I argue in the paper that classical chemistry is a science predominantly concerned with material substances, both useful materials and pure chemical substances restricted to scientific laboratory studies. The central epistemological and methodological status of material substances corresponds with the material productivity of classical chemistry and its way of producing experimental traces. I further argue that chemist’s ‘pure substances’ have a history, conceptually and materially, and I follow their conceptual history from the Paracelsian concept of purity to the modern concept (...) of pure stoichiometric compounds. The history of the concept of ‘pure substances’ shows that modern chemists’ concept of purity abstracted from usefulness rather than being opposed to it. Thus modern chemists’ interest in pure chemical substances does not presuppose a concept of pure science. (shrink)