Note 14 — Chapter II · Establishment and Development of the Idea of Chemical Affinity.

See Dumas, Leçons de Phil. Chim. p. 364. Rees’ Cyclopædia, Art. Chemistry. In the passage of Boerhaave to which I refer above, affinitas is rather opposed to, than identified with, chemical combination. When, he says, the parts of the body to be dissolved are dissevered by the solvent, why do they remain united to the particles of the solvent, and why do not rather both the particles of the solvent and of the dissolved body collect into homogeneous bodies by their affinity? ‘denuo se affinitate suæ naturæ colligant in corpora homogenea?‘ And the answer is, because they possess another force which counteracts this affinity of homogeneous particles, and makes compounds of different elements. Affinity, in chemistry, now means the tendency of different kinds of matter to unite: but it appears, as I have said, to have acquired this sense since Boerhaave’s time.