Alkali bromides

Sodium bromide [7647-15-6] NaBr, the most common and available alkali bromide, is a salt of hydrobromic acid (see Bromine compounds). Sodium bromide crystallines from aqueous solution as a 3466-08-5] NaBr-2H20, below 51°C. Above 51°C, it crystallines as the anhydrous compound. 

Many other applications of multi-photon absorption spectroscopy have meanwhile been reported in photochemistry and also in solid state physics, for instance, a new assignment of the band gap in alkali bromides by Froehlich et al Some further examples will be discussed in Section 111.10). 

Silver bromide is prepared by double decomposition reaction. An aqueous solution of alkali bromide, such as sodium or potassium bromide, is slowly added to an aqueous solution of sdver nitrate ... 

The increase in the solubility of bromine in soln. of ammonium salts is very marked, as is also the case with the alkali chlorides. The case with the alkali bromides is specially interesting. The solubilities by F. P. Worley are indicated in Table IX. The marked increase in the solubility of bromine in soln. of potassium bromide was attributed by M. Roloff to the formation of molecules of KBr3. He shook up a soln. of bromine in carbon disulphide with water and with an aq. soln. of potassium biomide, and measured the concentration of the bromine in the two layers. M. Wildermann has shown that the density of bromine vapour over a soln. of potassium bromide sat. with bromine is the same as over water sat. with bromine, indicating that the cone, of the free bromine in all the aq. soln. is the same, and any excess in the presence of potassium bromide must be united with the potassium bromide. All the bromine dissolved by a soln. of potassium bromide can be removed... 

The history of the bromides dates from the discovery of bromine by A. J. Balard1 in 1824. He prepared potassium bromide by the action of bromine on potash lye, and calcined the residue remaining on evaporating the product to dryness. The bromine in sea-water may be present as alkali bromide, but more probably as magnesium bromide. It is, however, uncertain how the bromides are distributed and similar remarks apply to the bromides present in spring and mine waters. Potassium bromide is used in chemical laboratories medicinally in some nervous diseases and in photography. 

The preparation oi the alkali bromides.—While V. Merz and W. Weith 2 found that metallic sodium reacts very slowly with bromine such that even after the two elements have been kept for 8 hrs. at 200°, the conversion of sodium into the bromide is but superficial potassium, caesium, and rubidium unite with bromine more quickly, forming the alkali bromide. The bromides are also formed when hydro-bromic acid is neutralized with the alkali hydroxide or carbonate, and the soln. evaporated. This method, for example, has been used for preparing rubidium bromide, RbBr. C. Chaubrie and N. N. Beketofi made a soln. of caesium bromide, CsBr, by the double decomposition of caesium sulphate, and barium bromide. P. Klein 3 made lithium bromide by digesting calcium bromide with lithium carbonate... 

The mol. vol. are indicated in Table XXIV. Potassium bromide does not form mixed crystals with the sodium salt. K. Fajans and H. Grimm studied the mol. vol. of the alkali bromides. For the effect of press, on the sp.gr. see the alkali chlorides. 

The coefficient of thermal expansion (linear) for crystals of potassium bromide, by H. Fizeau, is a=0 000042007 at 40°. The coeff. of cubical expansion of crystals of the alkali bromides, by G. P. Baxter and C. C. Wallace, are ... 

The diffusion coefficient19 of sodium bromide is 0-86 at 10° for soln. of sodium bromide containing 2 9 mols. per litre and for iV-soln. of potassium bromide, 1 13 per sq. cm. per day. The capillary constant20 of fused sodium bromide is o2=4 08, and potassium bromide, a2=4 49 sq. mm. The surface tensions are respectively 49"0 and 484 dynes per cm. W. Herz and G. Anders 21 measured the viscosities of soln. of alkali bromides and F. Korber the effect of press, on the viscosities as indicated in Table XIX. 

Ammonium bromide dissolves in various organic solvents. Ethyl alcohol at 15° dissolves 2-97 per cent, of the salt at 19°, 3 12 per cent. and at 78°, 9 50 per cent. Methyl alcohol at 19° dissolves 11-1 per cent. and ether (sp. gr. 0729) dissolves 0123 grm. of salt per 100 grms. of solvent. G. Tammann and W. Hirsch-berg have measured the sp. gr. of alcoholic soln. and measurements on the lowering of the f.p. and the electrical conductivities by G. Carrara and by H. C. Jones and C. L. Lindsay show that the salt is considerably ionized in these soln.—vide alkali bromides. Similar remarks apply to soln. of ammonium bromide in acetone by P. Dutoit and A. Levier, and in formic acid by H. Zanninovich-Tessarin. In the vol. n. 2 q... 

Bromine can function as a solvent. One of the very few metal bromides that has significant solubility in bromine is cesium bromide, 19.3 g/100 g of solution, thus providing a method of separating cesium bromide from the other alkali bromides (12). Aluminum bromide also is reported to have significant solubility in bromine but the published solubility values are not in good agreement (13). Bromine serves as the solvent in some brominations of organic compounds, such as 1,2-diphenylethane (14). 

With the alkali bromides and alkyl ammonium bromides selenium tetrabromide can form crystalline additive compounds of the type MaSeBr6, termed selenibromides. Indeed, by the action of bromine on finely divided selenium in the presence of concentrated hydrobromic acid, a solution is obtained 4 which gradually deposits deep red crystals of hydrogen selenibromide, HaSeBr6. The solution of this body in hydrobromic acid on dilution with water undergoes decomposition with liberation of colloidal selenium. Two reactions probably occur concurrently ... 

The potassium and ammonium selenibromides have been prepared by dissolving selenium dioxide in hydrobromic acid and adding either potassium or ammonium bromide. The selenibromides are orange-red in colour and are decomposed by water into selenious acid, hydrogen bromide and the alkali bromide, yielding colourless solutions.1... 

Br- (g). The electron affinity of Br (g) is calculable by the method of lattice energies. Selecting the crystal RbBr, because Rb+ and Br have exactly the same nuclear structure, and taking the exponent of the repulsive term to be 10, we have computed, for the reaction, RbBr (c) = Rb+ (g)+Br g), Dz= —151.2 whence the electron affinity of Br (g) becomes 87.9. Using the lattice energies of the alkali bromides as calculated by Sherman,1 we have computed the values 89.6, 85.6, 84.6, 83.6, and 89.6, respectively. Butkow,1 from the spectra of gaseous TIBr, deduced the value 86.5. From data on the absorption spectra of the alkali halides, Lederle1 obtained the value 82. See also Lennard-Jones.2... 

Experimental evidence in support of this explanation is the fact that lithium added to a solution of lithium iodide in ethylenediamine dissolves without imparting a blue color to the solution—i.e., reacts immediately to give the amide. By contrast, lithium added to a solution of lithium chloride in ethylenediamine dissolves and imparts a deep blue color to the solution. The catalytic effect of iodide anion may be related to the effect of iodide anion on the electron spin resonance (ESR) absorption of solutions of alkali metals in liquid ammonia. Catterall and Symons (2) observed a drastic change in the presence of alkali iodides but very little change in the presence of alkali bromides or chlorides. They attributed this change to interaction of the solvated electron with the 6 p level of the iodide anion. 

Synthesis of MCM-41 with Additives. The hydrothermal crystallization procedure as described earlier [10] was modified by adding additional salts like tetraalkylammonium (TAA+) bromide or alkali bromides to the synthesis gel [11]. Sodium silicate solution ( 14% NaOH, 27% Si02) was used as the silicon source. Cetyltrimethylammonium (CTA) bromide was used as the surfactant (Cl6). Other surfactants like octadecylltrimethylammonium (ODA) bromide (C,8), myristyltrimethylammonium (MTA) bromide (C,4) were also used to get MCM-41 structures with different pore diameter. Different tetralkylammonium or alkali halide salts were dissolved in little water and added to the gel before addition of the silica source. The final gel mixture was stirred for 2 h at room temperature and then transferred into polypropylene bottles and statically heated at 100°C for 4 days under autogeneous pressure. The final solid material obtained was washed with plenty of water, dried and calcined (heating rate l°C/min) at 560°C for 6 h. 

Freely soluble in water, alcohol, and ether. Aqueous solutions of alkalies decompose it to alkali cyanide and alkali bromide. Pure cyanogen bromide, completely dried by distillation over sodium, may be stored in a desiccator for several months. Impure material decomposes rapidly and tends to explode.1... 

Bromoform1 is obtained in a similar manner if alkali bromide be employed in the presence of alcohol or acetone. Chloroform is produced by employing alkali chloride with acetone. Schering s2 patent in this connection has been worked through and confirmed by Teeple.3 Chloral is produced if alcohol is used in the presence of alkali chloride. ... 

Bromine is used for the production of alkali bromides that cannot be manufactured by the action of caustic soda on bromine because hypo-bromites and bromates are also produced. Thus, the van der Meulen process from the production of potassium bromide involves treating bromine with potassium carbonate in the presence of ammonia. 

Arsenical, and 8. Bromiuretted (Woodhall, Lincolnshire) waters contain small quantities of arsenic and bromine (as an alkali bromide) respectively. 

With traces of alkali bromides and iodides, phosphates of calcium and iron, and silica.2... 

---