The Baumé scale is a pair of hydrometer scales 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. One scale measures the density of liquids heavier than water and the other, liquids lighter than water.

At 20 °C, the relationship between specific gravity (s.g.) (relative density) 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.

Baumé degrees (heavy) originally represented the percent by mass of sodium chloride in water at 60 degrees Fahrenheit (15.5 °C). Baumé degrees (light) was calibrated with 0°Bé (light) being the density of 10% NaCl in water by mass and 10°Bé (light) set to the density of water. 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.

In the sugar beet processing industry, Baume was traditionally used for the measurement of milk of lime, a calcium oxide/calcium hydroxide/sugar solution mixture. It is also used to measure sugar levels in winemaking.

References

• Boulton, Roger; Vernon Singleton, Linda Bisson, Ralph Kunkee (1996). Principles and Practices of Winemaking. Chapman & Hall. ISBN 0-412-06411-1