Name: China Chemical Manufacturer Supply Best Purity Sodium metabisulfite CAS 7681-57-4 with good service
Brand: Wuhan Fortuna Chemical Co., Ltd.

Specifications Of Sodium metabisulfite CAS 7681-57-4

Items	Specifications	Results
Characters	This product is a colorless to off-white crystalline or crystalline powder, readily soluble in water and slightly soluble in ethanol.	The off-white crystalline powder is readily soluble in water and slightly soluble in ethanol.
Identification	The solution shows the reactions of sulfate identification (1) and (3)	Positive reaction
Identification	This product shows a flame reaction with sodium salts	Conforms
PH	3.5~5.0	4.1
Clarity and color	Clear and colorless	Clear and colorless
chloride	NMT 0.05%	＜0.05%
thiosulfate	NMT 0.05%	＜0.05%
ferric salt	NMT 0.002%	＜0.002%
Heavy Metal	NMT 20 per million	＜20 per milion
arsenic salt	NMT0.0001%	＜0.0001%
bacterial endotoxin	＜5EU/mg	＜5EU/mg
Total aerobic bacteria count	NMT10³cfu/g	＜10cfu/g
Assay	NLT 95.0%	97.3%
Conclusion	The product conforms to the above specifications.

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Parameters Of Sodium metabisulfite CAS 7681-57-4

Product parameters
Cas number:	7681-57-4
Appearance:	White or yellowish crystalline powder
Purity:	96.5%min
Package details:	25kg/bag; 50kg/bag
Brand:	Fortunachem

Sodium metabisulfite (or sodium pyrosulfite) is an inorganic compound with the chemical formula Na₂S₂O₅. It is a white or yellowish-white crystalline powder with a sharp, pungent sulfur dioxide (SO₂) odor.

Key Chemical Behavior:
It is not stable in water and readily decomposes, releasing sulfur dioxide (SO₂). This property is the source of its usefulness.

Major Uses of Sodium Metabisulfite

1. Food Industry (Common Food Additive: E223)

It is widely used as a preservative, antioxidant, and bleaching agent.

Preservative: Inhibits the growth of bacteria, yeasts, and molds. Extends shelf life.
Antioxidant: Prevents browning (enzymatic and non-enzymatic) in fruits and vegetables. Used in:

Dried fruits (e.g., apricots, golden raisins)
Potato products (french fries, dehydrated potatoes)
Fruit juices, concentrates, and syrups
Wine and cider (see below)

Bleaching Agent: Used in the production of some sugars (like beet sugar) and maraschino cherries to achieve a bright color.

2. Winemaking & Brewing (Critical Tool)

It is indispensable in these industries, where it is often referred to simply as "sulfites" or "campden tablets" (a tablet form).

Antimicrobial Agent: Kills or inhibits wild yeasts and bacteria, allowing cultivated yeast to ferment without competition.
Antioxidant: Protects wine from oxidation, which spoils color and flavor (prevents "browning" of white wines).
Stabilizer: Halts fermentation at a desired point and prevents refermentation in the bottle.
Equipment Sanitizer: Used to sanitize fermentation vessels, barrels, and bottles.

3. Pharmaceutical Industry

Antioxidant: Used as an excipient in some medications (injectable drugs, liquid formulations) to prevent the active ingredient from oxidizing and degrading.
Sterilizing Agent: For some equipment.

4. Water Treatment

Dechlorination: Removes excess chlorine (and chloramines) from water. It is a common chemical for neutralizing chlorine in wastewater, in industrial processes, and even in home brewing (to make tap water safe for yeast).
Oxygen Scavenger: Used in boilers and oil recovery to remove dissolved oxygen, preventing corrosion.

5. Photography (Traditional Film Development)

Component of Developers and Fixers: Acts as a preservative to prevent oxidation of the developing agents.

6. Textile & Chemical Manufacturing

Bleaching Agent: For wool, silk, and certain synthetic fibers.
Reducing Agent: In various chemical synthesis processes.
Waste Treatment: Neutralizes peroxide bleaches and removes heavy metals (e.g., chromium) from wastewater.

Important Safety & Regulatory Information

Allergies and Sensitivities

"Contains Sulfites" Warning: In many countries, foods and beverages containing more than 10 ppm SO₂ must carry this label.
Asthma Risk: A small subset of the population (particularly asthmatics, estimated ~3-10%) can have severe sulfite sensitivity, leading to breathing difficulties, wheezing, and in rare cases, anaphylaxis.
Generally Recognized as Safe (GRAS): For the vast majority of people, it is safe when consumed at regulated levels.

Handling Precautions

Irritant: Powder can irritate eyes, skin, and respiratory tract. Use in well-ventilated areas.
Toxic Gas Release: NEVER MIX WITH ACIDS (like vinegar, bleach, or hydrochloric acid). This mixture produces toxic sulfur dioxide gas, which can cause severe respiratory distress.
Corrosive to Metals: Releases SO₂ in moist air, which can corrode metals.

Comparison with Related Compounds

Compound	Formula	Primary Use Context	Relationship
Sodium Metabisulfite	Na₂S₂O₅	Versatile; food (E223), winemaking, water treatment, photography. Contains ~67% SO₂.	The most common solid source of SO₂; dissociates to bisulfite in solution.
Sodium Bisulfite	NaHSO₃	Very similar to metabisulfite, often used interchangeably. Contains ~61% SO₂.	The form metabisulfite creates in water. Often a liquid solution in industry.
Sodium Sulfite	Na₂SO₃	Paper pulping, water treatment, food preservative.	Releases less SO₂, more alkaline.
Potassium Metabisulfite	K₂S₂O₅	Identical uses, especially in winemaking (preferred by some for potassium sensitivity).	Potassium version; used where sodium intake is a concern.

Summary

Sodium metabisulfite is a versatile reducing agent, preservative, and antioxidant whose power comes from its controlled release of sulfur dioxide (SO₂). Its primary roles are:

Preserving Food & Drink: Preventing spoilage and browning.
Enabling Winemaking: As an antimicrobial and antioxidant.
Treating Water: As a dechlorinating agent.
Industrial Chemical: In textiles, photography, and as a reducing agent.

Its use is strictly regulated in food due to potential allergenic reactions in sensitive individuals, but it remains a critical and legal additive worldwide.