On Air and Chemistry in the Encyclopédie

The Encyclopédie article Air is almost silent on the recent remarkable chemical thinking on air, whose component parts were said to be totally without elasticity and subject to the laws of chemical affinity like those of any other substance. Thus, as Venel insisted in his article Chymie, the air must be considered in two ways by natural philosophers: either as a constituent part of bodies possessing chemical properties and as a mass with physical properties, or as fixed and expanding. This dual approach to the air corresponds to the distinction made by Venel between chemistry and (ordinary) physics as to the size of their objects of study, but is also intended to emphasize both the specificity and the relevance of chemical method which can also ‘lead to genius’. Thus the question of the nature of the air, common to the two disciplines, illustrated how chemistry can correct the ‘mistakes’ which according to Venel have disfigured physics. Turgot’s article Expansibilité can perhaps also be seen as a rewriting Air following the contributions of chemistry, as any body is potential air.