emit flammable gases” (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) |
|---|---|---|---|
| Potassium | 4.3 | I | |
Source: 49 CFR 172.101 Hazardous Materials Table · eCFR, revision 2026-08-03. Class 4.3 is “Dangerous when wet material” (49 CFR 173.2).
12 · Questions
Potassium — frequently asked questions
What is the CAS number of Potassium?
The CAS number of Potassium is 7440-09-7. Its EC number is 231-119-8.
What is the chemical formula of Potassium?
The molecular formula of Potassium is K and its molecular weight is 39.098 g/mol.
What does a Potassium label have to show?
Under CLP Annex VI the label for Potassium carries the pictograms Flame and Corrosion and the signal word is Danger.
Is Potassium flammable?
Yes. CLP Annex VI assigns Potassium H260 — in contact with water releases flammable gases which may ignite spontaneously. The flash point reported for it is Not Applicable. Combustible solid. (USCG, 1999) (CAMEO).
Is Potassium a carcinogen?
CLP Annex VI records no harmonised carcinogenicity classification for Potassium. Annex VI is a list of agreed classifications, not a list of substances found safe, so this is an absence of a classification rather than a clean bill of health.
What is the boiling point of Potassium?
The boiling point reported for Potassium is 759 °C (1398.2 °F) (HSDB).
What is the melting point of Potassium?
The melting point reported for Potassium is 63.5 °C (146.3 °F) (HSDB).
How should Potassium be stored?
PROTECT AGAINST PHYSICAL DAMAGE. KEEP AWAY FROM WATER OR LOCATION WHERE WATER MAY BE NEEDED FOR FIGHTING FIRE... AVOID HIGH TEMP. STORE UNDER NITROGEN OR KEROSINE. NEVER STORE UNDER HALOGENATED HYDROCARBONS. DETACHED FIRE-RESISTIVE BUILDING RECOMMENDED FOR QUANTITY STORAGE. (Hazardous Substances Data Bank (HSDB))
Nearby
Substances next to Potassium
Keep going: substances starting with P, or search the whole database by name, CAS number, pictogram or signal word.