Hard Water and Soft Water

Rain water is pure, but after reaching the earth, many types of impurities and salts dissolve in it, due to which the properties of water also changes.

If we look at the water of the sea, ordinary salt is dissolved in more quantity than other salts, due to which the taste of sea water is very salty (saline). There are two types of water depending on the presence of water soluble salts.

Water that does not contain salts, etc. and easily lathers with soap, such water is called soft water. Rain water and distilled water are examples of soft water.

If soap is not rubbed in water, froth does not arise. The same white substance is formed with soap, it is called hard water. This is due to the magnesium and calcium salts present in it. Sea water, lake water and water from open wells are often hard water.

Measures to remove the hardness of water

Due to dissolution of ordinary salt or calcium salts in hard water, the taste of water is good. Therefore it can be used for drinking. However, it cannot be used in pharmaceutical or chemical sector industries, because there is a need for pure water in which no impurities are dissolved.

Hard water is completely unusable for washing clothes. This also spoils the cooking and eating utensils because these utensils solidify the layer of salts dissolved in hard water. A white colored layer solidifies on the coil parts of the water heating immersion rod. This white layer consists of impurities dissolved in water.

Water hardness is of two types depending on the salts dissolved in it:

  1. Temporary hardness
  2. Permanent hardness

1. Temporary hardness: The hardness that is caused by bicarbonate salts of calcium and magnesium dissolved in the water is called temporary hardness. This type of hardness can be easily overcome by boiling water at high temperature. Bi-carbonate salts precipitate as insoluble carbonate salts by heating. The salts settle down and then they can be easily separated by filtering. 

2. Permanent hardness: Such hardness is due to dissolution of calcium and magnesium in chloride and sulfate salts in water. It cannot be boiled away with proper means. It overcomes by special chemical treatments.

(A) By washing soda: When dissolved soda is added to hard water, the dissolved impurities of sulfate and chloride salts are converted into insoluble carbonate salts. Insoluble salts are filtered and separated. Thus, they remove these impurities.

(B) By permutite method (using zeolide): Zeolite contains sodium and aluminum oxide sand particles and water. When the hard water passes through the filter of permutid (zeolite), the calcium and the magnesium ions of the salts are added to zeolite and; the sodium ions of the zeolite moves into the water. The water thus obtained is not hard.