SODIUM METABISULFITE (Sodium Pyrosulfite)

SODIUM METABISULFITE
PRODUCT IDENTIFICATION
CAS NO.	7681-57-4
EINECS NO.	231-673-0
FORMULA	Na₂S₂O₅
MOL WT.	190.10
H.S. CODE
TOXICITY
SYNONYMS	Dinatriumdisulfit; Disulfito de disodio; Disulfite de disodium;
Disodium disulfite; Disodium Salt Pyrosulfurous Acid; Disulfurous acid, disodium salt; Pyrosulfurous acid, disodium salt; Sodium Metabisulfite; Sodium disulfite; Sodium Pyrosulfite;
DERIVATION
CLASSIFICATION
PHYSICAL AND CHEMICAL PROPERTIES
PHYSICAL STATE	white crystalline powder with odor of sulfur dioxide
MELTING POINT	150 C (Decomposes)
BOILING POINT
SPECIFIC GRAVITY	1.48
SOLUBILITY IN WATER	Freely soluble (470g/l)
pH	3.5 - 5
VAPOR DENSITY
AUTOIGNITION
NFPA RATINGS	Health: 1; Flammability: 0; Reactivity: 0
REFRACTIVE INDEX
FLASH POINT
STABILITY	Stable under ordinary conditions. Hygroscopic.
GENERAL DESCRIPTION & APPLICATIONS
Sodium Metabisulfite is a white to slightly yellowish crystalline powder with sulfur dioxide odor; readily soluble in water. Sodium metabisulfite containing more than 65.0% SO₂ w/w releases sulfur dioxide gas when mixed with water. It forms a bisulfite adduct with aldehyde and with ketones to a sulfonic acid. It is used to purify or isolate aldehydes and ketones. Sodium metabisulfite's reductive and sulfonating properties provide versatile applications. It is used as an oxygen scavenger to eliminate the dissolved oxygen in waste water and in pipes. Bisulfite is a reductive bleaching agent. It reduces carbonyl and alcohol groups, which function as colorants of the substances. It is used in bleaching mechanical paper pulp, cotton, wool and kaolin clay. Additional applications include as a preservative (antioxidant), a hair waving agent, and Ensiling agent. Bisulfites are used in industries concerned with leather processing, food and beverage processing, gas purification, water treatment to remove excess chlorine, textiles and pulp processing, and many others. It is used as a reducing agent in chemical manufacturing. It is an alternative to sulfur dioxide which is used in sterlization of equipment. Examples of other metallic bisulfite Calcium Bisulfite [13780-03-5, Ca(HSO₃)₂] A white powder, used as an antiseptic and in pulping process. Potassium Bisulfite [1310-61-8, KHSO₃] Also called potassium acid sulfite, white, water-soluble powder with sulfur dioxide odor; insoluble in alcohol; decomposes when heated; used as an antiseptic and reducing chemical, tanning, and bleaching. Magnesium Bisulfite [13774-25-9, Mg(HSO₃)₂]
SALES SPECIFICATION
TECH GRADE
APPEARANCE	White to slightly yellowish crystalline powder
CONTENT	98.0% min
SO₂	65.0% min
Na₂S₂O₄	2.0% max
INSOLUBLES IN WATER	0.05% max
PARTICLE SIZE	85% (mesh 200)
pH	4 -4.6
Fe	5ppm max
FOOD GRADE
APPEARANCE	White to slightly yellowish crystalline powder
CONTENT	98.0% min
SO₂	65.0% min
Na₂S₂O₄	2.0% max
INSOLUBLES IN WATER	0.05% max
PARTICLE SIZE	85% (mesh 200)
HEAVY METALS	10ppm max
As	1ppm max
Fe	5ppm max
pH	4.5 - 5.5
TRANSPORTATION
PACKING	25kgs or big bag
HAZARD CLASS
UN NO.
EUROPEAN LABELING IN ACCORDANCE WITH EC DIRECTIVES
`Hazard Symbols: XN, Risk Phrases: 22-31-41, Safety Phrases: 26-39-46`
BISULFITE ADDUCTS WITH ALDEHYDE GROUPS
Acetone Sodium Bisulfite: [CAS RN: 540-92-1, (CH₃)₂C(OH)SO₃Na] Crystals that have a slight sulfur dioxide odor and slightly fatty feel; freely soluble in water, decomposed by acids; used in textile dyeing and printing. Sodium Formaldehyde Bisulfite [CAS RN: 870-72-4 CH₃NaO₄S] A compound used as a fixing agent for fibers containing keratin, in metallurgy for flotation of lead-zinc ores, and in photography Indole-3-acetaldehyde Sodium Bisulfite [CAS RN: 20095-27-6, C₁₀H₉NO · NaHSO₃] Glutaraldehyde bis(sodium bisulfite) [CAS RN: 7420-89-5, C₅H₁₂O₈S₂] used as an antiseptic Menadione Sodium Bisulfite [CAS RN: 57414-02-5, C₁₁H₉NaO₅S] a water-soluble derivative of menadione provitamin which converted in the body to active vitamin K. Glyoxal sodium bisulfite [CAS RN: 332360-05-1, [CH(OH)SO₃Na]₂] nonaqueous form of glyoxal
OTHER INFORMATION
Sulfate (also spelled sulphate in Europe) is any chemical compound containing the SO₄^2- ion related to sulfuric acid (H₂SO₄). Sulfates are salts or esters of sulfuric acid, formed by replacing one or both of the hydrogens with a metal or a radical as in sodium sulfate, Na₂SO₄. Sulfates in which both hydrogens are replaced are called normal sulfates. Bisulfate is a compound that has the HSO₄^- radical. Bisulfate (called also hydrogen sulfate or acid sulfate) is a compound formed by replacing only one hydrogen in sulfuric acid. Sulfite (also sulphite) is a compound that contain the sulfite ion SO₃^2-. Sulfites are salts or esters of sulfurous acid (H₂SO₃), formed by replacing one or both of the hydrogens with a metal or a radical as in sodium sulfite, Na₂SO₃. Sulfites in which both hydrogens are replaced are called normal sulfites. Bisulfite is a compound that has the HSO₃^- radical. Bisulfate (called also hydrogen sulfite or acid sulfite) is a compound formed by replacing only one hydrogen in sulfurous acid. The term of 'meta' or 'pyro' is the chemical prefix for oxo acid formed through the loss of one water molecule (dehydration) from two molecules of ortho acid by heating. Pyrosulfuric acid is an example ( 2H₂SO₄ - H₂O = H₂S₂O₇). Ortho acid is the compound fully hydrated acid or its salts. Orthophosphoric acid is an example (2·H₃PO₄ = P₂O₅^.3H₂O), in contrast to the less hydrated form, pyrophosphoric acid (2·HPO₃ = P₂O₅^.H₂O). Na₂O₅S₂ is called sodium metabisulfite (2·HNaO₃S - H₂O). Sulfide is a compound having one or more sulfur atoms in which the sulfur is connected directly to a carbon, metal, or other nonoxygen atom; for example sodium sulfide, Na₂S. Sulfide ion is S^2- with oxidation number -2. Bisulfide ion is an anion formed by two sulfur atoms having an overall -2 charge, (S₂)^2-. Sulfamate is a salt of sulfamic acid (HSO₃NH₂). Calcium sulfamate Ca(SO₃NH₂)₂ is an example.