Emil Wohlwill's “Entdeckung des Isomorphismus”: A Nineteenth-Century “Material Biography” of Crystallography

Abstract

Eilhard Mitscherlich's experimental work on isomorphism in the crystallisation of many inorganic compounds was regarded by Emil Wohlwill (1835–1912) as a milestone in the history of the atomic–molecular theory. Despite his positivist account, Wohlwill's 1866 survey was primarily concerned with the material conditions that shaped Mitscherlich's theoretical assumptions on iso- and polymorphic crystallisation, narrowing the range of possible alternative models. Following an account of Wohlwill's exposition, and a discussion of his historiographic views, the paper shows how, from a historico-epistemological perspective, technical improvements in crystallography (an emerging branch of early-nineteenth-century mineralogy) were deeply entangled with a new interest in crystal formation as a cutting-edge research field of inorganic chemistry. This had fundamental implications for the development of atomic and molecular theory.