Sulfur dioxide

Описание

Sulfur dioxide is a compound formed by the combination of the elements sulfur and oxygen. On a weight basis, the proportion of the elements is about I part sulfur to I part oxygen, or more exactly, 50.05 percent to 49.95 percent, respectively. At standard conditions of temperature and pressure, sulfur dioxide is a colorless gas with a characteristic pungent odor. It may be cooled and compressed to a colorless liquid, which, at one atmosphere pressure, boils at 14°F (10.0°C) and freezes at -104.6°F (-75.9°C). Sulfur dioxide liquid is heavier than water, and has a specific gravity of 1.436 at 32°F (0°C). As a gas, it is more than twice as heavy as air; its relative density is 2.2638 at atmospheric pressure and 32°F (0°C).
Sulfur dioxide is not flammable or explosive in either the gaseous or liquid state. It is a relatively stable chemical. Temperatures above 3632°F (2000°C) are required to bring about detectable decomposition of sulfur dioxide. Dry sulfur dioxide (less than 100 ppm water) is not corrosive to ordinary metals. However, in the presence of even small amounts of water, sulfur dioxide becomes corrosive to most metals, with exceptions including lead, Type 316 stainless steel, and certain alloys. Glass and certain plastics are also resistant to moist sulfur dioxide.

Химические свойства

Sulfur dioxide,S02, also known as sulfurous acid anhydride,is a toxic, irritating, colorless gas. It is soluble in water, alcohol, and ether, and boils at -10 °C. Sulfur dioxide is used as a chemical intermediate, in artificial ice, in paper pulping,in ore refining,and as a solvent.

sulfur dioxide lewis structure

Физические свойства

Colorless gas; pungent suffocating odor; gas density 2.927 g/L at 20°C; heavier than air, vapor density 2.263 (air=1); condenses to a colorless liquid at -10°C; density of liquid SO₂ 1.434 g/mL; freezes at -72.7°C; critical temperature 157.65°C; critical pressure 77.78 atm; critical volume 122 cc/g; dielectric constant 17.27 at -16.5°C; dissolves in water forming sulfurous acid, solubility 22.97 g and 11.58 g/100mL water at 0° and 20°C, respectively, under atmospheric pressure; very soluble in acetone, methyl isobutyl ketone, acetic acid, and alcohol; soluble in sulfuric acid; liquid SO₂ slightly miscible in water.

Вхождение

Reported found in orange juice, grapefruit juice, onion, boiled and cooked beef,starfruit and weinbrand brandy.

Использование

Sulfur Dioxide is a preservative, being a gas that dissolves in water to yield sulfurous acid. sulfite salts, such as sodium and potassium sulfite, sodium and potassium bisulfite, and sodium and potassium metabisulfite, yield free sulfurous acid at low ph. sulfur dioxide pre- vents the discoloration of foods by combining with the sugars and enzymes. it also inhibits bacterial growth. it is used in beverages, cherries, wines, and fruits.

Подготовка

Sulfur dioxide usually is prepared industrially by the burning in air or oxygen of sulfur or such compounds of sulfur as iron pyrite or copper pyrite. Large quantities of sulfur dioxide are formed in the combustion of sulfur-containing fuels. In the laboratory, the gas may be prepared by reducing sulfuric acid (H2SO4) to sulfurous acid (H2SO3), which decomposes into water and sulfur dioxide, or by treating sulfites (salts of sulfurous acid) with strong acids, such as hydrochloric acid, again forming sulfurous acid.

Методы производства

Sulfur dioxide can be made by burning sulfur, or by roasting sulfide ores such as pyrites, sphalerite, and cinnabar.

Реакции воздуха и воды

Dissolves in water to form sulfurous acid, a corrosive liquid. Moist Sulfur dioxide is very corrosive due to the slow formation of sulfuric acid [Handling Chemicals Safely 1980 p. 876].

Профиль реактивности

Sulfur dioxide is acidic. Reacts exothermically with bases such as amines, amides, metal oxides, and hydroxides. Frequently used as a reducing agent although Sulfur dioxide is not a powerful one. Acts as a reducing bleach to decolorize many materials. Can act as an oxidizing agent. Supports combustion of powdered aluminum [Mellor 5:209-212 1946-47]. Reacts explosively with fluorine [Mellor 2:1 1946-47]. Supports burning of manganese [Mellor 12:187 1946-47]. Readily liquefied by compression. Contact between the liquid and water may result in vigorous or violent boiling and extremely rapid vaporization. If the water is hot an explosion may occur. Pressures may build to dangerous levels if the liquid contacts water in a closed container [Handling Chemicals Safely 1980]. Supports incandescent combustion of monocesium acetylide, monopotassium acetylide, cesium oxide, iron(II) oxide, tin oxide, and lead oxide [Mellor]. Ethylene oxide and SO2 can react violently in pyridine solution with pressurization if ethylene oxide is in excess (Nolan, 1983, Case History 51).

Опасность

Toxic by inhalation, strong irritant to eyes and mucous membranes, especially under pressure. Dangerous air contaminant and constituent of smog. Not permitted in meats and other sources of vitamin B1. U.S. atmospheric standard 0.140 ppm. Pulmonary function inhibitor and lower respiratory tract irritant. Questionable carcinogen.

Угроза здоровью

Exposures to sulfur dioxide cause adverse health effects to users and occupational workers. The gaseous sulfur dioxide is particularly irritating to the mucous membranes of the upper respiratory tract. Chronic exposure to sulfur dioxide produces dryness of the throat, cough, rhinitis, conjunctivitis, corneal burns, and corneal opacity. Acute exposure to high concentrations of sulfur dioxide may also result in death due to asphyxia. By contrast, chronic exposures to sulfur dioxide lead to nasopharyngitis, fatigue, and disturbances of the pulmonary function. Animals exposed to chronic doses of sulfur dioxide have shown thickening of the mucous layer in the trachea and also hypertrophy of goblet cells and mucous glands resembling the pathology of chronic bronchitis. It has been found that penetration of sulfur dioxide into the lungs is greater during mouth breathing than during nose breathing. In fact, an increase in the fl ow rate of the gas would markedly increase the penetration. Human subjects exposed for very brief periods to sulfur dioxide also showed alterations in pulmonary mechanics. More information on the adverse effects of sulfur dioxide and the manner of its potentiation in association with other chemicals may be found in literature.

Пожароопасность

Containers may explode in heat of fire or they may rupture and release irritating toxic Sulfur dioxide. Sulfur dioxide has explosive properties when Sulfur dioxide comes in contact with sodium hydride; potassium chlorate at elevated temperatures; ethanol; ether; zinc ethylsulfurinate at very cool temperatures (-15C); fluorine; chlorine trifluoride and chlorates. Sulfur dioxide will react with water or steam to produce toxic and corrosive fumes. When the liquid is heated Sulfur dioxide may release irritating, toxic Sulfur dioxide gas. Avoid ammonia, monocesium or monopotassium acetylide; dicesium monoxide; iron (II) oxide; tin oxide; lead (IV) oxide; chromium; manganese; molten sodium, powder aluminum and rubidium. Sulfur dioxide has explosive properties when Sulfur dioxide comes in contact with sodium hydride; potassium chlorate at elevated temperatures; ethanol; ether; zinc ethylsulfurinate at very cool temperatures (-15C); fluorine; chlorine trifluoride and chlorates. Sulfur dioxide will react with water or steam to produce toxic and corrosive fumes. Hazardous polymerization may not occur.

Воспламеняемость и взрывоопасность

Sulfur dioxide is a noncombustible substance (NFPA rating = 0).

Фармацевтические приложения

Sulfur dioxide is used as an antioxidant for pharmaceutical injections. It is also used as a preservative and antioxidant in the food and cosmetics industries.

Использование в материалах

Service conditions must be defined to properly specifY materials of construction for handling sulfur dioxide. It is customary, however, to use carbon steel for dry sulfur dioxide at ambient temperatures. Reference should be made to the latest edition of the ASME Code, Section VIlI, Division I for vessels, and to the latest edition of ANSI/ASME 831.3, Chemical Plant and Petroleum Refinery Piping for piping specifications.
Moist sulfur dioxide is corrosive to carbon steel; therefore, other materials of construction have to be considered in this case. A source of data on the corrosivity of sulfur dioxide to various materials is the Corrosion Data Survey, published by the National Association of Corrosion Engineers; suppliers of liquid sulfur dioxide are another source.

Профиль безопасности

A poison gas. Experimental reproductive effects. Human mutation data reported. Human systemic effects by inhalation: pulmonary vascular resistance, respiratory depression, and other pulmonary changes. Questionable carcinogen with experimental tumorigenic and teratogenic data. It chiefly affects the upper respiratory tract and the bronchi. It may cause edema of the lungs or glottis, and can produce respiratory paralysis. A corrosive irritant to eyes, skin, and mucous membranes. This material is so irritating that it provides its own warning of toxic concentration. Levels of 400-500 ppm are immediately dangerous to life. Its toxicity is comparable to that of hydrogen chloride. However, less than fatal concentration can be borne for fair periods of time with no apparent permanent damage. It is a common air contaminant. A nonflammable gas. It reacts violently with acrolein, Al, CsHC2, Cs2O, chlorates, ClF3, Cr, FeO, F2, Mn, KHC2, KClO3, Rb2C2, Na, Na2C2, SNOx diaminolithiumacetylene carbide. Will react with water or steam to produce toxic and corrosive fumes. Incompatible with halogens or interhalogens, lithium nitrate, metal acetylides, metal oxides, metals, polymeric tubing, potassium chlorate, sodium hydride.

Безопасность

Sulfur dioxide is used in food and pharmaceutical products. However, in large amounts, sulfur dioxide gas is highly irritant to the eyes, skin, and mucous membranes. Inhalation can lead to severe irritation of the respiratory tract. Direct contact with the liquid form may cause frostbite. Sulfur dioxide and sulfites may also cause allergic reactions and asthma.

Возможный контакт

Sulfur dioxide is used in the manufacture of sodium sulfite, sulfuric acid; sulfuryl chloride; thionyl chloride; organic sulfonates; disinfectants, fumigants, glass, wine, ice, industrial and edible protein; and vapor pressure thermometers. It is also used in the bleaching of beet sugar, flour, fruit, gelatin, glue, grain, oil, straw, textiles, wicker ware; wood pulp; and wool; in the tanning of leather; in brewing and preserving; and in the refrigeration industry. Exposure may also occur in various other industrial processes as it is a by-product of ore smelting, coal and fuel oil combustion; paper manufacturing and petroleum refining.

Канцерогенность

Sulfur dioxide may act as a cancer promoter. The mortality of arsenic smelter workers was higher when they had also been exposed to sulfur dioxide. In addition, rats exposed to 3.5 or 10 ppm of sulfur dioxide developed squamous cell carcinomas from inhalation of benzo[a]pyrene, but neither compound alone produced carcinomas under the conditions of this experiment.

хранилище

Sulfur dioxide is noncorrosive and stable when dry. It is usually stored under pressure in cylinders, and should be kept in a cool, dry, well-ventilated area, away from flammable materials.

Перевозки

UN1079 Sulfur dioxide, Hazard Class: 2.3; Labels: 2.3-Poisonous gas, 8-Corrosive material, Inhalation Hazard Zone C. Cylinders must be transported in a secure upright position, in a well-ventilated truck. Protect cylinder and labels from physical damage. The owner of the compressed gas cylinder is the only entity allowed by federal law (49CFR) to transport and refill them. It is a violation of transportation regulations to refill compressed gas cylinders without the express written permission of the owner

Методы очистки

Dry it by bubbling through conc H2SO4 and by passage over P2O5, then through a glass-wool plug. Freeze it with liquid air and pump it to a high vacuum to remove dissolved gases. It is easily liquefied by compression (2.5atmospheres at 15o), or by passing it through a glass spiral column in a freezing mixture of ice and salt. It is a colourless liquid with a density of 1.434 at 0o, which on rapid evaporation forms a snow white solid. It could be used as a solvent in certain reactions. HARMFUL SUFFOCATING VAPOURS.

Несовместимости

Sulfur dioxide reacts vigorously with strong alkalis and oxidizing agents. The moist gas corrodes most metals. Sulfur dioxide is incompatible with chlorates, fluorine, interhalogens, powdered metals, metal oxides, metal acetylides, sodium hydroxide, and diethyl zinc. It is also incompatible with thiamine and gelatin.

Утилизация отходов

Return refillable compressed gas cylinders to supplier. Pass into soda ash solution, then add calcium hypochlorite; neutralize and flush to sewer with water (A-38).

Меры предосторожности

Occupational workers should be careful at workplaces because exposure to sulfur dioxide occurs from breathing it in the air. It affects the lungs and at high levels may result in burning of the nose and throat, breathing diffi culties, and severe airway obstructions.

Регуляторный статус

GRAS listed. Accepted for use as a food additive in Europe. Included in the FDA Inactive Ingredients Database (IV infusions; injection solutions). Included in the Canadian List of Acceptable Non-medicinal Ingredients.