CHEMICAL DATA NOTEBOOK SERIES #42 POTASSIUM HYDROXIDE
HAZARDOUS MATERIALS
POTASSIUM HYDROXIDE is a corrosive, water-reactive, irritating, deliquescent, odorless white solid available in granule, flake, bead, lump, pellet, or stick form. It is nonvolatile and nonflammable. It is used in the manufacture of dyes, fertilizers, herbicides, paint and varnish removers, paper products, and soap. It is also found wherever printing or electroplating is done and is used in alkaline storage batteries and some fuel cells.
PROPERTIES
Potassium hydroxide does not burn, but its reaction with some substances releases either large amounts of heat, flammable gases, or both. When exposed to fire and heated severely, it decomposes to emit potassium oxide as toxic fumes. Its specific gravity is 2.04, its molecular weight is 56.11, its melting point is 692°F, and it is very soluble in water (with which it reacts violently). Its chemical formula is KOH.
[Note: Sodium hydroxide, a chemical with similar physical and chemical properties, is also known as lye (a synonym of potassium hydroxide), which can cause confusion. Since both chemicals are very hazardous and similar in properties, the same mitigation techniques will safely handle both chemicals.)
HAZARDS
Potassium hydroxide is an extremely corrosive material. Concentrated solutions of the product dissolved in water are as corrosive as many acids and cause severe damage to human tissue. These solutions (as well as wet potassium hydroxide) corrode many metals, such as aluminum, lead, tin, and zinc, releasing highly flammable hydrogen gas. Solutions of potassium hydroxide are slippery to the touch, as the upper layers of skin begin to dissolve.
Potassium hydroxide is very waterreactive, generating great amounts of heat when it contacts water: The water is heated to the point that it generates steam and causes violent boiling. The resulting solution is corrosive and hot. Often, enough heat is generated to ignite normal combustible materials.
Potassium hydroxide is a very reactive chemical, reacting violently and very dangerously with acids, alcohols, explosives, metals, organic peroxides, sugars, and water. It also reacts with such diverse chemicals as acrolein (an aldehyde); acrylonitrile (an organic cyanide); chlorine dioxide; 1,2-dichloroethylene and trichloroethylene (chlorinated hydrocarbons); nitrogen trichloride; nitrophenol; nitromethane; nitroethane and nitropropane (nitrated hydrocarbons); tetrahydrofuran; and mixtures of chloroform and methyl alcohol, chlorine and hydrogen peroxide, and chlorine and calcium carbide. In spite of this wide range of dangerous reactions, potassium hydroxide still is considered a very stable chemical.
Inhalation of potassium hydroxidedust causes severe nose and mouth burns, inflammation of the upper respiratory tract and lungs, and possibly pneumonitis. Inhalation of mists of potassium hydroxide solutions causes the same problems.
Ingestion of the solid material or concentrated solutions of potassium hydroxide in water causes burns of the mouth, throat, and stomach and may cause perforation of the intestinal tract. The esophagus may become constricted. Severe abdominal pain follows, then nausea, vomiting, diarrhea, and possibly death.
Contact with the eyes or skin by the solid material or concentrated solution causes severe skin burns and permanent eye damage.
The TLV-TWA of potassium hydroxide is 2 mg/m3 (milligrams of product per cubic meter of air).
Potassium hydroxide is sometimes referred to as an alkali, alkaline material, or caustic material. The words alkali and alkaline have the same meaning when attached to a substance like a hydroxide; the material has a pH greater than 7.0. Caustic refers to its corrosiveness, which is substantial in the case of potassium hydroxide.
Chemically, potassium hydroxide is a base, which means it is the chemical opposite of an inorganic acid —that is, when a base is mixed with an inorganic acid in the proper proportions, the resultant products are a salt plus pure water. This is a classic neutralization reaction. An example would be the addition of potassium hydroxide to hydrochloric acid as follows: KOH + HCl KCl + HOH (potassium hydroxide plus hydrochloric acid yields potassium chloride plus water).
Adding exactly the right amount (in grams) of potassium hydroxide to exactly the right amount of hydrochloric acid forms an exact amount of potassium chloride and pure water (at a pH of 7.0). Determine the exact amount needed by looking up the atomic weights of the elements in the compounds on the left side of the equation (the reactants) and using the same amount of grams as atomic weight of each of the reactants. The reaction will always take place in proportion to the molecular weight of the reactants, and the products will include potassium chloride, water, and whatever reactant was in excess of the proper ratio.
The temptation is to use a strong acid such as hydrochloric to neutralize spills of potassium hydroxide. How ever, it is not always a good idea to mitigate an incident involving one very hazardous material by using another very hazardous material.
NONFIRE RELEASE
In any release of hazardous materials, standard operating procedures guiding the mitigation of this event should include, near the very beginning, the notification of environmental authorities. Preplanning of any incident, and indeed, all training for a hazardousmaterials incident, should include interaction with environmental authorities, especially local personnel. Procedures must be set up in advance to automatically trigger an alert to these people. During an incident their input will be invaluable to the incident commander, who must make all decisions regarding public safety.
In the event of a release of the solid material, guide efforts toward keeping the product contained and dry, and alert the proper environmental authorities. If the release occurs on a windy day, and the potassium hydroxide is in powder form, the blowing powder creates a cloud of dust that can cause serious injuries.
SYNONYMS
caustic potash
KOH
lye
potassa
potassium hydrate
Breathing the dust causes serious mouth, nose, and respiratory system irritation and burns. Eye and skin injuries are also possible, so cover the material (or otherwise protect it from the wind) as soon as possible. Evacuation may not be necessary, as people are safest from the dust if they remain in their homes.
IDENTIFICATION NUMBERS AND RATINGS
CAS
(Chemical Abstract Services)
1310-58-3
STCC
(Standard Transportation Commodity Code)
4935225 (solid); 4935230 and 4935244 (in water)
RTECS
(Registry of Toxic Effects of Chemical Substances)
TT2100000
UN/NA
(United Nations/North America)
1813 (solid); 1814 (solutions)
CHRIS
(Chemical Hazard Response Information System) PTH
DOT
(U.S. Department of Transportation)
Corrosive
NFPA 704 Rating
(National Fire Protection Association)
3-0-1
IMO
(International Maritime Organization)
8, corrosive
Another reason for covering the material quickly is if rain is imminent. Potassium hydroxide reacts very rapidly and violently as the rain contacts it. Very soluble in water, it dissolves and forms very concentrated (and very corrosive) solutions that can flow away from the original spill site. The solution becomes very hot from the exothermic reaction typical of KOH and water. The same problem can arise if the humidity is very high and the chemical absorbs enough moisture from the air to dissolve itself.
GLOSSARY
Alkali—any substance that has a pH greater than 7.0 (neutral). The chemicals known as alkalis are corrosive.
Alkaline—the property of being an alkali.
Base—a chemical compound that contains the hydroxide ion (OH-1), is the chemical opposite of an inorganic acid, and is active chemically.
Caustic—any strongly alkaline substance that has a corrosive effect on tissue; usually refers to bases.
Deliquescent—the property by which a substance absorbs moisture from the air in such quantities that it dissolves in that moisture.
Exothermic—the action of the liberation of heat.
Inorganic acids—usually called mineral acids, they are ionic in composition and contain the hydrogen ion (H+1).
Neutralization—a particular type of chemical reaction in which an acid or base reacts with another material, producing a solution with a pH of 7.0.
Water-reactive—a material that reacts with water in a violent or dangerous manner and includes the evolution of hazardous products, heat, or violent spattering.
Once you cover the material, a professional salvage firm can salvage it, using vacuum equipment to pick it up. If the product is not dusty but in bead or larger form, mechanical equipment or shovels can scoop it up carefully and place it into secure containers. All tools and equipment used must be compatible with the product.
If rain or another source of water reaches the solid product, a violent, heat-producing reaction occurs before the product dissolves. This solution must now be contained with techniques used for hazardous liquids. You can push up dirt, sand, clay, and other materials into dikes to form a containment pond or dig a containment pit with a trench to lead the liquid to the pit. A professional salvage firm will then have to remove the liquid as well as any contaminated soil from the pit, pond, or diking materials.
If the potassium hydroxide has dissolved in water, or a solution of potassium hydroxide and water that has leaked is now contained, there is no great danger to human life as long as no one comes in contact with the solution. The solution is nonflammable, although the action of potassium hydroxide in contact with water might generate enough heat to ignite ordinary combustibles. The major hazard in this scenario is the corrosiveness of the solution. If only enough water to totally dissolve the product is present, the solution is every bit as corrosive and hazardous as a concentrated inorganic acid. In the event that this happens, the emergency responder’s primary job is to secure the area, keep all unauthorized persons away from the liquid, and keep the solution from spreading. As long as no splashing occurs and no spray or mist is generated from the contained liquid, there is no immediate danger.
You must keep environmental authorities informed of each step and heed their advice, especially when the product is in a solution. They should oversee removal of the liquid and determine the amount of contaminated soil and other material to be removed.
One of the mitigation techniques for a strong basic solution is to neutralize it with an inorganic acid, as mentioned above. This technique should only be used by those with extensive training and proper equipment. Neutralization might be carried out on a very small spill, and very carefully at that. Whatever acid is selected (hydrochloric and sulfuric acids are common enough to be available), first add a small amount of it to a small sample of the caustic solution to check for violent reactions. The more concentrated the acid, the more hazardous the neutralization attempt. Dilute solutions of strong acids are preferable if available. Exercise care, even if the acid is dilute. One reference recommends using dilute acetic acid (an organic acid) after the potassium hydroxide itself has been diluted. Again, neutralization should be left to the professionals under the watchful eyes of environmental experts—under no circumstances should the fire department undertake this risky task.
Another technique is dilution with water. The more water you add to the solution, the less hazardous it will be. However, the main drawback here is the amount of water needed to dilute beyond danger. First, such an amount might not be available. Second, a containment pond or pit must be large enough to contain the extra volume, which might be anywhere from 10 to 100 times the original volume of the spill. Third, a knowledgeable person must test the dilution to determine its safety. Fourth, removal of the increased volume may be very costly. Fifth, adding water to the solid causes a violent reaction.
If the volume of liquid spilled is not great, or if enough sorbent material is available, the technique of absorption is another possibility. Materials that absorb a solution of potassium hydroxide include cement powder, clay, fly ash, sand, and soil. These materials must be added in quantities that will dry up the entire spill. The sorbent must also be dry to prevent a reaction with the water. Once the sorbent absorbs the solution, the resulting mixture is still hazardous because of the presence of potassium hydroxide but is much easier to handle. This mitigation technique should be carried out under the supervision of the environmental authorities, and the disposal of the absorbed materials and any contaminated soil must comply with all environmental regulations.
Keep the solution of potassium hydroxide from entering sewers or waterways, even though dilution occurs fairly quickly in a large, rapidly moving waterway. If the solution does enter a sewer, alert the sewage treatment plant to the amount and concentration of the solution. Calculations can determine if the solution will be rendered harmless by flushing the sewer with very large quantities of water. Still notify the treatment facility, since an unusually large volume of water is being added to the system in a short period of time.
If the sewer is a storm sewer that empties into a waterway, the environmental experts must determine whether dilution will solve or aggravate the problem. Testing will determine the harmfulness of the dilute solution reaching the watenvay.
If solid product is accidently released into a large, rapidly moving waterway, dilution will be rapid. However, a more serious condition arises when solid material enters a sewer. Usually, the volume of moving water in a sewer is small, and the exothermic reaction is great enough to ignite most organic materials present in sewers. Once you notify the treatment facility of the release, rapid action involving flushing may be necessary.
In all situations, inform the environmental authorities of all plans of action. If no human life is threatened, and no serious damage to property and systems is imminent, the emergency responders should follow the experts’ suggestions. The incident commander, who makes the final decisions, still needs input from all available resources.
FIRE SITUATION
Although potassium hydroxide is not flammable, problems can occur if the material is involved in a fire or is present during firefighting. If water used to fight the fire contacts the solid product, it generates more heat, which may cause the fire to spread faster. Also, the runoff water then contains dissolved potassium hydroxide, creating problems already mentioned. You may have to alter firefighting procedures if you have to contain large volumes of water.
If containers of solutions of potassium hydroxide are present and are receiving energy from flame contact or radiated heat, a pressure-relief explosion is possible. If the rising pressure produced by the absorbed heat is not relieved, a catastrophic failure of the container with resulting shrapnel is possible. Firefighters have to keep these containers cool by applying some of their water supply from as far away as possible.
Inside a manufacturing facility where potassium hydroxide may be present, firefighters have to protect themselves from material being thrown around by the dynamics of the fire and also from the possible splashing of highly concentrated solutions of the caustic material.
PROTECTIVE EQUIPMENT AND CLOTHING
Protective equipment and clothing must prevent contact of the material with the eyes, skin, and respiratory system. Rubber boots, gloves, aprons, and turnout gear should be similarly resistant to this corrosive. Wear safety goggles and splash-proof goggles (for solutions) and face masks impervious to potassium hydroxide to protect the face and eyes.
Where a danger exists of dusts or mists blowing around, wear total encapsulating suits. These suits offer protection up to 70 percent concentration of the product in water. Manufacturers of such suits claim that rubber materials such as butyl, natural, neoprene, and nitriles offer protection, in addition to such blended compounds as neoprene/ SBR (styrene-butadiene rubber), SBR, and NBR (nitrile-butadiene rubber). Plastics such as polyethylene (PE) and polyvinyl chloride (PVC) also offer protection. Wear positive-pressure, selfcontained breathing apparatus in the presence of dusts and mists.
FIRST AID
For inhalation, remove victims to fresh air and keep them warm and quiet. Administer artificial respiration if breathing stops or becomes difficult. Be careful to avoid exposure to the product in the victim’s lungs or vomit. Seek medical attention as soon as possible.
For eye contact, immediate medical attention is mandatory. Until it is provided, flush the eyes with water for at least 15 minutes, lifting the lids periodically.
For skin contact, remove all contaminated clothing and wash all contacted areas with large amounts of water Immediate medical attention is necessary.
For ingestion, give the victim large quantities of water to drink. Don’t induce vomiting, and never try to make an unconscious person drink anything. Seek immediate medical attention.
