**13. Ion exchangers of functional formazane groups**

Chelating ion exchangers of functional formazane groups [88–91] based on the styrene divinylbenzene skeleton [58], amino- and chloromethylated polystyrene [91], cellulose [58, 91], saccharose [65] and methacrylate [58] were applied for sorption and separation of platinum metals, gold, mercury, silver and copper. The sorption capacity towards Pd(II), Ag(I) and Hg(II) ions was in the range 0.05–0.06 mmol/g, 0.4–0.9 mmol/g and 0.6–0.8 mmol/g, respec‐ tively, for formazane ion exchanger based on cellulose, aminomethylated polystyrene; however, their sorption capacity towards Cu(II) ions was close to zero.
