The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918
Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.
Persian berries are the seed-bearing fruit of various species of Rhamnus, growing wild or cultivated in France, Spain, Italy, the Levant, and Persia. The Persian berry proper is obtained from R. amygdalinus, R. oleoides, and R. saxatilis, and is imported from Smyrna and Aleppo. Its size is about that of a pea, colour yellowishgreen, surface much shrivelled, hard, and divisible along well-marked depressions forming a cross, into four parts, each containing a triangular seed; its taste is intensely bitter.
Avignon or French berries, the product of R. infectorius (Linn.) and R. alaternus (Linn.), are smaller in size than the foregoing and contain only two seeds.
Spanish, Italian, and Hungarian berries are respectively the products of R. saxatilis, R. infectorius (Linn.), and R. cathartica (Linn.). These are similar in quality to the Avignon berries. Other qualities come from the Morea, Wallachia, and Bessarabia.
All of these botanical varieties do not contain entirely the same constituents, but, on the other hand, there is every reason to suppose that the colouring constituents of those to which the term Persian berry proper is applied are identical in each case.
Gelatly (Edinburgh New Phil. Jour., 7, 252) was the first to isolate from Persian berries (R. tinctoria, Wald. et Kit.) the glucoside xanthorhamnin, C45H56O28, which on hydrolysis with acid gave a sugar and a colouring matter rhamnetin. Hlasiwetz (Annalen, 112, 107) considered that xanthorhamnin was identical with quercitrin, and rhamnetin with quercetin, but Schützenberger and Berteche (Bull. Soc. Ind. Mulhouse, 35, 456) denied this, and assigned to rhamnetin the formula C12H10O5. Xanthorhamnin, which Schützenberger (Jahres., 1868, 774) termed α-rhamnegin was considered to possess the formula C24H32O14. The presence of a second glucoside, β-rhamnegin, was also detected by this chemist, and from this by hydrolysis fi-rhamnetin was derived. Liebermann and Hörmann (Annalen, 196, 313) also investigated Persian berries, devised a method for the preparation of xanthorhamnin and rhamnetin, and prepared various derivatives of the latter.
It is now known that Persian berries contain the glucosides of three colouring matters, namely rhamnetin, rhamnazin, and quercetin (Herzig, Monatsh., 6, 889; 9, 549; 12, 175; Perkin and Geldard, Chem. Soc. Trans., 1895, 67, 500).
To isolate these substances Persian berries are extracted with boiling water, the solution treated with a small quantity of sulphuric acid, and digested while boiling for one hour. The glucosides are thus hydrolysed and the crude colouring matters separate in the form of a greenish-yellow precipitate.
The product is extracted with boiling alcohol, which dissolves principally the quercetin, this being the most soluble of the three colouring matters. The residue now contains rhamnetin and rhamnazin, and the latter is removed from the former by two or three extractions with boiling acetic acid.
Rhamnetin, C16H12O7, crystallises in yellow needles very sparingly soluble in acetic acid and alcohol. It dissolves in alkaline solutions with a pale yellow colour, and gives with alcoholic lead acetate an orange-red precipitate. When acetylated it forms tetra-acetylrhamnetin, C16H8O7(C2H3O)4 (Liebermann and Hörmann), colourless needles, melting-point 183-185°, and on bromination dibromrhamnetin is produced.
Rhamnetin sulphate, C16H12O7.H2SO4 (Perkin and Pate, Chem. Soc. Trans., 1895, 67, 650), orange-red needles, and monopotassium rhamnetin, C16H11O7K (Perkin and Wilson, ibid., 1903, 83, 136), orange-yellow needles, have been prepared.
Rhamnetin is in reality a quercetinmonomethyl ether (Herzig, loc. cit.}, for on digestion with hydriodic acid it is converted into quercetin, and when methylated with methyl iodide quercetintetramethyl ether is produced.
By the action of boiling potassium hydroxide solution, of boiling alcoholic potash, or by aspirating air through its alkaline solution, rhamnetin gives protocatechuic acid, and a syrupy phloroglucinol derivative. The latter, identified by means of its diazobenzene compound, consists of phloroglucinol monomethyl ether (Perkin and Allison, Chem. Soc. Trans., 1902, 81, 470), and consequently the constitution of rhamnetin is to be expressed as follows [KUVA PUUTTUU]
Rhamnetin is a strong dyestuff, and gives on mordanted woollen cloth shades which are practically identical with those produced by quercetin:
Chromium - Red-brown.
Aluminium - Brown-orange.
Tin - Bright Orange.
Iron - Deep olive.
(Perkin and Wilkinson, ibid., 1902, 81, 590).
Rhamnazin, C17H14O7 (P. and G.), yellow needles, melting-point 214-215°, is moderately soluble in boiling toluene, a property which distinguishes it from both rhamnetin and quercetin. It dissolves in alkaline liquids to form orange-yellow solutions, and with alcoholic ferric chloride gives an olive-green coloration.
Acetylrhamnazin, C17H11O7(C2H3O)3, colourless needles, benzoylrhamnazin, C17H11O7(C7H6O)3, colourless needles, melting-point 204-205°, and dibromrhamnazin, C17H12Br2O7, yellow needles, have been prepared.
Rhamnazin is a quercetin dimethyl ether. Digested with boiling hydriodic acid, it is converted into quercetin, and by methylation in the ordinary manner gives quercetin tetramethyl ether. Boiling alcoholic potash hydrolyses rhamnazin with formation of vanillic acid and phloroglucinol monomethyl ether (Perkin and Allison, loc. cit.). It accordingly possesses the constitution [KUVA PUUTTUU]
Rhamnazin does not readily dye mordanted calico, but on mordanted wool gives shades resembling those which are produced by kaempferol-
Chromium - Golden-yellow
Aluminium - Orange-yellow
Tin. - Lemon-Yellow.
Iron - Olive-brown.
Only a small amount of this colouring matter is present in Persian berries.
Xanthorhamnin, C23H42O20, is readily prepared by extracting powdered Persian berries with three times their weight of boiling 85 per cent, alcohol. On standing the dark brown filtered extract deposits a large quantity of the impure glucoside as a brown resinous mass. From the supernatant liquid on standing a purer xanthorhamnin separates in the form of a pale yellow cauliflower-like precipitate, and in such quantity as to congeal the whole liquid to a stiff paste. This is collected, repeatedly crystallised from alcohol, and finally from alcohol containing a little water and ether (Liebermann and Hörmann, loc. cit.}.
Xanthorhamnin consists of pale yellow needles readily soluble in water and hot alcohol, soluble in alkaline solutions with a yellow colour. With basic lead acetate it gives an orange precipitate. According to the work of Liebermann and Hörmann, xanthorhamnin, when hydrolysed with acid, gives rhamnetin and rhamnose, C8H66O29 + 5H2O = 4C6H14O6 + 2C12H10O5
More recently, however, Xanthorhamnin has been shown to possess the formula C34H42O20, and that by means of its specific ferment rhamninase, contained by Persian berries, it is hydrolysed with formation of rhamnetin and a complex sugar rhamninose, C18H32O14, C24H42O26+H2O=C16H12O7+C18H32O14
When rhamninose is digested with boiling dilute acids, it is converted into 2 molecules of rhamnose, and 1 molecule of galactose (C. and G. Tanret, Comptes rend., 1899, 129, 725), C18H22O14+4H2O=C6H12O6+2C6H14O6
No glucosides of rhamnazin or quercetin have been isolated as yet from Persian berries.
The action of the ferment rhamninase is readily demonstrated. If crushed Persian berries, contained in a muslin bag, are suspended in water heated to 40°, a yellow solution containing the glucosides is produced; this quickly becomes opaque and a heavy precipitate of the mixed colouring matters eventually separates. To within recent years this reaction was carried out on a commercial scale, and the product was placed on the market under the name of "rhamnétine". This reaction can be employed to distinguish between the dyeing properties of the glucosides contained in the berries, and the free colouring matters produced by their hydrolysis. Thus if Persian berries be added to a cold dye-bath, and this is slowly heated to boiling, the glucosides are hydrolysed by the ferment; but if, on the other hand, the berries be at once plunged into boiling water, the ferment is killed and a solution of the glucosides is obtained. In the former case wool mordanted with tin gives an orangered shade, whereas in the latter a pure yellow colour is produced.
Beyond the ordinary extract of Persian berries which is prepared in large quantity by extracting the berries with boiling water, and evaporating the solution under reduced pressure, no special commercial preparations are manufactured at the present time.
Dyeing Properties.
In wool dyeing Persian berries are little employed on account of their cost; moreover, they possess no special advantage over quercitron bark and old fustic. Persian berries, as a rule, give redder shades than quercitron bark, a fact which is to be explained as due to the hydrolysis of its glucosides by the ferment. The quercitrin of quercitron bark is not accompanied by such a specific ferment, and consequently the shades given by this dyestuff are of a yellower character. With tin mordant Persian berries give bright yellows and oranges, which are only fairly fast to light; but according to Hummel, the yellowish-olive produced with copper mordant is extremely fast, and is darkened rather than otherwise by exposure. Persian berries are still used to a considerable extent in calico-printing for the formation of yellow, orange, and green shades.
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