One-Step Formation and Characterization of Zn(II)−Cr(III) Layered Double Hydroxides, Zn2Cr(OH)6X (X = Cl,1/2SO4)

Titration curves show that the layered double hydroxide Zn2Cr(OH)6Cl, unlike Zn2Fe(OH)6Cl (shown) or Zn2Al(OH)6Cl (not shown) forms directly from solution, without the intermediacy of "MIII(OH)3", when a mixture of metal chlorides is treated with base. Co(II), Ni(II), and Cu(II) behave similarly. Spectroscopic and titrimetric data show that Zn2Cr(OH)6Cl is formed initially from mixed solutions of various stoichiometries and suggest that the Zn(II) and Cr(III) ions may be locally ordered.