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.