Enthalpimetric determinations with sodium hypobromit

Abstract

The applicability of sodium hypobromite as a reagent in enthalpimetric determinations of various organic and inorganic compounds is reviewed. Using this method it is possible to determine various oxidizable nitrogen and sulphur compounds, e.g. ammonium salts, urea, c~-amino acids, sulphides, sulphites, thiosulphates, organic compounds with sulphidic sulphur, aromatic amines, mono-and polyphenols, and other compounds. Determinations are sufficiently precise and sensitive. The enthalpy changes of these reactions are approximately 10 z to 10 z kJ mole -1. Suggested determinations are advantageous due to their simplicity, quickness and possible automatization of measurements.Solutions of alkali metal hypobromites, which may be easily prepared by the action of bromine upon aqueous solutions of alkali metal hydroxides, are frequently applied as oxidants in quantitative analysis. During these oxidationreduction reactions hypobromites change into bromides according to Eq. (1) [1-51:At first individual papers were published referring to the application of hypobromites in titrimetric determinations [6][7][8][9]. Later, Jellinek and Kresteff [10] suggested hypochlorites as a general agent for oxidimetric titrations. However, great problems arose when solutions of hypochlorites and hypobromites were used for titrations, because of their instability. Another problem in these titrations was the selection of a suitable method for the indication of the equivalence point. Many authors studied the application of hypochlorites and hypobromites for titrimetric analyses. Kolthoff and Stenger [I 1] suggested application of a more stable solution of calcium hypochlorite instead of unstable alkali metal hypochlorites, and addition of potassium bromide to the titrated solution so that hypobromite formed during the titration exhibited oxidative action. In most titrations it is recommended to add excessive amount of titrant (= reagent) to the titrate (= analyzed substance) and to re-estimate the excess of titrant by means of direct or indirect titration. Many authors studied various methods of application of hypochlorites and hypobromites in titrimetric analysis and developed various methods of assays with these reagents (see surveys of literature dealing with oxidation-reduction titrations [2,3]).

A rapid enthalpimetric method for the assay of the reducing sugar content of some soft drinks

“…If the periodate complex [KTCu(IO6)2] or the tellurate complex [K9Cu(TeO6)2] are used, the redox potential of the Cu(III)/Cu(II) system in alkaline solution is 1.8 V [10], hence titrations with Cu(III) solutions are usually done in an alkaline medium, mostly in potassium hydroxide solutions. Both direct and indirect determinations of Cu(III) have been reported and the possible use of Cu(III) for the determination of some mono-and di-saccharides has also been reported [11].…”