The French chemist and physicist Joseph Louis Gay-Lussac (1778-1850) is distinguished for his work on gas laws and for his studies of the properties of cyanogen and iodine.

Born at Saint-Léonard in the department of Vienne, Joseph Gay-Lussac came from a solidly bourgeois family. The storms of the French Revolution delayed his education, but largely by his own disciplined self-teaching, he passed the examinations and was admitted to the prestigious École Polytechnique in 1797. Here he became the protégé of Claude Louis Berthollet.

In these early years Gay-Lussac's skill as an experimenter and scientific instrument maker was well developed. In 1802 he published a law of the expansion of gases by heat, which became known as Charles' law. In 1804 he made an ascent of 23,000 feet in a balloon to collect samples of the atmosphere for chemical analyses and to measure the dependence of the earth's magnetic field on elevation. In 1806 Gay-Lussac was elected to the Institut de France, and in 1809 he became a professor of chemistry at the École Polytechnique and professor of physics at the Sorbonne. He invented the portable barometer, steam injector pump, and air thermometer and improved the spirit lamp and the chemist's furnace. In addition to his work on these laboratory devices, he contributed to the production and improvement of industrial chemical machinery and processes, above all in the important sulfuric acid tower which bears his name.

In 1805-1806, through the intervention of Berthollet, Gay-Lussac accompanied the scientific explorer Alexander von Humboldt on his expedition through Italy and Germany making measurements of terrestrial magnetism. While in Rome, the young chemist was able to use the laboratory of Wilhelm von Humboldt, on which occasion he discovered the presence of fluorides and phosphates in the bones of fish. Not long after this, Gay-Lussac met a beautiful girl in a Paris draper's shop, soon became engaged, and then sent his fiancée to school to complete her chemistry education. In 1808 he married her. The marriage lasted for 40 years and was marked by the closest collaboration of hearts and minds.

In addition to his well-known work on the combining properties of gases, Gay-Lussac also worked on the determination of vapor densities, and the coefficients of expansion of gases, in which he pioneered the procedures, and contributed to the careful quantitative measurements that in later years were so useful for grounding the kinetic theory of gases and thermal physics. He published his most influential work in 1808, the law of combining volumes of gases.

Electrolysis and Iodine

Some of Gay-Lussac's best work, however, was done in close collaboration with Louis Jacques Thénard, the chemist who created the foundations of organic analysis. Together they produced the alkali metals in quantity by reacting fused alkalis with red-hot iron. Napoleon made considerable sums available to the École Polytechnique to support their work on electrolysis. However, though aware of the theoretical importance of the electrolytic process, they elaborated a more efficient method of producing the alkali metals.

Gay-Lussac investigated (1813-1814) the chemical properties of iodine and described his findings in a number of papers presented to the Institut de France. However, Sir Humphry Davy, visiting in Paris at the time, wrote a particularly insulting note to the scientific world claiming priority for the discovery of the elemental nature of iodine, asserting that Gay-Lussac had learned the fundamental properties of iodine from him. In yet another controversy Gay-Lussac and Thénard claimed a priority of 36 hours for their isolation of boron. They claimed that the experiment was completed on June 21, 1800, and the results sent to Geneva for publication, whereas Davy's announcement was supposedly dated June 30. It should be noted that the potassium that Davy used to treat borax was produced by using the Thénard-Gay-Lussac method.

Other Achievements

The French partners also carried out extensive investigations on the composition of hydrochloric acid. Individual work by Gay-Lussac on the properties of the sulfates and sulfides, as well as other salts, was an important step in the perfection of what later became known as volumetric analysis. He compiled extensive solubility charts for numerous compounds. Classic work on cyanogen compounds was carried out by him largely on his own. He was also the first to recognize that the CN combination was stable and behaved as a radical in the various combinations into which it entered.

Gay-Lussac served in 1818 as superintendent of the government gunpowder plant and as chief assayer of the national mint in 1829. King Louis Philippe raised him to the peerage in 1839. The honor had been delayed for 17 years, for, argued the old aristocracy, Gay-Lussac worked with his hands. He died on May 9, 1850.

Further Reading

• Gay-Lussac is discussed in Sir William A. Tilden, Famous Chemists: The Men and Their Work (1921); Edward Farber, ed., Great Chemists (1961); and Maurice Crosland, The Society of Arcueil: A View of French Science at the Time of Napoleon I (1967).