The reaction of Cu2+ ions with CN−,SCN− and CuCl2 will lead to the formation of [Cu(CN)4]3−,[Cu(SCN)4]3− and CuCl which will shift the reaction in the backward direction. Cu2++2Cn− → Cu(CN)2 CuCN + 3CN− → [Cu(CN)4]3− Cu2++4SCN− → [Cu(SCN)4]3− CuCl2+Cu → 2CuCl−