BASIC IRON(3) CARBONATES .2. PREPARATION RADIOCRYSTALLOGRAPHY AND INFRARED SPECTRA OF (NH4)2FE2(OH)4(CO3)2.H2O

The obtention of the crystalline basic carbonate of iron (III) and ammonium, (NH4)2Fe2(OH)4(CO3)2 · H2O, is described and its formula is established by chemical analysis and infrared spectroscopy. The powder X‐ray diagram could be indexed tetragonally leading to a body centred elementary cell with a = 12,04 ± 0,02 Å and c = 6,62 ± 0,01 Å. The infrared spectra show that in the CO 32− groups either one oxygen atom is linked to one iron atom or, rather, two oxygen atoms are linked to two iron atoms. The symmetry of the NH 4+ groups is lower than C3v. The OH‐groups are linked by hydrogen bonds of 2,75 Å. Two sorts of OH‐groups can be distinguished, with a radius of approximately 1,34 Å and 1, 48 Å, respectively. The iron atoms are octahedrally coordinated by oxygen atoms, but either the octahedra are deformed or the iron atoms are in part coordinated tetrahedrally. Copyright © 1969 Verlag GmbH & Co. KGaA, Weinheim