⚫020

0.3088 25.967 0.3343 28.111

If this took place in the preparation of oxygen, the solution obtained by extracting the residue with water would contain manganese, which is not the case. Moreover, manganous chloride cannot exist at a high temperature in the presence of potassic chlorate, for it is immediately transformed into an oxide with evolution of chlorine. If the chlorine, which might be produced by the action of the peroxide directly on the chlorate, is thus absorbed by the manganate, it fully explains the very small quantity of chlorine that is evolved, for in the case in which the largest proportion was found (IX), when precipitated peroxide was used, it corresponds to only 6 per cent. of the peroxide present, and as the action in this case was of a very violent character it is not improbable that much of the chlorine was due to the subsequent action of the peroxide on the potassic chloride. In the experiment in which granular oxide was used and the mixture heated over a gas flame (V), the quantity of chlorine corresponds to little more than 1 per cent. of the peroxide.

The table (p. 191, et seq.) contains the details of the experiments referred to in the paper; they are not, however, given in the order in which they were actually made.

XXVI. Contributions to the Chemistry of Lignification. Constitution of the Jute Fibre-substance.

By C. F. CROSS and E. J. BEVAN.

SINCE the publication of earlier papers on this subject (Trans., 1882, 90; 1883, 18) we have continued to prosecute our researches in various directions, certain of which have led to results from which more positive conclusions may be drawn as to the molecular constitution of this group of compound celluloses. Of these we proceed to give a short account. The investigations have been, for the most. part, confined to the jute-fibre, than which we have found no better representative of the group of lignified celluloses. With regard to the term lignocellulose, we should, perhaps, explain at this point, that it recommends itself as being a sufficient description, without containing any suggestion as to the nature of the process by which they are formed, and which we do not think, speaking from the chemical point of view, is by any means completely elucidated.

Although from its nature the jute-fibre is an aggregate, it exhibits, notwithstanding, the constancy in composition and properties which

18 9

denote a chemical individual. The simplest expression of its elementary composition is the empirical formula C12HO, (C = 47·0, H= 6·0, 0 = 47·0); whilst its proximate resolution into cellulose (78—80 per cent.) and non-cellulose (20-22 per cent.), may be represented by the formula 3C,H1005, C6H6O3. For the moment, we advance this as a statistical rather than a molecular expression, leaving it to the experimental evidence to be adduced to show in what degree it is established in the latter and more definite aspect. We shall show, in the first instance, that the more oxidisable constituents of the jute-fibre, to which is applied the neutral term non-cellulose, are compounds, or a compound characterised by an atomic ratio,* approximating to C¿ : H。 : 0з, and associated with the cellulose in chemical rather than mechanical union.

The intimate nature of this union is shown first in its resistance to the action of all simple hydrolytic agents. The alkalis in aqueous solution, the dilute mineral acids, such as have neither oxidising nor reducing properties, attack the fibre in proportion to temperature and duration of action. The result is a solution of the fibre substance, in quantity from 1 to 30 per cent. of its weight, according to the conditions, but without producing any essential chemical change in the insoluble residue (Trans., 1882, 100). In illustration of this point, we cite here the results of the "mercerising" treatment (Watts's Dictionary, New Edition, "Cellulose "), as applied to the jute-fibre.

The structural changes attending the action are profound, as they are in the case of cotton. The individual fibrils increase in thickness at the expense of length to the almost entire obliteration of the central canal; at the same time the union of the fibrils into bundles is more or less completely resolved, and the splitting up of the bundles is accompanied by the development of a wavy outline.

The empirical formula actually deduced from the experimental results given in this paper is C76H80O37 (see pp. 207 and 213).

The cellulose in these determinations serves as a constant to which to refer possible variations of the non-cellulose.

that, with the increased softness, the increased fibre has an external resemblance to wool. This increased softness is to be noted as a distinction from the pectic fibres or pecto-celluloses, which are hardened by such treatment. Reverting to the chemical features of these hydrolytic changes, the product does not differ in any essential point from the original fibre; the aggregate composition (C,H,O), the proportion of cellulose to non-cellulose, and the characteristic properties of the latter persist unchanged.

The structural changes determined by the dilute acids, on the other hand, are opposite in character. The fibre substance surviving undissolved is converted into a hard friable modification, fracture taking place across the fibre bundles which are not resolved by the treatment. But the chemical feature of resistance of the combined molecule to hydrolytic resolution is equally characteristic in relation to this group of reagents.

The dissolution of the fibre substance in the ammonio-copper reagent, when carried out fractionally, also fails to resolve the compound molecule in question. In short, the fibre-substance is to be regarded as an aggregate, only in the sense that some portions (or molecules) are more susceptible of hydration than others, and although these may be attacked and dissolved wholly or in part by hydrolytic agents, they are not decomposed, but preserve intact their essential characteristics, which are those of the original fibre-substance.

The force of this conclusion is not diminished by the consideration of the resolutions effected by hydrolytic agents other than those above mentioned, or by these agents under extreme conditions of temperature. Thus, dilute nitric acid at 60°, sulphurous acid (7 per cent. solution) at 90-100°, and the aqueous alkalis at high temperatures, resolve it into cellulose and non-cellulose (soluble), at the same time attacking the cellulose more or less. But in these cases other conditions, whether of oxidation, reduction, or dehydration (condensation), are superadded, and our conclusion as to resistance of the lignocellulose molecule to simple hydrolysis, is unaffected by the results.

Secondly. In those reactions of the fibre substance which depend on its alcoholic characteristics (OH-groups), its molecular homogeneity is equally manifest. We give the statistics of the conversion of the lignocellulose into nitrates under varying conditions.

(a.) Nitrating acid: mixture of equal volumes of nitric acid (sp. gr. 1-43) and sulphuric acid (sp. gr. 1.8). Temp. 18°.