A solid bounded by plain surfaces having definite geometrical shapes. In nature, crystals are found as minerals, for example, ruby, diamond, graphite, etc. These crystals have beautiful color due to impurities or traces of water present in them.

Making Crystals

1.           Dissolving a solid in water or any other solvent and then evaporating the liquid. For example, salt, nitre, alum in water. Sulfur in carbon disulphide or carbon tetrachloride CCl4, iodine in petrol or benzene or spirit.
2.           By melting a solid and allowing it to cool properly. For example, prismatic sulfur.
3.           By sublimation. For example, iodine and ammonium crystals.
4.           By subjecting a solid to great heat and pressure. For example, diamond and graphite. The cost is prohibitive as artificial diamond is more costly than natural diamond.

Water of Crystallization

Some solids while crystallizing out from solution unite with a definite quantity of H2O known as water of crystallization/ hydration. This water of crystallization can be driven out by heating the crystal to 100°C, and may be condensed and tested. Such crystals lose their crystalline structure and become anhydrous.

Water of crystallization is the number of molecules of water combined it a loose chemical combination which on heating on exposure to air is partly on fully given off by a hydrated salt.

Hydrated Salts

A hydrated salt is a substance which contains water of crystallization which on exposure to air or heat becomes anhydrous by giving off partly or fully its water of crystallization.

Hydrated Salt
Chemical Formula
Common Name
sodium carbonate
Na2CO3 · 10H2
washing soda
sodium sulphate
Na2SO4 · 10H2
Glauber’s salt
copper sulphate
CuSO4 · 5H2
blue vitriol
ferrous sulphate
FeSO4 · 7H2
green vitriol
zinc sulphate
ZnSO4 · 7H2
white vitriol (H2SO4 is called oil of vitriol)
cobalt chloride
CoCl2 · 6H2O

barium chloride
BaCl2 · 2H2O

calcium chloride
CaCl2 · 6H2O

magnesium sulphate
MgSO4 · 7H2
Epsom salt

Crystals without Water of Crystallization – Anhydrous

Anhydrous Salt
Chemical Formula
sodium chloride (common salt)
potassium chromate  
potassium chloride  

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