A nearly chemically pure amorphous carbon made by carbonizing and treating dense material such as coconut shells, peach pits, or hardwood. When made from coal, or in the chemical industry, it is more usually called activated carbon, or filter carbon. It may be made by dry distillation, or by leaching the charcoal with steam or by treatment with zinc chloride or potassium thiocyanate. It is used as an adsor bent material for gas masks, for cigarette filters, and for purifying acids,recovering solvents, and decolorizing liquids. Coconut charcoal, valued for gas masks, is an activated charcoal usually made by heating coconut shells in a closed retort, crushing, and steam treating. An activated charcoal made from coconut shell will adsorb 68% of its weight of carbon tetrachloride
A requirement of activated charcoals, besides high adsorbing power, is that they possess strength to retain a porous structure to pass the air or liquid. Activated carbon CXC4-6, of Union Carbide Corp., produced from petroleum and used as a catalyst support, is in 3/16-in (0.48-cm) pellets of high hardness and strength. Powdered activated charcoal is usually ground to 300 mesh. For water purification it should be {ine enough to wet easily, but not so light that it will float on the top. For decolorizing or deodorizing oils and chemicals it is mixed in the liquid and settles out in a few hours. A single drop of water will hold 10,000 particles of powdered charcoal. In sugar and oil refining it removes color but does not bleach like chemicals. Color removal is measured by the molasses number which is the index of color removed per gram of carbon when tested on a standard molasses solution. Hydrodarco, of the Atlas Chemical Industries, is a powdered activated carbon. Norit, of the American Norit Co., Inc., is a group of highly adsorptive activated carbons. Kelpchar is activated carbon made from seaweed. Tec-Char, of the Tennessee Eastman Co., is a by-product charcoal obtained in wood distillation, and in graded grains for various uses.
Nuchar is an activated carbon of the West Virginia Pulp 8e Paper Co. The activated carbon of the Masonite Corp. is made by subjecting wood chips to high steam pressure and disintegrating by sudden release of the pressure. The doughy mass is briquetted and carbonized. Activated carbon derived from coal is harder than organic carbons and
does not crumble easily, permitting a higher flow of liquid to be filtered. It has a high density and high activity. SGL carbon, of the Pittsburgh Coke Chemical Co., has a density of 0.46, and an iodine number of 1,000 compared with 650 for ordinary carbons. Its color-removal index is about 40% higher than that of organic carbons. Filt-o-cite, of the Shamokin Filter Co., is finely ground anthracite used to replace sand as a filtering agent for industrial wastes.
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