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Sulfurous Acid

Chemical Name:
Sulfurous Acid
Molecular Formula:
Lewis structure
h2so3 lewis structure
Molecular Weight:
MDL Number:
MOL File:
MSDS File:
Last updated:2024-02-27 14:09:48

Sulfurous Acid Properties

Density 1.03 g/mL at 25 °C(lit.)
vapor density 2.3 (vs air)
solubility solution of SO2 in H2O
pka 1.92(at 25℃)
form Liquid
color Colorless
Water Solubility Miscible with water.
Sensitive Air Sensitive
Merck 14,8976
Dielectric constant 15.6(0℃)
Stability Stable. Incompatible with strong bases.
LogP -1.579 (est)
Substances Added to Food (formerly EAFUS) SULFUROUS ACID
CAS DataBase Reference 7782-99-2(CAS DataBase Reference)
EWG's Food Scores 1
EPA Substance Registry System Sulfurous acid (7782-99-2)


Risk and Safety Statements

Symbol(GHS)  GHS hazard pictogramsGHS hazard pictograms
Signal word  Danger
Hazard statements  H314-H332
Precautionary statements  P261-P271-P280-P303+P361+P353-P304+P340+P310-P305+P351+P338
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
HazardClass  8
PackingGroup  II
HS Code  28111990
NFPA 704
3 1

Sulfurous Acid price More Price(7)

Manufacturer Product number Product description CAS number Packaging Price Updated Buy
Sigma-Aldrich 247626 Sulfur dioxide solution ACS reagent, ≥6% 7782-99-2 100g $80.2 2024-03-01 Buy
Sigma-Aldrich 247626 Sulfur dioxide solution ACS reagent, ≥6% 7782-99-2 2kg $262 2024-03-01 Buy
Alfa Aesar 033275 Sulfurous acid, ACS 6.0% SO2 min 7782-99-2 500ml $86.1 2024-03-01 Buy
Alfa Aesar 033275 Sulfurous acid, ACS 6.0% SO2 min 7782-99-2 *4x500ml $317 2024-03-01 Buy
Sigma-Aldrich 247626 Sulfur dioxide solution ACS reagent, ≥6% 7782-99-2 500g $142 2024-03-01 Buy
Product number Packaging Price Buy
247626 100g $80.2 Buy
247626 2kg $262 Buy
033275 500ml $86.1 Buy
033275 *4x500ml $317 Buy
247626 500g $142 Buy

Sulfurous Acid Chemical Properties,Uses,Production


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


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.


Dental bleach.


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].


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.


Global( 212)Suppliers
Supplier Tel Email Country ProdList Advantage
Hubei Jusheng Technology Co.,Ltd.
18871490254 CHINA 28180 58
Hubei xin bonus chemical co. LTD
86-13657291602 CHINA 22968 58
Qingdao kaimoshi biochemical technology co., ltd.
+86-0571-87191913 +86-19957014543 CHINA 144 58
Hebei Mojin Biotechnology Co., Ltd
+8613288715578 China 12465 58
Hefei TNJ Chemical Industry Co.,Ltd.
0551-65418671 China 34571 58
+8615255079626 China 23556 58
Shaanxi Dideu Medichem Co. Ltd
+86-029-89586680 +86-18192503167 China 9128 58
+8617731987558 China 990 58
Hebei Duling International Trade Co. LTD
+8617333973358 China 15544 58
Hebei Guanlang Biotechnology Co., Ltd.
+86-19930503259 +86-19930503259 China 18451 58

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View Lastest Price from Sulfurous Acid manufacturers

Image Update time Product Price Min. Order Purity Supply Ability Manufacturer
Sulfurous acid pictures 2023-03-31 Sulfurous acid
US $50.00 / kg 1kg 99% 20 tons Hebei Duling International Trade Co. LTD
Sulfurous Acid pictures 2023-01-31 Sulfurous Acid
US $0.00 / KG 1KG 99% 50000KG/month Hebei Mojin Biotechnology Co., Ltd
  • Sulfurous acid pictures
  • Sulfurous acid
  • US $50.00 / kg
  • 99%
  • Hebei Duling International Trade Co. LTD
  • Sulfurous Acid pictures
  • Sulfurous Acid
  • US $0.00 / KG
  • 99%
  • Hebei Mojin Biotechnology Co., Ltd
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