Geoffroy, Etienne-Francois

The term "affinity" has its roots in very old ideas to the effect that like attracts like and that bodies combine with other bodies because of mutual affection or affinitas. This meaning is employed in Etienne Francois Geoffroy s Table des differents rapports observes entre differentes substances (1718) for replacement reactions.28 However, in the middle of the eighteenth century, Boerhaave spoke of the affinity of a substance for others unlike it, giving the word "affinity" a new meaning. Boerhaave interpreted Geoffroy s table as a representation of Newtonian-type forces of gravitational attraction or electrical attraction and repulsion.29... 

The attention of many chemists from about this time was devoted to ascertaining the laws and generalizations of chemical attraction or affinity. The first serious attempt to systematize the relative affinities between substances was that of Etienne Francois Geoffroy (1672-1721), Professor of Chemistry at the Jardin du Roi from 1712 to 1731. He presented a memoir to the Academy of Sciences at Paris in 1718, entitled Table of the different Connections rapports ) observed in Chemistry between different Substances. In this he lays down as his fundamental law Whenever two substances having some tendency to combine with each other are found combined and there enters a third which has more affinity with one of the two, it unites with that one, setting the other free. ... 

It is therefore obvious that the chemistry of pure substances can be defined only on the basis of its objects of inquiry. But it should be noted that in the eighteenth century it were the chemists themselves who distinguished these objects of inquiry from other ones in their practices of classification. We argue that their distinction corresponds exactly with the boundaries of objects of inquiry in the tableau of the Meth-ode. The question raised above was whether the authors of the Methode were the first to see an inner bond among the many different activities with pure chemical substances scattered through all domains of chemistry, or whether their distinction of the particular sphere of the chemistry of pure substances followed a tradition established earlier. Fortunately, there exists unmistakable evidence for such a tradition. The famous tables of chemical affinities testify unambiguously to the existence of this particular chemical practice. The first of these tables was the Table des differents rapports constmctedby Etienne Francois Geoffroy (1672-1731), published in 1718. We can thus even determine when the distinction of operations with pure chemical substances first became manifest, namely approximately seventy years before the Tableau of 1787. 

FIGURE 175. Top half of Etienne Geoffroy s (Jacques Francois Demachy, Paris, 1781). 

---