What does the Langelier index determine the stability point of?

The Langelier Index is a calculation used to determine the stability of calcium carbonate in water. Specifically, it is designed to assess whether water is scaling, corrosive, or in a state of equilibrium regarding calcium carbonate saturation. The index helps predict the potential for calcium carbonate to precipitate out of solution or for already present calcium carbonate to dissolve, which can have significant implications for water quality and plumbing systems.

When the Langelier Index indicates that the water is supersaturated with calcium carbonate, there is a tendency for calcium carbonate to precipitate and form scale. Conversely, if it shows that the water is undersaturated, it means that the water is corrosive and can dissolve existing calcium carbonate deposits or corrode the infrastructure. Thus, the correct focus of the Langelier Index on calcium carbonate makes it an essential tool in water treatment and management.

Factors such as pH, temperature, alkalinity, and calcium ion concentrations influence the Langelier Index, but the primary substance it is evaluating for stability is calcium carbonate.