Sulfurous Acid is a weak and unstable inorganic acid, which is considered an aqueous solution of sulfur dioxide in water. It is formed theoretically by burning sulfur to produce sulfur dioxide, which is then reacted with water. However, there is no evidence that sulfurous acid exists in solution, while the molecules of which has been detected in the gas phase, since the reaction is reversible and the acid readily decomposes back into the reactants. Sulfurous acid is not usually available in its acid form, but more commonly prepared as its sodium or potassium salts.
Sulfurous acid and its salts are commonly applied as powerful reducing agents and disinfectant agents due to its strong reducibility. It is also considered as a mild bleaching agent especially for applications having chlorine sensitive materials. Besides, Sulfurous acid is a food additive listed on the EAFUS food Additive Database (Jan. 2001).
SULFUROUS ACID, colorless liquid, prepared by dissolving SO2 in H2O. Reagent grade H2SO3 contains approximately 6% SO2 in solution
Sulfurous acid (H2SO3) can be produced by burning sulfur to form sulfur dioxide (SO2) gas
and by then dissolving the gas in water to form sulfurous acid. This is the acid produced by
burning coal that has a high sulfur content; the gaseous sulfur dioxide by-product of combustion
then combines with atmospheric water to form “acid rain.”
As a bleaching agent, sulfurous acid is used for whitening wool, silk, feathers, sponge, straw, wood, and other natural products. In some areas, its use is permitted for bleaching and preserving dried fruits. The salts of sulfurous acid are sulfites.
A weak acid found only in
solution, made by passing sulfur(IV) oxide
into water. The solution is unstable and
smells of sulfur(IV) oxide. It is a reducing
agent, converting iron(III) ions to iron(II)
ions, chlorine to chloride ions, and orange dichromate(VI) ions to green chromium(III) ions.
Sulfurous acid, H2S03, is an unstable, water-soluble, colorless liquid with a pungent burning sulfur odor. Corrosive to metals and tissue. It is derived from absorption of sulfur dioxide( S02) in water.Reagent grade sulfurous acid contains about 6% sulfur dioxide in solution. Sulfurous acid is a strong reducing agent.It is readily oxidized to sulfuric acid and is itself reduced to hydrogen sulfide by zinc and dilute sulfuric acid. Sulfurous acid is used in the synthesis of medicines and chemicals, in the manufacture of paper and wine, in brewing, in metallurgy, in ore flotation, as a bleach and analytical reagent, and for refining of petroleum products.
Soluble in water with release of heat.
Colorless, corrosive, moderately toxic liquid. When heated to decomposition SULFUROUS ACID emits toxic fumes of oxides of sulfur [Lewis, 3rd ed., 1993, p. 1196].
Toxic by ingestion and inhalation, strong
irritant to tissue.
TOXIC; inhalation, ingestion or skin contact with material may cause severe injury or death. Contact with molten substance may cause severe burns to skin and eyes. Avoid any skin contact. Effects of contact or inhalation may be delayed. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause pollution.
Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Some are oxidizers and may ignite combustibles (wood, paper, oil, clothing, etc.). Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated.
Sulfurous acid (H2SO3) is usually marketed as liquid SO2. The bulk of SO2 is produced
from off-smelter gases. Although handling of SO2 liquid requires special
equipment, it is frequently used as a pH regulator and depressant, primarily during
the treatment of complex sulfide ores. SO2 is largely used in North American operations
as a pyrite depressant and for the depression of galena during copper/lead
separation.
A poison by ingestion and inhalation. A corrosive irritant to skin, eyes, and mucous membranes. Human systemic effects by ingestion: nausea or vomiting, hypermotility, diarrhea, and othergastrointestinal effects. When heated to decomposition it emits highly toxic fumes ofSOx.
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