Charcoal, Wood

Syn. Veg′etable charcoal ; Car′bo lig′ni , L. The residue obtained after heating wood without acce of air to about 572° Fahr. It is extremely porous, and retains the structure of the wood from which it is derived. It consists e entially of carbon and of the fixed or inorganic matter which exists in wood; but if carbonisation be imperfectly effected, it may contain a sensible amount of hydrogen. Charcoal burning is effected in the open air in piles or stacks provided with a yielding cover, in pits, in closed chambers of brick or stone, and in iron retorts heated externally like common gas retorts. The latter method is only practised by the manufacturers of pyroligneous acid and gunpowder. Charcoal for Fuel , . The method of pile burning is that which is most extensively practised. Pieces of wood of equal length are piled concentrically round a sort of chimney formed by driving 3 stakes in the ground; those nearest the centre are almost vertical, and the surrounding pieces have a slight but gradually increasing inclination; a second row, and in the case of very large piles even a third, may be stacked in a similar manner one above the other. The pile is covered with turf and soil, and kindled by filling the space within the 3 central stakes with easily inflammable wood, which is ignited. The character of the smoke which i ues from vents made in the piles indicates exactly the degrees of carbonisation in different parts. When the charcoal is drawn from the pile it is extinguished by cold water, or if that is not at hand, by charcoal dust or dry soil. In some parts of Sweden the wood is charred in large rectangular stacks, and in China the method of charring in pits is practised. Charcoal for Gun′powder; Cyl′inder Charcoal. The charcoal employed in the manufacture of gunpowder is burnt in close iron cylinders, and has hence received the name of cylinder charcoal. For this and other nice purposes it is e ential that the last portion of the tar and vinegar should be suffered to escape, and the reabsorption of the crude vapours prevented by cutting off the communication between the cylinders and the condensing apparatus; as without this precaution, on the fire being withdrawn, a retrograde movement of the product takes place, and the charcoal is much reduced in quality. Alder and willow are the woods chiefly used for making charcoal at Waltham Abbey. The Dutch white willow, and after that the Hunting don willow, are said to yield the best charcoal for gunpowder. The charcoal from the cylinders of the pyroligneous acid (wood vinegar) works is also called cylinder charcoal, and is that chiefly used for chemical purposes; but it is inferior to that prepared for gunpowder. Charcoal for Scientific Purposes. The box-wood charcoal, employed in voltaic electricity, is prepared by putting prismatic pieces of box-wood, about 1 inch long by 1 ⁄ 2 inch thick, into a crucible, which is then filled with clean, dry sand, covered up, and exposed to a red heat for about an hour. Uses, . These are numerous and varied. Charcoal is extensively employed as a fuel; and in metallurgy for tempering metals, making steel, .; reduced to powder, it is used to surround ve els and bodies required to retain their heat for some time; a coating of charcoal, formed on piles and stakes of wood by charring them, promotes their preservation. Fresh burnt charcoal, in coarse powder, restores tainted meat and putrid water, discolours vegetable solutions, deodorises fetid substances, and withdraws lime from syrups filtered through it. Exposed on trays it is used as a disinfectant and deodoriser in the wards of hospitals and in di ecting rooms, also as a material for water filters. In medicine , charcoal is principally used as a deodoriser and disinfectant, either in the form of powder or made into a poultice. It has been given internally in dyspepsia, diarrhœa, dysentery, heartburn, agues, constipation, sickne of pregnancy, and various other diseases, with advantage. As a prophylactic of cholera and fevers it is invaluable and superior to all other substances. It forms the best tooth powder known, as it both whitens the teeth and deodorises the breath.— Dose , 10 gr. to a teaspoonful, or more ad libitum . An ointment made with lard and charcoal has been succe fully employed in some skin diseases. In all cases, to be useful, the charcoal must be both fresh-burnt and fresh-powdered, and carefully preserved, out of contact with the air, until about to be administered. Fresh carbonised bread forms an excellent charcoal, both for a prophylactic and a tooth powder. Charcoal varies in its qualities according to the substance from which it is prepared: that of the soft woods (willow or alder) is best for crayons and gunpowder; that of the hard woods for fuel, and for blowpipe supports. That made by a low red heat, not exceeding cherry red, and which has a dull surface, is the most valuable. If the heat be carried much beyond this point, the charcoal acquires a brilliant surface, and deteriorates in quality. Chestnut charcoal is preferred by smiths for forging, as it not only burns slowly, but deadens as soon as the blast ceases. Areca-nut charcoal is preferred as a dentifrice; but the willow charcoal or box-wood charcoal is usually substituted for it by shopkeepers. Ant., . Poisoning or suffocation, resulting from respiring the fumes of burning charcoal, has been already alluded to, and the treatment briefly pointed out. See Carbonic anhydride .