Sodium sulfite

About: Sodium sulfite is a research topic. Over the lifetime, 2548 publications have been published within this topic receiving 18523 citations. The topic is also known as: Na2SO3 & Anhydrous sodium sulfite.

[126] Preparation of reduced DPN (chemical method)

Abstract: Publisher Summary There are two types of such preparations of DPNH which have gained some use: the disodium salt and the barium salt. In both cases, the diphosphopyridine nucleotide (DPN) is reduced chemically with hydrosulfite. In the former procedure, the disodium salt is isolated subsequent to the removal of sodium sulfite and sodium sulfate formed from the hydrosulfite by fractional crystallization from the aqueous solution at very low temperatures. From the analytical and spectrophotometric data presented, it appears permissible to conclude that the preparation was about 92% pure and that about half of the impurity was BaCO 3 . It is possible that the rest may be moisture not removed at 60 ° but labile at 100 °. Such preparations of DPNH were stored in the cold over calcium chloride. Preparations held in a desiccator for a year at room temperature showed a decline of the 340 mg: 260 mμ ratio to about 0.26 and a decline of enzymatic assay values to about 70 % purity.

1,3,5-Trimethoxybenzene (TMB) as a new quencher for preserving redox-labile disinfection byproducts and for quantifying free chlorine and free bromine

Abstract: Sodium sulfite, sodium thiosulfate, and ascorbic acid are commonly used to quench free chlorine and free bromine in studies of disinfection byproducts (DBPs) in drinking water, wastewater, and recreational water. The reducing capabilities of these quenchers, however, can lead to the degradation of some redox-labile analytes. Ammonium chloride, another common quencher, converts free chlorine into monochloramine and is therefore inappropriate for analytes susceptible to chloramination. Herein, we demonstrate the utility of 1,3,5-trimethoxybenzene (TMB) as a quencher of free chlorine and free bromine. The reactivity of TMB toward free chlorine was characterized previously. The reactivity of TMB toward free bromine was quantified herein (kHOBr,TMB = 3.35 × 106 M−1 s−1) using competition kinetics. To explore the feasibility of TMB serving as a free halogen quencher for kinetic experiments, chlorination of 2,4-dichlorophenol, bromination of anisole, and chlorination and bromination of dimethenamid-P were examined. Although TMB does not react with free chlorine or free bromine as quickly as do some (but not all) traditional quenchers, there was generally no significant difference in the experimental rate constants with TMB (relative to thiosulfate) as the quencher. By monitoring the chlorination and bromination products of TMB, free halogen residuals in quenched samples were quantified. Furthermore, TMB did not affect the stabilities of DBPs (e.g., chloropicrin and bromoacetonitriles) that otherwise degraded in the presence of traditional quenchers. TMB could, therefore, be an appropriate quencher of free chlorine and free bromine in aqueous halogenation experiments involving redox-labile analytes and/or when selective quantification of residual free halogens is desired.