How is specific gravity measured?

Specific gravity is the ratio of the density of a substance to the density of a reference substance, typically water for liquids and solids, and air for gases. Specific gravity can be measured using a hydrometer, which is a device that consists of a weighted glass or plastic tube that floats in the liquid. The hydrometer has a graduated scale that is used to read the specific gravity of the liquid. Another method is to use a digital density meter, which uses electronic sensors to measure the density of the substance. In this method, the substance is placed in a container and the electronic sensors measure the weight and volume of the substance to calculate its density and specific gravity.

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