CHEMICAL DATA NOTEBOOK SERIES #70: HYDRAZINE
HAZARDOUS MATERIALS
Hydrazine is an extremely reactive, corrosive, flammable, toxic, oily, fuming liquid with an odor similar to ammonia. One of the most hazardous chemicals in use today, it is used in the manufacture of antioxidants, explosives, medicines, pesticides, plastics, and other chemicals. Hydrazine also is used as a reducing agent (a substance that removes oxygen from a compound), rocket fuel, and solvent. It is an experimental carcinogen. It may be shipped as the pure material (anhydrous) or in concentrations in water as low as 35 percent. Its molecular formula is N2H4, also written H2NNH2.
PROPERTIES
Several references list hydrazine’s flash point as 100°F; at least one reference lists it as 1 24°F. Ordinarily, this would classify it as a combustible liquid rather than a flammable liquid, since flammable liquids have flash points below 100°F. However, in the presence of some materials, the igrti- tion temperature of hydrazine is lower than 100°F. For example, in the presence of ordinary rust, hydrazine will ignite at 74°F. In this situation, the iron oxide (the rust) obviously acts as a catalyst. Another strange property is that hydrazine’s flammable range is from 2.9 to 100 percent. This means that hydrazine will burn in the absence of oxygen.
Hydrazine’s specific gravity is 1.01, its molecular weight is 32, and its vapor density is 1.1. Hydrazine boils at 236.3°F, freezes at 35.6°F, and is soluble in water.
HAZARDS
Although hydrazine is classified as a flammable liquid (in anhydrous form and highly concentrated solutions), the major hazard may be its high degree of reactivity with so many chemicals. Hydrazine reacts spontaneously with oxidizing agents, resulting in its ignition. It is so highly reactive that it reacts with asbestos, cloth, wood, earth, and any oxidized metals. This series of reactions also results in the spontaneous ignition of the hydrazine. Metals that act as catalysts—such as cadmium, cobalt, copper, gold, molybdenum, platinum, and silver, as well as their alloys—must be prevented from contacting hydrazine. Many other chemicals produce violent or dangerous reactions with hydrazine; they include ammonia, chlorine, copper oxide, diethyl zinc, dinitrogen oxide iron, lead oxide, lithium, mercurv(I) chloride, mercury(II) chloride, nickel, oxygen, potassium, sodium, and tetryl. Classes of chemicals with which hydrazine reacts in a violent manner include chlorates, chlorites, chromates, hypochlorites, nitrates, nitrites, oxides, perchlorates, permanganates, peroxides, and other oxidizing agents.
Hydrazine is hypergolic with dinitrogen tetraoxide, which means a violent reaction is instantaneous on contact. This property makes hydrazine a good rocket fuel. In the vacuum of space, a rocket engine of considerable thrust will operate simply by allowing hydrazine and dinitrogen tetraoxide to mix together.
An extremely flammable liquid, hydrazine exhibits many strange properties under different conditions. Its lower flammable limit is reported in various references as either 2.9 or 4.7 percent. Since it always is safest to err on the side of conservatism, the lower flammable limit should be considered 2.9 percent. The really strange part is that the upper flammable limit is listed as a range of 98 to 100 percent, as if it could not be measured accurately. Considering that very few materials can burn in the absence of oxygen, this makes hydrazine very strange indeed. Substances that burn in the absence of oxygen, such as ethylene oxide (see Fire Engineering December 1986), can do so because they contain within their molecules oxygen released in a form that can support combustion. Hydrazine contains no oxygen within its molecules.
Acetylene (see Fire Engineering, October 1990), which can decompose inside its container with no oxygen present, represents another kind of chemical reaction —molecular decomposition. Perhaps the upper flammable limit of 100 percent means that hydrazine also decomposes inside its own container. Whatever the case, hydrazine is extremely hazardous.
Hydrazine decomposes when heated, and its oxidation can be catalyzed by the presence of certain types of metal. Hydrazine is such a powerful reducing agent (it reacts with just a small amount of oxidizer, such as oxygen, present) that it may begin burning at 98 percent concentration in air. The energy released by this reaction, even with a tiny amount of oxygen, may produce enough heat to cause the molecular decomposition of hydrazine rather than its burning. Whatever the explanation for the violence with which hydrazine reacts, hydrazine is a strange and dangerous material. Ignition and/or explosion can occur whenever any amount of it accidentally is released.
The ignition temperature is the second strange property of hydrazine that is difficult to explain. Ignitions have been reported at temperatures as high as 518°F when the only material hydrazine contacted was glass. In other situations, as when it came in contact with rusty iron (iron oxide), it ignited at temperatures as low as 74°F. Any material that can ignite simply by being warmed to 74°F (when a rusty surface is exposed to it) should be considered almost as dangerous as a pyrophoric material (a substance that reacts spontaneously in air).
The third strange property of hydrazine is its flash point, listed by some references as 1()0°F. It is not clear under what conditions the flash point should be considered 100°F, since some recorded instances show that the material ignited at 74°F. If the vapors ignite at 74°F under these conditions (the presence of rust), the flash point must be below 74°F under the same conditions. Since flash point is measured in the laboratory under very strictly controlled conditions and hydrazine (as well as almost all other hazardous materials) never is accidentally released under very strictly controlled conditions, the flash point data probably are meaningless. Therefore, whenever hydrazine is accidentally released, expect explosive ignition from the first moment the material contacts the air. Since there is absolutely no control over whether any catalysts (such as rust) will be present, it is possible for hydrazine to self-ignite on a warm day (above 74°F) as soon as it mixes with air.
Hydrazine is toxic by all routes of entry into the body. Its odor, described by some as fishy and by others as ammonia-like, can be detected by humans in concentrations as low as three ppm (parts per million in air). Its TLV-TWA (threshold limit valuetime weighted average) is 0.1 ppm, with an intended change to 0.01 ppm. Its IDLH (immediately dangerous to life and health) value is 80 ppm.
Inhaling hydrazine vapors will irritate the mouth, nose, and throat and can cause tissue burns. Mucous membrane tissue may be destroyed at high concentrations. Under conditions where vapors are highly concentrated, convulsions, pulmonary edema, damage to blood cells, liver and kidney damage, and ultimately death can occur. Rats exposed during experiment to concentrations of hydrazine vapors at 600 ppm for four hours have died. Low concentrations in air may not permanently damage human tissue, but they will greatly irritate the skin, eyes, mouth, throat, and respiratory system.
The eyes can be severely and often permanently damaged if liquid hydrazine or high concentrations of vapors come in contact with them. If the liquid contacts the skin, severe burns and possible destruction of tissue will result.
Ingesting hydrazine will severely damage the mouth, tongue, esophagus, and stomach by corrosive action. Symptoms prior to death can include convulsions and pulmonary edema. Ingestion of amounts too small to cause death can cause liver and kidney damage.
Hydrazine is corrosive not only to human tissue but also to many metals and alloys. Attacking metals is characteristic of hydrazine’s reactivity.
In situations where hydrazine is heated but does not ignite or decompose violently, molecular decomposition will yield nitrogen and ammonia. Nitrogen is an inert gas, while ammonia is a toxic, corrosive gas that burns, even though it is listed as a nonflammable gas.
Hydrazine is hygroscopic, which means that it will absorb moisture from its surroundings. This is hazardous, since it makes ordinary combustibles, having been dried out, more susceptible to ignition. This property also can lead to a mitigation technique, since hydrazine is so soluble in water.
NONFIRE RELEASE
The release of almost any quantity of hydrazine outside most industrial operations should activate the community emergency plan as dictated by SARA Title III (Superfund Amendments and Reauthorization Act of 1986). In addition to the mobilization of all safety forces, environmental experts also will be activated. Their monitoring efforts and advice during mitigation of the incident will be invaluable.
Hydrazine vapor is only slightly heavier than air, as its vapor density of 1.1 indicates. When released, hydrazine vapors sink slowly to the ground unless they are warmer than the surrounding air. Under those conditions, the hydrazine may or may not fall, depending on how warm the vapors are. However, any larger release of hydrazine is extremely dangerous, so evacuate within a radius of a minimum of a half mile of the spill and farther downwind. Evacuation distances may be increased significantly (to one or two miles, depending on the sizc[s] of the container[s] involved in the incident). Hydrazine vapors may ignite at any time, since even its highest recorded ignition temperature is relatively low and well within the range of all common ignition sources.
You must keep hydrazine from entering sewer systems or waterways. Dam all sewer openings and catch basins to prevent liquid from entering the sewer. If hydrazine enters a sewer, a highly explosive situation may exist due to the possible presence of materials that act as catalysts in the presence of hydrazine. If any metal articles are in the sewer and if any of them have oxidized even slightly, the ignition temperature of the hydrazine vapors may be as low as 74°F. Because of the decomposition of organic matter in sewers, this temperature easily can be reached, and it is almost guaranteed that oxidized metal articles will be present in a sewer. The conditions are set for an almost automaticexplosive situation. As in every situation involving a hazardous material entering a sewer system, warn all along the system of the particular dangers involved and immediately notify any sewage treatment facilities. The treatment facility operators will be interested in the amount and concentration of the material that entered the system and the location and time of entry.
If hydrazine enters a waterway, it will dissolve immediately in the water. It is a toxic material, and its presence will have a detrimental effect on wildlife. If the waterway is a fast-moving stream, the hydrazine will be diluted and carried aw’ay very rapidly, diminishing the effect it will have on fish, waterfowl, and other life in and near the w ater. If the waterway is a small and slow-moving stream, the effect will be more devastating. Damming and/or diverting the water for treatment w ill keep the problem from spreading. Once the water has been diverted to a low -lying area, a neutralizing agent may be added or the hydrazine may be removed from the water by aeration, air stripping, or sparging.
If the waterway is a large, slowmoving river, damming and/or diverting may not be possible. In any event, when hydrazine enters moving water, notify all possible downstream users at once.
If hydrazine enters a small pond, the problem w ill be isolated, although all fish and other animals living in the water may be poisoned. The resulting hydrazine solution may be neutralized by adding calcium hypochlorite to the water. Contact the manufacturer of hydrazine for other neutralization techniques. Ilie environmental experts responding to the release w ill monitor all water spills and advise on actions to take. For large lakes, the problem will be more severe, as the hydrazine will have more water in which to dissolve and disperse. While dilution of hydrazine is a valid mitigation technique, very low concentrations are toxic to aquatic life.
If large quantities of hydrazine vapor are leaking from their containers, the vapors may be removed from the air by dissolving them in water applied by a sw eeping motion of a highpressure water spray or fog pattern. This technique also is useful where vapors from a spill begin to move w ith a gentle breeze. Whenever this technique is used, however, the runoff water must be contained.
In the case of a liquid spill, the contamination can be prevented from spreading with a containment pond built by constructing dikes with drysand around the spill. Remember that the hydrazine may ignite spontaneously if it comes in contact with soil, so it may not be possible to build dikes around the spill. Hydrazine reacts with so many materials that ignition may occur right after the liquid is released.
If the liquid does not ignite, adding water will reduce the chances that it will. Dilution reduces most of the hazards, but the resulting solution must be contained. Alcohol foam may be applied to the surface of the spill to reduce the generation of vapors. It may break down after application, so reapplication will be needed. Again, the increased volume must be contained.
IDENTIFICATION NUMBERS AND RATINGS
CAS
(Chemical Abstract Services)
302-01-2
STCC
(Standard Transportation Commodity Code)
4906225—anhydrous form 4935030—water solution
RTECS
(Registry of Toxic Effects of Chemical Substances)
MU7175000
UN/NA
(United Nations/North America)
2029—solutions of more than 64 percent concentration
2030—solutions of 64 percent and lower concentrations
CHRIS
(Chemical Hazard Response Information System)
HDZ
RCRA
(Resource Conservation and Recovery Act)
U133
DOT
(U.S. Department of Transportation)
flammable liquid
NFPA 704 Rating
3-3-2
IMO
(International Maritime Organization)
3.3. flammable liquid—anhydrous form and solutions with higher than 64 percent concentration
8.0 corrosive—solution of 64 percent and lower concentration
One reference claims that calcium hypochlorite, added at a rate of seven pounds per every pound of hydrazine, will neutralize it. Before attempting this or any neutralizing procedure with any hazardous material, conduct a small experiment. Place a small sample of the spilled material in a plastic container in a safe place; then slowly add the neutralizing agent to the haz mat. Note any reaction, remembering that this reaction will occur on a large scale if carried out with all the spilled material. Only after the operation has been determined to be safe and worthwhile should it be attempted on the spill.
Salvage of the liquid must be carried out by professionals who are properly educated, trained, and equipped to do the job safely. Firefighters and other emergency responders should not be involved in salvage or cleanup operations at a hazardous-materials incident, especially with a material as hazardous as hydrazine. After being pumped out (or removed another way), the remaining hydrazine may be absorbed with dry sand or another nonporous, inert material. The material used for absorption now will be contaminated with hydrazine and will have many of the hazards of the pure material. It must be disposed of in compliance with federal, state, and local regulations. The environmental authorities will advise on disposal, perform constant monitoring duties, determine the degree of spread of contamination. and oversee the final removal of all contaminated materials.
FIRE SCENARIO
When hydrazine is released from its container as the pure material, particularly in a transportation accident, it is highly likely that the material will ignite fairly quickly. It is so reactive that it may ignite spontaneously on contact with soil, rusty metals, cloth, or wood. It is almost impossible to imagine a release where the spilled hydrazine will not contact one of these materials.
If, however, the hydrazine is still in its container and a fire is nearby or approaching, the container should be cooled by water applied by unmanned appliances from as far away as possible, because of hydrazine’s toxicity and the possibility of an explosion. If the container is leaking, the water, if not confined, will spread the contamination.
Burning hydrazine may be extinguished by applying alcohol foam, carbon dioxide, dry chemical, or water. Water and alcohol foam will add to the volume of the spill and must be contained. If the fire is extinguished, a serious danger of explosive reignition exists because of hydrazine’s extremely low ignition temperature. Almost any noncombustible material will be heated by the fire to a temperature above hydrazine’s ignition temperature, and this heated object or material will become the ignition source once the fire is extinguished.
If vapors are escaping from the container and arc burning, do not extinguish the flames unless you can stop the flow of fuel immediately after extinguishment. Getting near the container from which the burning vapors are escaping, however, is extremely dangerous, since it is possible for the flames to back up into the container or cause in some other fashion the hydrazine inside the container to decompose explosively. The best mitigation technique might be to allow the hydrazine to burn while protecting exposures. The deliberate ignition of hydrazine may be called for in a drastic situation. This action should be carried out only after input has been received from all advisers including the manufacturer, shipper, and user of the product, as well as environmental and other experts.
The combustion products of hydrazine include the highly toxic nitrogen oxides, which might produce death some 12 to 48 hours after exposure and inhalation.
SYNONYMS
anhydrous hydrazine
diamide
diamine
hydrazine, anhydrous
hydrazine base
hydrazine hydrate
PROTECTIVE CLOTHING AND EQUIPMENT
Wear protective clothing and equipment that prevent any contact of the hydrazine with the eyes or skin, including rubber gloves, aprons, and boots and splashproof chemical goggles. Use positive-pressure, self-contained breathing apparatus. Manufacturers of total encapsulating suits claim that suits made of butyl rubber, natural rubber, neoprene, nitrile rubber, and polyvinyl chloride offer protection. Protection from hazardous materials during mitigation is a relative term. For precise information, contact the suit manufacturer for the degree of safety offered by each recommended material; also consult the manufacturers of hydrazine.
FIRST AID
Inhalation. Move the victim to fresh air: keep him/her calm and warm. If the victim’s breathing has stopped or becomes labored, administer artificial respiration. Obtain immediate medical attention.
Eye contact. Flush the eyes immediately for at least 15 minutes, lifting the eyelids occasionally. Obtain immediate medical attention.
Skin contact. Wash the affected body areas with large amounts of soap and water. If irritation continues after washing, seek medical attention.
Ingestion. If the victim is conscious, make him/her drink large quantities of water immediately. Never try to make an unconscious person drink anything. Seek immediate medical attention. Do not induce vomiting unless advised to do so by medical authorities.
