Baumé scale

Conversions

The relationship between specific gravity (s.g.; i.e., water-specific gravity, the density relative to water) and degrees Baumé is a function of the temperature. Different versions of the scale may use different reference temperatures. Different conversions formulae can therefore be found in various handbooks.

As an example, a 2008 handbook states the conversions between specific gravity and degrees Baumé at a temperature of 60 °F (16 °C):

${\displaystyle \begin{array}{cc}\mathrm{d}\mathrm{e}\mathrm{g}\mathrm{r}\mathrm{e}\mathrm{e}\mathrm{s}\mathrm{B}\mathrm{a}\mathrm{u}\mathrm{m}\acute{\mathrm{e}}& =\{\begin{array}{ll}{\displaystyle 145\left(1-\frac{1}{\text{s.g.}}\right)}& \text{for density greater than water}\\ {\displaystyle \frac{140}{\text{s.g.}}-130}& \text{for density lesser than water}\end{array}\\ \text{s.g.}& =\{\begin{array}{ll}{\displaystyle \frac{145}{145-\text{degrees Baum}\acute{\mathrm{e}}}}& \text{for density greater than water}\\ {\displaystyle \frac{140}{130+\text{degrees Baum}\acute{\mathrm{e}}}}& \text{for density lesser than water}\end{array}\end{array}}$

The numerator in the specific gravity calculation is commonly known as the "modulus".

An older handbook gives the following formulae (no reference temperature being mentioned):

${\displaystyle \text{s.g.}=\{\begin{array}{ll}{\displaystyle \frac{144}{144-\text{degrees Baum}\acute{\mathrm{e}}}}& \text{for density greater than water}\\ {\displaystyle \frac{144}{134+\text{degrees Baum}\acute{\mathrm{e}}}}& \text{for density lesser than water}\end{array}}$

Other scales

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.

Use

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. Today the Baumé scale is still used in various industries such as sugar beet processing, ophthalmics, starch industry, winemaking, industrial water treatment, metal finishing, and printed circuit board (PCB) fabrication. It is also used for caustic in refining process.