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 · GHS classification
Hazards and label elements
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
| Code | Hazard statement |
|---|---|
| H260 | In contact with water releases flammable gases which may ignite spontaneously. |
| H314 | Causes severe skin burns and eye damage. |
Supplemental EU statements: EUH014
03 · 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.
| 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 | ||
| Melting point | 63.5 °C (146.3 °F) | HSDB | |
| 62.78 °C (145 °F) | CAMEO | ||
| 63.2 °C (145.8 °F) | ICSC | ||
| Density | 0.856 g/cm³ | ICSC | |
| 0.862 g/cm³ | at 20 °C | HSDB | |
| 0.86 g/cm³ | at 20 °C | CAMEO | |
| 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 | ||
| Vapor pressure | 8 mmHg | at 432 °C | HSDB |
| Vapor pressure at 20 °C: negligible | at 20 °C | ICSC | |
| Flash point | Not Applicable. Combustible solid. (USCG, 1999) | CAMEO | |
| Vapor density | 1.4 (air = 1) | HSDB | |
| 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.
04 · Fire and explosion
Fire and explosion behaviour of Potassium
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.
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
05 · Handling and storage
Storing and handling 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)
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 →