Potassium hydroxide is commonly called caustic potash. It is an odorless inorganic compound, represented by the formula KOH. KOH is a thermally stable metallic base that appears as fine, white crystals. Potassium hydroxide mass produced for commercial and laboratory use is most often made in the form of pressed-solid, translucent white pellets. Potassium hydroxide is extremely corrosive, and it is extremely toxic. KOH is soluble in water, methanol and alcohol at room temperature.
The physical properties of potassium hydroxide are most similar to sodium hydroxide. The specific gravity of KOH is 2.04. Its pH is 13.5 in a 0.1 molar solution. Potassium hydroxide's boiling point is 1,320 degrees Celsius and 2,408 degrees Fahrenheit. Its melting point is 360 degrees Celsius and 680 degree Fahrenheit. KOH's vapor pressure at 0.1 millimeters of mercury is 714 degrees Celsius and 1,317 degrees Fahrenheit.
Potassium hydroxide is non-combustible. Contact with some metals, however, produces hydrogen gas, which is highly combustible. This makes KOH storage in closed containers an explosion concern, and it can make careless battery disposal a fire hazard. Dissolved in water, potassium hydroxide becomes highly caustic and can destroy aluminum and zinc. Accidental mixture of KOH with dichloroethylene can result in rapid spontaneous combustion, even explosion. Mixing KOH with aluminum will break down aluminum and produce alum, a substance used in water purification and cosmetics.
The National Institute for Occupational Safety and Health notes that potassium hydroxide is hazardous to people when it comes into direct contact with eyes, skin, the respiratory system and the digestive system. Ingestion or respiration of KOH can be fatal. Eye contact can result in degrees of injury from passing irritation to blindness. Skin contact can result in burns, and severe burns if the KOH is dissolved in water.