Researches on Cellulose Part 19

The tendency in the hexoses and their polyanhydrides to split off one carbon atom in the oxidised form, throws some light on the furfurane type of condensation, which is represented in the lignocelluloses. We are still without any evidence as to the possible transition of the hexoses to benzenoid compounds. Such transitions would be more easily explained on the a.s.sumption that the celluloses are composed in part of polyanhydrides of the ketoses.

SPIRITUS AUS CELLULOSE UND HOLZ.

E. SIMONSEN (Ztschr. angew. Chem., 1898, 3).

~PRODUCTION OF ALCOHOL FROM CELLULOSE AND WOOD.~

(pp. 50, 209) This investigation was undertaken with one main object--to determine the optimum conditions of treatment of wood-cellulose and of wood itself for conversion into 'fermentable sugar.' The process of 'inversion' or hydrolysis, by digestion with dilute acid at high temperature, involves the four main factors: pressure (i.e.

temperature), concentration of acid, ratio of liquid to cellulose and duration of digestion. Each of these was varied in definite gradations, and the effect measured. The degree of action was measured in terms of 'reducing sugar,' calculated from the results of estimation by Fehling solution, as 'glucose' per cent. of original cellulose (or wood).

(a) _Cellulose._ [Wood-cellulose obtained by bisulphite process.]--With a proportion of total liquid to cellulose of 27 : 1, and using sulphuric acid as the hydrolysing agent, the optimum results were obtained with acids of 0.45-0.60 p.ct. (H_{2}SO_{4}) and pressures of 6-8 atm. The maximum yield of 'sugar' was 45 p.ct. of the cellulose.

Under the above conditions the maximum of conversion is attained in 2 hours.

Having now regard to the production of a solution of maximum _concentration_ of dissolved solids, the following conditions were asertained to fulfil the requirement, and, in fact, may be regarded as the economic optimum:

Proportion of total liquid 6 times wt. of cellulose Concentration of acid 0.5 p.ct. H_{2}SO_{4} Pressure 10 atm.

Duration of digestion 1.5 hour

giving a yield of 41 p.ct. 'reducing sugar' calculated to the original cellulose (dry).

_Alcoholic Fermentation of Neutralised Extract._--The liquors were found to ferment freely, and on distillation to yield a quant.i.ty of alcohol equal to 70 p.ct. of the theoretical--i.e. on the basis of the numbers for copper oxide reduction.

(b) _Hydrolytic 'Conversion' of Wood (Lignocellulose)._--A similarly systematic investigation carried out upon pine sawdust established the following as optimum conditions:

Proportion of total liquid 5 times wt. of wood Concentration of acid 0.5 p.ct. H_{2}SO_{4} Pressure 9 atm.

Duration of digestion 15 minutes

giving a yield of 20 p.ct. 'reducing sugar,' calculated from the 'Fehling' test.

_Fermentation_ of the neutralised extracts gave variable results. The highest yields obtained were 60 p.ct. of theoretical, the author finally concluding that under properly controlled conditions of inversion and fermentation 100 kg. wood yield 6.5 l. absolute alcohol.

uBER DIE URSACHE DER VON SIMONSEN BEOBACHTETEN UNVOLLSTaNDIGKEIT DER VERGaHRUNG DER AUS HOLZ BEREITETEN ZUCKERFLuSSIGKEITEN.

B. TOLLENS (Ztschr. angew. Chem., 1898, 15).

~ON THE CAUSE OF INCOMPLETE FERMENTATION OF SUGARS OBTAINED BY ACID HYDROLYSIS OF WOOD.~

The author criticises Simonsen's explanation of the results obtained with extracts from pine wood. The incompleteness of fermentation of the products is certainly due in part to the presence of furfural-yielding carbohydrates, which are resistant to yeast. The pine woods contain 8-10 p.ct. of these const.i.tuents in their anhydride form ('pentosanes'). They yield readily to acid hydrolysis, and certainly const.i.tute a considerable percentage of the dissolved products. A similar complex was obtained by the author in his investigation of peat (Berl. Ber. 30, 2571), and was found to be similarly incompletely attacked by yeast. The yields of alcohol corresponded with the proportion of the total carbohydrates disappearing. These were the hexose const.i.tuents of the hydrolysed complex, the pentoses (or 'furfuroids') surviving intact.

UEBER SULFITCELLULOSEABLAUGE.

H. SEIDEL (Ztschr. angew. Chem., 1900).

~WASTE LIQUORS FROM BISULPHITE PROCESS.~

(p. 210) Later researches confirm the conclusion that in the soluble by-products of these cellulose processes the S is combined as a SO_{3}H group. The following a.n.a.lyses of the isolated lignin sulphonic acid are cited:

________________________________________________ C H S __________________________ _______ ______ ______ (a) Lindsey and Tollens 56.12 5.30 5.65 (b) Seidel (1) 56.27 5.87 5.52 (c) Seidel and Hanak (2) 53.69 5.22 8.80 (d) Street 50.22 5.64 7.67 __________________________ _______ ______ ______

The variations are due to the varying conditions of the digestion of the wood and to corresponding degrees of sulphonation of the original lignone group. Calculating the composition of the latter from the above numbers on the a.s.sumption that the S represents SO_{3}H, the following figures result:

__________________________________ (a) and (b) (c) (d) ___ _____________ _______ _______ C 64.00 65.1 59.61 H 6.65 6.33 6.69 ___ _____________ _______ _______

This author considers that beyond the empirical facts established by the above named[10] very little is yet known in regard to the const.i.tution of the lignone complex.

Nor is there any satisfactory application of this by-product as yet evolved. Evaporation and combustion involve large losses of sulphur [D.R.P. 74,030, 83,438; Seidel and Hanak, Mitt. Techn. Gew. Mus. 1898].

A more complete regeneration of the sulphur has been the subject of a series of patents [D.R.P. 40,308, 69,892, 71,942, 78,306, 81,338], but the processes are inefficient through neglect of the actual state of combination of the S, viz. as an organic sulphonate. The process of V.B.

Drewson (D.R.P. 67,889) consists in heating with lime under pressure, yielding calcium monosulphite (with sulphate and the lignone complex in insoluble form). The sulphite is redissolved as bisulphite by treatment with sulphurous acid. This process is relatively costly, and yields necessarily an impure lye. It has been proposed to employ the product as a foodstuff both in its original form and in the form of benzoate (D.R.P. 97,935); but its unsuitability is obvious from its composition.

A method of destructive distillation has been patented (D.R.P. 45,951).

The author has investigated the process, and finds that the yield of useful products is much too low for its economical development. Fusion with alkaline hydrates for the production of oxalic acid (D.R.P. 52,491) is also excluded by the low yield of the product.

The application of the liquor for tanning purposes (D.R.P. 72,161) appears promising from the fact that 28 p.ct. of the dry residue is removed by digestion with hide powder. This application has been extensively investigated, but without practical success. Various probable uses are suggested by the viscosity of the evaporated extract.

As a subst.i.tute for glue in joinery work, bookbinding, &c., it has proved of little value. It is applied to some extent as a binding material in the manufacture of briquettes, also as a subst.i.tute for gelatin in the petroleum industry. Cross and Bevan (E.P. 1548/1883) and Mitscherlich (D.R.P. 93,944 and 93,945) precipitate a compound of the lignone complex and gelatin by adding a solution of the latter to the liquors. The compound is redissolved in weak alkaline solutions and employed in this form for engine-sizing papers. Ekman has patented a process (D.R.P. 81,643) for 'salting out' the lignone sulphonates, the product being resoluble in water and the solution having some of the properties of a solution of dextrin. Owing to its active chemical properties this product--'dextron'--has a limited capability of subst.i.tuting dextrin. The suggestion to employ the evaporated extract as a reducing agent in indigo dyeing and printing has also proved unfruitful. The author's application of the soda salt of the lignone sulphonic acid as a reducing agent in chrome-mordanting wool and woollen goods (D.R.P. 99,682) is more successful in practice, and its industrial development shows satisfactory progress. The product is known as 'lignorosin.'

FOOTNOTES:

[10] See more particularly: Lindsey and Tollens, _Annalen_, 267, 341; Cross and Bevan's _Cellulose_, pp. 197-203; Street, Inaug.-Diss., Gottingen, 1892; Klason, _Rep. d. Chem. Ztg._ 1897, 261; Seidel and Hanak, _Mitt. d. Techn. Gew. Mus._ 1897-1898.

SECTION VII. PECTIC GROUP

UNTERSUCHUNGEN uBER PECTINSTOFFE.

R. W. TROMP DE HAAS and B. TOLLENS (Lieb. Ann., 286, 278).

uBER DIE CONSt.i.tUTION DER PECTINSTOFFE, B. TOLLENS (ibid. 292).

~INVESTIGATIONS OF PECTINS.~

(p. 216) It is generally held that the pectins are, or contain, oxidised derivatives of the carbohydrates. The authors have isolated and a.n.a.lysed a series of these products, and the results fail to confirm a high ratio O : H. The following are the a.n.a.lytical numbers:

________________________________________________ Pectin from Ash C H Ratio H : O ______________ ______ ______ _____ _____________ Apple 6.2 43.4 6.4 1 : 7.9 Cherry 20.5 42.5 6.5 1 : 7.9 Rhubarb 4.2 43.3 6.8 1 : 7.4 Currant 5.0 47.1 5.9 1 : 8.5 Greengage 3.3 43.0 5.9 1 : 8.5 Turnip 7.3 41.0 5.9 1 : 9.0 ______________ ______ ______ _____ _____________

Acid hydrolysis (4 p.ct. H_{2}SO_{4}) gave syrupy products not crystallisable--in certain cases the hydrolysis was accompanied by separation of insoluble cellulose. The insoluble product from currant pectin had the composition C 54.4, H 5.0.

Tollens points out that the results of empirical a.n.a.lysis are inconclusive; and that from the acid reactions of these products and their combination with bases, carboxylic groups are present, though probably in anhydride or ester form.

The pectins may be regarded as closely related to the mucilages (_Pflanzenschleim_), differing from them only by the presence of the oxidised groups in question.

UEBER DIE CONSt.i.tUTION DER PECTINSTOFFE.