Sulfur dioxideSulfur Dioxide (SO2) is a colourless gas,

belonging to the family of gases called sulfur oxides (SOx). It reacts on the surface of a variety of airborne solid particles, is soluble in water and can be oxidized within airborne water droplets.

Natural SourcesNatural sources of sulfur dioxide include releases

from volcanoes, oceans, biological decay and forest fires. The most important man-made sources of sulfur dioxide are fossil fuel combustion, smelting, manufacture of sulfuric acid, conversion of wood pulp to paper, incineration of refuse and production of elemental sulfur. Coal burning is the single largest man-made source of sulfur dioxide accounting for about 50% of annual global emissions, with oil burning accounting for a further 25 to 30%

Health EffectsThe major health concerns associated with

exposure to high concentrations of sulfur dioxide include effects on breathing, respiratory illness, alterations in pulmonary defenses, and aggravation of existing cardiovascular disease. In the atmosphere, sulfur dioxide mixes with water vapour producing sulfuric acid. This acidic pollution can be transported by wind over many hundreds of miles, and deposited as acid rain.

A method and apparatus for burning fossil fuels containing a significant sulfur content which removes a significant portion of the sulfur oxides released to the atmosphere. The invention is characterized by the dispersal of a molten metal into a combustion chamber for intimate contact with the combustion products to combine with the sulfur compounds produced by the combustion reaction. The metal sulfide may then be collected and refined for recirculation and the sulfur dioxides collected for use or sale

Sulfur dioxide is a colourless gas with a pungent, irritating odour similar to burning sulfur. It is a colourless liquid below -10 deg C. Sulfur dioxide will not burn. It is a COMPRESSED GAS. Cylinders or tanks may rupture and explode if heated. It is VERY TOXIC and may be fatal if inhaled. Sulfur dioxide is also extremely irritating to eyes and respiratory tract. It causes lung injury and these effects

may be delayed. It may also cause frostbite.

Its major use is a captive intermediate in the production of sulfuric acid. In the pulp and paper industry, sulfur dioxide is used to produce other chemicals such as chlorine dioxide and sodium hyposulfite and is also used in the bleaching of pulp. In food processing, sulfur dioxide is used for fumigating, preserving, bleaching and steeping. It

is also used to reduce residual chlorine in potable water, treated sewage and industrial effluent, as an oxygen scavenger, a selective extraction solvent and as a catalyst in chemical processes. In the presence of a catalyst (e.g. nitrogen compounds), sulfur dioxide can be oxidized to sulfuric acid. Occurs as a by-product during the burning (combustion) of sulfur containing organic compounds (e.g. coal). A common component of air pollution, it is a major contributor to acid rain.

Other questions !What should I know about the composition and purity of sulfur dioxide?

Available as a liquefied compressed gas. The anhydrous grade has a minimum purity of 99.98%.

With so many names for sulfur dioxide, is there a unique identifier for this chemical?

Its CAS Registry Number is 7446-09-5. This number is assigned by the Chemical Abstracts Service (CAS) in the United States and is used as a unique identifier number world-wide.

Contact with sulfur dioxide !What happens when sulfur dioxide comes into contact with my

skin? The gas will react with moisture on the skin and cause irritation.

Liquid SO2 may cause burns due to freezing. Symptoms of mild frostbite include numbness, prickling and itching in the affected area. The skin may become white or yellow. Blistering, necrosis (dead skin) and gangrene may develop in severe cases.

Can sulfur dioxide hurt my eyes? Volunteers exposed to 5.4 ppm SO2 experienced mild irritation, while

9.1 ppm cause moderate to severe irritation. At 8-12 ppm, smarting of the eyes and lachrymation (tears) began. There is strong irritation at 50 ppm. In severe cases, (very high concentrations in confined spaces), SO2 has caused temporary corneal burns. Liquid SO2 can burn the eye and permanently affect vision. Injury from contact with liquid SO2 may not be immediately noticed by the victim because SO2 damages the nerves of the eye. Any eye contact should be treated as very serious. .

What happens if sulfur dioxide is accidentally swallowed (enters the digestive system)?

Not applicable. Ingestion of gaseous or liquid SO2 is highly unlikely.

Will sulfur dioxide cause cancer? Several epidemiological studies have examined the

possibility that sulfur dioxide may cause cancers such as lung cancer, stomach cancer or brain tumours. In all of the studies, there were uncontrolled confounding factors, such as concurrent exposure to other chemicals. The International Agency for Cancer (IARC) has reviewed these studies and concluded there is inadequate evidence for carcinogenicity in humans. However, there is limited evidence of carcinogenicity in animals. Their overall evaluation is that sulfur dioxide is not classifiable as to its carcinogenicity to humans (Group 3).

What are the fire and explosion dangers associated with sulfur dioxide?

Non-flammable gas. However, heat from a surrounding fire can rupture cylinders, causing a dangerous explosion and the release of toxic sulfur dioxide gas. Cylinders have fusible metal plugs which melt at 165 deg F, releasing SO2.

Is sulfur dioxide stable when exposed to air, moisture, or heat? SO2 is extremely stable to heat, even up to 2000 deg C. Complex

reactions of SO2 occur in the atmosphere. SO2 gas and its aqueous forms are oxidized to sulfuric and sulfates which contribute to air pollution.

Are there any conditions to avoid when sing sulfur dioxide? Moisture.

Is the odour of sulfur dioxide reliable as a warning property? Not reliable

What can be done to control hazardous conditions?

Engineering methods to control hazardous conditions are preferred. Methods include mechanical ventilation (dilution and local exhaust), process or personnel enclosure, control of process conditions, and process modification (e.g. substitution of a less hazardous material). Administrative controls and personal protective equipment may also be required.

Use a corrosion-resistant ventilation system separate from other exhaust ventilation systems. Exhaust directly to the outside. Treatment of exhaust gases to prevent environmental contamination may be required. Supply sufficient replacement air to make up for air removed by exhaust systems.