Editing Chemical affinity (section)

== History ==

===Early theories===
The idea of ''affinity'' is extremely old.  Many attempts have been made at identifying its origins.<ref name="Levere" />  The majority of such attempts, however, except in a general manner, end in futility since "affinities" lie at the basis of all [[Magic (paranormal)|magic]], thereby pre-dating [[science]].<ref>Malthauf, R. P. (1966). The Origins of Chemistry. Pg. 299. London.</ref> [[Physical chemistry]], however, was one of the first branches of science to study and formulate a "theory of affinity".  The name ''affinitas'' was first used in the sense of chemical relation by German philosopher [[Albertus Magnus]] near the year 1250.  Later, those as [[Robert Boyle]], [[John Mayow]], [[Johann Glauber]], [[Isaac Newton]], and [[Georg Stahl]] put forward ideas on elective affinity in attempts to explain how [[heat]] is evolved during [[combustion reactions]].<ref>Partington, J.R. (1937). ''A Short History of Chemistry.'' New York: Dover Publications, Inc. {{ISBN|0-486-65977-1}}</ref>

The term ''affinity'' has been used figuratively since c.&nbsp;1600 in discussions of structural relationships in chemistry, [[philology]], etc., and reference to "natural attraction" is from 1616. "Chemical affinity", historically, has referred to the "[[electromagnetic force|force]]" that causes [[chemical reaction]]s.<ref>[[Thomas Thomson (chemist)|Thomas Thomson]]. (1831). ''A System of Chemistry'', vol. 1. p.31 (chemical affinity is described as an "unknown force"). 7th ed., 2 vols.</ref> as well as, more generally, and earlier, the ″tendency to combine″ of any pair of substances. The broad definition, used generally throughout history, is that chemical affinity is that whereby substances enter into or resist decomposition.<ref name="Levere" >{{cite book | last = Levere | first = Trevor, H. | title = Affinity and Matter – Elements of Chemical Philosophy 1800-1865 | publisher = Gordon and Breach Science Publishers | year = 1971 | isbn = 2-88124-583-8}}</ref>
 
The modern term chemical affinity is a somewhat modified variation of its eighteenth-century precursor "elective affinity" or elective attractions, a term that was used by the 18th century chemistry lecturer [[William Cullen]].<ref>See Arthur Donovan, Philosophical Chemistry in the Scottish Enlightenment, Edinburgh, 1975</ref> Whether Cullen coined the phrase is not clear, but his usage seems to predate most others, although it rapidly became widespread across Europe, and was used in particular by the Swedish chemist [[Torbern Olof Bergman]] throughout his book {{lang|la|De attractionibus electivis}} (1775).  Affinity theories were used in one way or another by most chemists from around the middle of the 18th century into the 19th century to explain and organise the different combinations into which substances could enter and from which they could be retrieved.<ref>{{cite journal|last=Eddy|first=Matthew Daniel|title=Elements, Principles and the Narrative of Affinity|journal=Foundations of Chemistry|date=2004|volume=6|issue=2|pages=161–175|doi=10.1023/B:FOCH.0000035061.02831.45|s2cid=143754994|url=https://www.academia.edu/3770609}}</ref><ref>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</ref> [[Antoine Lavoisier]], in his famed 1789 ''[[Traité Élémentaire de Chimie]] (Elements of Chemistry)'', refers to Bergman's work and discusses the concept of elective affinities or attractions.

According to chemistry historian Henry Leicester, the influential 1923 textbook ''Thermodynamics and the Free Energy of Chemical Reactions'' by [[Gilbert N. Lewis]] and [[Merle Randall]] led to the replacement of the term "affinity" by the term "[[thermodynamic free energy|free energy]]" in much of the English-speaking world.

According to Prigogine,<ref>I.Prigogine. (1980). ''From being to becoming. Time and Complexity in the Physical Sciences''. San Francisco: W.H.Freeman and Co</ref> the term was introduced and developed by [[Théophile de Donder]].<ref>de Donder, T. (1936). ''L'affinité''. Ed. Pierre Van Rysselberghe. Paris: Gauthier-Villars</ref>

[[Johann Wolfgang von Goethe]] used the concept in his novel ''[[Elective Affinities]]'' (1809).

=== Visual representations ===
[[file:Affinity-table.jpg|thumb|500px|Geoffroy's ''Affinity Table'' (1718): At the head of the column is a substance with which all the substances below can combine, where each column below the header is ranked by degrees of "affinity"]]

The affinity concept was very closely linked to the visual representation of substances on a table. The first-ever ''affinity table'', which was based on [[displacement reaction]]s, was published in 1718 by the French chemist [[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 of Sciences]] in 1718 and 1720.

During the 18th century many versions of the table were proposed with leading chemists like Torbern Bergman in Sweden and Joseph Black in Scotland adapting it to accommodate new chemical discoveries.  All the tables were essentially lists, prepared by collating observations on the actions of substances one upon another, showing the varying degrees of affinity exhibited by analogous bodies for different [[reagent]]s.

Crucially, the table was the central graphic tool used to teach chemistry to students and its visual arrangement was often combined with other kinds diagrams.  Joseph Black, for example, used the table in combination with chiastic and circlet diagrams to visualise the core principles of chemical affinity.<ref>{{cite journal|last1=Eddy|first1=Matthew Daniel|title=How to See a Diagram: A Visual Anthropology of Chemical Affinity|journal=Osiris|date=2014|pages=178–196|doi=10.1086/678093|url=https://www.academia.edu/4588508|volume=29|pmid=26103754|s2cid=20432223 }}</ref>  Affinity tables were used throughout Europe until the early 19th century when they were displaced by affinity concepts introduced by [[Claude Louis Berthollet|Claude Berthollet]].