Ammonium Hydroxide
FEATURES
HAZARDOUS MATERIALS
Ammonium hydroxide is a solution of ammonia in water. Its chemical symbol is NH4OH. It’s a corrosive, irritating, somewhat toxic, clear-to-translucent milky white liquid with the characteristic strong, pungent odor of ammonia. It’s used in the manufacture of ceramics, detergents, dyes, explosives, fertilizers, food additives, household cleaners, inks, lubricants, pesticides, pharmaceuticals, rayon, rubber, soaps, textiles, and other products. It’s shipped in the following grades: Technical, CP (chemically pure), 16%, 20%, 26%, 30%, 44%, NF (National Formulary), and FCC (Food Chemical Codex). The percentages indicate the amount of ammonia dissolved in water, while the word “Technical” and the letter designations indicate grades of purity.
Properties
Ammonium hydroxide has no flash point, and, as such, the solution will not bum. However, since the solubility of gases in water decreases as the temperature rises, ammonia will be liberated from the solution. Although ammonia is classified by the U.S. Department of Transportation (DOT) as a nonflammable gas because of the two criteria used to classify gases, it will burn. For DOT to classify a substance as a flammable gas, it must have a lower flammable limit no higher than 15% (ammonia’s is 16%) and a flammable range of at least 10% (ammonia’s flammable range is from 16% to 25%, a spread of only 9%). However, if a concentrated solution of ammonium hydroxide is subjected to heat in a confined area or where the ammonia may not be quickly dispersed, the lower limit of 16% may be reached, producing an explosive atmosphere. Ammonia gas will ignite at 1,204°F.
The specific gravity’ of ammonium hydroxide ranges from 0.9 to 0.96, depending on the concentration; its molecular weight is 35, and its vapor density is 0.59. At the highest concentration of ammonia in water —generally, 30% — the boiling point of ammonium hydroxide is 81°F, and the freezing point is -98.3%. Ammonium hydroxide is soluble in water in all proportions.
It’s classified by DOT as ORM-A (Other Regulated Material-A) when the concentration of ammonia in water is less than 12%, and by the Environmental Protection Agency as an environmentally hazardous substance when the concentration of ammonia is 12% or higher.
Hazards
Ammonium hydroxide is corrosive to human skin at concentrations near 10% and above. The higher the concentration of ammonia dissolved in water, the greater the hazard. At concentrations below 10%, severe irritation of the skin may result, depending on individual sensitivity. It’s corrosive to some metals, again depending on the concentration. These metals include aluminum, copper, lead, silver, tin, zinc, and alloys of these metals.
Ammonium hydroxide will react with different chemicals with varying degrees of violence. Explosive mixtures are possible in contact with calcium and mercury metals, halogens, calcium and sodium hypochlorites, and silver oxide. It will also react with acrolein, acrylic acid, dimethyl sulfate, the halogen acids, propylene oxides, silver nitrate and silver permanganate, and strong mineral acids. Combustible or toxic gases may be liberated by some of these reactions.
The vapors of ammonia as they are liberated from ammonium hydroxide will prove very irritating to human eyes and skin, and can cause burns and blisters when highly concentrated. Concentrations as high as 5,000 ppm (0.5%) may be fatal. At lower concentrations they will produce irritation of the respiratory system when inhaled. Other reactions include bronchitis and pulmonary edema.
Ingestion of liquid ammonium hydroxide may cause burning of the mouth, esophagus, and stomach, and ingestion of a very small amount of the concentrated liquid may cause death.
The odor threshold for the ammonia liberated from ammonium hydroxide may be as low as 0.04 ppm, depending on the individual. The threshold limit valuetime weighted average (TLV — TWA) for ammonia is 25 ppm and the short-term exposure limit (STEL) is 35 ppm for 15 minutes. Some references list the immediately dangerous to life and health (IDLH) level as 500 ppm.
Ammonium hydroxide presents a fire hazard only when sufficient amounts of ammonia are liberated from the solution to reach 16% concentration in air. This is difficult to do under “normal” conditions, but protection against explosions should always be sought. This is important, particularly in light of the somewhat misleading classification of ammonia as a “non-flammable” gas.
Spill situations
Even though the fire hazard may not be great unless concentrations of ammonia reach 16%, standard operating procedures for evolution of a flammable gas should be followed: Approach from upwind; eliminate all ignition sources (including all tools and equipment); keep all unauthorized personnel from the spill area; and evacuate people from the immediate area for an adequate distance downwind. The radius of evacuation and length dowmwind depend upon the size of the spill, the concentration of the liquid, the ambient temperature, the surrounding terrain, weather conditions, and possible chemical reaction. Evacuation distances of 1,000 feet in radius and one-half mile downwind are not uncommon.
The hazards of toxicity of ammonia are greater than the fire hazard under many conditions. The movement of vapors away from the spill should be prevented whenever people may be exposed. This can be done in several ways once the liquid is collected in containment ponds, pits, or trenches. (Normal diking materials, such as soil, sand, clay, peat moss, and other inert materials, may be used to create the containment pond.)
• Dilution: A fine water spray or fog may be used to “sweep” ammonia vapors from the air. Since ammonia is readily soluble in water up to nearly 30%, it will quickly dissolve in the spray or fog. The resulting solution may be added to the spill, but in any event, this runoff must be contained.
Synonyms
Ammonia aqueous
Ammonia liquor
Ammonia monohydrate
Ammonia solution
Ammonia water
Ammonium hydrate
Aqua ammonia
Aqueous ammonia
Household ammonia
Ammonia solution
Water of ammonia
Identification Numbers and Ratings
UN/NA
(United Nations/North America)
2073, 2672
CAS
(Chemical Abstract Service)
1336-21-6
RTECS
(Registry of Toxic Effects of Chemical Substances) BQ9625000 Syce
(Standard Transportation Commodity Code)
4935234, 4935280, 4940316, 4940347
CHRIS
(Chemical Hazard Response Information System)
AMH DOT
(U.S. Department of Transportation)
Corrosive, ORM-A (Other Regulated Material-A) than 12% ammonia concentration in water
EPA
(Environmental Protection Agency)
Environmentally hazardous substance when 12% or highe ammonia concentration in water
IMO
(International Maritime Organization)
8.0, corrosive
The spill may be diluted by the addition of water. This can be done deliberately by adding water from firehoses, or by sweeping the air above the contained liquid with water spray or fog. The containment ponds or pits must be large enough to be able to hold the diluted solution.
• Neutralization: The solution of ammonium hydroxide may be neutralized by adding the proper neutralization agents (as recommended by the manufacturers). One manufacturer recommends neutralization with “dilute acids,” probably dilute sulfuric and hydrochloric acids. These neutralizing agents should be used only by qualified individuals who understand the danger of using and handling acids (even dilute ones) and are aware of possible further environmental damage if the acid is accidently spilled, is too strong, or both.
Whenever neutralizing techniques are to be used, they should always be done so conservatively and safely at first by adding a small amount of the neutralizer to a small amount of ammonium hydroxide in a plastic bucket away from the spill. This technique is used to determine whether or not there will be reactions violent enough to make the problem worse, rather than solving it. If the small-scale test neutralization is successful, the neutralization agent may then be added to the container liquid. Some references call for neutralization with water, but this is really dilution.
• Suppression by foam: Foam may be added to slow the evolution of ammonia. This technique will also add to the volume of the contained liquid. If the spill has been contained in a deep pit with a small surface area, a tarpaulin or plastic sheeting may be used to cover it.
Ammonia’s low vapor density indicates that it will rise and disperse fairly rapidly if no wind is blowing. It will move with the wind, carried near the ground for some distance before it will rise and disperse, especially if the vapors are cool.
The liquid—either the original spill or a contained accumulation of original product plus runoff or water added for dilution purposes—may be removed by pumping into a secure container. Any pumping equipment should be explosion-proof, and should be constructed of materials that resist corrosion by ammonium hydroxide. Pumping involves agitation, which will liberate ammonia gas.
The spilled product may also be absorbed by adding soil, clay, sand, fly ash, cement powder, or other acceptable sorbent. It may also be adsorbed by using activated charcoal or vermiculite. Whenever either of these techniques is used, it must be remembered that the hazardous material is still present, though in another form. The absorbed (or adsorbed) material can still liberate ammonia gas under certain conditions, and must be disposed of in accordance with federal, state, and local laws. In any spill, the appropriate environmental protection agencies (probably in addition to the state EPA) must be notified. They will have the last say on removal of contaminated soil and eventual cleanup of the affected area.
Spilled product and contaminated runoff must be kept from entering sewers and waterways. If the spilled product does enter a sewer, sewage treatment operations must be notified immediately, and if the product enters a waterway, all downstream users must be notified immediately. If it’s possible to divert a small stream or other contaminated waterway into a containment area, it should be done. Once contained, neutralization agents may be added to the water, or aeration techniques such as sparging or air stripping may be perfonned.
The entrance of ammonium hydroxide into a sewer could be very dangerous, since the rapid movement of the liquid will cause agitation severe enough to liberate enough ammonia to reach toxic levels very rapidly. Also, since the liberation of ammonia is occurring in an enclosed space, an explosion hazard is imminent because it will be easy to reach the lower flammable limit rapidly. All that is lacking for an explosion is the occurrence of an ignition source.
Glossary
Alloy—A mixture of metals, usually prepared by melting the metals together. Concentration —The percentage of one material in another.
Flammable Range —The concentration of gas or vapor in air between the upper and lower flammable limits. Halogens—The elements of Group VII on the Periodic Table; fluorine, chlorine, bromine and iodine.
Halogen acids—Hydrofluoric acid, hydrochloric acid, hydrobromic acid, and hydriodic acid.
Lower Flammable Limit— (LFL) The minimum concentration of gas or vapor in air, below which ignition cannot occur. The mixture is said to be too lean. Sometimes called the Lower Explosive Limit (LEL).
Mineral acids—The acids of oxysalts. Examples are sulfuric acid, nitric acid, perchloric acid, chloric acid, chlorous acid, and hypochlorous acid. ORM-A—Other Regulated Material – Any material that is anesthetic, irritating, noxious, toxic, or has similar properties and can cause extreme annoyance or discomfort to passengers and crew in event of leakage (DOT). Upper Flammable Limit— (UFL) The maximum concentration of gas or vapor in air, above which ignition will not occur. The mixture is said to be too rich. Sometimes called the Upper Explosive Limit (UEL).
The entry of a small amount of spilled product into a large river will not be a major hazard downstream, although users must be notified immediately. There will be danger to aquatic life at the point of entry. Since dilution is a viable mitigation technique, this will occur naturally in a large body of moving water. The potential hazard at the source of entry will disappear as the product is diluted infinitely by the river. Environmental authorities will be testing the water downstream for the presence or absence of a hazard.
Fire situations
If a container of ammonium hydroxide is threatened by fire, it should be kept cool. Since the product is a gas dissolved in water, liberated ammonia and water vapor will rapidly build up pressure inside a container and will cause catastrophic failure of such container if not sufficiently vented and/or cooled.
It is conceivable that ammonia leaking from an ammonium hydroxide container would be ignited as it escaped through a safety relief device. If this occurs, the flame should be allowed to burn, unless some extraordinary circumstances demand that it be extinguished. Even though the hot gas may rise and disperse rapidly, it is probably better to let it burn than to release that much ammonia into the air. Once the gas has moved away from the vent, it will mix with air and disperse rapidly, lessening the chance of ignition. However, right near the vent, the concentration of ammonia is sure to be within the flammable range.
If a fire is burning near a spill or the containment pond or pit, the radiated heat will cause the liberation of ammonia. Again, the low vapor density and high lower flammable limit may lessen the chances of ignition of the gas, but emergency responders must be aware that the gas will burn.
Protective clothing
Protective clothing and equipment used for personal protection should keep the product from contacting the skin or eyes. Clothing made of impervious material should be used, in addition to rubber gloves and boots, splash-proof goggles, and face shields. Total encapsulating suits should be used, and manufacturers of those suits claim that protection from ammonium hydroxide is provided by suits made of butyl rubber, chlorinated polyethylene, natural rubber, neoprene, nitrile rubber, nitrile-butadiene rubber, polyethylene, polyurethane, polyvinyl chloride, styrene-butadiene rubber, and Viton. These suits should be used with positive-pressure self-contained breathing apparatus or air supplied by an umbilical.
Although some references suggest that the use of a cannister gas mask or ammonia cartridge respirator with a full facepiece may be safe under conditions of low concentrations of ammonia, it’s always safer to use the positive-pressure SCBA with full facepiece.
First aid
If the vapors of ammonia have been inhaled, move the victim to fresh air immediately. Artificial respiration must be administered if breathing is difficult or has stopped. (Warning: Mouth-tomouth resuscitation may expose the responder to the chemical in the victim’s lungs or vomit.) Get medical attention immediately.
If the liquid ammonium hydroxide has been ingested, and if the victim is conscious, administer large amounts of water. Do not attempt to make the victim vomit. Do not try to administer water to an unconscious victim. Get medical attention immediately.
If the liquid has made contact with the eyes, flush the eyes immediately with water for at least 15 minutes, occasionally lifting the eyelids. Get immediate medical attention.
If the liquid has made contact with the skin, immediately remove contaminated clothing, being sure to protect yourself against contact with the liquid. Wash affected areas with large amounts of water. Get immediate medical attention.
