Alkalinity measurement indicates the fluid's ability to neutralize acids -- an important measure in coolants and some aqueous oils. High alkalinity means good buffering capacity against acids, while low value can cause increased risk of corrosion.
The analysis is carried out by titration, in which acid is added and the amount needed to neutralize the alkalinity is recorded.
The result gives the customer an assessment of whether the fluid is still protecting the system effectively, or whether it is time for replenishment or replacement.