"There is currently a widespread ‘master narrative’ of Newton’s alchemy, though one with which I disagree. The major scholars of the subject at that time, especially Westfall, argued that the impact of alchemy on Newton’s more mainstream science lay in his emphasis on invisible forces that could act over a considerable space, such as gravitational attraction. The reason why a lodestone attracted iron at a distance was because of a hidden sympathy between the two, like the occult sympathies governing magical phenomena. Couldn’t this sort of explanation have stimulated Newton to think of gravity in terms of an immaterial attraction? And wasn’t alchemy based on the idea that some materials react with others because of a similar principle of affinity? Thus the idea that Newton’s involvement with alchemy was part of a quest to understand gravitational attraction was born. Contemporary sources ranging from popular outlets such as Wikipedia to serious scholarly monographs echo this theme.
In reality, however, there is little to no evidence to support the view that alchemy led to Newton’s belief in action at a distance. Instead, Newton’s alchemical research had a serious impact on his optics, as I explain in Newton the Alchemist, and it also contributed to his work on the short-range forces operating in chemical reactions, which the eighteenth century called ‘elective affinity.’ Newton came to be seen as the patron saint of elective affinity, thanks to a section of his famous 1717 Opticks that dealt with the theme of chemical attraction."