As bromate can readily and accurately be measured iodometrically it is most suitable to reduce the determination of the bromide ion to the measurement of bromate. In this case the equivalent weight of the bromide ion is the lowest, thus slight amounts can also be determined very accurately. On carrying out the oxidation with chlorine the estimation has further advantages: a) The oxidation by means of chlorine can be performed readily, its excess can be easily removed, and in the course of the oxidation no products form interfering with the procedure. b) Even large amounts of the chloride ion do not either interfere with the determination. c) On using this method we meet with the least disturbances, thus their elimination is greatly simplified. The determinations of bromide -based on oxidation with chlorine -hitherto reported in the literature can be characterized briefly as follows: The basic method by means of boric acid-alkali buffer was elaborated by VAN DEXZ MEULEN~. Independently of the latter author one of us (SZAB~)~ carried out the oxidation of bromide in the presence of potassium hydrocarbonate. D'ANs AND H~FER~ used primary and sesondary phosphate as buffer, Their experiments were checked by KOLTHOFF AND YUTZ+. WILLARD AND HEYN~ employed an acetate buffer, ALICINO, CRICKENBERGER AND REYNOLDS~ sodium hydroxide phosphate. DOERING's' work ought also to be mentioned, he adjusted the medium by addition of calcium carbonate. The analyses carried out with the methods mentioned above did not always give satisfactory results. It seemed reasonable to reinvestigate the exact conditions of the oxidation of bromide in order to be able to work out a procedure which can be satisfactorily applied. The authors of the enumerated methods do not furnish particular data concerning the oxidation steps of bromide ion, whereas this is of fundamental significance also from the analytical point of view. At any rate the equation undoubtedly reveals the dependence of the oxidation upon the PH. Referetlces p. 216. VOL. 6 (x952) DETRRMINATION OF BROMIDE ION 209 (I) Br-+ 3 Cl, +.3 H,O = BrO-, + 6 Cl-+ 6 H+ On carrying out approximative calculations -utilizing the oxidation potentials it can be shown, according to the above equation, thti in a medium of PH = 0, the conversion ratio is