Decomposition of aqueous dithionite. Part I. Kinetics of decomposition of aqueous sodium dithionite

Abstract

A rate equation for the total path of decomposition of aqueous Na2S204 in the p H range 3.5-5.0 at 23 "C was determined, taking into account the rapid autocatalytic decomposition as well as the "induction" period. The kinetic data were determined by a continuous polarographic method. The form of the rate equation was found by studying the decomposition of aqueous Na2S204 at various values of p H and at various initial concentrations. Rate constants were calculated from the data using the integrated form of the rate equation. The rate equation, with certain limitations, was found to be where kl = 1.67 x 10-l l mole-' s-l and k, = 5.83 x 10312 molew2 s-' at 23 "C; C and C, being dithionite concentration at time t and initial concentration, respectively. The integrated form of the rate equation was used to generate decomposition curves, which are in reasonable agreement with the experimental data.

pHLIP-Mediated Translocation of Membrane-Impermeable Molecules into Cells

“…These results indicate that the C-terminus of pHLIP is located inside the vesicles at pH 4, thus protecting NBD from dithionite quenching, while the NC(X) 4 cyclic cargo peptides stay outside. Slow quenching of NBD fluorescence is sometimes observed on a time scale of minutes, as can be seen for the pHLIP-NBD conjugate, perhaps due to leakage of dithionite or its decomposition products (Lem and Wayman, 1970; Wayman and Lem, 1970) into the liposomes at pH 4. As mentioned in the Materials and Methods section, protection is evaluated from the first data point collected immediately after addition of dithionite (denoted by a circle in Figure 1B).…”

“…Changes in the fluorescence signal of NBD were monitored upon addition of 5 μL of sodium dithionite (Na 2 S 2 O 4 ) (pH 4.0, 1M sodium phosphate; final dithionite concentration in the cuvette = 0.5 – 2 mM) to a 95 μL sample of pHLIP construct in buffer B that had been incubated in the presence of liposomes at pH 4.0 for 30 min. Fresh dithionite stock solution was prepared for each measurement because dithionite decomposes rapidly at low pH (Lem and Wayman, 1970; Wayman and Lem, 1970). The percentages of protection are calculated from the first data point collected after addition of dithionite.…”

Oxidative Cleavage of S–S Bond During the Reduction of Tris(pyridine‐2‐carboxylato)manganese(III) by Dithionite in Sodium Picolinate–Picolinic Acid Buffer Medium

“…Freshly prepared dithionite solutions were always used for the experiments. Na 2 S 2 O 4 solutions are quite stable at pH >5 and in the concentration range (0.2-1.2) × 10 −3 mol dm −3 [21] at which the reactions were studied.…”

Large Amplitude pH Oscillations in the Hydrogen Peroxide−Dithionite Reaction in a Flow Reactor

“…This observation was confirmed by others. [2][3][4][5][6][7] Moreover, with an excess of sulfite ion, so as to minimize the effect of decomposition products, neither the induction period nor the fast reaction are detectable.…”

“…However, we point out that other laboratories have never confirmed these oscillations. 6,7 Our own efforts repeatedly failed to reproduce pH oscillations of any kind in a closed reactor when we studied the disproportionation of S 2 O 4 2-in a concentration range 0.001-0.05 M and in a temperature interval 25-70°C excluding the air oxygen. Only a minimum, followed by a single maximum, appeared on the experimental pH-time curves.…”