CARBOHYDRATE 346 CARBONIC ACID CARBOHYDRATE, any one of a large group of compounds, containing six car- bon atoms or some multiple of six, and hydrogen and oxygen in the proportion in which they form water : 'that is, twice as many hydrogen as oxygen atoms. CARBOLIC ACID, CaHcOH, also called Phenol, Phenic acid. Coal-tar, Creosote. Phenol is a secondary mon- atomic aromatic alcohol, obtained by the dry distillation of salicylic acid. It is also formed by the dry distillation of coal, in the coal-tar oil. When pure it forms white deliquescent crystals melt- ing at 35° to an oily liquid, which boils at 184°. It has a penetrating odor and burning taste; it is neutral; it coagu- lates albumen and has powerful anti- septic properties. It is used as a disin- fectant, and to presei've meat, etc. It dissolves in alkalies, forming compounds called phetiates. Potassium phenate crystallizes in white needles; when it is heated with iodides of ethyl, methyl, etc., double ethers are formed, as methyl- phenate, CeHeOCHa. Chlorine, bromine, iodine, and nitric acid form with it sub- stitution compounds. Phenol is benzene with one molecule of (OH) substituted for one atom of H. CARBON, a tetrad, non-metallic ele- ment, symbol C. At. wt., 12. Carbon oc- curs in three allotropic forms — two crystalline (diamond and graphite), and one amorphous (charcoal). Diamond crystallizes in forms belonging to the regular system. It is transparent, either colorless, or yellow, pink, blue, or green. The hardest substance known, refracts light strongly, is infusible, but is burned into CO2 in oxygen gas at white heat. Sp. gr., 3.5. It is a non-conductor of electricity. It is found in gravel in India, Brazil, etc. Graphite crystallizes in six-sided prisms. Sp. gr., 2.3. It is gray-black, with a metallic luster. It is a good conductor of electricity. Graphite often separates in scales from molten iron; it is used for lead pencils; it is often called black-lead. Amorphous car- bon occurs more or less pure in lamp- black, wood charcoal, coal, coke, and ani- mal charcoal. Sp. gr., from 1.6 to 2. It is porous, absorbs gases, removes color from organic liquids, is used as a disin- fectant, and bums in the air at red heat, forming CO2. When boiled with YL,S>0*, it is oxidized to CO, and SO2 is also formed, which escape in gas used as a
- reducing agent. Carbon forms two
oxides with oxygen, CO and COl-, car- bonic oxide and carbonic anhydride. The compounds of this element are more numerous than those of all the other ele- ments taken together. With hydrogen especially it forms a very large number of compounds, called hydrocarbons, which are possessed of the most diverse properties, chemical and physical. With oxygen, carbon forms only two com- pounds, but union between the two ele- ments is easily effected. It is one of the regular and most characteristic constitu- ents of both animals and plants. CARBONATES, compounds formed by the union of carbonic acid with a base, as the carbonate of lime, the carbonate of copper, etc. Carbonates are an im- portant class of salts, many of them be- ing extensively used in the arts and in medicine. CARBONDALE, a city in Lackawanna CO., Pa., on the Lackawanna river, and the Erie, the New York, Ontario and Western, and the Delaware and Hudson railroads; 16 miles N. E. of Scranton. It is in the center of an extensive coal- mining district; and contains many ma- chine shops, car shops, foundries, etc. Carbondale has a National bank, several churches, a Roman Catholic academy, several newspapers, etc. Pop. (1910) 17,040; (1920) 18,640. CARBON DISULPHIDE, or BISUL- PHIDE, a colorless liquid produced by burning carbon in an atmosphere of sul- phur, or by distilling certain of the metallic sulphides with charcoal; sp. gr. 1.268. It is of great use in a large variety of manufacturing processes, and as a solvent. CARBONIC ACID (CO2), more prop- erly called Carbonic Anhydride, or Car- bon Dioxide, a gaseous compound of 12 parts by weight of carbon and 32 of oxygen, colorless, without smell, 22 times as heavy as hydrogen, turning blue lit- mus slightly red, and existing in the at- mosphere to the extent of 1 volume in 2,500. It is incapable of supporting combustion or animal life, acting as a narcotic poison when present in the air to the extent of only 4 or 5 per cent. It is disengaged from fermenting liquors and from decomposing vegetable and ani- mal substances, and is largely evolved from fissures in the earth, constituting the choke-damp of mines. From its weight it has a tendency to subside into low places, vaults and wells, rendering some low-lying places uninhabitable. It has a pleasant, acidulous, pungent taste, and aerated beverages of all kinds — beer, champagne, and carbonated mineral water — owe their refreshing qualities to its presence, for though poisonous when taken into the lungs, it is agreeable when taken into the stomach. This acid is formed and given out during the respira-
