What does mg CaCO3/l mean in practice?
The unit expresses the concentration equivalent relative to calcium carbonate, even when the hardness is also formed by magnesium ions.
When does it matter?
Does not literally mean that the entire given mass of CaCO3 is dissolved in the sample.
Which solutions are related to it?
It is used as a common basis for calculations of hardness, alkalinity and capacity, retaining the name of the parameter being tested.