Hydrobromic acid, composition solutions

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). 

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. 

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. 

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