---
title: "History of chemistry"
chunk: 8/20
source: "https://en.wikipedia.org/wiki/History_of_chemistry"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:59:28.102404+00:00"
instance: "kb-cron"
---

=== New elements and gas laws ===

English chemist Humphry Davy was a pioneer in the field of electrolysis, using Alessandro Volta's voltaic pile to split up common compounds and thus isolate a series of new elements. He went on to electrolyse molten salts and discovered several new metals, especially sodium and potassium, highly reactive elements known as the alkali metals. Potassium, the first metal that was isolated by electrolysis, was discovered in 1807 by Davy, who derived it from caustic potash (KOH). Before the 19th century, no distinction was made between potassium and sodium. Sodium was first isolated by Davy in the same year by passing an electric current through molten sodium hydroxide (NaOH). When Davy heard that Berzelius and Pontin prepared calcium amalgam by electrolyzing lime in mercury, he tried it himself. Davy was successful, and discovered calcium in 1808 by electrolyzing a mixture of lime and mercuric oxide. He worked with electrolysis throughout his life and, in 1808, he isolated magnesium, strontium and barium.
Davy also experimented with gases by inhaling them. This experimental procedure nearly proved fatal on several occasions, but led to the discovery of the unusual effects of nitrous oxide, which came to be known as laughing gas. Chlorine was discovered in 1774 by Swedish chemist Carl Wilhelm Scheele, who called it "dephlogisticated marine acid" (see phlogiston theory) and mistakenly thought it contained oxygen. Scheele observed several properties of chlorine gas, such as its bleaching effect on litmus, its deadly effect on insects, its yellow-green colour, and the similarity of its smell to that of aqua regia. However, Scheele was unable to publish his findings at the time. In 1810, chlorine was given its current name by Humphry Davy (derived from the Greek word for green), who insisted that chlorine was in fact an element. He also showed that oxygen could not be obtained from the substance known as oxymuriatic acid (HCl solution). This discovery overturned Lavoisier's definition of acids as compounds of oxygen. Davy was a popular lecturer and able experimenter.

French chemist Joseph Louis Gay-Lussac shared the interest of Lavoisier and others in the quantitative study of the properties of gases. From his first major program of research in 1801–1802, he concluded that equal volumes of all gases expand equally with the same increase in temperature: this conclusion is usually called "Charles's law", as Gay-Lussac gave credit to Jacques Charles, who had arrived at nearly the same conclusion in the 1780s but had not published it. The law was independently discovered by British natural philosopher John Dalton by 1801, although Dalton's description was less thorough than Gay-Lussac's. In 1804 Gay-Lussac made several daring ascents of over 7,000 meters above sea level in hydrogen-filled balloons—a feat not equaled for another 50 years—that allowed him to investigate other aspects of gases. Not only did he gather magnetic measurements at various altitudes, but he also took pressure, temperature, and humidity measurements and samples of air, which he later analyzed chemically.
In 1808 Gay-Lussac announced what was probably his single greatest achievement: from his own and others' experiments he deduced that gases at constant temperature and pressure combine in simple numerical proportions by volume, and the resulting product or products—if gases—also bear a simple proportion by volume to the volumes of the reactants. In other words, gases under equal conditions of temperature and pressure react with one another in volume ratios of small whole numbers. This conclusion subsequently became known as "Gay-Lussac's law" or the "Law of Combining Volumes". With his fellow professor at the École Polytechnique, Louis Jacques Thénard, Gay-Lussac also participated in early electrochemical research, investigating the elements discovered by its means. Among other achievements, they decomposed boric acid by using fused potassium, thus discovering the element boron. The two also took part in contemporary debates that modified Lavoisier's definition of acids and furthered his program of analyzing organic compounds for their oxygen and hydrogen content.
The element iodine was discovered by French chemist Bernard Courtois in 1811. Courtois gave samples to his friends, Charles Bernard Desormes (1777–1862) and Nicolas Clément (1779–1841), to continue research. He also gave some of the substance to Gay-Lussac and to physicist André-Marie Ampère. On December 6, 1813, Gay-Lussac announced that the new substance was either an element or a compound of oxygen. It was Gay-Lussac who suggested the name "iode", from the Greek word ιώδες (iodes) for violet (because of the color of iodine vapor). Ampère had given some of his sample to Humphry Davy. Davy did some experiments on the substance and noted its similarity to chlorine. Davy sent a letter dated December 10 to the Royal Society of London stating that he had identified a new element. Arguments erupted between Davy and Gay-Lussac over who identified iodine first, but both scientists acknowledged Courtois as the first to isolate the element.
In 1815, Humphry Davy invented the Davy lamp, which allowed miners within coal mines to work safely in the presence of flammable gases. There had been many mining explosions caused by firedamp or methane often ignited by open flames of the lamps then used by miners. Davy conceived of using an iron gauze to enclose a lamp's flame, and so prevent the methane burning inside the lamp from passing out to the general atmosphere. Although the idea of the safety lamp had already been demonstrated by William Reid Clanny and by the then unknown (but later very famous) engineer George Stephenson, Davy's use of wire gauze to prevent the spread of flame was used by many other inventors in their later designs. There was some discussion as to whether Davy had discovered the principles behind his lamp without the help of the work of Smithson Tennant, but it was generally agreed that the work of both men had been independent. Davy refused to patent the lamp, and its invention led to him being awarded the Rumford medal in 1816.