ABSTRACT
Hardness in water is caused by the presence of certain positively charged metallic ions in solution in the water. The most common of these hardness-causing ions are calcium and magnesium; others include iron, strontium, and barium. The two primary constituents of water that determine the hardness of water are calcium and magnesium. If the concentration of these elements in the water is known, the total hardness of the water can be calculated. To make this calculation, the equivalent weights of calcium, magnesium, and calcium carbonate must be known; the equivalent weights are given below:
Calcium (Ca) 20.04 Magnesium (Mg) 12.15 Calcium carbonate (CaCO3) 50.045
The hardness (in mg/L as CaCO3) for any given metallic ion is calculated using Equation 8.1.
