Who first identified oxygen?
Oxygen
Oxygen was isolated by Michael Sendivogius before 1604, but it is commonly believed that the element was discovered independently by Carl Wilhelm Scheele, in Uppsala, in 1773 or earlier, and Joseph Priestley in Wiltshire, in 1774. Priority is often given for Priestley because his work was published first. Priestley, however, called oxygen "dephlogisticated air", and did not recognize it as a chemical element. The name "oxygen" was coined in 1777 by Antoine Lavoisier, who first recognized oxygen as a chemical element and correctly characterized the role it plays in combustion.
Inhalation sedation
Nitrous oxide was first discovered by Joseph Priestley in 1772. In 1795, Sir Humphrey Davy and surgeon J. B. Borlase experimented with nitrous oxide and the effects of its inhalation. Davy then published a book in 1799 hinting the possible role of nitrous oxide in achieving mild anaesthesia during surgical procedures. In 1824, Henry Hill Hickman used carbon dioxide to achieve a state of "suspended animation" in animals; successfully diminishing pain during the surgical procedure. In 1831, chloroform was discovered by Justus von Liebig in Germany, Samuel Guthrie in New York and Eugène Soubeiran in France, all of whom worked independently. In 1842, a chemist in Rochester, William Edward Clarke provided Dr. Elijah Pope with ether prior to a tooth extraction of his patient. In the same year, a doctor in Georgia, Dr. Crawford W. Long administered ether to John Venable for the removable of a neck tumour. In 1844, Dr. Horace Wells carried out an experiment on himself where he had Professor Gardner Quincy Colton administer nitrous oxide to himself prior to a wisdom tooth extraction by Dr. John Riggs. Wells discovered that he was unaware of the procedure and experienced absolutely no pain during the procedure.
Oxygen
Polish alchemist, philosopher, and physician Michael Sendivogius in his work "De Lapide Philosophorum Tractatus duodecim e naturae fonte et manuali experientia depromti" (1604) described a substance contained in air, referring to it as 'cibus vitae' (food of life), and this substance is identical with oxygen. Sendivogius, during his experiments performed between 1598 and 1604, properly recognized that the substance is equivalent to the gaseous byproduct released by the thermal decomposition of potassium nitrate. In Bugaj’s view, the isolation of oxygen and the proper association of the substance to that part of air which is required for life, lends sufficient weight to the discovery of oxygen by Sendivogius. This discovery of Sendivogius was however frequently denied by the generations of scientists and chemists which succeeded him.
Jean-François Pilâtre de Rozier
Jean-François Pilâtre de Rozier () was a French chemistry and physics teacher, and one of the first pioneers of aviation. He and François Laurent d'Arlandes made the first manned free balloon flight on 21 November 1783, in a Montgolfier balloon. He later died when his balloon crashed near Wimereux in the Pas-de-Calais during an attempt to fly across the English Channel. He and his companion, Pierre Romain, thus became the first known fatalities in an air crash. He also risked himself while researching the flammability of hydrogen: in "A Short History of Nearly Everything", Bill Bryson writes "In France, a chemist named Pilatre de Rozier tested the flammability of hydrogen by gulping a mouthful and blowing across an open flame, proving at a stroke that hydrogen is indeed explosively combustible and that eyebrows are not necessarily a permanent feature of one’s face."
Karol Olszewski
In 1883, Zygmunt Wróblewski and Karol Olszewski were the first in the world to liquefy oxygen, nitrogen and carbon dioxide from the atmosphere in a stable state (not, as had been the case up to then, in a dynamic state in the transitional form as vapor).
Oxisol
Fossil Oxisols are known from the first appearance of free oxygen in the atmosphere about 2,200 million years ago. In warm periods like the Mesozoic and Paleocene, Oxisols extended to areas that now have quite cool climates, extending well into North America and Europe. It is believed Oxisols became vegetated later than Ultisols or Alfisols, probably because vegetation took a long time to adapt to the infertility of Oxisols.
Pnictogen
The nitrogen compound sal ammoniac (ammonium chloride) has been known since the time of the Ancient Egyptians. In the 1760s two scientists, Henry Cavendish and Joseph Priestley, isolated nitrogen from air, but neither realized the presence of an undiscovered element. It was not until several years later, in 1772, that Daniel Rutherford realized that the gas was indeed nitrogen.
Oxygen cocktail
The oxygen cocktail was developed in the 1960s by the Russian academician N. N. Sirotinin. While researching the respiratory function of the stomach and the possibility of filling the body with oxygen through the digestive tract, Soviet doctors put probes into the patients’ stomachs, through which the body could be filled with up to 2 liters of oxygen. Although the condition of the patients improved considerably, this method had to be abandoned because of discomfort caused by the probes. In an alternative treatment, a foam-forming liquid was filled with oxygen and transferred to the patient’s mouth via a tube. Later, researches suggested adding the oxygen foam into food or drink. Such oxygen-enriched drinks received the name “oxygen cocktail” and were produced in sanatoriums and clinics. Since the 1970s, the method of making such drinks has undergone almost no changes, but the foam-forming ingredients and the ways of filling the cocktails with oxygen have been improved.
Sendivogius
Michael Sendivogius (; ; 1566–1636) was a Polish alchemist, philosopher, and medical doctor. A pioneer of chemistry, he developed ways of purification and creation of various acids, metals and other chemical compounds. He discovered that air is not a single substance and contains a life-giving substance-later called oxygen, 170 years before Scheele's discovery of the element. He correctly identified this 'food of life' with the gas (also oxygen) given off by heating nitre (saltpetre). This substance, the 'central nitre', had a central position in Sendivogius' schema of the universe.
Chalcogen
Early attempts to separate oxygen from air were hampered by the fact that air was thought of as a single element up to the 17th and 18th centuries. Robert Hooke, Mikhail Lomonosov, Ole Borch, and Pierre Bayden all successfully created oxygen, but did not realize it at the time. Oxygen was discovered by Joseph Priestley in 1774 when he focused sunlight on a sample of mercuric oxide and collected the resulting gas. Carl Wilhelm Scheele had also created oxygen in 1771 by the same method, but Scheele did not publish his results until 1777.
Wilhelm Reich
It was shortly after he arrived in New York in 1939 that Reich first said he had discovered a biological or cosmic energy, an extension of Freud's idea of the libido. He called it "orgone energy" or "orgone radiation", and the study of it "orgonomy". Reich said he had seen orgone when he injected his mice with bions and in the sky at night through an "organoscope", a special telescope. He argued that it is in the soil and air (indeed, is omnipresent), is blue or blue-grey, and that humanity had divided its knowledge of it in two: aether for the physical aspect and God for the spiritual. The colour of the sky, the northern lights, St Elmo's Fire, and the blue of sexually excited frogs are manifestations of orgone, he wrote. He also argued that protozoa, red corpuscles, cancer cells and the chlorophyll of plants are charged with it.
Nonmetal
Hydrogen: Cavendish, in 1766, was the first to distinguish hydrogen from other gases, although Paracelsus around 1500, Robert Boyle (1670), and Joseph Priestley (?) had observed its production by reacting strong acids with metals. Lavoisier named it in 1793. Oxygen: Carl Wilhelm Scheele obtained oxygen by heating mercuric oxide and nitrates in 1771, but did not publish his findings until 1777. Priestley also prepared this new "air" by 1774, but only Lavoisier recognized it as a true element; he named it in 1777. Nitrogen: Rutherford discovered nitrogen while he was studying at the University of Edinburgh. He showed that the air in which animals breathed, after removal of exhaled carbon dioxide, was no longer able to burn a candle. Scheele, Henry Cavendish, and Priestley also studied this element at about the same time; Lavoisier named it in 1775 or 1776. Tellurium: In 1783, Franz-Joseph Müller von Reichenstein, who was then serving as the Austrian chief inspector of mines in Transylvania, concluded that a new element was present in a gold ore from the mines in Zlatna, near today's city of Alba Iulia, Romania. In 1789, a Hungarian scientist, Pál Kitaibel, discovered the element independently in an ore from Deutsch-Pilsen that had been regarded as argentiferous molybdenite, but later he gave the credit to Müller. In 1798, it was named by Martin Heinrich Klaproth, who had earlier isolated it from the mineral calaverite. Chlorine: In 1774, Scheele obtained chlorine from hydrochloric acid but thought it was an oxide. Only in 1808 did Humphry Davy recognize it as an element.
Doubly ionized oxygen
These emission lines were first discovered in the spectra of planetary nebulae in the 1860s. At that time, they were thought to be due to a new element which was named "nebulium". In 1927, Ira Sprague Bowen came up with the current explanation of them being due to doubly ionized oxygen.
Otto Hahn
In February 1921, Otto Hahn published the first report on his discovery of uranium Z (later known as Pa ), the first example of nuclear isomerism. Gerlach remarked that this was "a discovery that was not understood at the time but later became highly significant for nuclear physics". Not until 1936 did Carl Friedrich von Weizsäcker provide a theoretical explanation of the phenomenon of nuclear isomerism. For this discovery, whose full significance was recognized by very few, Hahn was again proposed, from 1923 till 1929, for the Nobel Prize in Chemistry by Naunyn, Goldschmidt, and Max Planck.
Exhaled nitric oxide
NO was first detected in exhaled breath samples in 1991. In 1992, NO was voted molecule of the year by the scientific journal "Science". In 1993, researchers from the Karolinska Institute in Sweden were the first to report increased eNO in asthmatics.
Aerobic exercise
British physiologist Archibald Hill introduced the concepts of maximal oxygen uptake and oxygen debt in 1922. Hill and German physician Otto Meyerhof shared the 1922 Nobel Prize in Physiology or Medicine for their independent work related to muscle energy metabolism. Building on this work, scientists began measuring oxygen consumption during exercise. Notable contributions were made by Henry Taylor at the University of Minnesota, Scandinavian scientists Per-Olof Åstrand and Bengt Saltin in the 1950s and 60s, the Harvard Fatigue Laboratory, German universities, and the Copenhagen Muscle Research Centre among others.
Nitrous oxide (medication)
Breathing the pure gas often caused hypoxia (oxygen insufficiency) and sometimes death by asphyxiation. Eventually practitioners became aware of the need to provide at least 21% oxygen content in the gas (the same percentage as in air). In 1911, the anaesthetist Arthur Ernest Guedel first described the use of self-administration of a nitrous oxide and oxygen mix. It was not until 1961 that the first paper was published by Michael Tunstall and others, describing the administration of a pre-mixed 50:50 nitrous oxide and oxygen mix, which led to the commercialisation of the product.
Acid–base reaction
The first scientific concept of acids and bases was provided by Lavoisier in around 1776. Since Lavoisier's knowledge of strong acids was mainly restricted to oxoacids, such as (nitric acid) and (sulfuric acid), which tend to contain central atoms in high oxidation states surrounded by oxygen, and since he was not aware of the true composition of the hydrohalic acids (HF, HCl, HBr, and HI), he defined acids in terms of their containing "oxygen", which in fact he named from Greek words meaning "acid-former" (from the Greek οξυς ("oxys") meaning "acid" or "sharp" and γεινομαι ("geinomai") meaning "engender"). The Lavoisier definition held for over 30 years, until the 1810 article and subsequent lectures by Sir Humphry Davy in which he proved the lack of oxygen in , HTe, and the hydrohalic acids. However, Davy failed to develop a new theory, concluding that "acidity does not depend upon any particular elementary substance, but upon peculiar arrangement of various substances". One notable modification of oxygen theory was provided by Berzelius, who stated that acids are oxides of nonmetals while bases are oxides of metals.
History of chemistry
In 1773, Swedish chemist Carl Wilhelm Scheele discovered oxygen, which he called "fire air", but did not immediately publish his achievement. In 1774, English chemist Joseph Priestley independently isolated oxygen in its gaseous state, calling it "dephlogisticated air", and published his work before Scheele. During his lifetime, Priestley's considerable scientific reputation rested on his invention of soda water, his writings on electricity, and his discovery of several "airs" (gases), the most famous being what Priestley dubbed "dephlogisticated air" (oxygen). However, Priestley's determination to defend phlogiston theory and to reject what would become the chemical revolution eventually left him isolated within the scientific community.
Cardiopulmonary bypass
The oxygenator was first conceptualized in the 17th century by Robert Hooke and developed into practical extracorporeal oxygenators by French and German experimental physiologists in the 19th century. Bubble oxygenators have no intervening barrier between blood and oxygen, these are called 'direct contact' oxygenators. Membrane oxygenators introduce a gas-permeable membrane between blood and oxygen that decreases the blood trauma of direct-contact oxygenators. Much work since the 1960s focused on overcoming the gas exchange handicap of the membrane barrier, leading to the development of high-performance microporous hollow-fibre oxygenators that eventually replaced direct-contact oxygenators in cardiac theatres.
Pneumatic Institution
After Lavoisier had established the role of oxygen in animal respiration, members of the Lunar Society, such as Joseph Priestley (who had co-discovered oxygen), originated pneumatic chemistry, which eventually led to the establishment of the Pneumatic Institution.
Absolute zero
With a better theoretical understanding of absolute zero, scientists were eager to reach this temperature in the lab. By 1845, Michael Faraday had managed to liquefy most gases then known to exist, and reached a new record for lowest temperatures by reaching . Faraday believed that certain gases, such as oxygen, nitrogen, and hydrogen, were permanent gases and could not be liquefied. Decades later, in 1873 Dutch theoretical scientist Johannes Diderik van der Waals demonstrated that these gases could be liquefied, but only under conditions of very high pressure and very low temperatures. In 1877, Louis Paul Cailletet in France and Raoul Pictet in Switzerland succeeded in producing the first droplets of liquid air . This was followed in 1883 by the production of liquid oxygen by the Polish professors Zygmunt Wróblewski and Karol Olszewski.
Bowood House
The remaining house is still large, and the front wing is open to the public with rooms, paintings and sculpture on display. One of the rooms was the laboratory of Joseph Priestley, who discovered oxygen there on 1 August 1774. In the year 2000 Bowood House was designated an ACS National Historic Chemical Landmark in recognition of the importance of Priestley's discovery.
Oxygen toxicity
Victorian society had a fascination for the rapidly expanding field of science. In "Dr. Ox's Experiment", a short story written by Jules Verne in 1872, the eponymous doctor uses electrolysis of water to separate oxygen and hydrogen. He then pumps the pure oxygen throughout the town of Quiquendone, causing the normally tranquil inhabitants and their animals to become aggressive and plants to grow rapidly. An explosion of the hydrogen and oxygen in Dr Ox's factory brings his experiment to an end. Verne summarised his story by explaining that the effects of oxygen described in the tale were his own invention. There is also a brief episode of oxygen intoxication in his "From the Earth to the Moon".
Humphry Davy
Sir Humphry Davy, 1st Baronet (17 December 177829 May 1829) was a Cornish chemist and inventor, who is best remembered today for isolating, using electricity, a series of elements for the first time: potassium and sodium in 1807 and calcium, strontium, barium, magnesium and boron the following year, as well as discovering the elemental nature of chlorine and iodine. He also studied the forces involved in these separations, inventing the new field of electrochemistry. In 1799 Davy experimented with nitrous oxide and became astonished that it made him laugh, so he nicknamed it "laughing gas", and wrote about its potential anaesthetic properties in relieving pain during surgery.
Oxygen
The French chemist Antoine Laurent Lavoisier later claimed to have discovered the new substance independently. Priestley visited Lavoisier in October 1774 and told him about his experiment and how he liberated the new gas. Scheele also dispatched a letter to Lavoisier on September 30, 1774, that described his discovery of the previously unknown substance, but Lavoisier never acknowledged receiving it (a copy of the letter was found in Scheele's belongings after his death).
Lavoisier conducted the first adequate quantitative experiments on oxidation and gave the first correct explanation of how combustion works. He used these and similar experiments, all started in 1774, to discredit the phlogiston theory and to prove that the substance discovered by Priestley and Scheele was a chemical element.
Christian Friedrich Schönbein
It was while doing experiments on the electrolysis of water at the University of Basel that Schönbein first began to notice a distinctive odor in his laboratory. This smell gave Schönbein the clue to the presence of a new product from his experiments. Because of the pronounced smell, Schönbein coined the term "ozone" for the new gas, from the Greek word "ozein", meaning "to smell". Schönbein described his discoveries in publications in 1840. He later found that the smell of ozone was similar to that produced by the slow oxidation of white phosphorus.
John Scott Haldane
Haldane helped determine the regulation of breathing, and discovered the Haldane effect in haemoglobin. He was the founder of "The Journal of Hygiene". In 1907 Haldane made a decompression chamber to help make deep-sea divers safer and produced the first decompression tables after extensive experiments with animals. He was also an authority on the effects of pulmonary diseases, such as silicosis caused by inhaling silica dust. After being forced out of combatting poison gases in World War I, through alleged German sympathies, he shifted into working with victims of gas warfare and developed oxygen treatment including the oxygen tent.
Carbon dioxide
Carbon dioxide was first liquefied (at elevated pressures) in 1823 by Humphry Davy and Michael Faraday. The earliest description of solid carbon dioxide was given by Adrien-Jean-Pierre Thilorier, who in 1835 opened a pressurized container of liquid carbon dioxide, only to find that the cooling produced by the rapid evaporation of the liquid yielded a "snow" of solid .
South West England
Jan Ingenhousz, the Dutch biologist discovered photosynthesis in 1779 at Bowood House in Wiltshire; on 1 August 1774, Joseph Priestley discovered oxygen at Bowood House. A fossil of the oldest ancestor of the Tyrannosaurus was found in Gloucestershire; Mary Anning was a famous fossil collector from Lyme Regis. Edward Jenner was from Gloucestershire.
Oxygen
"Oxygen" entered the English language despite opposition by English scientists and the fact that the Englishman Priestley had first isolated the gas and written about it. This is partly due to a poem praising the gas titled "Oxygen" in the popular book "The Botanic Garden" (1791) by Erasmus Darwin, grandfather of Charles Darwin.
John Dalton's original atomic hypothesis presumed that all elements were monatomic and that the atoms in compounds would normally have the simplest atomic ratios with respect to one another. For example, Dalton assumed that water's formula was HO, leading to the conclusion that the atomic mass of oxygen was 8 times that of hydrogen, instead of the modern value of about 16. In 1805, Joseph Louis Gay-Lussac and Alexander von Humboldt showed that water is formed of two volumes of hydrogen and one volume of oxygen; and by 1811 Amedeo Avogadro had arrived at the correct interpretation of water's composition, based on what is now called Avogadro's law and the diatomic elemental molecules in those gases.
Edward W. Morley
Edward Williams Morley (January 29, 1838 – February 24, 1923) was an American scientist famous for his extremely precise and accurate measurement of the atomic weight of oxygen and for the Michelson–Morley experiment.
List of artworks in the collection of the Royal Society of Chemistry
English theologian, philosopher and chemist, Joseph Priestley is credited with the discovery of oxygen.
Allotropes of oxygen
Triatomic oxygen (ozone, O), is a very reactive allotrope of oxygen that is destructive to materials like rubber and fabrics and is also damaging to lung tissue. Traces of it can be detected as a sharp, chlorine-like smell, coming from electric motors, laser printers, and photocopiers. It was named "ozone" by Christian Friedrich Schönbein, in 1840, from the Greek word ὠζώ (ozo) for smell.
Industrial gas
The history of chemistry tells us that a number of gases were identified and either discovered or first made in relatively pure form during the Industrial Revolution of the 18th and 19th centuries by notable chemists in their laboratories. The timeline of attributed discovery for various gases are carbon dioxide (1754), hydrogen (1766), nitrogen (1772), nitrous oxide (1772) 
, oxygen (1773) 
, ammonia (1774), chlorine (1774), methane (1776), hydrogen sulfide (1777), carbon monoxide (1800), hydrogen chloride (1810), acetylene (1836), helium (1868) fluorine (1886), argon (1894), krypton, neon and xenon (1898)
Joseph Priestley
Additional recognition for Priestley's work is marked by a National Historic Chemical Landmark designation for his discovery of oxygen, made on 1 August 1994, at the Priestley House in Northumberland, Penn., by the American Chemical Society. Similar recognition was made on 7 August 2000, at Bowood House in Wiltshire, England. The ACS also awards their highest honour, the Priestley Medal, in his name.
Oxygen
By the late 19th century scientists realized that air could be liquefied and its components isolated by compressing and cooling it. Using a cascade method, Swiss chemist and physicist Raoul Pierre Pictet evaporated liquid sulfur dioxide in order to liquefy carbon dioxide, which in turn was evaporated to cool oxygen gas enough to liquefy it. He sent a telegram on December 22, 1877 to the French Academy of Sciences in Paris announcing his discovery of liquid oxygen. Just two days later, French physicist Louis Paul Cailletet announced his own method of liquefying molecular oxygen. Only a few drops of the liquid were produced in each case and no meaningful analysis could be conducted. Oxygen was liquefied in a stable state for the first time on March 29, 1883 by Polish scientists from Jagiellonian University, Zygmunt Wróblewski and Karol Olszewski.
Chemistry
Before his work, though, many important discoveries had been made, specifically relating to the nature of 'air' which was discovered to be composed of many different gases. The Scottish chemist Joseph Black (the first experimental chemist) and the Dutchman J.B. van Helmont discovered carbon dioxide, or what Black called 'fixed air' in 1754; Henry Cavendish discovered hydrogen and elucidated its properties and Joseph Priestley and, independently, Carl Wilhelm Scheele isolated pure oxygen.
Nitrous oxide
The first important use of nitrous oxide was made possible by Thomas Beddoes and James Watt, who worked together to publish the book "Considerations on the Medical Use and on the Production of Factitious Airs (1794)". This book was important for two reasons. First, James Watt had invented a novel machine to produce "Factitious Airs" (i.e. nitrous oxide) and a novel "breathing apparatus" to inhale the gas. Second, the book also presented the new medical theories by Thomas Beddoes, that tuberculosis and other lung diseases could be treated by inhalation of "Factitious Airs".
The machine to produce "Factitious Airs" had three parts: a furnace to burn the needed material, a vessel with water where the produced gas passed through in a spiral pipe (for impurities to be "washed off"), and finally the gas cylinder with a gasometer where the gas produced, "air", could be tapped into portable air bags (made of airtight oily silk). The breathing apparatus consisted of one of the portable air bags connected with a tube to a mouthpiece. With this new equipment being engineered and produced by 1794, the way was paved for clinical trials, which began in 1798 when Thomas Beddoes established the ""Pneumatic Institution for Relieving Diseases by Medical Airs"" in Hotwells (Bristol). In the basement of the building, a large-scale machine was producing the gases under the supervision of a young Humphry Davy, who was encouraged to experiment with new gases for patients to inhale. The first important work of Davy was examination of the nitrous oxide, and the publication of his results in the book: "Researches, Chemical and Philosophical (1800)". In that publication, Davy notes the analgesic effect of nitrous oxide at page 465 and its potential to be used for surgical operations at page 556. Davy coined the name "laughing gas" for nitrous oxide.
Leland Clark
Leland C. Clark Jr. (December 4, 1918 – September 25, 2005) was an American biochemist born in Rochester, New York. He is most well known as the inventor of the Clark electrode, a device used for measuring oxygen in blood, water and other liquids. Clark is considered the "father of biosensors", and the modern-day glucose sensor used daily by millions of diabetics is based on his research. He conducted pioneering research on heart-lung machines in the 1940s and '50s and was holder of more than 25 patents. Although he developed a fluorocarbon-based liquid that could be breathed successfully by mice in place of air, his lifelong goal of developing artificial blood remained unfulfilled at the time of his death. He is the inventor of Oxycyte, a third-generation perfluorocarbon (PFC) therapeutic oxygen carrier designed to enhance oxygen delivery to damaged tissues.
Chemistry: A Volatile History
Lavoisier had successfully dispensed with the need for the theory of phlogiston and recognised Priestley's ‘dephlogisticated air’ as the element oxygen. Despite the fact it was Priestley's original work that laid the foundations for his discovery, Lavoisier claimed he had discovered oxygen; Priestley, after all, had failed to recognise it as a new element.
Allotropes of oxygen
The common allotrope of elemental oxygen on Earth, , is generally known as oxygen, but may be called "dioxygen", "diatomic oxygen", "molecular oxygen", or "oxygen gas" to distinguish it from the element itself and from the triatomic allotrope "ozone," . As a major component (about 21% by volume) of Earth's atmosphere, elemental oxygen is most commonly encountered in the diatomic form. Aerobic organisms utilize atmospheric dioxygen as the terminal oxidant in cellular respiration. The ground state of dioxygen is known as triplet oxygen, O, because it has two unpaired electrons. The first excited state, singlet oxygen, ""O has no unpaired electrons and is metastable.
Pneumatic chemistry
Van Helmont (1579 – 1644) is sometimes considered the founder of pneumatic chemistry, as he was the first natural philosopher to take an interest in air as a reagent. Alessandro Volta began investigating pneumatic chemistry in 1776 and argued that there were different types of inflammable air based on experiments on marsh gases. Pneumatic chemists credited with discovering chemical elements include Joseph Priestley, Henry Cavendish, Joseph Black, Daniel Rutherford, and Carl Scheele. Other individuals who investigated gases during this period include Robert Boyle, Stephen Hales, William Brownrigg, Antoine Lavoisier, Joseph Louis Gay-Lussac, and John Dalton.
Eudiometer
In 1772, Joseph Priestley began experimenting with different “airs” using his own redesigned pneumatic trough in which mercury instead of water would trap gases that were usually soluble in water. From these experiments Priestley is credited with discovering many new gases such as oxygen, hydrogen chloride, and ammonia. He also discovered a way to find the purity or “goodness” of air using “nitrous air test”. This test was conducted by mixing nitrous gas with a test sample of another gas and trapping it in the pneumatic trough, essentially the greater the decrease in volume, the more pure the sample of gas was (key principle in eudiometry). Henry Cavendish later used a similar device to determine the fraction of oxygen in the Earth's atmosphere.
Gas
The word "gas" was first used by the early 17th-century Flemish chemist Jan Baptist van Helmont. He identified carbon dioxide, the first known gas other than air. Van Helmont's word appears to have been simply a phonetic transcription of the Ancient Greek word χάος "Chaos" – the "g" in Dutch being pronounced like "ch" in "loch" (voiceless velar fricative, IPA |x]) – in which case Van Helmont was simply following the established alchemical usage first attested in the works of Paracelsus. According to Paracelsus's terminology, "chaos" meant something like "ultra-rarefied water".
William Giauque
His correlated investigations of the entropy of oxygen with Dr. Herrick L. Johnston, led to the discovery of oxygen isotopes 17 and 18 in the Earth's atmosphere and showed that physicists and chemists had been using different scales of atomic weight for years without recognising it.
Oxygen toxicity
Pulmonary oxygen toxicity was first described by J. Lorrain Smith in 1899 when he noted central nervous system toxicity and discovered in experiments in mice and birds that had no effect but of oxygen was a pulmonary irritant. Pulmonary toxicity may be referred to as the "Lorrain Smith effect". The first recorded human exposure was undertaken in 1910 by Bornstein when two men breathed oxygen at for 30 minutes while he went on to 48 minutes with no symptoms. In 1912, Bornstein developed cramps in his hands and legs while breathing oxygen at for 51 minutes. Smith then went on to show that intermittent exposure to a breathing gas with less oxygen permitted the lungs to recover and delayed the onset of pulmonary toxicity.
Ola Didrik Saugstad
In 1980, Saugstad was the first to demonstrate that oxygenation after a period of asphyxia could result in an explosive increase in oxygen radicals. In the late 1980s, Saugstad and Rooth published a seminal article questioning the use of 100% oxygen in the resuscitation of newborn children. This would lead to his major discovery of the dangers of using 100% oxygen, resulting in the amendment of the international guidelines for newborn resuscitation in 2010 based on the research of Saugstad and his team. Saugstad has described the use of 100% oxygen as "one of the largest scandals in the history of medicine." It is estimated that his discovery can save the lives of 200,000 children each year.
Natural science
Significant advances in chemistry also took place during the scientific revolution. Antoine Lavoisier, a French chemist, refuted the phlogiston theory, which posited that things burned by releasing "phlogiston" into the air. Joseph Priestley had discovered oxygen in the 18th century, but Lavoisier discovered that combustion was the result of oxidation. He also constructed a table of 33 elements and invented modern chemical nomenclature. Formal biological science remained in its infancy in the 18th century, when the focus lay upon the classification and categorization of natural life. This growth in natural history was led by Carl Linnaeus, whose 1735 taxonomy of the natural world is still in use. Linnaeus in the 1750s introduced scientific names for all his species.
Glucose meter
Leland Clark presented his first paper about the oxygen electrode, later named the Clark electrode, on 15 April 1956, at a meeting of the American Society for Artificial Organs during the annual meetings of the Federated Societies for Experimental Biology.
In 1962, Clark and Ann Lyons from the Cincinnati Children’s Hospital developed the first glucose enzyme electrode. This biosensor was based on a thin layer of glucose oxidase (GOx) on an oxygen electrode. Thus, the readout was the amount of oxygen consumed by GOx during the enzymatic reaction with the substrate glucose. This publication became one of the most often cited papers in life sciences. Due to this work he is considered the “father of biosensors,” especially with respect to the glucose sensing for diabetes patients.
Another early glucose meter was the Ames Reflectance Meter by Anton H. Clemens. It was used in American hospitals in the 1970s. A moving needle indicated the blood glucose after about a minute.
Neon
Neon was discovered in 1898 by the British chemists Sir William Ramsay (1852–1916) and Morris W. Travers (1872–1961) in London. Neon was discovered when Ramsay chilled a sample of air until it became a liquid, then warmed the liquid and captured the gases as they boiled off. The gases nitrogen, oxygen, and argon had been identified, but the remaining gases were isolated in roughly their order of abundance, in a six-week period beginning at the end of May 1898. First to be identified was krypton. The next, after krypton had been removed, was a gas which gave a brilliant red light under spectroscopic discharge. This gas, identified in June, was named "neon", the Greek analogue of the Latin "novum" ('new') suggested by Ramsay's son. The characteristic brilliant red-orange color emitted by gaseous neon when excited electrically was noted immediately. Travers later wrote: "the blaze of crimson light from the tube told its own story and was a sight to dwell upon and never forget."
Oxygen
One of the first known experiments on the relationship between combustion and air was conducted by the 2nd century BCE Greek writer on mechanics, Philo of Byzantium. In his work "Pneumatica", Philo observed that inverting a vessel over a burning candle and surrounding the vessel's neck with water resulted in some water rising into the neck. Philo incorrectly surmised that parts of the air in the vessel were converted into the classical element fire and thus were able to escape through pores in the glass. Many centuries later Leonardo da Vinci built on Philo's work by observing that a portion of air is consumed during combustion and respiration.
Joseph Priestley
Priestley assembled his oxygen paper and several others into a second volume of "Experiments and Observations on Air", published in 1776. He did not emphasise his discovery of "dephlogisticated air" (leaving it to Part III of the volume) but instead argued in the preface how important such discoveries were to rational religion. His paper narrated the discovery chronologically, relating the long delays between experiments and his initial puzzlements; thus, it is difficult to determine when exactly Priestley "discovered" oxygen. Such dating is significant as both Lavoisier and Swedish pharmacist Carl Wilhelm Scheele have strong claims to the discovery of oxygen as well, Scheele having been the first to isolate the gas (although he published after Priestley) and Lavoisier having been the first to describe it as purified "air itself entire without alteration" (that is, the first to explain oxygen without phlogiston theory).
Ralph Keeling
Ralph Keeling developed his first scientific instrument, a light-gauging interferometer for the accurate measurement of atmospheric oxygen, as part of his Ph.D. research. By October 25, 1986, Keeling had developed a working prototype, a stainless steel box about seven feet tall, with a glass front. Inside the box, light beams shine through the gas molecules of air samples. Keeling's interferometer measures the speed of light at different wavelengths and determines the specific composition of the air and its oxygen content based on tiny variations in speed. The instrument Keeling developed was able to measure oxygen at a far more precise level than anything previously created, detecting differences of a few molecules per million.
List of multiple discoveries
Commonly cited examples of multiple independent discovery are the 17th-century independent formulation of calculus by Isaac Newton, Gottfried Wilhelm Leibniz and others, described by A. Rupert Hall; the 18th-century discovery of oxygen by Carl Wilhelm Scheele, Joseph Priestley, Antoine Lavoisier and others; and the theory of the evolution of species, independently advanced in the 19th century by Charles Darwin and Alfred Russel Wallace.
Herschel Space Observatory
It was reported on 1 August 2011, that molecular oxygen had been definitively confirmed in space with the "Herschel Space Telescope", the second time scientists have found the molecule in space. It had been previously reported by the Odin team.
Royal Observatory, Cape of Good Hope
In 1897 Frank McClean, a close friend of Gill's and the donor of the McClean telescope, discovered the presence of oxygen in a number of stars using an objective prism attached to the Astrographic Telescope.
Octave Boudouard
Octave Leopold Boudouard became a professor at the Conservatoire National des Arts et Métiers in Paris. He worked in various fields of applied chemistry, such as the chemistry of fuels and clays. His most important work was his research into chemical equilibria when reducing iron oxides in a blast furnace. In 1901 he proposed the first theory of the hydrogenation of carbon monoxide, where he considered that metal oxide was reacting with carbon. In 1905 Boudouard identified the Boudouard reaction, where carbon and carbon dioxide combine to form carbon monoxide at high temperatures, while the reverse occurs at lower temperatures. In 1912 he published a paper on the odors of Paris, researching the chemicals polluting the air of that city.
Oxygen
In 1891 Scottish chemist James Dewar was able to produce enough liquid oxygen for study. The first commercially viable process for producing liquid oxygen was independently developed in 1895 by German engineer Carl von Linde and British engineer William Hampson. Both men lowered the temperature of air until it liquefied and then distilled the component gases by boiling them off one at a time and capturing them separately. Later, in 1901, oxyacetylene welding was demonstrated for the first time by burning a mixture of acetylene and compressed . This method of welding and cutting metal later became common.
Exercise physiology
British physiologist Archibald Hill introduced the concepts of maximal oxygen uptake and oxygen debt in 1922. Hill and German physician Otto Meyerhof shared the 1922 Nobel Prize in Physiology or Medicine for their independent work related to muscle energy metabolism. Building on this work, scientists began measuring oxygen consumption during exercise. Notable contributions were made by Henry Taylor at the University of Minnesota, Scandinavian scientists Per-Olof Åstrand and Bengt Saltin in the 1950s and 60s, the Harvard Fatigue Laboratory, German universities, and the Copenhagen Muscle Research Centre among others.
Hemoglobin
The oxygen-carrying property of hemoglobin was discovered by Hünefeld in 1840. In 1851, German physiologist Otto Funke published a series of articles in which he described growing hemoglobin crystals by successively diluting red blood cells with a solvent such as pure water, alcohol or ether, followed by slow evaporation of the solvent from the resulting protein solution. Hemoglobin's reversible oxygenation was described a few years later by Felix Hoppe-Seyler.
Oxygen
In 1923, the American scientist Robert H. Goddard became the first person to develop a rocket engine that burned liquid fuel; the engine used gasoline for fuel and liquid oxygen as the oxidizer. Goddard successfully flew a small liquid-fueled rocket 56 m at 97 km/h on March 16, 1926 in Auburn, Massachusetts, US.
Chlorine
Chlorine dioxide (ClO) was the first chlorine oxide to be discovered in 1811 by Humphry Davy. It is a yellow paramagnetic gas (deep-red as a solid or liquid), as expected from its having an odd number of electrons: it is stable towards dimerisation due to the delocalisation of the unpaired electron. It explodes above −40 °C as a liquid and under pressure as a gas and therefore must be made at low concentrations for wood-pulp bleaching and water treatment. It is usually prepared by reducing a chlorate as follows:
Its production is thus intimately linked to the redox reactions of the chlorine oxoacids. It is a strong oxidising agent, reacting with sulfur, phosphorus, phosphorus halides, and potassium borohydride. It dissolves exothermically in water to form dark-green solutions that very slowly decompose in the dark. Crystalline clathrate hydrates ClO·"n"HO ("n" ≈ 6–10) separate out at low temperatures. However, in the presence of light, these solutions rapidly photodecompose to form a mixture of chloric and hydrochloric acids. Photolysis of individual ClO molecules result in the radicals ClO and ClOO, while at room temperature mostly chlorine, oxygen, and some ClO and ClO are produced. ClO is also produced when photolysing the solid at −78 °C: it is a dark brown solid that explodes below 0 °C. The ClO radical leads to the depletion of atmospheric ozone and is thus environmentally important as follows:
David Catling
In the area of the evolution of the Earth’s atmosphere, Catling is known for a theory explaining how the Earth’s crust accumulated large quantities of oxidized minerals and how the atmosphere became rich in oxygen. Geological records show that oxygen flooded the atmosphere in a Great Oxidation Event (GOE) about 2.4 billion years ago, even though bacteria that produced oxygen likely evolved hundreds of millions of years earlier. Catling’s theory proposes that biological oxygen was initially used by reactions with chemicals in the environment; gradually, however, Earth’s environment shifted to a tipping point where oxygen flooded the air. Atmospheric methane is the key part of this theory. Before oxygen was abundant, methane gas could reach concentrations hundreds of times greater than today’s 1.8 parts per million. Ultraviolet light decomposes methane molecules in the upper atmosphere, causing hydrogen gas to escape into space. Over time, the irreversible atmospheric escape of hydrogen– a powerful reducing agent -caused Earth to oxidize and reach the GOE tipping point.
Other studies about Earth’s atmospheric oxygen have considered its second increase around 600 million years ago that acted as a precursor to the rise of animal life. Catling proposed looking at oxygen-sensitive variations in stable isotopes of selenium to trace atmospheric and seawater oxygen, and the results of such a study showed that Earth's second increase in oxygen occurred in fits and starts spread over about 100 million years.
Oxygen mask
The first successful creation for the oxygen mask was by Armenian born Dr. Arthur Bulbulian, in the field of facial prosthetics, in 1941.
Henri Buisson
Buisson and Charles Fabry discovered the ozone layer in 1913.
Chappuis absorption
James Chappuis was the first researcher (in 1880) to notice that light passing through ozone gas has a blue tint. He attributed this effect to absorption in the yellow, orange, and red parts of the light spectrum. The French chemist Auguste Houzeau had already shown in 1858 that the atmosphere contains traces of ozone, so Chappuis presumed that ozone could explain the blue color of the sky. He was certainly aware that this was not the only possible explanation, since the blue light that can be seen from Earth's surface is polarised. Polarization cannot be explained by light absorption by ozone, but can be explained by Rayleigh scattering, which was already known by Chappuis's time. Contemporary scientists thought that Rayleigh scattering was sufficient to explain the blue sky, and so the idea that ozone could play a role was eventually forgotten.
Experiments and Observations on Different Kinds of Air
After the publication of the first volume of "Experiments and Observations", Priestley undertook another set of experiments. In August 1774 he isolated an "air" that appeared to be completely new, but he did not have an opportunity to pursue the matter because he was about to tour Europe with Shelburne. While in Paris, however, Priestley managed to replicate the experiment for others, including Antoine Lavoisier. After returning to Britain in January 1775, he continued his experiments and discovered vitriolic acid air (sulphur dioxide, SO). In March he wrote to several people regarding the new "air" that he had discovered several months earlier. One of these letters was read aloud to the Royal Society, and he published a paper in "Philosophical Transactions" titled "An Account of further Discoveries in Air." Priestley called the new substance "dephlogisticated air" and described it as "five or six times better than common air for the purpose of respiration, inflammation, and, I believe, every other use of common atmospherical air." He had discovered oxygen gas (O). As revised for "Experiments and Observations", his paper begins:
Karl Samuel Leberecht Hermann
Cadmium was discovered in 1817 by a physician, Friedrich Stromeyer (1776–1835). The element was first found in the condensation of vapors (mixed with soot and zinc oxide) that rose out of a furnace in which zinc oxide was being roasted. Cadmium’s discovery is also loosely attributed to K.S.L. Hermann and J.C.H. Roloff who may have found cadmium in zinc oxide during the same year. A historical debate still remains as to who actually discovered the pure form of the element first. 
The phase of scientific history in which Stromeyer was active was one in which chemical discovery was being accomplished primarily by pharmacists, apothecaries and physicians. The practice of alchemy was dying out, and chemistry was just beginning to emerge as a separate science. Stromeyer, a professor at the University of Göttingen, was testing zinc oxide, a medicine in those days, for purity.
Phlogiston theory
Joseph Black's student Daniel Rutherford discovered nitrogen in 1772 and the pair used the theory to explain his results. The residue of air left after burning, in fact a mixture of nitrogen and carbon dioxide, was sometimes referred to as "phlogisticated air," having taken up all of the phlogiston. Conversely, when Joseph Priestley discovered oxygen, he believed it to be "dephlogisticated air," capable of combining with more phlogiston and thus supporting combustion for longer than ordinary air.
Thomas Henry (apothecary)
In 1776, Thomas Henry speculated tongue in cheek that Joseph Priestley’s newly discovered dephlogisticated air (now called oxygen) might become “as fashionable as French wine at the fashionable taverns”. He did not expect, however, that tavern goers would “relish calling for a bottle of Air, instead of Claret”.
Science in the Age of Enlightenment
Lavoisier subsequently discovered and named oxygen, described its role in animal respiration and the calcination of metals exposed to air (1774–1778). In 1783, Lavoisier found that water was a compound of oxygen and hydrogen. Lavoisier’s years of experimentation formed a body of work that contested phlogiston theory. After reading his “Reflections on Phlogiston” to the Academy in 1785, chemists began dividing into camps based on the old phlogiston theory and the new oxygen theory. A new form of chemical nomenclature, developed by Louis Bernard Guyton de Morveau, with assistance from Lavoisier, classified elements binomially into a genus and a species. For example, burned lead was of the genus oxide and species lead. Transition to and acceptance of Lavoisier’s new chemistry varied in pace across Europe. The new chemistry was established in Glasgow and Edinburgh early in the 1790s, but was slow to become established in Germany. Eventually the oxygen-based theory of combustion drowned out the phlogiston theory and in the process created the basis of modern chemistry.
Tetraoxygen
The tetraoxygen molecule (O), also called oxozone, was first predicted in 1924 by Gilbert N. Lewis, who proposed it as an explanation for the failure of liquid oxygen to obey Curie's law. Today it seems Lewis was off, but not by much: computer simulations indicate that although there are no stable O molecules in liquid oxygen, O molecules do tend to associate in pairs with antiparallel spins, forming transient O units. In 1999, researchers thought that solid oxygen existed in its ε-phase (at pressures above 10 GPa) as O. However, in 2006, it was shown by X-ray crystallography that this stable phase known as ε oxygen or red oxygen is in fact . Nevertheless, positively charged tetraoxygen has been detected as a short-lived chemical species in mass spectrometry experiments.
Edward W. Morley
In chemistry, his original field, Morley had worked on determining accurate values for the composition of the atmosphere and the weights of its gases. His work on the atomic weight of oxygen covered a period of eleven years. Much time was spent in the calibration of instruments and improving the measurement accuracy to the highest possible degree (ca. 1 part per 10,000). In 1895 he introduced a new value for the atomic weight ratio of oxygen to hydrogen, providing the most precise determination of the atomic weight of oxygen at the time. His research on the atomic weight of oxygen was recognized as a National Historic Chemical Landmark by the American Chemical Society in 1995.
Tadeusz Estreicher
Estreicher studied in Berlin, Leipzig, and in London under William Ramsay. As a student at the Jagiellonian University, Estreicher worked as an assistant to Karol Olszewski, the first chemist to liquefy oxygen. After having been appointed assistant in 1899, Estreicher successfully liquefied hydrogen in 1901 before he was promoted to "Privatdozent" in 1904.
Scientific Revolution
Great advances in science have been termed "revolutions" since the 18th century. In 1747, Clairaut wrote that "Newton was said in his own life to have created a revolution". The word was also used in the preface to Lavoisier's 1789 work announcing the discovery of oxygen. "Few revolutions in science have immediately excited so much general notice as the introduction of the theory of oxygen ... Lavoisier saw his theory accepted by all the most eminent men of his time, and established over a great part of Europe within a few years from its first promulgation."
Iodine
Courtois gave samples to his friends, Charles Bernard Desormes (1777–1838) and Nicolas Clément (1779–1841), to continue research. He also gave some of the substance to chemist Joseph Louis Gay-Lussac (1778–1850), and to physicist André-Marie Ampère (1775–1836). On 29 November 1813, Desormes and Clément made Courtois' discovery public. They described the substance to a meeting of the Imperial Institute of France. On 6 December, 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 ("ioeidēs") for violet (because of the colour of iodine vapor). Ampère had given some of his sample to English chemist Humphry Davy (1778–1829), who experimented on the substance and noted its similarity to chlorine. Davy sent a letter dated 10 December 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.
Xenon
Xenon and the other noble gases were for a long time considered to be completely chemically inert and not able to form compounds. However, while teaching at the University of British Columbia, Neil Bartlett discovered that the gas platinum hexafluoride (PtF) was a powerful oxidizing agent that could oxidize oxygen gas (O) to form dioxygenyl hexafluoroplatinate (). Since O and xenon have almost the same first ionization potential, Bartlett realized that platinum hexafluoride might also be able to oxidize xenon. On March 23, 1962, he mixed the two gases and produced the first known compound of a noble gas, xenon hexafluoroplatinate. Bartlett thought its composition to be Xe[PtF], but later work revealed that it was probably a mixture of various xenon-containing salts. Since then, many other xenon compounds have been discovered, in addition to some compounds of the noble gases argon, krypton, and radon, including argon fluorohydride (HArF), krypton difluoride (KrF), and radon fluoride. By 1971, more than 80 xenon compounds were known.
Argon
"Argon" (Greek , neuter singular form of meaning "lazy" or "inactive"), is named in reference to its chemical inactivity. This chemical property of this first noble gas to be discovered impressed the namers. An unreactive gas was suspected to be a component of air by Henry Cavendish in 1785. Argon was first isolated from air in 1894 by Lord Rayleigh and Sir William Ramsay at University College London by removing oxygen, carbon dioxide, water, and nitrogen from a sample of clean air. They had determined that nitrogen produced from chemical compounds was 0.5% lighter than nitrogen from the atmosphere. The difference was slight, but it was important enough to attract their attention for many months. They concluded that there was another gas in the air mixed in with the nitrogen. Argon was also encountered in 1882 through independent research of H. F. Newall and W. N. Hartley. Each observed new lines in the emission spectrum of air that did not match known elements.
Carbon monoxide
Aristotle (384–322 BC) first recorded that burning coals produced toxic fumes. An ancient method of execution was to shut the criminal in a bathing room with smoldering coals. What was not known was the mechanism of death. Greek physician Galen (129–199 AD) speculated that there was a change in the composition of the air that caused harm when inhaled. In 1776, the French chemist produced CO by heating zinc oxide with coke, but mistakenly concluded that the gaseous product was hydrogen, as it burned with a blue flame. The gas was identified as a compound containing carbon and oxygen by the Scottish chemist William Cruikshank in 1800. Its toxic properties on dogs were thoroughly investigated by Claude Bernard around 1846.
Winkler test for dissolved oxygen
The test was originally developed by Ludwig Wilhelm Winkler, in later literature referred to as Lajos Winkler, while working at Budapest University on his doctoral dissertation in 1888. The amount of dissolved oxygen is a measure of the biological activity of the water masses. Phytoplankton and macroalgae present in the water mass-produce oxygen by way of photosynthesis. Bacteria and eukaryotic organisms (zooplankton,fish) consume this oxygen through cellular respiration. The result of these two mechanisms determines the concentration of dissolved oxygen, which in turn indicates the production of biomass. The difference between the physical concentration of oxygen in the water (or the theoretical concentration if there were no living organisms) and the actual concentration of oxygen is called the biochemical demand in oxygen. The Winkler test is often controversial as it is not 100% accurate and the oxygen levels may fluctuate from test to test despite using the same constant sample.
Nitrogen
The discovery of nitrogen is attributed to the Scottish physician Daniel Rutherford in 1772, who called it "noxious air". Though he did not recognise it as an entirely different chemical substance, he clearly distinguished it from Joseph Black's "fixed air", or carbon dioxide. The fact that there was a component of air that does not support combustion was clear to Rutherford, although he was not aware that it was an element. Nitrogen was also studied at about the same time by Carl Wilhelm Scheele, Henry Cavendish, and Joseph Priestley, who referred to it as "burnt air" or "phlogisticated air". Nitrogen gas was inert enough that Antoine Lavoisier referred to it as "mephitic air" or "azote", from the Greek word (azotikos), "no life". In an atmosphere of pure nitrogen, animals died and flames were extinguished. Though Lavoisier's name was not accepted in English, since it was pointed out that almost all gases (indeed, with the sole exception of oxygen) are mephitic, it is used in many languages (French, Italian, Portuguese, Polish, Russian, Albanian, Turkish, etc.; the German "Stickstoff" similarly refers to the same characteristic, viz. "sticken" "to choke or suffocate") and still remains in English in the common names of many nitrogen compounds, such as hydrazine and compounds of the azide ion. Finally, it led to the name "pnictogens" for the group headed by nitrogen, from the Greek πνίγειν "to choke".
Botany
Palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. Cyanobacteria, the first oxygen-releasing photosynthetic organisms on Earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the chloroplasts in plant cells. The new photosynthetic plants (along with their algal relatives) accelerated the rise in atmospheric oxygen started by the cyanobacteria, changing the ancient oxygen-free, reducing, atmosphere to one in which free oxygen has been abundant for more than 2 billion years.
Robin Hill (biochemist)
Robert Hill FRS (2 April 1899 – 15 March 1991), known as Robin Hill, was a British plant biochemist who, in 1939, demonstrated the 'Hill reaction' of photosynthesis, proving that oxygen is evolved during the light requiring steps of photosynthesis. He also made significant contributions to the development of the Z-scheme of oxygenic photosynthesis.
Blowpipe (tool)
The blowpipes of all of the foregoing blasted air into a flame. The blow pipe was used by the Egyptians at around 200 BCE and to today. Antoine Lavoisier is credited as the first to blow oxygen - of which he was co-discoverer - through a blowpipe to support the combustion of charcoal, in 1782. Others, such as Edward Daniel Clarke, employed hydrogen, and later mixed hydrogen and oxygen in the oxy-hydrogen blowpipe. The vastly increased temperatures, and the volatility of hydrogen-oxygen mixes drove on the development of the so-called gas blowpipe as a tool, and at the same time brought many new materials into reach of the blowpipe as a tool for assay. Robert Hare was a noted exponent of the improved tool. Goldsworthy Gurney, whilst at the Surrey Institute, published in 1823 an account of a new blowpipe so constructed as to enable the operator to produce a flame of great size, power and brilliancy by burning large quantities of the mixed gases with the utmost safety. Gurney went on to employ the principles in his Bude light.
Oxygen
Established in 1667 by the German alchemist J. J. Becher, and modified by the chemist Georg Ernst Stahl by 1731, phlogiston theory stated that all combustible materials were made of two parts. One part, called phlogiston, was given off when the substance containing it was burned, while the dephlogisticated part was thought to be its true form, or calx.
Cambrian explosion
Earth's earliest atmosphere contained no free oxygen (O); the oxygen that animals breathe today, both in the air and dissolved in water, is the product of billions of years of photosynthesis. Cyanobacteria were the first organisms to evolve the ability to photosynthesize, introducing a steady supply of oxygen into the environment. Initially, oxygen levels did not increase substantially in the atmosphere. The oxygen quickly reacted with iron and other minerals in the surrounding rock and ocean water. Once a saturation point was reached for the reactions in rock and water, oxygen was able to exist as a gas in its diatomic form. Oxygen levels in the atmosphere increased substantially afterward. As a general trend, the concentration of oxygen in the atmosphere has risen gradually over about the last 2.5 billion years.
Oxygen (play)
Oxygen is a 2001 play by Roald Hoffman who received the chemistry Nobel prize in 1982, and Carl Djerassi, the Stanford biochemist. The play is a dramatisation of events leading to the discovery of oxygen in the eighteenth century.
Joseph Priestley
Volume I of "Experiments and Observations on Different Kinds of Air" outlined several discoveries: "nitrous air" (nitric oxide, NO); "vapor of spirit of salt", later called "acid air" or "marine acid air" (anhydrous hydrochloric acid, HCl); "alkaline air" (ammonia, NH); "diminished" or "dephlogisticated nitrous air" (nitrous oxide, NO); and, most famously, "dephlogisticated air" (oxygen, O) as well as experimental findings that showed plants revitalised enclosed volumes of air, a discovery that would eventually lead to the discovery of photosynthesis. Priestley also developed a "nitrous air test" to determine the "goodness of air". Using a pneumatic trough, he would mix nitrous air with a test sample, over water or mercury, and measure the decrease in volume—the principle of eudiometry. After a small history of the study of airs, he explained his own experiments in an open and sincere style. As an early biographer writes, "whatever he knows or thinks he tells: doubts, perplexities, blunders are set down with the most refreshing candour." Priestley also described his cheap and easy-to-assemble experimental apparatus; his colleagues therefore believed that they could easily reproduce his experiments. Faced with inconsistent experimental results, Priestley employed phlogiston theory. This, however, led him to conclude that there were only three types of "air": "fixed", "alkaline", and "acid". Priestley dismissed the of his day. Instead, he focused on gases and "changes in their sensible properties", as had natural philosophers before him. He isolated carbon monoxide (CO), but apparently did not realise that it was a separate "air".
Wöhler synthesis
It is argued that organic chemistry did not actually start with this discovery in 1828 but 4 years earlier with the synthesis of oxalic acid in 1824 also by Wöhler and also from the inorganic precursor cyanogen. It is also argued that vitalism was not put to bed either in 1828. His contemporaries Liebig and Pasteur never abandoned vitalism and it took until 1845 when Kolbe repeated an inorganic – organic conversion of carbon disulfide to acetic acid before vitalism started to lose supporters in serious numbers.
Ozone
A half century later, Christian Friedrich Schönbein noticed the same pungent odour and recognized it as the smell often following a bolt of lightning. In 1839, he succeeded in isolating the gaseous chemical and named it "ozone", from the Greek word "" () meaning "to smell". 
For this reason, Schönbein is generally credited with the discovery of ozone. The formula for ozone, O, was not determined until 1865 by Jacques-Louis Soret and confirmed by Schönbein in 1867.
Adrien-Jean-Pierre Thilorier
Thilorier was not the first person to liquefy carbon dioxide: Michael Faraday had liquefied it in 1823. However, with an ample and reliable supply of liquid carbon dioxide, Thilorier was able to observe and measure its properties, such as its vapor density and its extraordinary rate of expansion with temperature, under a wide range of conditions.
Robert Strutt, 4th Baron Rayleigh
In 1916, working with his colleague Alfred Fowler, Strutt was the first to prove the existence of ozone in the atmosphere by examining the ultra-violet spectrum of the setting sun. Strutt proved that the ozone was mainly located in the upper atmosphere, in what is now called the ozone layer.
Oxygen
It is also commonly claimed that oxygen was first discovered by Swedish pharmacist Carl Wilhelm Scheele. He had produced oxygen gas by heating mercuric oxide and various nitrates in 1771–2. Scheele called the gas "fire air" because it was then the only known agent to support combustion. He wrote an account of this discovery in a manuscript titled "Treatise on Air and Fire", which he sent to his publisher in 1775. That document was published in 1777.
Catalase
Catalase was not noticed until 1818 when Louis Jacques Thénard, who discovered HO (hydrogen peroxide), suggested its breakdown is caused by an unknown substance. In 1900, Oscar Loew was the first to give it the name catalase, and found it in many plants and animals. In 1937 catalase from beef liver was crystallised by James B. Sumner and Alexander Dounce and the molecular weight was found in 1938.
Allotropes of oxygen
Tetraoxygen had been suspected to exist since the early 1900s, when it was known as oxozone. It was identified in 2001 by a team led by Fulvio Cacace at the University of Rome. The molecule was thought to be in one of the phases of solid oxygen later identified as . Cacace's team suggested that probably consists of two dumbbell-like molecules loosely held together by induced dipole dispersion forces.
Allotropes of oxygen
Atomic oxygen has been detected at planet Mars by Mariner, Viking, and the SOFIA observatory.
Burning glass
Burning lenses were used both by Joseph Priestley and Antoine Lavoisier in their experiments to obtain oxides contained in closed vessels under high temperatures. These included carbon dioxide by burning diamond, and mercuric oxide by heating mercury. This type of experiment contributed to the discovery of "dephlogisticated air" by Priestley, which became better known as oxygen, following Lavoisier's investigations.
Oxygen toxicity
Central nervous system toxicity was first described by Paul Bert in 1878. He showed that oxygen was toxic to insects, arachnids, myriapods, molluscs, earthworms, fungi, germinating seeds, birds, and other animals. Central nervous system toxicity may be referred to as the "Paul Bert effect".
Thomas Andrews (scientist)
In Andrews' experiments on phase transitions, he showed that carbon dioxide may be carried from any of the states we usually call liquid to any of those we usually call gas, without losing homogeneity. The mathematical physicist Willard Gibbs cited these results in support of the Gibbs free energy equation. They also set off a race among researchers to liquify various other gases. In 1877-78 Louis Paul Cailletet was the first to liquefy oxygen and nitrogen.
Oxygen
Lavoisier renamed 'vital air' to "oxygène" in 1777 from the Greek roots " (oxys)" (acid, literally "sharp", from the taste of acids) and "-γενής (-genēs)" (producer, literally begetter), because he mistakenly believed that oxygen was a constituent of all acids. Chemists (such as Sir Humphry Davy in 1812) eventually determined that Lavoisier was wrong in this regard (hydrogen forms the basis for acid chemistry), but by then the name was too well established.