Sodium n-alkyl sulphates ( n-decyl, n-dodecyl, n-tetradecyl) have been found to be degraded when they are contained in aqueous suspensions of acidic alumina. The surface tension and surface potential of aqueous “surface chemically pure” sodium n-dodecyl sulphate (SDDS) solutions containing aluminium oxide have been studied as a function of adsorption time, surfactant concentration, and the type and amount of alumina. The decomposition of the dodecyl sulphate molecule in aqueous suspensions was followed from the dynamic surface tension and surface potential behaviour. Decomposition depends on the concentration and on the length of time during which the solutions are in contact with acidic alumina. The parent n-dodecanol could be detected in the corresponding SDDS by thin layer chromatography. A small but significant increase in the solution pH was observed when neutral SDDS was added to aqueous suspensions of acidic alumina. This shift of pH, together with the corresponding point of zero charge (PZC) of the acidic alumina, supports an anionic exchange mechanism at the alumina surface. From these findings it is concluded that the labile COS bond of the alkyl sulphates is hydrolysed catalytically by polarization during adsorption. The hydrolysis rates observed in the acidic alumina suspensions exceed those in homogeneous solutions by orders of magnitude. Hydrolysis of sodium n-alkyl sulphates has not been observed in basic alumina suspensions.