The Baumé scale was created by French chemist Antoine Baumé for use in marking hydrometers, which measure the density of liquids. For water and liquids heavier than water, zero degrees Baumé corresponds to a specific density of 1.000 (the density of water at 4 degrees Celsius). For liquids lighter than water, zero degrees Baumé corresponds to the density of a 10% sodium chloride solution. You can convert between degrees Baumé and the more commonly used measure of specific gravity using a few simple formulas.
Things You'll Need
 Hydrometer
Calculating Baumé Degrees from Specific Gravity

Heat or cool the solution to approximately room temperature (68 degrees Fahrenheit, 20 degrees Celsius).

Measure the specific gravity of your solution using a hydrometer. If the liquid is less dense than water, divide 140 by the specific gravity. If the liquid is water or a denser liquid, divide 145 by the specific gravity.

Subtract 130 from the result of Step 2 if the liquid is less dense than water. Subtract the result of Step 2 from 145 if the liquid is water or a denser liquid.
Calculating Specific Gravity from Baumé Degrees

Heat or cool the solution to approximately room temperature (68 degrees Fahrenheit, 20 degrees Celsius).

Measure the degrees Baumé of your solution using your hydrometer. If the liquid in your solution is less dense than water, add 130 to the degree measure. If the liquid is water or a denser liquid, subtract the degree measure from 145.

Divide 140 by the result of Step 2 if the liquid is less dense than water. Divide 145 by the result of Step 2 if the liquid or a denser liquid. The answer is the specific gravity of your solution.
References
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