Substance profile
Potassium hydroxide
Potassium hydroxide is white or colorless, orthorhombic, deliquescent pieces, lumps and is odorless.
01 · Identification
What Potassium hydroxide is
Potassium hydroxide is white or colorless, orthorhombic, deliquescent pieces, lumps and is odorless. Its molecular formula is HKO and its molecular weight is 56.106 g/mol. It boils at 1327 °C, melts at 406 °C.
Under the GHS it carries the signal word Danger. It is classed as corrosives.
Other names for Potassium hydroxide
- caustic potash
- KOH
- Battery
- Lye
- Potassa
- Potassium Hydrate
- Potassium Hydroxide (Lye)
- Potassium Hydroxide, Solid
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 |
|---|---|
| H302 | Harmful if swallowed. |
| H314 | Causes severe skin burns and eye damage. |
Precautionary statements: P260, P270, P280, P301, P310, P312, P330, P331
03 · Physical and chemical properties
Potassium hydroxide 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 | 1327 °C (2420.6 °F) | HSDB | |
| 1324 °C (2415 °F) | NIOSH | ||
| 1320 °C (2408 °F) | at 760 mmHg | CAMEO | |
| Melting point | 406 °C (762.8 °F) | HSDB | |
| 380 °C (716 °F) | NIOSH | ||
| 360 °C (680 °F) | CAMEO | ||
| Density | 2.044 g/cm³ | HSDB | |
| 2.04 g/cm³ | NIOSH | ||
| Solubility | Soluble in 0.9 part water, about 0.6 part boiling water | HSDB | |
| Soluble in ethanol, methanol | HSDB | ||
| Solubility in water, 121 g/100 g water at 25 °C | at 25 °C | HSDB | |
| Vapor pressure | 1 mmHg | at 714 °C | HSDB |
| 1 mmHg | at 713.89 °C | NIOSH | |
| 1 mmHg | at 718.89 °C | CAMEO | |
| Autoignition temperature | Not flammable (USCG, 1999) | CAMEO | |
| Lower explosive limit (LEL) | Noncombustible Solid; however, may react with H2O & other substances | NIOSH | |
| and generate sufficient heat to ignite combustible materials. | NIOSH | ||
| Corrosivity | Corrosive | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
04 · Handling and storage
Storing and handling Potassium hydroxide
Storage conditions
Keep container tightly closed in a dry and well-ventilated place. Absorbs carbon dioxide (CO2) form air. Air sensitive. Strongly hygroscopic. Storage class (TRGS 510): Non-combustible, corrosive hazardous materials.
Source: Hazardous Substances Data Bank (HSDB)
Incompatible materials
Acids, water, metals (when wet), halogenated hydrocarbons, maleic anhydride [Note: Heat is generated if KOH comes in contact with water & carbon dioxide from the air].
Source: Hazardous Substances Data Bank (HSDB)
Reactivity
POTASSIUM HYDROXIDE, SOLUTION is a strong base dissolved in water. Reacts exothermically with all acids. Slowly dissolves glass. Attacks aluminum and zinc to generate flammable hydrogen gas. Ignited a polyethylene container liner when mixed with potassium persulfate by release of heat and oxygen [MCA Case History 1155. 1955].
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check Potassium hydroxide in the storage compatibility matrix →
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