Soda ash

Where Found

While soda ash can be manufactured from salt, it can also be found in nature in the form of deposits of the minerals trona (Na₂CO₃·NaHCO₃·2H_2DO) and natron (Na₂CO₃·10H₂O) and in alkaline brines associated with dry lakes. Soda ash is mined from large natural trona deposits in Wyoming and recovered from lake brines in California. It is also produced from natural deposits in South America, Africa, China, Russia, Europe, and India. In 2023, leading producers of soda ash were the United States and Turkey.

Primary Uses

One of the most fundamental industrial chemicals, soda ash is used in the manufacture of glass, chemicals, soaps and detergents, and paints. It is also used in processing wood pulp to make paper, refining aluminum, desulfurizing pig iron, purifying petroleum, and softening water.

Technical Definition

Soda ash (also known as soda) is a commercial term for the chemical compound sodium carbonate (Na₂CO₃). Its average molecular weight is 105.99. Pure soda ash is a white, odorless powder that is hygroscopic (absorbs moisture from the air) and that forms a strongly alkaline water solution (a 1 percent aqueous solution has a pH of 11). Its specific gravity is 2.53. It has a melting point of 853° Celsius and decomposes before reaching a boiling point.

Description, Distribution, and Forms

Soda ash, or soda, is an important inorganic chemical used widely in industry. Soda ash is an alkali—that is, it is a caustic substance that dissolves in water to produce a solution with a pH substantially greater than 7. While soda ash can be manufactured from salt, it can also be obtained from naturally occurring sodium carbonate deposits and alkaline lake brines. Soda ash is one of the most fundamental industrial chemicals and is an essential part of many industrial processes. Total world production of soda ash is approximately 65 million metric tons; the United States produces nearly one-half of the world total. Soda ash derives its name from the earliest method for producing the substance: sea plants were burned, their ashes were boiled with water, and the resulting solution was allowed to evaporate, leaving behind sodium carbonate.

Soda ash is found in nature in the form of deposits of hydrated sodium carbonate minerals such as trona and natron and in alkaline brines associated with dry lakes. Most of the world’s supply of natural soda ash comes from the Green River region of southwest Wyoming, the largest known deposit of trona. These trona beds were deposited approximately 50 million years ago in the early to mid-Eocene epoch. The Green River basin is estimated to contain 115 billion metric tons of trona deposits. In California, soda ash is recovered from lake brines at Searles Lake in San Bernardino County and at Owens Lake in Inyo County.

Trona, the from which soda ash is commonly obtained, is a white or yellow-white found as a powder on the soil surface or in fibrous or columnar layers and thick beds in saline residues. Trona deposits are formed by the drying of alkaline bodies of water in arid regions. Soda ash is also found in brines and in saline lake water.

History

Soda ash has been used since the days of the earliest Egyptian dynasties. The first glass containers made with it were produced by Egyptians around 3500 BCE. Natron from the dry lakes of the Wadi Natrun, a valley in Egypt, was used as a drying agent in mummification; it may also have been mixed with malachite to create a blue glaze. In his Meteorology, Aristotle describes how Umbrians in the fourth century BCE produced soda ash from the ashes of reeds and rushes. Four centuries later, the Roman historian Pliny the Elder writes of soda ash being used in glass, in medicines for colic pains and skin disorders, and in breadmaking. Plant ash remained an important source of soda ash for manufacturing glass and soap until the early nineteenth century.

In 1791, French chemistNicolas Leblanc developed a commercial process for making soda ash from salt; however, the French Revolution impeded the development of the process, and more than thirty years passed before the process became a commercial success in Liverpool, England. The Leblanc process, which played an important role in the Industrial Revolution, involved decomposing salt with sulfuric acid to produce sodium sulfate and hydrochloric acid, then heating the sulfate with coal and to yield soda ash. In the early 1860s, Belgian industrial chemist Ernest Solvay and his brother Alfred developed another method for producing soda ash from salt, coke, and limestone, using ammonia as a catalyst. The Solvay process, which remains an important part of modern industry, came to provide most of the soda ash used commercially; however, by the late twentieth century, antipollution legislation and the high cost of energy, labor, and materials associated with the process had made natural deposits the preferred source of soda ash for the United States.

Obtaining Soda Ash

Natural soda ash is commonly obtained from trona, with approximately 2 metric tons of trona producing 1 metric ton of soda ash. Some soda ash is also produced from brines and by electrolytic methods. Soda ash can be synthesized using the Solvay process, in which soda ash is manufactured from salt, ammonia, carbon dioxide, and limestone. The limestone is heated to produce quicklime and carbon dioxide; the carbon dioxide is dissolved in a solution of water, ammonia, and salt; and sodium bicarbonate precipitates and is filtered out, dried, and heated to form soda ash.

Uses of Soda Ash

A fundamental industrial chemical, soda ash is used in the manufacture of glass, ceramics, glazes, enamels, chemicals, soaps and detergents, and paints. It serves as a in assaying and as a cleansing agent. It is also used in processing wood pulp to make paper, refining aluminum, desulfurizing pig iron, purifying petroleum, and softening water.

Bibliography

Dyni, John R., and Richard W. Jones. Proceedings of the First International Soda Ash Conference: Utilization of Natural Resources of Sodium Carbonate into the Next Century. Laramie: Wyoming State Geological Survey, 1998.

Garrett, Donald E. Natural Soda Ash: Occurrences, Processing, and Use. New York: Van Nostrand Reinhold, 1992.

Jensen, Mead L., and Alan M. Bateman. Economic Mineral Deposits. 3d ed. New York: Wiley, 1979.

Kogel, Jessica Elzea, et al., eds. “Soda Ash.” In Industrial Minerals and Rocks: Commodities, Markets, and Uses. 7th ed. Littleton, Colo.: Society for Mining, Metallurgy, and Exploration, 2006.

Rahimpour, Hamed, Ahmad Fahmi, and Sahar Zinatloo-Ajabshir. "Toward Sustainable Soda Ash Production: A Critical Review on Eco-Impacts, Modifications, and Innovative Approaches." Results in Engineering, vol. 23, Sept. 2024, doi.org/10.1016/j.rineng.2024.102399. Accessed 6 Jan. 2025.

Royal Society of Chemistry. Sodium Carbonate: A Versatile Material. London: Author, 2000.U