Hydrobromic acid, composition

Sandri (15) reported the formation of characteristic crystals with cadmium bromide-hydrobromic acid, bismuth iodide-potassium iodide, and bismuth bromide-hydrobromic acid, with compositions CdBr2 HBr CgHgN 4H 0, HBiI CgHoN, and HBiBr CgHgN, respectively. 

Yellow orthorhombic crystals density 7.6 g/cm decomposes on heating at about 298°C loses its stoichiometric composition at 170°C very slightly soluble in cold water decomposes in hot water soluble in hydrochloric and hydrobromic acids, and alkah cyanide solutions. 

Its solutions in dilute hydrobromic acid are a carmine-red (0.025 M PoBr4) and in more dilute solution (10 3 M), orange red. The tetrabromide is soluble in ethanol, acetone and some other ketones, and is sparingly soluble in liquid bromine. It is hygroscopic and is easily hydrolyzed to a white, basic bromide of variable composition. It forms a yellow ammine in ammonia gas and this yields polonium dibromide and polonium metal on standing, presumably because of radiation decomposition of the ammonia and subsequent hydrogen reduction of the tetrabromide (7). 

Thus hydrobromic acid is more strongly stabilized in monoglyme + water mixtures than in water. Moreover, the negative values of AG for the experimental mixed solvent compositions support the view that water is less basic than the mixed solvents, if it is assumed that the hydration of a larger bromide ion in aqueous solution is negligible, although our data indicates that the hydration number of chloride in aqueous solution might not be zero (22). 

When the reduction is completed, the flask is connected with a condenser and the mixture subjected to distillation. The boiling point of constant boiling hydrobromic acid is 125-126° at 760 mm., but it must be remembered that in distilling the product from the sulfuric acid mixture, the thermometer reading should not be relied upon as an index to the composition of the distillate. Towards the end of the distillation the thermometer may rise to 130° and above, when water with only traces of acid distils from the sulfuric acid residue. Upon redistillation of the product the thermometer reading may be relied upon. For many uses a product free from traces of... 

Hypovanadic Bromide, vanadium tetrabromide, VBr4, has not hitherto been isolated, but it is of interest to note that a double salt of composition VBr4.SbBr3.7HaO has been obtained by dissolving antimony tribromide and vanadium pentoxide in hydrobromic acid and adding bromine. ... 

Potassium Aquobromruthenate, KaRu(OH2)Br5, may be prepared 3 by boiling potassium bromruthenite with alcohol and hydrobromic acid. On standing, minute brown crystals, having the above composition, separate out. 

Preliminary emf measurements were made on Cell I, and the standard potential of the Ag-AgBr electrode was determined as 0.07106 V from data taken in 0.01000 mol kg"1 hydrobromic acid. This value of Em° was identical with that given in the literature (20). The emf values were reproducible up to m = 1.0 mol kg"1. There was some evidence of irreversible behavior for m = 1.5 mol kg"1. In order to avoid this kind of drift in the emf values at the highest constant total molality tested, the cell with the hydrogen electrode was allowed to equilibrate for 45 min before the Ag-AgBr electrode (which was kept in a separate standard-joint test tube containing a solution of the same composition) was transferred to the electrode compartment. The equilibrium emf value was recorded every 5 min until no deviation was noticed. 

The values of E, log y , Mxy> A, and B from Equations 5-10 substituted into Equation 4, make it possible to calculate Em0 at known molalities of hydrobromic acid, solvent compositions, and temperatures. By plotting values of Em° at a given solvent composition and temperature vs. molality, one can find the standard electrode potential E° of the Ag-AgBr electrode at that solvent composition and temperature from the value of Em° extrapolated to infinite dilution. This method has been used successfully in water and in organic solvent-water mixtures of higher dielectric constants, but if the mixed solvents have low dielectric constants, ca. 50 or below, the curvatures of the Em0f vs. m plots are sufficient to prevent accurate determinations of Em0 and hence of E°. 

Addition.—When ethylene, C2H4, is treated with hydrobromic acid, or with bromine, it does not act slowly as does methane or ethane, but most readily, and the resulting compounds are found to have the composition represented by the formulas C2H5Br, and C2H4Br2. That is, one hydrogen atom and one bromine atom or two bromine atoms are added directly to the hydrocarbon molecule. 

The fact that methyl alcohol is much more readily converted into methyl iodide by hydriodic acid than into methyl chloride by hydrochloric acid, is evidence that the reactions involved are probably not of the same nature as those of neutralization in inorganic chemistry. It is probable that the reaction between the alcohol and the halogen acid involves the formation of an intermediate addition-product, which subsequently decomposes into water and the alkyl halide. That such addition-products can exist is shown by the fact that when methyl alcohol is treated with liquid hydrobromic acid, a compound having the composition CHaOH.HBr is formed. 

Composition. A botde of concentrated hydrobromic acid has the following information on the label Assay 48% HBr. Sp. gr. 1.5. The assay is the percentage by mass the specific gravity is numerically equal to the density in grams per milliliter. Calculate (a) the mole fraction and (b) the molarity of HBr in this solution. 

Tellurium-containing products were not obtained when tellurium tetrachloride reacted with ethylene. The instability of this addition product makes it a desirable intermediate in the catalytic oxidation of ethylene. Patents for such a process using a solution of tellurium dioxide in hydrobromic/glacial acetic acid were issued - Diisobutylene, 1,4-diphenylbuta-diene, 2,3-diphenylbutadiene, 2,4-hexadiene , allyl bromide, allyl chloride, allyl acetate, and styrene either reduced tellurium tetrachloride to tellurium, produced compounds of indefinite composition, or did not react at all. 

---