General Description
A white solid. Corrosive to metals and tissue. Used in soap manufacture, bleach, as an electrolyte in alkaline batteries, and as a food additive.
Reactivity Profile
POTASSIUM HYDROXIDE absorbs moisture readily forming caustic solution that attacks aluminum and zinc. A piece of potassium hydroxide causes liquid chlorine dioxide to explode [Mellor 2:289. 1946-47]. 1,2-dichloroethylene and potassium hydroxide forms chloroacetylene, which is explosive and spontaneously flammable in air. POTASSIUM HYDROXIDE, [DRY SOLID, FLAKE, BEAD, OR GRANULAR] is highly toxic [Rutledge 1968. p. 134]. A reaction between n-nitrosomethylurea and potassium hydroxide in n-butyl ether resulted in an explosion due to the formation of diazomethane [Schwab 1972]. Potassium persulfate and a little potassium hydroxide and water ignited a polythene (polyethylene) liner of a container by release of heat and oxygen [MCA Case History 1155. 1955]. Using potassium hydroxide to dry impure tetrahydrofuran, which contains peroxides, may be hazardous. Explosions have occurred in the past. Sodium hydroxide behaves in a similar way as potassium hydroxide [NSC Newsletter Chem. Soc. 1967]. A strong base. Forms caustic solution in water. [Merck 11th ed. 1989].
Air & Water Reactions
Hydrolysis generates enough heat to ignite adjacent combustible material [Haz. Chem. Data 1966]. Dissolves in water (with liberation of heat, may steam and spatter. Solution is basic (alkaline). Deliquescent
Hazard
Toxic by ingestion and inhalation, strong
caustic, handle with gloves or tongs, corrosive to
tissue. Eye, skin and upper respiratory tract irritant.
Health Hazard
Causes severe burns of eyes, skin, and mucous membranes.
Potential Exposure
KOH is generally used as an alkali
and in the manufacture of other potassium compounds.
Fire Hazard
Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Some are oxidizers and may ignite combustibles (wood, paper, oil, clothing, etc.). Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated.
First aid
Move victim to fresh air. Call 911 or emergency
medical service. Give artificial respiration if victim is not
breathing. Do not use mouth-to-mouth method if victim
ingested or inhaled the substance; give artificial respira-
tion with the aid of a pocket mask equipped with a one-
way valve or other proper respiratory medical device.
Administer oxygen if breathing is difficult. Remove and
isolate contaminated clothing and shoes. In case of contact
with substance, immediately flush skin or eyes with
running water for at least 20 minutes. For minor skin
contact, avoid spreading material on unaffected skin. Keep
victim warm and quiet. Effects of exposure (inhalation,
ingestion or skin contact) to substance may be delayed.
Ensure that medical personnel are aware of the material(s)
involved and take precautions to protect themselves.
Medical observation is recommended for 24?48 hours after
breathing overexposure, as pulmonary edema may be delayed. As first aid for pulmonary edema, a doctor or
authorized paramedic may consider administering a drug or
other inhalation therapy.
Shipping
UN1814 (solution) & UN1813 (solid); Potassium
hydroxide, solid or solution, Hazard class: 8; Labels:
8-Corrosive material.
Incompatibilities
A strong base. Violent reaction with
acids, alcohols, water, metals (when wet), halogenated
hydrocarbons; maleic anhydride. Heat is generated if KOH
comes in contact with water and carbon dioxide from
the air. Corrosive to zinc, aluminum, tin and lead in the
presence of moisture releasing combustible/explosive
hydrogen gas. Can absorb water from air and give off
sufficient heat to ignite surrounding combustible materials.
Waste Disposal
Dilute with large volume of
water, neutralize and flush to sewer
Physical properties
White rhombohedral deliquescent crystal; density 2.044 g/cm3; melts at 360°C; vaporizes around 1,320°C; highly soluble in water, 107 g/100mL at 15°C and 178 g/100mL at 100°C; aqueous solution highly alkaline, pH of 0.1M solution is 13.5; soluble in alcohol and glycerol; insoluble in ether and liquid ammonia.
Application
Potassium hydroxide is used as an emulsifier in lotions and as an alkali in liquid soaps, protective creams, and shaving preparations. Depending on the concentration used, it can be highly irritating to the skin and/or cause a burning sensation. It is used in making potassium salts, in electroplatingand lithography, in printing inks, as a mordantfor wood, and finds wide applicationsin organic syntheses and chemical analyses.
Definition
ChEBI: Potassium hydroxide is an alkali metal hydroxide.
Indications
Potassium hydroxide (KOH) is a strong alkali that digests proteins and epidermal
debris. In one study, 10% solution was applied b.i.d. to each lesion for 30 days with excellent clearance. The side effects included stinging of the lesion and one case of secondary infection. Also reported were the occurrence of a hypertrophic scar
as well as some persistent or transitory hyper- and hypopigmentation. The same
authors who used the 5% KOH solution completed further studies and they found
it to be as effective-yet with decreased side effects.
Flammability and Explosibility
Sodium hydroxide and potassium hydroxide are not flammable as solids or aqueous
solutions.
Pharmaceutical Applications
Potassium hydroxide is widely used in pharmaceutical formulations
to adjust the pH of solutions. It can also be used to react with weak
acids to form salts.
Therapeutically, potassium hydroxide is used in various
dermatological applications.
Safety
Potassium hydroxide is widely used in the pharmaceutical and food
industries and is generally regarded as a nontoxic material at low
concentrations. At high concentrations it is a corrosive irritant to
the skin, eyes, and mucous membranes.
(rat, oral): 0.273 g/kg
storage
splash goggles and impermeable gloves should be worn at all times when handling these substances to prevent eye and skin contact. Operations with metal hydroxide solutions that have the potential to create aerosols should be conducted in a fume hood to prevent exposure by inhalation. NaOH and KOH generate considerable heat when dissolved in water; when mixing with water, always add caustics slowly to the water and stir continuously. Never add water in limited quantities to solid hydroxides. Potassium hydroxide should be stored in an airtight, nonmetallic container in a cool, dry place, separated from acids and incompatible substances.
Purification Methods
Its carbonate content can be reduced by rinsing KOH sticks rapidly with water prior to dissolving them in boiled out distilled water. Alternatively, a slight excess of saturated BaCl2 or Ba(OH)2 can be added to the solution which, after shaking well, is set aside so that the BaCO3 is allowed to separate out. Davies and Nancollas [Nature 165 237 1950] rendered KOH solutions carbonate free by ion exchange using a column of Amberlite IR-100 in the OH-form.
Regulatory Status
GRAS listed. Accepted for use in Europe in certain food
applications. Included in the FDA Inactive Ingredients Database
(injections, infusions, and oral capsules and solutions). Included in
nonparenteral and parenteral medicines licensed in the UK.
Included in the Canadian List of Acceptable Non-medicinal
Ingredients.
