Carbon atomic weight, 12 meltingpoint, above 3,600 degrees C.is well known in the three forms of the diamond, graphite, and charcoal. It is also found widely distributed in nature, not only as a constituent of animal and vegetable tissues, and in the air ,n the form of carbon dioxide 2, but also in combination as calcium carbonate in the rocks known as limestone and dolomite. Diamonds are found in many deposits in Brazil, India, South Africa, and elsewhere, and are for the most part colourless, but sometimes tinged with various colourings. Minute diamonds have been made artificially on a very small scale, and proved to have the same composition as the natural diamonds. When strongly ignited, diamonds burn up in the presence of oxygen into carbon dioxide, just as charcoal does at a lower temperature, thus proving them to consist of carbon. Graphites found plentifully in nature in Canada, Japan, Siberia, Spain, California, Ceylon, and elsewThere, including Borrowdale in Cumberland, where it is used in the preparation of pencils. It is a shiny, soft, nearly black substance consisting mainly of carbon, and on account of its refractory character it is used for the manufacture of socalled plumbago cruciblesthat is, crucibles made of fireclay mixed with graphiteand arclight carbons. It is also employed as a polish and coating for iron articles to prevent rusting, and as a paint pigment. Carbon is also known in impure form as coke, lampblack, and animai charcoal, and this lastnamed substance is used in refining sugar, glycerine, fats, etc., to decolorize the solutions, having the property of taking up many kinds of colouring matters. In this property, birch rharcoaldust is stated to lie equally efficient. Animal charcoal prepared from bones contains about 81 per cent, of calcium and magnesium phosphates and calcium fluoride, from 7 to 8 per cent, of calcium carbonate and other salts, and from 10 to 11 per cent, of carbon. Most of the carbon black used in the United States of America in the preparation of inks, polishes, pigments, and the rubber industries, is now made by the. incomplete combustion of natural gas in air. It is of a velvety black character, but only a small percentage of the total carbon is recovered namely, from iJto 3 per cent. Charcoal has the property of absorbing gases very readily, wood and peat charcoal being superior in this respect to animal charcoal. The absorptive power of wood charcoal is notably increased by prolonged heating, and the denser charcoalsnotably those from palmnut, cocoanut, and fruit stonesare the most efficient gas absorbents. The following table shows the capacity of absorption of various gases by boxwood charcoal: Water is not adsorbed by charcoal, but absorbed or held by capi lary action, and the adsorptive power of charcoal varies with the method of its preparation within very wide limits. The adsorption of oxygen by charcoal is considered due to a surface action, the product being a kind of car bon oxide which upon heating, breaks up into carbon monoxide and carbon dioxide, so that it has to be regarded as an intermediate compound in the combustion of the charcoal. “Char” does not only adsorb colour from complex solutijns, but will retainsometimes with great avidity many mineral and organic compounds, such as the alkaloids, for which, indeed, purified animal black is an antidote. All vegetable matters consist, in part, of carbon in chemical combination with hydrogen and oxygen, and when they are burned with an insufficient quantity of aii or oxygen, a Ammonia gas… Hydrochloric acid gas Sulphur dioxide gas Hydrogen sulphide gas Carbon dioxide gas Oxygen gas…mass of “char,” or carbon, remains behind. For example, when wood is burned in a smothered sort of waythat is, with an insufficient quantity of air or oxygena part of it is left behind in the form of woodcharcoal; in fact, that is how charcoal is prepared. Of course, if enough oxygen or air is supplied to burning wood or coal, all the carbon becomes consumed b> entering into combination with the oxygen, and only the ash is left, This ash consists of mineral matters which were present in the wood and coal before burning. Vegetable MattersThere are an immense number of vegetable substances and products, such as sugar, rosin, starch, gum, linseed oil, castor oil. cocoanut oil, various fats, essential oils, and colouring matters, all of which consist of chemical compounds of carbon with hydrogen and oxygen. All these products of vegetable life are built up by chemical processes which take place in their living organisms, and are derived from the carbon dioxide absorbed from the soil and air by their roots and other partsstomata, or small openings on the lower surface of leavesand this fact demonstrates very forcibly the importance of that substance as a constituent of the atmosphere. Many of these products can be built up artificially by means of synthetical processes, showing that these natural processes are essentially of the same order as other chemical processes, although very complicated and at present imperfectly understood. Amongst the substances that have been produced by chemists may be mentioned formaldehyde, urea, alcohol, gljcerine, tartaric acid, indtgotine, vanillin, alizarin, indiarubber, and coumarin also many synthetical perfumes, the manufacture of which has become an important industry. We may well be excited to wonder by the marvellous extent and nature of the structures, the tissues, the colouring matters and the products that characterize vegetable life, all of which are built up out of the constituents of the soil and the air by the living agencies contained in their seeds. These wonderful processes of nature may be compared with the determining force that causes many salts in a state of solution to crystallize out therefrom in such beautiful geometrical or symmetrical forms as referred to in another section. Animal MattersOther organic compounds are found to exist in all parts of the flesh, the brains and other parts of animals, but sometimes phosphorus is also found in association, and these organic compounds are even more complex. By animals we mean not only human beings, but all beasts, birds, fishes, and insects. Compounds, of which carbon forms an important constituent, are generally termed organic, and all of them are combustiblethat is to say, they can be burned up if heated sufficiently in the presence of plenty of air or oxygen.
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