Langelier Saturation Index
A calculated number used to predict the calcium carbonate (CaCO3) stability of a water; that is, whether a water will precipitate, dissolve, or be in equilibrium with, calcium carbonate.
It is sometimes erroneously assumed that any water that tends to dissolve CaCO3 is automatically corrosive.
Langelier saturation index = pH - pHs where pH = actual pH of the water, and pHs = pH at which the water having the same alkalinity and calcium content is just saturated with calcium carbonate.
See Also: Saturation Index Rzynar Index Saturation Index