Bromate-sulfite reaction

Nagy, I. P. Keresztessy, A. Pojman, J. A. 1995a. Periodic Convection in the Bromate-Sulfite Reaction A Jumping Wave , J. Phys. Chem. 99, 5385-5388. 

A Landolt pH-oscillator based on a bromate/sulfite/ferrocyanide reaction has been developed with a room temperature period of 20 minutes and a range of 3.1periodic oscillations in volume in a pH responsive hydrogel. A continuously stirred, constant volume, tank reactor was set-up in conjuction with a modified JKR experiment and is used to show that the combination of a pH oscillator and a pH responsive hydrogel can be used to generate measurable force. 

Indeed, PAAc cryogels coupled with a bromate oscillator oscillated between swollen and collapsed states [31]. The reactions of bromate, sulfite, and ferrocyanide ions were conducted in an open continuously stirred tank reactor. Four feed solutions (potassium bromate, sodium sulfite, potassium ferrocyanide, and sulfuric acid) were supplied continuously to the reactor, during which the pH of the reaction solution was monitored as a function of time. The flow rate of the feed solutions is an important parameter in determining the extent of pH oscillations. In Fig. 21, pH versus time plots are shown for four different reduced flow rates k, defined as the flow rate of the feed solutions divided by the reaction volume. It is seen that the pH of the solution oscillates between 6.2-6.9 and 3.2-3.8. The dissociation degree a of a weak electrolyte relates to pH by ... 

Eager, M. D. Santos, M. Dolnik, M. Zhabotinsky, A. M. Kustin, K. Epstein, I. R. 1994. Dependence of Wave Speed on Acidity and Initial Bromate Concentration in the Belousov-Zhabotinsky Reaction-Diffusion System, J. Phys. Chem. 98, 10750-10755. Edblom, E. C. Luo, Y. Orban, M. Kustin, K. Epstein, I. R. 1989. Kinetics and Mechanism of the Oscillatory Bromate-Sulfite-Ferrocyanide Reaction, J. Phys. Chem. 93, 2722-2727. 

Boissonade etal. consider the chemoelastodynamics of responsive gels in Chapter 9. This chapter is devoted to the spontaneous generation of mechanical oscillations by a responsive gel immersed in a reactive medium away from equilibrium. Two important cases are considered. In the first case, the chemomechanical instability is mainly driven by a kinetic instabiUty leading to an oscillatory reaction. The approach is applied to the BZ reaction. The second case is a mechanical oscillatory instability that emerges from the cross-coupUng of a reaction-diffusion process and the volume or size responsiveness of the supporting material. In this case, there is no need for an oscillatory reaction. Bistable reactions, namely, the chlorite-tetrathionate (CT) and the bromate-sulfite (BS) reactions, were chosen... 

Zinc forms a wide variety of other salts, many by reaction with the adds, though some can only be obtained by fusing the oxides together. The salts include arsenates (ortho, pyro, and meta), the borate, bromate, chlorate, chlorite, various chromates, cyanide, iodate. various periodates, permanganate, phosphates (ortho, pyro, meta, various double phosphates 1. die selenate, selenites, various silicates, fluosilicate. sulfate, sulfite, and duocyanate. 

C4H604Pb Pb(CH3COO)2 Violent reaction with bromates, carbonates, phenols, phosphates potassium bromate (possible explosion). Contact with strong acids forms acetic acid. Reacts with strong oxidizers. Incompatible with alkalis, alkylene oxides, ammonia, amines, carbonates, citrates, cresols, chloral hydrate, chlorides, epichloro-hydrin, hydrozoic acid, isocyanates, methyl isocyanoacetate, phenol, phosphates, potassium bromate, resorcinol, salicylic acid, sodium salicylate, sodium peroxyborate soluble sulfates sulfites, tannin, tartrates, some tinctures triiutrobenzoic acid, urea nitrate. In the heat of fire lead oxides and acetic acid fumes are formed. 

The selectivity of the test is quite limited, even compared to the specificity seen in the identification test for chlorides. In the identification three criteria have to be fulfilled to qualify for a positive reaction. The unknown should give a white (curdled) precipitate formed upon addition of silver nitrate, which is insoluble in dilute nitric acid but redissolves in ammonia. In the limit test 2.4.4. Chlorides any substance capable of giving a white or weakly colored precipitate in dilute nitric acid will give a response like chloride, and this should be remembered in case of an xmexpected result. For the sake of example the following ions and substances are capable of giving a false positive reaction bromide, iodide, bromate, iodate, sulfite, chlorate, oxalate, and benzoate. In addition to this a variety of more complex organic substances are likely to precipitate, for example, alkaloids. 

The reactions were conducted in an open continuously stirrer tank reactor (CSTR) at room temperature, with a peristaltic pump supplying the feed solutions of potassium bromate, sodium sulfite, potassium ferrocyanide and sulphuric acid and also pumping out bulk solution to keep the volume in the CSTR constant. Measurements of pH were made using a standard gel-filled probe, and the output from the meter monitored by a PC. A typical pH profile is shown in Figure 1. 

Bromate and iodate salts are prepared on a much smaller scale than chlorates. Under appropriate conditions, these ions undergo oscillating chemical reactions known as chemical clocks. The best known clock reaction is observed when an acidified solution of sodium sulfite (Na2S03) is mixed with an excess of iodate in the presence of starch indicator. After a suitable induction period allowing for sodium sulfite reduction of iodate to iodide [Eq. (44)], the blue, starch-iodine color periodically appears and disappears as the iodide is oxidized to iodine [Eq. (45)], and the iodine is reduced back to iodide [Eq. (46)]. 

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