Larson index
CORROSION INDEX - Larson index or Larson Ratio (LR) :

The Larson Ratio (LR) describes the corrosivity of water towards mild steel.
The index is the ratio of the twice moles per liter (mol/L) of sulfate (SO42-) plus chlorides (Cl-), to the moles per liter of alkalinity (in form bicarbonate and carbonate) :

Ratio > [ (sulfate x 2] + chloride ] / alcalinity

Interpretation of results (personal suggestions):
(according to Larson, tendency to corrosion with LR> 0.5)

Tendency to corrosion
< 0.2
No metal tendency
Light metal tendency
Low metal tendency
Mid metal tendency
=> 1.0
High metal tendency