PREPARATIONS 203 elimination of the amino group, because the tribromobenzene so formed is solid, and small quantities can easily be purified by recrystallisation. Required: 2,4,6-Tribromoaniline, 5 g.; absolute ethanol, 40 ml.; dry benzene, 10 ml.; sodium nitrite, 3 g. Dissolve 5 g. of 2,4,6-tribromoanilinc in a hot mixture of 40 ml. of absolute ethanol and 10 ml. of dry benzene con-tained in a 150 ml. wide-necked bolt-head flask. (The benzene is added to increase the solubility of the tribromoaniline.) Now add 2 ml. (3-9 g.) of concentrated sulphuric acid (pre-ferably from a burette or a small pipette) to the hot solution, shaking the latter gently round. Attach the flask to a reflux water-condenser and heat on a water-bath until the clear solution boils. Now detach the flask, add 3 g. of dry powdered sodium nitrite, and return the flask to the condenser but not to the water-bath. Shake the flask vigorously: the heat of the reaction causes the solution to continue boiling for several minutes. When the
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