Charcoal, decolourising

Chalkone, 709, 718 Charcoal, decolourising, 127, 128 Chloral hydrate, 1011 reactions of, 298 ... 

On the whole it is better to employ the activated decolourising charcoal prepared from wood. Excellent decolourising carbons are marketed under the trade names Norit (from birch wood), Darco and Nuchar. ... 

To isolate pure p-dibromobenzene, filter the second portion of the steam distillate through a small Buchner funnel with suction press the crystals as dry as possible. Combine these crystals with the residue (R) and recrystaliise from hot ethyl alcohol (for experimental details, see Section IV,12) with the addition of 1-2 g. of decolourising charcoal use about 4 ml. of alcohol (methylated spirit) for each gram of material. Filter the hot solution through a fluted filter paper, cool in ice, and filter the crystals at the pump. The yield of p-dibromobenzene, m.p. 89°, is about 12 g. 

Triiodobenzoyl chloride. Reflux 5 g. of 3 4 5-triiodo-benzoic acid, m.p. 289-290°, gently with 10 ml. of redistilled thionyl chloride for 2 hours. Distil off the excess of thionyl chloride on a water bath, and recrystallise the residue from carbon tetrachloride - light petroleum with the use of a little decolourising charcoal. The yield of the acid chloride (bright yellow needles, m.p. 138°) is 3-8 g. it keeps well in a stoppered bottle. 

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