Soda, Synthesized Common
Soda ash is the common name for technical grade sodium carbonate. It is a odorless, white powder that has an alkaline taste. It is represented by the molecular formula Na2CO3. It has a melting point of 93.2°F (34°C).
Soda ash was one of the earliest manufactured chemicals. Ancient peoples produced soda ash by pouring water through burned plants and then evaporating the water from the resulting mix. This soda was used for making both glass and soap.
The chemical industry expanded during the 1700s, producing ever-increasing amounts of glass, soaps, and textiles, all of which required common soda. Soda derived from plants was expensive and could not keep up with the demand, especially when sources of supply were disrupted by frequent wars. A number of chemists experimented with ways to produce soda from alternative sources. The French Academy of Sciences, intent on spurring industrial growth, offered a monetary prize around 1775 for the best method of producing sodium carbonate from common salt (sodium chloride).
In response to the Academy's competition, the French physician and chemist Nicolas Leblanc developed a usable method of treating salt from seawater with sulfuric acid to produce sodium sulfate, which was then heated with limestone and charcoal to produce soda ash and calcium sulfide. Leblanc received a patent for his process in 1791 and won the Academy's prize which, however, was never paid. His efforts to establish a factory to produce soda ash were destroyed by the French revolutionary government. The Leblanc process was finally used commercially in England in the 1820s and soon became the industrial standard worldwide.
Although Leblanc's process did produce artificial soda in large quantities for industry, it had its drawbacks. Sulfuric acid was expensive at first, and the byproducts of the process were both pollutants and difficult to find uses for. Chemists turned their attention to the possibilities of extracting soda from sodium chloride with ammonia. They noted that when ammonia and carbon dioxide gas act on sodium chloride, sodium bicarbonate and ammonium chloride are formed. Simple heating of the bicarbonate produces sodium carbonate--common soda--and lime decomposes the ammonium chloride to ammonia, which can then be used to start the reaction again.
Around 1810, chemists from France, Germany, and England were attempting to find a practical means of exploiting the ammonia-soda cycle. Unaware of these chemists' efforts, Ernest Solvay of Belgium devised a feasible way to use the ammonia-soda cycle on a commercial scale in 1861. He designed metallic towers that allowed large amounts of gas to mix with the salt and ammonia solution, producing large amounts of soda; this method was able to recover 99 percent of the expensive ammonia for reuse. Solvay's factory in Couillet, Belgium, began producing commercial amounts of synthetic soda ash in 1865. Ludwig Mond (1839-1909), a German-born English chemist, improved Solvay's process in the 1870s. Today, the Solvay process remains in use to produce most of the world supply of soda ash.
Natural soda ash is mined and purified from deposits in ancient lakes and seas. Salt electrolysis--the breaking down of sodium chloride into its elements by electric current--is being developed as an alternative to the Solvay process for producing synthetic soda.
Soda ash is used in the production of a variety of products including soap, glass, and textiles, as well as wood pulp, paper, and water softeners. In 1996 demand for soda ash in the United States was at 7.1 million tons.
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