Sodium hydroxide

(Sodium hydrate, caustic soda, lye, caustic)

CAS 1310-73-2

Potassium hydroxide

(Potassium hydrate, caustic potash)

CAS 1310-58-3

bp 1390 °C, mp 318 °C

Highly soluble in water (109 g/100 mL)

bp 1320 °C, mp 360 °C

Highly soluble in water

Extremely corrosive; causes severe burns to skin, eyes, and mucous membranes.

The alkali metal hydroxides are highly corrosive substances; contact of solutions, dusts, or mists with the skin, eyes, and mucous membranes can lead to severe damage. Skin contact with the solid hydroxides or concentrated solutions can cause rapid tissue destruction and severe burns. In contrast to acids, hydroxides do not coagulate protein (which impedes penetration), and metal hydroxide burns may not be immediately painful while skin penetration occurs to produce severe and slow-healing burns. Potassium hydroxide is somewhat more corrosive than sodium hydroxide. Contact with even dilute solutions will also cause skin irritation and injury, the severity of which will depend on the duration of contact. Eye exposure to concentrated sodium hydroxide or potassium hydroxide solutions can cause severe eye damage and possibly blindness. Ingestion of concentrated solutions of sodium hydroxide or potassium hydroxide can cause severe abdominal pain, as well as serious damage to the mouth, throat, esophagus, and digestive tract. Inhalation of sodium/potassium hydroxide dust or mist can cause irritation and damage to the respiratory tract, depending on the concentration and duration of exposure. Exposure to high concentrations may result in delayed pulmonary edema.

Repeated or prolonged contact may cause dermatitis. Sodium hydroxide and potassium hydroxide have not been found to be carcinogenic or to show reproductive or developmental toxicity in humans.

Sodium hydroxide and potassium hydroxide are not flammable as solids or aqueous solutions.