Alexandru Manafu (Paris) gives a talk at the MCMP conference "Reduction and Emergence in the Sciences" (14-16 November, 2013) titled "Inter-theoretic relations: The Brønsted Lowry theory of acids and microphysics". Abstract: This paper examines the relations between the Brønsted-Lowry theory of acids and the underlying microphysical theories. It argues that these relations are complex and somewhat messy. They do not lend wholesale support to any of the philosophical theories of reduction or emergence. However, they do support particular aspects from both sides. The paper fleshes out what these aspects are, and draws some general philosophical lessons. One of these is that acidity is a sui generis chemical property, which is made possible by processes at the lower level, but which can be adequately defined only at a higher level.