What instrument is commonly used to measure the flow rate of chlorine gas?

The instrument commonly used to measure the flow rate of chlorine gas is a rotameter. This device operates on the principle of variable area flow measurement, where a float rises and falls within a conical tube as the flow rate changes. The position of the float indicates the flow rate on a calibrated scale.

Rotameters are particularly suitable for gases like chlorine due to their simple design, ease of use, and ability to provide a visual indication of flow. They can also accurately measure low flow rates, which is important in chlorine gas applications, where precise dosing is essential for disinfection in water treatment processes.

In contrast, other instruments listed may not be as effective for measuring chlorine gas specifically. For example, the proportional meter is more common for liquid applications, while nutating-disc and compound meters are primarily designed for water or other liquids rather than gases, making them less ideal for chlorine measurement.