Early Ideas of Chemical Affinity

The roots of both chemical thermodynamics and contemporary kinetics both lie in the eighteenth-century ideas of chemical "affinity" and "force," transformed into nineteenth-century conceptions of "work" and "energy." Berthollet identified the fundamental difficulty for eighteenth-century theories of affinity in a critique that applied equally to early-nineteenth-century theories of electrochemical dualism. In "Recherches sur les lois de l affinite" (1799), Berthollet wrote,... 

Early ideas of chemical kinetics were extremely vague and based on an anthropomorphic view of matter and on the equally vague idea of affinity. Therefore, within the Anthropomorphic Model, rate was synonymous with readiness for a transformation to occur. 

The observation that certain elements prefer to combine with specific kinds of elements prompted early chemists to classify the elements in tables of chemical affinity. Later these tables would lead, somewhat indirectly, to the discovery of the periodic system, perhaps the biggest idea in the whole of chemistry. Indeed, periodic tables arose partly through the attempts by Dimitri Mendeleev and numerous others to make sense of the way in which particular elements enter into chemical bonding. 

The contribution of Bergman to the knowledge of carbonic acid or aerial acid will be alluded to in connection with the development of Pneumatic Chemistry, and his extensive work on Chemical Affinity will be referred to in connection with the history of early ideas on that subject. 

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