CELLULOSE, a chemical substance closely allied to starch, which occurs in all plants, where its compounds form essential constituents of the walls of the cells. It is especially prominent in young plants, and with age it becomes more or less completely con verted into lignin and other analogous prod ucts. Cellulose can be readily digested and absorbed by herbivorous animals, but only to a slight extent by man. Cotton fibres are com posed almost entirely of cellulose, and such other substances as they do contain are readily removed by treatment with alkalis, alcohol, ether, etc. Wood and all textile fibres are mostly compounds of cellulose. Cellulose has the chemical formula n (C.1100.), and is there fore a carbohydrate. In some respects, it is widely different from starch, but in others it resembles starch very closely. It may be said in general that the chemistry of all the sub stances that are intimately related to the starches, gums and sugars is still very imper fectly known. Cellulose is specially remark able for its insolubility and its chemical stabil ity. It may be decomposed and caused to enter into combination with other bodies, but the only solvent known, which will dissolve it without destroying its chemical identity, is an ammoniacal solution of cupric oxide. From its solution in this menstruum, cellulose may be again precipitated in apparently unchanged chemical form, though in a physically amor phous condition. Unglazed paper (which is nearly pure cellulose) is converted, by the action of strong sulphuric acid, into a parch ment-like substance that is known as vegetable parchment, or parchment paper. By the action of a mixture of strong nitric and sulphuric acids, cellulose is converted into nitrates, the higher ones of which are commercially known as gun-cotton (q.v.). Collodion (q.v.) is a solution of the lower nitrates in a mixture of ether and alcohol. Celluloid (q.v.) is a mixture of the lower nitrocelluloses with camphor.
Acetates of cellulose are formed by treatment with acetyl chloride, and are often used as substitutes for celluloid, being less inflammable, and as insulating films. Formates are also used in this way. Xanthogenates of cellulose are used in the production of certain forms of artificial silk, leather and wood. Alkalis react with cellulose, causing it to contract (see MERCERIZED Corrox). By the prolonged action of sulphuric acid cellulose is partially converted into glu cose, and various' other reactions are also known with sulphuric acid according to the conditions under which the experiment is made. When strongly heated out of contact with the air cellulose is destroyed, with the formation of acetic acid, methyl alcohol and many other products. These transformations occur in the distillation of wood in the manufacture of wood alcohol. (See ALCOHOL). It is probable that true cellulose occurs only in plants; but a substance that is closely analogous to it, and which is believed by some authorities to be identical with it, is found in the tissues of ascidia.
Cellulose as prepared from corn pith has been used to a considerable extent in ships of war, to prevent the entrance of water through shot-holes. For this purpose it is disposed within the steel hull along the water line, in the form of a belt some three feet in thickness. For several years a packing of cocoa fibre was used in this way, but corn pith is now preferred, because as soon as the water reaches it the pith swells and automatically closes the shot-hole. Consult Bersch, (Cellulose) (Philadelphia 1904) ; Cross and Bevan, (Cellulose) (London 1895) ;