(December 6, 1778 – May 9, 1850)
Joseph Louis Gay-Lussac was insatiably curious: a trait which predisposed him into becoming one of the greatest experimenters of the 19th century. Even before earning his professorial chair in physics, he researched extensively in chemistry. After occupying that physics chair for 24 years at Sorbonne, he relinquished it for a chemistry one at the Jardin des Plantes (which was also in Paris). Gases intrigued him; just like his showy compatriot, Antoine Lavoisier. With the aid of hydrogen-filled balloons, he would ascend a few kilometers above sea-level in order to collect fresh air samples for analysis. It was many of such analyses which led him to discover that when gases react at constant temperature and pressure, they combine in volumes which are in simple ratios; and to the volume of the product (if gaseous). This gas law became known as Gay-Lussac’s Law of Combining Volumes. And it provided clues which inspired Amedeo Avogadro to come-up with his own groundbreaking hypothesis, after further investigations. Apart from working with gases, Gay-Lussac made other notable contributions to chemistry. For example, he co-discovered boron with Louis Jacques Thénard and Humphry Davy. And while collaborating with Alexander von Humboldt, he discovered that water comprise of two parts of hydrogen and one part of oxygen by volume. He also coined the terms: “burette” and “pipette” after developing improved versions of both. And his quantitative analyses of alcohols made France, the U.K., and several other countries to adopt “degrees Gay-Lussac” as the standard percentage-by-volume measurement for ethanol.