Rubidium bromide

Rubidium bromide [7789-39-1 ] M 165.4, m 682°, b 1340°, d 3.35. A white crystalline powder which crystallises from H2O (solubility. 50% in cold and 67% in boiling H2O to give a neutral soln). Also crystd from near-boiling water (0.5mL/g) by cooling to 0°. 

RbBr RUBIDIUM BROMIDE 78.4584 -1.4856E+04 -2.2965E+01 5.3426E-03... 

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... 

H. Topsoe found the refractive indices of crystals of potassium bromide to be 1 5546 for the C-line 1"5593 for the D-line 15715 for the F-Iine and 1-5814 for the H-line. Similar results were obtained by M. SprockhofE, and for rubidium bromide, 1 5483 for the C-line 1 5528 for the Z)-line and 1 5646 for the F-line. For the caesium bromide, M. SprockhofE obtained T6924 for the C-line 1 6984 for the D-line and 1 7126 for the F-line. The refractive index /u. of soln. of lithium, sodium, and potassium bromides have been determined by G. P. Baxter and for potassium bromide soln. by A. H. Borgesius,27 at 18° for the D-line. The fractional increase in the refractive index (/u.—p0)/w of soln. containing w per cfent. of the salt per litre, is... 

M. le Blanc gave the refractive indices of solii. of potassium and rubidium bromides as 1 5593 and 1 5533 respectively, when the densities are 2"738 and 3 314 respectively. Hence the refraction eq. of potassium bromide by Gladstone and Dale s formula is therefore 24 32 and by Lorentz and Lorenz s formula 14-05 the corresponding values for rubidium bromide are27"62 and 15"98. The mol. refractions of potassium bromide in soln. by the two formulae are respectively 25"11 and 14 70 and of rubidium bromide in soln., 27 85 and 16 33. The mol. refractions of these salts are therefore greater in soln. than in the solid form. Crystals of potassium bromide, says H. Marbuch, exhibit optical activity. A. S. Newcomer found that sodium chloride was the only salt relatively soluble and yet capable of emitting fluorescent rays in the mid-ultra-violet region of the spectrum under the influence of X-rays. 

RbBr Rubidium bromide Rubidium(I) bromide 8. AICI3 Aluminum trichloride0 Aluminum(lll) chloride0... 

Since the sum of the ionic radii is known (from x-ray studies), both radii may then be evaluated. Similarly, if the S values for the argon, krypton, and xenon structures are known, the interionic distances in KC1, RbBr, and Csl may be used to calculate ionic radii for K+, Rb+, Cs4, Cl, Br, and I . The values for cesium and iodide ions must be regarded cautiously (for, as we shall see presently, the structure of the cesium halides is different from that of the other alkali halides) but the radii of the retnaining ions fit into a self-consistent system. Thus, adding from sodium fluoride (0.95 k) to R Br from rubidium bromide (1.95 A) yields a sum not greatly different from the observed interionic distance in solid sodium bromide (2.98 A). 

Rubidium bromide, RbBr.—The methods for the formation of the bromide are similar to those employed for the production of rubidium chloride. The salt is colourless, crystallizes in cubes, and is stated to melt at 681° C.14 and 683° C.,1S and to boil at 1350° C.16 The vapour-pressure in atmospheres is given by the expression 16... 

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