The hydrometer is a measurement device to determine the mass density of liquids. It was developed in the early 19th century and put to use by the British Customs Services to measure the alcoholic strength.

The Hydrometer in our HistoLab is an original, the inscription on the box reads: "Sikes's Hydrometer, John McGlashan & Co, Albany Works, Glascow"

Martin, T. (2007). Hydrometry and slide rules in brewing and distilling. Journal of the Brewery History Society, 124/5, 14-37.