Das 1871 von Dmitri Mendeleev konstruierte Periodensystem. Das Periodensystem ist eine der kraftvollsten Ikonen der Wissenschaft, die im Zentrum der Chemie steht und die grundlegendsten Prinzipien des Feldes verkörpert.
Die Geschichte der Chemie repräsentiert eine Zeitspanne von der antiken Geschichte bis zum Jahr das Geschenk. Um 1000 v. Chr. Verwendeten Zivilisationen Technologien, die schließlich die Grundlage der verschiedenen Zweige der Chemie bildeten. Beispiele sind die Gewinnung von Metallen aus Erzen, die Herstellung von Tonwaren und Glasuren, die Vergärung von Bier und Wein, die Gewinnung von Chemikalien aus Pflanzen für Medizin und Parfüm, die Umwandlung von Fett in Seife, die Herstellung von Glas, und Legierungen wie Bronze herstellen.
Die Chemie der Chemie, die Alchemie, konnte die Natur der Materie und ihre Umwandlungen nicht erklären. Indem Alchemisten Experimente durchführten und die Ergebnisse aufzeichneten, wurden die Voraussetzungen für die moderne Chemie geschaffen. Die Unterscheidung begann sich zu entwickeln als Robert Boyle in seiner Arbeit The Skeptical Chymist (1661) eine klare Unterscheidung zwischen Chemie und Alchemie machte. Während sich sowohl die Alchemie als auch die Chemie mit der Materie und ihren Umwandlungen befassen, wird davon ausgegangen, dass Chemiker auf ihre Arbeit wissenschaftliche Methoden anwenden.
Mit der Arbeit von Antoine Lavoisier, der ein Massenerhaltungsgesetz entwickelte, das eine sorgfältige Messung und quantitative Beobachtung chemischer Phänomene erforderte, gilt die Chemie als etablierte Wissenschaft. Die Geschichte der Chemie ist eng mit der Geschichte der Thermodynamik verknüpft, insbesondere durch die Arbeit von Willard Gibbs. [1]
Alte Geschichte [ edit
Frühe Menschen []
In der Blombos-Höhle in Südafrika wurde eine 100.000 Jahre alte Ocker-verarbeitende Werkstatt gefunden. Es zeigt, dass der frühe Mensch über grundlegende Kenntnisse der Chemie verfügte. Gemälde von frühen Menschen, die aus frühen Menschen bestehen und Tierblut mit anderen Flüssigkeiten an Höhlenwänden mischen, weisen ebenfalls auf geringe Kenntnisse der Chemie hin. [2][3]
Frühe Metallurgie [ edit
Die frühesten Aufnahmen Metall, das vom Menschen eingesetzt wird, scheint Gold zu sein, das frei oder "einheimisch" gefunden werden kann. Kleine Mengen an natürlichem Gold wurden in spanischen Höhlen gefunden, die während der Altsteinzeit genutzt wurden, etwa 40.000 v.Chr. [4]
Silber, Kupfer, Zinn und Meteoriteisen können ebenfalls heimisch gefunden werden Metallbearbeitung in alten Kulturen war begrenzt. [5] Ägyptische Waffen aus Meteoreisen wurden um 3000 v. Chr. als "Dolche vom Himmel" hoch geschätzt. [6]
Wahrscheinlich die erste chemische Reaktion, die in verwendet wurde Eine kontrollierte Art war Feuer. Jahrtausende lang wurde Feuer jedoch einfach als mystische Kraft angesehen, die eine Substanz in eine andere verwandeln konnte (brennendes Holz oder kochendes Wasser), während sie Wärme und Licht produzierte. Feuer beeinflusste viele Aspekte früher Gesellschaften. Diese reichten von den einfachsten Facetten des Alltags, wie Kochen und Erwärmen und Beleuchten von Lebensräumen, bis zu fortgeschritteneren Anwendungen, wie zum Beispiel zur Herstellung von Keramik und Ziegeln sowie zum Schmelzen von Metallen, um Werkzeuge herzustellen.
Es war Feuer, das zur Entdeckung von Glas und zur Reinigung von Metallen führte; es folgte der Aufstieg der Metallurgie. [7] In den frühen Stadien der Metallurgie wurde nach Methoden zur Reinigung von Metallen gesucht, und Gold, das im alten Ägypten bereits um 2900 v. Chr. bekannt war, wurde zu einem Edelmetall.
Bronzezeit [ edit ]
Bestimmte Metalle können durch Erhitzen der Felsen in einem Feuer aus ihren Erzen gewonnen werden: Zinn, Blei und (bei höherer Temperatur) Kupfer. Dieser Prozess wird als Schmelzen bezeichnet. Die ersten Beweise für diese extraktive Metallurgie stammen aus dem 6. und 5. Jahrtausend v. Chr. Und wurden in den archäologischen Stätten Majdanpek, Yarmovac und Plocnik, alle drei in Serbien, gefunden. Die früheste Kupferschmelzung ist am Standort Belovode zu finden. [8] Zu diesen Beispielen gehört eine Kupferaxt aus der Zeit von 5500 v. Chr., Die zur Vinča-Kultur gehört. [9] Andere Hinweise auf frühe Metalle finden sich an Orten wie dem 3. Jahrtausend v Palmela (Portugal), Los Millares (Spanien) und Stonehenge (Vereinigtes Königreich). Wie so oft bei der Erforschung der prähistorischen Zeit, können die endgültigen Anfänge nicht eindeutig definiert werden und neue Entdeckungen sind im Gange.
Bergbauregionen des alten Nahen Ostens. Schachtelfarben: Arsen ist in Braun, Kupfer in Rot, Zinn in Grau, Eisen in Rotbraun, Gold in Gelb, Silber in Weiß und Blei in Schwarz. Der gelbe Bereich steht für Arsenbronze, der graue Bereich für Zinnbronze.
Diese ersten Metalle waren Einzelelemente oder Kombinationen, wie sie in der Natur vorkamen. Durch die Kombination von Kupfer und Zinn könnte ein überlegenes Metall hergestellt werden, eine Legierung, die Bronze genannt wird. Dies war ein großer technologischer Wandel, der um 3500 v. Chr. In der Bronzezeit begann. Die Bronzezeit war eine Zeit der menschlichen kulturellen Entwicklung, in der die fortschrittlichste Metallverarbeitung (zumindest in systematischer und weit verbreiteter Anwendung) Techniken zum Schmelzen von Kupfer und Zinn aus natürlich vorkommenden Aufschlüssen von Kupfererzen und das anschließende Schmelzen dieser Erze zum Bronzegießen umfasste. Diese natürlich vorkommenden Erze enthielten typischerweise Arsen als häufige Verunreinigung. Kupfer / Zinn-Erze sind selten, was sich in der Abwesenheit von Zinnbronzen in Westasien vor 3000 v.
Nach der Bronzezeit wurde die Geschichte der Metallurgie von Armeen geprägt, die bessere Waffen suchten. Die Länder in Eurasien blühten, als sie die überlegenen Legierungen bauten, die wiederum bessere Rüstungen und bessere Waffen boten. [ Zitat erforderlich ] Im alten Indien wurden bedeutende Fortschritte in der Metallurgie und Alchemie gemacht [10]
Eisenzeit [ edit ]
Die Gewinnung von Eisen aus seinem Erz zu einem verarbeitbaren Metall ist viel schwieriger als Kupfer oder Zinn. Eisen ist zwar für Werkzeuge nicht besser geeignet als Bronze (bis Stahl entdeckt wurde), Eisenerz ist jedoch viel häufiger und häufiger als Kupfer oder Zinn und daher häufiger vor Ort verfügbar, ohne dafür dafür handeln zu müssen.
Die Eisenverarbeitung scheint um 1200 v. Chr. Von den Hethitern erfunden worden zu sein, beginnend mit der Eisenzeit. Das Geheimnis der Gewinnung und Bearbeitung von Eisen war ein Schlüsselfaktor für den Erfolg der Philister: 19459040 [6] [11]
Die Eisenzeit bezieht sich auf das Aufkommen der Eisenbearbeitung ( Eisenmetallurgie). Historische Entwicklungen in der Eisenmetallurgie finden sich in einer Vielzahl von Kulturen und Zivilisationen der Vergangenheit. Dazu gehören die alten und mittelalterlichen Königreiche und Reiche des Nahen Ostens und des Nahen Ostens, des alten Iran, des alten Ägyptens, des alten Nubiens und Anatoliens (der Türkei), des antiken Nok, Karthagos, der Griechen und Römer des alten Europas, des mittelalterlichen Europas, des alten und des antiken Europas unter anderem das mittelalterliche China, das alte und das mittelalterliche Indien, das alte und das mittelalterliche Japan. Viele Anwendungen, Praktiken und Vorrichtungen, die mit der Metallurgie in Zusammenhang stehen oder an der Metallurgie beteiligt sind, wurden im alten China etabliert, wie die Innovation des Hochofens, Gusseisen, hydraulisch angetriebene Schlaghämmer und doppeltwirkende Kolbenbälge. [12][13]
Klassische Antike und atomism [ edit ]
Democritus, griechischer Philosoph der atomistischen Schule.
Philosophische Versuche zu rationalisieren, warum verschiedene Substanzen unterschiedliche Eigenschaften (Farbe, Dichte, Geruch) haben ( gasförmig, flüssig und fest) und reagieren auf andere Weise, wenn sie Umgebungsbedingungen ausgesetzt sind, beispielsweise Wasser oder Feuer oder Temperaturschwankungen. Die antiken Philosophen postulierten die ersten Theorien über Natur und Chemie. Die Geschichte solcher philosophischer Theorien, die sich auf die Chemie beziehen, lässt sich wahrscheinlich auf jede einzelne alte Zivilisation zurückführen. Der gemeinsame Aspekt in all diesen Theorien war der Versuch, eine kleine Anzahl von primären klassischen Elementen zu identifizieren, aus denen sich die verschiedenen Substanzen der Natur zusammensetzen. Substanzen wie Luft, Wasser und Boden / Erde, Energieformen wie Feuer und Licht und abstraktere Begriffe wie Gedanken, Äther und Himmel waren in der Antike üblich, auch wenn es keine gegenseitige Befruchtung gab, zum Beispiel Die alten griechischen, indischen, maya- und chinesischen Philosophien betrachteten Luft, Wasser, Erde und Feuer als primäre Elemente. [ Zitat benötigt ]
Ancient world [ bearbeiten ]
Um 420 v. Chr. Erklärte Empedocles, dass sich die Materie aus vier Grundsubstanzen zusammensetzt: Erde, Feuer, Luft und Wasser. Die frühe Theorie des Atomismus lässt sich auf das antike Griechenland und das alte Indien zurückführen. [14] Der griechische Atomismus geht auf den griechischen Philosophen Democritus zurück, der erklärt, dass Materie um 380 v. Chr. Aus unteilbaren und unzerstörbaren Teilchen besteht, die als "Atomos" bezeichnet werden. Leukippus erklärte auch, Atome seien der unteilbarste Teil der Materie. Dies fiel zeitlich mit einer ähnlichen Erklärung des indischen Philosophen Kanada in seinen Vaisheshika-Sutras zusammen. [14] In ähnlicher Weise diskutierte er die Existenz von Gasen. Was Kanada vom Sutra erklärte, der Demokrit vom philosophischen Nachdenken. Beide litten an einem Mangel an empirischen Daten. Ohne wissenschaftliche Beweise war die Existenz von Atomen leicht zu leugnen. Aristoteles widersetzte sich 330 v. Chr. Der Existenz von Atomen. Im Jahr 380 v. Chr. Behauptete ein griechischer Text, der Polybus zugeschrieben wurde, dass der menschliche Körper aus vier Wunden besteht. Um 300 v. Chr. Postulierte Epicurus ein Universum aus unzerstörbaren Atomen, in dem der Mensch selbst für ein ausgeglichenes Leben verantwortlich ist.
Um dem römischen Publikum die epikureische Philosophie zu erklären, schrieb der römische Dichter und Philosoph Lucretius [15] De rerum natura (Die Natur der Dinge) [16] im Jahre 50 v. In der Arbeit präsentiert Lucretius die Prinzipien des Atomismus; die Natur des Geistes und der Seele; Erklärungen zu Empfindung und Denken; die Entwicklung der Welt und ihrer Phänomene; und erklärt eine Vielzahl von himmlischen und terrestrischen Phänomenen.
Ein Großteil der frühen Entwicklung von Reinigungsmethoden wird von Pliny the Elder in seiner Naturalis Historia beschrieben. Er versuchte, diese Methoden zu erklären und den Zustand vieler Mineralien genau zu beobachten.
Mittelalterliche Alchemie [ edit ]
Siehe auch: Minima naturalia, ein dem Atomismus analoges mittelalterliches aristotelisches Konzept
Das alchemistische Emblem aus dem 17. Jahrhundert zeigt die vier klassischen Elemente in den Ecken von das Bild neben dem Tria Prima auf dem zentralen Dreieck.
Das in der mittelalterlichen Alchemie verwendete Elementarsystem wurde hauptsächlich vom persisch-arabischen Alchemisten Jābir ibn Hayyān entwickelt und war in den klassischen Elementen der griechischen Tradition verwurzelt. [17] Sein System bestand aus den vier aristotelischen Elementen Luft, Erde, Feuer und Wasser sowie zwei philosophischen Elementen: Schwefel, der das Prinzip der Brennbarkeit charakterisiert, "der Stein, der brennt"; und Quecksilber, das das Prinzip der metallischen Eigenschaften charakterisiert. Sie wurden von frühen Alchimisten als idealisierte Ausdrücke irreduzibler Bestandteile des Universums gesehen [18] und werden von größter Bedeutung zur Klarstellung innerhalb der philosophischen Alchemie.
Die drei metallischen Prinzipien (Schwefel gegen Entzündbarkeit oder Verbrennung, Quecksilber gegen Flüchtigkeit und Stabilität und Salz bis zur Festigkeit) wurden tria prima des Schweizer Alchemisten Paracelsus. Er argumentierte, dass Aristoteles Vier-Elemente-Theorie in Körpern als drei Prinzipien auftauchte. Paracelsus betrachtete diese Prinzipien als grundlegend und begründete sie mit der Beschreibung, wie Holz im Feuer brennt. Quecksilber schloss das kohäsive Prinzip ein, so dass das Holz beim Verlassen des Holzes (in Rauch) auseinanderbrach. Rauch beschreibt die Flüchtigkeit (das Quecksilberprinzip), die Hitze erzeugenden Flammen die Entflammbarkeit (Schwefel) und die verbleibende Asche als Solidität (Salz). [19]
Der Stein der Weisen [ edit ] 19659060] "The Alchemist", von Sir William Douglas, 1855
Alchemie definiert sich durch die hermetische Suche nach dem Stein der Weisen, dessen Studie von symbolischer Mystik durchdrungen ist und sich stark von der modernen Wissenschaft unterscheidet. Alchimisten bemühten sich, Transformationen auf esoterischer (spiritueller) und / oder exoterischer (praktischer) Ebene durchzuführen. [20] Es waren die protowissenschaftlichen, exoterischen Aspekte der Alchemie, die im griechisch-römischen Ägypten, im islamischen Goldenen, maßgeblich zur Entwicklung der Chemie beigetragen haben Alter und dann in Europa. Alchemie und Chemie haben ein gemeinsames Interesse an der Zusammensetzung und den Eigenschaften der Materie, und bis zum 18. Jahrhundert waren sie keine getrennten Disziplinen. Der Begriff Chymistry wurde verwendet, um die Mischung aus Alchemie und Chemie zu beschreiben, die vor dieser Zeit existierte. [21]
Die ältesten westlichen Alchemisten, die in den ersten Jahrhunderten lebten die gemeinsame Ära erfand chemischen Apparat. Das Wasserbad oder Wasserbad ist nach Maria, der Jüdin, benannt. Ihre Arbeit gibt auch die ersten Beschreibungen der tribikos und Kerotakis . [22] Cleopatra der Alchemist beschrieb Öfen und wurde mit der Erfindung des Alembikers [23] später gutgeschrieben Der von Jabir ibn Hayyan entwickelte experimentelle Rahmen beeinflusste die Alchemisten, als die Disziplin durch die islamische Welt und im 12. Jahrhundert nach Europa zog.
Während der Renaissance blieb die exoterische Alchemie in Form der paracelsianischen Chemiechemie populär, während die spirituelle Alchemie blühte und sich auf ihre platonischen, hermetischen und gnostischen Wurzeln ausrichtete. Folglich wurde die symbolische Suche nach dem Stein der Weisen nicht durch wissenschaftliche Fortschritte abgelöst und war bis in das frühe 18. Jahrhundert noch immer ein Bereich angesehener Wissenschaftler und Ärzte. Zu den frühneuzeitlichen Alchemisten, die für ihre wissenschaftlichen Beiträge bekannt sind, gehören Jan Baptist van Helmont, Robert Boyle und Isaac Newton.
Probleme mit der Alchemie [ edit ]
Es gab mehrere Probleme mit der Alchemie, vom heutigen Standpunkt aus gesehen. Es gab kein systematisches Benennungsschema für neue Verbindungen, und die Sprache war esoterisch und vage bis zu dem Punkt, dass die Terminologien verschiedene Dinge für verschiedene Menschen bedeuteten. Tatsächlich laut Die Geschichte von Fontana (Brock, 1992):
Die Sprache der Alchemie entwickelte bald ein arkanes und geheimnisvolles technisches Vokabular, das dazu dient, Informationen vor Uneingeweihten zu verbergen. Diese Sprache ist für uns heute weitgehend unverständlich, obwohl es offensichtlich ist, dass die Leser von Geoffery Chaucers Canone Yeoman's Tale oder das Publikum von Ben Jonsons The Alchemist es so gut verstehen konnten, dass sie darüber lachten. [24]
Chaucers Geschichte enthüllte die betrügerische Seite der Alchemie, insbesondere die Herstellung von gefälschtem Gold aus billigen Substanzen. Vor weniger als einem Jahrhundert zeigte Dante Alighieri auch ein Bewusstsein für diesen Betrug und veranlaßte ihn, alle Alchemisten in seinen Schriften dem Inferno zu überlassen. Bald darauf, im Jahre 1317, befahl der Avignon-Papst Johannes XXII. Allen Alchemisten, Frankreich zu verlassen, um gefälschtes Geld zu verdienen. In England wurde 1403 ein Gesetz verabschiedet, das die "Vermehrung von Metallen" mit dem Tod unter Strafe stellte. Trotz dieser und anderer scheinbar extremer Maßnahmen starb die Alchemie nicht. Noch suchten Könige und privilegierte Klassen, den Stein der Weisen und das Lebenselixier für sich selbst zu entdecken. [25]
Es gab auch keine vereinbarte wissenschaftliche Methode, um Experimente reproduzierbar zu machen. Tatsächlich enthalten viele Alchemisten in ihren Methoden irrelevante Informationen wie den Zeitpunkt der Gezeiten oder die Mondphasen. Das esoterische Wesen und das kodifizierte Vokabular der Alchemie waren anscheinend sinnvoller, um die Tatsache zu verbergen, dass sie sich überhaupt nicht sicher sein konnten. Bereits im 14. Jahrhundert schienen Risse in der Fassade der Alchemie zu wachsen; und die Menschen wurden skeptisch. Zitat erforderlich ] Es musste eindeutig eine wissenschaftliche Methode geben, bei der Experimente von anderen Personen wiederholt werden konnten und die Ergebnisse in einer klaren Sprache berichtet werden mussten das legte sowohl bekanntes als auch unbekanntes dar.
Alchemie in der islamischen Welt [ edit ]
In der islamischen Welt übersetzten die Muslime die Werke der alten Griechen und Ägypter ins Arabische und experimentierten mit wissenschaftlichen Ideen. 19659078] Die Entwicklung der modernen wissenschaftlichen Methode war langsam und mühsam, aber eine frühe wissenschaftliche Methode für die Chemie begann unter den frühen muslimischen Chemikern, beginnend mit dem Chemiker Jābir ibn Hayyān aus dem 9. Jahrhundert (in Europa als "Geber" bekannt) manchmal als "Vater der Chemie" angesehen. [27][28][29][30] Im Gegensatz zu den alten griechischen und ägyptischen Alchemisten, deren Werke weitgehend allegorisch und oft unverständlich waren, führte er einen systematischen und experimentellen Ansatz für die wissenschaftliche Forschung ein. [31] erfand und benannte den Alembic (al-anbiq), analysierte chemisch viele chemische Substanzen, stellte Lapidare zusammen, unterschied zwischen Alkalien und Säuren und stellte Hunderte von Medikamenten her. [32] Er auch verfeinerte die Theorie von fünf klassischen Elementen in die Theorie von sieben alchemistischen Elementen, nachdem Quecksilber und Schwefel als chemische Elemente identifiziert worden waren. [33] [ Verifizierung erforderlich
Unter anderen einflussreichen muslimischen Chemikern war Abū al -Rayhān al-Bīrūnī, [34] Avicenna [35] und Al-Kindi widerlegten die Theorien der Alchemie, insbesondere die Theorie der Transmutation von Metallen; und al-Tusi beschrieb eine Version der Massenerhaltung und stellte fest, dass ein Körper aus Materie sich ändern kann, aber nicht verschwinden kann. [36] Rhazes widerrief Aristoteles 'Theorie der vier klassischen Elemente zum ersten Mal und gründete die Firma Grundlagen der modernen Chemie, das Labor im modernen Sinn verwenden, mehr als zwanzig Instrumente entwerfen und beschreiben, von denen viele heute noch verwendet werden, z. B. ein Tiegel, ein Kürbis oder eine Retorte für die Destillation und der Kopf eines Destillierkolbens Abgaberohr (ambiq, lateinische Alembik) und verschiedene Arten von Ofen oder Ofen. Zitat benötigt ]
Für Praktizierende in Europa wurde die Alchemie nach der frühen arabischen Alchemie eine intellektuelle Beschäftigung wurde durch lateinische Übersetzung verfügbar, und im Laufe der Zeit verbesserten sie sich. So lehnte Paracelsus (1493–1541) die 4-Elemente-Theorie ab und bildete mit nur einem vagen Verständnis für seine Chemikalien und Medikamente eine Mischung aus Alchemie und Wissenschaft in der sogenannten Iatrochemie. Paracelsus konnte seine Experimente nicht wirklich wissenschaftlich machen. Als Erweiterung seiner Theorie, dass neue Verbindungen durch die Kombination von Quecksilber mit Schwefel hergestellt werden könnten, hat er beispielsweise das gemacht, was er für "Öl des Schwefels" hielt. Dies war eigentlich Dimethylether, der weder Quecksilber noch Schwefel hatte. Zitat erforderlich ]
17. und 18. Jahrhundert: Frühe Chemie [
] Agricola, Autor von De re metallica
Praktische Versuche, die Raffination von Erzen und deren Gewinnung zum Schmelzen von Metallen zu verbessern, waren eine wichtige Informationsquelle für frühe Chemiker im 16. Jahrhundert, darunter Georg Agricola (1494–1555) ), der 1556 sein großes Werk De re metallica veröffentlichte. Seine Arbeiten beschreiben die hoch entwickelten und komplexen Prozesse des Abbaus von Metallerzen, der Metallgewinnung und der Metallurgie der Zeit. Sein Ansatz entfernte die mit dem Thema verbundene Mystik und schuf die praktische Basis, auf der andere aufbauen konnten. Die Arbeit beschreibt die vielen Ofenarten, die zum Schmelzen des Erzes verwendet wurden, und weckte das Interesse an Mineralien und ihrer Zusammensetzung. Es ist kein Zufall, dass er zahlreiche Verweise auf den früheren Autor Pliny the Elder und seine Naturalis Historia enthält. Agricola wurde als "Vater der Metallurgie" bezeichnet. 19459097 [37]
. Sir Francis Bacon veröffentlichte 1605 The Proficience and Advancement of Learning das eine Beschreibung dessen enthält wurde später als wissenschaftliche Methode bekannt. [38] Im Jahr 1605 veröffentlicht Michal Sedziwój die alchemistische Abhandlung Ein neues Licht der Alchemie in der die Existenz der "Nahrung des Lebens" in der Luft vorgeschlagen wurde, die später als anerkannt wurde Sauerstoff. 1615 veröffentlichte Jean Beguin das frühe Chemiebuch Tyrocinium Chymicum (19459012), in dem die erste chemische Gleichung aller Zeiten dargestellt wird. [39] 1637 veröffentlicht René Descartes Discours de la méthode . die einen Überblick über die wissenschaftliche Methode enthält.
Der niederländische Chemiker Jan Baptist van Helmont Ortus medicinae wurde 1648 posthum veröffentlicht; Das Buch wird von einigen als eine bedeutende Übergangsarbeit zwischen Alchemie und Chemie und als wichtiger Einfluss auf Robert Boyle zitiert. Das Buch enthält die Ergebnisse zahlreicher Experimente und legt eine frühe Version des Massenerhaltungsgesetzes fest. Jan Baptist van Helmont arbeitete in der Zeit unmittelbar nach Paracelsus und der Iatrochemie und schlug vor, es gäbe neben Luft noch unwesentliche Substanzen und prägte für sie einen Namen - "Gas", aus dem griechischen Wort chaos . Van Helmont führte nicht nur das Wort "Gas" in das Vokabular der Wissenschaftler ein, sondern führte auch mehrere Experimente mit Gasen durch. Jan Baptist van Helmont ist heute vor allem für seine Ideen zur spontanen Erzeugung und für sein fünfjähriges Baumexperiment sowie für den Begründer der pneumatischen Chemie bekannt.
Robert Boyle [ edit ]
Robert Boyle, einer der Mitbegründer der modernen Chemie durch seine Verwendung von Experimenten, die die Chemie weiter von der Alchemie trennten.
Anglo- Der irische Chemiker Robert Boyle (1627–1691) hat die moderne wissenschaftliche Methode für die Alchemie verfeinert und die Chemie weiter von der Alchemie getrennt. [40] Obwohl seine Forschung eindeutig in der alchemistischen Tradition wurzelt, wird Boyle heute als weitgehend angesehen der erste moderne Chemiker und damit einer der Begründer der modernen Chemie und einer der Pioniere der modernen experimentellen wissenschaftlichen Methode. Obwohl Boyle nicht der ursprüngliche Entdecker war, ist er am besten für das Boyle'sche Gesetz bekannt, das er 1662 vorstellte: [41] Das Gesetz beschreibt die umgekehrt proportionale Beziehung zwischen dem absoluten Druck und dem Volumen eines Gases, wenn die Temperatur innerhalb eines Gases konstant gehalten wird geschlossenes System [42] [43]
Boyle wird auch für seine Meilenstein-Publikation The Skeptical Chymist im Jahre 1661, die als Eckstein gilt, zugeschrieben Buch auf dem Gebiet der Chemie. In der Arbeit stellt Boyle seine Hypothese vor, dass jedes Phänomen das Ergebnis von Kollisionen von Partikeln in Bewegung war. Boyle appellierte an Chemiker, zu experimentieren, und behauptete, dass Experimente die Beschränkung chemischer Elemente auf die klassischen Vier, nämlich Erde, Feuer, Luft und Wasser, bestreiten. Er plädierte auch dafür, dass die Chemie nicht länger der Medizin oder der Alchemie unterworfen werden sollte und zum Status einer Wissenschaft aufsteigen sollte. Wichtig ist, dass er sich für einen rigorosen Ansatz für wissenschaftliches Experiment einsetzte: Er glaubte, dass alle Theorien experimentell bewiesen werden müssen, bevor sie als wahr betrachtet werden. Die Arbeit enthält einige der frühesten modernen Ideen von Atomen, Molekülen und chemischen Reaktionen und markiert den Beginn der Geschichte der modernen Chemie.
Boyle versuchte auch, Chemikalien zu reinigen, um reproduzierbare Reaktionen zu erhalten. Er war ein vokaler Befürworter der von René Descartes vorgeschlagenen mechanischen Philosophie, um die physikalischen Eigenschaften und Wechselwirkungen materieller Substanzen zu erklären und zu quantifizieren. Boyle war ein Atomist, bevorzugte jedoch den Begriff Korpuskel gegenüber Atomen . Er kommentierte, dass die feinste Verteilung der Materie, in der die Eigenschaften erhalten bleiben, auf der Ebene der Körperchen liegt. Er führte auch zahlreiche Untersuchungen mit einer Luftpumpe durch und stellte fest, dass das Quecksilber beim Abpumpen von Luft fiel. Er beobachtete auch, dass das Pumpen der Luft aus einem Behälter eine Flamme löschen und kleine Tiere töten würde. Boyle half mit seiner mechanischen Korpuskularphilosophie, die Grundlagen für die chemische Revolution zu schaffen. [44] Boyle wiederholte das Baumexperiment von van Helmont und war der erste, der Indikatoren verwendete, die mit Säure den Farbton veränderten.
Entwicklung und Demontage von Phlogiston edit
Joseph Priestley, Mitentdecker des Elements Sauerstoff, das er als "entpuppte Luft" bezeichnete
Stahl prägte den Namen "Phlogiston" für die Substanz, die im Verbrennungsprozess freigesetzt wird. Um 1735 analysierte der schwedische Chemiker Georg Brandt ein in Kupfererz gefundenes dunkelblaues Pigment. Brandt zeigte, dass das Pigment ein neues Element enthielt, das später Kobalt genannt wurde. Im Jahr 1751 identifizierte ein schwedischer Chemiker und Schüler von Stahl namens Axel Fredrik Cronstedt eine Verunreinigung im Kupfererz als separates metallisches Element, das er Nickel nannte. Cronstedt ist einer der Begründer der modernen Mineralogie. [45] Cronstedt entdeckte 1751 auch das Mineral Scheelit, das er Wolfram nannte, was auf Schwedisch "schwerer Stein" bedeutet.
Im Jahr 1754 isolierte der schottische Chemiker Joseph Black Kohlendioxid, das er "fixierte Luft" nannte. [46] Im Jahr 1757 kreierte Louis Claude Cadet de Gassicourt bei der Untersuchung von Arsenverbindungen Cadets rauchende Flüssigkeit, die später als Cacodyloxid entdeckt wurde , die als erste synthetische metallorganische Verbindung angesehen wird. [47] 1758 formulierte Joseph Black das Konzept der latenten Wärme, um die Thermochemie von Phasenänderungen zu erklären. [48] Im Jahre 1766 isolierte der englische Chemiker Henry Cavendish "brennbar" Luft". Cavendish entdeckte Wasserstoff als farbloses, geruchloses Gas, das verbrennt und mit Luft ein explosionsfähiges Gemisch bilden kann, und veröffentlichte einen Artikel über die Erzeugung von Wasser durch Verbrennen brennbarer Luft (dh Wasserstoff) in enträtselter Luft (jetzt als Sauerstoff bekannt). Letzteres ist Bestandteil der atmosphärischen Luft (Phlogiston-Theorie).
1773 entdeckte der schwedische Chemiker Carl Wilhelm Scheele Sauerstoff, den er "Feuerluft" nannte, veröffentlichte seine Errungenschaft jedoch nicht sofort. [49] 1774 isolierte der englische Chemiker Joseph Priestley in seinem gasförmigen Zustand Sauerstoff unabhängig "dephlogisticated air" und veröffentlichte seine Arbeit vor Scheele. [50][51] Zu Lebzeiten gründete Priestleys beachtlicher wissenschaftlicher Ruf auf seiner Erfindung von Sodawasser, seinen Schriften über die Elektrizität und seiner Entdeckung mehrerer "Luft" (Gase), am meisten berühmt ist, was Priestley "entartete Luft" (Sauerstoff) genannt hat. Die Entschlossenheit von Priestley, die Phlogiston-Theorie zu verteidigen und die chemische Revolution abzulehnen, ließ ihn schließlich innerhalb der wissenschaftlichen Gemeinschaft isoliert.
Im Jahr 1781 entdeckte Carl Wilhelm Scheele, dass eine neue Säure, Wolframsäure, aus Cronstedts Scheelit (damals Wolfram genannt) hergestellt werden konnte. Scheele und Torbern Bergman meinten, durch die Reduktion dieser Säure könnte ein neues Metall erhalten werden. [52] 1783 fanden José und Fausto Elhuyar eine mit Wolframsäure identische Säure aus Wolframit. Später in diesem Jahr gelang es den Brüdern, das Metall, das jetzt als Wolfram bekannt ist, durch Reduktion dieser Säure mit Holzkohle zu isolieren, und ihnen wird die Entdeckung des Elements zugeschrieben. [53][54]
Volta und der Voltaic-Haufen [ edit ]
Der italienische Physiker Alessandro Volta konstruierte eine Vorrichtung zum Akkumulieren einer großen Ladung durch eine Reihe von Induktionen und Erdungen. Er untersuchte die Entdeckung "Tierelektrizität" aus den 1780er Jahren von Luigi Galvani und fand heraus, dass der elektrische Strom durch den Kontakt unterschiedlicher Metalle erzeugt wurde und dass das Froschschenkel nur als Detektor fungierte. Volta demonstrierte 1794, dass, wenn zwei Metalle und mit Salzlösung getränktes Tuch oder Karton in einem Kreislauf angeordnet sind, sie elektrischen Strom erzeugen.
Im Jahr 1800 stapelte Volta mehrere Paare abwechselnder Kupfer- (oder Silber-) und Zinkscheiben (Elektroden), die durch in Lauge (Elektrolyt) getränkte Tücher oder Kartons getrennt waren, um die Leitfähigkeit des Elektrolyts zu erhöhen. [55] Wenn der obere und der untere Kontakt waren Durch einen Draht verbunden, floss ein elektrischer Strom durch den Spannungspfahl und den Verbindungsdraht. So wird Volta der Bau der ersten elektrischen Batterie zur Stromerzeugung zugeschrieben. Voltas Methode des Stapelns von runden Platten aus Kupfer und Zink, die durch mit Salzlösung befeuchtete Pappscheiben getrennt wurden, wurde als voltaischer Stapel bezeichnet.
Somit gilt Volta als Begründer der Disziplin der Elektrochemie. [56] Eine Galvanikzelle (oder Voltaazelle) ist eine elektrochemische Zelle, die elektrische Energie aus spontanen Redoxreaktionen in der Zelle ableitet. Es besteht im Allgemeinen aus zwei verschiedenen Metallen, die durch eine Salzbrücke miteinander verbunden sind, oder einzelne Halbzellen, die durch eine poröse Membran getrennt sind.
Antoine-Laurent de Lavoisier [ edit ]
Obwohl die Archive der chemischen Forschung auf Arbeiten aus dem alten Babylonien, Ägypten und vor allem den Arabern und Persern nach dem Islam aufbauen, florierte die moderne Chemie aus der Zeit von Antoine-Laurent de Lavoisier, einem französischen Chemiker, der als "Vater der modernen Chemie" gefeiert wird. Lavoisier zeigte mit sorgfältigen Messungen, dass eine Umwandlung von Wasser in Erde nicht möglich ist, das Sediment jedoch aus kochendem Wasser aus dem Behälter stammt. Er verbrannte Phosphor und Schwefel in Luft und bewies, dass die Produkte mehr wiegen als das Original. Trotzdem ging das Gewicht aus der Luft verloren. So setzte er 1789 das Gesetz der Massenerhaltung ein, das auch "Lavoisiers Gesetz" genannt wird. [57]
Das weltweit erste Eis-Kalorimeter der Welt, das im Winter 1782-83 von Antoine Lavoisier und Pierre-Simon Laplace verwendet wurde zur Bestimmung der Wärme, die bei verschiedenen chemischen Veränderungen auftritt Berechnungen, die auf der Entdeckung der latenten Wärme durch Joseph Black beruhten. Diese Experimente stellen die Grundlage der Thermochemie dar.
Er wiederholte die Experimente von Priestley und zeigte, dass Luft aus zwei Teilen besteht, von denen sich einer mit Metallen zu Calxen verbindet. In Considérations Générales sur la Nature des Acides (1778) zeigte er, dass die für die Verbrennung verantwortliche "Luft" auch die Quelle des Säuregehalts war. Im nächsten Jahr nannte er diesen Teil Sauerstoff (griechisch für Säure-ehemalige) und den anderen Azote (griechisch für kein Leben). Lavoisier hat daher neben Priestley und Scheele Anspruch auf Sauerstoffentdeckung. He also discovered that the "inflammable air" discovered by Cavendish - which he termed hydrogen (Greek for water-former) - combined with oxygen to produce a dew, as Priestley had reported, which appeared to be water. In Reflexions sur le Phlogistique (1783), Lavoisier showed the phlogiston theory of combustion to be inconsistent. Mikhail Lomonosov independently established a tradition of chemistry in Russia in the 18th century. Lomonosov also rejected the phlogiston theory, and anticipated the kinetic theory of gases. Lomonosov regarded heat as a form of motion, and stated the idea of conservation of matter.
Lavoisier worked with Claude Louis Berthollet and others to devise a system of chemical nomenclature which serves as the basis of the modern system of naming chemical compounds. In his Methods of Chemical Nomenclature (1787), Lavoisier invented the system of naming and classification still largely in use today, including names such as sulfuric acid, sulfates, and sulfites. In 1785, Berthollet was the first to introduce the use of chlorine gas as a commercial bleach. In the same year he first determined the elemental composition of the gas ammonia. Berthollet first produced a modern bleaching liquid in 1789 by passing chlorine gas through a solution of sodium carbonate - the result was a weak solution of sodium hypochlorite. Another strong chlorine oxidant and bleach which he investigated and was the first to produce, potassium chlorate (KClO3), is known as Berthollet's Salt. Berthollet is also known for his scientific contributions to theory of chemical equilibria via the mechanism of reverse chemical reactions.
Traité élémentaire de chimie
Lavoisier's Traité Élémentaire de Chimie (Elementary Treatise of Chemistry, 1789) was the first modern chemical textbook, and presented a unified view of new theories of chemistry, contained a clear statement of the Law of Conservation of Mass, and denied the existence of phlogiston. In addition, it contained a list of elements, or substances that could not be broken down further, which included oxygen, nitrogen, hydrogen, phosphorus, mercury, zinc, and sulfur. His list, however, also included light, and caloric, which he believed to be material substances. In the work, Lavoisier underscored the observational basis of his chemistry, stating "I have tried...to arrive at the truth by linking up facts; to suppress as much as possible the use of reasoning, which is often an unreliable instrument which deceives us, in order to follow as much as possible the torch of observation and of experiment." Nevertheless, he believed that the real existence of atoms was philosophically impossible. Lavoisier demonstrated that organisms disassemble and reconstitute atmospheric air in the same manner as a burning body.
With Pierre-Simon Laplace, Lavoisier used a calorimeter to estimate the heat evolved per unit of carbon dioxide produced. They found the same ratio for a flame and animals, indicating that animals produced energy by a type of combustion. Lavoisier believed in the radical theory, believing that radicals, which function as a single group in a chemical reaction, would combine with oxygen in reactions. He believed all acids contained oxygen. He also discovered that diamond is a crystalline form of carbon.
While many of Lavoisier's partners were influential for the advancement of chemistry as a scientific discipline, his wife Marie-Anne Lavoisier was arguably the most influential of them all. Upon their marriage, Mme. Lavoisier began to study chemistry, English, and drawing in order to help her husband in his work either by translating papers into English, a language which Lavoisier did not know, or by keeping records and drawing the various apparatuses that Lavoisier used in his labs.[58] Through her ability to read and translate articles from Britain for her husband, Lavoisier had access knowledge from many of the chemical advances happening outside of his lab.[58] Furthermore, Mme. Lavoisier kept records of Lavoisier's work and ensured that his works were published.[58] The first sign of Marie-Anne's true potential as a chemist in Lavoisier's lab came when she was translating a book by the scientist Richard Kirwan. While translating, she stumbled upon and corrected multiple errors. When she presented her translation, along with her notes to Lavoisier [58] Her edits and contributions led to Lavoisier's refutation of the theory of phlogiston.
Lavoisier made many fundamental contributions to the science of chemistry. Following Lavoisier's work, chemistry acquired a strict quantitative nature, allowing reliable predictions to be made. The revolution in chemistry which he brought about was a result of a conscious effort to fit all experiments into the framework of a single theory. He established the consistent use of chemical balance, used oxygen to overthrow the phlogiston theory, and developed a new system of chemical nomenclature. Lavoisier was beheaded during the French Revolution.
19th century[edit]
In 1802, French American chemist and industrialist Éleuthère Irénée du Pont, who learned manufacture of gunpowder and explosives under Antoine Lavoisier, founded a gunpowder manufacturer in Delaware known as E. I. du Pont de Nemours and Company. The French Revolution forced his family to move to the United States where du Pont started a gunpowder mill on the Brandywine River in Delaware. Wanting to make the best powder possible, du Pont was vigilant about the quality of the materials he used. For 32 years, du Pont served as president of E. I. du Pont de Nemours and Company, which eventually grew into one of the largest and most successful companies in America.
Throughout the 19th century, chemistry was divided between those who followed the atomic theory of John Dalton and those who did not, such as Wilhelm Ostwald and Ernst Mach.[59] Although such proponents of the atomic theory as Amedeo Avogadro and Ludwig Boltzmann made great advances in explaining the behavior of gases, this dispute was not finally settled until Jean Perrin's experimental investigation of Einstein's atomic explanation of Brownian motion in the first decade of the 20th century.[59]
Well before the dispute had been settled, many had already applied the concept of atomism to chemistry. A major example was the ion theory of Svante Arrhenius which anticipated ideas about atomic substructure that did not fully develop until the 20th century. Michael Faraday was another early worker, whose major contribution to chemistry was electrochemistry, in which (among other things) a certain quantity of electricity during electrolysis or electrodeposition of metals was shown to be associated with certain quantities of chemical elements, and fixed quantities of the elements therefore with each other, in specific ratios.[citation needed] These findings, like those of Dalton's combining ratios, were early clues to the atomic nature of matter.
John Dalton[edit]
John Dalton is remembered for his work on partial pressures in gases, color blindness, and atomic theory
In 1803, English meteorologist and chemist John Dalton proposed Dalton's law, which describes the relationship between the components in a mixture of gases and the relative pressure each contributes to that of the overall mixture.[60] Discovered in 1801, this concept is also known as Dalton's law of partial pressures.
Dalton also proposed a modern atomic theory in 1803 which stated that all matter was composed of small indivisible particles termed atoms, atoms of a given element possess unique characteristics and weight, and three types of atoms exist: simple (elements), compound (simple molecules), and complex (complex molecules). In 1808, Dalton first published New System of Chemical Philosophy (1808-1827), in which he outlined the first modern scientific description of the atomic theory. This work identified chemical elements as a specific type of atom, therefore rejecting Newton's theory of chemical affinities.
Instead, Dalton inferred proportions of elements in compounds by taking ratios of the weights of reactants, setting the atomic weight of hydrogen to be identically one. Following Jeremias Benjamin Richter (known for introducing the term stoichiometry), he proposed that chemical elements combine in integral ratios. This is known as the law of multiple proportions or Dalton's law, and Dalton included a clear description of the law in his New System of Chemical Philosophy. The law of multiple proportions is one of the basic laws of stoichiometry used to establish the atomic theory. Despite the importance of the work as the first view of atoms as physically real entities and introduction of a system of chemical symbols, New System of Chemical Philosophy devoted almost as much space to the caloric theory as to atomism.
French chemist Joseph Proust proposed the law of definite proportions, which states that elements always combine in small, whole number ratios to form compounds, based on several experiments conducted between 1797 and 1804[61] Along with the law of multiple proportions, the law of definite proportions forms the basis of stoichiometry. The law of definite proportions and constant composition do not prove that atoms exist, but they are difficult to explain without assuming that chemical compounds are formed when atoms combine in constant proportions.
Jöns Jacob Berzelius[edit]
A Swedish chemist and disciple of Dalton, Jöns Jacob Berzelius embarked on a systematic program to try to make accurate and precise quantitative measurements and insure the purity of chemicals. Along with Lavoisier, Boyle, and Dalton, Berzelius is known as the father of modern chemistry. In 1828 he compiled a table of relative atomic weights, where oxygen was set to 100, and which included all of the elements known at the time. This work provided evidence in favor of Dalton's atomic theory: that inorganic chemical compounds are composed of atoms combined in whole number amounts. He determined the exact elementary constituents of large numbers of compounds. The results strongly confirmed Proust's Law of Definite Proportions. In his weights, he used oxygen as a standard, setting its weight equal to exactly 100. He also measured the weights of 43 elements. In discovering that atomic weights are not integer multiples of the weight of hydrogen, Berzelius also disproved Prout's hypothesis that elements are built up from atoms of hydrogen.
Motivated by his extensive atomic weight determinations and in a desire to aid his experiments, he introduced the classical system of chemical symbols and notation with his 1808 publishing of Lärbok i Kemienin which elements are abbreviated by one or two letters to make a distinct abbreviation from their Latin name. This system of chemical notation—in which the elements were given simple written labels, such as O for oxygen, or Fe for iron, with proportions noted by numbers—is the same basic system used today. The only difference is that instead of the subscript number used today (e.g., H2O), Berzelius used a superscript (H2O). Berzelius is credited with identifying the chemical elements silicon, selenium, thorium, and cerium. Students working in Berzelius's laboratory also discovered lithium and vanadium.
Berzelius developed the radical theory of chemical combination, which holds that reactions occur as stable groups of atoms called radicals are exchanged between molecules. He believed that salts are compounds of an acid and bases, and discovered that the anions in acids would be attracted to a positive electrode (the anode), whereas the cations in a base would be attracted to a negative electrode (the cathode). Berzelius did not believe in the Vitalism Theory, but instead in a regulative force which produced organization of tissues in an organism. Berzelius is also credited with originating the chemical terms "catalysis", "polymer", "isomer", and "allotrope", although his original definitions differ dramatically from modern usage. For example, he coined the term "polymer" in 1833 to describe organic compounds which shared identical empirical formulas but which differed in overall molecular weight, the larger of the compounds being described as "polymers" of the smallest. By this long superseded, pre-structural definition, glucose (C6H12O6) was viewed as a polymer of formaldehyde (CH2O).
New elements and gas laws[edit]
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.[62][63] He worked with electrolysis throughout his life and, in 1808, he isolated magnesium, strontium[64] and barium.[65]
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.[66] 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.
Joseph Louis Gay-Lussac, who stated that the ratio between the volumes of the reactant gases and the products can be expressed in simple whole numbers.
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.[67] The law was independently discovered by British natural philosopher John Dalton by 1801, although Dalton's description was less thorough than Gay-Lussac's.[68][69] 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.[70][71] 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.[72][73][74] It was Gay-Lussac who suggested the name "iode"from the Greek word ιώδες (iodes) for violet (because of the color of iodine vapor).[70][72] Ampère had given some of his sample to Humphry Davy. Davy did some experiments on the substance and noted its similarity to chlorine.[75] Davy sent a letter dated December 10 to the Royal Society of London stating that he had identified a new element.[76] 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.[77]
Amedeo Avogadro, who postulated that, under controlled conditions of temperature and pressure, equal volumes of gases contain an equal number of molecules. This is known as Avogadro's law.
After Dalton published his atomic theory in 1808, certain of his central ideas were soon adopted by most chemists. However, uncertainty persisted for half a century about how atomic theory was to be configured and applied to concrete situations; chemists in different countries developed several different incompatible atomistic systems. A paper that suggested a way out of this difficult situation was published as early as 1811 by the Italian physicist Amedeo Avogadro (1776-1856), who hypothesized that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules, from which it followed that relative molecular weights of any two gases are the same as the ratio of the densities of the two gases under the same conditions of temperature and pressure. Avogadro also reasoned that simple gases were not formed of solitary atoms but were instead compound molecules of two or more atoms. Thus Avogadro was able to overcome the difficulty that Dalton and others had encountered when Gay-Lussac reported that above 100 °C the volume of water vapor was twice the volume of the oxygen used to form it. According to Avogadro, the molecule of oxygen had split into two atoms in the course of forming water vapor.
Avogadro's hypothesis was neglected for half a century after it was first published. Many reasons for this neglect have been cited, including some theoretical problems, such as Jöns Jacob Berzelius's "dualism", which asserted that compounds are held together by the attraction of positive and negative electrical charges, making it inconceivable that a molecule composed of two electrically similar atoms—as in oxygen—could exist. An additional barrier to acceptance was the fact that many chemists were reluctant to adopt physical methods (such as vapour-density determinations) to solve their problems. By mid-century, however, some leading figures had begun to view the chaotic multiplicity of competing systems of atomic weights and molecular formulas as intolerable. Moreover, purely chemical evidence began to mount that suggested Avogadro's approach might be right after all. During the 1850s, younger chemists, such as Alexander Williamson in England, Charles Gerhardt and Charles-Adolphe Wurtz in France, and August Kekulé in Germany, began to advocate reforming theoretical chemistry to make it consistent with Avogadrian theory.
Wöhler and the vitalism debate[edit]
Structural formula of urea
In 1825, Friedrich Wöhler and Justus von Liebig performed the first confirmed discovery and explanation of isomers, earlier named by Berzelius. Working with cyanic acid and fulminic acid, they correctly deduced that isomerism was caused by differing arrangements of atoms within a molecular structure. In 1827, William Prout classified biomolecules into their modern groupings: carbohydrates, proteins and lipids. After the nature of combustion was settled, a dispute about vitalism and the essential distinction between organic and inorganic substances began. The vitalism question was revolutionized in 1828 when Friedrich Wöhler synthesized urea, thereby establishing that organic compounds could be produced from inorganic starting materials and disproving the theory of vitalism.
This opened a new research field in chemistry, and by the end of the 19th century, scientists were able to synthesize hundreds of organic compounds. The most important among them are mauve, magenta, and other synthetic dyes, as well as the widely used drug aspirin. The discovery of the artificial synthesis of urea contributed greatly to the theory of isomerism, as the empirical chemical formulas for urea and ammonium cyanate are identical (see Wöhler synthesis). In 1832, Friedrich Wöhler and Justus von Liebig discovered and explained functional groups and radicals in relation to organic chemistry, as well as first synthesizing benzaldehyde. Liebig, a German chemist, made major contributions to agricultural and biological chemistry, and worked on the organization of organic chemistry. Liebig is considered the "father of the fertilizer industry" for his discovery of nitrogen as an essential plant nutrient, and his formulation of the Law of the Minimum which described the effect of individual nutrients on crops.
Mid-1800s[edit]
In 1840, Germain Hess proposed Hess's law, an early statement of the law of conservation of energy, which establishes that energy changes in a chemical process depend only on the states of the starting and product materials and not on the specific pathway taken between the two states. In 1847, Hermann Kolbe obtained acetic acid from completely inorganic sources, further disproving vitalism. In 1848, William Thomson, 1st Baron Kelvin (commonly known as Lord Kelvin) established the concept of absolute zero, the temperature at which all molecular motion ceases. In 1849, Louis Pasteur discovered that the racemic form of tartaric acid is a mixture of the levorotatory and dextrotatory forms, thus clarifying the nature of optical rotation and advancing the field of stereochemistry.[78] In 1852, August Beer proposed Beer's law, which explains the relationship between the composition of a mixture and the amount of light it will absorb. Based partly on earlier work by Pierre Bouguer and Johann Heinrich Lambert, it established the analytical technique known as spectrophotometry.[79] In 1855, Benjamin Silliman, Jr. pioneered methods of petroleum cracking, which made the entire modern petrochemical industry possible.[80]
Avogadro's hypothesis began to gain broad appeal among chemists only after his compatriot and fellow scientist Stanislao Cannizzaro demonstrated its value in 1858, two years after Avogadro's death. Cannizzaro's chemical interests had originally centered on natural products and on reactions of aromatic compounds; in 1853 he discovered that when benzaldehyde is treated with concentrated base, both benzoic acid and benzyl alcohol are produced—a phenomenon known today as the Cannizzaro reaction. In his 1858 pamphlet, Cannizzaro showed that a complete return to the ideas of Avogadro could be used to construct a consistent and robust theoretical structure that fit nearly all of the available empirical evidence. For instance, he pointed to evidence that suggested that not all elementary gases consist of two atoms per molecule—some were monatomic, most were diatomic, and a few were even more complex.
Another point of contention had been the formulas for compounds of the alkali metals (such as sodium) and the alkaline earth metals (such as calcium), which, in view of their striking chemical analogies, most chemists had wanted to assign to the same formula type. Cannizzaro argued that placing these metals in different categories had the beneficial result of eliminating certain anomalies when using their physical properties to deduce atomic weights. Unfortunately, Cannizzaro's pamphlet was published initially only in Italian and had little immediate impact. The real breakthrough came with an international chemical congress held in the German town of Karlsruhe in September 1860, at which most of the leading European chemists were present. The Karlsruhe Congress had been arranged by Kekulé, Wurtz, and a few others who shared Cannizzaro's sense of the direction chemistry should go. Speaking in French (as everyone there did), Cannizzaro's eloquence and logic made an indelible impression on the assembled body. Moreover, his friend Angelo Pavesi distributed Cannizzaro's pamphlet to attendees at the end of the meeting; more than one chemist later wrote of the decisive impression the reading of this document provided. For instance, Lothar Meyer later wrote that on reading Cannizzaro's paper, "The scales seemed to fall from my eyes."[81] Cannizzaro thus played a crucial role in winning the battle for reform. The system advocated by him, and soon thereafter adopted by most leading chemists, is substantially identical to what is still used today.
Perkin, Crookes, and Nobel[edit]
In 1856, Sir William Henry Perkin, age 18, given a challenge by his professor, August Wilhelm von Hofmann, sought to synthesize quinine, the anti-malaria drug, from coal tar. In one attempt, Perkin oxidized aniline using potassium dichromate, whose toluidine impurities reacted with the aniline and yielded a black solid—suggesting a "failed" organic synthesis. Cleaning the flask with alcohol, Perkin noticed purple portions of the solution: a byproduct of the attempt was the first synthetic dye, known as mauveine or Perkin's mauve. Perkin's discovery is the foundation of the dye synthesis industry, one of the earliest successful chemical industries.
German chemist August Kekulé von Stradonitz's most important single contribution was his structural theory of organic composition, outlined in two articles published in 1857 and 1858 and treated in great detail in the pages of his extraordinarily popular Lehrbuch der organischen Chemie ("Textbook of Organic Chemistry"), the first installment of which appeared in 1859 and gradually extended to four volumes. Kekulé argued that tetravalent carbon atoms - that is, carbon forming exactly four chemical bonds - could link together to form what he called a "carbon chain" or a "carbon skeleton," to which other atoms with other valences (such as hydrogen, oxygen, nitrogen, and chlorine) could join. He was convinced that it was possible for the chemist to specify this detailed molecular architecture for at least the simpler organic compounds known in his day. Kekulé was not the only chemist to make such claims in this era. The Scottish chemist Archibald Scott Couper published a substantially similar theory nearly simultaneously, and the Russian chemist Aleksandr Butlerov did much to clarify and expand structure theory. However, it was predominantly Kekulé's ideas that prevailed in the chemical community.
A Crookes tube (2 views): light and dark. Electrons travel in straight lines from the cathode (left), as evidenced by the shadow cast from the Maltese cross on the fluorescence of the righthand end. The anode is at the bottom wire.
British chemist and physicist William Crookes is noted for his cathode ray studies, fundamental in the development of atomic physics. His researches on electrical discharges through a rarefied gas led him to observe the dark space around the cathode, now called the Crookes dark space. He demonstrated that cathode rays travel in straight lines and produce phosphorescence and heat when they strike certain materials. A pioneer of vacuum tubes, Crookes invented the Crookes tube - an early experimental discharge tube, with partial vacuum with which he studied the behavior of cathode rays. With the introduction of spectrum analysis by Robert Bunsen and Gustav Kirchhoff (1859-1860), Crookes applied the new technique to the study of selenium compounds. Bunsen and Kirchhoff had previously used spectroscopy as a means of chemical analysis to discover caesium and rubidium. In 1861, Crookes used this process to discover thallium in some seleniferous deposits. He continued work on that new element, isolated it, studied its properties, and in 1873 determined its atomic weight. During his studies of thallium, Crookes discovered the principle of the Crookes radiometer, a device that converts light radiation into rotary motion. The principle of this radiometer has found numerous applications in the development of sensitive measuring instruments.
In 1862, Alexander Parkes exhibited Parkesine, one of the earliest synthetic polymers, at the International Exhibition in London. This discovery formed the foundation of the modern plastics industry. In 1864, Cato Maximilian Guldberg and Peter Waage, building on Claude Louis Berthollet's ideas, proposed the law of mass action. In 1865, Johann Josef Loschmidt determined the exact number of molecules in a mole, later named Avogadro's number.
In 1865, August Kekulé, based partially on the work of Loschmidt and others, established the structure of benzene as a six carbon ring with alternating single and double bonds. Kekulé's novel proposal for benzene's cyclic structure was much contested but was never replaced by a superior theory. This theory provided the scientific basis for the dramatic expansion of the German chemical industry in the last third of the 19th century. Today, the large majority of known organic compounds are aromatic, and all of them contain at least one hexagonal benzene ring of the sort that Kekulé advocated. Kekulé is also famous for having clarified the nature of aromatic compounds, which are compounds based on the benzene molecule. In 1865, Adolf von Baeyer began work on indigo dye, a milestone in modern industrial organic chemistry which revolutionized the dye industry.
Swedish chemist and inventor Alfred Nobel found that when nitroglycerin was incorporated in an absorbent inert substance like kieselguhr (diatomaceous earth) it became safer and more convenient to handle, and this mixture he patented in 1867 as dynamite. Nobel later on combined nitroglycerin with various nitrocellulose compounds, similar to collodion, but settled on a more efficient recipe combining another nitrate explosive, and obtained a transparent, jelly-like substance, which was a more powerful explosive than dynamite. Gelignite, or blasting gelatin, as it was named, was patented in 1876; and was followed by a host of similar combinations, modified by the addition of potassium nitrate and various other substances.
Mendeleev's periodic table[edit]
An important breakthrough in making sense of the list of known chemical elements (as well as in understanding the internal structure of atoms) was Dmitri Mendeleev's development of the first modern periodic table, or the periodic classification of the elements. Mendeleev, a Russian chemist, felt that there was some type of order to the elements and he spent more than thirteen years of his life collecting data and assembling the concept, initially with the idea of resolving some of the disorder in the field for his students. Mendeleev found that, when all the known chemical elements were arranged in order of increasing atomic weight, the resulting table displayed a recurring pattern, or periodicity, of properties within groups of elements. Mendeleev's law allowed him to build up a systematic periodic table of all the 66 elements then known based on atomic mass, which he published in Principles of Chemistry in 1869. His first Periodic Table was compiled on the basis of arranging the elements in ascending order of atomic weight and grouping them by similarity of properties.
Mendeleev had such faith in the validity of the periodic law that he proposed changes to the generally accepted values for the atomic weight of a few elements and, in his version of the periodic table of 1871, predicted the locations within the table of unknown elements together with their properties. He even predicted the likely properties of three yet-to-be-discovered elements, which he called ekaboron (Eb), ekaaluminium (Ea), and ekasilicon (Es), which proved to be good predictors of the properties of scandium, gallium, and germanium, respectively, which each fill the spot in the periodic table assigned by Mendeleev.
At first the periodic system did not raise interest among chemists. However, with the discovery of the predicted elements, notably gallium in 1875, scandium in 1879, and germanium in 1886, it began to win wide acceptance. The subsequent proof of many of his predictions within his lifetime brought fame to Mendeleev as the founder of the periodic law. This organization surpassed earlier attempts at classification by Alexandre-Émile Béguyer de Chancourtois, who published the telluric helix, an early, three-dimensional version of the periodic table of the elements in 1862, John Newlands, who proposed the law of octaves (a precursor to the periodic law) in 1864, and Lothar Meyer, who developed an early version of the periodic table with 28 elements organized by valence in 1864. Mendeleev's table did not include any of the noble gases, however, which had not yet been discovered. Gradually the periodic law and table became the framework for a great part of chemical theory. By the time Mendeleev died in 1907, he enjoyed international recognition and had received distinctions and awards from many countries.
In 1873, Jacobus Henricus van 't Hoff and Joseph Achille Le Bel, working independently, developed a model of chemical bonding that explained the chirality experiments of Pasteur and provided a physical cause for optical activity in chiral compounds.[82] van 't Hoff's publication, called Voorstel tot Uitbreiding der Tegenwoordige in de Scheikunde gebruikte Structuurformules in de Ruimteetc. (Proposal for the development of 3-dimensional chemical structural formulae) and consisting of twelve pages text and one page diagrams, gave the impetus to the development of stereochemistry. The concept of the "asymmetrical carbon atom", dealt with in this publication, supplied an explanation of the occurrence of numerous isomers, inexplicable by means of the then current structural formulae. At the same time he pointed out the existence of relationship between optical activity and the presence of an asymmetrical carbon atom.
Josiah Willard Gibbs[edit]
American mathematical physicist J. Willard Gibbs's work on the applications of thermodynamics was instrumental in transforming physical chemistry into a rigorous deductive science. During the years from 1876 to 1878, Gibbs worked on the principles of thermodynamics, applying them to the complex processes involved in chemical reactions. He discovered the concept of chemical potential, or the "fuel" that makes chemical reactions work. In 1876 he published his most famous contribution, "On the Equilibrium of Heterogeneous Substances", a compilation of his work on thermodynamics and physical chemistry which laid out the concept of free energy to explain the physical basis of chemical equilibria.[83] In these essays were the beginnings of Gibbs’ theories of phases of matter: he considered each state of matter a phase, and each substance a component. Gibbs took all of the variables involved in a chemical reaction - temperature, pressure, energy, volume, and entropy - and included them in one simple equation known as Gibbs' phase rule.
Within this paper was perhaps his most outstanding contribution, the introduction of the concept free energy, now universally called Gibbs free energy in his honor. The Gibbs free energy relates the tendency of a physical or chemical system to simultaneously lower its energy and increase its disorder, or entropy, in a spontaneous natural process. Gibbs's approach allows a researcher to calculate the change in free energy in the process, such as in a chemical reaction, and how fast it will happen. Since virtually all chemical processes and many physical ones involve such changes, his work has significantly impacted both the theoretical and experiential aspects of these sciences. In 1877, Ludwig Boltzmann established statistical derivations of many important physical and chemical concepts, including entropy, and distributions of molecular velocities in the gas phase.[84] Together with Boltzmann and James Clerk Maxwell, Gibbs created a new branch of theoretical physics called statistical mechanics (a term that he coined), explaining the laws of thermodynamics as consequences of the statistical properties of large ensembles of particles. Gibbs also worked on the application of Maxwell's equations to problems in physical optics. Gibbs's derivation of the phenomenological laws of thermodynamics from the statistical properties of systems with many particles was presented in his highly influential textbook Elementary Principles in Statistical Mechanicspublished in 1902, a year before his death. In that work, Gibbs reviewed the relationship between the laws of thermodynamics and statistical theory of molecular motions. The overshooting of the original function by partial sums of Fourier series at points of discontinuity is known as the Gibbs phenomenon.
Late 19th century[edit]
German engineer Carl von Linde's invention of a continuous process of liquefying gases in large quantities formed a basis for the modern technology of refrigeration and provided both impetus and means for conducting scientific research at low temperatures and very high vacuums. He developed a dimethyl ether refrigerator (1874) and an ammonia refrigerator (1876). Though other refrigeration units had been developed earlier, Linde's were the first to be designed with the aim of precise calculations of efficiency. In 1895 he set up a large-scale plant for the production of liquid air. Six years later he developed a method for separating pure liquid oxygen from liquid air that resulted in widespread industrial conversion to processes utilizing oxygen (e.g., in steel manufacture).
In 1883, Svante Arrhenius developed an ion theory to explain conductivity in electrolytes.[85] In 1884, Jacobus Henricus van 't Hoff published Études de Dynamique chimique (Studies in Dynamic Chemistry), a seminal study on chemical kinetics.[86] In this work, van 't Hoff entered for the first time the field of physical chemistry. Of great importance was his development of the general thermodynamic relationship between the heat of conversion and the displacement of the equilibrium as a result of temperature variation. At constant volume, the equilibrium in a system will tend to shift in such a direction as to oppose the temperature change which is imposed upon the system. Thus, lowering the temperature results in heat development while increasing the temperature results in heat absorption. This principle of mobile equilibrium was subsequently (1885) put in a general form by Henry Louis Le Chatelier, who extended the principle to include compensation, by change of volume, for imposed pressure changes. The van 't Hoff-Le Chatelier principle, or simply Le Chatelier's principle, explains the response of dynamic chemical equilibria to external stresses.[87]
In 1884, Hermann Emil Fischer proposed the structure of purine, a key structure in many biomolecules, which he later synthesized in 1898. He also began work on the chemistry of glucose and related sugars.[88] In 1885, Eugene Goldstein named the cathode ray, later discovered to be composed of electrons, and the canal ray, later discovered to be positive hydrogen ions that had been stripped of their electrons in a cathode ray tube; these would later be named protons.[89] The year 1885 also saw the publishing of J. H. van 't Hoff's L'Équilibre chimique dans les Systèmes gazeux ou dissous à I'État dilué (Chemical equilibria in gaseous systems or strongly diluted solutions), which dealt with this theory of dilute solutions. Here he demonstrated that the "osmotic pressure" in solutions which are sufficiently dilute is proportionate to the concentration and the absolute temperature so that this pressure can be represented by a formula which only deviates from the formula for gas pressure by a coefficient i. He also determined the value of i by various methods, for example by means of the vapor pressure and François-Marie Raoult's results on the lowering of the freezing point. Thus van 't Hoff was able to prove that thermodynamic laws are not only valid for gases, but also for dilute solutions. His pressure laws, given general validity by the electrolytic dissociation theory of Arrhenius (1884-1887) - the first foreigner who came to work with him in Amsterdam (1888) - are considered the most comprehensive and important in the realm of natural sciences. In 1893, Alfred Werner discovered the octahedral structure of cobalt complexes, thus establishing the field of coordination chemistry.[90]
Ramsay's discovery of the noble gases[edit]
The most celebrated discoveries of Scottish chemist William Ramsay were made in inorganic chemistry. Ramsay was intrigued by the British physicist John Strutt, 3rd Baron Rayleigh's 1892 discovery that the atomic weight of nitrogen found in chemical compounds was lower than that of nitrogen found in the atmosphere. He ascribed this discrepancy to a light gas included in chemical compounds of nitrogen, while Ramsay suspected a hitherto undiscovered heavy gas in atmospheric nitrogen. Using two different methods to remove all known gases from air, Ramsay and Lord Rayleigh were able to announce in 1894 that they had found a monatomic, chemically inert gaseous element that constituted nearly 1 percent of the atmosphere; they named it argon.
The following year, Ramsay liberated another inert gas from a mineral called cleveite; this proved to be helium, previously known only in the solar spectrum. In his book The Gases of the Atmosphere (1896), Ramsay showed that the positions of helium and argon in the periodic table of elements indicated that at least three more noble gases might exist. In 1898 Ramsay and the British chemist Morris W. Travers isolated these elements—called neon, krypton, and xenon—from air brought to a liquid state at low temperature and high pressure. Sir William Ramsay worked with Frederick Soddy to demonstrate, in 1903, that alpha particles (helium nuclei) were continually produced during the radioactive decay of a sample of radium. Ramsay was awarded the 1904 Nobel Prize for Chemistry in recognition of "services in the discovery of the inert gaseous elements in air, and his determination of their place in the periodic system."
In 1897, J. J. Thomson discovered the electron using the cathode ray tube. In 1898, Wilhelm Wien demonstrated that canal rays (streams of positive ions) can be deflected by magnetic fields, and that the amount of deflection is proportional to the mass-to-charge ratio. This discovery would lead to the analytical technique known as mass spectrometry in 1912.[91]
Marie and Pierre Curie[edit]
Marie Curie, a pioneer in the field of radioactivity and the first twice-honored Nobel laureate (and still the only one in two different sciences)
Marie Skłodowska-Curie was a Polish-born French physicist and chemist who is famous for her pioneering research on radioactivity. She and her husband are considered to have laid the cornerstone of the nuclear age with their research on radioactivity. Marie was fascinated with the work of Henri Becquerel, a French physicist who discovered in 1896 that uranium casts off rays similar to the X-rays discovered by Wilhelm Röntgen. Marie Curie began studying uranium in late 1897 and theorized, according to a 1904 article she wrote for Century magazine, "that the emission of rays by the compounds of uranium is a property of the metal itself—that it is an atomic property of the element uranium independent of its chemical or physical state." Curie took Becquerel's work a few steps further, conducting her own experiments on uranium rays. She discovered that the rays remained constant, no matter the condition or form of the uranium. The rays, she theorized, came from the element's atomic structure. This revolutionary idea created the field of atomic physics and the Curies coined the word radioactivity to describe the phenomena.
Pierre and Marie further explored radioactivity by working to separate the substances in uranium ores and then using the electrometer to make radiation measurements to ‘trace’ the minute amount of unknown radioactive element among the fractions that resulted. Working with the mineral pitchblende, the pair discovered a new radioactive element in 1898. They named the element polonium, after Marie's native country of Poland. On December 21, 1898, the Curies detected the presence of another radioactive material in the pitchblende. They presented this finding to the French Academy of Sciences on December 26, proposing that the new element be called radium. The Curies then went to work isolating polonium and radium from naturally occurring compounds to prove that they were new elements. In 1902, the Curies announced that they had produced a decigram of pure radium, demonstrating its existence as a unique chemical element. While it took three years for them to isolate radium, they were never able to isolate polonium. Along with the discovery of two new elements and finding techniques for isolating radioactive isotopes, Curie oversaw the world's first studies into the treatment of neoplasms, using radioactive isotopes. With Henri Becquerel and her husband, Pierre Curie, she was awarded the 1903 Nobel Prize for Physics. She was the sole winner of the 1911 Nobel Prize for Chemistry. She was the first woman to win a Nobel Prize, and she is the only woman to win the award in two different fields.
While working with Marie to extract pure substances from ores, an undertaking that really required industrial resources but that they achieved in relatively primitive conditions, Pierre himself concentrated on the physical study (including luminous and chemical effects) of the new radiations. Through the action of magnetic fields on the rays given out by the radium, he proved the existence of particles electrically positive, negative, and neutral; these Ernest Rutherford was afterward to call alpha, beta, and gamma rays. Pierre then studied these radiations by calorimetry and also observed the physiological effects of radium, thus opening the way to radium therapy. Among Pierre Curie's discoveries were that ferromagnetic substances exhibited a critical temperature transition, above which the substances lost their ferromagnetic behavior - this is known as the "Curie point." He was elected to the Academy of Sciences (1905), having in 1903 jointly with Marie received the Royal Society's prestigious Davy Medal and jointly with her and Becquerel the Nobel Prize for Physics. He was run over by a carriage in the rue Dauphine in Paris in 1906 and died instantly. His complete works were published in 1908.
Ernest Rutherford[edit]
Ernest Rutherford, discoverer of the nucleus and considered the father of nuclear physics
New Zealand-born chemist and physicist Ernest Rutherford is considered to be "the father of nuclear physics." Rutherford is best known for devising the names alpha, beta, and gamma to classify various forms of radioactive "rays" which were poorly understood at his time (alpha and beta rays are particle beams, while gamma rays are a form of high-energy electromagnetic radiation). Rutherford deflected alpha rays with both electric and magnetic fields in 1903. Working with Frederick Soddy, Rutherford explained that radioactivity is due to the transmutation of elements, now known to involve nuclear reactions.
Top: Predicted results based on the then-accepted plum pudding model of the atom. Bottom: Observed results. Rutherford disproved the plum pudding model and concluded that the positive charge of the atom must be concentrated in a small, central nucleus.
He also observed that the intensity of radioactivity of a radioactive element decreases over a unique and regular amount of time until a point of stability, and he named the halving time the "half-life." In 1901 and 1902 he worked with Frederick Soddy to prove that atoms of one radioactive element would spontaneously turn into another, by expelling a piece of the atom at high velocity. In 1906 at the University of Manchester, Rutherford oversaw an experiment conducted by his students Hans Geiger (known for the Geiger counter) and Ernest Marsden. In the Geiger–Marsden experiment, a beam of alpha particles, generated by the radioactive decay of radon, was directed normally onto a sheet of very thin gold foil in an evacuated chamber. Under the prevailing plum pudding model, the alpha particles should all have passed through the foil and hit the detector screen, or have been deflected by, at most, a few degrees.
However, the actual results surprised Rutherford. Although many of the alpha particles did pass through as expected, many others were deflected at small angles while others were reflected back to the alpha source. They observed that a very small percentage of particles were deflected through angles much larger than 90 degrees. The gold foil experiment showed large deflections for a small fraction of incident particles. Rutherford realized that, because some of the alpha particles were deflected or reflected, the atom had a concentrated centre of positive charge and of relatively large mass - Rutherford later termed this positive center the "atomic nucleus". The alpha particles had either hit the positive centre directly or passed by it close enough to be affected by its positive charge. Since many other particles passed through the gold foil, the positive centre would have to be a relatively small size compared to the rest of the atom - meaning that the atom is mostly open space. From his results, Rutherford developed a model of the atom that was similar to the solar system, known as Rutherford model. Like planets, electrons orbited a central, sun-like nucleus. For his work with radiation and the atomic nucleus, Rutherford received the 1908 Nobel Prize in Chemistry.
20th century[edit]
In 1903, Mikhail Tsvet invented chromatography, an important analytic technique. In 1904, Hantaro Nagaoka proposed an early nuclear model of the atom, where electrons orbit a dense massive nucleus. In 1905, Fritz Haber and Carl Bosch developed the Haber process for making ammonia, a milestone in industrial chemistry with deep consequences in agriculture. The Haber process, or Haber-Bosch process, combined nitrogen and hydrogen to form ammonia in industrial quantities for production of fertilizer and munitions. The food production for half the world's current population depends on this method for producing fertilizer. Haber, along with Max Born, proposed the Born–Haber cycle as a method for evaluating the lattice energy of an ionic solid. Haber has also been described as the "father of chemical warfare" for his work developing and deploying chlorine and other poisonous gases during World War I.
Robert A. Millikan, who is best known for measuring the charge on the electron, won the Nobel Prize in Physics in 1923.
In 1905, Albert Einstein explained Brownian motion in a way that definitively proved atomic theory. Leo Baekeland invented bakelite, one of the first commercially successful plastics. In 1909, American physicist Robert Andrews Millikan - who had studied in Europe under Walther Nernst and Max Planck - measured the charge of individual electrons with unprecedented accuracy through the oil drop experiment, in which he measured the electric charges on tiny falling water (and later oil) droplets. His study established that any particular droplet's electrical charge is a multiple of a definite, fundamental value — the electron's charge — and thus a confirmation that all electrons have the same charge and mass. Beginning in 1912, he spent several years investigating and finally proving Albert Einstein's proposed linear relationship between energy and frequency, and providing the first direct photoelectric support for Planck's constant. In 1923 Millikan was awarded the Nobel Prize for Physics.
In 1909, S. P. L. Sørensen invented the pH concept and develops methods for measuring acidity. In 1911, Antonius Van den Broek proposed the idea that the elements on the periodic table are more properly organized by positive nuclear charge rather than atomic weight. In 1911, the first Solvay Conference was held in Brussels, bringing together most of the most prominent scientists of the day. In 1912, William Henry Bragg and William Lawrence Bragg proposed Bragg's law and established the field of X-ray crystallography, an important tool for elucidating the crystal structure of substances. In 1912, Peter Debye develops the concept of molecular dipole to describe asymmetric charge distribution in some molecules.
Niels Bohr[edit]
In 1913, Niels Bohr, a Danish physicist, introduced the concepts of quantum mechanics to atomic structure by proposing what is now known as the Bohr model of the atom, where electrons exist only in strictly defined circular orbits around the nucleus similar to rungs on a ladder. The Bohr Model is a planetary model in which the negatively charged electrons orbit a small, positively charged nucleus similar to the planets orbiting the Sun (except that the orbits are not planar) - the gravitational force of the solar system is mathematically akin to the attractive Coulomb (electrical) force between the positively charged nucleus and the negatively charged electrons.
In the Bohr model, however, electrons orbit the nucleus in orbits that have a set size and energy - the energy levels are said to be quantizedwhich means that only certain orbits with certain radii are allowed; orbits in between simply don't exist. The energy of the orbit is related to its size - that is, the lowest energy is found in the smallest orbit. Bohr also postulated that electromagnetic radiation is absorbed or emitted when an electron moves from one orbit to another. Because only certain electron orbits are permitted, the emission of light accompanying a jump of an electron from an excited energy state to ground state produces a unique emission spectrum for each element.
Niels Bohr also worked on the principle of complementarity, which states that an electron can be interpreted in two mutually exclusive and valid ways. Electrons can be interpreted as wave or particle models. His hypothesis was that an incoming particle would strike the nucleus and create an excited compound nucleus. This formed the basis of his liquid drop model and later provided a theory base for the explanation of nuclear fission. Niels Bohr later received the Nobel Prize awarded to him in physics for his work.
In 1913, Henry Moseley, working from Van den Broek's earlier idea, introduces concept of atomic number to fix inadequacies of Mendeleev's periodic table, which had been based on atomic weight. The peak of Frederick Soddy's career in radiochemistry was in 1913 with his formulation of the concept of isotopes, which stated that certain elements exist in two or more forms which have different atomic weights but which are indistinguishable chemically. He is remembered for proving the existence of isotopes of certain radioactive elements, and is also credited, along with others, with the discovery of the element protactinium in 1917. In 1913, J. J. Thomson expanded on the work of Wien by showing that charged subatomic particles can be separated by their mass-to-charge ratio, a technique known as mass spectrometry.
Gilbert N. Lewis[edit]
American physical chemist Gilbert N. Lewis laid the foundation of valence bond theory; he was instrumental in developing a bonding theory based on the number of electrons in the outermost "valence" shell of the atom. In 1902, while Lewis was trying to explain valence to his students, he depicted atoms as constructed of a concentric series of cubes with electrons at each corner. This "cubic atom" explained the eight groups in the periodic table and represented his idea that chemical bonds are formed by electron transference to give each atom a complete set of eight outer electrons (an "octet").
Lewis's theory of chemical bonding continued to evolve and, in 1916, he published his seminal article "The Atom of the Molecule", which suggested that a chemical bond is a pair of electrons shared by two atoms. Lewis's model equated the classical chemical bond with the sharing of a pair of electrons between the two bonded atoms. Lewis introduced the "electron dot diagrams" in this paper to symbolize the electronic structures of atoms and molecules. Now known as Lewis structures, they are discussed in virtually every introductory chemistry book.
Shortly after publication of his 1916 paper, Lewis became involved with military research. He did not return to the subject of chemical bonding until 1923, when he masterfully summarized his model in a short monograph entitled Valence and the Structure of Atoms and Molecules. His renewal of interest in this subject was largely stimulated by the activities of the American chemist and General Electric researcher Irving Langmuir, who between 1919 and 1921 popularized and elaborated Lewis's model. Langmuir subsequently introduced the term covalent bond. In 1921, Otto Stern and Walther Gerlach establish concept of quantum mechanical spin in subatomic particles.
For cases where no sharing was involved, Lewis in 1923 developed the electron pair theory of acids and base: Lewis redefined an acid as any atom or molecule with an incomplete octet that was thus capable of accepting electrons from another atom; bases were, of course, electron donors. His theory is known as the concept of Lewis acids and bases. In 1923, G. N. Lewis and Merle Randall published Thermodynamics and the Free Energy of Chemical Substancesfirst modern treatise on chemical thermodynamics.
The 1920s saw a rapid adoption and application of Lewis's model of the electron-pair bond in the fields of organic and coordination chemistry. In organic chemistry, this was primarily due to the efforts of the British chemists Arthur Lapworth, Robert Robinson, Thomas Lowry, and Christopher Ingold; while in coordination chemistry, Lewis's bonding model was promoted through the efforts of the American chemist Maurice Huggins and the British chemist Nevil Sidgwick.
Quantum mechanics[edit]
In 1924, French quantum physicist Louis de Broglie published his thesis, in which he introduced a revolutionary theory of electron waves based on wave–particle duality in his thesis. In his time, the wave and particle interpretations of light and matter were seen as being at odds with one another, but de Broglie suggested that these seemingly different characteristics were instead the same behavior observed from different perspectives — that particles can behave like waves, and waves (radiation) can behave like particles. Broglie's proposal offered an explanation of the restriction motion of electrons within the atom. The first publications of Broglie's idea of "matter waves" had drawn little attention from other physicists, but a copy of his doctoral thesis chanced to reach Einstein, whose response was enthusiastic. Einstein stressed the importance of Broglie's work both explicitly and by building further on it.
In 1925, Austrian-born physicist Wolfgang Pauli developed the Pauli exclusion principle, which states that no two electrons around a single nucleus in an atom can occupy the same quantum state simultaneously, as described by four quantum numbers. Pauli made major contributions to quantum mechanics and quantum field theory - he was awarded the 1945 Nobel Prize for Physics for his discovery of the Pauli exclusion principle - as well as solid-state physics, and he successfully hypothesized the existence of the neutrino. In addition to his original work, he wrote masterful syntheses of several areas of physical theory that are considered classics of scientific literature.
In 1926 at the age of 39, Austrian theoretical physicist Erwin Schrödinger produced the papers that gave the foundations of quantum wave mechanics. In those papers he described his partial differential equation that is the basic equation of quantum mechanics and bears the same relation to the mechanics of the atom as Newton's equations of motion bear to planetary astronomy. Adopting a proposal made by Louis de Broglie in 1924 that particles of matter have a dual nature and in some situations act like waves, Schrödinger introduced a theory describing the behaviour of such a system by a wave equation that is now known as the Schrödinger equation. The solutions to Schrödinger's equation, unlike the solutions to Newton's equations, are wave functions that can only be related to the probable occurrence of physical events. The readily visualized sequence of events of the planetary orbits of Newton is, in quantum mechanics, replaced by the more abstract notion of probability. (This aspect of the quantum theory made Schrödinger and several other physicists profoundly unhappy, and he devoted much of his later life to formulating philosophical objections to the generally accepted interpretation of the theory that he had done so much to create.)
German theoretical physicist Werner Heisenberg was one of the key creators of quantum mechanics. In 1925, Heisenberg discovered a way to formulate quantum mechanics in terms of matrices. For that discovery, he was awarded the Nobel Prize for Physics for 1932. In 1927 he published his uncertainty principle, upon which he built his philosophy and for which he is best known. Heisenberg was able to demonstrate that if you were studying an electron in an atom you could say where it was (the electron's location) or where it was going (the electron's velocity), but it was impossible to express both at the same time. He also made important contributions to the theories of the hydrodynamics of turbulent flows, the atomic nucleus, ferromagnetism, cosmic rays, and subatomic particles, and he was instrumental in planning the first West German nuclear reactor at Karlsruhe, together with a research reactor in Munich, in 1957. Considerable controversy surrounds his work on atomic research during World War II.
Quantum chemistry[edit]
Some view the birth of quantum chemistry in the discovery of the Schrödinger equation and its application to the hydrogen atom in 1926.[citation needed] However, the 1927 article of Walter Heitler and Fritz London[92] is often recognised as the first milestone in the history of quantum chemistry. This is the first application of quantum mechanics to the diatomic hydrogen molecule, and thus to the phenomenon of the chemical bond. In the following years much progress was accomplished by Edward Teller, Robert S. Mulliken, Max Born, J. Robert Oppenheimer, Linus Pauling, Erich Hückel, Douglas Hartree, Vladimir Aleksandrovich Fock, to cite a few.[citation needed]
Still, skepticism remained as to the general power of quantum mechanics applied to complex chemical systems.[citation needed] The situation around 1930 is described by Paul Dirac:[93]
The underlying physical laws necessary for the mathematical theory of a large part of physics and the whole of chemistry are thus completely known, and the difficulty is only that the exact application of these laws leads to equations much too complicated to be soluble. It therefore becomes desirable that approximate practical methods of applying quantum mechanics should be developed, which can lead to an explanation of the main features of complex atomic systems without too much computation.
Hence the quantum mechanical methods developed in the 1930s and 1940s are often referred to as theoretical molecular or atomic physics to underline the fact that they were more the application of quantum mechanics to chemistry and spectroscopy than answers to chemically relevant questions. In 1951, a milestone article in quantum chemistry is the seminal paper of Clemens C. J. Roothaan on Roothaan equations.[94] It opened the avenue to the solution of the self-consistent field equations for small molecules like hydrogen or nitrogen. Those computations were performed with the help of tables of integrals which were computed on the most advanced computers of the time.[citation needed]
In the 1940s many physicists turned from molecular or atomic physics to nuclear physics (like J. Robert Oppenheimer or Edward Teller). Glenn T. Seaborg was an American nuclear chemist best known for his work on isolating and identifying transuranium elements (those heavier than uranium). He shared the 1951 Nobel Prize for Chemistry with Edwin Mattison McMillan for their independent discoveries of transuranium elements. Seaborgium was named in his honour, making him the only person, along Albert Einstein and Yuri Oganessian, for whom a chemical element was named during his lifetime.
Molecular biology and biochemistry[edit]
By the mid 20th century, in principle, the integration of physics and chemistry was extensive, with chemical properties explained as the result of the electronic structure of the atom; Linus Pauling's book on The Nature of the Chemical Bond used the principles of quantum mechanics to deduce bond angles in ever-more complicated molecules. However, though some principles deduced from quantum mechanics were able to predict qualitatively some chemical features for biologically relevant molecules, they were, till the end of the 20th century, more a collection of rules, observations, and recipes than rigorous ab initio quantitative methods.[citation needed]
Diagrammatic representation of some key structural features of DNA
This heuristic approach triumphed in 1953 when James Watson and Francis Crick deduced the double helical structure of DNA by constructing models constrained by and informed by the knowledge of the chemistry of the constituent parts and the X-ray diffraction patterns obtained by Rosalind Franklin.[95] This discovery lead to an explosion of research into the biochemistry of life.
In the same year, the Miller–Urey experiment demonstrated that basic constituents of protein, simple amino acids, could themselves be built up from simpler molecules in a simulation of primordial processes on Earth. Though many questions remain about the true nature of the origin of life, this was the first attempt by chemists to study hypothetical processes in the laboratory under controlled conditions.[citation needed]
In 1983 Kary Mullis devised a method for the in-vitro amplification of DNA, known as the polymerase chain reaction (PCR), which revolutionized the chemical processes used in the laboratory to manipulate it. PCR could be used to synthesize specific pieces of DNA and made possible the sequencing of DNA of organisms, which culminated in the huge human genome project.
An important piece in the double helix puzzle was solved by one of Pauling's students Matthew Meselson and Frank Stahl, the result of their collaboration (Meselson–Stahl experiment) has been called as "the most beautiful experiment in biology".
They used a centrifugation technique that sorted molecules according to differences in weight. Because nitrogen atoms are a component of DNA, they were labelled and therefore tracked in replication in bacteria.
Late 20th century[edit]
Buckminsterfullerene, C60
In 1970, John Pople developed the Gaussian program greatly easing computational chemistry calculations.[96] In 1971, Yves Chauvin offered an explanation of the reaction mechanism of olefin metathesis reactions.[97] In 1975, Karl Barry Sharpless and his group discovered stereoselective oxidation reactions including Sharpless epoxidation,[98][99]Sharpless asymmetric dihydroxylation,[100][101][102] and Sharpless oxyamination.[103][104][105] In 1985, Harold Kroto, Robert Curl and Richard Smalley discovered fullerenes, a class of large carbon molecules superficially resembling the geodesic dome designed by architect R. Buckminster Fuller.[106] In 1991, Sumio Iijima used electron microscopy to discover a type of cylindrical fullerene known as a carbon nanotube, though earlier work had been done in the field as early as 1951. This material is an important component in the field of nanotechnology.[107] In 1994, Robert A. Holton and his group achieved the first total synthesis of Taxol.[108][109][110] In 1995, Eric Cornell and Carl Wieman produced the first Bose–Einstein condensate, a substance that displays quantum mechanical properties on the macroscopic scale.[111]
Mathematics and chemistry[edit]
Classically, before the 20th century, chemistry was defined as the science of the nature of matter and its transformations. It was therefore clearly distinct from physics which was not concerned with such dramatic transformation of matter. Moreover, in contrast to physics, chemistry was not using much of mathematics. Even some were particularly reluctant to use mathematics within chemistry. For example, Auguste Comte wrote in 1830:
Every attempt to employ mathematical methods in the study of chemical questions must be considered profoundly irrational and contrary to the spirit of chemistry.... if mathematical analysis should ever hold a prominent place in chemistry -- an aberration which is happily almost impossible -- it would occasion a rapid and widespread degeneration of that science.
However, in the second part of the 19th century, the situation changed and August Kekulé wrote in 1867:
I rather expect that we shall someday find a mathematico-mechanical explanation for what we now call atoms which will render an account of their properties.
Scope of chemistry[edit]
As understanding of the nature of matter has evolved, so too has the self-understanding of the science of chemistry by its practitioners. This continuing historical process of evaluation includes the categories, terms, aims and scope of chemistry. Additionally, the development of the social institutions and networks which support chemical enquiry are highly significant factors that enable the production, dissemination and application of chemical knowledge. (See Philosophy of chemistry)
Chemical industry[edit]
The later part of the nineteenth century saw a huge increase in the exploitation of petroleum extracted from the earth for the production of a host of chemicals and largely replaced the use of whale oil, coal tar and naval stores used previously. Large-scale production and refinement of petroleum provided feedstocks for liquid fuels such as gasoline and diesel, solvents, lubricants, asphalt, waxes, and for the production of many of the common materials of the modern world, such as synthetic fibers, plastics, paints, detergents, pharmaceuticals, adhesives and ammonia as fertilizer and for other uses. Many of these required new catalysts and the utilization of chemical engineering for their cost-effective production.
In the mid-twentieth century, control of the electronic structure of semiconductor materials was made precise by the creation of large ingots of extremely pure single crystals of silicon and germanium. Accurate control of their chemical composition by doping with other elements made the production of the solid state transistor in 1951 and made possible the production of tiny integrated circuits for use in electronic devices, especially computers.
See also[edit]
Histories and timelines[edit]
Notable chemists[edit]
listed chronologically:
List of chemists
Robert Boyle, 1627–1691
Joseph Black, 1728–1799
Joseph Priestley, 1733–1804
Carl Wilhelm Scheele, 1742–1786
Antoine Lavoisier, 1743–1794
Alessandro Volta, 1745–1827
Jacques Charles, 1746–1823
Claude Louis Berthollet, 1748–1822
Amedeo Avogadro, 1776-1856
Joseph-Louis Gay-Lussac, 1778–1850
Humphry Davy, 1778–1829
Jöns Jacob Berzelius, inventor of modern chemical notation, 1779–1848
Justus von Liebig, 1803–1873
Louis Pasteur, 1822–1895
Stanislao Cannizzaro, 1826–1910
Friedrich August Kekulé von Stradonitz, 1829–1896
Dmitri Mendeleev, 1834–1907
Josiah Willard Gibbs, 1839–1903
J. H. van 't Hoff, 1852–1911
William Ramsay, 1852–1916
Svante Arrhenius, 1859–1927
Walther Nernst, 1864–1941
Marie Curie, 1867–1934
Gilbert N. Lewis, 1875–1946
Otto Hahn, 1879–1968
Irving Langmuir, 1881–1957
Linus Pauling, 1901–1994
Glenn T. Seaborg, 1912–1999
Robert Burns Woodward, 1917-1979
Frederick Sanger, 1918-2013
Geoffrey Wilkinson, 1921-1996
Rudolph A. Marcus, 1923-
George Andrew Olah, 1926-2017
Elias James Corey, 1928-
Akira Suzuki, 1930-
Richard F. Heck, 1931-2015
Harold Kroto, 1939-2016
Jean-Marie Lehn, 1939-
Peter Atkins, 1940-
Barry Sharpless, 1941-
Richard Smalley, 1943–2005
Jean-Pierre Sauvage, 1944-
{[Niels Bohr}}
^Selected Classic Papers from the History of Chemistry
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^Will Durant wrote in The Story of Civilization I: Our Oriental Heritage:
"Something has been said about the chemical excellence of cast iron in ancient India, and about the high industrial development of the Gupta times, when India was looked to, even by Imperial Rome, as the most skilled of the nations in such chemical industries as dyeing, tanning, soap-making, glass and cement... By the sixth century the Hindus were far ahead of Europe in industrial chemistry; they were masters of calcinations, distillation, sublimation, steaming, fixation, the production of light without heat, the mixing of anesthetic and soporific powders, and the preparation of metallic salts, compounds and alloys. The tempering of steel was brought in ancient India to a perfection unknown in Europe till our own times; King Porus is said to have selected, as a specially valuable gift from Alexander, not gold or silver, but thirty pounds of steel. The Moslems took much of this Hindu chemical science and industry to the Near East and Europe; the secret of manufacturing "Damascus" blades, for example, was taken by the Arabs from the Persians, and by the Persians from India."
^B. W. Anderson (1975) The Living World of the Old Testament p. 154, ISBN 0-582-48598-3
^R. F. Tylecote (1992) A History of Metallurgy ISBN 0-901462-88-8
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^ abWill Durant (1935), Our Oriental Heritage:
"Two systems of Hindu thought propound physical theories suggestively similar to those of Greece. Kanada, founder of the Vaisheshika philosophy, held that the world was composed of atoms as many in kind as the various elements. The Jains more nearly approximated to Democritus by teaching that all atoms were of the same kind, producing different effects by diverse modes of combinations. Kanada believed light and heat to be varieties of the same substance; Udayana taught that all heat comes from the sun; and Vachaspati, like Newton, interpreted light as composed of minute particles emitted by substances and striking the eye."
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"To form an idea of the historical place of Jabir's alchemy and to tackle the problem of its sources, it is advisable to compare it with what remains to us of the alchemical literature in the Greek language. One knows in which miserable state this literature reached us. Collected by Byzantine scientists from the tenth century, the corpus of the Greek alchemists is a cluster of incoherent fragments, going back to all the times since the third century until the end of the Middle Ages."
"The efforts of Berthelot and Ruelle to put a little order in this mass of literature led only to poor results, and the later researchers, among them in particular Mrs. Hammer-Jensen, Tannery, Lagercrantz, von Lippmann, Reitzenstein, Ruska, Bidez, Festugiere and others, could make clear only few points of detail…
The study of the Greek alchemists is not very encouraging. An even surface examination of the Greek texts shows that a very small part only was organized according to true experiments of laboratory: even the supposedly technical writings, in the state where we find them today, are unintelligible nonsense which refuses any interpretation.
It is different with Jabir's alchemy. The relatively clear description of the processes and the alchemical apparatuses, the methodical classification of the substances, mark an experimental spirit which is extremely far away from the weird and odd esotericism of the Greek texts. The theory on which Jabir supports his operations is one of clearness and of an impressive unity. More than with the other Arab authors, one notes with him a balance between theoretical teaching and practical teaching, between the `ilm and the `amal. In vain one would seek in the Greek texts a work as systematic as that which is presented for example in the Book of Seventy."
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^First total synthesis of taxol 1. Functionalization of the B ring Robert A. Holton, Carmen Somoza, Hyeong Baik Kim, Feng Liang, Ronald J. Biediger, P. Douglas Boatman, Mitsuru Shindo, Chase C. Smith, Soekchan Kim, et al.; J. Am. Chem. Soc .; 1994; 116(4); 1597–1598. DOI Abstract
^First total synthesis of taxol. 2. Completion of the C and D rings Robert A. Holton, Hyeong Baik Kim, Carmen Somoza, Feng Liang, Ronald J. Biediger, P. Douglas Boatman, Mitsuru Shindo, Chase C. Smith, Soekchan Kim, and et al. J. Am. Chem. Soc .; 1994; 116(4) pp 1599–1600 DOI Abstract
^A synthesis of taxusin Robert A. Holton, R. R. Juo, Hyeong B. Kim, Andrew D. Williams, Shinya Harusawa, Richard E. Lowenthal, Sadamu Yogai J. Am. Chem. Soc .; 1988; 110(19); 6558–6560. Abstract
^"Cornell and Wieman Share 2001 Nobel Prize in Physics". NIST News Release. National Institute of Standards and Technology. 2001. Archived from the original on 2007-06-10. Retrieved 2007-03-27.
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