What tool is used to perform a propylene glycol level test?

The refractometer is the correct tool for performing a propylene glycol level test because it measures the concentration of a solution based on the principle of refraction. When light passes through a liquid, the degree to which it bends is affected by the concentration of solutes, such as propylene glycol in water. This allows a refractometer to provide precise readings of the specific gravity or concentration of propylene glycol, which is essential for ensuring the proper antifreeze levels in solutions.

Other instruments listed, like the hydrometer, are typically used for measuring the density of liquids, which can be less precise for assessing specific concentrations of solutes compared to a refractometer. Thermometers measure temperature and are not suitable for chemical concentration assessments. Pressure gauges measure the pressure of gases and liquids and, while useful in various applications, do not provide information on concentration levels. Thus, a refractometer is specifically designed to yield accurate results for propylene glycol level tests.