Decolourising carbon

Carbon dioxide, 184, 358, 359 solid see Dry Ice Carbon disulphide, 767 purification of, 175 Carbon monoxide, 185, 1003, 1004 Carbon, decolourising, 127, 128 Carbon tetrachloride, 733, 815 drying of, 734 purification of, 176 Carbonyl chloride, 185 Carborundum chips, 4 Carboxylic acids, equivalent weights of, 1071 ... 

Alternative Names/Abbreviations Activated carbon, acetyiene carbon, decolourising carbon, actibon, ultra carbon, channel black, furnace black, thermal black, gas black, lamp black... 

REMOVAL OF TRACES OF COLOURING MATTER AND RESINOUS PRODUCTS USE OF DECOLOURISING CARBON... 

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. ... 

A solution prepared by dissolving 2 g. of biomine in 100 g. of carbon tetra. chloride is satisfactory. Carbon tetrachloride is employed because it is an excellent solvent for bromine as well as for hydrocarbons it possesses the additional advan. tage of low solubility for hydrogen bromide, the evolution of which renders possible the distinction between decolourisation of bromine due to substitution or due to addition. 

Trimethylene Di-iodide. Use 76 g. of trimethylene glycol, 27 - 52 g. of pmified red phosphorus and 254 g. of iodine. Lag the arm C (Fig. Ill, 40, ) with asbestos cloth. Stop the heating immediately all the iodine has been transferred to the fiask. Add water to the reaction mixture, decolourise with a httle sodium bisulphite, filter, separate the crude iodide, wash it twice with water, dry with anhydrous potassium carbonate and distU under reduced pressure. B.p. 88-89°/6 mm. Yield 218 g. (a colourless liquid). 

Unsaturated esters decolourise a solution of bromine in carbon tetrachloride and also neutral potassium permanganate solution. 

A further 25 g. of cyanoacetamide may be obtained by evaporating the original mother liquor to dryness under reduced pressure (water pump) whilst heating the flask on a steam bath. The residue is dissolved in 50 ml. of hot ethanol, the solution shaken for a few minutes with decolourising carbon, Altered with suction whilst hot, and then cooled in ice. The resulting yellowish amide is recrystallised with the addition of decolourising carbon, if necessary. 

Oxidation of 10-undecynoic acid to sebacic acid. Dissolve 2 00 g. of the acid, m.p. 41-42°, in 50 ml. of water containing 0 -585 g. of pure anhydrous sodium carbonate. Saturate the solution with carbon dioxide and add O IN potassium permanganate solution (about 1500 ml.) slowly and with constant stirring until the pink colour remains for half an hour the addition occupies about 3 hours. Decolourise the solution with a httle sulphur dioxide and filter off the precipitated acid through a... 

Place a mixture of 1 0 g. of the hydrocarbon, 10 ml. of dry methylene chloride or ethylene dichloride or syw.-tetrachloroethane, 2 5 g. of powdered anhydrous aluminium chloride and 1-2 g. of pure phthalic anhydride in a 50 ml. round-bottomed flask fitted with a short reflux condenser. Heat on a water bath for 30 minutes (or until no more hydrogen chloride fumes are evolved), and then cool in ice. Add 10 ml. of concentrated hydrochloric acid cautiously and shake the flask gently for 5 min utes. Filter oflf the solid at the pump and wash it with 10-15 ml. of cold water. Boil the resulting crude aroylbenzoic acid with 10 ml. of 2 -5N sodium carbonate solution and 0 2 g. of decolourising carbon for 5 minutes, and filter the hot solution. Cool, add about 10 g. of crushed ice and acidify... 

The p-bromoaniline separates as an oil, which soon sohdifies. Filter at the pump and wash with cold water. Purify the crude p-bromoanihne aa follows. Dissolve it in a mixture of 120 ml. of water and 75 ml. of concentrated hydrochloric acid, add 1-2 g. of decolourising carbon, and warm on a water bath for 10 minutes. Filter through a fluted paper or through two thicknesses of filter paper on a Buchner funnel. Pour the filtrate slowly and with vigorous stirring into a mixture of 60 ml. of 10 per cent, sodium hydroxide solution and 100 g. of crushed ice. Thep-bromo-aniline crystallises out. Filter, etc. as in Method 1. The yield is 11 5 g. 

Unless the material is at least partly dried before hydrolysis, the yield of hydrochloride is reduced because of its solubility. If pure 3-broino-4-acetamino-toluene is required, the crude material may be recrystallised from 50 per cent, alcohol with the addition of a little decolourising carbon it separates as colourless needles, m.p. 116-117 (180 g.). 

If desired, the phenylhydrazine hydrochloride may be purified by recrystai-lisation. The crude hydrochloride is boiled with 6 times its weight of water and a few grams of decolourising carbon. After filtering, a volume of concentrated hydrochloric acid equal in volume to one-third of the solution is added, and the mixture cooled to 0°. Pure white crystals are obtained in 85-90 per cent, yield. 

The crude o-phenylenediamine may be converted into the dihydrocliloride and the salt purified in the following manner. Dissolve it in 60 ml. of concentrated hydrochloric acid and 40 ml. of water containing 2 g. of stannous chloride, and treat the hot solution with 2-3 g. of decolourising carbon. Filter, add 100 ml. of concentrated hydrochloric acid to the hot colourless filtrate, and cool in a freezing mixture of ice and salt. Collect the colourless crystals of the dihydrochloride on a Buchner or sintered glass funnel, wash with a small volume of concentrated hydrochloric acid, and dry in a vacuum desiccator over sodium hydroxide. The yield is 61 g. 

To isolate the triphenylguanidine, dilute the residue in the flask with 50 ml. of water, add 2-3 g. of decolourising carbon, warm, and filter. Cool the solution in ice, and filter oflF the hydrochloride at the pump. Dissolve it in the minimum volume of hot water, render the solution alkaline with sodium hydroxide, and allow to cool. Filter off the free base (triphenylguanidine), and recrystallise it from alcohol it separates in colourless crystals, m.p. 144°, The yield is 3 g. 

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