Aluminium-27 nuclear magnetic resonance studies of acidic solutions of aluminium salts

Abstract

²⁷ Al N.m.r. studies have been carried out in the absorption mode at 15 Mc./sec. and under conditions of resolution such that lines as narrow as 3 c./sec. have been observed. The dependence of linewidth upon pH is consistent with the simple protolytic reaction Al(H₂O)₆³⁺+ H₂O ⇌ Al(H₂O)₅OH²⁺+ H₃O⁺ and suggests that polymer alumino-ions if formed are formed by a separate ion-association step. Variable-temperature experiments reflect changes in the above equilibrium and cannot be used to determine the kinetic parameters for water exchange. It is also demonstrated that the complex ion Al(H₂O)₅HSO₄²⁺ is formed in the presence of sulphuric acid.