The Baumé scale is a pair of hydrometer scales developed by French pharmacist Antoine Baumé in 1768 to measure density of various liquids.
Baumé degrees (heavy) originally represented the percent by mass of sodium chloride in water at 60 °F (16 °C).
As an example, a 2008 handbook[1] states the conversions between specific gravity and degrees Baumé at a temperature of 60 °F (16 °C):[a] The numerator in the specific gravity calculation is commonly known as the "modulus".
An older handbook[4] gives the following formulae (no reference temperature being mentioned):[b] Because of vague instructions or errors in translation a large margin of error was introduced when the scale was adopted.
[remove or clarification needed] Before standardization on specific gravity around the time of World War II the Baumé scale was generally used in industrial chemistry and pharmacology for the measurement of density of liquids.