Leblanc process
| Process type | Chemical |
|---|---|
| Industrial sector(s) | Chlor-alkali industry |
| Feedstock | sodium chloride, sulfuric acid, coal, calcium carbonate |
| Product(s) | soda ash, hydrochloric acid |
| Inventor | Nicolas Leblanc |
| Year of invention | 1791 |
| Developer(s) | William Losh, James Muspratt, Charles Tennant |
The Leblanc process was an early industrial process for the production of soda ash (sodium carbonate) used throughout the 19th century, named after its inventor, Nicolas Leblanc. It involved two stages: production of sodium sulfate from sodium chloride, followed by reaction of the sodium sulfate with coal and calcium carbonate to produce sodium carbonate. The process gradually became obsolete after the development of the Solvay process.
Soda ash (sodium carbonate) and potash (potassium carbonate), collectively termed alkali, are vital chemicals in the glass, textile, soap, and paper industries. The traditional source of alkali in western Europe had been potash obtained from wood ashes. However, by the 13th century, deforestation had rendered this means of production uneconomical, and alkali had to be imported. Potash was imported from North America, Scandinavia, and Russia, where large forests still stood. Soda ash was imported from Spain and the Canary Islands, where it was produced from the ashes of glasswort plants (called barilla ashes in Spain), or imported from Syria. The soda ash from glasswort plant ashes was mainly a mixture of sodium carbonate and potassium carbonate. In addition in Egypt, naturally occurring sodium carbonate, the mineral natron, was mined from dry lakebeds. In Britain, the only local source of alkali was from kelp, which washed ashore in Scotland and Ireland.
In 1783, King Louis XVI of France and the French Academy of Sciences offered a prize of 2400 livres for a method to produce alkali from sea salt (sodium chloride). In 1791, Nicolas Leblanc, physician to Louis Philip II, Duke of Orléans, patented a solution. That same year he built the first Leblanc plant for the Duke at Saint-Denis, and this began to produce 320 tons of soda per year. He was denied his prize money because of the French Revolution.
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