Common synonyms

Caustic potash, lye

Formula

KOH

Physical properties

Form: White semi-transparent flaky solid
Stability: Stable, but hygroscopic. Absorbs carbon dioxide from the air.
Melting point: 360 C
Water solubility: high (dissolution is very exothermic)
Specific gravity: 2.04

Principal hazards

** Contact with the eyes can cause serious long-term damage
** The solid and its solutions are corrosive
** A significant amount of heat is released when potassium hydroxide dissolves in water; this may be sufficient to crack thin glassware if the solution is not stirred when dissolving the solid.

Safe handling

Always wear safety glasses. Do not allow solid or solution to come into contact with your skin. When preparing solutions swirl the liquid gently to prevent "hot spots" developing.

Emergency

Eye contact: Immediately flush the eye with plenty of water. Continue for at least ten minutes and call for immediate medical help.
Skin contact: Wash off with plenty of water. Remove any contaminated clothing. If the skin reddens or appears damaged, call for medical aid.
If swallowed: Drink plenty of water and call for immediate medical help.

Disposal

Small amounts of dilute potassium hydroxide can be flushed down a sink with a large quantity of water, unless local rules prohibit this. Larger amounts should be neutralised before disposal.

Protective equipment

ALWAYS wear safety glasses when handling potassium hydroxide or its solutions. For many chemicals safety glasses are needed because when the chemical gets in the eye it causes irritation; by contrast, potassium hydroxide can cause serious damage. If you need gloves, neoprene, nitrile or natural rubber are suitable for handling solutions at concentrations of up to 70%

Further information

Potassium hydroxide
Chemicals in the HSci database
More extensive safety data