Chemical Data Notebook Series:
Hydrogen peroxide, a colorless liquid with an acute irritating odor and sharp taste, is totally soluble in water. It may be shipped as nearly pure product, in solutions in water as low as 3%, and in varying concentrations in between. Obviously, the more concentrated the solution, the more hazardous the product, and even the dilute solution of 3% can cause problems.
Hydrogen peroxide’s molecular formula is H2O2. Note that when compared to the formula for water (H2O), there is an extra atom of oxygen in the hydrogen peroxide molecule.
water hydrogen peroxide
It is this extra atom of oxygen that is responsible for the chemical’s hazards.
The molecular weight of hydrogen peroxide is 34.0 and its specific gravity is 1.41. Hydrogen peroxide boils at 302°F and decomposes, liberating water and oxygen. Its freezing point of 31.3°F is very close to that of water. Hydrogen peroxide’s UN/NA designation is 2015 in the pure state, and 2014 and 2984 as solutions. Its STCC (Standard Transportation Commodity Code) numbers are 4918335, 4918776, 4918775. The U.S. Department of Transportation (DOT) classification is oxidizer, and the yellow placard with black lettering has a “flaming ball” in the upper half and the number 5 in the lower point. The IMO (International Maritime Organization) designation is 5.1, oxidizing substance. Its NFPA (National Fire Protection Association) rating is 2-0-3-OXY.
Hydrogen peroxide has many synonyms including albone, dihydrogen peroxide, hydrogen dioxide, hydrogen oxide, hydroperoxide, inhibine, peroxan, peroxide, superoxol, T-stuff, and perhydrol.
Hydrogen peroxide is an oxidizing agent, and therefore its principle uses are for its oxidizing power. It makes a very good oxidizer for liquid rocket engines, providing support for the burning of the fuel, which is sometimes hydrazine.
Hydrogen peroxide is a powerful bleach and disinfectant, both primary functions of an oxidizer. It bleaches by oxidizing organic pigments and dyes, rendering them colorless and exposing the underlying color of the material that was colored. In many cases, the oxidizing action will turn organic materials white or yellow, depending on the amount used and its concentration. The hydrogen peroxide used to bleach hair is usually about 6% in concentration, strong enough to cause scalp burns.
As a disinfectant, hydrogen peroxide operates by oxidizing organic material such as bacteria, “burning” them up. The hydrogen peroxide in your medicine cabinet is about 3% concentration, and is in a brown or amber plastic or glass bottle. The color of the bottle is necessary to screen out ultraviolet rays that would cause the decomposition of hydrogen peroxide into water and oxygen. The decomposition will also occur due to age and/or contamination. The next time you open the hydrogen peroxide bottle, do it slowly and hold it near your ear. A very slight hissing noise is caused by escaping oxygen, signaling slight decomposition of the product. It is probably still effective as an antiseptic, since the decomposition is probably slight.
Other uses of hydrogen peroxide include the manufacture of pesticides, dyes, pharmaceuticals, some plastic and rubber foams, and many other chemicals.
The main hazard of hydrogen peroxide is its oxidizing power. Although hydrogen peroxide does not burn, as an oxidizing agent, it will support combustion. The more concentrated the solution (up to 100%), the more powerful the oxidizing action. This means that in the presence of hydrogen peroxide, any substance that is not easily burned will become very combustible, and ordinary combustibles and other materials (such as metals) may become so flammable that they may literally explode.
The oxidizing hazard is present even if contact between the liquid and the fuel is avoided. If the hydrogen peroxide is released, the contamination of the liquid by dirt, metals, and many other materials will cause its decomposition. This decomposition causes a release of oxygen to the atmosphere, a considerably higher than normal percentage of oxygen in the vicinity of the spill. This, of course, provides extra support to combustion and, in some cases, allows an explosion to occur.
Hydrogen peroxide is very stable in its pure state, and its solutions are stable if kept uncontaminated. However, once exposed to contaminating materials, hydrogen peroxide becomes dangerously unstable. Again, the higher the concentration, the more dangerous a contaminated solution is. Once contaminated, decomposition may begin slowly (depending upon the type and amount of contaminant and the concentration of the hydrogen peroxide solution), or it may proceed at such a rate that the material may detonate! Every effort must be made to protect the purity of the product.
Contaminants include metals such as iron and any ferrous alloys, copper and its alloys, magnesium, chromium, zinc, lead, manganese, silver, or platinum. Several salts of these metals will also cause instability and decomposition, as will glycerines, alcohols, hydrazines, oxides, and many other materials including dirt.
Heat and light will also cause hydrogen peroxide to decompose. As mentioned previously, the ultraviolet portion of visible light must be kept from contacting the product, hence the use of amber or brown bottles. Heat will cause decomposition slowly at first, and then more rapidly. It could also proceed explosively.
Very concentrated or pure hydrogen peroxide is so sensitive to metallic contamination that the lining of the tanks on trucks and rail cars must be free of iron, copper, and other metals whose mere presence can cause the decomposition of the peroxide. For that reason, transportation and storage tanks holding hydrogen peroxide must be made of aluminum or glass and must be very smooth.
Hydrogen peroxide is not classified as a corrosive, but it will cause damage to living tissue when in contact with such tissue. Even dilute solutions such as those used to bleach hair will cause severe scalp burns if not washed away quickly. Severe eye damage, all the way to blindness, can be caused by contact with the liquid or vapor. Again, the more concentrated and the longer the contact, the more damage is done.
Hydrogen peroxide is also not classified as being toxic, but ingestion can cause severe damage to the esophagus and stomach. With enough damage, these organs can be destroyed.
Inhalation can cause pulmonary edema and, again, with enough exposure, permanent damage can be done.
Protective clothing must be selected to protect against contact with the liquid and/or mist. Positive pressure self-contained breathing apparatus (SCBA) must be used at all times.
Hydrogen peroxide in its pure state may attack many materials, so the wearer of a total encapsulating suit must satisfy himself in advance that his suit will protect him. Consult the manufacturer’s chart of chemical resistance to see if resistance is claimed for hydrogen peroxide (this should be done in all cases for all chemicals). Make sure the chart explains whether protection is afforded for pure material as well as for solutions of the peroxide.
Some of the materials that may offer protection include butyl rubber, nitrile rubber, neoprene, polyurethane, polyvinyl chloride, styrene-butadiene rubber, and Viton. Natural rubber and polyethylene may be good up to 70% solutions.
Alloy—A physical mixture of metals, usually created by melting the metals together. Alloys are not chemical compounds.
Concentration—The percent of
product dissolved in water.
Dilute—A weak solution (a very low percentage of product dissolved in water).
Dilution—The addition of water (or other substance) to reduce the concentration of active ingredient.
Ferrous—A material, usually a metal alloy, containing iron.
Neutralization—A technique used to render a hazardous substance harmless by the addition of another substance.
Oxidizer—A substance that contains oxygen and liberates it readily or in some other way supports combustion. Also called an oxidizing agent.
Remember that total encapsulating suits of the materials named must be verified as offering the proper protection. Obviously, thicker material will resist penetration better than thin material, and none of the above offer protection against detonations, explosions, or fire, all of which are possible with a hydrogen peroxide incident.
HANDLING Fire situation
Hydrogen peroxide does not burn, but it will provide oxygen to support a fire. This means that all fires involving hydrogen peroxide will be more intense than if the fuel were burning with the normal concentration of oxygen. Wherever water will be effective on the fuel involved, massive amounts are to be used when hydrogen peroxide is involved. In some cases, the fire may be so intense that unmanned monitors should be used.
Where there is fire and radiant heat or flames are impinging on containers of hydrogen peroxide, the emergency responder must be aware of the danger of catastrophic container failure. Remember that hydrogen peroxide is decomposed by heat, yielding water and oxygen. Any rupture of the tank will produce shrapnel, hot water, steam, some hydrogen peroxide, and oxygen, all hazardous in their own right. All containers should be kept cool if possible, but safety of firefighting personnel must take precedence. Unmanned monitors may be required and personnel withdrawn to a minimum radius of 2,000 feet.
If the rupture occurs, it will resemble a BLEVE (boiling liquid, expanding vapor explosion) in that the tank will fail in somewhat the same manner. However, a fireball will not be produced in the manner of easily liquified flammable gases. Instead of flammable gas being released instantaneously (as with propane or vinyl chloride) a tremendous quantity of oxygen will be released. When this occurs, whatever fuel was burning to cause the failure of the tank will begin to burn much more intensely. The resulting flare-up may be as bad as a fireball, with the flame concentrated on the ground.
In addition to the oxygen being released, hot water, steam, hot hydrogen peroxide, and hot metal will be propelled in all directions. The same degree of care must be exercised in this incident as would be necessary in fighting any other kind of tank fire.
Wherever hydrogen peroxide has been released, the emergency responder must realize that a liquid oxidizing agent is loose and will be mixing with organic materials. All organic materials burn, so two legs of the fire triangle are present, just waiting for an ignition source. The realization must also be made that materials that may not be considered hazardous because of relatively slow burning will now become extremely flammable. Examples might include heavy oils and asphalt.
Therefore, the first order of business (after evacuation, if necessary) is to try to prevent the mixing of the peroxide and a fuel. This may require one or more of the several following procedures:
Containment. Containment may be effected by either building dikes with sand, clay, and other materials or by digging pits. In either case, there will be seepage of the peroxide into the surrounding soil. This seepage not only produces a layer of contaminated soil that may have to be removed after the incident, it is also a source of contamination to the peroxide that will cause chemical decomposition with the liberation of oxygen. So, even if containment procedures are successful, there could be a constant liberation of oxygen to support a potential fire. There could also be mists and fumes of hydrogen peroxide, and, if so, these may be removed from the air by a fine spray or fog pattern. Be careful with the runoff.
Once contained, methods should be employed to either remove the product or render it harmless. Those removing contaminated organic material (such as the soil) must be warned that the mixture could be explosive!
Every effort must be made to prevent the liquid from entering a sewer or waterway. Sewers contain organic materials (fuels) that, once mixed with an oxidizing agent, may become extremely flammable. If the liquid enters a waterway, all downstream users, including water treatment plants, must be notified of the contamination. Damming and diking techniques should be employed if possible, but diversion of the water may be too large a problem to handle.
Removal. The liquid may be removed by pumping or suctioning the product into approved containers. Care must be taken to be sure that all pump and other surfaces contacted by the peroxide are made of materials impervious to attack by hydrogen peroxide. Also, the liberation of oxygen during pumping might cause internal pressures to build. The presence of this oxygen will make any surrounding combustibles highly flammable. In most instances, the safest policy is to allow the manufacturer or shipper to effect removal.
Dilution. If removal is not feasible, one method of slowing the release of oxygen and removing other hazards of hydrogen peroxide is to dilute the liquid by the addition of water. Of course, containment of the resulting solution poses a problem, and the risk of further ground contamination is increased. Just as the addition of water to a water-soluble flammable liquid will lower its flashpoint by spreading the molecules further and further apart, the hydrogen peroxide molecules are separated (and cooled), thus slowing the release of oxygen.
Neutralization. The neutralization of hydrogen peroxide is not the same technique as the neutralization of an acid by a base or some other neutralizing agent. This technique should not be attempted unless the proper neutralizing agents have been identified by the manufacturer or some other qualified expert. Even using the proper materials, the evolution of oxygen may be accelerated by the addition of another substance.
Since hydrogen peroxide is such a powerful oxidizing agent, it should never be stored near combustibles or any place where an accidental release will allow the liquid to flow to where combustibles are stored.
Handling of small containers of the highly concentrated liquid, such as glass bottles, should be done carefully to avoid conditions of heat, shock, or contamination. All containers, small or bulk, should be protected from heat sources.
Containers run the gamut from small, 3-ounce bottles to 30,000gallon railroad tank cars. Small bottles may be packaged in cardboard boxes and shipped in mixed truckloads, and truck tank wagons may carry solutions ranging from 30% concentration to nearly pure material. The purer the shipment, the more economical the shipping costs since the pure material may be diluted at its destination into the concentrations required by the user. Always take the conservative position and assume the peroxide is concentrated so that you may be prepared for the worst in case of an accidental release.
If someone has been splashed with hydrogen peroxide, all contaminated clothing must be removed and all affected parts of the body washed with copious quantities of water. Medical attention should be sought at once.
If contact with the eyes is made, flushing with water for at least 15 minutes is necessary, lifting the eyelids as often as possible. Again, immediate medical attention is required.
If the victim has swallowed the peroxide, he must be made to drink large quantities of water right away and vomiting must be induced. Immediate medical attention is mandatory.
For inhalation of mists and vapors, fresh air must be provided immediately. If breathing becomes labored, artificial respiration will be necessary until medical help arrives.
Hydrogen peroxide is an oxidizing agent whose oxidizing powers and other hazards depend upon its concentration. It is highly hazardous in a fire situation and its presence in an accidental release increases the potential for fire if none presently exists.
The release of hydrogen peroxide poses many problems, particularly those caused by the liberation of oxygen. Notify the manufacturer and/or shipper or other qualified experts immediately as well as all federal, state, and local environmental agencies.