Leblanc Develops Soda Production

Instead of using organic sources, Leblanc discovered an artificial method of making soda (sodium carbonate) from salt (sodium chloride), and his method led to widespread use of soda in industries making soap, glass, and paper, as well as in the bleaching and dyeing industries.

Summary of Event

From antiquity, the compound now known as sodium carbonate was important to alchemists as a reactive alkali and to artisans for its role in making such substances as glass. It was found as a mineral, natron, in desert regions, and it could also be made from the ashes of seaweed or the barilla plant. During the medieval period, other alkaline substances were discovered, but by the eighteenth century soda, or “soda ash,” had become the alkali with the greatest practical value, because it was essential to the manufacture of glass, paper, and soap, and it was also used in bleaching Bleaching of textiles and dyeing. Dyes France obtained most of its soda from Spain, where the coastal barilla plants were harvested and burned to an ash rich in soda. However, this soda was expensive, varied in quality, and was subject to blockade during conflicts. [kw]Leblanc Develops Soda Production (1789)
[kw]Soda Production, Leblanc Develops (1789)
Soda production
Sodium carbonate
[g]France;1789: Leblanc Develops Soda Production[2790]
[c]Chemistry;1789: Leblanc Develops Soda Production[2790]
[c]Science and technology;1789: Leblanc Develops Soda Production[2790]
[c]Manufacturing;1789: Leblanc Develops Soda Production[2790]
[c]Environment;1789: Leblanc Develops Soda Production[2790]
Leblanc, Nicolas
Orléans, duc d’
Dizé, Michel Jean Jacques

Because French industries were increasingly dependent on vulnerable supplies of soda, the French Academy of Sciences, Academy of Sciences, France in 1775, announced a substantial monetary prize to be given to the person who invented a commercial process for making soda from common salt. This prize caught the attention of Nicolas Leblanc, a physician with an interest in chemistry who was then employed by the duc d’Orléans, an aristocrat who was willing to support Leblanc’s chemical research.

Contrary to what some scholars have described as the “Leblanc legend,” Leblanc was not the first person to convert salt into soda. Other chemists had discovered more than a dozen laboratory procedures to bring about this important conversion. Furthermore, before Leblanc set up his factory, several small industries were actually making artificial soda, but this soda was expensive, and it was not economically competitive with imported natural soda. Leblanc’s achievement was to find an efficient method of making artificial soda that was able to outcompete its barilla-based manufacture in quantity, quality, and price.

Scholarly consensus exists that Leblanc began work on the “soda problem” in the 1780’s, but disagreements exist over precisely when his work started and when he actually discovered his new process. In his patent application Leblanc stated that he began his research in 1784. Since no evidence in his personal and published papers exists to support this date, some scholars have cast doubt on this early date, preferring instead a time in the late 1780’s. J. R. Partington, the distinguished historian of chemistry, thinks that Leblanc discovered his process in 1787, but many scholars choose 1789 as a date “beyond dispute,” since Leblanc definitely made soda crystals by his new method in that year.

Controversy also exists about who actually made the discovery and how it was made. According to Leblanc, he got the idea for his method by reading about a trip that a French journalist made to England and Scotland to study their industries. This journalist, Jean Claude Delamétherie, who edited a physics journal, reported, albeit erroneously, on how the British were manufacturing soda. This discussion occurred after his description of British ironmaking. Some scholars think that this serendipitous juxtaposition of garbled chemical reactions helped Leblanc arrive at his idea about the use of limestone and coal to transform salt into soda.

In the late 1780’s, while still in the employ of the duc d’Orléans, Leblanc used the laboratory facilities of the Collège de France in Paris to repeat the work of earlier researchers. He reacted common salt with concentrated sulfuric acid to form what he called “salt-cake” (sodium sulfate). He then went beyond the work of others by finding how to make soda from this salt-cake. He did this by using a furnace to heat a crucible containing the salt-cake and a mixture of powdered coal and limestone (calcium carbonate). This reaction resulted in what he called “black ash” (today we know it was a mixture of sodium carbonate and calcium sulfide, along with unreacted coal and limestone). He obtained the desired soda from the black ash by using water to dissolve the soda (the other materials were insoluble). Evaporation of the solution left him with “white ash,” which turned out to be soda (sodium carbonate).

The French Revolution was under way while Leblanc, with the assistance of Michel Jean Jacques Dizé, completed his research. Since the duc d’Orléans, the funder of this research, had fled to England, Leblanc and Dizé traveled there in October of 1789 to discuss the commercialization of their artificial soda process. On February 12, 1790, Orléans and his agent, along with Leblanc and Dizé, signed an agreement whose principal provisions were that Leblanc would patent his soda-making process and Orléans would furnish 200,000 livres to enable Leblanc and Dizé to set up a factory to start manufacturing soda. On March 27, 1790, Leblanc deposited a document that included a detailed description of his process with a notary in Paris (this document, discovered in 1856, clearly established Leblanc’s priority over Dizé).

In 1791, with money supplied by Orléans, Leblanc built a pilot plant at Saint Denis, north of Paris. The Committee of Public Safety Committee of Public Safety (France) allowed him to obtain a secret patent for his process on September 25, 1791. In scaling up his process from the laboratory to the factory level, Leblanc built three furnaces, the first to make salt-cake, with a chimney to convey a poisonous by-product, hydrogen chloride gas, into the atmosphere. On the site, a horse-driven mill pulverized coal and limestone for use in the second furnace, where the reaction producing the black ash took place. With water, he leached out the soda, which the final furnace evaporated into soda ash.

In his plans, Leblanc hoped that this factory would produce 275,000 pounds of soda annually, but throughout its early years it averaged only a bit more than 10 percent of this theoretical amount. On January 28, 1794, political authorities confiscated the plant and made the details of the Leblanc process public. This nationalization of the plant failed to solve France’s soda shortage, and it led to the economic devastation of Leblanc and his family. Leblanc had already become disheartened when the duc d’Orléans, who had returned to France under the name of Philippe Égalité, was guillotined on November 6, 1793. Even though Napoleon Bonaparte returned the factory to Leblanc in 1802, Leblanc was never able to raise the capital to make it a successful enterprise. Burdened with financial problems and desperate to shock the authorities into granting his family the rewards that the state had previously promised him, he shot himself through the head in 1806. Unfortunately, his family’s troubles continued, and, to make matters worse, Dizé began making claims that he, not Leblanc, was the real inventor of the process. Based on a study of various documents, modern scholars have declared the contention of Dizé and his family spurious, and Leblanc has been posthumously recognized as the true inventor of the process that is now inextricably tied to his name.


James Muspratt, an important nineteenth century English chemical manufacturer, once wrote that the Leblanc process had a greater impact on society, commerce, and chemical technology than any other discovery. Although evaluations of the Leblanc process’s significance by modern historians of technology are less sweeping than Muspratt’s, they nevertheless recognize the great influence of his method in facilitating the development of many modern chemical industries. Within a generation of Leblanc’s death, his method had proved its worth and, especially after the remission of the salt tax, its economic profitability.

The process quickly spread to England and other European countries, where soda was sold in ever-increasing amounts to the textile and soap industries. Soap manufacture Inexpensive soap resulted in its increased use, with concomitant health benefits, for example, a decline in infant mortality. On the other hand, the multiplication of soda plants increased environmental degradation, especially because of the vented hydrogen chloride gas. Air pollution;hydrogen chloride So severe were the problems in England that an Alkali Act Alkali Act (1863) was promulgated in 1863 that required factories to recover and not release their hydrogen chloride.

Despite these and other problems, the Leblanc process dominated the industrial production of soda for nearly a century, when it was replaced by a more efficient method developed by Ernest and Alfred Solvay in Belgium. The last Leblanc soda works closed in 1923, but the sodium carbonate that it and many other factories had produced spurred the growth of important industries that were vital in creating our modern technological society.

Further Reading

  • Brock, William H. The Chemical Tree: A History of Chemistry. New York: Norton, 2000. This reissue of a book originally published in England as The Fontana History of Chemistry makes available to American readers the best thematic history of chemistry. Brock discusses the Leblanc process in chapter 8, “Chemistry Applied to Arts and Manufactures.” Extensive bibliographical essay for each of the chapters. Index.
  • Gillispie, Charles C. “The Discovery of the Leblanc Process.” Isis 48 (1957): 152-170. This article by a distinguished historian of science seeks to demythologize traditional accounts of how Leblanc made (and suffered from) his discovery. Extensive footnotes with references to primary and secondary sources.
  • Hall, Nina, ed. The New Chemistry. New York: Cambridge University Press, 2000. Although this book’s emphasis is on twentieth century developments, Colin Russell, in his chapter on “Chemistry in Society,” analyzes the Leblanc process and its social impact on the nineteenth century. Each of the chapters ends with a further reading section. Index.
  • Partington, J. R. A History of Chemistry. Vol. 3. Reprint. New York: Martino, 1996. Chapter 11 contains a section on “The Leblanc Process” in which Partington, basing his treatment largely on original sources, gives a factual rather than analytic account of Leblanc and the development of his process. Name and subject indexes.

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