Sulfur dioxide

Sulfur dioxide is the chemical compound with the formula SO2. It is produced by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide. Besides the oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus acid rain. This is a cause for concern about the environmental impact of the use of these fuels for energy.

Sulfur dioxide is an intermediate in the production of sulfuric acid, which is converted to sulfur trioxide and then to oil, which turns into sulfuric acid. Sulfur dioxide for this purpose is done when sulfur combines with oxygen. The method of converting sulfur dioxide to sulfuric acid is called the contact process. Several million pounds produced annually for this purpose.

Sulfur dioxide is sometimes used as a preservative in dried apricots and other dried fruits due to its antimicrobial properties and is sometimes called E220 when used this way. As a preservative, maintains the appearance of the fruit and avoid rotting. His presence gives the fruit a distinctive chemical taste.

Sulfur dioxide is an important compound in wine making, and is designated as parts per million in wine, E number: E220. It is present even in the wine unsulphurated called at concentrations up to 10 milligrams per liter. Serves as an antibiotic and antioxidant, protects the wine from decomposition by bacteria and oxidation. It also helps keep volatile acidity at desirable levels. Sulfur dioxide is responsible for the words "contains sulfites" found on wine labels. Wines with SO2 concentrations below 10 ppm do not require "contains sulfites" on the label by U.S. law and the EU. The maximum allowable SO2 in wine is 350 ppm in the U.S., the EU is 160 ppm for red wines and 210 ppm for white wines and rosés. At low concentrations of SO2 is mostly undetectable in wine, but more than 50 ppm, SO2 is evident in the nose and taste of wine.SO2 is also a very important element in winery sanitation. Bodegas and equipment clean, and because chlorine can not be used in a warehouse, a mixture of SO2, water and citric acid is commonly used for cleaning and disinfecting equipment.

Basic properties:
Properties Value
chemical formula SO2
molecular weight 64.064 g/mol
phase gas (at STP)
melting point -73 °C
boiling point -10 °C
density 0.002619 g/cm3 (at 25 °C)

Gas properties:
Properties Value
density 0.002619 g/cm3 (at 25 °C)
vapor density 2.26 (relative to air)
molar volume 24460 cm3/mol
surface tension 0.02859 N/m
refractive index 1.3047
dynamic viscosity 1.3×10-5 Pa s (at 25 °C)