Sulfuric Acid (and Oleum)
FEATURES
HAZARDOUS MATERIALS
Chemical Data Notebook Series:
This is the first in an ongoing series of articles that will attempt to cover every facet of between 100 and 150 chemicals which represent 95% of the volume of chemicals transported and used in this country. The articles will describe the physcial and chemical properties, as well as the hazards presented by each substance. Suggestions on and safety precautions in responding to and mitigating an incident involving each chemical will also be offered.
It is hoped that this series will assist fire departments in preparing their own hazardous material reference guide. On page 37 is a blank hazardous materials data sheet. This sheet should be taken out, copied, and the information filled in after studying the chemical. By saving each data sheet in a loose-leaf binder, you won’t have to search through several reference sources to get the needed information on a particular chemical.
sulfuric acid (also spelled sulphuric acid) is the highest volume chemical produced in the world, and is used in more chemical reactions and industrial processes than any other chemical. There is a direct correlation between the industrialization (or “development”) of a nation and the amount of sulfuric acid it produces and/or uses.
Sulfuric acid is used in the manufacture of metals, pharmaceuticals, paper, explosives, fertilizers, batteries, cellulose, paint, dyes and pigments, detergents, and glue. It is also used in leather processing and in the production of numerous other chemicals and substances.
The molecular formula for sulfuric acid, H2SO4, indicates that it is a source of the sulfate ion (SO4-2). Having strong corrosive or oxidizing properties, sulfuric acid is the battery acid used in automobile storage batteries and the corrosive material needed to unclog sink drains.
Sulfuric acid is known as oil of vitriol, spirit of vitriol, spirit of sulfur, battery acid, diathonic acid, dipping acid, fertilizer acid, chamber acid, matting acid, brown oil, BOV, vitriol brown oil, hydrogen sulfate, nordhausen acid, and G.E. Mat. D4A2.
APPEARANCE
Sulfuric acid is a liquid whose color may range from water-clear to dark brown. The most common form is at least 98% pure sulfuric acid, but it may be shipped in a concentration considered “more than 100%.” This material is commonly known as oleum, or fuming sulfuric acid.
Oleum is concentrated sulfuric acid with additional sulfur trioxide (SO3) gas dissolved in the acid. When this gas is released, it dissolves the moisture in the air, giving the name “fuming” to this form of sulfuric acid. Other synonyms for oleum include nordhausen acid, disulfuric acid, dithionic acid, and pyrosulfuric acid.
Both sulfuric acid and oleum are non-flammable liquids, but they can cause or support a fire. They can cause a fire by reacting with any of a large number of chemicals, liberating enough heat to ignite ordinary combustibles. They will support a fire by releasing some of the oxygen held in the sulfate ion.
Sulfuric acid has a specific gravity of 1.54 to 1.84 depending on concentration, and is totally soluble in water. It is a relatively stable chemical, but may produce fumes if heated. Oleum has a higher specific gravity of 1.92 to 1.99, and is also totally soluble in water.
Both sulfuric acid and oleum will attack many metals, dissolving them and liberating their own hydrogen, which is highly flammable. The heat liberated during the chemical reaction may be sufficient to ignite the hydrogen, producing an explosion.
Sulfuric acid and oleum are also very reactive with many different chemicals and substances, often causing fire and/or explosions. Especially dangerous is contact with organic material and oxidizers.
Sulfuric acid may boil at temperatures ranging from 518° to 644°F (again, depending on concentration), and freezes at 37.4°F. It has a molecular weight of 98 amu (atomic mass units).
The appearance of oleum can vary from a colorless fuming liquid to a cloudy, or even black fuming liquid. The odor, like that of sulfuric acid, is sharp, penetrating, and choking. Oleum has a high degree of reactivity with many materials, especially organic and other reactive chemicals.
IDENTIFICATION
The Department of Transportation (DOT) requires that the black and white corrosives placard and label be affixed to containers of sulfuric acid and oleum during transportation. The placards show a test tube pouring liquid onto metal on the upper left half, and a hand on the upper right. The United Nations numerical classification for corrosives (“8″) is at the lowest point on the placard. The substance’s specific identification number, a four-digit number proceeded by UN or NA (UN/NA number), is centered on the card.
Oleum or fuming sulfuric acid is identified by UN/NA number 1831, while sulfuric acid is 1830, and spent sulfuric acid is 1832.
The STCC (Standard Transportation Commodity Code) for oleum is 4930030, while sulfuric acid is 4930040, and spent sulfuric acid is 4930032. The STCC does not appear on the placard, but is used on railroads’ shipping documents.
For stationary containers, the National Fire Protection Association recommends the use of its 704 Identification System. In this diamond-shaped system using four quadrants, the left quadrant (colored blue) designates the health hazard, the top (colored red) designates flammability, the right (yellow) designates reactivity, and the bottom (white) will have special information. For sulfuric acid and oleum, the designation is 3-0-2-W.
CONTAINERS
Sulfuric acid is shipped in rail cars, tank trucks, and carboys. Although it may be clearly labeled as a powerful corrosive, it may not be identified as water-reactive; and there will not be any warning on the label indicating that flammable and explosive hydrogen will be generated by the acid contacting many metals.
Oleum is shipped in the same kind of containers as sulfuric acid. It is used mainly in petroleum refining and the manufacture of explosives, dyes, and various chemicals.
HAZARDS
Personal
The hazards of sulfuric acid and oleum are similar. Both are very corrosive to metals, minerals, and human tissue. Both will produce a black char on human skin or wood, as the water is withdrawn from them, leaving mostly carbon behind. If either oleum or concentrated sulfuric acid contact large areas of human skin, death is sure to result from the resulting damage and trauma.
There are very few corrosive materials more dangerous to human life than concentrated sulfuric acid and oleum.
Water reactivity
Sulfuric acid, like oleum, reacts violently with water, liberating tremendous amounts of heat. It is an old adage in the chemistry lab that a student, while preparing a dilute solution of H2SO4, must never add water to the concentrated acid, rather the acid must be added to the water. This is because as a water-reactive material, if water is added to concentrated sulfuric acid, enough heat will be generated to boil the water. If this is done in a container, the water will instantly boil away and concentrated sulfuric acid will be forced from the container. If the concentrated acid is added to water (in small amounts), what will be forced from the container will be very dilute acid, if anything at all comes out.
This obviously presents a problem to the firefighter responding to an incident involving H2SO4. If he must use water on an existing fire, or if he must use water to dilute the acid (an acceptable method of handling a spill), he has to apply the water in flooding amounts, not as a stream. A fog or spray application will not splash the acid about and will absorb any acid fumes released from the liquid. And, of course, any time water is used to dilute a hazardous material, the run-off water must be contained.
PROTECTIVE CLOTHING
In the event of leaks, spills, and other accidental discharges, the techniques for handling incidents involving oleum and sulfuric acid are very similar. In all cases, personnel must avoid contact with these powerful corrosives. When contact is inevitable, the proper safety equipment must be used to prevent contact with the skin or other external organs. Needless to say, ingestion of these materials will cause serious burns and probable death.
Safety clothing includes rubber gloves and boots, acid-resistant goggles and/or face shields, and acid-resistant clothing. Positive pressure self-contained breathing apparatus (SCBA) must be used at all times.
Acid suits and total encapsulating suits may be constructed of nitrile-butadiene, butyl, nitrile, or styrene-butadiene rubber, polyvinyl chloride (PVC), neoprene, chlorinated polyethylene, or Viton. These suits must be decontaminated after they are used, and care taken to contain the cleaning water.
It is always recommended that the encapsulating suits be tested prior to exposure. This can be done by having the suit manufacturer provide you with swatches of material from which the suit was made, and expose these swatches to the most hazardous material you’ll face. Concentrated sulfuric acid and oleum surely fit this description.
Dip a swatch into the acid and leave it there for 15 minutes. Remove the swatch and carefully wash it clean with water. Inspect it for damage. Admittedly this is a severe test, but your life may depend on the suit getting a passing grade.
HANDLING
Once these corrosives have been released from their containers, first responders should never make any attempt to handle the materials. Also, if carboys or bottles of the acids have been damaged, these containers should not be handled unless the proper protective equipment is worn, which, at the very least, includes acid-resistant goggles and face shields, and rubber aprons and gloves.
Whenever possible, let personnel with the most experience in handling these materials move the containers around. That is, wherever it is not necessary for emergency personnel to be involved, such as in cleanup, let others who have more experience do the nonemergency work, such as shippers, consignees, etc.
There are several ways to handle a sulfuric acid and/or oleum incident, including containment, absorption, re-cycling, dilution, neutralization, and removal. Never forget that one of the possible responses to a leak or spill is to do nothing as far as intervening in the incident. Your best response may be to just seal off the area and wait for the experts to arrive. In any case, whether you directly intervene or not, the implementation of evacuation procedures should always be considered.
Containment
Containment techniques, of course, include all actions that will keep the released material from moving to an area where it will cause more problems than the original incident. Even though these techniques appear to be simple, you must keep in mind that you are still dealing with very dangerous substances, and simple containment does not bring the incident to a successful conclusion.
The simplest containment technique for a release of sulfuric acid or oleum on land is to build a dike to surround the material. This dike may be constructed of soil, sand, or other inert materials. Soil may be the choice simply because of its presence. Other inert materials may include sorbents (mentioned later), but if the spill is large, there may not be enough sorbent material readily available to do the job.
Another technique is to dig a pit with trenches leading from the liquid to the pit. Here, the soil removed to make the pit may be used as diking material also.
Be advised that these containment techniques enable the acid to seep into the ground, and this may complicate the removal of all contaminated soil (including diking material), which is necessary under any circumstances.
Containment of dangerous fumes generated by a spill may be effected by the use of a fog stream. This technique will dissolve acid vapors from the air. Also, water may be used to dilute the material; however, whenever water is used, remember the violent reaction that will occur when oleum or concentrated sulfuric acid comes in contact with water. Again, with powerful corrosives like sulfuric acid and oleum, all water that is used in the incident must be contained or otherwise prevented from entering a sewer, stream, or other waterway.
If the acids spill into a waterway, containment is much more difficult, since both materials are soluble in water in all proportions. Total damming of the stream or river is necessary to prevent contamination downstream. However, since this is rarely possible, all users of the water downstream must be notified of the contamination so that they may be able to divert the flow.
Adsorption
The released liquid may be adsorbed with inert materials, such as soil, sand, clay, powdered cement, fly ash or a commercial sorbent. If any of the acid can be removed before adsorption is tried, it will naturally lessen the amount of sorbent required.
Remember, adsorption, like containment, is not the final step in handling the incident. The hazardous material is still present. All you have done is render it immobile by getting it to adhere to the surface of another material. Like the contaminated soil and/or diking material in the containment procedure, the sorbent that holds the acid must now be removed.
Dilution
A third method of handling a spill of these acids is to dilute them with water (remember what happens when water contacts sulfuric acid and/or oleum?). Of course, this means that you will need a very large containment area or pit to hold the diluted acid. You must never allow the dilute solution to enter sewers or waterways, or the contamination that you are trying so hard to prevent will spread. You may have to use water in a volume of 1,000 times the volume (or more) of the spilled material to get the acid to a concentration where it no longer poses a hazard. Then a decision must be made concerning what to do with the dilute solution. Leave this decision to the environmental representative, who will surely have responded to the incident.
Neutralization
Neutralization is a chemical reaction that will change the hazardous chemical to a usually nonhazardous material and water. For acids, there are several neutralization agents that may be used, and they all have drawbacks:
- Sodium hydroxide (caustic soda) or potassium hydroxide (caustic potash), both in a concentrated solution in water, will be the most effective, but they are expensive, and are very hazardous materials themselves.
- Calcium hydroxide (slaked lime) dissolved in water is not as dangerous to use as the sodium and potassium hydroxides, but it is fairly costly and not as effective. All three hydroxides may be used in their dry, solid form, but they are very hazardous in this state and will not mix as rapidly as the solutions will.
- Sodium bicarbonate (baking soda), sodium carbonate (soda ash), and calcium carbonate (crushed limestone) are usually recommended because they are relatively inexpensive (calcium carbonate is the least expensive and the least effective, but works adequately) and they will do the job. With the addition of these materials, there will be visible bubbling and gassing. This is the generation of carbon dioxide, a product of the neutralization process.
In any event, a small sample of the spilled acid should be obtained in a small container, and the chosen neutralizer should be added slowly. This simple experiment will show what will happen when large amounts are added to the spill, and will eliminate any surprises. The use of acid test paper will also indicate the relative amount to be added to the spill.
Once again, the ranking environmental representative should make the decision that the spilled acid has been rendered safe.
Recycling
Recycling is a useful technique if the container holding the acid is leaking in such a way that the released material can be caught in a container and pumped back into the leaking container. This creates a relatively closed system that will keep the material under control until the acid may be off-loaded into another container.
Just be sure that the container catching the leaking acid is resistant to the acid, along with all parts of the pump with which the acid will come into contact.
Removal
The safest procedure for incident responders is for the shipper (or manufacturer, or consignee) to provide another container and equipment to move the acid from its original container. If the acid has spilled and is behind containment dikes, in a pit, or in another container, the shipper would then pump it into a secure container. If the material has been adsorbed, the shipper would then remove all the contaminated sorbent, including all contaminated soil.
The remover of the acid or contaminated sorbent and/or soil should be either the chemical manufacturer, consignee, shipper, or a professional firm that is a recognized expert in the chemical field.
EVACUATION
Depending on the size of the spill, the geographical location, population, the ability to effect one of the emergency responses, and, of course, the weather, evacuation may be necessary for as far as a one-half mile radius and up to two miles downwind.
FIRST AID
In the event the chemical contacted eyes and/or skin, flood the affected area with water for 15 minutes (holding the eyelid open during the washing). For ingestion, large amounts of water must be administered. For inhalation of vapors and fumes, the airway must be maintained and resuscitation measures used. Treat for shock and pulmonary edema. Get medical attention immediately.
DECONTAMINATION
Decontamination of protective clothing should be done so that the run-off water can be contained. The encapsulating suit or other impervious protective clothing should be washed down thoroughly:
- First with clean water,
- Then by a rinsing with a solution of sodium bicarbonate and water,
- Another clean-water rinse,
- A washing with a solution of a mild detergent,
- And a final clean water rinse.
Only the water from the first wash-down needs to be contained.
FINAL CLEANUP
The final cleanup should be carried out by the shipper, the manufacturer, the consignee, or other professional organizations experienced in removal of hazardous materials. This work should be done under the supervision of the proper environmental officials.
In all hazardous material incidents, the fire department and other first responding personnel should limit their activities to emergency procedures only, and not be involved in clean-up and disposal procedures. Leave this work to the “experts.”
