The Langelier index is used to determine which Aspect of water?

The Langelier index is a key tool used to assess the calcium carbonate saturation in water, which reflects its corrosive or scaling potential. Specifically, it measures the balance between the concentration of calcium carbonate in the water and its solubility based on the water's pH and temperature. When water is saturated with calcium carbonate, it is neither corrosive nor scaling; if it is under-saturated, the water has the potential to corrode pipes and infrastructure, while over-saturation may lead to scaling issues.

Understanding this index is crucial for managing water quality, especially in public health and utility settings, where maintaining optimal water chemistry is important for both safety and infrastructure longevity. Thus, the correct answer pertains to calcium carbonate, as that is the specific aspect of water that the Langelier index evaluates.