Nicolas Leblanc

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Nicolas Leblanc

Nicolas Leblanc (1742-1806) was a French surgeon and chemist who discovered how to manufacture soda from common salt. The "Leblanc process" was key to making soap, glass and other products from soda ash.

Nicolas Leblanc was born on January 6, 1742, in Ivoy-le-Pre, France. His father, a minor official at an iron works, died in 1751. Leblanc was sent to Bourges to live with Dr. Bien, a close family friend. Under the influence of his guardian, Leblanc developed an interest in medicine. When Bien died in 1759, Leblanc enrolled at the Ecole de Chirurgie in Paris to study medicine.

Graduating with a master's degree in surgery, Leblanc opened a medical practice. He married in 1775, and the couple's first child followed four years later. Unable to provide adequately for his family on the medical fees he obtained from his patients, Leblanc in 1780 accepted a position as the private physician to the household of the Duke of Orleans, later known as the revolutionary figure Philippe Egalite.

During this time, the study of chemistry was becoming more popular. Leblanc, having obtained financial stability in a position that allowed him a substantial amount of free time, began conducting experiments. He started with the study of crystallization, primarily because the material required for the experiments was inexpensive. In March 1786 he sent his results to the Academy of Sciences, which recommended that Leblanc "consider the formation of a complete collection of crystallized salts" and that this research be supported by the government. However, because of the turmoil that followed the French Revolution, the Academy was dissolved before its recommendations could be followed.

In 1794 the Committee of Public Instruction offered to support Leblanc's research. However, the chaotic social situation again kept Leblanc from getting his work on a solid footing. Eventually, the Committee on Public Instruction did manage to get public funds to underwrite the publication of Leblanc's crystallization research, detailed in the 1802 work De la Cristallotechnie.

Jean Darcet, the chair of the chemistry department at the College de France, became aware of Leblanc's research in 1786 and suggested Leblanc work on the problem of the production of pure nickel. Not published until 12 years later, the results were relatively insignificant and inconclusive; however, the work is evidence of Leblanc's early interest in industrial chemistry.

The Soda Crisis

Of much greater importance was Leblanc's next project: the creation of soda from non-organic sources. At that time, the main source for soda was wood ashes, and the wood supply in industrial Europe was diminishing. As a result, most of the sodium carbonate that the French glass, textile, and soap industries needed was imported from Spain, at a substantial price. Other markets, such as Russia and North America, were too distant and shipping costs too high to provide a practical solution.

Although soda was already being industrially produced from salt, the process was neither efficient nor cost-effective. The development of an inexpensive method of preparing soda from sea salt—the cheapest and most obvious source—became a national imperative for France. In 1783 King Louis XVI ordered the Academy of Sciences to offer a reward for the invention of an economical method of decomposing sea salt on a large scale. Although the Academy was dissolved before any prize was awarded, the contest was surely an important factor in Leblanc's decision to turn his attention to soda.

Developed the Leblanc Process

Leblanc began his study of the development of sodium carbonate around 1784. After making some progress, Leblanc approached the Duke and requested his financial support. The Duke agreed on the condition that Darcet, a longtime consultant to the Duke, be included in the process. Leblanc was allowed to set up a laboratory at the College of Paris, and Darcet assigned J. Dize, his assistant, to collaborate with Leblanc.

The process by which Leblanc developed sodium carbonate is not known, nor is the exact date. Most likely the method was developed in 1789 after several months of work in the laboratory. After numerous attempts and partial failures, Leblanc eventually succeeded in isolating soda crystals by fusing sulfate, coal, and limestone. In its final incarnation, the method, which became known as the Leblanc process, produced sodium carbonate by first exposing sea salt to sulfuric acid, and then converting the product to soda by calcinating (heating at a high temperature) with limestone and charcoal.

Once the process was established, Leblanc turned his attention to producing soda. He and Dize went to London, where the Duke had been sent as a result of rising political tensions, to discuss the necessary steps. An agreement reached on March 27, 1790 among Leblanc, Dize, and Henri Shee, the Duke's steward, stipulated that Leblanc submit a complete description of the process, which would be certified by Darcet. Dize also submitted his invention of a method for manufacturing sal ammoniac, a complementary process to the production of soda. In return Leblanc and Dize were to receive 200,000 livres to pursue the development of a profitable business of soda production.

In 1791 Leblanc applied for a patent. According to Ralph E. Oesper in the Journal of Chemical Education, a board of examiners reported: "Having carefully examined the method employed by said M. Leblanc for producing soda by the large-scale decomposition of sea salt, we acknowledge that the invention is new and very superior to all that up to now have come to our knowledge as regards to economy, speed and certainty of the method as well as regards to the abundance and purity of the products. We believe that the discovery of M. Leblanc for political and economic reasons merits the encouragement of the French nation, and that the secret of his discovery should be well guarded." Leblanc was granted a secret patent on September 25, 1791, which gave him the sole right to the process for the next 15 years.

Soda Plant at St. Denis

A manufacturing plant was built in St. Denis, a small village located four miles outside of Paris, and production began. With a production rate of between 500 and 600 pounds of soda every day, the soda works had sales totaling 420,000 livres by the spring of 1794. However, the unstable political times brought devastating changes to Leblanc's operation. First, there was a critical shortage of potash (previously the primary source of soda), because it was needed to produce gunpowder, so the French government instructed all soda manufacturers to disclose plant production levels, processes, and sales. Leblanc was ordered to reveal the secrets of his invention. Second, Leblanc was further hampered by the arrest of the Duke, known during the Revolution as Philippe Egalite, and his subsequent beheading on November 6, 1793. The Revolutionary government confiscated all his property, including his interest in the soda plant. In effect, the French government became the chief shareholder of the business.

In the chaos of the revolution, the government suspended production at Leblanc's plant. Even though a review committee highly recommended the operation and commended Leblanc and Dize for their patriotism for revealing the secrets of the process, the French government established soda production at other locations, leaving Leblanc's plant closed. Rather than being allowed to provide his country with soda, Leblanc was ordered to leave the premises, including the house on the factory grounds in which he lived with his wife and children. He received no financial reward for his chemical contribution, nor for his interest in the soda plant. Just months before, Leblanc stood at the threshold of financial success; suddenly he was thrown into poverty.

The Revolution and Aftermath

Leblanc held several government positions after the soda operation was shut down. Beginning in 1792, he served as the administrator to the Department of the Seine for five consecutive terms, but he received no salary for his work. In January 1794 he secured a salaried position as the commissioner of powder and saltpeter, but the department was dissolved within six months, along with Leblanc's job. In February 1794 he was appointed to the temporary Commission of the Arts, a branch of the Committee of Public Instruction. He was responsible, again without remuneration, for taking an inventory of the contents of properties confiscated by the government, including those facilities left vacant because their owners had been guillotined.

In June 1795, as the Revolution was winding down and France was working to restore normalcy, Leblanc was appointed by the Committee on Public Safety to investigate the steps necessary to rebuild the mining industry. After sending back numerous papers and information from the mining regions, Leblanc was named director of a copper and alum mining operation. Although he was supposed to receive a salary and reimbursement for expenses, he never did. After one year, he returned to Paris in desperate financial straits.

Constantly attentive to chemical processes that could be used in industry, Leblanc began researching the possible use of the ammonia that is released when organic matter is subjected to heat. In time, Leblanc developed the use of animal waste to create ammonia, which in turn provided a useful fertilizer. After developing a small-scale mechanism that effectively produced ammonia from animal waste, Leblanc petitioned the government for a grant to establish a commercial plant. He also requested an exclusive patent and the sole rights to certain waste facilities. Although none of his requests were honored and his efforts to establish a plant failed, he can be credited with important developments in the study of fertilizers.

Leblanc's troubles continued. He could not find adequate employment. Considering himself to be academically inadequate, he declined a faculty position offered to him by the Ecole Centale in Alby in 1796. The following year he secured a place on the Council of Conservation, but before his nomination was acted upon, the minister of interior was replaced, and the new director made different appointments. In 1798 Leblanc won an election for the office of second deputy of St. Denis, but the election was contested and the seat was awarded to his opponent. His struggles were exacerbated by a family tragedy: his 16-year-old daughter became suddenly paralyzed and died six months later.

Failure and Depression

LeBlanc still hoped someday to reopen his soda plant or at least to be compensated for his discovery and investment. The Department of Public Safety finally awarded him 3,000 francs as payment for past services, but Leblanc received only 60 francs. By April 1801 Leblanc had enlisted enough support to persuade the French government under Napoleon to return the factory at St. Denis to him and his partners. Because Shee and Dize were otherwise occupied, Leblanc became the director of the whole operation. Despite his best efforts to revive the factory, Leblanc never reestablished a profitable business. The years of idleness had left the machinery in poor condition, and much of the necessary equipment had been confiscated and removed. Also, because Leblanc's process had become public knowledge, others had opened competing plants.

For several years Leblanc worked diligently to secure funds to revive his operation. Finally in November 1804, arbitrators determined LeBlanc was due payment of 52,473 francs—about $10,000—from the government. It was far less than he had hoped, and no money was ever paid. Leblanc fell into deep depression. He became withdrawn and morose, and his health deteriorated. On January 16, 1806, he committed suicide in his study by putting a bullet in his head.

Later, Dize, who took the soda plant from Leblanc's family in payment for a debt owed him by Leblanc, made claims that he was the mastermind of the soda process. However, historians agree that Dize, a trained chemist who believed himself a superior scientist to Leblanc, was overstating his role in the development of the process, and that Leblanc should get the most credit for the first efficient, economical method of producing soda.


Asimov, Isaac, Asimov's Biographical Encyclopedia of Science and Technology, Doubleday, 1964.

A Biographical Dictionary of Scientists, Third edition, edited by Trevor I. Williams, Adam and Charles Black, 1982.

The Cambridge Biographical Encyclopedia, 2nd edition, edited by David Crystal, Cambridge University Press, 1998.

Daintith, John; Mitchell, Sarah, and Tootill, Elizabeth, A Biographical Encyclopedia of Scientists, Volume 2, Facts on File, 1981.

Dictionary of Scientific Biography, Volume 8, edited by Charles Coulston Gillispie, Charles Scribner's Sons, 1973.


Journal of Chemical Education, December 1942; January 1943.


"Leblanc, Nicolas," World of Invention, (February 5, 2001).

"Nicolas Leblanc," Merriam-Webster's Biographical Dictionary, (February 5, 2001). □

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Leblanc, Nicolas


Nicolas Leblanc invented a method of making alkali soda from salt that became one of the most important chemical processes of the nineteenth century. Leblanc was born in Issoudun, France; his father managed an iron-works. After completing his medical education in about 1780, Leblanc became a private physician in the house of Philippe Égalité, duc d'Orléans (17471793). France had been suffering from an acute shortage of alkali from traditional vegetable sources. Alkali was critical in the manufacture of glass, textiles, paper, soap, and other products. In 1775 the French Royal Academy offered a prize to anyone who could develop a process for transforming common salt (sodium chloride) into soda ash. With Égalité's support, Leblanc achieved the goal by 1789 and opened a small factory at Saint Denis that began production in 1791.

What became known as the Leblanc process was actually several inter-related processes. Salt was first reacted with sulphuric acid in a cast-iron pan, then in a reverberator furnace (in which heat was applied from a flame blown from a separate chamber, not in direct contact with the salt), to produce saltcake (sodium sulphate), with hydrochloric acid released as a waste gas. Saltcake was used to make sodium carbonate, or roasted with limestone (calcium carbonate) and coal or coke to produce "black ash." This mixture of sodium carbonate, calcium sulphide, sodium sulphide, lime, salt, carbon, and ash could be treated further with hot water to produce impure sodium carbonate in solution, evaporated into soda crystals (washing soda), or heated to yield anhydrous sodium carbonate. The latter, in turn, could be reacted with lime to made caustic soda (sodium hydroxide), the strongest commercial alkali then available.

Leblanc personally benefited little from his innovation. The National Assembly granted him a fifteen-year patent in September 1791, but three years later the revolutionary government sequestered his factory and made his patents public, giving Leblanc only meager compensation for his assets. Napoléon Bonaparte returned the plant to him in 1802, but by then Leblanc was too poor to resume production and, in 1806 he took his own life. (In 1855 Napoléon III gave Leblanc's heirs a payment in lieu of the 1775 prize.)

Leblanc's processby greatly reducing the cost and boosting the efficiency of alkali for the key industries that depended on itboosted European industrialization for two generations. The year of Leblanc's suicide, the Saint Gobain Company opened a soda ash factory; by 1818 French producers were turning about roughly 10,000 to 15,000 tons of Leblanc soda ash per year. British producers, discouraged until a prohibitive tax on salt was repealed in 1823, embraced the new process and surpassed the French by the middle of the century. U.S. alkali makers remained wedded to potash but imported Leblanc soda ash after 1850. Germany took the lead in Leblanc soda production in the 1870s.

By that time the Leblanc process was facing competition from the newer Solvay (ammonia soda) alkali. The dominance of Leblanc soda was extended by improvements, most notably the Deacon process (1868), which converted the wasteful and harmful hydrochloric acid gases into chlorine, and the Chance process (1882), which recovered waste sulphur. By the turn of the twentieth century, however, the Leblanc and Solvay processes were eclipsed by new electrolytic methods for making chlorine and caustic soda.

see also Alkali Metals; Industrial Chemistry, Inorganic; Sodium.

David B. Sicilia


Haber, L. F. (1958). The Chemical Industry during the Nineteenth Century: A Study of the Economic Aspect of Applied Chemistry in Europe and North America. Oxford, U.K.: Clarendon Press.

Landes, David S. (1972) The Unbound Prometheus: Technological Change and Industrial Development in Western Europe from 1750 to the Present. Cambridge, MA: Harvard University Press.

Morgan, Sir Gilbert T., and Pratt, David D. (1938). British Chemical Industry: Its Rise and Development. London: Edward Arnold & Co.

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Leblanc, Nicolas

(b. Ivoy-le-Pré, France, 6 December 1742; d Paris, France, 16 January 1806)


From 1751 Leblanc was brought up as and orphan in Bourges. Influenced by his guardian, who was adoctor, he went to the École de Chirurgie in Paris and in 1780 entered the service of the duc d’Orlèans (the future Philippe Égalité) as a surgeon. The patronage of the Orléans family, which lasted until the duke was guillotined in November1793, gave Leblanc the opportunity for research. He began with a study of crystallization, the results of which were later incorporated in his book Cristallotechnie (1802), But the most important work dating from this period was that which led him in 1789 to the discovery of the Leblanc process for the artificial preparation of soda. Although it was developed industrially, the discovery brought Leblanc neither happiness nor prosperity, and he eventually committed suicide.

During the late eighteenth century there were strong incentives to devise a new method for the preparation of soda. It was observed that it might soon become impossible to meet the growing industrial demand for soda from the traditional sources, such as potash, which was obtained from wood ashes, or from coastal shrubs like barilla, imported from Spain. In the 1770’s and 1780’s a number of alternative methods were developed, and between 1783 and 1788 the Académie es Sciences showed its interest by offering a prize for the best method of preparing soda from salt. Although no prize was awarded, by the time Leblanc made his discovery in 1789 several establishments were manufacturing artificial soda in France, if only as a by-product.

In Leblanc’s method, sodium sulfate is prepared by the action of sulfuric acid on the salt from seawater and is them converted to soda by calcination with limestone and charcoal. It is not clear how Leblanc discovered the method, for there was now obvious precedent in the processes then in use; and the precise mechanism of the reaction was still obscure over a century later. In fact in 1810, in and artical disputing Leblanc’s claim to the discovery, J.J. DizLé even maintained that at first Leblanc had prepared sodium sulfide, mistaking it for soda, and that the correct process was developed only in subsequent researches undertaken by Leblanc and Dizé jointly ,with guidance from Jean Darcet, the agent of the d’Orlé even Unfortunately there is no way of confirming or disproving Dizé’s account, but it seems porbable that the credit for the discovery should go to Leblanc. In any event, such was the decision of a commission specially appointed by the Académie des Sciences in 1856.

Once made, the discovery was quickly applied. In 1790 the due d’Orléans, Leblanc, Dizé, and Henri Shée formed a company; and between 1791 and 1793, with capital provided by the duke, a factory was established at St.-Denis. But regular production never began. In 1793 work was abandoned because of the wartime shortage of sulfuric acid, and early in 1794 the factory was nationalized as property of the executed duc d’Orléans. Some months later details of Leblanc’s process (with details of all the other known processes for the manufacture of soda) were published by the Committee of Public Safety in the interests of the war effort. Although Leblanc very soon began to seek compensation for his losses, it was several years before his many letters and petitions had any effect, and even when control of the factory was provisionally returned to him in 1800, pending a definitive ruling on his claims, he did not succeed in reviving it through lack of capital. His hope was always that the final settle- ment of his claims would give him the capital he needed. However, when a settlement was eventually made, in November 1805, the award announced fell far short of his expectations, and two months later, in despair and ill health, Leblanc shot himself.


I. Original Works. Leblanc’s only major publication is De la cristallotechnie, ou sur les phénomènes de la cristallisation (Paris, 1802). For references to the surviving MS material see the article by C. C. Gillispie cited below.

II. Secondary Literature. The standard biography, Nicolas Leblanc, sa vie, travaux, et l’histoire de la soude artificielle (Paris, 1884), is by Leblanc’s grandson, Auguste Anastasi. Despite some useful documentation, it is uncritical and has set the tone for most subsequent biographical sketches, nearly all of which reflect Anastasi’s undue reverence for Leblanc. The most useful of the derivative sketches are P. Baud, “Les origines de la grande industrie chimique en France,”in Revue historique, 174 (1934), 1-18; and R. E. Oesper, “Nicolas Leblanc (1742-1806),”in Journal of Chemical Education, 19 (1942), 567-572, and 20 (1943), 11-20. And important reappraisal is C. C. Gillispie, “The Discovery of the Leblanc Process,”in Isis, 48 (1957), 152-170, which uses MS material to show Leblanc as the victim less of misfortune that of his own difficult personality. The article also reexamines the circumstances of the discovery. A more favorable view of Leblanc appears in J. G. Smith, “Studies of Certain Chemical Industries in Revolutionary and Napoleonic France”(Leeds University, Ph.D. thesis, 1970). For the deliberations of the 1856 commission, see L. J. Thenard et al., “Rapport relatif à la découverte de la soude artificielle,”in Comptes rendus hebdomadaires des séances de l’Académie des sciences,42 (1856), 553-578.

Robert Fox

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Nicolas Leblanc


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, lacking the 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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Nicolas Leblanc


French physician and inventor who is best known for inventing a process by which to make sodium carbonate. This material is widely used in making glass, soap, and other useful chemicals. In fact, Leblanc's process was widely used for over a century, although Leblanc did not benefit from this because his factory was seized during the French Revolution. Due to this and other problems, he committed suicide at age 64.

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Leblanc, Nicolas (1742–1806) French chemist. In 1790, he devised a process for producing soda ash (sodium carbonate, Na2CO3) from salt (sodium chloride, NaCl) by treating it with sulphuric acid.