Joseph-Louis Gay-Lussac

French physical scientist

• Born: December 6, 1778
• Birthplace: Saint-Léonard-de-Noblat, France
• Died: May 9, 1850
• Place of death: Paris, France

A preeminent scientist of his generation, Gay-Lussac helped prepare the way, through his discoveries in chemistry and physics, for the modern atomic-molecular theory of matter. His investigations of gases led to the law describing how they react with each other in simple proportions by volume, and his chemical investigations led to the discovery of a new element, boron, and to the development of new techniques in qualitative and quantitative analysis.

Early Life

Born in a small market town in west central France, Joseph-Louis Gay was the eldest son of five children of Antoine Gay, a lawyer and public prosecutor, who, to distinguish himself from others called Gay, later changed his surname to Gay-Lussac (gay-lew-sahk), after the family property in the nearby hamlet of Lussac. Joseph-Louis used this expanded name throughout his life. His early education from a priest and his comfortable social and economic position were ended by the French Revolution of 1789, and in the turbulent years that followed, his teacher fled the country, and his father was arrested.

With the fall of Robespierre in 1794, the Revolution took a more moderate direction, and Gay-Lussac’s father was freed. Antoine Gay-Lussac was then able to send Joseph-Louis to Paris to continue his education at religious boarding schools. His father expected him to study law, but Gay-Lussac became increasingly interested in mathematics and science. His excellent record in mathematics gave him the opportunity to enter the École Polytechnique, then a young but already prestigious revolutionary institution for the training of civil and military engineers. Gay-Lussac completed his studies there with distinction, and he was graduated in November, 1800. He then entered the École des Ponts et Chaussées. He saw engineering not as a career but as a position to fall back on if he did not succeed in pure science.

During these years of study, Gay-Lussac came under the wing of Claude Louis Berthollet, a distinguished chemist and former companion to Napoleon I in Egypt. In his triple role as teacher, father-substitute, and patron, Berthollet became the most important influence on Gay-Lussac’s life. Some of Gay-Lussac’s greatest early work was done at Berthollet’s country house at Arcueil, where important scientists would gather and where the Society of Arcueil was later formed. Gay-Lussac continued his studies at the École des Ponts et Chaussées, but his relationship with the school grew more nominal as he spent more and more time on scientific research at Arcueil.

Life’s Work

Gay-Lussac’s initial research was of considerable importance both because of its permanent scientific value and because it marked his successful initiation into a career of pure science. In 1802, after painstaking measurements, he showed that many different gases expand equally over the temperature range from 0 to +100 degrees Celsius. Despite the thoroughness of his studies and the significance of his results, Gay-Lussac is not generally credited with the discovery of the quantitative law of the thermal expansion of gases. Some chemists recalled that Jacques Charles, a French physicist, had found in 1787 that certain gases expanded equally, but Charles had also found that other gases, those that dissolved in water, had different rates of expansion. Because Charles never published his work and because he did not completely understand the phenomenon of thermal expansion, many scholars believe that justice demands that this discovery should be known as Gay-Lussac’s law.

Gases were central to another of Gay-Lussac’s early research projects. During the early nineteenth century, scientists debated whether the percentage of nitrogen, oxygen, and other gases was different in the upper and lower atmosphere. A similar diversity of opinion existed about the behavior of a magnet at low and high altitudes.

To resolve these differences, Gay-Lussac and Jean-Baptiste Biot, a young colleague, made a daring ascent from Paris in a hydrogen-filled balloon on August 24, 1804. By observing oscillations of a magnetic needle, they concluded that the intensity of the earth’s magnetism was constant up to four thousand meters, but they did not have time to collect samples of air. Therefore, to answer the question about the atmosphere’s composition, Gay-Lussac made a solo balloon ascent over Paris on September 16, 1804. He reached a height of more than seven thousand meters, an altitude record that would remain unmatched for a half century. He discovered that the temperature of the atmosphere decreased by one degree Celsius for every 174-meter increase in elevation. When he analyzed the air samples that he had collected, he found that the composition of air was the same at seven thousand meters as it was at sea level (his technique was not sensitive enough to detect the differences that were later found).

Shortly after the balloon flights, Gay-Lussac began to collaborate with Alexander von Humboldt, a Prussian nobleman, world traveler, and scientist. Gay-Lussac had just received an appointment to a junior post at the École Polytechnique when he met Humboldt, who was interested in his analysis of the atmosphere. Humboldt and Gay-Lussac agreed to collaborate in a series of experiments on atmospheric gases. Their research led to a precise determination of the relative proportions with which hydrogen and oxygen combine to form water: almost exactly two hundred parts to one hundred parts by volume. Though they were not the first to discover this 2:1 ratio (Henry Cavendish had noted it in 1784), the experiment convinced Gay-Lussac that scientists should study the reactions of gases by volume instead of by weight.

Because of the fruitfulness of their collaboration, Gay-Lussac wanted to accompany Humboldt on a European tour he was planning, to make a systematic survey of magnetic intensities. Gay-Lussac was granted a leave of absence from the École Polytechnique, and in March, 1805, he and Humboldt embarked on a year of travel through Italy, Switzerland, and Germany. Through their tour, Gay-Lussac made many contacts with important physicists and chemists such as Alessandro Volta, the inventor of the electric battery. A tangible result of his European travels was a paper on terrestrial magnetism. Because of this and other studies, he was elected in 1806 to the National Institute (the revolutionary replacement for the Royal Academy of Sciences). Although this was a major step in Gay-Lussac’s career, his base of operations remained the École Polytechnique and Arcueil.

In 1807, Gay-Lussac completed a series of experiments to see if there was a general relationship between the specific heat of a gas and its density. Specific heat is a measure of a substance’s capacity to attract its own particular quantity of heat. For example, mercury has less capacity for heat than water; that is, mercury requires a smaller quantity of heat than does water to raise its temperature by the same number of degrees. Gay-Lussac knew that the compression of gases was accompanied by the evolution of heat and their expansion by the absorption of heat, but he wanted to find the relationship between the absorbed and evolved heat. Through an ingenious series of experiments, he discovered that the heat lost by expansion was equal to the heat gained by compression, a result significant in the history of physics, particularly for the law of the conservation of energy.

Although Gay-Lussac had studied the 2:1 chemical combination of hydrogen and oxygen in 1805, he did not generalize his results until 1808, when he again became interested in gas reactions. At that time, he began his long collaboration with Louis Jacques Thenard, a peasant’s son who had risen from laboratory boy to Polytechnique professor. In one of their early experiments, they heated a mixture of calcium fluoride and boric acid in an iron tube. Instead of getting the expected fluorine, they obtained fluoric acid (now called boron trifluoride), a gas that, on coming into contact with air, produced dense white fumes that reminded them of those produced by muriatic acid (now called hydrogen chloride) and ammonia. In fact, they found that boron trifluoride and ammonia reacted in a 1:1 ratio by volume, just as hydrogen chloride and ammonia did.

With these and other examples from his own experiments, along with results reported by others in various papers, Gay-Lussac felt secure enough to state that all gases combine in simple volumetric proportions. He announced this law, now known as Gay-Lussac’s law of combining volumes, at a meeting of the Société Philomatique in Paris on December 31, 1808. This law would later be used to teach students about the evidence for the atomic theory , but at the time of its proposal Gay-Lussac rejected John Dalton’s atomic theory.

Despite Gay-Lussac’s important research at the École Polytechnique and Arcueil, his career was stalled. During the years 1808 and 1809, his friends tried to lobby on his behalf for a position commensurate with his accomplishments. The death of Antoine Fourcroy in 1809 provided the opportunity for which Gay-Lussac’s friends had been waiting, and on February 17, 1810, Gay-Lussac became Fourcroy’s successor to the chemistry chair at the École Polytechnique. Another reason for this activity on Gay-Lussac’s behalf was his impending marriage to Geneviève-Marie-Joseph Riot, to whom he was married in May, 1809. The marriage was a happy one, eventually producing five children.

During the time that Gay-Lussac’s friends were trying to find him a position, Gay-Lussac and Thenard were doing important work on the alkali metals. These soft metals with great chemical reactivity had recently been isolated by Humphry Davy, the great English chemist who would become Gay-Lussac’s competitor in many discoveries. Davy had used the giant voltaic batteries at the Royal Institution to discover sodium and potassium. Because of the rivalry between Great Britain and France, Napoleon ordered the construction of an even larger collection of batteries at the École Polytechnique, and he urged Gay-Lussac and Thenard to do experiments with this voltaic pile. Ironically, they actually found that they could ignore electrolysis and use chemical means to produce large quantities of sodium and potassium. Davy’s electrical method had liberated only tiny amounts of the new metals, whereas Gay-Lussac and Thenard’s method of fusing potassium and sodium salts with iron filings at high temperatures produced great amounts of sodium and potassium more cheaply.

Gay-Lussac and Davy were both interested in isolating the element contained in boric acid. On June 21, 1808, Gay-Lussac and Thenard heated boric acid with potassium in a copper tube, producing a mixture of products, one of which was the new element. Their first published claim to the discovery of boron was in November, a month before Davy submitted a similar claim to the Royal Society. They delayed publishing their discovery because they wanted not only to decompose boric acid but also to recompose it.

After their work on boron, Gay-Lussac and Thenard examined oxymuriatic acid. At the beginning of the nineteenth century, chlorine was called oxymuriatic acid because chemists thought that it was a compound of oxygen and muriatic acid. This belief was based on its preparation by heating muriatic (now called hydrochloric) acid with a substance such as manganese dioxide with its abundance of oxygen. Gay-Lussac and Thenard were therefore astonished when they passed oxymuriatic acid gas over red-hot charcoal and the oxygen that was supposedly in the acid refused to combine with the charcoal. This led them to doubt that the gas contained oxygen and to suggest that it might be an element. Historians of chemistry usually report that Davy first recognized the elementary nature of chlorine, because in Gay-Lussac and Thenard’s report in the 1809 volume of the Arcueil Memoires, which was known to Davy, they conservatively stated that their experiments caused them to doubt the existence of oxygen in oxymuriatic acid, whereas Davy in 1810 unambiguously stated that it was an element, for which he proposed the name chlorine.

In addition to the misconception about chlorine, chemists of the time were also grappling with a faulty theory of acids since Antoine Lavoisier had earlier proposed that all acids contained oxygen. Until Gay-Lussac’s research on iodine in 1814 and on prussic acid in 1815, he had accepted Lavoisier’s theory of acidity. Gay-Lussac’s discovery and investigation of hydriodic acid reopened the question for him, and he concluded that hydrogen, not oxygen, was necessary to convert iodine to an acid. He clearly stated that hydrogen played the same role for one class of substances that oxygen did for another. He introduced the concept and name “hydracid” for the first class, and his studies of hydrogen chloride, hydrogen iodide, and hydrogen fluoride prepared the way for a new theory of acids.

Gay-Lussac’s early work was based on the recognition, common among chemists since the eighteenth century, that each substance possessed a unique chemical composition that could be represented by a unique formula. During the 1820’s, Gay-Lussac and other chemists discovered pairs of compounds, each member of which had the same number of the same atoms but with quite distinct properties. Gay-Lussac straightforwardly interpreted this phenomenon, called isomerism, as a result of the different atomic arrangements in the two substances. This idea, that different structures result in different chemical properties, would become an extremely important theme in the history of modern chemistry.

During the final decades of Gay-Lussac’s career, he turned his attention more and more to applied science. The economic needs created by his growing family caused him to do more industrial research, where the financial rewards were greater than in theoretical work. Particularly noteworthy was his development of a superior method of assaying silver using a standard solution of common salt. This precise method, which he developed after he became chief assayer to the mint in 1829, is still used.

In 1832, Gay-Lussac accepted a distinguished position at the Museum of Natural History. In his last years, he worked so hard to provide for his family that he produced little theoretical work, but he continued to reap honors for his brilliant early discoveries. In 1839, he became a Peer of France, even though his election was accepted reluctantly by those who thought that he worked too much with his hands to be a gentleman. He had a brief political career during the 1830’s, after which he held a number of advisory positions, where he used his technical knowledge to suggest improvements in such industrial chemical processes as the production of gunpowder and oxalic acid. He died in Paris on May 9, 1850, lamenting his departure from the world just when science was becoming interesting.

Significance

The quest for laws dominated Joseph-Louis Gay-Lussac’s scientific life. He believed that if a scientist lacked this desire, then the laws of nature would escape his attention. His most important discovery was the law of combining volumes, which helped pave the way for the modern atomic-molecular theory of matter.

Gay-Lussac managed to pass relatively unscathed through three political revolutions. Nevertheless, his life reflected the social and political changes taking place around him. His education occurred largely in schools founded or modified by the Revolution. Berthollet and the Society of Arcueil, the shapers of Gay-Lussac as a scientist, owed much to the patronage of Napoleon. During the 1830’s and 1840’s, under Louis-Philippe, Gay-Lussac became a conservative member of the professional class or upper bourgeoisie. Through all these changes he continued to be a French patriot. This chauvinism surfaced in his scientific controversies with the British chemists Humphry Davy and John Dalton.

Just as Gay-Lussac’s political life was a curious blend of liberalism and conservatism, so too was his scientific life. In his early career, devoted to pure science, he made so many important discoveries in so many areas that no one in post-Napoleonic France could teach chemistry without frequent references to his work. During the Restoration, however, he made few contributions to pure science, and he seemed to many young scientists to represent an enervating conservatism. For example, he adhered to the caloric theory of heat (heat as a substance) rather than embracing what most scientists saw as the superior kinetic theory (heat as motion).

Despite these weaknesses in his later career, Gay-Lussac’s place in the history of science is secure. His achievements in chemistry, physics, meteorology, and geology led him to become a central figure in the French scientific establishment, and he was influential in shaping such institutions as the École Polytechnique and the Museum of Natural History. His facility in applying chemistry to practical problems set an example that had wide repercussions later in the century. He also had great influence internationally—he emerges as a key figure of European science in the first third of the nineteenth century.

Bibliography

Crosland, Maurice. Gay-Lussac, Scientist and Bourgeois. New York: Cambridge University Press, 1978. Crosland takes a thematic rather than a strictly chronological approach to the life and work of Gay-Lussac. He relates Gay-Lussac both to the history of science and to contemporary social and political history. His account, which is refreshingly frank in dealing with issues of scientific rivalry and academic politics, is intended for historians of science as well as for social and economic historians, but because Crosland explains the science of the times so well, his work should be accessible to a wider audience.

‗‗‗‗‗‗‗. The Society of Arcueil: A View of French Science at the Time of Napoleon I. Cambridge, Mass.: Harvard University Press, 1967. This book contains an important account of the social context of Gay-Lussac’s early work. Crosland also uses Arcueil to make some good general points about the nature of patronage and about French science.

Ihde, Aaron J. The Development of Modern Chemistry. New York: Harper & Row, 1964. Ihde, who taught the history of chemistry for many years at the University of Wisconsin, emphasizes the period from the eighteenth to the twentieth centuries. His approach is more encyclopedic than analytic, but descriptive enough so that it is readable by high school and college chemistry students. Contains an extensive annotated bibliography.

Nye, Mary Jo. Before Big Science: The Pursuit of Modern Chemistry and Physics, 1800-1940. New York: Twayne, and London: Prentice Hall, 1996. A social and intellectual history of the physical sciences from the early nineteenth century until the beginning of World War II. Chapter 2, “Dalton’s Atom and Two Paths for the Study of Matter,” includes information on Gay-Lussac.

Purrington, Robert D. Physics in the Nineteenth Century. New Brunswick, N.J.: Rutgers University Press, 1997. An historical overview of nineteenth century physics, placing the science within the context of the Industrial Revolution and the rise of European nation states. Includes information about Gay-Lussac’s caloric theory of heat and his ideas about atoms.

Scott, Wilson L. The Conflict Between Atomism and Conservation Theory, 1644-1860. New York: Elsevier, 1970. Scott focuses on the conflict between groups of scientists over the issue of whether force (later called energy) is conserved when one hard body strikes another. This debate had important implications for the atomic theory, and Gay-Lussac’s ideas and experiments were integral to it. The book is based on extensive research, but because the author can tell a story and explain scientific concepts clearly, his account is accessible to readers without any special scientific knowledge.

Szabadvary, Ferenc. History of Analytical Chemistry. Elmsford, N.Y.: Pergamon Press, 1966. This book, first published in Hungarian in 1960, is a detailed account of the historical development of analytical chemistry. Gay-Lussac’s contributions to qualitative and quantitative, gravimetric and volumetric analyses are extensively discussed. The book is based largely on original sources and is intended for the reader with some knowledge of chemistry.