Sodium sulfate 1

Sodium sulfate is an important chemical raw material. It is the main raw material for producing sodium sulfide, sodium silicate, and other chemical products. It can also be used as a filler in synthetic detergents and a cooking agent in the paper industry when manufacturing sulfate pulp. Sodium sulfate is also known as yuanming powder, anhydrous mirabilite, and anhydrous pyroclastic salt. It is a white monoclinic fine crystal or powder. Its relative density is 2.68 and its melting point is 884℃. It dissolves in water and the aqueous solution is neutral. It dissolves in gasoline but does not dissolve in ethanol. When exposed to the air, it easily absorbs moisture and becomes hydrated sodium sulfate. It is a homogeneous multi-crystalline substance. At a temperature of 32.4 to 223℃, it is rhombic, and at higher temperatures, it forms monoclinic crystals. At 241℃, it transforms into hexagonal crystals. When crystallizing from a solution, it has affinity for iron, iron compounds, and various organic substances. High-purity, fine-grained anhydrous sodium sulfate is called yuanming powder.
There are two hydrates of sodium sulfate: one is sodium sulfate heptahydrate Na2SO4·7H2O, which is a white regular hexagonal or tetragonal crystal, losing water at 24.4℃. The other is sodium sulfate decahydrate Na2SO4·10H2O, commonly known as mirabilite, yuanming powder, or insurance powder. It is a colorless monoclinic crystal with a density of 1.464g/cm3 and a melting point of 32.38℃. It loses water at 100℃ to become anhydrous sodium sulfate and is easily soluble in water. It easily dehydrates in dry air to become anhydrous white powder. Sodium sulfate can be used as a chemical analysis reagent, such as for the determination of dyes, used as a mordant in the printing and dyeing industry, used to manufacture sodium sulfide, glass, sodium silicate, porcelain glaze, quantitative nitrogen measurement, and paper pulp. In medicine, it is used as a diuretic, laxative, and antidote for barium salt poisoning. Sodium sulfate crystals precipitate in salt ponds in winter. Naturally occurring sodium sulfate minerals are widely distributed and are mostly magnesium (calcium) sulfate compounds and mirabilite. Industrially, sodium sulfate is mainly obtained by separating natural minerals or by dehydrating mirabilite and treating sodium chloride with sulfuric acid. Sodium sulfate is also a by-product in many chemical production departments and is extracted from the waste liquid produced in the production of viscose fibers and glass paper. In the production of chromium sulfate, phenol, boric acid, lithium carbonate, and certain pigments, there are also by-products of sodium sulfate. Sodium sulfate has another characteristic of being prone to form supersaturated solutions. The main use of sodium sulfate is as an important raw material for manufacturing glass and paper. It is the largest in usage in the paper and cellulose industries, accounting for about 70% of the total. Sodium sulfate is a component of synthetic detergents, it is a neutral salt, and adding it can reduce surface tension and increase the solubility of the detergent. It is also a diluent for dyes and a dyeing and printing aid. It is used as a promoting dye for direct dyes, sulfurized dyes, and reducing dyes for cotton fibers, and as a retardant for direct dyeing of silk. In the chemical industry, sodium sulfate is used as a raw material for manufacturing sodium sulfide, gypsum, sodium silicate, and other chemical products. Methods for manufacturing sulfuric acid, sulfur, soda ash, ammonium sulfate, and other products using sodium sulfate have been studied, but these methods have not yet been widely applied due to high costs. Sodium sulfate is commonly used in laboratories to make cold remedies. Mirabilite is used as a laxative in medicine. Most of the sodium sulfate in the body is retained in the gastrointestinal tract and is not absorbed, maintaining a certain osmotic pressure, which can increase intestinal volume and cause intestinal peristalsis, having a laxative effect. Sodium sulfate is an antidote for barium and lead poisoning. When lead poisoning occurs, washing the stomach with 10% mirabilite or orally taking 1-2% sodium sulfate solution can be used.