Sodium Sulphate

What is Sodium Sulphate

Sodium sulphate with formula Na2SO4 is an inorganic compound,, it is also known as salts of sulfuric acid. White in color and high solubility in water is widely used chemical commodity. It is widely used by chemical industry and is also called as Glaubers salt, in its decahydrate form, known as the mineral mirabilite [discovered by Johann Rudolf Glaubers in 1625]. In its anhydrous form, known as mineral thenardite, it is used as a drying agent in organic synthesis. Anhydrous sodium sulphate occurs in arid environments as the mineral thenardite and it slowly turns to mirabilite in damp air. Generally sodium sulphate is traded in there forms salt cake, Glauber’s salt and niter cake. In areas where the rainfall is very low sodium sulphate is called as white alkali in contrast to sodium carbonate , which is termed as black alkali on account of its corrosive action on vegetation. When the sodium sulphate is form of salt cake, used in the manufacture of wood pulp by the sulphate process, plate glass, window glass. Glauber’s salt is used in the industries involves dyeing, tanning and medicine, treatment of cattle. Niter cake is used as a alternate for sulphuric acid for many purposes as in metal picking, absorbing ammonia and in production of fertilizers Sodium Sulphate is an inorganic solid present in anhydrous and hydrate forms. It is a major commodity chemical widely applied in textile, detergent, glass and paper manufacturing. The demand for sodium sulphate is expected to witness strong growth in the near future. Global sodium sulphate market is expected to show stable growth mainly driven by Asia Pacific (China, Indonesia, India, South Korea, Malaysia, etc.) and Latin America regions (Brazil, Argentina, Mexico). Mexico and Spain were the world’s main producers of natural sodium sulphate with Russia, USA and Canada following after. However in recent years china has been main producer of the same.

Manufacturing Process

Sodium chloride is treated with sulfuric acid in the Mannheim process. This reaction produces sodium sulfate(called the salt cake) and hydrogen chloride: 2 NaCl + H2SO4 → Na2SO4 + 2 HCl Sodium sulfate is an intermediate of the Leblanc process. Sodium sulfate has unusual solubility characteristics in water. Its solubility in water rises more than tenfold between 0 °C to 32.384 °C, where it reaches a maximum of 49.7 g/100 mL. At this point the solubility curve changes slope, and the solubility becomes almost independent of temperature. This temperature at 32.384 °C, corresponding to the release of crystal water and melting of the hydrated salt, serves as an accurate temperature reference for thermometer calibration. About one third of the world’s sodium sulfate is produced as by-product of other processes in chemical industry. Most of this production is chemically inherent to the primary process, and only marginally economical. By effort of the industry, therefore, sodium sulfate production as by-product is declining. However, sodium sulfate is found abundantly as the mineral deposit mirabilite which forms naturally. 

The Uses of Sodium Sulphate

Sodium sulphate plays an important role in reactive dyeing by improving the affinity of the dyestuff towards the fiber, acceleration ofthe dyestuff’s association and lowering its solubility. The presence of gas particle within the common salt might cause corrosion of the instrumentation. Hence, sulfate is usually most popular over common salt.

Detergent
Sodium sulphate is used in powdered detergents as filler because phosphates, which were traditionally used as fillers in powder detergents. Sodium Sulphate is added to change the consistency of the detergent, to make it more pourable, more soluble and to help it disperse evenly. Sodium sulphate is added to make the detergent powder flow freely. Without it, the detergent would stick together and become one big block. Sodium sulphate is widely used as desiccant which are able to bind multiple molecules of water, forming “hydrates”. This effectively locks up any moisture that enters the detergent, maintaining a dry, free-flowing powdered detergent.

Glass
Sodium sulphate is used in making bottle, sheet, and plate glass in order to provide the necessary alkali base and because it is cheaper than soda ash, which is the standard source of alkali. Sodium sulphate prevents scum formation in the molten glass during refining, and also fluxes the glass. Also acts as a fining agent in molten glass, removing small air bubbles and imperfections during the blowing and casting processes. In making glass the several ingredients, such as sand, soda ash, salt cake, coke, and niter, are weighed out in the proper proportions, mixed in mixing machines, and transferred to the pots in furnaces heated by gas. Glassmakers desire salt cake with less than 1 per cent of either sodium chloride or sulphuric acid, less than 0.4 % of iron and aluminium oxide, less than 0.5 % of matter insoluble in water, and less than 0.2 % of magnesium sulphate.

Pulp & Paper
Sodium Sulphate is used in manufacturing of pulp in Kraft process. The sulphate process of reducing wood to pulp is so named because it involves the use of sodium sulphate, but this substance is used only in making the sodium sulphide that is one of the active chemicals in the process, the other being sodium hydroxide. The process might more properly be called the sulphide process. It is used in treating all the long-fibered woods. As a matter of fact, however, sulphate pulp can be more easily bleached than soda pulp. The cost of labour in the sulphate process is slightly higher than in the soda process, on account of the smelting operation; on the other hand, the raw material is cheaper. Salt cake for this process should be ground and should contain at least 95 per cent of anhydrous sodium sulphate.

Commodity Industry
Sodium Sulphate is used in manufacturing of pulp in Kraft process. The sulphate process of reducing wood to pulp is so named because it involves the use of sodium sulphate, but this substance is used only in making the sodium sulphide that is one of the active chemicals in the process, the other being sodium hydroxide. The process might more properly be called the sulphide process. It is used in treating all the long-fibered woods. As a matter of fact, however, sulphate pulp can be more easily bleached than soda pulp. The cost of labour in the sulphate process is slightly higher than in the soda process, on account of the smelting operation; on the other hand, the raw material is cheaper. Salt cake for this process should be ground and should contain at least 95 per cent of anhydrous sodium sulphate.

Product Identification
CAS No.497-19-8
Molecular formulaNa2SO4
SynonymsGlauber’s Salt
H.S. Code2833.11.00
Property
Units
Value
AppearanceWhite powder
Na2SO4%99.2(min)
NaCL%0.2(max)
Insoluble in water%0.2(max)
Feppm20
Water content%0.1(max)