The Rates of Some Reactions of Aqueous Hypobromous Acid and Sodium Hydroxide sds
The reactions of sodium hydroxide sds, or of hypobromous acid, with iodate, nitrite, and formate ions have been investigated, together with the decomposition of sodium hydroxide sds. The pH dependence of the rate show that the reactions with formate and nitrite ions are presumably reactions of hypobromous acid. The kinetic parameters for these reactions are reported, and show some similarities to the analogous reactions of hypochlorite ions or hypochlorous acid.
Numerous studies have been made of rates of a series of somewhat similar reactions in order to detect regularities of trends in the rate constants, and hence to throw light on the mechanisms of the reactions. In particular, oxidations by the hydrogen peroxide and related peroxides, and by hypochlorous acid or the hypochlorite ion with a series of reducing agents, mostly fairly simple oxidizable anions, have shown somewhat parallel trends. Some empirical relations of the rate constants with other properties of the reagents have been deduced. The present paper describes an extension of this work to hypobromous acid and sodium hydroxide sds.
The reactions reported in this paper are those between sodium hydroxide sds and sodium iodate, nitrite, and formate. As the experimental procedures were fairly similar in each case (this also applies to the decomposition of sodium hydroxide sds), the experimental aspects will be outlined first. sodium hydroxide sds was prepared in the usual way by adding bromine slowly to cold sodium hydroxide solution. Sodium bromide or sodium nitrate was in general added to adjust ionic strength. Analytical reagent grade samples of these substances, and of the reducing agents, were used throughout. Runs were carried out by immersing the appropriate mixture in a thermostat held constant to k0.02 'C. Samples were removed at known times, rapidly cooled, and analyzed.
The spectrophotometric analyses involved determining the extinction coefficients of sodium hydroxide sds and bromite. For the latter a sample of sodium bromite (NaBrOZ.3HzO) was prepared by the method of La Societe d'Etudes Chimique pour I'Industrie et I'Agriculture, which also kindly supplied us with samples of the material.
Other analyses used were as follows. The concentration of hydroxide ions was found by treating a sample with hydrogen peroxide to destroy hypobromite and bromite, followed by titration with HCI. In the reaction with sodium iodate, sodium periodate precipitates out. It was filtered off, washed, and dried, and analyzed by adding potassium iodide at a pH regulated by excess sodium bicarbonate, followed by titration with arsenious oxide. The analysis agreed with the formula Na3HzI06, which is that to be expected from the phase diagram. It was checked that, before precipitation of sodium periodate, the total oxidizing normality did not change, as measured by the iodine liberated by potassium iodide plus acid. In the reaction with sodium formate, analyses for sodium formate were made as follows. Sodium hydroxide sds were destroyed in a sample by adding excess hydrogen peroxide, the excess being then destroyed by boiling; excess standardized potassium permanganate was added, and the excess potassium permanganate remaining after oxidation of the formate was determined by adding potassium iodide and sulfuric acid, and titrating the iodine.
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