Chemistry of Calamine

Calamine is a mixture of zinc oxide and ferric oxide having molecular formula ZnCl2.

Preparation:

It is prepared by the reacting zinc sulphate with sodium bicarbonate.
$$\ce{ZnSO4 + 2NaHCO3->ZnCO3 + Na2SO4 + CO2 + H2O}$$

Physical properties of calamine

  • It is a white soft powder which is insoluble in water.
  • It is basic in nature.

Chemical properties of calamine

a. Action with HCl:
$$\ce{ZnCO3 + 2HCl->ZnCl2 + CO2 + H2O}$$

b. Action with H2SO4:
$$\ce{ZnCO3 + H2SO4->ZnSO4 + CO2 + H2O}$$

Uses of calomel:

  • It is used in medicine to prepare calamine lotion.
  • It is used as an anti-itching agent to treat conditions such as sunburn, rashes, insect bites etc.

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