History of Atmospheric Science Discovery of Oxygen

1. History of Atmospheric Science Discovery of Oxygen

2. Term Schedule Date Topic 1 11/03/2011 Introduction / Organisation 2 11/10/2011 Aristotle’s Meteorology – atmospheric science 350 B.C 3 11/17/2011 The Weight of Air – Galilei, Torricelli, Boyle 4 11/24/2011 Discovery of Oxygen 5 12/08/2011 Atmospheric Dynamics and the Coriolis Effect 6 12/15/2011 The classification of Clouds – Luke Howard’s heritage 7 12/22/2011 Discovery of the Greenhouse Effect 8 01/12/2012 Instrumentation I – Meteorological Instruments 9 01/19/2012 Instrumentation II – Optical and Spectroscopic instruments 10 01/26/2012 Discovery of Ozone, Ozone Crisis and Ozone Hole 1102/02/2012 Discovery of the Magnetosphere 12 02/09/2012 The Gaia-Hypothesis – a critical Review 13 02/16/2012 Summary

3. Summary of last lecture • Aristotle’s view of nature’s abhorrence of the void (accepted until 17th century) • Galilei’s measurement of the weight of air (published 1638) • Torricelli performs his legendary barometric experiment in 1643/1644 • Pascal demonstrates the altitude dependence of air pressure in 1648 • Halley’s empirical pressure-altitude dependence published in 1686 • Laplace derived explicit formula for the altitude dependence of atmospheric pressure (1802)

4. Lecture Outline • Fundamental characteristics of Oxygen • Early experiments • The Phlogiston Theory • Priestley’s discovery of dephlogisticated air • Lavoisier’s oxygen experiments • The role of oxygen for the evolution of the Earth’s atmosphere

5. Fundamental characteristics of Oxygen Atomic Number: 8 Atomic Radius: 66 pm Atomic Symbol: O Melting Point: -218.79 °C Atomic Weight: 15.9994 amu Boiling Point: -182.95 °C Electron Configuration: 1s2 2s2 2p4 • Properties: • The gas is colorless, odorless, and tasteless. The liquid and solid forms are pale blue • Until 1961 the atomic mass of O was used to define the atomic mass unit (1/16th of the mass of an oxygen atom). Since then 12C is used for this purpose (unified atomic mass unit) • O2 constitutes about 21% of the Earth atmosphere • O2 absorbs radiation in the visible and NIR spectral range (e.g., A-band) • Electronic transitions of O atoms produce the red (630 nm) and green (558 nm) colours of the Aurora • O is the most abundant (by mass) element in the Earth’s crust • About two thirds of the human body and nine tenths of water consists of oxygen

6. O21-band (a1g – X3-g) O2 A-band (b1+g – X3-g) O2 absorption/emission in SCIAMACHY spectra

7. Philo‘s candle experiment Early experiments • Philo of Byzantium (about 280 BC to about 220 BC) or „Philo mechanicus“ performed an experiment with a burning candle in an inverted jar put in a vessel owl filled with water • Result: Burning causes the water level in the inverted glass jar to rise • Philo‘s explanation: Air is partly converted to fire (both elements), which is able to escape through the glass • 17th century: Robert Boyle showed that air is required for combustion processes

8. The work of John Mayow (1643 – 1679) • John Mayow (1643-1679), an English chemist and physiologist showed that only part of the air is required for maintaining fire. He called it „spiritus igneo-aereus“ or „nitro-aereus“ (now known as oxygen) • He also suggested that spiritus nitro-aerus is consumed in both combustion and respiration • Furthermore, he observed that an antimon sample became heavier after being heated with a burning glass. Mayow‘s interpretation: Spiritus ignea-aereus is combined with the burned material • In summary, Mayow‘s work was carried out about a century before the generally accepted discovery of oxygen by Príestley, Scheele, and Lavoisier (1770s)

9. The Phlogiston theory • First proposed by Johann Joachim Becher (1635 – 1682): • 1667: Publication of „Physical Education“ containing the first outline of the Phlogiston theory. In addition to the 4 fundamental elements of the Greeks there exists a fifth element which occurs in flammable materials and is released during combustion. • In detail, Johann Becher replaced the greek elements fire and air by three forms of earth: • Terra lapidae, terra fluida and terra pinguis • Ernst Stahl (1659 – 1734) called Terra pinguis „phlogiston“ (1718) • Main statements of the phlogiston theory: • All flammable materials contain phlogiston, which has no color, odor nor taste • Phlogiston is set free by burning • Air is only capable to absorb a certain amount of phlogiston. Once the air is saturated with phlogiston, burning ceases. • Phlogisticated air cannot support life. Importance of air for respiration: removal of phlogiston from the body. • Phlogiston is like „anti-oxygen“ (from our perspective)

10. The Phlogiston theory II • Strengths of the phlogiston theory: Several experimental findings could be explained • Extinction of a flame in a limited air volume • Combustion of organic matter typically leads to reduction of mass of the solid components (neglecting gaseous products) • Explanation: Phlogiston is absorbed by the plants and released during combustion • Weaknesses of the phlogiston theory: • Heating of metals leads to a mass increase, despite the assumed phlogiston release • Solution: Phlogiston has a negative mass

11. Carl Wilhelm Scheele Carl Wilhelm Scheele • Oxygen was first discovered by Carl Wilhelm Scheele (1742 (Stralsund) – 1786 (Köping/Sweden)) in 1772/1773 • Scheele heated Mercurius calcinatus (mercury oxide, HgO) producing a novel gas • Scheele called it „fire air“ and distinguished it from „foul air“ (later identified to be nitrogen) • Scheele realized that air is not an element, but consists of different components • His „Treatise on Air and Fire“ was submitted in 1775, but only published in 1777 • But: Scheele still believed in the Phlogiston theory • Scheele also discovered several other elements and compounds, e.g., Barium, Magnesium, Molybdenum, Tungsten, Chlorine, Fluorine. • (The red form of HgO can be produced by heating Hg in oxygen to about 350 °C; Melting point of HgO: 350 °C)

12. Joseph Priestley (1733 – 1804) • 1733 Born at Birstall near Leeds • Studied theology, philology, history, philosophy and natural sciences • 1755 – 1772 Priest and teacher at different locations • 1772 – 1780 Private teacher and librarian of William Fitzmaurice-Petty, Earl of Shelbourne • 1773 Received the Copley Medal of the Royal Society for discovering/inventing soda-water • 1791 His house was set alight by a mob of people, because he was sympathetic to the French revolution • 1794 Emigration to the United States • 1804 Death in Northumberland, Pennsylvania Joseph Priestley

13. Priestley’s contributions • Joseph Priestley produced oxygen by liberation from mercurius calcinatus (Mercuryoxide, HgO) using sunlight focussed by a burning lens (12 inch diameter, 20 inch focal length) on August 1, 1774. • He called it „dephlogisticated air“ • Results published in 1775 in a paper entitled „An account of further discoveries of air“, i.e., 2 years earlier than Scheele‘s paper appeared

14. Sunlight Mercurius calcinatus Hg Priestley‘s burning lens Priestley’s experiment to produce “dephlogisticated air” • A glass tube filled with Hg is inverted and put into a jar also filled with Hg • A piece of mercurius calcinatus (HgO) was put into the air volume (beforehand of course) • The HgO is heated using a burning lens and sunlight • The produced gas can be extracted through a valve

15. Distinct features of Priestley’s dephlogisticated air • Dephlogisticated air is not absorbed („imbibed“) by water, in contrast to „fixed air“ (CO2) • Candles burn longer and more intense, similar to being exposed to „nitrous air“ (NO, nitric oxide) • Mice, exposed to a limited volume of dephlogisticated air live two to three times longer than in common air: • „On the 8th of this month I procured a mouse, and put it into a glass vessel, containing two ounce measures of air from mercurius calcinatus. Had it been common air, a full- grown mouse, as it was would have lived in it about a quarter of an hour. In this air, however, my mouse lived a full half hour ; and though it was taken out seemingly dead, it appeared to have been only exceedingly chilled ; for, upon being held to the fire, it presently revived, and appeared not to have received any harm from the experiment“. • Joseph Priestley, From Experiments and Observations on Different Kinds of Air, Section III. On dephlogisticated air, and of the constitution of the atmosphere, London 1775. • Nitrous air test (or “test of the goodness of air”; Principle of Eudiometry) (Priestley, page 16 and 18): Dephlogisticated air is mixed with nitrous air (NO) over water and the reduction in volume is measured: • “For after mixing it with nitrous air, in the usual proportion of two to one, it was diminished in the proportion of 4 ½ to 3 ½ ; that is, the nitrous air had made it two ninths less than before […] ; whereas I had never found that, in the longest time, nay common air was reduced more than one fifth of its bulk by any proportion of nitrous air , nor more than one fourth by any phlogistic process whatever”

16. Distinct features of Priestley’s dephlogisticated air • Priestley’s conclusion on the “goodness of dephlogisticated air”: • “I conclude that it was between four and five times as good as common air.” • Reason: • “Now, as common air takes about one half of its bulk of nitrous air, before it begins to receive any addition to its dimensions from more nitrous air, and this air took more than four half-measures before it ceased to be diminished by more nitrous air, and even five half-measures made no addition to its original dimensions, I conclude that it was between four and five times as good as common air.”

17. Our perspective Priestley‘s results Composition Atomic massRatios N2 28 1 NO 29 1.035 78% N2, 21% O2 28.8 1.028 O2 32 1.143 The bladder filled with dwts.*gr.* Ratios Phlogisticated air 7 15 1 Nitrous air 7 16 1.005 Common air 7 17 1.011 Dephlogisticated air 7 19 1.021 Priestley’s measurements of the weight of air • Measurement of the weight of air using Cavendish‘s bladder method * dwts. = pennyweights = 24 grains = 1.5552 g * 1 gr. = 1 grain ≈ 65 mg (originally the weight of a single barleycorn) • Priestley‘s conclusions: • Both nitrous air, and air diminished by phlogistic processes are rather lighter than common air • Dephlogisticated air appears to be a little heavier than common air

18. Miscellanous commenty by Joseph Priestley I „For my own part, I will frankly acknowledge, that, at the commencement of the experiments recited in this section, I was so far from having formed any hypothesis that led to the discoveries I made in pursuing them, that they would have appeared very improbable to me had I been told of them ; and when the decisive facts did at length obtrude my notice, it was very slowly, and with great hesitation, that I yielded to the evidence of my senses. And yet, when I re-consider the matter, and compare my last discoveries relating to the constitution of the atmosphere with the first, I see the closest and the easiest connexion in the world between them, so as to wonder that I should not have been led immediately from the one to the other. That this was not the case, I attribute to the force of prejudice, which, unknown to ourselves, biasses not only our judgements, properly so called, but even the perception of our senses: for we may take a maxim so stongly for granted, that the plainest evidence of sense will not intirely change, and often hardly modify our persuasions ; and the more ingenious a man is, the more effectually he is entangled in his errors ; his ingenuity only helping him to deceive himself, by evading the force of truth.“ Joseph Priestley, From Experiments and Observations on Different Kinds of Air, Section III. On dephlogisticated air, and of the constitution of the atmosphere, London 1775.

19. Miscellanous commenty by Joseph Priestley II „My reader will not wonder, that, after having ascertained the superior goodness of dephlogisticated air by mice living in it, and the other tests above mentioned, I should have the curiosity to taste it myself. I have gratified that curiosity, by breathing it, drawing it through a glass syphon, and, by this means, I reduced a large jar full of it to the standard of common air. The feeling of it to my lungs was not sensibly different from that of common air ; but I fancied that my breast was particuliarly light and easy for some time afterwards. Who can tall but that, in time, this pure air may become a fashionable article in luxury. Hitherto only two mice and myself have had the privilege of breathing it.“ Joseph Priestley, From Experiments and Observations on Different Kinds of Air, Section V. Miscellaneous Observations on the Properties of dephlogisticated Air, London 1775.

20. Antoine Lavoisier Antoine Lavoisier (1743 – 1794) • 1743 Born at Paris • 1754 – 1761 Studied chemistry, botany, astronomy and mathematics • 1763 Bachelor of Law • 1779 Introduction of the term „oxygen“ • 1794 Execution in Paris • Lavoisier‘s main achievement in the discovery of oxygen was to disprove the Phlogiston theory • Priestley and Scheele were still supporters of the phlogiston theory and interpreted their experiments within the paradigm of the phlogiston theory

21. Sunlight Sealed jar weights Pb Lavoisier‘s lead experiment • Lavoisier‘s findings: • Heating the lead sample made it heavier • the overall weight of the sealed glass-jar remained constant •  The additional weight must have come from the gas inside the jar • Furthermore: Breaking the seal caused air streaming into the jar • Weighting the complete setup again, showed that the mass of the lost air equals the mass gained by the lead sample • Issue: Lavoisier didn’t know how to release the gas again from the lead

22. Lavoisier‘s famous experiment • Heating of mercury (Hg) and air in a jar (A) for 12 days, leading to the formation of red mercury calx or mercurius calcinatus (HgO) • Volume of air decreased from 50 to 41 in3 • The remaining air was called azote (Greek: a and zoe = without life; now N2). • Then the mercurius calcinatus was heated again and produced 9 in3 of dephlogisticated air • Mixing the produced dephlogisticated air with the azote obtained earlier yielded a gas that was not distinguishable from common air •  Heat caused something to be combined with mercury to form the mercury calx, rather than phlogiston being released from the mercury •  Falsification of the Phlogiston theory, Coining of the term ‘oxy-gen’ (made from acid)

23. Oxygen content of air • Priestley discovered in 1772 that metals only absorb about 1/5 of the air during the calcination (combustion) process • Lavoisier determined the oxygen content of air as about 1/4 in 1780

24. A (very) short history of Earth‘s climate • Formation of Earth about 5 billion years ago • Primary atmosphere consisted presumably mainly of H2 and He • Loss of primary atmosphere possibly through meteor impact and solar wind, leaving a surface of bare rock • Surface temperatures determined by equilibrium between solar insulation and thermal emission (Stefan-Boltzmann-Law) • Comparison of Venus, Earth and Mars: Venus has highest temperature, because of closest proximity to Sun, Mars had the lowest surface temperature • Modern atmosphere is a secundary atmosphere – created by outgassing of H2O, CO2 und sulphur compounds (e.g. by volcanic eruptions) • Outgassing of H2O und CO2 leads to greenhouse effect Warming

25. A (very) short history of Earth‘s climate II • On Venus: temperature was always above the H2O condensation point • H2O stays in the atmosphere and heats it up • H escaped into space and CO2 stayed in the Venus atmosphere. Surface temperature of Venus is abous 700 K („Runaway greenhouse effect“) • On Mars: T probably mainly below the freezing point of H2O Weak greenhouse effect • On Earth: Outgassed H2O formed oceans and T stayed close to triple point • About 3.5 billion years ago terrestrial life evolved and photosynthesis by algae began •  O2 accumulation in the atmosphere • Formation of O3 by photolysis of O2 • UV shield enables life on land • On Earth no runaway greenhouse effect probably due to larger distance to sun • 5 billion years ago the solar constant was about 30 % smaller

26. Evolution of CO2 and O2 in the Earth‘s atmosphere

27. O3 O2 Evolution of O2 and O3 O2 und O3 abundances relative to present Time before present in million years Graedel & Crutzen [1994]

28. Comparison of the atmospheres of Earth, Venus and Mars

29. Venus and the „Runaway“ Greenhouse effect Venus Erde Mars

30. Conclusions • Early discoveries by John Mayow in the 1670s preceding the works by Scheele, Priestley and Lavoisier by a century • The Phlogiston Theory • Priestley’s discovery of dephlogisticated air • Falsification of the Phlogiston theory by Lavoisier • The role of oxygen for the evolution of the Earth’s atmosphere • Industrial production of oxygen

31. Used resources • Priestley, Joseph, The discovery of Oxygen: Experiments by Joseph Priestley, Kessinger Publishing, 1775 (1912). • Boyle, Robert, Original papers available online http://www.bbk.ac.uk/boyle/ • Encyclopedia Brittanica articles on Priestley, Becher, Levoisier, Scheele, Mayow, Stahl • www.wikipedia.org • Walker, Gabrielle, An ocean of air: Why the Wind Blows and Other Mysteries of the Atmosphere, Bloomsbury, 2007