(a) Vapor phase refining- This method is based upon the principle that the impure metal is converted into a suitable volatile compound which on being heated, gets decomposed to give pure metal. Among its examples, we can observe
(i) Mond process (also called carbonyl process)
(ii) van-Arkel de-Boer’s process (also called iodine refining process).
The Mond’s process is used for the purification of Nickel.
The van-Arkel de-Boer’s process is use for the purification of Zr (zirconium), Ti (titanium), V (vanadium), Th (thorium), etc.
(b) A soluble complex of silver cyanide is formed as NaCN oxidizes silver and the impurities remain unaffected and thus they are filtered off. The reaction is as follows:
4Ag + 8CN- + 2H2O + O2→ 4 [Ag [CN] 2]- + 4OH-
This process is known as leaching.
(c) Compounds like Pine oil, Xanthates, Fatty acids etc are called as collectors which attach themselves by the polar groups to grains of minerals which then become water repellant and thus pass on into the froth.
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