This kit is designed for the colorimetric determination of residual hardness.

The total hardness of water is based on its content of alkaline earth ions (calcium and magnesium ions). This content depends on the geological conditions the water encounters during its course and may vary widely. Knowledge of the total hardness is important for the use of water in industrial as well as municipal applications, e.g. in the household as wash water or as boiler feed water in industry.