'Who can tell me what potable water means?' The assessment of water quality in debates over hydraulic infrastructure in nineteenth-century Italy.

How water is perceived and represented has an impact on the relationships between a given society and its water infrastructure. Historians have identified a shift in the perception of water during the nineteenth century, which was connected to the development of chemistry. From an understanding based in Hippocratic medicine and natural history that treated it as an infinite variety of substances, water eventually became understood as a simple compound consisting of oxygen and hydrogen. This resulted in the abstraction of water from its social and environmental contexts, with consequences for the way water was managed. This article aims to demonstrate that such a view gives a mistaken intellectual coherence to a fragmented and conflicted process, which involved continuities, an adaptation of old frameworks to new social priorities, and fine changes in scientific thinking and practices. This paper examines the scientific and political debates concerning water infrastructure, surveys and analyses on water quality, medical reports and political measures in nineteenth-century Italy. Ultimately, the reduction of 'waters' to 'water' in Italy was more about determining who had the authority to assess water quality in the process of creating and stabilizing new power relations between the public and the private spheres than about the abstraction of water from its social and environmental contexts.