Baumé scale
The Baumé scale is a hydrometer scale developed by French pharmacist Antoine Baumé in 1768 to measure density of various liquids. Notated variously as: degrees Baume, degrees Baumé; B°, Be°, Bé°, Baume.
At 20 °C, the relationship between specific gravity (s.g.) and degrees Baumé is:
- For liquids heavier than water: s.g. = 145 ÷ (145 - degrees Baumé)
- For liquids lighter than water: s.g. = 140 ÷ (degrees Baumé + 130)
An older version of the scale for liquids heavier than water, at a reference temperature of 15.5 °C, uses 144.32 rather than 145.
Originally the scale was based on salinity of water and brine. Because of vague instructions or errors in translation a large margin of error was introduced when the scale was adopted. The API gravity scale is a result of adapting to the subsequent errors from the Baumé scale. The Baumé scale is related to the Balling, Brix, Plato and 'specific gravity times 1000' scales. The Baumé scale is sometimes used by US brewers.