A Text-book of Paper-making. C. F. Cross
body have, however, been but slightly studied, and apparently not at all with the view to elucidate anything respecting the constitution of cellulose itself.
Cellulose and Chlorine.
—Dry chlorine gas has no action upon cellulose, but the presence of water determines an indirect oxidising action. This oxidising action results from the decomposition of water by chlorine with formation of hydrochloric acid and liberation of oxygen. The reaction, however, can only take place in the presence of light.
Cellulose and Oxygen.
—When cotton is exposed for some time to the action of a solution of bleaching powder, in the cold, and with access of air, e.g. when a piece of white calico is moistened with the solution, squeezed out and exposed to the air, it is found to undergo gradual disintegration accompanied by a change in composition, and an elementary {11} analysis of the product shows it to contain less carbon and more oxygen than the original cellulose. The following percentage numbers indicate the composition of these oxidised derivatives of cellulose, and the progress of the oxidation:—
| 12 hours’ exposure. | 24 hours’ exposure. | |
|---|---|---|
| C | 43·78 43·47 | 43·00 42·90 |
| H | 5·85 6·13 | 6·28 6·18 |
| O | 50·37 50·40 | 50·72 50·92 |
Other oxidising agents produce similar results; even by exposure to air and light, cellulose is slowly converted into these oxidised derivatives.2 From their mode of formation, they have been termed oxycelluloses, and to distinguish them from a series of more highly oxidised derivatives, produced by the action of nitric acid upon cellulose, which they nevertheless resemble in many of their characteristics, the prefix α is employed. The following are the distinguishing features of the α oxycelluloses as represented by the more extreme of the above mentioned products. It reduces Fehling’s solution at the boiling temperature, and the cuprous oxide is deposited upon the fibre in a state of intimate union, producing the effect of an orange dye. It attracts the basic colouring matters from their solutions and is dyed to a full shade, the depth of colour being proportionate to the amount of oxidation to which the cellulose has been subjected. See also p. 43. Treated with a warm solution of phenylhydrazine salts in water, it is coloured a bright lemon-yellow. Its most remarkable property is its attraction for the vanadium compounds, which is so powerful that combination may be proved to take place when this element in the form of chloride is presented to the oxycellulose in an aqueous solution containing not more than 1 in 1,000,000,000,000 parts.
2 Witz. Bull. Soc. Ind. Rouen, X. 416, and XI. 189.
The β oxycellulose resulting, as already indicated, from the action of dilute nitric acid upon cellulose, will be subsequently considered, under the head of the decompositions of cellulose, to which the reaction which we have been considering may be regarded as transitional. {12}
Decomposition of Cellulose.
—Acids.—Of the decomposition of cellulose by artificial means, i.e. by the action of reagents, the most important are those which disclose the relationship which it bears to the group of so-called carbo-hydrates. Cellulose is, indeed, a highly elaborated carbo-hydrate, differing from dextrin and starch, not so much in its essential constitution as in the molecular arrangement which has been impressed upon it in and through the life of the plant. There are numerous observations in biological science which demonstrate the close connection, and in many cases the physiological equivalence of the members of this natural group, which includes the sugars, dextrin, starches, and cellulose. The following facts show the constitutional or chemical ties which underlie their interdependence.
Amyloid.
—When cotton is treated with 30 times its weight of sulphuric acid somewhat diluted (1 part H2O, 4 parts H2SO4) it quickly dissolves, the solution being at first gelatinous, becoming afterwards syrupy. On pouring this solution into water, a white flocculent precipitate is formed, consisting of a substance closely resembling the cellulose from which it is derived, differing, indeed, only in being amorphous, and in being coloured blue by iodine. This substance, from its resemblance to starch, has been called amyloid. When sufficiently dehydrated it constitutes a swollen starchy mass, which dries to a brittle transparent solid. This transformation appears to consist in a simple hydration of the cellulose molecule, thus:—2 (C6H10O5)
Cellulose.
+
H2O
=
C12H22O11.
Amyloid.
The modification of cellulose, which occurs on the conversion of unsized paper into the so-called parchment paper, by exposure for a short time to the action of strong sulphuric acid, and subsequent washing and drying, consists doubtless in a superficial conversion of the cellulose into amyloid, or a body closely resembling it.
Hydracellulose.
—Closely related in composition to the above {13} described amyloid, is the substance called hydracellulose, into which cellulose is converted by exposure for some time to the action of moderately strong sulphuric, or hydrochloric acids (sp. gr. 1·35). This substance is also formed by the action of very weak acids, if the exposure of the cellulose be sufficiently prolonged. Its formation is accompanied by the complete disintegration of the cellulose. If the action of strong sulphuric acid be prolonged, a further modification ensues, dextrin or sugar being formed. These products have not been sufficiently studied to have established their exact identity with any of the substances known under these group-names. The dextrin has a close resemblance to the dextrin obtained from starch; the sugar is susceptible of fermentation; but beyond this nothing specific is known of these bodies. Their general properties, however, and mode of formation, sufficiently establish the fact that cellulose itself is constituted of similar molecules.
The action of zinc chloride solution upon cellulose is similar to that of sulphuric acid.
Cellulose in contact with iron, and in presence of air and moisture, is converted into a sugar and a gummy substance, which latter is converted into a sugar on boiling with dilute acids. Oxidised by potassium permanganate or bichromate in presence of acetic acid, it is converted into glucose, dextrin, and formic acid.
Cellulose and nitric acid: β Oxycellulose.*