Preparation, properties and uses of (i) Calomel (ii) Corrosive Sublimate

Calomel

Hg₂Cl₂ is known as calomel. It is prepared by heating HgCl₂ and Hg in an iron vessel.

It can also be prepared by mixing mercury salt with chloride ions.

Properties

1) It is a white powder which is insoluble in water.

2) Hg₂Cl₂ on heating dissociates into HgCl₂ and Hg.

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Corrosive sublimate

HgCl₂ is a corrosive sublimate, which is prepared by passing chlorine over heated mercury or mercury chloride.

It can also be prepared by heating mercury sulphate with NaCl.

Properties

1) It is a crystalline solid.

2) It is soluble in hot water, ethanol and ether.

3) HgCl₂ reacts with KI and forms a colorless solution known as Nessler's reagent.