Hydromètre

A hydrometer measures the density or specific gravity of liquids. This works according to static buoyancy. Static buoyancy is a force on a body in liquid or gases that opposes gravity. This is also how hot air balloons, for example, rise in the air. In a hydrometer, a body immersed in liquid is lowered until the weight force of the displaced liquid equals the weight force of the immersed body. Provided the density of the liquid is low, a body of the same weight continues to be immersed in it. In practice, the liquid is poured into a measuring vessel defined from glass. Then a hydrometer is selected that corresponds to the measuring range of the approximate density of the liquid. This is immersed in the liquid. The value (density) of the immersed hydrometer can then be read from the surface of the liquid.