Hydration, water Hydrobromic acid

Chemical/Physical. Hydrolyzes in water forming methanol and hydrobromic acid. The estimated hydrolysis half-life in water at 25 °C and pH 7 is 20 d (Mabey and Mill, 1978). Castro and Belser (1981) reported a hydrolysis rate constant of 3 x 10 Vsec or a half-life of 26.7 d. Forms a voluminous crystalline hydrate at 0-5 °C (quoted, Keith and Walters, 1992). 

Dinitrito - tetrammino - iridium Bromide, [Ir(NH3)4(N02)2] Br.H20, separates in long, colourless, flat prisms, and may be obtained anhydrous by reerystallisation from hydrobromic-acid solution. The hydrated salts lose water on heating but not over phosphorus pentoxide. 

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). 

Tellurium tetrabromide is slightly hygroscopic and can be dissolved in a little water without decomposition. The aqueous solution, on evaporation over sulphuric acid, yields a deep red hydrated product. More water causes hydrolysis to tellurous and hydrobromic acids ... 

The filtrate is run into an equal volume of 48% hydrobromic acid. The chocolate-brown monohydrate of the desired product is precipitated this is filtered off, pressed well, and dried for one hour at 110°C to remove the water of hydration. Olive powder. 

Iridium Tribromide, IrBr3.4H20, may be obtained by dissolving the hydrated dioxide, Ir02.2H20, in hydrobromic acid, and evaporating to dryness to decompose the tetrabromide thus formed. Extraction with water and subsequent crystallisation yields olive-green prisms, very soluble in water, but insoluble in alcohol. 

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