Joseph Louis Gay-Lussac
Joseph Louis Gay-Lussac (, , ; 6 December 1778 – 9 May 1850) was a French chemist and physicist. He is known mostly for his discovery that water is made of two parts hydrogen and one part oxygen by volume (with Alexander von Humboldt), for two laws related to gases, and for his work on alcohol–water mixtures, which led to the degrees Gay-Lussac used to measure alcoholic beverages in many countries. Biography 
Gay-Lussac was born at Saint-Léonard-de-Noblat in the present-day department of Haute-Vienne. His father, Anthony Gay, son of a doctor, was a lawyer and prosecutor and worked as a judge in Noblat Bridge. Father of two sons and three daughters, he owned much of the Lussac village and began to add the name of this hamlet to his name, following a custom of the Ancien Régime. Towards the year 1803, father and son formally adopted the name Gay-Lussac. During the Revolution, under the Law of Suspects, his father, former king's attorney, was imprisoned in Saint Léonard from 1793 to 1794. Gay-Lussac received his early education at the hands of the Catholic Abbey of Bourdeix. In the care of the Abbot of Dumonteil, he began his education in Paris, finally entering the École Polytechnique in 1798. Three years later, Gay-Lussac transferred to the École des Ponts et Chaussées, and shortly afterward was assigned to C. L. Berthollet as his assistant. In 1804 he was appointed répétiteur (demonstrator) to Antoine François Fourcroy at the École Polytechnique, whom he succeeded in 1809 as professor of chemistry. From 1809 to 1832, he was also the professor of physics at the Sorbonne, a post which he only resigned for the chair of chemistry at the Jardin des Plantes. In 1821, he was elected a foreign member of the Royal Swedish Academy of Sciences. In 1831 he was elected to represent Haute-Vienne in the chamber of deputies, and in 1839 he entered the chamber of peers. He was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1832. Gay-Lussac married Geneviève-Marie-Joseph Rojot in 1809. He had first met her when she worked as a linen draper's shop assistant; he noticed she was studying a chemistry textbook under the counter, which led to their acquaintance. The couple had five children, of whom the eldest (Jules) became a student of Justus Liebig in Giessen. Some publications by Jules are mistaken as his father's today since they share the same first initial (J. Gay-Lussac). Gay-Lussac had a reputation as one of the greatest European scientists of his day, well justified by his innumerable discoveries in both chemistry and physics. The restored royalty made him a Peer of France, although he worked politically with the anti-clerical party. He was closely associated with François Arago. Gay-Lussac died in Paris, and his grave is there at Père Lachaise Cemetery. His name is one of the 72 names inscribed on the Eiffel Tower. Achievements 

 1802 – Gay-Lussac first published the law that at constant pressure, the volume of any gas increases in proportion to its absolute temperature. Since in his paper announcing the law he cited earlier unpublished work on this subject by Jacques Charles, the law is usually called Charles's Law, though some sources use the expression Gay-Lussac's Law. This law was independently and nearly simultaneously stated by John Dalton. 1804 – He and Jean-Baptiste Biot made a hydrogen-balloon ascent; a second ascent the same year by Gay-Lussac alone attained a height of  in an early investigation of the Earth's atmosphere. He wanted to collect air samples at different heights to record differences in temperature and moisture. 1805 – Together with his friend and scientific collaborator Alexander von Humboldt, he discovered that the composition of the atmosphere does not change with decreasing pressure (increasing altitude). They also discovered that water is formed by two parts of hydrogen and one part of oxygen (by volume). 1808 – He was the co-discoverer of boron. 1808 – Discovery and announcement of the law of combining volumes of gases; published in 1809. 1810 – In collaboration with Louis Jacques Thénard, he developed a method for quantitative elemental organic combustion analysis by measuring the CO2 and H2O evolved when an organic compound is fully oxidized by potassium chlorate. He also summarised the equation of alcoholic fermentation. 1811 – He recognized iodine as a new element, described its properties, and suggested the name iode. 1815 – He synthesized cyanogen, determined its empirical formula, and named it. 1824 – He developed an improved version of the burette that included a side arm, and coined the terms "pipette" and "burette" in an 1824 paper about the standardization of indigo solutions. Awards and honors 
 Along with Thénard, Gay Lussac received 30,000 francs from Napoleon in the third edition of the Galvanism Prize in 1809 for their research. In Paris, a street and a hotel near the Sorbonne are named after him as are a square and a street in his birthplace, Saint-Léonard-de-Noblat
 In Australia, the "Gay-Lussac Room" at AB Mauri STC, Sydney was named after him in honor of his work with yeast fermentation. Academic lineage

Publications 
 Chemistry courses of the École Polytechnique, Vol.1&2
Lessons of Physics, Faculty of Sciences in Paris, (November 6, 1827, March 18, 1828)

See also 
Brin process
Joule expansion

References

Further reading 

 Joseph Louis Gay-Lussac, French chemist (1778–1850) from the Encyclopædia Britannica, 10th Edition (1902)
 Rue Gay-Lussac, Paris
 Gay-Lussac's article (1809) "On the combination of gaseous substances", online and analyzed on BibNum (for English, click 'à télécharger'). École Polytechnique alumni
École des Ponts ParisTech alumni
Corps des ponts
1778 births
1850 deaths
People from Haute-Vienne
Academic staff of the University of Paris
Burials at Père Lachaise Cemetery
Discoverers of chemical elements
Members of the French Academy of Sciences
Members of the Royal Swedish Academy of Sciences
Fellows of the American Academy of Arts and Sciences
Recipients of the Pour le Mérite (civil class)
French atheists
19th-century French chemists
19th-century French physicists
Foreign Members of the Royal Society
Boron
Flight altitude record holders
French aviation record holders
Fluid dynamicists