Which of the following devices is commonly used to assess antifreeze solutions?

The refractometer is the device commonly used to assess antifreeze solutions because it measures the optical properties of a liquid to determine the concentration of antifreeze present in the solution. This method relies on the principle of refraction, where the degree to which light bends as it passes through the solution correlates with its concentration.

Antifreeze solutions, typically made from ethylene glycol or propylene glycol mixed with water, need precise concentration levels to ensure optimal freezing and boiling point protection in fire suppression and plumbing systems. Using a refractometer allows for quick and accurate measurements, making it an essential tool for ensuring safety and efficacy in systems that utilize antifreeze solutions.

Other devices listed in the choices serve different purposes. A hydrostatic test gauge measures pressure within a system, a flow rate meter assesses the volume of fluid passing through a point over time, and a thermometer measures temperature. Each has its specific function, but none are suitable for determining the concentration of antifreeze solutions like a refractometer.