By looking at the fierce debates in the city of Carlsbad in Bohemia around the fabrication of medical salt by a local doctor, David Becher, from 1763 to 1784, the paper examines the interactions between different spheres or levels of circulation of knowledge in the Habsburg Empire. The dispute crystallized around the definition of the product, about its medical qualities and its relation with the water of the local mineral spring. The city's inhabitants contested the vision of the medical experts, fearing that the extraction of the medical salt from the spring water and its sale outside the town would have a negative effect on the number of visitors to the spa. Their vision implied a more or less ‘popularized’ form of alchemical thinking as it identified the mineral water with the extracted ‘salt’, conceived as the ‘essence’ of the water, produced by evaporation. The Carlsbad salt dispute highlights the complex interactions among the different networks in which knowledge circulated through the Habsburg Empire in the eighteenth century. The different actors relied on specific networks with different logics of discourse and different modes of circulation. In each case the relation between the local, the regional and the imperial had to be negotiated. The paper thus sketches out the different geographies of knowledge in the Habsburg Empire but also its localization in and around Carlsbad.