A Text-book of Paper-making. C. F. Cross
has an enormous industrial application for the coarser textile purposes. The chemistry of jute throws light on the course of lignification, the process by which cellulose is modified into wood, and in studying it in preference to wood we have the advantage of studying a simple tissue.
Like cellulose, jute dissolves in cuprammonia, and is similarly acted upon by the concentrated acids. By nitric acids it is converted into nitric ethers, which are yellow coloured, but in other respects closely resemble the pyroxylins. They are entirely soluble in acetone.
Jute differs from cellulose in the following respects: its percentage composition (excluding ash) is
| C | 47·0 | 48·0 | per cent. |
| H | 5·9 | 5·7 | „ |
| O | 47·1 | 46·3 | „ |
It is harsher to the touch, and its colour varies from grey to brown; it combines directly with the greater number of the organic colouring matters, removing them from solution, i.e., becoming dyed with them; it is coloured deep yellow by immersion in a solution of aniline sulphate; moistened with a solution of phloroglucol and afterwards with hydrochloric acid, it gives a deep red coloration; with pyrrol also in presence of hydrochloric acid it gives a deep carmine colour; it is attacked and partially converted into soluble products by a number of reagents which have no action, under similar conditions, upon cellulose. Certain of these we must consider more in detail.
Iodine.
—Jute absorbs iodine from its solution in potassium iodide. This action is characteristic of all lignified tissues, the quantity of iodine taken up being proportional to the amount of lignification. If the physical conditions remain the same, the amounts of iodine absorbed will be found to be constant for each particular fibre. This constancy points to the formation of a definite chemical compound, probably resembling the blue compound of starch and iodine. This property may be made available for the estimation of the {18} amount of mechanical wood-pulp in papers; it will be more fully considered elsewhere.
Bromine.
—Jute, exposed to the action of bromine water in the cold, combines with the halogen, being oxidised at the same time, and the products may be dissolved by boiling the modified fibre in weak alkaline solutions. On repeating this treatment four or five times, a residue of cellulose is ultimately obtained, amounting to 72 or 73 per cent. of the original fibre: the cellulose is obtained in the form of the disintegrated fibre elements. On allowing the halogen to act in presence of an alkali, i.e., as hypobromite, not only is its action intensified and accelerated, but its modus operandi more clearly revealed. The chief products are in this case, carbonic acid, bromoform CHBr3 (which may be isolated by distillation), and cellulose. At the same time the yield of cellulose is considerably less than by the former method, the cellulose itself being attacked by the hypobromite.
Chlorine.
—Dry chlorine gas has no action upon jute even when the temperature is raised to 140° C. (284° F.), but the presence of moisture determines rapid combination, at ordinary temperature, accompanied by evolution of heat. The colour of the jute changes to a bright yellow, which, on treatment of the fibre with a solution of sodium sulphite, gives place to a pure magenta. This reaction is characteristic of all lignified tissues, and is a valuable aid in the micro-chemical examination of plant structures. For this purpose, the reagent may be employed in the form of chlorine water; the sections or small fragments to be examined are allowed to remain in this solution a short time, and then mounted for observation in a dilute solution of sodium sulphite. By combination with chlorine the fibre substance or ligno-cellulose is partially resolved. Alcohol dissolves away from the chlorinated fibre, a bright yellow substance, which is precipitated in yellow flocks on pouring the solution into water. This chlorinated derivative has the composition C19H18Cl4O9. By this formula, as well as by its colour reactions, and by its yielding protocatechuic acid on fusion with potash, it is {19} shown to be related to the trihydric phenols, and to the tannins which are derivatives of these.
After dissolving away this compound by exhaustive treatment with alcohol, the fibre still gives a brilliant reaction with sodium sulphite, showing that a portion is still held back in combination with the cellulose, or cellulose residue. On treating the residual fibre with boiling nitric acid, a considerable quantity of chloropicrin CCl3NO2 is formed, and it is probable that the union of the molecule C19H18Cl4O9 with the cellulose may be effected by the aldehyde5 molecule CCl3COH; each group being contained in the original lignocellulose, the action of the chlorine tending to disturb the atomic equilibrium and to rearrange the atoms into groups, which in their modified form have less mutual coherence. If the chlorinated fibre be directly boiled with the sodium sulphite solution, its resolution into cellulose and soluble non-cellulose derivatives is complete: and this treatment constitutes the most simple and rapid method of estimating the cellulose in lignified tissues. It is only necessary finally to wash the cellulose with hot water containing a little acetic acid (when placed in a funnel it acts as its own filter), and then with, alcohol, when it may be dried and weighed. In order to ensure the resolution of the fibre by a single chlorination (in the case of jute, and the like), it must, previously to exposure to the gas, be boiled in a dilute (1 per cent.) solution of potassic hydrate. In the case of wood and other more resistant structures, it will be necessary to repeat the chlorination.
5 Furfural may also be isolated from the chlorinated jute; the survival of this aldehyde is noteworthy.
The percentage of cellulose yielded by this method is, in the case of jute, usually 2–3 per cent. higher than by the bromine method. Moreover, if the temperature be maintained at 0° C. (32° F.), by placing the fibre, which is to be exposed to the action of the gas, in contact with pounded ice, the percentage may be still further increased, amounting {20} in some cases to 80–82. Corresponding to this increased yield, the cellulose is obtained in long filaments. It will be seen, therefore, that the cellulose isolated by chemical treatment from a compound cellulose is affected both in character and quantity by the process employed, and it is affected in a much greater degree than the cellulose itself exposed to the same treatment, after isolation. The composition of the cellulose obtained in this way differs from that of celluloses, such as cotton, which exist in the plant in an isolated and more fully formed condition; it contains 43 per cent. C and 6 per cent. H, corresponding to the formula n [3 C6H10O5H2O.] The composition of this cellulose will be seen to be identical with that of certain of the oxycelluloses previously described; and its properties are, moreover, those of an oxycellulose. These facts go to show that the jute fibre substance, and the substances allied to it, are compounds of cellulose with other molecules, i.e. they are compound celluloses. They may be conveniently grouped under the term ligno-cellulose.
Dilute Mineral Acids.
—Under the action of