Which instrument is used to measure the specific gravity of urine?

The refractometer is the instrument specifically used to measure the specific gravity of urine. This tool operates on the principle of refraction, which is the bending of light as it passes through a liquid. When urine is placed in the refractometer, the device measures how much the light is bent, which correlates with the concentration of solutes in the urine. The specific gravity reflects the concentration of substances in the urine compared to pure water, providing valuable information about hydration status and kidney function.

While a hydrometer can measure the specific gravity of liquids, it is not ideal for urine analysis in clinical settings due to potential inaccuracies from the varied composition of urine. A manometer measures pressure of gases or liquids, not specific gravity. A barometer is designed to measure atmospheric pressure and has no application in the measurement of specific gravity in urine. Thus, the refractometer is the appropriate and precise choice for this purpose.