Sodium Sulfite

JAM Group Co. is able to supply more than 8000 tons per year of Sulfite Products such as Sodium Sulfite, Sodium Metabisulfite and Catalyzed Sodium Sulfite in accordance with international standards.

What is sodium sulfite?

Sodium Sulfite is the inorganic compound and a white odorless crystal or powder with sulfurous salty taste it decompress when heated,  moreover it sinks in water and dissolves slowly and also transported as a heptahydrate Na2SO3.7H2O. It is generally available in powder, crystalline, and tablet forms

Physical Properties of Sodium Sulfite:

Formula: Na2SO3     

  • Molar mass: 126.043 g/mol
  • IUPAC ID: Sodium sulfite
  • Density: 2.63 g/cm³
  • The heptahydrate form density:   1.561 g/cm3.

When heated to 306.5K (33.4oC), the heptahydrate undergoes dehydration. The anhydrous form melts at a temperature of 500o

Sodium sulfite does not have a specific boiling point since it tends to decompose at high temperatures.

It is moderately soluble in water; its solubility corresponds to 27g/100mL.

The crystal structure of anhydrous Na2SO3 is hexagonal whereas the heptahydrate crystals have a monoclinic structure Ph.  8.00-10.0

Chemical Safety

Chemical Properties of Sodium Sulfite

When sodium sulfite contacts with strong or weak acids, Na2SO3 undergoes decomposition, liberating gaseous sulfur dioxide.

Sodium sulfite reacts with aldehydes to yield a bisulfite adduct. although, sulfonic acids are    produced from its reaction with ketones.

Solutions of sodium sulfite are oxidized by atmospheric oxygen, yielding sodium sulfate. Sodium sulfite is not soluble in ammonia and chlorine

Sodium sulfite production process

Sodium sulfite can be prepared by treating a solution of sodium hydroxide with sulfur dioxide. When conducted in warm water, Na2SO3 initially precipitates as a yellow solid. With more SO2, the solid dissolves to give the disulfite, which crystallizes by cooling.

Sodium Sulfite Preparation

1. In laboratories, sodium sulfite is generally prepared from the reaction between gaseous sulfur dioxide (SO2) and sodium hydroxide (NaOH). The chemical equation for this reaction is given by

SO2 + 2NaOH → Na2SO3 + H2O

The depletion of the NaOH reactant can be detected via the addition of a few drops of concentrated H2SO4, concluding in the liberation of SO2 gas.

2. Industrially, Na2SO3 is produced from the reaction between sulfur dioxide and sodium carbonate solution. At first, sodium bisulfite (NaHSO3) is formed. This compound now reacts with sodium carbonate or sodium hydroxide to yield the sodium sulfite product. The reaction can be generalized to:

Na2CO3 + SO2 → Na2SO3 + CO2

Different grades of sodium sulfite:

  1. Food and photographic grade
  2. Technical grade

Uses of Sodium Sulfite

Sodium sulfite is used in photography, the bleaching of wool, and as preservatives in foods, beverages, and medications. it acts as useful antioxidant compounds and is  also used in the manufacture of pulp for paper and wood products. Its preservative specifications include controlling microbial growth and the prevention of browning and spoilage.

Sodium sulfite application is as a sulfonation and sulfomethylation agent in the chemical manufacturing industry Sodium sulfite is primarily used as a food preservative (e.g., to prevent dried fruit from discoloring) and as an antioxidant. In the past, sodium sulfite was used to make pulp in the paper industry Sodium sulfite is also used water treatment and photography, Oil recovery, food preservatives, and coloring.

Pulp and paper industry

Most sodium sulfite, 54%, is consumed in the pulp and paper industry for semi chemical and

acid sulfite pulping. The Kraft process ( sulfate process) is a process for conversion of wood into wood pulp, which consists of almost pure cellulose fibers, the main component of paper. The Kraft process entails treatment of wood chips with a hot mixture of

water, sodium hydroxide (NaOH), and sodium sulfide (Na2S), , that breaks the bonds that link lignin, hemicellulose, and cellulose. The technology entails several steps, both mechanical and chemical. It is the dominant method for producing paper.

Food preservation

Sodium sulfite is often used to prevent the discoloration of dried fruits because it can act as a preservative. sodium sulfite, is used as preservatives in processed fruit products including dried fruits and juices, it is effective antioxidants that slow browning reactions and improve ascorbic acid retention in certain fruit products, It is  used in the juice and juice beverage industry to inhibit malolactic bacteria, acetic acid bacteria, and spoilage yeasts and molds sodium sulfite demonstrates optimal antimicrobial effects below pH = 4 which recommend its use in high acid food systems such as fruit juices.

Water waste treatment

One of the largest use of sodium sulfite is in water and wastewater treatment plants, where its application is to react with and neutralize excess chlorine used in the water and wastewater treatment processes.

Sodium Sulfite in photography.

it is used in the developing process, and it acts as a preservative for the final picture produced.

Sodium sulfite in Swimming pool

Sodium sulfite another application is in swimming pools to decrease the chlorine levels in the water.

Sodium sulfite as oxygen scavenger

The purpose of an oxygen scavenger is to limit the amount of oxygen available for deteriorative reactions that can lead to reduced functionality of many types of products, from pharmaceuticals to metals, to food This product is used in steam boiler water treatment to remove dissolved oxygen and to remove excess chlorine from wastewater. In boiler systems, this compound works as an oxygen scavenger to protect the system from pitting corrosion. so the water fed to boilers is often treated with sodium sulfite.

Sodium sulfite in textile industry

The textile industry makes extensive use of Na2SO3 for bleaching, dechlorinating and desulfurizing purposes.

Sodium sulfite in purifying trinitrotoluene

Sodium sulfite is also used in the process of purifying trinitrotoluene (TNT) in order to make it fit for military use.


It is a useful agent in many drugs, which helps maintain their potency and stability.




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