Hydrometer

Densimeter or hydrometer is bulb-shaped flask with a projecting stem for measuring the density. Hydrometers are used for indicative and operational density measurements of liquids. Each densimeter has a certain range for which it is manufactured.

The model shows hydrometer for water, which floats at a certain depth after immersion into a liquid. Thanks to Archimedes' law the depth of immersion of the bulb and stem depends on the liquid density.

When placed in a liquid with density like water, it is showing the density at a scale that is part of the stem. When immersed in a substance with a significantly greater density, it will be floating on its surface. When immersed in a substance with a significantly lower density, it will sink to the bottom. The scale is calibrated in SI units - kilogram per cubic meter (kg/m³).