A series of studies on the acidity of AlCl 3 -1-ethyl-3-methylimidazolium chloride (EMIC) melts buffered with alkali metal chlorides were carried out. The solubility of HCl, a strong Brønsted acid in these melts, was measured in melts buffered with LiCl, NaCl, and KCl. The solubility of HCl in all three melts is 450-475 mM under 1 atm of HCl, approximately the same as that in the acidic (AlCl 3 -rich) melts. The relative solubility products of LiCl, NaCl, and KCl were measured, and it was found that K sp (NaCl)/K sp (LiCl) ) 72 ( 6 and K sp (KCl)/K sp -(NaCl) ) 1000 ( 400. It is likely that the differences in the acidity of HCl in the various melts are due to the differences in the solubility product of the relevant alkali metal chlorides. These ratios are consistent with the results of previous studies on the acidity of HCl in the melts. The concentrations of the strongly Lewis acidic Al 2 Cl 7ion in melts buffered with LiCl were measured using an aluminum electrode. The results of the potentiometric work indicate that a melt containing 1 M Li + (approximately n AlCl3 /n EMIC ) R ) 1.25:1 prior to buffering) would contain about 200 µM Al 2 Cl 7 -. This corresponds to a solubility product of about (1.5 ( 0.5) × 10 -12 M 2 . The liquid junction potentials between unbuffered and buffered melts were found to be about 49 mV × ([Li + ]/M). These results are related to previous work on the acidity of HCl in these melts, and it is shown that it is possible to explain many of the acidity and latent acidity results on the basis of the solubility products of the alkali metal chlorides.

The Brønsted acidity of HCl in neutral buffered AlCl3:1-ethyl-3-methylimidazolium chloride (EMIC) melts has been compared to the Brønsted acidity of HCl in acidic (55 mol % AlCl3) melts. The acidities were compared using the spectrophotometric indicator method. Arenes were used as the weak indicator bases. The acidity of HCl in the neutral buffered melts was found to be dependent on both the type of buffering agent (LiCl, KCl, and NaCl) and on the concentration of the metal cation in the melt. An enhancement in Brønsted acidity of HCl is observed in the neutral buffered melts, although to a lesser degree than that in the acidic melts. A Hammett acidity function was determined for a NaCl (originally 55 mol % AlCl3) buffered melt and a LiCl (originally 55 mol % AlCl3) buffered melt. For a HCl (1 atm)/NaCl/AlCl3:EMIC (originally 55 mol % AlCl3) buffered melt, H o = −11.3. H o = −12.7 for a HCl (1 atm)/LiCl/AlCl3:EMIC (originally 55 mol % AlCl3) buffered melt.

The mechanism of the reaction: I 2 + 2BrO3---, Br2 + 2103-in aqueous solution (pH 1.5 to 2.5) at 25 "C has been investigated. It is found to go in four stages. Firstly, there is an induction period during which the acidified bromate produces a catalyst (probably HOBr) for the next stage. However, iodide ions, if present, destroy this catalyst. Secondly, iodine reacts by the overall equation, 12 + Br03--+ IBr + IO3-, at a rate proportional to [H+]2[Br03-12. Thirdly, the iodine bromide reacts by the overall equation, 31Br + 2Br03-+ 3H20 -+ 5Br-+ 3103,-+ 6H+, at a rate proportional to I[Br:l2PrO3-]2.Finally bromide and bromate ions react to give brom~ne. Mechan~sms are suggested for the various stages, and some of the rate constants are evaluated.Canadian Journal of Chemistry, 46, 279 (1968) Iodine is known (1) to displace bromine from and Lomb Spectronic 505. The other analytical methods aqueous bromate solutions, although, of course, consisted of extracting the reacting mixture with carbon tetrachloride, and estimating the halogen extracted the is the other way around in either spectrophotometrically, or by addition of aqueous halide solutions. The total reaction, which is potassium iodide and titration with sodium thiosulfate. Iodine-thiosulfate titrations were also used to standardize I2 + 2Br03--+ BrZ + 2103-, the stock solutions of iodine and sodium bromate. The can be expected to go in a number of steps, since it is unlikely that so many oxygen atoms would be transferred in a single stage. It seemed therefore to be of interest to investigate the mechanism of this reaction, especially as it might be expected to yield more information on oxy-halogen reactions in general. As will be seen in what follows, the reaction did indeed prove to be complicated, and although the mechanism has been elucidated to a considerable extent, only rather speculative proposals can be put forward for certain parts of the reaction. ExperimentalThe experiments in general consisted of mixing aqueous solutions of iodine and sodium bromate, with added phosphoric acid and sodium dihydrogen phosphate as a DH buffer. The DH of the reaction mixture was in the ;ange of 1.5 to i.5; and was measured on a Beckman 101900 Research pH meter using a glass electrode, Beckman 40498, in the usual way. The pH reading was calibrated by means of a potassium tetroxalate buffer (pH 1.68) but various dilute HC1 solutions of pH about 1.0 to 1.5 were checked against this buffer. It was assumed that the HC1 was completely ionized, and consequently these measurements gave a correction which enabled pH readings to be converted to hydrogen ion concentrations. Sodium nitrate was also added to the reaction mixtures to control the ionic strength, which was always close to 0.15. The reacting solutions were kept in a thermostat at 25.0 =! = 0.1 "C. The reaction was chiefly followed by measurements of optical density on a Beckman DU. spectrophotometer. In some cases spectra over the range 200 to 500 m l were measured on a Bausch substances used were all of analytica...

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