Introduction

The pure water is composed of two parts of hydrogen and one part of oxygen by volume and dissolves many substances. These dissolved salts are the impurities in water. Water is a very good solvent. So it is called as universal solvent.

Hardness of water:

The water which does not give lather with soap is called Hard water. The Hard water contains dissolved calcium & magnesium salts.

Soft water: – The water which can give lather with soap easily is called as soft water.