Sulfur dioxide (SO2)
sulfur dioxide
CAS: 7446-09-5
Molecular Formula: O2S
Sulfur dioxide (SO2) - Names and Identifiers
Sulfur dioxide (SO2) - Physico-chemical Properties
| Molecular Formula | O2S |
| Molar Mass | 64.06 |
| Density | 1.25 g/mL at 25 °C (lit.) |
| Melting Point | -73 °C (lit.) |
| Boling Point | -10 °C (lit.) |
| Water Solubility | %H2O: 17.7 (0°C), 11.9 (15°C), 8.5 (25°C), 6.4 (35°C); % other solvents: 25, alcohol; 32, methanol [MER06] |
| Vapor Presure | 1779 mm Hg ( 21 °C) |
| Vapor Density | 2.26 (21 °C, vs air) |
| Appearance | colorless gas |
| Odor | Pungent odor detectable at 0.3 to 5 ppm |
| Exposure Limit | TLV-TWA 2 ppm (～5 mg/m3) (ACGIH),5 ppm (OSHA and MSHA); IDLH 100 ppm(NIOSH). |
| Merck | 13,9061 |
| BRN | 3535237 |
| Stability | Stable. Non-corrosive when dry to common materials except zinc; corrosive when wet. Incompatible with strong reducing or oxidizing agents, moisture, zinc and its alloys. |
| Refractive Index | 1.51 |
| Physical and Chemical Properties | Colorless transparent liquid, irritating odor. boiling point -10 ℃ relative density 1.43(0 ℃) soluble in water, ethanol and ether. Water solubility: 0 deg C for 22.8g/100g;20 deg C for 11.5g/100g;90 deg C for 2.1g/100g. |
| Use | Used as organic solvent and refrigerant, and used to refine a variety of lubricating oil |
Sulfur dioxide (SO2) - Risk and Safety
| Hazard Symbols | T - Toxic |
| Risk Codes | R23 - Toxic by inhalation R34 - Causes burns |
| Safety Description | S9 - Keep container in a well-ventilated place. S26 - In case of contact with eyes, rinse immediately with plenty of water and seek medical advice. S36/37/39 - Wear suitable protective clothing, gloves and eye/face protection. S45 - In case of accident or if you feel unwell, seek medical advice immediately (show the label whenever possible.) |
| UN IDs | UN 2037 2.3 |
| WGK Germany | 1 |
| RTECS | WS4550000 |
| FLUKA BRAND F CODES | 4.5-31 |
| Hazard Class | 2.3 |
| Toxicity | LC50 inhal (rat) 2520 ppm (6590 mg/m3; 1 h) LCLO inhal (human) 1000 ppm (2600 mg/m3; 10 min) PEL (OSHA) 5 ppm (13 mg/m3) TLV-TWA (ACGIH) 2 ppm (5.2 mg/m3) STEL (ACGIH) 5 ppm (13 mg/m3) |
Sulfur dioxide (SO2) - Upstream Downstream Industry
Sulfur dioxide (SO2) - Nature
Open Data Verified Data
It is a colorless gas at room temperature and has strong irritating and asphyxiating odor. Its liquid relative density 1. 436, melting point -76.1 ℃, boiling point -10 ℃. Soluble in water and ethanol. Sulfurous acid rapidly releases sulfur dioxide upon heating. Non-combustible. In case of high fever, the internal pressure of the container increases, and there is a risk of cracking and explosion.
Last Update：2025-06-10 22:55:16
Sulfur dioxide (SO2) - Preparation Method
Open Data Verified Data
The tail gas of sulfuric acid plant is absorbed by ammonia water, and the absorption liquid contains ammonium sulfite and ammonium bisulfite. The high concentration of S02 gas can be released by decomposition with sulfuric acid, and the liquid product is formed by drying, compression, separation and cooling. Sulfur and pure oxygen can also be burned in a sulfur incinerator to generate a high concentration of S02 gas, which is dried, compressed and condensed into liquid S02.
Last Update：2025-06-10 22:55:16
Sulfur dioxide (SO2) - Application
Open Data Verified Data
sulfur dioxide is a reducing bleaching agent that is allowed to be used in China. It is suitable for the preservation of alcohol and dried fruits, and has a bleaching effect on food. It has a strong inhibitory effect on the oxidase in plant food and can resist the invasion of microorganisms. China's provisions can be used for wine and fruit wine, the maximum use of 0. 25g/kg, residues should not exceed 0. 05g/kg.
Last Update：2025-08-19 16:24:40
Sulfur dioxide (SO2) - Safety
Open Data Verified Data
rats inhaled (1H) LCsa:6600mg/m3.ADI 0-70mg/kg (calculated as S02, total ADI including S02 and sulfite; FAO/WHO,2001). It has a strong stimulating effect on the mucosa of eyes and respiratory tract. When the concentration of S02 in the air reaches 0. 04% ~ 05%, people will be poisoned. Store in a cool, ventilated warehouse. Keep away from fire and heat source. Storage temperature should not exceed 30 ℃. It should be stored separately from flammable materials, oxidizing agents, reducing agents and edible chemicals, and should not be mixed.
Last Update：2025-06-10 22:55:16
Sulfur dioxide (SO2) - Reference Information
| FEMA | 3039 | SULFUR DIOXIDE |
| olfactory Threshold | 0.87ppm |
| NIST chemical information | information provided by: webbook.nist.gov (external link) |
| (IARC) carcinogen classification | 3 (Vol. 54) 1992 |
| EPA chemical substance information | information provided by: ofmpeb.epa.gov (external link) |
| Introduction | sulfur dioxide is the most common sulfur oxide, which is a colorless gas with a strong pungent odor. It is one of the major atmospheric pollutants. The gas is ejected from a volcanic eruption and sulfur dioxide is also produced in many industrial processes. |
| color and odor | sulfur dioxide is a colorless, spicy and ambient odor gas. |
| Structure | SO2 is a type V molecule, and its symmetry point group is C2v. The sulfur atom has an oxidation state of 4 and a formal charge of 0, surrounded by 5 electron pairs, and thus can be described as a hypervalent molecule. From the viewpoint of molecular orbital theory, it is believed that most of these valence electrons participate in the formation of S-O bonds. |
| source of pollutants | combustion of sulfur-containing petroleum, coal and natural gas, digestion and combustion of sulfide ores, and a variety of sulfur-containing raw materials processing and production processes can produce sulfur dioxide and air pollution. Since coal and oil are the main sources of energy, the SO2 produced by the combustion of coal and oil now accounts for 70% of the pollution in the atmosphere. The industrial production process of SO2 mainly includes non-ferrous metal smelting, petroleum refining, sulfuric acid manufacturing, sulfur refining, paper making, vulcanized rubber and so on. Among them, non-ferrous metal smelting and sulfuric acid manufacturing are the most serious. |
| Use | sulfur dioxide can be used as a preservative, commonly used in dried fruits, pickled vegetables, sausages, fruit and vegetable juices, cider, vinegar and alcohol in different kinds of food and beverages. Although the toxicity of sulfur dioxide residues in food is very low, but people who are sensitive to sulfur dioxide may cause asthma, Head Pain or Nausea of allergic reactions. used as organic solvent and refrigerant, and used to refine all kinds of lubricating oil mainly used in the production of sulfur trioxide, sulfuric acid, sulfite, thiosulfate, also used as fumigant, bleach, antiseptic, disinfectant, reducing agents such as sulfur dioxide is China's permitted use of reducing bleaching agents. It has a strong inhibitory effect on the food and the oxidase in the plant food. China's provisions can be used for wine and fruit wine, the maximum use of 0.25g/kg, residues should not exceed 0.05g/kg. It is a good solvent for many compounds in industry. It can be used as a raw material for refrigerants, preservatives, bleaching agents and other organic products. It is also used in the manufacture of sodium hydrosulfite and sulfite. Also used in pesticides, pharmaceuticals, man-made fibers, dyes and other industrial sectors. for ICP-AES, AAS, AFS, ICP-MS, ion chromatography, etc. Standard solutions were used for titration analysis. |
| Role of sulfur dioxide | the role of sulfur dioxide is as follows: 1. Preservatives due to the antimicrobial properties of sulfur dioxide, it is sometimes used in different types of food such as dried fruits, pickled vegetables, and processed meat products such as sausages and burgers. Used to maintain the appearance of fruit, or to prevent food decay. The presence of sulfur dioxide, can make the fruit has a special chemical taste, and maintain a fresh appearance. 2. Reducing, bleaching agent sulfur dioxide is also a good reducing agent. In the presence of water, sulfur dioxide can discolor substances. In particular, it is a useful bleaching agent for paper and clothing. This bleaching effect usually does not last long. The oxygen in the air re-oxidizes the reduced dye to restore color. 3. Reagents and solvents liquid sulfur dioxide is a versatile inert solvent, widely used to dissolve strong oxidizing salts. It undergoes self-coupling ionization to generate SO2 and SO32 −. It is also sometimes used as a source of sulfonyl groups in organic synthesis, and the aryl diazonium salt is treated with sulfur dioxide to obtain the corresponding aryl sulfonyl chloride. |
| Environmental Standard | The National Ambient Air Quality Standard provides that the daily average concentration of sulfur dioxide in residential areas should be less than 150 micrograms/cubic meter. |
| harm of sulfur dioxide | sulfur dioxide is a colorless gas with pungent odor, which can stimulate human respiratory organs and eye membranes, long-term inhalation of respiratory system, liver, kidney, heart are harmful. Sulfur dioxide in a certain concentration on the respiratory tract, especially on the upper respiratory tract has a stimulating effect, and can affect the respiratory function. In addition, chlorine dioxide also has a stimulating effect on the eye conjunctiva, and can cause inflammation, but also has a mutagenic and carcinogenic effect at high concentrations. In the atmosphere, it is easy to form sulfuric acid mist, which corrodes metal products and buildings, resulting in acidification of soil and rivers and lakes. The acid mist in the air can be inhaled into the lung tissue, causing lung inflammation, pulmonary edema, especially for infants, and even cause sudden infant death syndrome. |
| solubility in water (g/100ml) | grams dissolved per 100ml of water: 9.4g/20 ℃ |
| identification test | solubility 36 parts by volume were dissolved in 1 part by volume of water, and 114 parts by volume were dissolved in 1 part by volume of ethanol. The filter paper wetted with the mercury nitrate test solution (Ts-141) can be made black. The filter paper treated with the potassium iodate test (TS-191) and the starch test solution (TS-235), exposed to the sample, should be blue, but will fade if the exposure continues. |
| content analysis | The SO2 content (%) is determined by subtracting the difference between the measured moisture content and the nonvolatile residue from 100%.. |
| toxicity | ADI 0~0.7mg/kg (calculated as SO2, including the total ADI value of SO2 and sulfite; FAO/WHO,2001). 1L air containing a few mg can be due to glottic spasm suffocation and death. China's highest standard concentration of 20mg/m. Safe for use in food (FDA,§ 182.3862,2000). |
| preventive measures | can irritate the respiratory tract, cause bronchospasm, and increase respiratory resistance. Can stimulate the eyes, the person's skin is thin and hyperhidrosis parts have stimulation and burning sensation. In case of poisoning, immediately move the patient to a place with fresh air, unpack tight clothes, rapidly inhale oxygen, Rinse eyes and nasal cavities, and rinse your mouth with 2% soda solution. If you accidentally splash the eyes, you should use a lot of warm water to rinse. Severe cases should be sent to the hospital for treatment. The maximum allowable concentration of sulfur dioxide in air is 10mg/m3. If sulfur dioxide and sulfur trioxide are present in the air at the same time, the maximum allowable concentration is correspondingly reduced. operators should wear gas masks, work clothes, latex gloves and other labor protection articles. |
| Use limit | GB 2760-96: can be used for wine, fruit wine as a preservative, 0.25g/kg. Sulfur dioxide residues should not exceed 0.05g/kg. In order to smoke the sulfur method to bleach dried fruit, preserved fruit, dried vegetables, fans, candied varieties allow residues with reference to the "sulfur". Sulfur is sulfur dioxide produced by burning sulfur, which can destroy the cells on the surface of fruit slices and promote drying. At the same time, due to its reducing effect, it can destroy the oxidation system of enzymes and prevent oxidation. So that the tannin in the fruit is not oxidized to become brown. Can preserve the fruit of vitamin C. Sulfur dioxide concentration in the sulfur chamber is generally 1% ~ 2%, up to 3%. Sulfur fumigation time 30~50min, up to 3H. FAO/WHO(1984;mg/kg): white granulated sugar 20 (Specification A), 70 (Specification B); Sugar powder, fructose, glucose powder 20 (introduced amount); Soft white sugar 40; anhydrous glucose, dextrose monohydrate 20; Glucose syrup 40; 400 when used to make candy; High concentration glucose syrup 40, 150 when used to make candy; Bleached currants 1500; Jam, jelly and orange peel jelly 100, with volume; Dried apricot 2000; Pickled cucumber 50, with initial product; Concentrated pineapple juice with preservative 500 (for manufacturing only). EEC(1990;mg/k): coconut dried 50; Beer 70; Candied and canned anthocyanin 100; Apple juice 200; Most of the dried fruit 2000; Thousand papaya enzyme and papain 30000. EEC-HACSG recommendations cannot be used for children's food. FDA,182.3862(2000): Do not use in meat and B vitamins. SOURCE Food. According to the maximum dosage of Japanese regulations with reference to "sodium dithionite". |
| production method | The Ammonium sulfite-ammonium bisulfite mother liquor obtained from the absorption process of tail gas of sulfuric acid plant by the ammonia-acid method, about 100% of the sulfur dioxide gas produced, by compression and freezing method, can be obtained by liquid sulfur dioxide. (1) the compression method uses sulfuric acid to decompose ammonium sulfite-ammonium bisulfite mother liquor, and the sulfur dioxide gas generated by the decomposition is condensed, dried, filtered, and then compressed and liquefied to prepare a liquid sulfur dioxide product. The 2NH4HSO3 H2SO4 →(NH4)2SO4 2SO2 2H2O(NH4)2SO3 H2SO4 →(NH4)2SO4 SO2 H2O(2) freezing method uses sulfuric acid to decompose ammonium sulfite-ammonium bisulfite mother liquor, the sulfur dioxide gas generated by the decomposition is dried and sent to a low-temperature condenser for condensation under normal pressure, and the temperature is maintained at a liquefaction point of -10 ° C. Or less by freezing with ammonia. A finished product of liquid sulfur dioxide is obtained. Its (NH4)2SO3 H2SO4 →(NH4)2SO4 SO2 H2O2NH4HSO3 H2SO4 →(NH4)2SO4 2SO2 2H2O pure oxygen combustion method to burn sulfur and pure oxygen in a sulfur incinerator to generate a high concentration of sulfur dioxide gas, after purification, drying, compression liquefaction, condensation, prepared liquid sulfur dioxide products. The sulfur dioxide gas purified by S2 2O2 → 2SO2 sodium citrate method is absorbed by sodium citrate solution, and then sulfur dioxide is extracted by low-pressure steam, cooled and separated from condensed water, dried with concentrated sulfuric acid, and then compressed and liquefied, condensation, the preparation of liquid sulfur dioxide products. The combustion method uses sulfur and pure oxygen to burn in a sulfur incinerator to generate high-concentration Soz gas. It can be dried, compressed and condensed into liquid SO2. S O2 → SO2 ammonia absorption method uses 350 ~ 400g/L ammonia water to absorb the tail gas of sulfuric acid plant, and the absorption solution contains 120 ~ 130g/L ammonium sulfite and 230 ~ 270g/L ammonium bisulfite, the decomposition of sulfuric acid can release a high concentration of SO2 gas. SO2 gas is condensed to remove water, dried in concentrated sulfuric acid, filtered by Coke or fiber filter, compressed to 0.5MPa, separated into liquid product after cooling. 2NH4HSO3 H2SO4→(NH4)2SO4 2H2O 2SO3↑(NH4)2SO3 H2SO4→(NH4)2SO4 H2O SO2↑ |
| category | hazardous gas |
| toxicity grade | poisoning |
| Acute toxicity | inhalation-rat LC50: 2520 PPM/1 hour; Inhalation-mouse LC50: 3000 PPM/30 min |
| stimulation data | eyes-rabbits 6 PPM/4 hours/32 days mild |
| explosive hazard characteristics | the cylinder can be exploded by heat and sun exposure; The leakage releases highly toxic gas |
| flammability hazard characteristics | non-combustible; Toxic sulfur oxide smoke generated in fire scene |
| storage and transportation characteristics | The warehouse is ventilated and dried at low temperature; It is stored separately from oxidants and combustibles |
| extinguishing agent | Water |
| Occupational Standard | TWA 5 mg/m3; Tel 10 mg/m3 |
| DOT Classification | 2.3, Hazard Zone C (Gas poisonous by inhalation) |
| toxic substance data | information provided by: pubchem.ncbi.nlm.nih.gov (external link) |
| immediate life-and health-threatening concentration | 100 ppm |
Last Update：2024-04-09 15:16:52
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View History
Raw Materials for Sulfur dioxide (SO2)
Downstream Products for Sulfur dioxide (SO2)
Sodium bisulfite
Ammonium Bisulfite
Sodium sulfite
ammonium sulfite
Sulfuryl chloride
sulfuryl fluoride
Bromine
Ammonium Bisulfite
Sodium sulfite
ammonium sulfite
Sulfuryl chloride
sulfuryl fluoride
Bromine