Sulfurous Acid Chemical Properties

Density 

1.03 g/mL at 25 °C(lit.)

vapor density 

2.3 (vs air)

solubility 

solution of SO2 in H2O

form 

Liquid

pka

1.92(at 25℃)

color 

Colorless

PH

pKa1= 1.658, pKa2 = 6.820(25℃)

Water Solubility 

Miscible with water.

Sensitive 

Air Sensitive

Merck 

14,8976

Dielectric constant

15.6（0℃）

Stability:

Stable. Incompatible with strong bases.

InChIKey

LSNNMFCWUKXFEE-UHFFFAOYSA-N

LogP

-1.579 (est)

CAS DataBase Reference

7782-99-2(CAS DataBase Reference)

EPA Substance Registry System

Sulfurous acid (7782-99-2)

Safety Information

Hazard Codes 

C,Xn

Risk Statements 

20-34-36/38

Safety Statements 

26-36/37/39-45

RIDADR 

UN 1833 8/PG 2

WGK Germany 

1

RTECS 

WT2775000

F 

10-23

TSCA 

Yes

HazardClass 

8

PackingGroup 

II

HS Code 

28111990

MSDS

• Language:English Provider:SigmaAldrich
• Language:English Provider:ALFA

Sulfurous Acid Usage And Synthesis

Description

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).

Chemical Properties

colourless liquid

Chemical Properties

SULFUROUS ACID, colorless liquid, prepared by dissolving SO2 in H2O. Reagent grade H2SO3 contains approximately 6% SO2 in solution

Uses

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.

Uses

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.”

Uses

Dental bleach.

Definition

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.

General Description

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.

Air & Water Reactions

Soluble in water with release of heat.

Reactivity Profile

Colorless, corrosive, moderately toxic liquid. When heated to decomposition SULFUROUS ACID emits toxic fumes of oxides of sulfur [Lewis, 3rd ed., 1993, p. 1196].

Hazard

Toxic by ingestion and inhalation, strong irritant to tissue.

Health Hazard

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.

Fire Hazard

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.

Industrial uses

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.

Safety Profile

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.

References

https://en.wikipedia.org/wiki/Sulfurous_acid
http://printwiki.org/Sulfurous_Acid
http://www.softschools.com/formulas/chemistry/sulfurous_acid_uses_properties_structure_formula/242/
https://pubchem.ncbi.nlm.nih.gov/compound/Sulfurous_acid#section=Top
http://www.chemistrylearner.com/sulfurous-acid.html

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