What device is used to measure specific gravity?

The device used to measure specific gravity is a hydrometer. A hydrometer operates on the principle of buoyancy, which is based on Archimedes' principle. It consists of a sealed glass tube with a bulb at the bottom that is weighted, enabling it to float in a liquid. When the hydrometer is placed in a liquid, it displaces a volume of liquid equal to the weight of the hydrometer. The level to which the hydrometer sinks indicates the specific gravity of the liquid compared to water.

Specific gravity is defined as the ratio of the density of a substance to the density of a reference substance, typically water for liquids. Because the hydrometer is calibrated to provide readings directly related to specific gravity, it serves as a simple and effective tool for measuring this property without the need for complex calculations.

Other devices mentioned serve different purposes. For example, a barometer is used to measure atmospheric pressure, a manometer measures the pressure of gases or liquids, and a thermometer measures temperature. Each serves a specialized function that does not pertain to the measurement of specific gravity.