Total acidity for a series of modified clays obtained from a natural vermiculite is determined through temperature programmed
desorption (TPD) using ammonia as probe molecule. Results obtained for the acidity range from 15.1 to 68.5 meq/100 g.
Immersion enthalpies of the clays in benzene, water and aqueous solutions of NH3 0.058 M and NaHCO3 0.053 M are determined. The results obtained show that immersion enthalpies in benzene and water are between −6.26 and −25.6
J g−1 and −2.10 and 5.55 J g−1, respectively and are smaller than the values obtained for the immersion enthalpies in the solutions.
Immersion enthalpy values in NH3 solution are greater than the obtained using NaHCO3. Linear relations between the total acidity of the clays and the immersion enthalpies in the basic solutions are determined.
An interaction factor using ammonia is calculated since the relation between the immersion enthalpy in ammonia solution and
in water and it may be deduced that the relation with the total acidity is of second order tendency between them.