What Is Sodium Sulfate?
Sodium sulfate is a salt of sodium sulfate and sodium hydroxide with the chemical formula Na2SO4.
It is also called glauber’s salt. When distinguishing it from the anhydrous salt (Na2SO4・10H2O), Na2SO4 is called anhydrous glauber’s salt, while the anhydrous salt is called crystalline glauber’s salt.
Uses of Sodium Sulfate
Sodium sulfate is widely used as a food additive, pharmaceutical, reagent, and for industrial purposes because it is nonflammable and has almost no harmful effects on the human body. For industrial use, it is used as one of the raw materials for manufacturing glass and pulp, and as a raw material for producing sodium sulfide. Its high hygroscopicity can also be used as a desiccant.
For household products, it is used as an auxiliary agent (builder) to improve the cleaning power of neutral detergents, and as a raw material for bath salts. Other uses include mining and smelting, dyeing, dye intermediates, pharmaceuticals, and the manufacture of precipitable barium sulfate.
Properties of Sodium Sulfate
Sodium sulfate comes in two forms: decahydrate (Na2SO4・10H2O) and anhydrate (Na2SO4), both of which are hydrous salts.
1. Crystalline Glauber’s Salt (Na2SO4・10H2O)
Molecular weight is 322.21 and specific gravity is 1.46. It is well soluble in water, and at 32.4℃, it changes from decahydrate to anhydrous. its solubility in water increases with increasing temperature up to 32.4℃, but above 32.4℃, solubility decreases with increasing temperature.
It is soluble in glycerin, insoluble in alcohols, and fats soluble.
2. Anhydrous Glauber’s Salt (Na2SO4)
Molecular weight is 142.04 and specific gravity is 2.698. Its melting point is 884°C. It is soluble in glycerin and insoluble in alcohols. It appears as a colorless or white, crystalline or crystalline powder solid.
It is characterized by high hygroscopicity and mixing or contact with aluminum and magnesium should be avoided.
Other Information on Sodium Sulfate
How Sodium Sulfate Is Produced
Sodium sulfate is produced directly from nature. It is produced in the United States and China as crystalline glauber’s salt and condensed salt (a mixture of sodium sulfate and calcium sulfate).
In industry, sodium sulfate is generally produced by refining low-purity sodium sulfate, a byproduct of the manufacture of rayon and other industrial products, to produce high-purity sodium sodium sulfate. The raw materials used are glauber’s salt, which is a byproduct of rayon production, and glauber’s salt byproduct, which is a byproduct of other industrial products.
When using glauber’s salt, soda ash is added to glauber’s salt to neutralize excess sulfuric acid, which is then heated and concentrated to precipitate sodium sulfate. This is further dehydrated, dried, and pulverized to refine the sodium sulfate.
1. Rayon
Cellulose + NaOH → Viscose
Viscose + H2SO4 → Viscose rayon + Na2SO4
Cellulose is dissolved in sodium hydroxide to make viscose. Viscose rayon is produced by precipitating the viscose solution in dilute sulfuric acid in fibrous form. Sodium sulfate is produced during this neutralization reaction. The residue after the fibers are recovered is rayon glauber’s salt.
2. Production of Sodium Dichromate
2Na2CrO4 + H2SO4 → Na2Cr2O7 + Na2SO4 + H2O
3. Production of Ammonium Perchlorate
(NH4)2SO4 + 2NaClO4 → 2NH4ClO4 + Na2SO4
4. Production of Boric Acid
Na2B4O7 + H2SO4 + 5H2O → 4H3BO3 +Na2SO4
5. Production of Formic Acid
2HCOONa + H2SO4 → 2HCOOH + Na2SO4