A Comprehensive Guide to Sodium Sulfate
Sodium sulfate (Na2SO4), also called disodium sulfate, is used widely as an industrial chemical. It is an inorganic compound whose main ingredients are Sodium (Na) and Sulfur (S), and it occurs naturally as Thenardite. It can be created as a byproduct during certain industrial chemical processes, but even as a “waste” product, sodium sulfate is very useful.
Naturally Occurring Sodium Sulfate
Sodium sulfate occurs naturally over millions of years of igneous rock erosion. When these rocks are gradually eroded by friction, the sodium content of the rocks is carried by water and eventually collects in natural basins, where it reacts with sulfur, which normally comes from eroding iron pyrite, volcanic sources or beds of gypsum. This chemical reaction produces a precipitate, which is sodium sulfate. This mineral, which collects in crystalline deposits, was named Thenardite, in honor of Louis Thenard, a French chemist. It tastes salty and dissolves in water.
History of Use by Humans
Thenardite is one name for the natural sodium sulfate mineral, but it is also known as Glauber’s Salt, after the Dutch-German chemist, Johann Glauber, who isolated it from Austrian spring water in 1604. He named it sal mirabilis (miraculous salt), because it had excellent applications as a generalized laxative. Although it is still used as a laxative in some stronger preparations, the use of this substance has fallen by the wayside in pharmaceuticals with the discovery of other, less harsh, compounds. Now, sodium sulfate is used in large-scale manufacturing.
Sources of Sodium Sulfate
Sodium sulfate can be found plentifully in nature. It is obtained from Searles Lake, California; the Great Salt Lake in Utah; and various sources in Nevada, Wyoming, and Washington State. Internationally, Mexico, China, South Africa, China and several other nations have significant sodium sulfate deposits. The US currently imports more naturally-occurring sodium sulfate than it mines, because the imported compounds are so much cheaper than the process of developing and mining the domestic sites.
Manufactured Sodium Sulfate
Sodium sulfate is often produced as a waste or byproduct during several industrial chemical processes. Manufacturing rayon, recycling battery acids, production of ascorbic and hydrochloric acids, cellulose and flue gas desulfurization are only a few of the processes which create sodium sulfate. The US generates about half of its domestically-produced sodium sulfate in this manner.
Uses for Sodium Sulfate
This waste or byproduct has many commercial and industrial applications. It is often used as a “filler” in powdered and liquid detergents and soaps, but has important uses in glassmaking, the manufacture of wood pulp products and paper, and the production of textiles and fabrics. Sodium sulfate is also used as a laboratory drying agent, a window de-frosting ingredient, during starch production, in carpet cleaners, and even as an additive to cattle feed. One interesting application for the compound is in solar panels as a passive heat storage medium.
Physical and Environmental Impact
Although sodium sulfate is classified as non-toxic and has no strict regulations for handling stipulated by the MSDS, sodium sulfate can be an irritant to the lungs, causing asthma-like symptoms, and can cause pain and irritation of the mucous membranes, especially the eyes and mouth. Handling with gloves and goggles is recommended. It also doesn’t represent a significant environmental risk, according to the MSDS, not displaying bioaccumulation properties, unlike its close cousins, sodium lauryl and sodium laureth sulfates, both of which are used similarly.
As an industrial chemical, sodium sulfate is extremely versatile as well as inexpensive to produce. Its use has declined in recent years, as the trend in detergents and soaps has now shifted to concentrated liquids instead of bulky powders, which use more of this filler-type compound. However, it still has wide applications in other industries and will continue to be used in other, more innovative processes.