Nicolas Leblanc
1742?-1806
French Surgeon and Chemist
Although trained as a physician and surgeon, Nicolas Leblanc is best known for his discoveries as an industrial chemist. In this role, he developed the Leblanc process of making soda ash (sodium carbonate) from common salt. Because of the wide variety of uses for soda ash, including making soap, glass, paper, and more, this became one of the most important chemical processing innovations of the eighteenth century.
Nicolas Leblanc was the son of an iron works director, probably born in 1742. He attended medical school, earning sufficient distinction to be named the private physician to the Duke d'Orleans at the age of 38. Intrigued by a competition sponsored by the French Academy in 1775, Leblanc became interested in the problem of making soda ash from common salt. At that time, the only source of this important chemical was by extracting it laboriously from wood ash or seaweed ash, or by mixing these ashes with whatever material required the soda ash for processing. One example of this is soap, which was often made by mixing lye (sodium hydroxide) or animal fat with wood ashes. However, the impurities present in the ash made this method less than desirable for many applications. The only source of high-purity soda ash was in some desert lakes, called soda lakes, or in some mineral deposits formed from soda lakes long ago.
French scientists suspected that, since both common salt (sodium chloride) and soda ash were both sodium compounds, it might be possible to change the one into the other cheaply and efficiently. However, five years after the competition began, this still had not been accomplished.
The Leblanc process consisted of treating salt with sulfuric acid to make salt cake (sodium sulfate). The salt cake was then mixed with limestone (calcium carbonate) and coal (primarily carbon) to form a black substance containing mostly sodium carbonate (soda ash) and calcium sulfide. Since the soda ash was soluble and the calcium sulfide was not, mixing this with water would dissolve the soda ash, which would then be recovered by boiling off the water or allowing the mixture to dry. Compared with previous methods, the Leblanc process was very simple and inexpensive.
The Leblanc process was a significant step forward in industrial chemistry because of the widespread use of soda ash. Purer soap became much less expensive and available to many more people. Glass also became cheaper and of higher quality because of the lesser quantity of impurities in soda ash produced by the Leblanc process. Soda ash is also used in paper manufacturing, ceramics production, petroleum refining, for water softeners, as a cleaning and degreasing agent, and as a process chemical in the manufacture of other chemicals containing sodium.
Although Leblanc won the award offered by the French Academy, he never collected on his prize because the French Revolution had begun by the time he completed his work. Nevertheless, he went on to construct a factory to manufacture large amounts of soda ash, only to have it seized by Revolutionary leaders in 1793. It was returned to him by Napoleon in 1802 but, lackingthe money to resume his business, he was unable to run the factory. Depressed and disheartened by these setbacks, Leblanc committed suicide in 1806.
Although Leblanc's life ended tragically, his process was already widespread by the time of his death and continued to be used quite widely for nearly a century, until being replaced by the less expensive Solvay process. Today, approximately seven million tons of soda ash are used annually in the U.S. alone, giving an idea of the continuing importance of this chemical in modern life.
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