Sulfate reduction reversibility

Trudinger, P.A. and Chambers, L.A., 1973. Reversibility of bacterial sulfate reduction and its relevance to isotope fractionation. Geochim. Cosmochim. Acta, 37 1775— 1778. 

Maximum expression of isotope fractionation will occur when the internal and external sulfate pools are in exchange equilibrium, as well as the reversible steps in the sulfate reduction process (steps 2 and 3, Eqn. 11). Under these circumstances the final step (step 4, Eqn. 11) will be rate limiting. Exchange equilibrium will be best realized when cellular metabolism is slow, or in other words, at low specific rates of sulfate reduction. This explains why high fractionations are observed at low specific rates (Fig. 2). 

Polymer-supported reagent. HMPT supported on a polystyrene-type resin is a catalyst for SN2 reactions5-7 and for reduction of ketones by NaBIi4.7 It also has a marked effect on the alkylation of ethyl acetoacetate with diethyl sulfate. In the presence of solid HMPT the enolales undergo 60 70% O-alkylation. In the absence of HMPT, the lithium enolate does not react and the sodium and potassium enolates undergo C-alkylation (90-100%). There is some difference in the effect of solid and liquid I1MPT The solid HMPT increases the reactivity of the K. enolate more than the liquid form, whereas the reverse is true with the Li enolate.8... 

Disposable batteries have relatively short lives because electron-producing chemicals are consumed. The main feature of rechargeable batteries is the reversibility of the oxidation and reduction reactions. In your car s rechargeable lead storage battery, for example, electrical energy is produced as lead dioxide, lead, and sulfuric acid are consumed to form lead sulfate and water. The elemental lead is oxidized to Pb2+, and the lead in the lead dioxide is reduced from the Pb4+ state to the Pb2+ state. Combining the two half-reactions gives the complete oxidation-reduction reaction ... 

OXIDATION-REDUCTION INDICATOR. A substance that has a color in the oxidized form different from that of the reduced form and can be reversibly oxidized and reduced. Thus, if diphenylamine is present in a ferrous sulfate solution to which potassium dichromate is being added, a violet color appears with the first drop of excess dichromate. 

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