page_title: Joseph Louis Gay-Lussac
section_title: Achievements
hierarchical_section_title: Joseph Louis Gay-Lussac / Achievements
context_page_description: Joseph Louis Gay-Lussac 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, 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.
context_section_description: 1802 – Gay-Lussac first formulated the law, Gay-Lussac's Law, stating that if the mass and volume of a gas are held constant then gas pressure increases linearly as the temperature rises. His work was preceded by that of Guillaume Amontons, who established the rough relation without the use of accurate thermometers. The law is sometimes written as p = k T, where k is a constant dependent on the mass and volume of the gas and T is temperature on an absolute scale (in terms of the ideal gas law, k = n·R/V).
  1804 – He and Jean-Baptiste Biot made a hot-air balloon ascent to a height of 7,016 metres (23,018 ft) in an early investigation of the Earth's atmosphere. He wanted to collect samples of the air 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.
  1810 – In collaboration with Louis Thenard, he developed a method for quantitative elemental analysis by measuring the CO₂ and O₂ evolved by reaction with 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.
caption: Gay-Lussac and Biot ascend in a hot air balloon, 1804. Illustration from the late 19th century.
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