What is one of the functions of a thorpe tube in gas delivery systems?

A thorpe tube is designed primarily to visually indicate the flow rate of gases in delivery systems. It operates based on the principle of floating a float within a tapered tube. As gas flows through the tube, the float rises to a level that corresponds to the specific flow rate of the gas, which can be read directly on a scale printed along the tube. This visual indicator allows healthcare providers to quickly assess and adjust gas flow as needed for patient care, making it an essential tool in various medical settings.

In contrast, the other functions described do not align with the purpose of a thorpe tube. Measuring fluid viscosity is a different measurement process that does not pertain to gas flow. Calibrating gas purity involves analyzing the composition of the gas rather than measuring flow rates. Regulating pressure changes is a function typically managed by regulators rather than by a thorpe tube. Thus, indicating flow rate visually is the correct and most appropriate answer related to the function of a thorpe tube in gas delivery systems.