Preparation, composition and structure of some nickel and zinc ferrocyanides: Experimental results.

Several methods have been used for preparation of nickel and zinc ferrocyanides: precipitation, growth in a gel and a new method based on growth on a solid alkali-metal ferrocyanide. The granulometry, morphology, composition and structure of the compounds were studied. Only the last method of preparation gives products suitable for use as ion fixators in columns on a large scale. The nickel ferrocyanide compositions can be written as M(I)(2x)Ni(2-x)Fe(CN)(6).yH(2)O with M(I) Na, K, Cs, H and 0 < x < 0.8. They have a cubic lattice with a partial occupancy of iron sites. For zinc ferrocyanides, rhombohedral M(I)(2)Zn(3)Fe(CN)(6).xH(2)O, trigonal Zn(2)Fe(Cn)(6).2H(2)O and other cubic compounds were found. Products resulting from the fixation of caesium by ion-exchange were also studied.