CHEMICAL DATA NOTEBOOK SERIES #39 Toluene
TOLUENE IS a flammable, irritating, narcotic, colorless liquid with a pungent, pleasant, benzene-like odor. It is used primarily as a solvent, but it is also used to make dyes and explosives and is an additive to fuels that are mixtures of hydrocarbons, such as aviation gasoline and high-octane blending stocks. It is a common solvent for coatings, glues, gums, lacquers, oils, paints, plastics, resins, and rubber and is used to make some organic chemicals. It is described as aromatic because it is a derivative of benzene. Its molecular formula is C6H5CH3 but may sometimes be shortened to C7H8, which will be confusing. Toluene’s structural formula is
The benzene “ring” is always portrayed as it is in the above structure, but understand that this is a shorthand way of drawing the structure. There is a carbon at each apex of the hexagon (thus the C6 portion of the formula), and one hydrogen is connected to each carbon in the ring except for where the methyl, or —CH3 radical, is attached (thus the H5 portion of the structure). The molecular formula for benzene is C6H6.
Toluene has a flash point of 40°F, a flammable range of 1.2% to 7.1%, and an ignition temperature of 997°F. It has a specific gravity of 0.87, a molecular weight of 92, and a vapor density of 3.18. It has a freezing point of-139°F, a boiling point of 231-1°F, and is very slightly soluble in water.
The major hazard of toluene is its flammability. Although it has a relatively narrow flammable range (less than 6%), its use in so many glues and paints makes it hazardous because of its popularity. As a solvent for glues or mastics, it is relatively easy to have vapors of toluene within the flammable range because it will be evaporating from a mixture containing a relatively small amount of the product.
The vapors of toluene are relatively heavy and will tend to gather in low spots or confined areas. This presents not only an explosion hazard but the dangers of vapor inhalation. High concentrations of vapors can irritate the eyes, mucous membranes, and respiratory system. Inhalation of high concentrations of toluene vapors can cause dizziness, drowsiness, headaches, weakness, and confusion and can lead to narcosis, depression of the central nervous system, and possibly death. Its TLV-TWA is 100 ppm and its STEL is 130 ppm.
Contact with the skin will cause irritation and, if the contact is prolonged or repeated, inflammation. Some amount of toluene will be absorbed through the skin. Contact with the eyes will cause irritation and injury to the cornea. Ingestion of toluene, in significant amounts, will produce symptoms including diarrhea, vomiting, slowed respiration, and possibly death.
Toluene is related to benzene in that the benzene ring is a major part of its structure; thus toluene can be considered a derivative of benzene. Toluene is being scrutinized carefully to determine whether it has any of the carcinogenic properties of benzene.
Toluene is a stable chemical that does not react with many other chemicals. However, being a flammable liquid and therefore a fuel (a fuel is defined as anything that will burn), it is incompatible with all strong oxidizers, particularly with a mixture of nitric and sulfuric acids or in the presence of nitrogen tetroxide or silver perchlorate. In the presence of strong oxidizing agents, all fuels that are normally flammable become explosive, since there will be an intimate mixture of the fuel with the oxygen (or other oxidizer) needed for its combustion.
A vapor density of 3-18 means that the vapors of toluene are 3.18 times heavier than air and that any vapors released in a spill or leak will “hang together” and travel great distances. Vapors are fluid in nature —they will flow from high places to low and if not diluted by a breeze will travel until they become “trapped” in low areas or confined spaces. Such an occurrence will create a double hazard. Although the flammable range of toluene is relatively narrow, the vapors will be ignitable somewhere near the edge of the accumulated vapors. If a suitable ignition source (one with enough energy to raise the temperature of some of the toluene vapors to 997°F) is present and the vapors are within the flammable range, the ignition will be explosive in nature. The second hazard is possible asphyxiation. In any low-lying areas or confined spaces, the relatively heavy vapors of toluene will displace the air, depriving exposed people of the oxygen they need for respiration.
Any toluene vapors generated from a spill or released by a leak necessitate consideration of evacuation downwind. As in the case of any flammable liquid, you must approach the incident from upwind and eliminate all existing and potential ignition sources.
If leaks in containers are not very large or are located in easy-to-reach areas, plugging and/or patching techniques may contain the liquid. In the case of small leaks caused by punctures, driving an oversized wood plug into the hole will control it. Placing a compatible material over the hole and tightening it against the container with ropes, large rubber bands, or chains will also control it. However, in every case you must use nonsparking tools and question the wisdom of using chains around a metal tank car.
Absorption—the penetration of one substance into the inner structure of another substance. Contrast with adsorption.
Adsorption—the adherence of one substance to the outer surface of another substance. Contrast with absorption.
Aeration—a process by which air is introduced into a liquid either by bubbling the air through it or by spraying the liquid into the air at normal pressures.
Air stripping—a process by which a material is pumped through an air chamber or sprayed into the open air at high pressure to remove contaminants.
Carcinogenic&emdash;capable of causing cancer.
Combustible liquid&emdash;a liquid with a flash point of 100°F or higher.
Flammable liquid&emdash;a liquid with a flash point of less than 100°F.
Flash point&emdash;the minimum temperature of a liquid at which it produces vapors sufficient to form an ignitable mixture with the air at the surface of the liquid or container. Be careful of published flash points because of the possibility of different values using different methods. Check several references and use the lowest value reported.
Sparging—a process by which air or other gas is bubbled through a liquid, solid, or gas to remove a contaminant.
Vapor density—the relative density of a vapor or gas as compared with clean, dry air.
Volatile — the capability of evaporating rapidly at normal temperatures and pressures.
After notifying the proper environmental authorities of the release, direct mitigation techniques toward keeping the surface area of the spill to a minimum to lessen the generation of vapors. The larger the surface area of the spill (that is, the larger the surface of the liquid exposed to the atmosphere), the greater the amount of vapors produced. Therefore, to lessen the explosion or asphyxiation hazard downwind, emergency responders may find it necessary to confine the liquid’s movement. Constructing a containment pond by diking around the spill with soil, sand, clay, or other materials will confine the liquid.
If digging equipment is available (and, of course, the manpower is available to operate it and conditions are safe for it), digging a pit may contain the liquid. Digging trenches can lead the liquid from the spill area to the completed pit. A containment pit may be more desirable than a containment pond because the pit may have a smaller surface area when filled. This is helpful not only from an evaporation standpoint, but also because it may be easier to cover with a tarp or sheets of compatible material to virtually eliminate the generation of vapors. The smaller surface area is also easier to blanket with foam, which may be effective in reducing the production of toluene vapors. You may have to reapply foam several times as it breaks down over the liquid. Foam also adds to the volume of the liquid being contained.
Antisal la benzene, methyl— methacide methane, phenylmethyl benzene
methyl benzol NCI-C07272 phenylmethane tolu-sol toluol
IDENTIFICATION NUMBERS AND RATINGS
(Chemical Abstract Services)
(Standard Transportation Commodity Code)
(Registry of Toxic Effects of Chemical Substances)
(United Nations/North America)
(Chemical Hazard Response Information System)
(Resource Conservation and Recovery Act)
(U.S. Department of Transportation)
(International Maritime Organization)
3.2, flammable liquid
When constructing the containment pond or pit, use nonsparking tools and take care when operating any equipment downwind, since the engine or motor on the machinery might ignite the vapors. Once you collect and contain the toluene, properly trained, educated, and equipped nonemergency personnel can remove it using equipment and techniques that protect them from direct contact and eliminate ignition sources.
Removal can be by pumping or vacuuming the product into secure containers for transporting from the scene. Whether or not the product can be salvaged is a decision for someone other than the emergency responders to make.
Once all the liquid that can be easily removed has been taken away, any residual toluene can be absorbed by applying cement powder, clay, fly ash, peat moss, sand, soil, straw, or any other sorbent either naturally or commercially available. Once the toluene is absorbed onto the sorbent, treat the mixture just as you would the toluene, since it can evaporate from the sorbent and cause an explosive mixture with the air. This absorbed material must be disposed of in accordance with federal, state, and local regulations.
Toluene (or any other hazardous material, for that matter) must be kept from sewer systems and waterways. Damming catch basins and manholes will prevent the liquid from entering sewers. If any material does enter the sewer system, notify the sewage treatment plant immediately. Also, there will be a danger of explosion all along the route of the sewer containing the toluene, especially near catch basins and manholes downgrade from the point of entry. It may be necessary to block off streets and warn residents along the sewer route.
If toluene enters a waterway, it will float on the surface and very slowly dissolve in the water. All downstream users of the water must be notified immediately. The dangers to the population using the contaminated waterway for drinking water are obvious. However, industrial users of the water will also be at risk—those who use the water to cool hot processes and equipment. Any undissolved toluene floating on the surface taken into the industrial process could be disastrous, since most manufacturing processes are at temperatures higher than the flash point of toluene. Contact with hot equipment or surfaces will cause very rapid evaporation of the product and put a tremendous volume of explosive flammable vapors into the air.
Since most water intakes for any use are below the waterway’s surface, the floating toluene may not enter the operation through those intakes. However, some water that contains dissolved product will enter. Heating water containing dissolved toluene forces the toluene out of solution and causes it to vaporize rapidly. Even though the concentration of toluene in water may be low, the great volume of water used may generate enough vapors to produce a devastating explosion.
Diking along the banks and diverting the liquid to a containment area can prevent entry to waterways. If the product does enter the waterway, damming the waterway itself will hold back the contaminated water or divert it into a low-lying area until it can be treated. Aeration techniques can purify water with dissolved toluene in it—that is, the water sprayed into the air under pressure will remove the contaminant. Alternately, air stripping or sparging techniques will remove the dissolved toluene.
Remove any undissolved toluene by adding straw or other absorbent material that floats on water. Capture any product floating on the water by this method. Floating oil booms increase the efficiency of the straw by keeping it in place. With its low lower flammable limit of 1.2%, the flammable range of toluene will be reached rather quickly.
If the toluene vapors are ignited, whether at the immediate release scene or at some distance downwind (and flashed back to the spill), a flammable liquid fire now exists. This is the type of hazardous-materials incident involving fire most familiar to firefighters. Water can be a fire extinguishing agent if delivered in a manner consistent with the training firefighters receive for fighting flammable liquid fires. Many references say water may be ineffective in fighting this type of fire, but new nozzle technology and delivery techniques allow trained firefighters to use water in flammable liquid fires. Foam can serve as both an extinguishing agent and an agent to blanket the liquid’s surface to prevent (or slow down) the generation of explosive vapors. Remember that foam or water will add to the volume of liquid in the containment pond or pit. (Consider the amount of additional volume the confinement techniques can hold in the mitigation decision.) Carbon dioxide or dry chemical may be effective on small or confined fires.
Where impinging flame or radiated heat threatens a container of toluene (or any other liquid or gas), danger of container failure exists. Firefighters must never allow themselves to be caught between the fire and such containers. Cool all containers exposed to heat or flame by applying water from as far away as possible or with unmanned appliances. If the containers cannot be cooled, withdrawal and evacuation are necessary in a radius of from 500 to 2,000 feet, depending on the size of the container. If the container fails, it will do so explosively, spewing flaming liquid in all directions.
The final combustion products of toluene are water, carbon, carbon dioxide, and carbon monoxide. All emergency response personnel should wear respiratory protection.
Remove victims of inhalation to fresh air. If the victim has stopped breathing or breathing has become difficult, administer artificial respiration. (Mouthto-mouth resuscitation may expose the provider of first aid to the material in the victim’s mouth or to vomit.) Provide medical attention immediately.
Do not induce vomiting for a victim of ingestion. Call for immediate medical attention while making sure the victim is warm and comfortable.
In case of skin contact, remove all contaminated clothing and wash all affected body areas with large amounts of water. Seek medical attention if irritation of the skin persists after washing.
In case of eye contact, flush the eyes immediately with large amounts of water for 15 minutes, occasionally lifting the eyelids. Provide medical attention.
PROTECTIVE EQUIPMENT AND CLOTHING
All equipment used and clothing worn should prevent contact with the eyes, skin, and respiratory system. This includes face shields, splash-proof goggles, rubber boots, rubber gloves, and other clothing that the manufacturer claims is impervious to toluene, which may include fluorine/chloroprene, nitrile-butadiene rubber, Saranex, and Viton. Some rubber compounds are dissolved by toluene, so consult the manufacturer’s specifications before using.
For respiratory protection, use a positive-pressure, self-contained breathing apparatus. Some references suggest using a gas mask equipped with an organic vapor cannister or an organic vapor cartridge respirator with full face pieces within the safety use limitations of those devices. However, unless you know the concentration of toluene vapor, it may not be worth the risk to use a device with the ability to remove those vapors if the vapors are higher than specifications of the device.