Nitric acid, proton affinity

Despite a wide range of the modifiers used, there is a clear symbasis between the calculated proton affinities and the experimental stability indices Kst (Figure 3). The decrease in concentration of nitric acid in the interlayer space will give rise to a poorer stability of GICs, if the proposed stabilization mechanism is valid. To verify this assumption, the treatment of graphite nitrate with 25-fold excess of acetic acid, compared to that used in the above procedure, was carried out in a glass column. Most of the molecules of nitric acid are probably removed from the interlayer space under such a treatment. It turns out that this procedure reduces the expansion... 

One of the components of the system may be a solvent This is the case, for example, with a solution of nitric acid in sulphuric acid. The sulphuric acid, with a very small affinity for the proton, plays the role of an acid and nitric acid behaves like a base. 

In general it is true that a solvent with a high proton affinity, such as liquid ammonia or hydrazine, will be a levelling solvent for acids, while a solvent of low proton affinity such as acetic acid, hydrogen fluoride, and nitric or sulphuric acid will be a levelling solvent for bases. 

Contradictory results regarding the possibility of protonation of silica are probably due to different affinities of monovalent anions to the silica surface at low pH. Recent electroacoustic study showed that silica carries positive electrokinetic charge in solutions of HCl at pH < 2, but the sign is negative even at very low pH in the presence of nitric of chloric VII acid [22]. This difference suggests some specific interaction between silica and monovalent anions at low pH, thus, the lEP and PZC do not necessarily coincide. 

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