A kinetic study of the dehydrations of the alums KCr(SO4)2. 12H2O and KAl(SO4)2. 12H2O

Abstract

By product identification and competition studies with selected solutes it has been shown that the reducing species generated m the ultraviolet photolysis of aqueous iodide ion is the solvated electron. Thus it does not react much more rapidly with O$_2$ than with N$_2$O, it reacts with 1:2-dichloroethane to form chloride (Cl$^-$) and not H$_2$ and reacts readily with I$^-^3$ ion at a rate which increases with ionic strength so that the slope of the Bronsted plot is approximately unity. In solutions with $\mu$ = 0.23 at solute concentrations where e$^-_{aq\ldot}$ reacts in less than 3 x 10$^{-10}$ s there is insufficient time for the ion atmosphere to form and the rate constant diminishes accordingly. The primary quantum yield is greater at 2288 $^\overset{\circ}{\mathrm A}$ than at 2537 $^\overset{\circ}{\mathrm A}$ and at each wavelength it increases markedly with temperature. Evidence is presented that the electron moves rapidly to a distance (of at least 10 $^\overset{\circ}{\mathrm A}$) from the site of its formation and that this process, which occurs when the excited iodide ion dissociates and is not deactivated, involves the rotation of water molecules.