Bromopentamminechromium III Bromide

Four and two-tenths grams of aquopentamminechro-mium(III) ammonium nitrate (0.01 mol) is dissolved in 8 ml. of water containing 2 ml. of 15 M aqueous ammonia. Ten milliliters of 48% hydrobromic acid and 10 ml. of 95% ethanol are added, and the mixture is cooled to 0°. The precipitate is collected on a filter, washed with 95% ethanol, and dissolved in 20 ml. of water. The resulting solution is filtered, treated with 20 ml. of 48% hydrobromic acid, and cooled to 0°. The crystallized aquo-pentamminechromium(III) bromide is removed by filtration and washed with 95% ethanol. The yield is 3.3 g. (83%). Anal Calcd. for [Cr(NH3)5(H20)]Br3 Cr, 13.2 NH3, 21.6 Br, 60.7. Found Cr, 13.5 NHS, 21.8 Br, 60.6. 

These crystals are dissolved in 20 ml. of water, and 5 ml. of 48% hydrobromic acid is added. The mixture is digested on a steam bath for 30 minutes, while three 5-ml. portions of 48% hydrobromic acid are added at intervals of several minutes. The mixture is cooled to room temperature and filtered. The precipitate of bromopentam- 

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