Anil Gomes at The Guardian:
Why do some things combine and others separate? Add nitric acid to gold, and nothing happens. Pour on aqua regia, a mixture of nitric and hydrochloric acids, and the gold dissolves. The chemical doctrine of affinity emerged as a way to explain these reactions. In his 1809 novel Elective Affinities, Johann Wolfgang Goethe applied the idea to human relationships. Charlotte and Edward may form a stable union but if Edward has an affinity with young Ottilie – ah, well, then all bets are off.
What is an affinity? A little like a crush, I suppose, at least at the beginning. And sometimes just as fleeting. But sometimes more stable, more serious, and more revealing of our ways of engaging with things. Brian Dillon’s writings have always been marked by affinities – for artworks, for writers, even for particular sentences.
more here.