SODIUM
HAZARDOUS MATERIALSL
CHEMICAL DATA NOTEBOOK SERIES #54
Sodium is a water-reactive, elemental metal. Its two most common synonyms are metallic sodium and natrium, the Latin word from which sodium gets its chemical symbol, Na. It is silvery in appearance until exposed to air, whereupon it turns grayish in color. A scratch on the surface will expose the silvery metal below, which will then “gray off.” Sodium is used in the manufacture of sodium vapor lights, photoelectric cells, and electric power cables. In addition, it helps to reduce titanium metal from its ore and works as a heat exchange agent in nuclear reactors and some internal combustion engine exhaust valves. Because it is a polymerization catalyst, it is used to manufacture such chemicals as tetraethyl lead, tetramethyl lead, sodium hydride, and sodium peroxide. In the medical field, isotopes of sodium trace the movement of chemicals through the body. It is shipped either as a solid or the molten liquid. It is so soft as a solid it can be cut with a dull knife.
PROPERTIES
Sodium is a combustible metal and will ignite in moist air at about 250°F and in dry air at 1635°F. The solid has a specific gravity of 0.971, a molecular weight of 23, a melting point of 207.5°F, and a boiling point of 1621°F. It is violently reactive on contact with water -liberating hydrogen and forming sodium hydroxide. The reaction is so exothermic that enough heat is generated to ignite the hydrogen.
HAZARDS
Sodium is extremely hazardous when exposed to water and will react violently in moist air. Its affinity for oxygen is so great that when reduced in size to a powder form, it is pyrophoric (some references claim it will react in air violently even in the solid state).
Sodium’s strong desire for oxygen makes it extremely dangerous. The water molecule is very stable, requiring a tremendous amount of energy to break it up. Yet sodium does this easily and quickly on contact with water. A piece of sodium metal thrown into a vat of w ater w ill begin to break up, rather explosively, into small spherical pieces.
Because sodium’s specific gravity is less than 1.0, the “balls” of sodium float on water, rolling around and literally ripping apart the water molecule to get at the oxygen. This reaction forms sodium hydroxide, a powerful corrosive. It also liberates large amounts of heat energy’, which usually is sufficient to ignite the released hydrogen.
If a large enough amount of sodium metal is exposed to water, it will explode, producing many smaller pieces of sodium, which could ignite combustible material wherever they land.
Hydrogen has a very wide flammable range (4 percent to 75 percent) and relatively low ignition temperature (932°F). It burns with an extremely hot flame, which produces very little light. Because the flame is almost invisible, hydrogen may be burning and exposed people may be totally unaware of the danger.
Sodium hydroxide is a very powerful corrosive. Depending on the amount of sodium and water contacted, the resulting solution may be very caustic. Sodium hydroxide is corrosive to most metals, liberating hydrogen in the process. An aluminum (or certain other metal) container holding a small amount of water presents a dangerous scenario. If enough sodium is placed in the water, the resulting solution will be corrosive enough to attack the aluminum. The hydrogen released will be added to the hydrogen evolving from the initial contact of the sodium with the water. At least one reference says to use acetic acid to neutralize the solutions. (For more information on sodium hydroxide, see Fire Engineering, January 1987.)
IDENTIFICATION NUMBERS AND RATINGS
CAS
(Chemical Abstract Services)
7440-23-5
STCC
(Standard Transportation Commodity Code)
4916456
RTECS
(Registry’ of Toxic Effects of Chemical Substances)
VY0686000
UN/NA
(United Nations/North America)
1428
CHRIS
(Chemical Hazard Response Information System)
SDU
DOT
(U.S. Department of Transportation)
Flammable Solid
IMO
(International Maritime Organization)
4.3, Flammable Solid
There is a great risk of injury when encountering an accidental release of sodium and its subsequent contact with water. Although the situation is relatively uncommon, many firefighters have the opportunity to see this violent reaction in June of every year. This is when high school chemistry teachers clean out the chemistry lab and must dispose of leftover sodium metal (and potassium metal, which, for all intents and purposes, is identical to sodium). They call the local fire department to remove the unwanted chemicals (including some more and some less dangerous than sodium). The responder will usually then experiment with the sodium, which can cause injuries.
Sodium’s affinity for oxygen and its ability to rip molecules apart to get it means it must either be stored in a vacuum or under some material that will keep oxygen from reaching it. Sodium is often stored in containers filled with kerosene, which is a mixture of hydrocarbons, and therefore free of oxygen. Kerosene has been selected because of its oxygen-free nature and its relatively high flash point (100°F).
Quarter-pound “sticks” of sodium, roughly the same shape as butter or margarine sticks, are used by high school and college chemistry laboratories. The amount needed for the experiment or process is cut off from the large piece and the rest immediately placed back into the kerosene. The kerosene must not be allowed to evaporate off the surface of the sodium before use. A particularly humid atmosphere might provide enough moisture to begin the reaction as soon as the surface of the metal is exposed.
Sodium metals have a need to become “stable.” They will react violently with oxygen and any oxidizer or material containing a component that will satisfy sodium’s need to be oxidized. Therefore, in addition to oxygen and any chemical compound containing oxygen, such as oxides, sodium will react with any halogen (fluorine, chlorine, bromine, or iodine) and almost any compound containing them (compounds whose names include fluoride, chloride, bromide, and iodide). Sodium also will react with acids, azides, carbon dioxide, halogenated hydrocarbons, hydrazine hydrate, hydroxylamine, and nitromethane, as well as any’ substance in the presence of moisture.
Sodium is corrosive to human tissue and will cause severe burns to any skin contacted. Any contact with the eyes will result in thermal burns, including the violent reaction produced when sodium contacts water.
Sodium is seldom inhaled. Since the powdered metal is pyrophoric, it is very’ rare to find powdered sodium floating in the air. However, as sodium burns, sodium oxide fumes are formed, which are very’ irritating when inhaled. There is also a possibility that sodium hydroxide might exist in powdered or mist (dissolved in water) form. When inhaled, the corrosive action of sodium hydroxide can cause burns to the eyes, nose, mouth, and entire respiratory system.
Ingestion of sodium metal is also rare, but if it occurs, severe damage may cause permanent organ damage or death. There is no TLV-TWA (Threshold Limit Value-Time Weighted Average) or STEL (Short-Term Exposure Limit) published for sodium metal.
NONFIRE RELEASE
If sodium metal is released from its oxygen-free container, everyone and everything nearby is in great danger. Water or anything containing water must be kept from contacting the metal.
In the event of such a release, notify’ the shipper, the manufacturer, and the consignee of the shipment immediately’. These companies will have experience handling the metal, and their expertise will be required to mitigate the incident. Also notify the proper environmental authorities and any other resources present in the fire department jurisdiction.
If possible, the spilled product should be covered with plastic sheeting or any Other compatible material to keep moisture from reaching it. Dry graphite, powdered table salt (sodium chloride), or other dry powder also may be used.
Remove all unnecessary personnel from the spill site, and consider evacuation of nearby homes and other occupancies depending on the amount of sodium released. The spilled sodium metal must be returned to an oxygen-free environment as soon as possible. This should be done by professionals who have experience handling it.
The metal must be prevented from entering sewers and waterways for obvious reasons. Large chunks of sodium that enter a sewer and contact water will immediately explode into many smaller pieces, and these may also explode. The hydrogen generated during this series of reactions could build up enough gas to cause a large explosion. The ignition of organic matter in the sewer is also a possibility.
Any metal that enters a stream, lake, or other waterway will immediately explode into many smaller pieces, repeating the action mentioned above. Pieces of flaming metal may reach the banks and ignite any combustibles, causing many small fires. The generation of caustic sodium hydroxide may endanger any life in the waterway.
If sodium does enter a sewer, alert the sewage treatment plant immediately. It can take the steps necessary to handle any sodium hydroxide arriving in a concentrated solution. Also notify all downstream users of water that may be contaminated from metal entering a waterway. The environmental experts will monitor all waterways to determine the amount of contamination and when the water is safe to use.
In some situations, molten metallic sodium may be spilled. If so, a containment pond built by creating dikes of dry sand or dry earth, or a pit can contain the metal. Remember, any moisture will cause the sodium to react, usually explosively. If the amount of molten sodium is small enough that a pond or pit of sufficient size can be built or dug and there is no moisture present, add kerosene to the cooled product to cover it and keep it oxygen-free. In very small releases, the sodium may be scooped up with shovels and deposited into containers partially filled with kerosene.
All unreacted sodium should be removed and placed in secure containers as soon as possible. Salvage and cleanup should always be done byprofessionals. Firefighters should keep their contact with the metal to an absolute minimum. Any handling of the product must be done on an emergency basis only, with extreme caution, using compatible tools and protective clothing.
Any soil that has been contaminated with metallic sodium or sodium hydroxide solution may have to be removed under supervision of environmental authorities and disposed of in accordance with federal, state, and local regulations. Again, this task is for professionals who are properly educated, properly trained, and properly equipped.
All equipment and clothing used by emergency responders must be properly decontaminated after use.
GLOSSARY
Catalyst-any substance that, in small quantities, will affect the rate of a chemical reaction without being consumed in the reaction.
Caustic-any strongly alkaline substance that has a corrosive effect on tissue; usually refers to bases.
Elemental-having the properties of an element. An element is defined as a pure substance that cannot be broken down into simpler substances by chemical means. There are 106 known elements.
Exothermic-a chemical reaction where heat is liberated; contrast with endothermic, which is a chemical reaction where heat is absorbed by the reaction.
Gram-Molecular Weight-the atomic weight of an element or the molecular weight of a compound expressed in grams instead of Atomic Mass Units.
Isotope-a form of the same element having identical chemical properties but a different number of neutrons in the nucleus of its atoms.
Polymerization-a unique chemical reaction where a monomer (a relatively “tiny” molecule) reacts with itself to form a “giant” molecule called a polymer.
Pyrophoric-a substance that reacts in air.
FIRE SCENARIO
Burning sodium will produce potentially dangerous fumes, so all emergency responders must was positivepressure, self-contained breathing apparatus. Discharging water onto burning sodium will cause violent reactions, aggravating the situation. Drygraphite and powdered sodium chloride (table salt) are relatively effective at extinguishing burning sodium, and some references add powdered soda ash (sodium carbonate) and crushed limestone (calcium carbonate). If very large amounts of sodium are burning, the best response may be to withdraw and protect exposures.
A quick-thinking chemistry student devised a way to extinguish a small piece of burning sodium in a chemistry7 lab. After he had removed the sodium from its protective cover of kerosene, he accidently dropped it into the sink with some water on the bottom. He picked up the burning metal with long forceps and replaced it in its original container partly filled with kerosene. The kerosene ignited but produced only a small combustible liquid fire in a small container, which he quickly extinguished with a carbon dioxide extinguisher. Hie real world is not a laboratory, so this technique is not recommended as a standard mitigation procedure. Carbon dioxide and other extinguishing agents (other than those mentioned previously) contain molecules of oxygen that will react with the burning sodium.
Large volumes of burning sodium may be impossible to extinguish, so evacuation and protection of exposures may be the only safe procedure to follow.
FIRST AID
Remove victims of sodium inhalation to fresh air and keep warm and quiet. Administer mouth-to-mouth resuscitation if the victim has difficulty breathing or has stopped breathing altogether; however, such action may result in exposure of the first-aid giver to the chemical in the victim’s lungs or vomit. Get medical attention immediately.
If sodium has contacted the victim’s eyes, flush the eyes for at least 15 minutes, raising the eyelids often during this procedure. Immediate medical attention is vital.
For contact w7ith the victim’s skin, remove all contaminated clothing, carefully brushing off all particles of sodium. Wash the affected areas of the victim’s body with large amounts of water. Seek medical attention immediately.
In the unlikely event of ingestion of sodium, have a conscious victim drink large amounts of water. Do not induce vomiting, and never tryto make an unconscious person drink anything. Get immediate medical help.
PROTECTIVE CLOTHING AND EQUIPMENT
When handling metallic sodium, ensure that all tools and equipment used are compatible with the material. All safety equipment and clothing must effectively keep sodium from contact w ith the eyes or skin. Personnel must wear rubber gloves and boots, goggles and face shields, and impervious clothing. Use total encapsulating suits and positive-pressure, self-contained breathing apparatus for protection from dust and fumes.
If any moisture is present on the protective clothing and sodium contacts the moisture, the clothing will not offer protection from the violent reaction that will occur. Similarly, if burning sodium contacts protective clothing, it will burn through quite rapidly. Take care never to contact the metal itself.
