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Encyclopedia Britannica - Main :: CAU-CHA |
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CELLULOSE , the name given to both an individualcellulose proper, in the restricted sense of a chemical individualand to a group of substances, the celluloses or cellulose group, which constitute in infinitely varied forms the containing envelope of the plant cell. They are complex carbohydrates, or " saccharocolloids " (Tollens), and are resolved by ultimate hydrolysis into monoses. The typical cellulose is represented by the empirical formula
starch
cotton
paper (Swedish) is practically pure cellulose, the final purification consisting in exhaustive treatment with hydrofluoric acid to remove silicious inorganic residues. The " cellulose " group, however, comprises a series of substances which; while presenting the characters generally similar to those of cotton
wall
The celluloses proper are essentially non-nitrogenous, though originating in the cell protoplasm. The cell-walls of the lower cryptogams, similarly purified, retain a notable proportion -2o-4.0%of constitutional nitrogen. When hydrolysed these fungoid celluloses yield, in addition to monoses, glucosamine and acetic acid. The celluloses of the phanerogams are generally associated, in a degree ranging from physical mixture to chemical union, with other complicated substances, constituting the " compound celluloses. The nature of the associated groups affords a convenient classification into pecto-celluloses, ligno-celluloses and cuto-celluloses. Pectocelluloses are so named because the associated substancescarbohydrates, together with their oxidation products, i.e. containing either two carbonyls (CO) in the unit group or carboxyl (CO.OH) groups in a complexare readily hydrolysed by weak acids to the gelatinous " pectic acids " or their salts. Ligno-celluloses are the substances of lignified tissue , the van-cellulose constituents of which are characterized by the presence of benzenoid and furfuroid groups; and although essentially complex,they may be regarded as homogeneous, and are conveniently grouped under the name lignone. The lignone complex reacts, by its unsaturated groups, with the halogens. It is a complex containing but little hydroxyl; and is of relatively high carbon percentage (s5.0-57.0%). Culo-celluloses predominate in the protective coatings of plant organs, and are characterized by constituent groups, the decomposition products of which are compounds of the fatty series , and also wax alcohols, acids, cholesterols, &c.The typical pecto-cellulose is the flax fibre, i.e. the bast fibre of the flax plant (Linum usitatissimum), as it occurs in the plant, or as the commercial textile fibre in its raw state. Rhea, or ramie, is another leading textile fibre in which the cellulose occurs associated with alkali-soluble colloidal carbohydrates. Pecto-celluloses are found in the stems of the Gramineae (cereal straws, esparto), and in the fibro-vascular bundles of monocotyledons used as textile and rope-making fibres. They are the chief
Cellulose andBotanicalScience.-Theelaboration of cellulose, i. e. of the cell walls, and its morphological and physiological aspects are discussed in the articles PLANTS: Physiology, Anatomy: and CYTOLOGY; while in the article COAL the part played by cellulose in the formation of these deposits receives treatment: here we may deal with its general relation to agriculture. In the analysis of fodder
SEEDS Seeds of Cereals. Per cent of Leguminous and Per cent of Fibre. Oil Seeds. Fibre. Wheat 2.8 Rape 6.4 Barley 6.3 Cotton 7.5 Oats . 9.0 Beans . . Ioo Maize . 5.2 Peas . Ioo Rye 8o Lentils loo Rice . 2.5 Vetches 7.2 End of Article: CELLULOSE If you wish, you can link directly to this article.
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