Original: Any impurities remain solid while the nickel carbonyl gas passes into a large chamber at high temperatures in which tens of thousands of nickel spheres , called pellets , are constantly stirred . The nickel carbonyl decomposes , depositing pure nickel onto the nickel spheres .
Simplified: The nickel carbonyl is blown into nickel pellets , where it coats the pellets with pure nickel and puts out carbon monoxide .