It is the process that is utilized to obtain pure Nickel from the impure Nickel.
In this method we react the nickel with carbon-monoxide at about 60 to 80 degree Celsius, to get a carbonyl compound which is volatile in nature, the impurities can not make the volatile compund , so here they get separated. Now this compound is further heated at higher temperatures to decompose the carbonyl compound. upon decomposition the pure Nickel metal can be recovered. the complete reaction is as follows :-