Диоксид серы

Description

Sulfur dioxide SO2 is a colorless gas with a pungent suffocating odor, heavier than air, and non-flammable. The odor detection threshold is low, about 0.33 ppm. Dissolving in water, it forms sulfurous acid. It is produced industrially by burning elemental sulfur, roasting sulfide ores and as a by-product of non-ferrous metallurgy. The section of the original product card with a detailed description is empty, so the characteristics below are given from reference databases.

Basic Attributes

• CAS No.: 7446-09-5
• Chemical formula: O2S (SO2)
• English name: Sulfur dioxide
• Molecular weight: 64.07
• Color and Form: Colorless gas or liquid

Physico-chemical characteristics

• Boiling point: −10 °C at 760 mmHg. Art.
• Melting point: −75.5 °C
• Liquid density: 1.434 g/cm³ at 0 °C
• Gas density: 2.619 g/l at 25 °C
• Vapor density: 2.26 (relative to air) - gas heavier than air
• Steam pressure: 330 kPa at 20 °C (2432 mmHg at 20 °C)
• Solubility in water: 8.5 ml per 100 ml at 25 °C, producing sulfurous acid
• Heat of evaporation: 22.92 kJ/mol
• Odor: strong suffocating, perception threshold from 0.33 ppm
• Flammability: does not burn

Chemical behavior

Sulfur dioxide acts as both a reducing agent and an oxidizing agent. In the presence of oxygen on the catalyst, it is oxidized to sulfur trioxide - this is what the contact production of sulfuric acid is based on. With water it gives an equilibrium system of sulfurous acid, with alkalis - sulfites and hydrosulfites. Reducing properties are used for decolorization and to bind dissolved oxygen and residual chlorine.

Scope of application

• Production of sulfuric acid by contact method is the main consumer
• Sulphite pulping in the pulp and paper industry
• Bleaching of paper, wool, silk, straw and other materials sensitive to chlorine bleaching
• Food industry and winemaking: preservative and antioxidant with index E220, suppression of wild microflora and enzymatic darkening of dried fruits and juices
• Disinfection of containers, barrels and storage areas
• Dechlorination of water and wastewater, binding of excess oxidizer
• Preparation of sulfites, hydrosulfites, thiosulfate, dithionite
• Solvent and reagent in organic synthesis
• Historically - refrigerant under the designation R-764

Toxicity and exposure

The gas irritates the mucous membranes of the eyes and upper respiratory tract. When inhaled, it causes coughing, tickling, and bronchospasm; in persons with bronchial asthma, the reaction develops at noticeably lower concentrations. High concentrations can lead to pulmonary edema. Sulfur dioxide is one of the main pollutants of atmospheric air and the cause of acid rain, therefore SO2 emissions are standardized, and flue gas desulfurization systems are installed at enterprises.

Storage and handling

It is supplied as liquefied gas in cylinders and tanks under its own vapor pressure. Cylinders are stored in a cool, ventilated room, away from heat sources, away from alkalis, oxidizing agents and food. The premises are equipped with exhaust ventilation and gas analyzers: gas is heavier than air and accumulates at the bottom. Personnel are provided with respiratory and eye protection equipment. Frostbite may result from contact with liquefied product.

Synonyms

• Sulfur dioxide, sulfur dioxide
• Sulfur dioxide, sulfurous acid gas, sulfur oxide (SO2)
• Food additive E220