Sulfurous acid.

sulfurous acid - a volatile inorganic dibasic acid of medium strength.Fragile compound is known only in aqueous solution at a concentration of no more than six per cent.In attempts to isolate pure sulfurous acid, it decomposes to sulfur dioxide (SO2) and water (H2O).For example, when exposed to sulfuric acid (H2SO4) in a concentrated form on sodium sulfite (Na2SO3) instead of sulfurous acid released sulfur oxide (SO2).Here is this reaction:

Na2SO3 (sodium sulfite) + H2SO4 (sulfuric acid) = Na2SO4 (sodium sulphate) + SO2 (sulfur dioxide) + H2O (water)

solution of sulfurous acid

during storage should be excludedair access.Otherwise, sulfurous acid, slowly absorbing the oxygen (O2), turn into sulfuric.

2H2SO3 (acid sulfurous) + O2 (oxygen) = 2H2SO4 (sulfuric acid)

Solutions sulfurous acid have quite specific smell (like the smell left after burning match), the presence of which can be explained by the presence of sulfur dioxide (SO2), chemicallybound water.

chemical properties sulphurous ac


1. sulfurous acid (formula H2SO3) can be used as a reducing agent or oxidizing agent.

H2SO3 is a good reducing agent.You can use it free of halogens get halides.For example:

H2SO3 (sulfurous acid) + Cl2 (chlorine gas) + H2O (water) = H2SO4 (sulfuric acid) + 2HCl (hydrochloric acid)

But when interacting with strong reducing this acid will act as an oxidant.An example is the reaction of sulfurous acid with hydrogen sulfide:

H2SO3 (sulfurous acid) + 2H2S (hydrogen sulfide) = 3S (sulfur) + 3H2O (water)

2. Considered contact chemical compound forms two kinds of salt - sulfites (middle) and hydrosulfites(acidic).These salts are reducing agents, as well as (H2SO3) sulfurous acid.With their oxidized form salts of sulfuric acid.When ignition sulfites active metal sulfides and sulfates formed.This oxidation reaction, self-healing.For example:

4Na2SO3 (sodium sulfite) = Na2S (sodium sulfide) + 3Na2SO4 (sodium sulfate)

sodium sulfite and potassium (Na2SO3 and K2SO3) are used for dyeing fabrics in the textile industry, in the bleaching of metals, as well as photographs.Calcium sulfite (Ca (HSO3) 2) exists only in the solution used for processing the wood material into a special sulfite pulp.From it then make paper.

Application sulfurous acid

sulfurous acid is used:

- for bleaching wool, silk, wood pulp, paper and other similar substances do not withstand bleaching using a strong oxidizing agents (eg, chlorine);

- preservative and antiseptic, for example, to prevent fermentation of grain in the preparation of the starch or to prevent fermentation in wine barrels;

- for the preservation of products, such as preservation of vegetables and fruits;

- in the processing of wood chips into pulp sulphite, which later obtained the paper.In this case, a solution of calcium sulfite (Ca (HSO3) 2), which dissolves the lignin - a special substance that binds the cellulose fibers.

sulfurous acid: getting

This acid can be obtained by dissolving sulfur dioxide (SO2) in water (H2O).You need the sulfuric acid in concentrated form (H2SO4), copper (Cu) and the tube.The algorithm of actions:

1. Carefully pour into the tube concentrated sulfurous acid, and then to put a piece of copper.Heat.The following reaction occurs:

Cu (copper) + 2H2SO4 (sulfuric acid) = CuSO4 (sulphate sulfur) + SO2 (sulfur dioxide) + H2O (water)

2. The flow of sulfur dioxide should be directed to the tube with water.When it is dissolved in part, a chemical reaction with water, resulting in the formation sulfurous acid:

SO2 (sulfur dioxide) + H2O (water) = H2SO3

So passing sulfur dioxide through the water, you can get sulfurous acid.It's worth noting that this gas has an irritating effect on the membranes of the respiratory tract, can cause an inflammation, and loss of appetite.Prolonged inhalation of its possible loss of consciousness.To address this need the gas with the utmost care and attention.