Page:The American Cyclopædia (1879) Volume III.djvu/780

770 CARBON ing considered accidental ; also gas carbon, the extremely hard substance which is deposited upon the inner surface of gas retorts; and lampblack, the soot deposited by highly com- bustible bodies, as they are imperfectly con- sumed. When one atom of carbon is com- bined with two atoms of oxygen, it forms the compound carbonic anhydride, commonly call- ed carbonic acid gas, an essential constituent of solid limestones and other carbonates, and, in a gaseous form, of the atmospheric air. Its compounds with hydrogen are called hydro- carbons; they occur in gaseous, solid, and | liquid forms. The chemical equivalent of car- bon is 12, established by Dumas by the dia- mond, when consumed in a stream of oxygen gas, combining with this in the proportion of 12 parts to 32. Carbon resists the influence of many reagents which powerfully affect other bodies; acids and alkalies at ordinary tem- peratures have no effect upon it in its denser forms ; but charcoal is oxidized in boiling nitric acid. Neither is it affected by the strongest heat attainable in furnaces, provided it be pro- tected from the action of air or oxygen. Pieces of charcoal are found enclosed in the cinders of the blast furnace, which have been for 24 hours or more in the intense heat of its in- terior, among melting ores and limestones, but protected in some way from exposure to the oxygen of the blast. The only indications of volatilization or fusion which it can be made to exhibit, are seen by exposing it in a vacuum to the heat from a Bunsen's battery of several hundred pairs, so arranged in five or six series as to form 100 pairs of five or six times the or- dinary size. It is then volatilized, and collects on the sides of the vessel in the form of a black crystalline powder. It is ultimately converted into graphite. Diamond is similarly affected. No substance, unless it be crystallized boron, is more unalterable in most conditions in which other bodies undergo a chemical change. It is taken up by some metals when these are fused in contact with it, and its presence in cast iron and steel imparts to them the qualities that distinguish them from malleable iron. In connection with the question of the volatility of carbon at high temperatures, Eis- ner has observed that when porcelain vessels are heated in the pottery furnace on trays made of a mixture of clay and graphite, they become brown-black throughout their mass, and covered with a light gray specular glaze. This result is attributed by him to volatiliza- tion of the carbon. Regnault, on the contrary, ascribes it to the formation of a hydro-car- bon. The most valuable qualities of carbon in practical uses are its strong affinity for oxy- gen at high temperatures, and its power of re- sisting in some of its forms the high heat of furnaces. The former quality gives to many of its varieties their value as combustibles (see FUEL), and it also renders carbon a most pow- erful reducing agent of the oxides of the met- als; for which purpose, as well as for gene- rating heat by its combustion, it is employed in smelting furnaces, bloomaries, &c. Its dis- appearance as carbonic acid gas adds greatly to the convenience of its use for this purpose. Its refractory character admirably adapts it as a material for crucibles; and when used in the form of paste of pure charcoal powder ground very finely, and applied as a lining to earthen crucibles, it serves not merely to protect the contents from injurious contact with the outer vessel, but also furnishes to these the best re- ducing agent or flux. The black lead crucibles or blue pots are in part composed of graphite, which, when prepared by grinding and mixing with refractory earths, powerfully resists even the action of the blast in highly heated fur- naces. Other useful purposes served by car- bon are considered in treating of the subjects in which this is the principal element, as BONE BLACK, CHARCOAL, COAL, COKE, DIAMOND, FUEL, GRAPHITE, &c. The peculiar form of carbon already referred to as being found lining gas retorts, and collected in crevices in their interior, possesses a metallic lustre, and is of mammillary structure, resulting from the aggregation of the vesicles of which it is com- posed. It is sometimes fibrous, resembling graphite ; its specific gravity is 1 -I 76. Its hard- ness exceeds that of any other form of carbon, except the diamond. It is burned with diffi- culty in high heat when exposed to currents of air a property which renders it useful for the illuminating points of the voltaic light. Its origin is commonly attributed to a deposition of carbon from olefiant gas, CiHt, which is generated in the distillation of bituminous coal, and is converted by parting with one atom of carbon into marsh gas or the light carburetted hydrogen, CH 4 , used for illumination. Carbon is, under certain circumstances, separated from cyanides in the form of graphite. This occurs at one stage of the soda ash manufactory ac- cording to the method of Le Blanc, and it is proposed to recover the shiny material sepa- rated in this way and apply it for the same pur- pose for which the natural graphite is used. CARBON. I. An E. county of Pennsylvania ; area, about 400 sq. m. ; pop. in 1870, 28,144. It is a mountainous district, made up of paral- lel ridges running in a N. E. and S. W. direc- tion. The largest of these is the Blue or Kit- tatinny mountain, which bounds the county on the S. E. Anthracite is the principal pro- duction of the county. The coal mines are in the smaller ridges N. W. of this. Of these, Manch Chunk, at the eastern termination of the southern anthracite coal field, is the most important. At the top of Summit mountain the beds have been opened and worked like a quarry, the coal lying in a mass not less than 50 ft. thick. The Hazleton and Beaver Meadow mines are in the N. W. corner of the county. The coal is transported by railroads from the mines to the Lehigh river, and thence by slackwater navigation and canal, and also by the Lehigh Valley railroad, down the Le-