An evaporator is used for which purpose?

An evaporator is specifically designed to convert a liquid into a gas, and in the context of the question, it refers to the process of converting liquid chlorine into chlorine gas. This process is crucial in water treatment systems, where chlorine is used for disinfection. When chlorine is in its liquid form, it is stored under pressure and kept at low temperatures. An evaporator increases temperature and reduces pressure, allowing the liquid chlorine to vaporize and become gas safely and efficiently.

The other options do not define the main function of an evaporator. Storing chlorine gas, diluting it, or measuring chlorine levels involve different equipment and processes unrelated to the evaporating function. Therefore, the role of the evaporator is essential for ensuring the appropriate dosage of chlorine gas is available for effective water treatment operations.