A lactometer is a specialized hydrometer used to check the purity and density of milk by measuring how deep it sinks in a sample; it works on the principle that pure milk is denser than water, so it floats higher, allowing users to detect adulteration, primarily water, by observing the scale reading. This simple, glass instrument helps dairy farmers and consumers quickly assess milk quality, though it primarily checks density, not fat content, requiring other tests for full composition analysis.
