Filtration through animal charcoal

Derivation Purification of ozocerite by treatment with concentrated sulfuric acid and filtration through animal charcoal. 

The resulting solution was filtered through animal charcoal and, after addition of 2 liters of methanol, it was debenzylated by hydrogenation at 60°C over palladinized charcoal as a catalyst. After removal of the catalyst by filtration, the filtrate was concentrated by evaporation, whereupon the hydrochloride of 1-p-methoxyphenyl-2-((3-3, 5 -dihydroxyphenyl-(3-oxo)-ethylamino-propane (MP 244°C) crystaiiized out. For the purpose of demethyiation. 

G. G. Nasmith and G. P. McKay, P. Rudnik, etc. According to A. Muntz and E. Laine, the filtration of dil. ammoniacal soln. through animal charcoal or peat is accompanied by some nitrification. F. Hiippe, W. Heraeus, R. Warington, A. Muntz, T. Leone and 0. Magnanini, T. Schlosing, M. Berthelot, P. F. and... 

For purification, transfer the acid to a 150 ml. flask containing 60 ml. of water, boil the mixture under reflux, and then add acetic acid in 5 ml. portions down the condenser until almost all the solid has dissolved avoid an excess of acetic acid by ensuring that the solvent action of each addition is complete before the next portion is added. A small suspension of insoluble impurity may remain. Add 2 g. of animal charcoal, boil the solution again for 10-15 minutes, and then filter it through a preheated Buchner funnel. Cool and stir the filtrate, which will deposit pale cream-coloured crystals of the acid. Collect as before and if necessary repeat the recrystallisation. Yield of pure acid, 9 g. m.p. 227-229°. 

Recrystallise from methylated spirit, using animal charcoal for this purpose, use about twice the minimum quantity of methylated spirit required to obtain a clear solution, and filter through a funnel preheated by the filtration of some boiling solvent, as the tribromobenzene separates very rapidly as the solution cools. The 1,3,5-tribromobenzene is thus obtained as colourless crystals, m.p. 122° yield, 3 g. 

Recrystallise the remaining half of the crude anthraquinone from boiling acetic acid, using animal charcoal filter the hot solution through a Buchner funnel which has been preheated by the filtration of some of the boiling solvent, as the anthraquinone crystallises rapidly as the solution cools. Cool the filtrate in cold water and then filter at the pump, drain, wash with methylated spirit and dry. Yield, 4-5 g. 

Charcoal is generally satisfactorily activated by heating gently to red heat in a crucible or quartz beaker in a muffle furnace, finally allowing to cool under an inert atmosphere in a desiccator. Good commercial activated charcoal is made from wood, e.g. Norit (from Birch wood), Darco and Nuchar. If the cost is important then the cheaper animal charcoal (bone charcoal) can be used. However, this charcoal contains calcium phosphate and other calcium salts and cannot be used with acidic materials. In this case the charcoal is boiled with dilute hydrochloric acid (1 1 by volume) for 2-3h, diluted with distilled water and filtered through a fine grade paper on a Buchner flask, washed with distilled water until the filtrate is almost neutral, and dried first in air then in a vacuum, and activated as above. To improve the porosity, charcoal columns are usually prepared in admixture with diatomaceous earth. 

From the residue after the steam distillation the non-volatile p-compound is isolated at the same time, at first in the form of its sodium salt. Sodium hydroxide solution (2 N) is added until the reaction to Congo paper has just disappeared, 100 c.c. more of the hydroxide solution are then poured in, and the mixture is boiled with a little animal charcoal while steam is again passed through. The solution is now filtered through a folded paper and the filtrate is... 

Dumont s filter consists of a wooden box of j he form of a four-aided truncated pyramid with a double bottom. The inner bottom is a metallic plate pierced with numerous holes upon it a cotton cloth is kid, and coarse-grained animal charcoal moistened with water is then Bpread layer by layer each layer being rendered of uniform thickness, and packed or pressed closely together by means of a sort of trowel. When the bone-black has been thus formed into a compact bed or stratum of about fifteen or eighteen inches in thickness, and Within five to ten inches fi om the top of the box, it is covered with another cotton cloth, and with another metallic plate pierced with holes, The object of the second cloth and metallic cover Is to collect any substances which would otherwise obstruct the interstices of tho superior stratnm. of the bone-black—an inconvenient accident which is easily prevented by the use of such a cover, and this cover is readily exchanged for another, should it be no mo itself obstructed. The superior covir is only of use when the previously described filtration through the cotton bag or leaf filter is omitted. 

Experiment 83. — Fill a test tube one-fourth full of animal charcoal (see App. A, 11), add 10 cc. of indigo solution, shake thoroughly for a minute, and then warm gently. Filter through a wet filter paper into a clean test tube. Compare the color of the filtrate with that of the indigo solution. Explain the change in color. 

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