Joseph Louis Gay-Lussac

December 6th 1778 - May 9th 1850

Joseph Louis Gay-Lussac, by virtue of his skill and diligence as an experimentalist, and by his demonstration of the power of the scientific method, deserves recognition as a great scientist. Born on December 6, 1778, Joseph was the eldest of five children. His father, Antoine Gay, was a lawyer who, to distinguish himself from other people in the Limoges region with the last name of Gay, used the surname Gay-Lussac from the name of some family property near St Leonard. The French Revolution affected many of what were to become the French scientific elite. Gay-Lussac was sent to Paris at the age of fourteen when his father was arrested. After having had private lessons and attending a boarding school, the Ecole Polytechnique and the civil engineering school, Gay-Lussac became an assistant to Berthollet who was himself a co-worker of Lavoisier. Gay-Lussac thus got the chance to become part of the group of famous men who spent time at Berthollet's country house near Arcueil. Here among the Arcueil Society he received his training in chemical research.

With the encouragement of Berthollet and LaPlace, Gay-Lussac at the age of 24 conducted his first major research in the winter of 1801-1802. He settled some conflicting evidence about the expansion properties of different gases. By excluding water vapour from the apparatus and by making sure that the gases themselves were free of moisture, he obtained results that were more accurate than had been obtained previously by others. He concluded that equal volumes of all gases expand equally with the same increase in temperature. While Jacques Charles discovered this volume-temperature relationship fifteen years earlier, he had not published it. Unlike Gay-Lussac, Charles did not measure the coefficient of expansion. Also, because of the presence of water in the apparatus and the gases themselves, Charles obtained results that indicated unequal expansion for the gases that were water soluble.

Gay-Lussac, like his mentor Berthollet, was interested in how chemical reactions take place. Working with the mathematical physicist, LaPlace, Gay-Lussac made quantitative measurements on capillary action. The goal was to support LaPlace 's belief in his Newtonian theory of chemical affinity. In 1814 this theoretical bent continued as Gay-Lussac and LaPlace sought to determine if chemistry could be reduced to applied mathematics. The approach was to ask whether the conditions of chemical reactions could be reduced simply to, as LaPlace had suggested, considerations of heat.

As with his mentor before him, Gay-Lussac was consulted by industry and supported by the government. "Napoleonic science sharpened the appetites of young men by holding up the prospects of recognition and reward". Gay-Lussac and Thenard, the laboratory boy turned professor, isolated the element boron nine days before Davy'sroup did (but Davyas the first to publish.) Gay-Lussac led his group into the isolation of plant alkaloids for potential medical use and he was instrumental in developing the industrial production of oxalic acid from the fusion of sawdust with alkali. His most important contribution to industry was, in 1827, the refinement of the lead chamber process for the production of sulfuric acid, the industrial chemical produced in largest volume in the world.

While Gay-Lussac was a great theoretical scientist, he was also respected by his colleagues for his careful, elegant, experimental work. Wanting to know why and how something happened was important to Gay-Lussac, but he preferred knowing much about a limited subject rather than proposing broad new theories which might be wrong . He devised many new types of apparatus such as the portable barometer, an improved pipette and burette and, when working at the Mint, a new apparatus for quickly and accurately estimating the purity of silver which was the only legal measure in France until 1881. His work on iodine is considered a model of chemical research. His precise measurement of the thermal expansion of gases mentioned above was used by Lord Kelvin in the development of the absolute temperature scale and Third Law of Thermodynamics and by Clausius in the development of the Second Law. He and Thenard improved existing methods of elemental analysis and developed volumetric procedures for measuring acids and alkalis. His quantification of the effect of light on the reaction of chlorine with hydrogen elevated photochemistry from mere artifice into a theoretical science which culminated, fifty years after his death, in the quantum theory. An example of his dedication to meticulous experimenting is his decision to undertake a balloon flight to a record setting height of 23,000 feet to test an hypotheses on earth's magnetic field and the composition of the air.