Charcoal purification

The preparation protocol for individual samples is important because of different preservation stage, sample size and possible samples loss during treatment (Nawrocka et al., 2007, 2009 Rebollo et al., 2008 Szczepaniak et al, 2008). The first stage of wood and charcoal purification was removal of macroscopically visible plant roots. Then the samples have been subjected to the "acid-base-acid" (ABA) preparation step by treatment with IM HCl solution. The aim of this step was to dissolve carbonates and other soluble minerals. The second stage was submerging the samples in the base solution (0,025 M NaOH and 0,5 M NaOH) to remove humic compounds. The last ABA step was the repeated acid treatment (0,25 M HCl). Each time, the samples were bathed in deionised water to restore the neutral pH. 

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°. 

Purification of charcoal. Heat Norit charcoal on a water bath for 6 hours with 10 per cent, nitric acid, filter, wash free from acid, and dry at 100°. If the acid-washed form of Norit charcoal is available, it may be used directly without further purification. 

Castor oil may be obtained by cold expression of the decorticated seed. The oil is steamed under vacuum to eliminate odors and coagulate the toxic albumin. Fuller s earth or activated charcoal may be used for further purification. 

Because of their zwitterionic nature, amino acids are generally soluble in water. Their solubility in organic solvents rises as the fat-soluble portion of the molecule increases. The likeliest impurities are traces of salts, heavy metal ions, proteins and other amino acids. Purification of these is usually easy, by recrystallisation from water or ethanol/water mixtures. The amino acid is dissolved in the boiling solvent, decolorised if necessary by boiling with Ig of acid-washed charcoal/lOOg amino acid, then filtered hot, chilled, and set aside for several hours to crystallise. The crystals are filtered off, washed with ethanol, then ether, and dried. 

Adipic acid [124-04-9] M 146.1, m 154 , pK 4.44, pK 5.45. For use as a volumetric standard, adipic acid was crystd once from hot water with the addition of a little animal charcoal, dried at 120 for 2h, then recrystd from acetone and again dried at 120 for 2h. Other purification procedures include crystn from ethyl acetate and from acetone/petroleum ether, fusion followed by filtration and crystn from the melt, and preliminary distn under vac. 

Benz[a]anthracene [56-55-3] M 228.3, m 159-160". Crystd from MeOH, EtOH or benzene (charcoal), then chromatographed on alumina from sodium-dried benzene (twice), using vacuum distn to remove benzene. Final purification was by vacuum sublimation. 

Bipyridyl [366-18-7] M 156.2, m 70.5 , b 273 , pK -0.52, pK 4.44. Crystd from hexane, or EtOH, or (after charcoal treatment of a CHCI3 soln) from pet ether. Also ppted from a cone soln in EtOH by addition of H2O. Dried in a vacuum over P2O5. Further purification by chromatography on AI2O3 or by sublimation. [Airoldi et al. J Chem Soc, Dalton Trans 1913 1986.]... 

Naphthol [135-19-3] M 144.2, m 122.5-123.5°, pK 9.57. Crystd from aqueous 25% EtOH (charcoal), water, benzene, toluene or CCI4, e.g. by repeated extraction with small amounts of EtOH, followed by dissolution in a minimum amount of EtOH and pptn with distilled water, then drying over P2O5 under vacuum. Has also been dissolved in aqueous NaOH, and ppted by adding acid (repeated several times), then ppted from benzene by addition of heptane. Final purification can be by zone melting or sublimation in vacuo. [Bardez et al. J Phys Chem 89 5031 7955 Kikuchi et al. J Phys Chem 91 574 1987.]... 

Phenylenediamine [95-54-5] M 108.1, m 100-101 , pK O.67 (aq H2SO4), pKj 4.47 (4.85). Crystd from aqueous 1% sodium hydrosulfite (charcoal), washed with ice-water and dried in a vacuum desiccator, or sublimed in vacuo. It has been purified by recrystn from toluene and zone refined [Anson et al. J Am Chem Soc 108 6593 1986]. Purification by refluxing a CH2CI2 solution containing charcoal was also carried out followed by evaporation and recrystn [Koola and Kochi J Org Chem 52 4545 1987], protect from light. 

The crude product separates as a solid from the reaction medium and is recovered by filtration, and it is then washed thoroughly with ether and dissolved in 350 ml 1 N HCI. Then, approximately 250 ml of the aqueous solvent is removed with a rotary evaporator and the evaporation residue combined with 125 ml methanol and filtered through decolorizing charcoal. The product is precipitated as the HCI salt by the addition of 7 parts of acetone. The resulting crystalline material is removed by filtration dried at 40°C with vacuum, and has a melting point of about 242°C and Is used without further purification. 

B) t-Butyl 2-Methyl-5-Methoxy-3-lndolylacetate t-Butyl alcohol (25 ml) and fused zinc chloride (0.3 g) are added to the anhydride from Part A. The solution is refluxed for 16 hours and excess alcohol is removed in vacuo. The residue is dissolved in ether, washed several times with saturated bicarbonate, water, and saturated salt solution. After drying over magnesium sulfate, the solution is treated with charcoal, evaporated, and flushed several times with Skellysolve B for complete removal of alcohol. The residual oily ester (18 g, 93%) is used without purification. 

For purification, the product was dissolved in water and the solution was filtered through iron-free charcoal. 

Adsorption beds of activated carbon for the purification of citric acid, and adsorption of organic chemicals by charcoal or porous polymers, are good examples of ion-exchange adsorption systems. Synthetic resins such as styrene, divinylbenzene, acrylamide polymers activated carbon are porous media with total surface area of 450-1800 m2-g h There are a few well-known adsorption systems such as isothermal adsorption systems. The best known adsorption model is Langmuir isotherm adsorption. 

A cleanup procedure is usually carried out to remove co-extracted matrix components that may interfere in the chromatographic analysis or be detrimental to the analytical instrument. The cleanup procedure is dependent on the nature of the analyte, the type of sample to be analyzed, and the selectivity and sensitivity of the analytical instrument used in the analysis. Preliminary purification of the sample extracts prior to chromatographic separation involves liquid-liquid partitioning and/or solid-phase extraction (SPE) using charcoal/Celite, Elorisil, carbon black, silica, or aminopropyl-silica based adsorbents or gel permeation chromatography (GPC). 

The details of the pretreatment of the electrodes and purification of the charcoal and the solution have already been described in an earlier publication43 and review.40... 

All the filtrations in the purification of tyrosine, except possibly the last, are best done on a 20-cm. Buchner funnel. Whenever charcoal is used, kieselguhr may be employed to obtain a clear filtrate. 

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