What is the hardness of water

Water hardness is the main monitoring indicator of dyeing and finishing water. It mainly indicates the content of calcium, magnesium and other salt impurities in the water. The more salt impurities, the higher the hardness. Natural water is generally divided into temporary hardness and permanent hardness, the sum of the two is called total hardness.

Temporary hardness:

After boiling, the impurities in the water can be precipitated out. This kind of water is called temporary hard water, and its hardness is called temporary hardness. The impurities that can form temporary hardness are mostly acid carbonates of calcium and magnesium, which can decompose insoluble carbonates when heated again, such as:

Ca(HCO3)2△CaCO3↓+H2O+CO2↑

The formed carbonate precipitate is separated and removed from the water, thereby reducing the hardness of the water.

Permanent hardness:

The water that cannot be boiled and must be chemically treated to remove the impurities is called permanent hard water, and its hardness is called permanent hardness. There are many impurities that can form permanent hardness

These are calcium and magnesium sulfates, chlorides, etc., which can be removed from water using chemical methods. E.g:

CaSO4+Na2CO3CaCO3↓+Na2SO4