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Questions
Outline the principles of refining of metals by the following method:
Vapour phase refining
Write the principles of vapour phase refining methods.
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Solution
Vapour phase refining is the process of refining metal by converting it into its volatile compound and then decomposing it to obtain a pure metal. To carry out this process,
- The metal should form a volatile compound with an available reagent, and
- The volatile compound should be easily decomposable so that the metal can be easily recovered.
The following examples illustrate the procedure:
Mond process for refining of nickel: The Mond process forms nickel tetracarbonyl, a volatile compound, by treating impure nickel at 330–350 K in a carbon monoxide current.
\[\ce{\underset{(Impure)}{Ni} + 4CO ->[330-350 K] Ni(CO)4}\]
The complex thus formed on being heated to 450-470 K yields pure nickel.
\[\ce{Ni(CO)4 ->[450-470 K] \underset{(Pure)}{Ni} + 4CO}\]
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