Bromine vapor pressure

Safety risks and the environmental impact are of major importance for the practical success of bromine storage system. The nonaqueous polybromide complexes in general show excellent physical properties, such as good ionic conductivity (0.1-0.05 Qcirf1), oxidation stability (depending on the nature of the ammonium ion), and a low bromine vapor pressure. The concentration of active bromine in the aqueous solution is reduced by formation of the complex phase up to 0.01-0.05 mol/L, hence ensuring a decisive decrease of selfdischarge. 

Figure 2 demonstrates that the bromine vapor pressure over a complex phase remains remarkably low with increasing temperature and is not a critical factor restricting battery operation. Even at -60 °C, vapor pressures of Br2 reaching only a few percent of the atmospheric pressure and that of elemental bromine are obtained. 

If the catalytic HBr oxidation reactor is required to serve as a central facility for recycling a variety of waste HBr streams and conditions that combust all of the organic contaminants cannot be discovered, then further bromine purification operations are probably required. The simplest operation is distillation of the bromine. Due to the high bromine vapor pressure, bromine distillation can be accomplished using relatively small equipment. This is expected to be a highly effective method of purification, particularly where the boiling points of any contaminants are greater than 10°C different from that of bromine. In other applications, absorption or extraction may be needed. 

A possible destruction upon impact of zinc-halogen batteries might lead to the release of chlorine gas or bromine liquid and vapor. A study of the effects of spilling a full load of chlorine hydrate on hot concrete concluded that the probability of lethal accidents appears to be no more serious than that caused by gasoline fires in ICE-powered cars. The bromine vapor pressure above the organic complex is lower than that of chlorine above chlorine hydrate its lethal dose, however, is smaller and the spill cleanup and dispersion problems may be more severe. 

The chemical species present in the electrolyte are actually more complex than that described. In solution, elemental bromine exists in equilibrium with bromide ions to form polybromide ions, Br, where = 3, 5, 7. Aqueous zinc bromide is ionized, and zinc ions exist as various complex ions and ion pairs. The electrolyte also contains complexing agents which associate with polybromide ions to form a low-solubility second liquid phase. The complex reduces the amount of bromine contained in the aqueous phase 10 to 100-fold, which, in addition to the separator, also reduces the amount of bromine available in the eeU for the self-discharge reaction. The complex also provides a way to store bromine at a site remote from the zinc deposits and is discussed further in the next section. Salts with organic cations such as iV-methyl-iV-ethylmorpholinium bromide (MEMBr) are commonly used as the complexing agents. One researcher has proposed a mixture of four quaternary ammonium salts for use in zinc/bromine batteries. The proposed electrolyte has favorable properties with regard to aqueous bromine concentration, resistivity, and bromine diffusion and does not form solid complexes at low temperatures (5°C and above). Complexes with quaternary ammonium ions are reversible and also have an added safety benefit due to a much reduced bromine vapor pressure (see Sec. 35.6). 

Previously studied possibilities for bromine storage systems are hsted in Table 7.1. The widely known reduction of the Bt2 vapor pressure by formation of adducts with various carbon materials results from strong chemisorption interactions and has been investigated in the case of activated carbon [4]. Adducts containing up to 85wt% Br2 were reported to be stable at ambient temperature however, considerable equilibrium bromine vapor pressures were found. 

Bromine Trifluoride. Bromine trifluoride is a colorless Hquid. The commercial grade is usually amber to red because of slight bromine contamination. The molecule has a distorted T stmeture (26). Infrared spectral data (26—30), the uv-absorption spectmm (31), and vapor pressure data (32) may be found in the Hterature. 

Bromine Pentafluoride. Bromine pentafluoride is a colorless Hquid having the molecular stmeture of a tetragonal pyramid (5). The index of refraction is 1.3529 (33). Infrared spectra (13,34), the uv-absorption spectmm (35), and vapor pressure data (11) are all available. 

Health and Safety Factors and Regulations. Iodine is much safer to handle at ordinary temperatures than the other halogens because iodine is a soHd and its vapor pressure is only 1 kPa (7.5 mm Hg) at 25°C, compared to 28.7 kPa (215 mm Hg) for bromine and 700 kPa (6.91 atm) for chlorine. When handling properly packed containers, usual work clothes are sufficient. In the handling of soHd, unpacked iodine, mbber gloves, mbber apron, and safety goggles are recommended. Respirators or masks are also recommended. 

Organic compounds of bromine usually resemble their chlorine analogues but have higher densities and lower vapor pressures. The bromo compounds are more reactive toward alkaUes and metals brominated solvents should generally be kept from contact with active metals such as aluminum. On the other hand, they present less fire hazard one bromine atom per molecule reduces flammabiUty about as much as two chlorine atoms. 

The value of Ay for gas hydrates of Structure I reported in Table II could thus be derived30 with the aid of Eq. 25 with v — 3/23 from the composition Br2 8.47 H20 of the bromine hydrate following from Miss Mulders accurate study19 of the system Br2-f-H20 cf. Section III.C.(l). It should be possible to derive the value of Ay for hydrates of Structure II in the same way from the equilibrium composition of the SFe hydrate unfortunately the equilibrium composition of this hydrate is not known. The value of Ay for hydrates of Structure II reported in the table has been derived from the vapor pressure of the SF6 hydrate using some further assumptions (cf. Section III.C.(2)(b)). 

The best method for determining Afx for Structure II would be to measure the composition of the equilibrium hydrate of SF. Since the SFt molecules only fit into the larger cavities, the value of A pi immediately follows from this composition by virtue of Eq. 25", in the same way as Ap for Structure I followed from the composition of bromine hydrate. Unfortunately, the composition of SF6 hydrate has never been measured, and thus it had to be derived in an indirect manner from the vapor pressure of this hydrate. 

The two basic requirements for efficient bromine storage in zinc-bromine batteries, which need to be met in order to ensure low self-discharge and more over a substantial reduction of equilibrium vapor pressure of Br2 of the polybromide phase in association with low solubillity of active bromine in the aqueous phase. As mentioned by Schnittke [4] the use of aromatic /V-substitucnts for battery applications is highly problematic due to their tendency to undergo bromination. Based on Bajpai s... 

Figure 2. Vapor pressures of bromine/quaternary ammonium salt complexes elemental Br2, Me4N+ Br, MEMBr, Oct,MeN Cl. From Ref. [59J.

Storage of bromine by formation of a polybromide phase with a lowering of the vapor pressure by more than one magnitude, to at least 10% of the value of Br2 at maximum, is the basic requirement for safe application in zinc-flow batteries [91, 92]. No information is available concerning negative health effects of the com-plexing agents MEM and MEP. 

E6.6 The partial pressure of Bri above a (. 1CCI4 +. v Bn) solution is 1.369 kPa. The composition of the solution is a = 0.0250. The vapor pressure of pure bromine at the same temperature is 28.4 kPa. Assume a Raoult s law standard state for bromine and calculate the activity coefficient of Br2 in the solution. 

Br(g) from the thermodynamic data provided in Appendix 2A. (b) What is the vapor pressure of liquid bromine (c) What is the partial pressure of Br(g) above the liquid in a bottle of bromine at 25°C (d) A student wishes to add 0.0100 mol Br2 to a reaction and will do so by filling an evacuated flask with Br2 vapor from a reservoir that contains only bromine liquid in equilibrium with its vapor. The flask will be sealed and then transferred to the reaction vessel. What volume container should the student use to deliver 0.010 mol Br2(g) at 25°C ... 

Although molecular bromine is a liquid at 298 K, 1 bar, it has a significant vapor pressure at this temperature. Calculate this vapor pressure in torr. 

Tittlemier, S.A., Halldorson, T., Stern, G.A., and Tomy, G.T. Vapor pressures, aqueous solubihties, and Henry s law constants of some brominated flame retardants. Environ. Toxicol. Chem., 21(9) 1804-1810, 2002. 

Black crystaUine solid exists in two modifications stable black needles known as alpha form that produces ruby-red color in transmitted light, and a labile, metastable beta modification consisting of black platelets which appear brownish-red in transmitted light density of alpha form 3.86 g/cm at 0°C density of beta form 3.66 g/cm at 0°C alpha form melts at 27.3°C, vapor pressure being 28 torr at 25°C beta form melts at 13.9°C hquid iodine monochloride has bromine-hke reddish-brown color hquid density 3.10 g/mL at 29°C viscosity 1.21 centipoise at 35°C decomposes around 100°C supercools below its melting point polar solvent as a hquid it dissolves iodine, ammonium chloride and alkali metal chlorides hquid ICl also miscible with carbon tetrachloride, acetic acid and bromine the solid crystals dissolve in ethanol, ether, acetic acid and carbon disulfide solid ICl also dissolves in cone. HCl but decomposes in water or dilute HCl. 

Heavy sdvery-white liquid does not wet glass forms tiny globules the only metal that occurs at ordinary temperatures as a hquid and one of the two hquid elements at ambient temperatures (the other one being bromine) density 13.534 g/cm3 solidifies at -38.83°C vaporizes at 356.73°C vapor pressure 0.015 torr at 50°C, 0.278 torr at 100°C and 17.29 torr at 200°C critical temperature 1,477°C critical pressure 732 atm critical volume 43cm3/mol resistivity 95.8x10 ohm/cm at 20°C surface tension 485.5 dynes/cm at 25°C vis-... 

Very recently, Hu et al. claimed to have discovered a convenient procedure for the aerobic oxidation of primary and secondary alcohols utilizing a TEMPO based catalyst system free of any transition metal co-catalyst (21). These authors employed a mixture of TEMPO (1 mol%), sodium nitrite (4-8 mol%) and bromine (4 mol%) as an active catalyst system. The oxidation took place at temperatures between 80-100 °C and at air pressure of 4 bars. However, this process was only successful with activated alcohols. With benzyl alcohol, quantitative conversion to benzaldehyde was achieved after a 1-2 hour reaction. With non-activated aliphatic alcohols (such as 1-octanol) or cyclic alcohols (cyclohexanol), the air pressure needed to be raised to 9 bar and a 4-5 hour of reaction was necessary to reach complete conversion. Unfortunately, this new oxidation procedure also depends on the use of dichloromethane as a solvent. In addition, the elemental bromine used as a cocatalyst is rather difficult to handle on a technical scale because of its high vapor pressure, toxicity and severe corrosion problems. Other disadvantages of this system are the rather low substrate concentration in the solvent and the observed formation of bromination by-products. 

Polonium tetrabromide is a bright red solid which melts, in bromine vapor, at about 330°C (7, 75), and boils at 360°C/200 mm 75). It is prepared by heating polonium metal in bromine vapor at 200 mm pressure for 1 hour at 250°C (7, 75) or, more rapidly, in a stream of nitrogen saturated with bromine vapor at 200°-250°C, and by heating polonium dioxide in hydrogen bromide or by evaporating a solution of polonium(IV) in hydro-... 

Polybrominated Diphenyl Ethers. In air, highly brominated PBDEs, which have low vapor pressures and exist in the particulate phase, will be removed from the atmosphere by wet and dry deposition. 

Tittlemier SA, Tomy GT. 2000. Vapor pressure of six brominated diphenyl ether congeners. Organohalogen Compoimds 47 206-209. 

Tittlemier SA, Tomy GT. 2001. Vapor pressures of six brominated dipheyl ether congeners. Environ Toxicol Chem 20(1) 146-148. 

Br2 (c). Regnault2 measured directly F = —2.53-7. This value is in accord with the heat of sublimation computed from the vapor pressure data on solid bromine of Braune,1 Isnardi,1 Ramsay and Young,1 Cuth-bertson and Cuthbertson,1 Henglein,2 and Henglein, Rosenberg, and Much-linski.1 See also Rideal.1... 

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