The calcium and magnesium ions in the water are the ions that cause the hardness of the water. If these ions are removed from the water, the water is softened. The working principle of the softening tools used in homes is to remove calcium and magnesium ions from the water.

By the hardness of the water, the capacity of water to precipitate soap is expressed. Soap is precipitated by calcium and magnesium ions in water. The amount of cations is measured by displacement with sodium and potassium ions in the soap. Other cations can precipitate soap, but they are complex with organic structures and are not very effective in softening the water. In addition, the amount of magnesium and calcium ions in water is considerably higher than other metal ions.

In practice, total hardness is expressed as the sum of calcium and magnesium concentrations. Hardness is generally expressed in mg / l in calcium carbonate. If this value is less than the total carbonate and bicarbonate alkalinity, the hardness amount is called carbonate hardness and if it is large, it is called non-carbonate hardness.

There are various methods for determining the hardness value of water, such as calculation method, EDTA titration method or soap method. One of these methods, EDTA, is the Ethylene Diamine Tetra Acetic Acid method. This chemical compound and its sodium salts are added to a solution of metal cations. If Eriochrome Black-T is added to the solution with a pH value of 10 and containing calcium and magnesium, the solution turns red. The solution is then titrated with EDTA and the calcium and magnesium ions complex with EDTA. When the reaction is complete, the color turns blue.

The hardness value of water is a value that indicates the quality of the water used in homes or enterprises.

 

Within the scope of chemical analysis, total hardness determination studies are carried out by titrimetric method in authorized laboratories.