Section Vii. Pectic Group

UNTERSUCHUNGEN UeBER PECTINSTOFFE.

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

UeBER DIE CONSTITUTION 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 analysed a series of these products, and the results fail to confirm a high ratio O : H. The following are the analytical 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 analysis 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 CONSTITUTION DER PECTINSTOFFE.

C. F. CROSS (Berl. Ber., 1895, 2609).

~CONSTITUTION OF PECTINS.~

It is pointed out that the composition of the pectin of white currants, as given in the preceding paper, is that of the typical lignocellulose, the jute fibre. The product was isolated and further investigated by the author. It gave 9.8 p.ct. furfural on boiling with HCl (1.06 s.g.), reacted freely with chlorine, giving quinone chlorides, and with ferric ferricyanide to form Prussian blue. This 'pectin' is therefore a form of soluble lignocellulose. The 'pectic' group consequently must be extended to include hydrated and soluble forms of the mixed complex of condensed and unsaturated groups with normal carbohydrates, such as constitute the fibrous lignocelluloses.

UEBER DAS PFLANZLICHE AMYLOID.

E. WINTERSTEIN (Ztschr. Physiol. Chem., 1892, 353).

~ON VEGETABLE AMYLOID.~

(p. 224) A group of constituents of many seeds, distinguished by giving slimy or ropy 'solutions' under the action of boiling water are designated 'amyloid.' They are reserve materials, and in this, as in the physical properties of their 'solutions,' they are very similar to starch. They are, however, not affected by diastase; and generally are more resistant to hydrolysis. Typical amyloids have been isolated by the author from seeds of Tropoeolum majus, Poeonia officinalis, and Impatiens Balsamina. The raw material was carefully purified by exhaustive treatment with ether and alcohol, &c.; the amyloid then extracted by boiling with water, and isolated by precipitation with alcohol. Elementary analysis gave the numbers C 43.2, H 6.1. On boiling with 12 p.ct. HCl it gave 15.3 p.ct. furfural; oxidised with nitric acid it yielded 10.4 p.ct. mucic acid. Specimens from the two first-named raw materials gave almost identical numbers.

Hydrolysis.--On boiling with dilute acids these products are gradually broken down, dissolving without residue. In this respect they are differentiated from the mucilages, which give a residue of cellulose (insoluble). From the solution the author isolated crystalline galactose, but failed to isolate a pentose. Dextrose was also not identified directly.

The tissue residues left after extracting the amyloid constituent, as above described, were subjected to acid hydrolysis. A complex of products was obtained, from which galactose was isolated. A furfural-yielding carbohydrate was also present in some quantity, but could not be isolated. The original seed tissues, therefore, contain an amyloid and a hemicellulose, the latter differentiated in its resistance to water. Both yield, however, to acid hydrolysis a complex of products of similar composition and constitution.

UEBER DEN GEHALT DES TORFES AN PENTOSANEN ODER FURFUROLGEBENDEN STOFFEN UND AN ANDEREN KOHLENHYDRATEN.

H. V. FEILITZEN and B. TOLLENS (Berl. Ber., 1897, 2,571).

~CARBOHYDRATE CONSTITUENTS OF PEAT.~

(p. 240) An investigation of typical peats taken at successive depths showed increasing percentage of carbon, and inversely a decreasing yield of furfural. The numbers may be compared with those for Sphagnum cuspidatum--with C = 49.80 p.ct., and furfural 7.99 p.ct., calculated to dry, ash-free substance:

_________________________________________________ | | | | | Depth at which taken | C p.ct. | Furfural p.ct. | |_____________________|_______|______________| | | | | | | 20-100 cm. | 51.08 | 6.93 | | I. | 100-200 " | 53.52 | 5.30 | | | 200-300 " | 58.66 | 3.19 | | | | | | | Surface-20 " | 55.47 | 3.40 | | II. | 20-60 " | 55.06 | 3.48 | | | 60-100 " | 58.25 | 1.45 | | | 100-120 " | 58.23 | 1.19 | | | 180-200 " | 57.57 | 1.80 | |_____________________|_______|_______________|

Cellulose was estimated by the Lange method. The yield from Sphagnum was 21.1 p.ct.

From specimen I. at { 20-100 cm. 15.20 { 100-200 " 6.87

From the peat of lower depths no cellulose could be obtained.

Hydrolysis (acid).--On heating with 1 p.ct. H{2}SO{4} at 130-135 deg., soluble carbohydrates were obtained, amongst which mannose was identified, and galactose shown to be present in some quantity. After fermenting away the hexoses, the residue was treated with phenylhydrazine and an osazone separated. It contained 17.3 p.ct. N, but melted at 130 deg.. The substance could not be identified as an osazone of any of the yet known pentoses.