Page:The American Cyclopædia (1879) Volume IV.djvu/282

 274 CIIAKOOAL CHARDIN tillation is kept below that of a red heat. If that temperature be exceeded, however, the aqueous vapor, in passing over the red-hot charcoal, reacts upon its carbon constituent and converts a portion of it into carbonic acid, carbonic oxide, and carburetted hydrogen ; all of which pass off in the gaseous form, diminish- ing the charcoal products by the amount of carbon they contain. If, of two equal weights of the same wood containing equal weights of uncombined water, one weight be dried while the water is allowed to remain in the other, the two masses will contain equal weights of lig- neous matter; and if they be charred or distilled at less than a red-heat temperature, under the same conditions, the same weight of charcoal will be obtained from the charred or distilled part of each. One pound of charcoal, having the chemical constitution given for it in the early part of this article, develops sufficient heat by combustion in oxygen to raise the tem- perature of 12, 306 '41 4 Ibs. of water, at the temperature of 32 F., one degree, or to evapo- rate under the atmospheric pressure 12 '743 Ibs. of water from the temperature of 212 F. One pound of what remains of this charcoal, after deducting its ash and hygroscopia water, will develop sufficient heat by combustion in oxygen to raise the temperature of 14,288 - 837 Ibs. of water, at the temperature of 32 F., one degree, or to evaporate under the atmospheric pressure 14'796 Ibs. of water from the tem- perature of 212 F. Equal weights of charcoal from all varieties of wood, prepared under equal conditions, haye the same heating power. In the ordinary mode of manufacturing char- coal in heaps, the sticks of wood are piled up, sometimes in horizontal and sometimes in ver- tical layers, around a central opening which extends from the bottom to the top of the heap. The heaps are conical or hemispherical, from 10 to 30 or 40 ft. in diameter, and of a height of about 12 ft. ; their outer surface, after being made even with chips and twigs, is covered with small branches, leaves, straw, or moss, upon which sods are laid together with the charcoal dust of previous burnings. This dust is mixed with sufficient earth to give it consistency, and when moistened the mixture makes the best of all coverings. The sticks of wood to be charred arc of any convenient size, and are closely packed, the interstices of the larger sticks being filled with smaller ones. The central vertical opening in the heap is left for a chimney, and for the introduction of the fire to ignite the heap ; to facilitate the latter, a horizontal opening is left in the bot- tom of the heap, extending from its periphery to the central opening. Around the bottom of the heap other smaller openings are made for the admission of air and the escape of the vola- tile products. As the charring process pro- ceeds, these small openings are closed, and new ones made nearer the top of the heap, and in other places, as it is found desirable to check the process in some parts and to hasten it in others. The heap is fired in the centre at the bottom, and the fire gradually spreads in all directions, but especially toward the open- ings by which the air is admitted. The first matter that escapes is aqueous vapor, which partly condenses in the cover of the heap, moistening it, and then passes off with a yel- lowish color. After the vapor disappears, it is followed by a lighter-colored smoke that be- comes black and dense, emitting the odor of pyroligneous acid, which grows stronger to the end of the process. The carbonization, first completed at the centre and top of the heap, gradually extends down its sides; and in a heap half charred, the finished portion has the form of an inverted cone, the apex of which is at the bottom of the vertical axis of the heap. As the line between the finished and unfinished portions moves downward, the open- ings for the admission of air are kept in ad- vance of it, and upper openings are closed as lower ones are made. The completion of the charring of each part of the heap is indicated by the smoke emerging from that part chang- ing from its black and dense appearance to a transparent light bluish color. The tarry mat- ters, which collect mostly toward the close of the operation, run out in channels made for that purpose beneath and around the heap. When the entire heap is completely charred, all its openings are closed, and it is then left for one or two days, after which it is partially un- covered and the charcoal drawn out and spread around in thin layers. This is best done at night, so that if any of the charcoal remains ignited, it can be quickly seen and quenched. The time required for the process varies with the size of the heap and the state of the weather. Small heaps may be charred in a week, and large ones may require three weeks. A common yield from one cord (128 cubic feet) of wood is about 30 bushels of charcoal. Animal charcoal has been described under BONE BLACK. CIIARDIN, Jean, a French merchant, born in Paris in November, 1643, died in London in January, 1713. He went to the East to trade in jewelry, became the favorite purveyor of the shah of Persia, and eventually produced a book of his travels and experiences in that country, which has been found true by subsequent trav- ellers, and translated into many foreign lan- guages. The London edition of 1686 contains only the description of his journey to Ispahan. Complete editions of the work, which is en- titled Journal du voyage du chevalier Chardin en Perse et aux Indes Orientals, par la Mer Noire et par la Colchide, appeared in 1711 and 1735. The most highly valued edition is that of Langles, the orientalist, who enriched it with a map, and with an abridged history of Persia (Paris, 1811). A Protestant by birth, Char- din was compelled on his return from the East in 1681 to seek refuge in England, where lie was knighted and appointed agent of the East India company in Holland.