The Syntheses of Hydrotalcite-Like Compounds and Their Structures and Physico-Chemical Properties—I: the Systems Mg²⁺-Al³⁺-NO ⁻₃ , Mg²⁺-Al³⁺-Cl⁻, Mg²⁺-Al³⁺-ClO ⁻₄ , Ni²⁺-Al³⁺-Cl⁻ and Zn²⁺-Al³⁺-Cl⁻

Abstract

The basic salts of this system were prepared and their structures and physico-chemical properties were studies by electron microscopy, chemical analysis, X-ray powder diffraction, thermal analysis, i.r. absorption spectra, BET absorption, and acidity-basicity measurements. The salts were found to be new compounds analogous to hydrotalcite. They can be expressed by the formula; [M ²⁺ _x M ³⁺ _y (OH)_2(x+y))]^y+ [A ⁻ _z1 , A_z2^- · mH₂O]^{-(z1 + 2z2)} where M²⁺ and M³⁺ denote di- and trivalent cations, A⁻ and A²⁻ denote mono- and divalent anions, respectively, and y = z₁ + 2z₂; z₁ ≫ z₂.

The structures consist of positively charged Cd(OH)₂-like basic layers and intermediate layers formed from anions and water molecules with the solid solution of divalent cation (M²⁺) and trivalent cation (M³⁺) being formed in the range of 0.6 > x/(x + y) > 0.9. The anions of Cl⁻, NO ⁻₃ and ClO ⁻₄ are easily substituted by CO ²⁻₃ . A large part of the NO ⁻₃ makes a monodentate-type bond and the ClO ⁻₄ a bridge-type bond.