Chemical affinity 1

Chemical affinityIn chemical physics and physical chemistry, chemical affinity is the electronic property by which dissimilarchemical species are capable of forming chemical compounds.[1] Chemical affinity can also refer to the tendency ofan atom or compound to combine by chemical reaction with atoms or compounds of unlike composition.

Modern conceptionsIn modern terms, we relate affinity to the phenomenon whereby certain atoms or molecules have the tendency toaggregate or bond. For example, in the 1919 book Chemistry of Human Life physician George W. Carey states that,"Health depends on a proper amount of iron phosphate Fe3(PO4)2 in the blood, for the molecules of this salt havechemical affinity for oxygen and carry it to all parts of the organism." In this antiquated context, chemical affinity issometimes found synonymous with the term "magnetic attraction". Many writings, up until about 1925, also refer toa "law of chemical affinity".Ilya Prigogine summarized the concept of affinity, saying, "All chemical reactions drive the system to a state ofequilibrium in which the affinities of the reactions vanish."

ThermodynamicsThe present IUPAC definition is that affinity A is the negative partial derivative of Gibbs free energy G with respectto extent of reaction ξ at constant pressure and temperature.[2] That is,

It follows that affinity is positive for spontaneous reactions.In 1923, the Belgian mathematician and physicist Théophile de Donder derived a relation between affinity and theGibbs free energy of a chemical reaction. Through a series of derivations, de Donder showed that if we consider amixture of chemical species with the possibility of chemical reaction, it can be proven that the following relationholds:

With the writings of Théophile de Donder as precedent, Ilya Prigogine and Defay in Chemical Thermodynamics(1954) defined chemical affinity in terms of the uncompensated heat of reaction Q' the reaction progress variable orreaction extent ξ; as the ratio of their infinitesimal increments:

This definition is useful for quantifying the factors responsible both for the state of equilibrium systems (where A =0), and for changes of state of non-equilibrium systems (where A ≠ 0).

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History"Chemical affinity", historically, has referred to the "force" that causes chemical reactions.[3] as well as, moregenerally, and earlier, the ″tendency to combine″ of any pair of substances. The broad definition, used generallythroughout history, is that chemical affinity is that whereby substances enter into or resist decomposition.[4]

The term affinity has been used figuratively since c. 1600 in discussions of structural relationships in chemistry,philology, etc., and reference to "natural attraction" is from 1616.The idea of affinity is extremely old. Many attempts have been made at identifying its origins.[4] The majority ofsuch attempts, however, except in a general manner, end in futility since "affinities" lie at the basis of all magic,thereby pre-dating science.[5] Physical chemistry, however, was one of the first branches of science to study andformulate a "theory of affinity". The name affinitas was first used in the sense of chemical relation by Germanphilosopher Albertus Magnus near the year 1250. Later, those as Robert Boyle, John Mayow, Johann Glauber, IsaacNewton, and Georg Stahl put forward ideas on elective affinity in attempts to explain how heat is evolved duringcombustion reactions.[6]

The modern term chemical affinity is a somewhat modified variation of its eighteenth-century precursor "electiveaffinity" or elective attractions, a term that was used by the 18th century chemistry lecturer William Cullen.[7]

Whether Cullen coined the phrase is not clear, but his usage seems to predate most others, although it rapidly becamewidespread across Europe, and was used in particular by the Swedish chemist Torbern Olof Bergman throughout hisbook De attractionibus electivis (1775). Affinity theories were used in one way or another by most chemists fromaround the middle of the 18th century into the 19th century to explain and organise the different combinations intowhich substances could enter and from which they could be retrieved.[8] Antoine Lavoisier, in his famed 1789 TraitéÉlémentaire de Chimie (Elements of Chemistry), refers to Bergman’s work and discusses the concept of electiveaffinities or attractions.According to chemistry historian Henry Leicester, the influential 1923 textbook Thermodynamics and the FreeEnergy of Chemical Reactions by Gilbert N. Lewis and Merle Randall led to the replacement of the term "affinity"by the term "free energy" in much of the English-speaking world.According to Prigogine,[9] the term was introduced and developed by Théophile de Donder.[10]

Goethe used the concept in his novel Elective Affinities, (1809)

Chemical affinity 3

Geoffroy's 1718 affinity tableThe first-ever affinity table, which was based on displacement reactions, was published in 1718 by the Frenchchemist Étienne François Geoffroy. Geoffroy's name is best known in connection with these tables of "affinities"(tables des rapports), which were first presented to the French Academy in 1718 and 1720, as shown below:

Geoffroy's Affinity Table (1718): At the head of the column is a substance with which all the substances below can combine, where eachcolumn below the header is ranked by degrees of "affinity".

These were lists, prepared by collating observations on the actions of substances one upon another, showing thevarying degrees of affinity exhibited by analogous bodies for different reagents, and they retained their vogue for therest of the century, until displaced by the profounder conceptions introduced by Claude Berthollet.

References[1] Chemical Affinity (http:/ / www. 1911encyclopedia. org/ Chemical_affinity) - Britannica 1911[2] IUPAC Green Book and Gold Book in .pdf (http:/ / www. IUPAC. org)[3] Thomas Thomson. (1831). A System of Chemistry, vol. 1. p.31 (chemical affinity is described as an "unknown force"). 7th ed., 2 vols.[4] Levere, Trevor, H. (1971). Affinity and Matter – Elements of Chemical Philosophy 1800-1865. Gordon and Breach Science Publishers.

ISBN 2-88124-583-8.[5][5] Malthauf, R. P. (1966). The Origins of Chemistry. Pg. 299. London.[6] Partington, J.R. (1937). A Short History of Chemistry. New York: Dover Publications, Inc. ISBN 0-486-65977-1[7][7] See Arthur Donovan, Philosophical Chemistry in the Scottish Enlightenment, Edinburgh, 1975[8][8] On the variety of affinity theories, see Georgette Taylor, Variations on a Theme; Patterns of Congruence and Divergence among 18th Century

Affinity Theories, VDM Verlag Dr Muller Aktiengesellschaft, 2008[9] I.Prigogine. (1980). From being to becoming. Time and Complexity in the Physical Sciences. San Fracisco: W.H.Freeman and Co[10] de Donder, T. (1936). L'affinité. Ed. Pierre Van Rysselberghe. Paris: Gauthier-Villars

Chemical affinity 4

Notes• This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911).

Encyclopædia Britannica (11th ed.). Cambridge University Press.

External links• William Whewell. "Establishment and Development of the Idea of Chemical Affinity" (http:/ / books. google.

com/ books?id=HGJxo1tmUP0C& lpg=PA15& ots=3Llmn3GJZr& dq=whewell "chemical affinity"&pg=PA15#v=onepage& q& f=false). History of Scientific Ideas. 2:15ff.

• Chemical Affinity and Absolute Zero (http:/ / nobelprize. org/ nobel_prizes/ chemistry/ laureates/ 1920/ press.html) - 1920 Nobel Prize in Chemistry Presentation Speech by Gerard de Geer

• Elements, Principles and the Narrative of Affinity (http:/ / 72. 14. 203. 104/search?q=cache:V8hWHBu0njMJ:eprints. dur. ac. uk/ archive/ 00000085/ 01/ Eddy_elements. rtf+ Louis+Lemery& hl=en& ct=clnk& cd=10& gl=us) – Essay Review

Étienne François Geoffroy

Étienne François Geoffroy

Étienne François Geoffroy (February 13, 1672 –January 6, 1731) was a French physician andchemist, best known for his 1718 affinity tables. Hefirst contemplated a career as an apothecary, but thendecided to practice medicine. He is sometimesknown as Geoffroy the Elder.

Biography

Geoffroy was born in Paris. After studying atMontpellier he accompanied Marshal Tallard on hisembassy to London in 1698 and thence travelled tothe Netherlands and Italy. Returning to Paris hebecame professor of chemistry at the Jardin du Roiand of pharmacy and medicine at the Collège Royal,and dean of the faculty of medicine. He died in Parison 6 January 1731.

His brother Claude Joseph, known as Geoffroy theyounger, was also a chemist.

Works

His name is best known in connection with his tablesof "affinities" (tables des rapports), which hepresented to the French Academy in 1718 and 1720.

Étienne François Geoffroy 5

Geoffroy's Affinity Table (1718): At the head of the column is a substance with which all the substances below can combine.

These were lists, prepared by collating observations on the actions of substances one upon another, showing thevarying degrees of affinity exhibited by analogous bodies for different reagents, and they retained their vogue for therest of the century, until displaced by the profounder conceptions introduced by CL Berthollet.Another of his papers dealt with the delusions of the philosopher's stone, but nevertheless he believed that iron couldbe artificially formed in the combustion of vegetable matter. His Tractatus de materia medico, publishedposthumously in 1741, was long celebrated.

References• This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911).

Encyclopædia Britannica (11th ed.). Cambridge University Press.

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Article Sources and ContributorsChemical affinity  Source: http://en.wikipedia.org/w/index.php?oldid=537992981  Contributors: 90fast, Ale2006, Alvestrand, Andres, Anyep, Biopresto, Burubuz, Cardamon, Ccac5161, Chaos,Conversion script, Ctdunstan, Damian Yerrick, Davidiad, Dlituiev, Ellmist, Elvim, FatFordyce, Felix Wan, Hoffmeier, JWSchmidt, JaGa, Jamelan, Kupirijo, Lemchesvej, Leutha, Marj Tiefert,Maschen, Mccaskey, Michael Hardy, Mr Bound, RedWolf, Rhadamante, Rich Farmbrough, Sadi Carnot, Stone, StradivariusTV, Tassedethe, Template namespace initialisation script, TheRationalist, Xezbeth, علی ویکی, มือใหม่, 15 anonymous edits

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Image Sources, Licenses and ContributorsImage:Affinity-table.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Affinity-table.jpg  License: Public Domain  Contributors: E.R. GeoffroyImage:Etienne-Francois Geoffroy.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Etienne-Francois_Geoffroy.jpg  License: Public Domain  Contributors: L. Surugue

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