Complex Behavior in the Formaldehyde−Sulfite Reaction

Abstract

The formaldehyde-sulfite reaction is an example of an "acid-to-alkali" clock. It displays an induction period, during which the pH varies only slowly in time, followed by a reaction event, during which the pH increases rapidly by several units. When the reaction is performed in a closed (batch) reactor, the clock time is found to increase with a decrease in initial concentrations of formaldehyde and sulfite and an increase in the total initial concentration of S(IV). At long times, following the clock event, there is a slow decrease in pH. In an open (flow) reactor, bistability between a low-pH steady state (pH approximately 6-8) and a high-pH steady state (pH approximately 11) is observed. Additionally, we report the existence of sustained, small-amplitude oscillations in pH in this system. An extended kinetic mechanism reproduces the batch behavior but fails to account for the complex behavior observed in the flow reactor. Possible additional reaction steps are discussed.

Contribution of Hydroxymethane Sulfonate to Ambient Particulate Matter: A Potential Explanation for High Particulate Sulfur During Severe Winter Haze in Beijing

“…An alternative pathway that may explain the high particulate sulfur observed during winter haze events is the reaction of dissolved bisulfite (HSO 3 − ) and sulfite (SO 3 2− ) with HCHO to form HMS (Boyce & Hoffmann, ; Kok et al, ; Kovacs et al, ; Munger et al, ; Olson & Hoffmann, ). In this pathway, which does not require oxidative conditions, dissolved SO 2 dissociates to form bisulfite and sulfite, which then combine with dissolved formaldehyde to form HMS (HOCH 2 SO 3 − ): …”

Influence of elemental impurities in aluminum hydroxide adjuvant on the stability of inactivated Japanese Encephalitis vaccine, IXIARO®

“…At neutral pH, we can assume the following equilibrium: HSO 3 − ⇔ H + + SO 3 2− , pK a = 7.2. During neutralization, formaldehyde forms a sulfite adduct according to the following equations [11]:…”

Chemoelastodynamics of Responsive Gels

“…Besides proton-autoactivated reactions, there are also a number of hydroxyl ion-autocatalyzed reactions where pH jumps from 6 to 11 are observed between the flow (F) and thermodynamic (T) branches [59]. Responsive polyelectrolyte gels have been reported to dramatically change size or volume over narrow pH domains (one or two units) within approximately the same spectrum of pH values than the above bistable system range.…”