Sulfur oxide (sulfur dioxide, sulfur dioxide, sulfur dioxide) is a colorless gas, which under normal conditions has a sharp characteristic odor (similar to the smell of a burning match). It liquefies under pressure at room temperature. Sulfur gas is soluble in water, and unstable sulfuric acid is formed. Also, this substance is soluble in sulfuric acid and ethanol. This is one of the main components that make up volcanic gases.
How to get sulfur dioxide
Obtaining SO2 - sulfur dioxide - in an industrial way consists in burning sulfur or burning sulphides (mainly pyrite is used).
4FeS2 (pyrite) + 11O2 = 2Fe2O3 (iron oxide) + 8SO2 (sulfur dioxide).
Under laboratory conditions, sulphurous gas can be obtained by exposing strong acids to hydrosulfites and sulfites. In this case, the resulting sulfuric acid immediately decomposes into water and sulfur dioxide. For instance:
Na2SO3 (sodium sulfite) + H2SO4 (sulfuric acid) = Na2SO4 (sodium sulfate) + H2SO3 (sulfuric acid).
H2SO3 (sulfur dioxide) = H2O (water) + SO2 (sulfur dioxide).
The third method for producing sulfur dioxide is the action of concentrated sulfuric acid when heated on low-active metals. For example: Cu (copper) + 2H2SO4 (sulfuric acid) = CuSO4 (copper sulfate) + SO2 (sulfur dioxide) + 2H2O (water).
Chemical properties of sulfur dioxide
The sulfur dioxide formula is SO3. This substance belongs to acid oxides.
1. Sulfur dioxide dissolves in water, and sulfuric acid is formed. Under normal conditions, this reaction is reversible.
SO2 (sulfur dioxide) + H2O (water) = H2SO3 (sulphurous acid).
2. With alkalis, sulfur dioxide forms sulfites. For example: 2NaOH (sodium hydroxide) + SO2 (sulfur dioxide) = Na2SO3 (sodium sulfite) + H2O (water).
3. The chemical activity of sulfur dioxide is quite large. The most pronounced reducing properties of sulfur dioxide. In such reactions, the degree of oxidation of sulfur increases. For example: 1) SO2 (sulfur dioxide) + Br2 (bromine) + 2H2O (water) = H2SO4 (sulfuric acid) + 2HBr (hydrogen bromide); 2) 2SO2 (sulfur dioxide) + O2 (oxygen) = 2SO3 (sulfite); 3) 5SO2 (sulfur dioxide) + 2KMnO4 (potassium permanganate) + 2H2O (water) = 2H2SO4 (sulfuric acid) + 2MnSO4 (manganese sulfate) + K2SO4 (potassium sulfate).
The latter reaction is an example of a qualitative reaction to SO2 and SO3. Discoloration of the violet solution occurs).
4. In the presence of strong reducing agents, sulphurous anhydride may exhibit oxidizing properties. For example, in order to extract sulfur from waste gases in the metallurgical industry, the reduction of sulfur dioxide with carbon monoxide (CO) is used: SO2 (sulfur dioxide) + 2CO (carbon monoxide) = 2CO2 (carbon dioxide) + S (sulfur).
Also, the oxidizing properties of this substance are used in order to obtain phosphorous acid: PH3 (phosphine) + SO2 (sulfur dioxide) = H3PO2 (phosphoric acid) + S (sulfur).
Where is sulphurous gas used?
Sulfur dioxide is mainly used to produce sulfuric acid. It is also used as a preservative (E-220) in the production of low alcohol drinks (wine and other drinks of the middle price category). Due to the property of this gas to kill various microorganisms, it is fumigated with storage facilities and vegetable stores. In addition, sulfur oxide is used to bleach wool, silk, straw (those materials that cannot be bleached with chlorine). In laboratories, sulfur dioxide is used as a solvent and in order to obtain various salts of sulfur dioxide.
Physiological effects
Sulfur gas has strong toxic properties. Symptoms of poisoning are a cough, runny nose, hoarseness, a peculiar aftertaste in the mouth, and a strong sore throat. When inhaling sulfur dioxide in high concentrations, difficulty swallowing and suffocation, speech impairment, nausea and vomiting, acute pulmonary edema may develop.
MAC of sulfur dioxide:
- indoors - 10 mg / m³;
- the average daily maximum one-time in atmospheric air is 0.05 mg / m³.
Sensitivity to sulfur dioxide in individuals, plants and animals is different. For example, among the trees, the most stable are oak and birch, and the least - spruce and pine.