Chapter 12

~Cellulose.~--There is little doubt that the furfural-yielding groups of the original are isolated in the form of the beta-cellulose. Tollens emphasises this fact in his studies of cellulose-estimation methods. We had previously shown (original, p. 159) that the yield of furfural is not affected by the _chlorination_, but it appears from our numbers that only 50 p.ct. of these groups remain in the isolated cellulose, the residue undergoing hydrolysis to soluble compounds. In a carefully regulated hydrolysis following the chlorination it appears that the furfuroids are almost entirely conserved in the form of a cellulose.

Moreover, an investigation of the products dissolved by sodium sulphite solution from the chlorinated fibre has shown that they are practically free from furfuroids. This enables us to exclude the furfural-yielding groups from the lignone complex. At the same time, through our later studies of the hydroxyfurfurals, it is certain that these products are represented in the fibre substance and probably in the lignone complex.

~Chlorination Statistics.~--It has been pointed out by a correspondent--to whom we express our indebtedness--that we have made a mistake in calculating the proportion of lignone from the ratio of the Cl combining with the fibre substance or lignocellulose (p.ct), to that of the Cl _present in_ the isolated lignone chloride (p.ct.). The lignocellulose combines with chlorine in the ratio 100 : 8, but the lignone chloride _containing_ 26.7 of chlorine means that, neglecting the hydrogen substituted, 73 of lignone combine with the 27 of chlorine approximately. On the uniform percentage basis the calculated proportion of lignone would be 8/37, or a little over 20 p.ct.

In regard to the proportion of hydration attending the resolution, we have shown on constitutional grounds that this must be relatively small. Assuming approximately the formula C_{19}H_{22}O_{9} for the lignone residue as it exists in combination, and the anhydride formula for the cellulose, these revised statistics now appear, as regards the carbon contents of the lignocellulose:

Cellulose, 44.4 C; lignone, 57.8. 80 × 44.4 ÷ 100 = 35.52 20 × 57.8 ÷ 100 = 11.56 _____

47.08 p.ct. C in lignocellulose.

These conclusions are in accordance with the experimental facts, and, taken together with the new evidence we have accumulated from a study of the lignocellulose esters, we may sum up the constitutional points as follows: The lignocellulose is a complex of

Cellulose alpha Cellulose beta Lignone 65 p.ct. 15 p.ct. 20 Allied to the normal Yielding furfural One-third of which celluloses approximately 50 p.ct. is of benzenoid type

The lignone contains but little hydroxyl. The celluloses are in condensed hydroxyl union with the lignone, but the combination occurs by complexes of relatively large molecular weight.

DIE CHEMIE DER LIGNOCELLULOSEN--EIN NEUER TYPUS.

W. C. HANCOCK and O. W. DAHL (Berl. Ber., 1895, 1558).

~Chemistry of Lignocelluloses--A New Type.~

The stem of the aquatic _Æschynomene aspera_ offers an exceptional instance of structural modification to serve the special function of a 'float,' 1 grm. of substance occupying an apparent volume of 40-50 c.c. This pith-like substance is morphologically a true wood (De Bary), and the author's investigations now establish that it is in all fundamental points of chemical composition a lignocellulose, although from its colour reactions it has been considered by botanists to be a cellulose tissue containing a proportion of lignified cells. Thus the main tissue is stained blue by iodine in presence of hydriodic acid (1.5 s.g.), and the colour is not changed on washing. The ordinary lignocelluloses are stained a purple brown changed to brown on washing. The reactions with phloroglucol and with aniline salts, characteristic of these compounds, is only faintly marked in the main tissue, though strongly in certain individual cells.

The following quantitative determinations, however, establish the close similarity of the product to the typical lignocelluloses:

_Elementary Analysis._--C 46.55, H 6.7. _Furfural_ 11.6 p.ct., of which there remained in the residue from alkaline hydrolysis (71 p.ct.) 8.0, i.e. about 70 p.ct. The distribution of the furfuroids is therefore not affected by the alkaline treatment.

_Chlorination._--The substance (after alkaline hydrolysis) takes up 16.9 p.ct. Cl, of which approximately one-half is converted into hydrochloric acid.

_Methoxyl._--O.CH_{3} estimated = 2.9 p.ct.

_Ferric Ferricyanide Reaction._--Increase of weight due to blue cyanide fixed (1) 75 p.ct., (2) 96 p.ct. Ratio, Fe : CN = 1 : 2, 4.

_Hydroxyl Reactions._--In the formation of nitric esters and in the sulphocarbonate reaction the substance gave results similar to those obtaining for the jute fibre.

These results establish the general identity of this peculiar product of plant life with the lignocelluloses, at the same time that they show that certain of the colour reactions supposed to characterise the lignocelluloses are due to by-products which may or may not be present.

(p. 172) ~Composition of Elder Pith.~--In a systematic investigation of the celluloses in relation to function we shall have to give special attention to the parenchymatous tissues of all kinds. These are, for structural reasons, not easily isolated, for which reason and their generally 'inferior' functions they do not present themselves to chemical observation in the same obvious way as do their fibrous relatives. The pith of the elder, however, _is_ readily obtained in convenient masses, and a preliminary investigation of the entire tissue has established the following points:

The _reactions_ of the tissue are in all respects those of the lignocelluloses.

_Composition._--Ash, 2.2 p.ct.; moisture in air-dry state, 12.3 p.ct. Alkaline hydrolysis (loss): (a) 14.77, (b) 17.84. Cellulose (yield), 52.33 p.ct. Nitrate-reaction complicated by secondary reactions and yields low, 90.95 p.ct. _Sulphocarbonate reaction:_ Resists the treatment, less than 10 p.ct. passes into solution.

_Furfural._--The original tissue yields 7.13 p.ct.; the residue from alkaline hydrolysis (b) 5.40 p.ct.

This tissue is, therefore, a lignocellulose having the chemical characteristics typical of the group, but of less resistance to hydrolytic actions.

The investigation will be prosecuted in reference to the cause of differentiation in this latter respect. Probably the pectocelluloses are represented in the tissue.

~The Insoluble Carbohydrates of Wheat (grain).~

H. C. SHERMAN (J. Amer. Chem. Soc., 1897, 291).

(p. 171) This is a study of the constituents of the cell-walls of wheat grain. Bran was taken as the most convenient form of the raw material, being freed from starch by treatment with malt extract, and further treated (1) with cold dilute ammonia, (2) cold dilute soda lye (2 p.ct. NaOH), and (3) boiling 0.1 p.ct. NaOH. The product retained only 1.25 p.ct. proteids, and yielded 15.62 p.ct. furfural.

_Acid Hydrolysis._--The product was boiled 30 mins. with dilute acid (1.25 p.ct. H_{2}SO_{4}), and the solution boiled until the Fehling test showed no further increase of monoses. At the limit the reducing power of the dissolved carbohydrates was 91.3 p.ct., that of dextrose. Converted into osazones the analysis showed them to be _pure pentosazones_. The _hemicellulose_ of wheat is, therefore, according to the author, _pure pentosane_.

_Residue._--This was a lignocellulose yielding 11.5 p.ct. furfural. It was subjected to a series of treatments with ferric ferricyanide, and the proportion of Prussian blue fixed was determined by increase of weight, viz. from 10 p.ct. to 47 p.ct. according to the conditions. The results confirmed those of Cross and Bevan first obtained with the typical lignocellulose (jute).

_Chlorination._-The residue was boiled with dilute alkali, washed, and exposed to chlorine gas. The resulting lignone chloride was isolated by solution in alcohol, &c. It yielded 26.7 p.ct. Cl on analysis. In this and its properties it appeared to be identical with the product isolated by Cross and Bevan from jute, with the empirical formula C_{19}H_{18}Cl_{4}O_{9}.

_Cellulose_ was isolated from the residue by three of the well-known methods, and the following comparative numbers are noteworthy:

_________________________________________________________________________ | | | | | | | F. Schulze | Lange | Cross and | | Method | Dil. HNO_{3} | Fusion KOH | Bevan | | | KClO_{3} | | Chlorine, &c. | |_____________________________|______________|____________|_______________| | | | | | | Cellulose p.ct. obtained | 66.0 | 39.3-43.1 | 66.5 | | Furfural p.ct. of cellulose | 7.0 | 3.96 | 5.62 | | Residual nitrogen | 0.22 | 0.03 | 0.00 | | Ferricyanide reaction, | | | | | Prussian blue fixed | 6.04 | 0.89 | 0.92 | |_____________________________|______________|____________|_______________|

The author remarks: 'It is evident no one feature can be urged as a criterion in judging between the methods, but all must be taken into consideration. Such a comparison shows the superiority of the chlorination method.'

The cellulose is not of the normal (cotton) type, since on treatment with sulphuric acid it dissolves with considerable discolouration, but only to the extent of about 80 per cent. The dissolved monoses converted into osazones were found to consist of hexoses only. The cellulose treated with caustic soda solution (5 p.ct. NaOH) in the cold yielded 20 p.ct. of its weight of soluble constituents, but as the residue yielded 3.34 p.ct. furfural the attack of the alkali is by no means confined to the furfuroids.

~Animal Digestion of the Constituents of Bran.~--Observations on a steer fed upon wheat bran only established the following percentage digestion of the several constituents:

Soluble carbohydrates 96.9 Starch 100.0 Free pentosanes 60.2 Cellulose 24.8 Lignin complex 36.7 Proteid 82.96 Ether extract 42.73 _____________________ ______

Nitrogen-free extract 76.08 Crude fibre 32.21

JOURNAL OF THE IMPERIAL INSTITUTE

(Research Department, Vols. 1-2, 1895-6).

(p. 109) In this journal appear a series of notices of the results of analyses of vegetable fibres by the method described in 'Report on Miscellaneous Fibres' (Col. Ind. Exhibition Reports, p. 368) [C. F. Cross]. These investigations deal with the following subjects:

1895. p. 29 Various Indian Fibres--more particularly Sida. 118 (a) Fibres from Victoria; (b) Special Analyses of (a) Samples of Jute; (c) Paper-making Fibres from S. Australia. 202 Fibres from Victoria. 287 Fibres from Victoria. 366 Sisal from Trinidad. 373 Rope-fibres from Grenada. (b) 398 Report of Experiments on Indian Jute (1). 435} Fifth and Sixth Report on Australian Fibres. 473} 1896. 68 Hibiscus and Abroma Fibres. 104-5 Hibiscus, Urena, and Crotalaria Fibres. 141 Indian Sisal (c) 182-3 Report of Experiments on Indian Jute (2). 264 Sanseviera from Assam.

From the above we may draw the general conclusion that the scheme of investigation has been found in practice to answer its main purpose, viz. to afford such numerical constants as determine industrial values. In illustration we may cite (a) the results of analyses of specially selected samples of jute, from which it will be seen that there is a close concordance of value as ordinarily determined from external appearance, with the chemical constants as determined in the laboratory.

__________________________________________________________________ | | | | | Quality of Jute | |____________________________|_____________________________________| | | | | | | | | Low | Medium | Extra | Extra Fine | |____________________________|_______|________|_______|____________| | | | | | | | Moisture | 11.0 | 10.4 | 11.1 | 9.6 | | Ash | 0.87 | 2.8 | 1.0 | 0.7 | | Alkaline hydrolysis (a) | | | | | | 5 mins. boiling | 13.2 | 11.6 | 8.5 | 9.1 | | Alkaline hydrolysis (b) | | | | | | 60 mins. boiling | 16.1 | 17.5 | 12.5 | 13.1 | | Mercerising treatment | 9.2 | 10.5 | 10.3 | 8.5 | | Nitration (increase p.ct.) | 36.6 | 35.7 | 37.5 | 36.7 | | Cellulose (yield) | 71.4 | 70.0 | 79.0 | 77.7 | | Acid purification | 2.6 | 1.3 | 1.9 | 2.0 | |____________________________|_______|________|_______|____________|

A useful series of experiments, initiated by the Institute, is that noted under (b) and (c) above.

(1) To ascertain the quality of the fibre extracted from the plant at different stages of growth, quantities of 400 lbs. of the stalks were cut at successive stages and the fibre isolated after steeping 14-20 days. The fibre was shipped to England and chemically investigated, with the following results:

No. 1. Cut before appearance of inflorescence. " 2. " after budding. " 3. " in flower. " 4. " after appearance of seed-pod. " 5. " when fully matured.

_________________________________________________________________ | | | | | | | | | (1) | (2) | (3) | (4) | (5) | |___________________________|_______|_______|______|______|_______| | | | | | | | | Moisture | 11.55 | 8.74 | 10.7 | 10.0 | 9.72 | | Ash | 1.1 | 1.1 | 1.1 | 1.1 | 0.90 | | Alkaline hydrolysis (a) | 6.2 | 8.5 | 9.7 | 8.9 | 7.3 | | " " (b) | 10.5 | 11.9 | 11.6 | 12.0 | 11.2 | | Mercerising treatment | 10.2 | 10.7 | 12.0 | 8.1 | 11.0 | | Nitration | 37.2 | 32.1 | 32.2 | 33.2 | 36.6 | | Cellulose | 74.0 | 76.2 | 74.1 | 74.8 | 76.4 | | Acid purification | 0.8 | 0.5 | 0.7 | 2.4 | 1.4 | |___________________________|_______|_______|______|______|_______|

It will be thus seen that there are no changes of any essential kind in the chemical composition of the bast fibre throughout the life-history of the plant, confirming the conclusion that the 'incrustation' view of lignification is consistent only with the structural features of the changes, and so far as it has assumed the gradual overlaying of a cellulose fibre with the lignone substance it is not in accordance with the facts.

Examination of the samples from the point of view of textile quality showed a superiority of No. 1 in fineness, softness, and strength; from this stage there is observed a progressive deterioration, but the No. 4 sample (which was taken at the usual period of cutting) is superior to No. 5.

In a further series of experiments (c) the jute was subjected to certain chemical treatments immediately after the separation of the fibre from the plant. These consisted in steeping (1) in solution of sodium carbonate, as well as of plant ashes, and (2) in sulphite of soda, the purpose of the treatments being to modify or arrest the changes which take place in the fibre when press-packed in bales for shipment. The samples were shipped from India under the usual conditions and examined soon after arrival. It was found that the chemical treatments had produced but small changes in chemical composition of the fibre-substance. The sulphite treatment was the more marked in influence, somewhat lowering the cellulose and nitration constants. The conclusion drawn from the results was that they afford no prospect of any useful modification, i.e. improvement of the textile quality of the fibre by any chemical treatments such as could be applied to the fibre on the spot before drying for press-packing and shipment.

The other matters investigated in the Institute laboratory and reported on as indicated above are rather of commercial significance, and contributed no points of moment to the chemistry of cellulose.

OBSERVATIONS ON SOME OF THE CHEMICAL SUBSTANCES IN THE TRUNKS OF TREES.

F. H. STORER (Bull. Bussey Inst., 1897, 386).

(p. 172) An examination of the outer and inner wood and of the bark of the grey birch, at different seasons of the year, gave the following yields of furfural p.ct. on the dry substance:

________________________________ | | | | | | Wood | | | |_______________| Bark | | | | | | | | Inner | Outer | | |_________|_______|_______|______| | | | | | | May | 21.3 | 19.6 | 16.7 | | July | 16.6 | 18.8 | 11.4 | | October | 16.2 | 16.3 | 12.3 | |_________|_______|_______|______|

The paper contains the results of treating the woods and various vegetable products with hydrolysing agents in order of intensity: (a) Malt-extract at 60°C., (b) boiling dilute HCl (1.0 p.ct. HCl), and (c) boiling dilute HCl (2.5 p.ct.). The residues were found to yield considerable proportions of furfural. The following numbers are typical:

________________________________________________________________________ | | | | | | Birch | Stones of | | |_____________|__________________________| | | | | | | | | | Bark | Wood | Date | Apricot | Peach | |_______________________________|______|______|________|_________|_______| | | | | | | | | Action of malt extract calcu- | | | | | | | lated as starch dissolved | 4.24 | 3.5 | 5.2 | 1.5 | -- | | | | | | | | | Residue boiled, 1 p.ct. HCl | | | Mannan | | | | gave pentosanes dissolved. | -- | -- | 11.7 | 14.1 | 6.7 | | | | | | | | | Residue yielded furfural | 19.3 | 17.8 | 3.4 | 9.6 | 9.7 | |_______________________________|______|______|________|_________|_______|

The proportion of pentosanes (furfuroids) removed, i.e. hydrolysed by boiling with hydrochloric acid of 2.5 p.ct. HCl, is shown by the following estimations of furfural:

_________________________________________________________________ | | | | | | | Birch | Sugar maple | | | |______________|_______________| Apricot | | | | | | | stones | | | Bark | Wood | Outer | Inner | | | | | | wood | wood | | |________________________|_______|______|_______|_______|_________| | | | | | | | | In original substance | 16.7 | 19.6 | 18.2 | 20.7 | 18.4 | | | | | | | | | In residue from action | 6.53 | 8.6 | 4.9 | 6.4 | 7.0 | | of 2.5 p.ct. HCl | | | | | | |________________________|_______|______|_______|_______|_________|

_Wood Gum._--The paper contains some observations on the various methods of isolating this product. Attention is directed to the necessary impurity of the product, and to the fact that the numbers for furfural and for the xylose yielded by hydrolysis are considerably less than for a pure pentosane.

_Estimation of Cellulose._--The author investigated the process of Lange and the 'celluloses' obtained from various raw materials. The products from the woods of birch and maple contained furfural-yielding constituents, represented by yields of 6-8 p.ct. furfural. Preference is given to the process by comparison with others, at the same time that it is recommended in all cases to examine the product for furfural quantitatively, converting the numbers into pentosane equivalents, and subtracting from the total 'cellulose' to give the true cellulose.

ZUR KENNTNISS DER MUTTERSUBSTANZEN DES HOLZGUMMI.

E. WINTERSTEIN (Ztschr. Physiol. Chem., 1892, 381).

~ON THE MOTHER SUBSTANCES OF WOOD-GUM.~

(p. 188) According to the text-books beech-wood may be regarded as the typical raw material for the preparation of the laboratory product known as wood-gum. The author has subjected beech-wood and beech-wood cellulose (Schulze process) to a range of hydrolytic treatments, acid and alkaline, in order to determine the conditions of selective action upon the mother substance of the wood-gum. In the main it appears that this group of furfuroids is equally resistant with the cellulose constituents of the wood; in fact, that the mother substance of wood-gum is a modified cellulose, and exists in the wood in chemical combination with the 'incrusting substances.'

Of the author's experimental results the following may be cited as typical:

Yield of furfural Substance p.ct. Original beech-wood 13.8

After boiling 3 hrs. with 1.25 p.ct. H_{2}SO_{4} (residue) 10.1

" " " " 5.0 " " " 5.6

Cellulose--isolated by Schulze process (yield 53 p.ct.) 6.9

" after further 14 days' digestion with the Schulze acid (HNO_{3} + KClO_{3}) 5.9

" after extraction with 5 p.ct. NaOH in cold (residue) 5.0

" after second extraction with 5 p.ct. NaOH in cold (residue) 4.4

UEBER DIE FRAGE NACH DEM URSPRUNG UNGESÄTTIGER VERBINDUNGEN IN DER PFLANZE.

C. F. CROSS, E. J. BEVAN, and C. SMITH (Berl. Ber., 1895, 1940).

~ON THE SOURCE OF THE UNSATURATED COMPOUNDS OF THE PLANT.~

(p. 179) In distilling for furfural by the usual methods of boiling cellulosic products with condensing acids, the furfural is accompanied by volatile acids, also products of decomposition of the cellulosic complex. A series of distillations was carried out with dilute sulphuric acids of varying concentration from 10-50 H_{2}SO_{4} : 90-50 H_{2}O by weight, using barley straw as a typical cellulosic material. The distillates were collected in successive fractions, and the furfural and volatile acid determined. The results are given in the form of curves. The aggregate yields were as follows:--

Concentration of acid (H_{2}SO_{4}) p.ct. 10 15 20 30 40 50