Complexes formed in the following methods are I. Mond's process for purification of nickel. II. Removal of lead poisoning from the bodyIII. Cyanide process for extraction of silver. IV. Froth flotation process for separation of ZnS from galena ore by using depressant. I II III IV (a) Ni(CO)4 [Pb(EDTA]2– [Ag(CN)2 ] – [Zn(CN)2 ] (b) Ni(CO)4 [Pb(EDTA]2– [Ag(CN)2 ] – [Zn(CN)4 ] 2– (c) Ni(CO)6 [Pb(EDTA)]4– [Ag(CN)2 ] – [Zn(CN)6 ] 4– (d) Ni(CO)4 [Pb(EDTA)]2– [Ag(CN)4 ] 3