Aluminium-27 nuclear magnetic resonance studies of sulphato-complexes of the hexa-aquo aluminium ion

A sulphato-aluminium complex and a small amount of dimeric aluminium cation have been detected in aqueous aluminium sulphate solutions by means of 27Al n.m.r. spectroscopy. The sulphato-complex is probably formed from the SO42– rather than the HSO4– ion. The results emphasise the complexity of aluminium sulphate solutions and may throw light upon the old controversy over the exact proportion of water present in aluminium sulphate crystals.