Which elements are measured in the hardness determination of water?

The determination of water hardness primarily focuses on the concentrations of calcium and magnesium ions present in the water. These two elements are the main contributors to what is referred to as 'hardness' in water. When water percolates through limestone, chalk, or gypsum, it can dissolve these minerals, leading to elevated levels of calcium and magnesium.

Hard water typically contains high concentrations of these ions, which can lead to various issues, including scaling in pipes and appliances and diminished effectiveness of soap and detergents. As a result, the measurement of hardness typically emphasizes these two ions, making it clear why calcium and magnesium are the correct components of water hardness.

In contrast, sodium and potassium are more associated with the concept of salinity rather than hardness, while iron and manganese are often linked to water quality issues like staining and taste, and chlorine and sulfate are more relevant to disinfection processes and anion concentration rather than hardness. Thus, calcium and magnesium are indeed recognized as the critical elements for assessing water hardness.