Measurements of hydrogen peroxide conversion into Caro's acid in sulphuric acid at T ≈ 298 K and H2SO4 content 78/95 wt% were performed to monitor the equilibriums: H2O2 + H3O+ ↔ H3O2+ + H2O and H2O2 + HSO4- ↔ HSO5- + H2O yielded K(298) = 8 × 10-4 and K(298)
= 1.2 × 10-2, respectively. The physical solubility of H2O2 as well as that including H3O2+ and HSO5- has been estimated. The calculation of the Henry's law coefficient (T = 298) of H2O2 shows the typical salting-out effect, while for the case of H3O2(aq)+ and HSO5(aq)- this coefficient
exhibits a sharp rising with H2SO4 content, starting from almost 50 wt%. An increase in the oxidative power of H2O2, H3O2(aq)+ and HSO5(aq)- is observed, as H2SO4 concentration increases. In addition, the kinetics of the liquid-phase reactions involving these reagents are analysed on the basis
of a correlation between the rate constants and the thermodynamic data. Finally, the occurrence of sulphate aerosol reactions involving the components that affect halogen activation in the low stratosphere is discussed.