Areometer, also called hydrometer or baumè, is an instrument used for measuring the density of liquids based on the concept of buoyancy in tannery.
They are typically calibrated and graduated with one or more scales such as specific gravity.

Range available:
0 – 10;
0 – 30;
0 – 50;
0 – 70;

The hydrometer consists of a sealed hollow glass tube with a wider bottom portion for buoyancy, a ballast such as lead or mercury for stability, and a narrow stem with graduations for measuring.
The liquid to test is poured into a tall container, often a graduated cylinder, and the hydrometer is gently lowered into the liquid until it floats freely.
The point at which the surface of the liquid touches the stem of the hydrometer correlates to relative density. Hydrometers can contain any number of scales along the stem corresponding to properties correlating to the density.