The intercalation of hexacyanoferrate(II) ions inside the interlayer of a Ni,Al hydrotalcite has been carried out by anionic exchange of the originally existing chloride ions. The best exchange reaction conditions have been established in order to use the intercalated hydrotalcite as a microreactor to synthesise the compound (Ni2Fe11)-Fe-11(CN)(6), i.e., a mixed hexacyanoferrate not containing structural potassium. All the samples have been characterised by elemental chemical analysis, powder X-ray diffraction, FTIR and X-ray absorption spectroscopies and cyclic voltammetry. It has been found that, after destroying the intercalated structure by keeping it in contact with a Ni2+ solution, the desired compound (Ni2Fe11)-Fe-11(CN)(6) is not obtained, since the Fe(CN)(6)(4-) ion is not exchanged as such but as the ion pair with potassium. Moreover, it has been demonstrated by X-ray absorption spectroscopy that no partial oxidation of Fe(CN)(6)(4-) occurs during the intercalation inside the hydrotalcite structure. (C) 2004 Elsevier B.V. All rights reserved.