Electrosorption of tert-butyl compounds on Hg from aqueous Na2SO4 solution: tert-butylamine

The adsorption of tert-butylamine (TBUNH₂) at the Hg/0.5 M aqueous Na₂SO₄ polarized interface has been studied by means of electrocapillary measurements. Adsorption has been found to follow a Frumkin isotherm with interaction parameter corresponding to particle-particle attraction. Adsorption is congruent neither with respect to charge nor with respect to potential, but the model of two capacitors in parallel is much better approached, especially at positive rational potentials. The positive value of the interaction parameter is explained in terms of unfavourable solvent-adsorbate surface interactions, slightly dependent on the electric field. The fundamental adsorption parameter of TBUNH₂ are compared with data previously obtained for TBUOH. The behaviour of TBUNH₂ at the air-solution interface seems to exclude any specific interaction between the Hg surface and NH₂ group; the differences between TBUNH₂ and TBUOH are probably to be related to the different nature of the particle-particle interactions.