Infrared spectroscopic studies of the low temperature interconversion of sulfuric acid hydrates

Ice condensation on sulfuric acid tetrahydrate: Implications for polar stratospheric ice clouds

“…The film is then warmed in the absence of H 2 O to either 180, 185, or 190 K. The ice evaporates, leaving behind a SAT film (spectrum E). The film shown in spectrum E compares very well to previously published spectra for SAT (Middlebrook et al, 1993;Nash et al, 2000;Zhang et al, 1993), with prominent peaks at 1077 cm −1 (SO 2− 4 asymmetric stretch), 1730 cm −1 (H 3 O + asymmetric bend), and 3148 cm −1 (OH stretch). At the end of an experiment, the usual procedure is to warm the film to 215 K to reform a liquid H 2 SO 4 film, which is then recrystallized to SAT following the above procedure.…”

Acid deprotonation driven by cation migration at biased graphene nanoflake electrodes

“…2, black, red). Near identical changes to the spectra of the acid CQO and carboxylate region in NaCl are observed, but additionally the asymmetric stretch for the solution sulphate anion 14 is seen at 1100 cm À1 . The anion is repelled from the electrode surface when À0.5 V is applied (black) and hence a decrease in absorbance is observed.…”

“…Spectral changes in the sulphate region can be rationalized by predicting trends in interfacial activities of solution species in response to changes in a M + at the electrode. Using the value for Da K + of 7 Â 10 À3 at À0.5 V, determined above, eqn (1) can be used to calculate pK a (app) for HSO 4 À with no applied potential and at À0.5 V, as shown in Table 1 14 however, this will be concomitant with an increase in intensity centered at 1100 cm À1 as the sulphate activity is increased. Overall spectral changes in the sulphate region are therefore predicted to be very weak at pH 3.5, due to the simultaneous increase and decrease in absorbance over this wavenumber range, and broader than at pH 7 due to the contribution from HSO 4 À which exhibits bands over a wider range than SO 4 2À .…”

Dissociation and microsolvation of bisulfate anion

“…[34] This is the reason that the peak at 1,027 cm −1 in NH 4 HSO 4 is at lower wave number than at 1,035 cm −1 in H 2 SO 4 , and the peak at 1,043 cm −1 is at the highest wave number than other two solutes, which is maybe because of the single proton in NaHSO 4 . The peak at 1,035 cm −1 in sulfuric acid was assigned to monohydrate (H 3 O + HSO 4 − ) ion pairs, [32,33] which clarifies the reason of higher peak in NaHSO 4 . Previous studies on MgSO 4 and NaNO 3 attributed the F I G U R E 4 Synchronous two-dimensional correlation spectroscopy contour maps of the symmetric vibrations of sulfate and bisulfate in the hydration process.…”

“…Myhre et al [29] and Knopf et al [30] 1,019 ν s -SO 3 (OH) -, Solid NH 4 HSO 4 Degen and Newman [31] 1,027 This work, Nash and Sully, [32] and Walrafen et al [33] 1,041 ν s -SO 3 (OH) − , Solid NaHSO 4 Degen and Newman [31] 1,043 Myhre et al [29] and Knopf et al [30] 2,878 Second overtone of NH 4 + umbrella bending Zou et al [34] 3,150 ν as NH 4 + Zou et al [34] 3,472 OH stretch in water Kitadai et al [35] F I G U R E 2 peaks are also indicative of the modes with related origin. For example, the positive cross-peaks suggest the peak intensities at the two positions change in same direction; however, the phenomenon is opposite for negative crosspeaks.…”