Sodium sulfite – صنایع شیمیایی فرتاش

Sodium sulfite

Sodium sulfite (sodium sulphite) is the inorganic compound with the chemical formula Na₂SO₃. A pale yellow, water-soluble solid, it is used commercially as an antioxidant and preservative. A heptahydrate is also known but it is less useful because of its greater susceptibility toward oxidation by air.

Preparation

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 upon cooling.

SO₂ + 2 NaOH → Na₂SO₃ + H₂O

Sodium sulfite is made industrially by treating sulfur dioxide with a solution of sodium carbonate. The overall reaction is:

SO₂ + Na₂CO₃ → Na₂SO₃ + CO₂

Applications

Sodium sulfite is primarily used in the pulp and paper industry.

As an oxygen scavenger agent, it is used to treat water being fed to steam boilers to avoid corrosion problems, in the photographic industry, it protects developer solutions from oxidation and (as hypo clear solution) to wash fixer (sodium thiosulfate) from film and photo-paper emulsions

As a reducing agent it is used in the textile industry as a bleaching, desulfurizing, and dechlorinating agent (e.g. in swimming pools). Its reducing properties are exploited in its use as a preservative to prevent dried fruit from discoloring, and for preserving meats.

It is used as a reagent in sulfonation and sulfomethylation agent. It is used in the production of sodium thiosulfate.

Reactions

Heptahydrate

If sodium sulfite is allowed to crystallize from aqueous solution at room temperature or below, it does so as a heptahydrate. The heptahydrate crystals effloresce in warm dry air. Heptahydrate crystals also oxidize in air to form the sulfate. The anhydrous form is much more stable against oxidation by air.

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Category: sulfates Tags: Fartash, Sodium hydroxide

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Sodium Tetraborate

Borax, also known as sodium borate, sodium tetraborate, or disodium tetraborate, is a compound with formula Na ₂H₄B₄O₉•nH₂O or, more precisely, [Na•(H₂O)⁺_m]₂ [B₄O₅(OH)²⁻₄].

The formula is often improperly written as Na ₂B₄O₇•(n+2)H₂O, reflecting an older incorrect understanding of the anion's molecular structure. The name may refer to any of a number of closely related boron-containing mineral or chemical compounds that differ in their water of crystallization content. The most commonly encountered one is the octahydrate Na ₂H₄B₄O₉•8H₂O or [Na(H₂O)⁺₄]₂ [B₄O₅(OH)²⁻₂] (or Na₂B₄O₇•10H₂O, the "decahydrate", in the older notation). It is a colorless crystalline solid that dissolves in water.

Borax is a component of many detergents, cosmetics, and enamel glazes. It is used to make buffer solutions in biochemistry, as a fire retardant, as an anti-fungal compound, in the manufacture of fiberglass, as a flux in metallurgy, neutron-capture shields for radioactive sources, a texturing agent in cooking, as a cross-linking agent in slime, as an alkali in photographic developers, as a precursor for other boron compounds, and is useful as an insecticide (similarly to boric acid).

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Sodium Hydrosulfite

Sodium dithionite (also known as sodium hydrosulfite) is a white crystalline powder with a weak sulfurous odor. Although it is stable in the absence of air, it decomposes in hot water and in acid solutions.

Structure

Raman spectroscopy and single-crystal X-ray diffraction studies reveal that the geometry of the dithionite anion is flexible. The dithionite dianion has C ₂ symmetry, with almost eclipsed with a 16° O-S-S-O torsional angle. In the dihydrated form the dithionite anion has a shorter S-S bond length and a gauche 56° O-S-S-O torsional angle.

A weak S-S bond is indicated by the S-S distance of 239 pm. Because this bond is fragile, the dithionite anion dissociates in solution into the [SO₂]⁻ radical anion, as has been confirmed by EPR spectroscopy. It is also observed that ³⁵S undergoes rapid exchange between S₂O₄²⁻ and SO₂ in neutral or acidic solution, consistent with the weak S-S bond in the anion.

Sodium dithionite is produced industrially by reduction of sulfur dioxide. Several methods are employed, including reduction with zinc powder, sodium borohydride, and formate. Approximately 300,000 tons were produced in 1990.

Solid paraffin

Paraffin wax (or petroleum wax) is a soft colorless solid derived from petroleum, coal or shale oil that consists of a mixture of hydrocarbon molecules containing between twenty and forty carbon atoms. It is solid at room temperature and begins to melt above approximately 37 °C (99 °F), and its boiling point is above 370 °C (698 °F). Common applications for paraffin wax include lubrication, electrical insulation, and candles; dyed paraffin wax can be made into crayons. It is distinct from kerosene and other petroleum products that are sometimes called paraffin.

Un-dyed, unscented paraffin candles are odorless and bluish-white. Paraffin wax was first created by Carl Reichenbach in Germany in 1830 and marked a major advancement in candlemaking technology, as it burned more cleanly and reliably than tallow candles and was cheaper to produce.

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Phosphoric acid, also known as orthophosphoric acid or phosphoric(V) acid, is a weak acid with the chemical formula H₃PO₄. It is normally encountered as a colorless syrup of 85% concentration in water. The pure compound is a colorless solid.

All three hydrogens are acidic to varying degrees and can be lost from the molecule as H⁺ ions (protons). When all three H⁺ ions are removed, the result is an orthophosphate ion PO₄³⁻, commonly called "phosphate". Removal of one or two protons gives dihydrogen phosphate ion H ₂PO⁻ ₄, and the hydrogen phosphate ion HPO²⁻ ₄, respectively. Orthophosphoric acid also forms esters, called organophosphates.

Phosphoric acid is commonly encountered in chemical laboratories as an 85% aqueous solution, which is a colourless, odourless, and non-volatile syrupy liquid. Although phosphoric acid does not meet the strict definition of a strong acid, the 85% solution can still severely irritate the skin and damage the eyes.

Sulfammon Granular Ammonium Sulfate

Ammonium sulfate [(NH₄)₂ SO₄] was one of the first and most widely used nitrogen (N) fertilizers for crop production. It’s now less common but especially valuable where both N and sulfur (S) are required. Its high solubility provides versatility for a number of agricultural applications.

Production

Ammonium sulfate (sometimes abbreviated as AS or AMS) has been produced for more than 150 years. Initially, it was made from ammonia released during manufacturing coal gas (used to illuminate cities) or from coal coke used to produce steel. Today, manufacturers make it by reacting sulfuric acid with heated ammonia. To get the crystal size best suited for the application, they control the reaction conditions by screening and drying the particles until achieving the desired size. Some materials are coated with a conditioner to reduce dust and caking.

Byproducts from various industries meet most of the current demand for ammonium sulfate. For example, the nylon manufacturing process produces ammonium sulfate as a co-product. In another, certain byproducts that contain ammonia or spent sulfuric acid are commonly converted to ammonium sulfate for use in agriculture.

Although the color can range from white to beige, ammonium sulfate is consistently sold as a highly soluble crystal with excellent storage properties. As described earlier, particle size can also vary depending on the intended purpose.

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Sodium metabisulfite or sodium pyrosulfite (IUPAC spelling; Br. E. sodium metabisulphite or sodium pyrosulphite) is an inorganic compound of chemical formula Na₂S₂O₅. The substance is sometimes referred to as disodium metabisulfite. It is used as a disinfectant, antioxidant, and preservative agent.

Sodium disulfite 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 crystallises upon cooling.

SO₂ + Na₂SO₃ → Na₂S₂O₅

which yields a residue of colourless solid Na₂S₂O₅.

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Hydrogen peroxide is unstable and slowly decomposes in the presence of light. Because of its instability, hydrogen peroxide is typically stored with a stabilizer in a weakly acidic solution in a dark coloured bottle. Hydrogen peroxide is found in biological systems including the human body. Enzymes that use or decompose hydrogen peroxide are classified as peroxidases.

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