Sodium metabisulfite (SMBS), the other name is sodium pyrosulfite, is an inorganic compound with the chemical formula Na2S2O5. Its appearance is white crystalline powder with a strong pungent smell, soluble in water, and its aqueous solution is acidic. Once it comes into contact with a strong acid, it releases sulfur dioxide and forms the corresponding salts. If left in the air for a long time, it will be oxidized to sodium sulfate, so sodium metabisulphite cannot be stored for a long time.
Sodium metabisulfite powder can be divided into industrial grade and food grade, and their quality indicators are also different. Please review the technical specifications below.
| Item | Specification |
|---|
| Na2S2O5 content | 97% min |
| Heavy metals ( as Pb) | 0.0005%max |
| Arsenic ( As) | 0.0001% max |
| Iron (Fe) | 0.0030% max |
| Water insoluble | 0.02% max |
| PH value | 4.0-4.8 |
| Package and Storage | Plastic-woven sack with polythene inner bag, net weight 25kg, 50kg or 1000kg; keep away from water or moisture, do not pile up the open air. |
Applications of Sodium Metabisulfite
Food Grade Sodium Metabisulfite
Sodium metabisulfite can be used as bleaching agent and leavening agent for food such as biscuits and cakes, nutrient retaining agent for dehydrating vegetables, preservative for storing fruits, bactericidal preservative for brewing and beverages, etc.
Industrial Grade Sodium Metabisulphite
pharmaceutical industry. SMBS can be used for the purification of chloroform, phenylpropyl sulfone and benzaldehyde;
Rubber industry. It can be used as a coagulant.
Printing and dyeing industry. SMBS chemical is used as a dechlorination agent for cotton cloth after bleaching, a scouring aid for cotton cloth, and a mordant for printing and dyeing.
Tanning industry. Used for leather treatment, which can make the leather soft, plump, tough, waterproof,anti-folding, and wear-resistant.
SMBS can be used as a developer in the photosensitive industry.
Used in the chemical industry to produce hydroxyvanillin, hydroxylamine hydrochloride, etc.
Production Process
(1) Dry method. Stir soda ash and water evenly according to a certain molar ratio. When the Na2CO3.nH2O is formed in a block, put it into the reactor, keep a certain gap between the blocks, and then pass in SO2 until the reaction is completed, and take out the block. Objects are crushed to obtain the finished product.
(2) Wet method. Adding a certain amount of soda ash to the sodium bisulfite solution to form a suspension of sodium sulfite, and then add SO2 to form sodium pyrosulfite crystals, which are centrifuged and dried to obtain the finished product.
