An approach to non-specific interactions of the hydrophobe type based on the study of the interfacial behaviour of normal aliphatic alcohols

Abstract

The adsorption of normal aliphatic alcohols at the mercury aqueous solution interface has been studied by measuring the differential capacity at the potential of minimum capacity ( i.e. maximum d'adsorption) as a function of the length of the aliphatic chain, the concentration of the alcohol in solution and the nature of the electrolyte [1]. C −1 is observed to vary linearly with the number of carbon atoms n C in the aliphatic chain and the slope varies with the nature of the anion of the base electrolyte (F −, Cl −, Br − or I − but not with the cation (K + or Na +). The limiting value for n C = 0 shows that the adsorbed layer includes at least a layer of water molecules which can be attributed to the hydration of the polar heads. These results, together with those given by Pleskov et al. [2], obtained by photoemission studies, suggest that the alcohol molecules are probably not adsorbed in their extended conformation. One also notes that C is independent of the alcohol concentration in solution once saturation is reached and what ever the base electrolyte. At the interface the situation is therefore the same as in solution with the appearance at this point of a new phase and this serves to illustrate the close correlation which exists between the physico-chemical properties of the interfacial phase as compared to those of the solution. This leads to the interesting conclusion that although the adsorption of alcohols on mercury have long been studied [3] this approach sheds a new light on the interaction between adsorbed surface active substances and the other solution constituents.