Hardness of water is defined as the soap destroying power of water. Water is hard, if soap does not lather easily.
Types of hardness
1. Temporary hardness: it is due to the presence of carbonates of calcium and magnesium.
2. Permanent hardness: It is also called as non-carbonate hardness. It is due to the presence of sulfates, chlorides and nitrates of calcium and magnesium.
Disadvantages of hard water
1. It consumes more soaps and detergents.
2. It produces furring and scaling of boilers and leads to their explosion.
3. In cooking, it produces a change in color and appearance of food.
4. It produces economical losses in industrial processes.
5. It shortens the life of water pipes.
Removal of hardness
1. Temporary hardness can be removed by boning, addition of lime, addition of sodium carbonate and by permuted process.
2. Permanent hardness can be removed by addition of sodium carbonate and by base exchange process.
It is of great importance in community medicine. Water may be purified either on a large scale or small scale.