Adsorbents charcoal

Decolorisation by Animal Charcoal. It sometimes hap pens (particularly with aromatic and heterocyclic compounds) that a crude product may contain a coloured impurity, which on recrystallisation dissolves in the boiling solvent, but is then partly occluded by crystals as they form and grow in the cooling solution. Sometimes a very tenacious occlusion may thus occur, and repeated and very wasteful recrystallisation may be necessary to eliminate the impurity. Moreover, the amount of the impurity present may be so small that the melting-point and analytical values of the compound are not sensibly affected, yet the appearance of the sample is ruined. Such impurities can usually be readily removed by boiling the substance in solution with a small quantity of finely powdered animal charcoal for a short time, and then filtering the solution while hot. The animal charcoal adsorbs the coloured impurity, and the filtrate is usually almost free from extraneous colour and deposits therefore pure crystals. This decolorisation by animal charcoal occurs most readily in aqueous solution, but can be performed in almost any organic solvent. Care should be taken not to use an excessive quantity... 

Charcoal adsorbent tubes with solvent desorption and gas chromatography... 

Glycol ether and glycol ether acetate vapours in air Lab method using charcoal adsorbent tubes, solvent desorption and gas chromatography 21... 

Acetylenes are most readily absorbed by CAA, and hence are generally removed in a prewash step. Strict control of the acetylene content of the recirculating solvent is necessary and a charcoal adsorbent bed is used to maintain the polymer content of the solution at low levels. 

MDHS 14 General method for the gravimetric determination of respirable and total dust MDHS 15 Carbon disulphide MDHS 16 Mercury vapour in air Laboratory method using hopcalite adsorbent tubes, and acid dissolution with cold vapour atomic absorption spectrometric analysis MDHS 17 Benzene in air Laboratory method using charcoal adsorbent tubes, solvent desorption and gas chromatography MDHS 18 Tetra alkyl lead compounds in air Continuous on-site monitoring method using PAC Check atomic absorption spirometry... 

Hexane may be determined in occupational air using collection on a charcoal adsorbent, followed by solvent desorption (Hakkola and Saarinen 1996 Rosenberg et al. 1992), or thermal desorption (Tang et al. 

Occupational air (breathing zone) Collection on charcoal adsorbent CS2 desorption GC/FID 0.006-1.1 ppb (50 L sample) Not reported Rosenberg et al. 1991... 

OSHA. 1979. Method No. 05. Collection on charcoal adsorbent, desorption with carbon disulfide, analysis by gas chromatography using a flame ionization detector. Organic Methods Evaluation Branch, Occupational Safety and Health Administration Analytical Lab, Salt Lake City, UT. May 1979. 

Adsorption. The adherence of atoms, ions, or molecules of a gas or liquid to a solid substance called an adsorbent. Activated charcoal adsorbs odors and other contaminants from a variety of gases. 

Charcoal adsorbent is used for collection of 1,4-dichlorobenzene in oeeupational air. The eompounds are desorbed with earbon disulfide and analyzed by GC/FID. The method is suffieiently sensitive and reliable for determining occupational exposure to 1,4-diehlorobenzene (NIOSH 1994). 

Pure charcoal adsorbs hydrogen and hydroxyl ions with equal facility and is itself inert in that it discharges no ions into the solution. Many adsorbiug agents, however, are either acid or basic in character in that they can discharge either hydrogen ions, e.g. 

Activated charcoal adsorbs salicylate effectively, and has been given in repeated oral doses (50 g 4 hourly) to enhance clearance, although its effect on outcome is unknown. Fluid and electrolyte replacement are important and special care should be taken to maintain normal potassium concentrations. Patients with signs of poisoning, especially when plasma salicylate concentration exceeds 500 mg/1, should receive specitic elimination therapy. 

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