Thuya occidentalis(CHAPTER VII. Flavonol Group.)

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.

Thuya occidenlalis (Linn.). In 1858 Rochleder and Kawalier (Wien. akad. Ber., 29, 10) isolated from the green portions of the Thuya (Thuja) occidentalis a glucoside Thujin, which, when hydrolysed, gave a yellow colouring matter thujetin.

Thujin, C₂₀H₂₂O₁₂. The plant was extracted with alcohol, the extract when cold filtered from wax, and evaporated to a small bulk. The residue was diluted with water, a few drops of lead acetate solution added, the precipitated impurities removed, and the clear brown filtrate treated with lead acetate. The yellow lead compound was collected, extracted with dilute acetic acid, and basic lead acetate now added to the solution. The bright yellow precipitate was suspended in water, decomposed with sulphuretted hydrogen, the lead sulphide removed, the filtrate treated with carbon dioxide in order to free it from sulphuretted hydrogen and evaporated in vacua over sulphuric acid. Crystals gradually separated, and these were crystallised repeatedly from dilute alcohol until when treated with ammonia a green coloration was no longer produced.

Thujin is described by these authors as citron yellow microscopic prisms sparingly soluble in cold water. The alcoholic solution becomes yellow on treatment with alkalis, whereas with ferric chloride a dark green coloration is produced. When thujin is digested in alcoholic solution with dilute hydrochloric or sulphuric acid it is hydrolysed with formation of glucose and thujigenin, apparently an intermediate product, which readily takes up a molecule of water, with formation of thujetin
C₂₀H₂₂O₁₂ + H₂O = C₁₄H₁₂O₇(Thujigenin.) + C₆H₁₂O₆
C₁₄H₁₂O₇ (Thujigenin.) + H₂O = C₁₄H₁₄O₈ (Thujetin.)

Thujetin, C₁₄H₁₄O₈, forms yellow crystals, and is characterised by the fact that its alcoholic solution is coloured blue-green with ammonia, and green coloured by potassium hydroxide solution.

With lead acetate it gives a deep red precipitate. When thujetin is digested with boiling baryta water it is converted into thujetinic acid, C₂₈H₂₂O₁₃, which consists of yellow microscopic needles, sparingly soluble in water, readily soluble in alcohol.

Thujigenin, C₁₄H₁₂O₇, crystallises in fine yellow needles, soluble in alcoholic ammonia, with a blue-green coloration.

The quantity of thujin which is present in the plant is very small; thus, from 240 lbs. Rochleder and Kawalier were successful in isolating a few grams only.

Perkin (Chem. Soc. Trans., 1914, 105, 1408), who re-examined this subject and employed methods almost identical with those of Rochleder and Kawalier, found that the glucoside corresponding to thujin possessed the formula C₂₁H₂₀O₁₁, melted at 183-185°, and when hydrolysed gave rhamnose and quercetin and was identical with the quercitrln of quercitron bark. The plant also contained a small amount of quercetin, and this also, prepared by the hydrolysis of the glucoside which evidently corresponds to the thujetin of Rochleder and Kawalier, dissolved in alkaline solutions with a pale green tint, but failed to give the blue-green coloration with ammonia described by these authors. During a preliminary investigation of this plant (Chem. Soc. Trans., 1899, 75, 829), the sample then examined gave a trace of yellow colouring matter soluble in alkalis with a strong green coloration, the acetyl compound of which after frequent recrystallisation melted at 205-206°. It thus seems probable that the thujin of Rochleder and Kawalier consisted of quercitrin contaminated with a second glucoside, possibly that of myricetin. The quantity of this latter present in the plant may possibly vary according to its environment or with the season of the year.

Other sources of Quercetin.(CHAPTER VII. Flavonol Group.)

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.

See ONION SKINS, PERSIAN BERRIES, SOPHORA JAPONICA, PODOPHYLLUM EMODI, WHITE CLOVER (Trifolium repens), CUTCH (Acacia catechu and Uncaria gambier), and SUMACH, Osyris compressa, Osyris abysinnica, Ailanthus glandulosa, Rhus rhodanthema, Artostaphylos uva ursi. Quercetin has also been shown to exist probably as glucoside in tea leaves (Hlasiwetz and Malin, Jahres., 1867, 732);
in the flowers of the horse-chestnut (Rochleder, ibid., 1859, 523);
in the bark of the apple-tree (Rochleder, ibid., 1867, 731);
in Craetagus oxycantha (may blossom); and yellow wallflowers, Cheiranthus chieri (Perkin and Hummel, Chem. Soc. Trans., 1896, 69, 1568);
Rumex obtusifolius (seeds), (Perkin, ibid., 1897, 71, 1199);
Delphinium zalil (Asbarg), (Perkin and Pilgrin, ibid., 1898, 73, 381);
Prunus spinosa (flowers), (Perkin and Phipps, ibid., 1904, 85, 56),
Thespasia lampas (Perkin, ibid., 1909, 95, 1859),
the flowers of the Poinciana regia (Bengal), Woodfordia floribunda, and the common fuschia, F. macrostema globosa (Perkin and Shulman, Chem. Soc. Proc., 1914, 30, 177).

Quercitron Bark.Glucosides of Quercetin.Rutin.(CHAPTER VII. Flavonol Group.)

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.

Rutin was discovered by Weiss (Chem. Zentr., 1842, 305) in the leaves of a rue (Ruta graveolens, Linn.), and was subsequently isolated from capers (Capparis spinosa, Linn.) by Rochleder and Hlasiwetz (Ann. Chem. Pharm., 82, 196), and by Schunck (Manchester Memoirs, 1858, 2 Ser., 155, 122) from buckwheat (Fagopyrum esculentum, Moench.). Whereas Hlasiwetz (Ann. Chem. Pharm., 96, 123) came to the conclusion that rutin was identical with quercitrin, it was shown by Zwenger and Dronke (ibid, 123, 145) that this could not be the case, because on hydrolysis rutin gives quercetin and two molecules of sugar. Schunck (Chem. Soc. Trans., 1888, 53, 262; 67, 30) considered that the formula of rutin is C₂₇H₃₂O₁₆, 2H₂O, and that on hydrolysis it is converted into quercetin and 2 molecules of rhamnose, C₂₇H₃₂O₁₆+3H₂O=C₁₅H₁₀O₇+2C₆H₁₄O₆. Rutin, moreover, was identical with the sophorin, which Foerster (Ber., 15, 214) had isolated from the Sophora japonica.

It has been shown by Schmidt (Chem. Zentr., 1901, ii., 121) that by the hydrolysis of rutin glucose is also produced, the formula of this substance being therefore C₂₇H₃₀O₁₆.C₂₇H₃₀O₁₆ + 3H₂O = C₁₅H₁₀O₇ + C₆H₁₂O₆ + C₆H₁₄O₆

Rutin forms pale yellow glistening needles, sparingly soluble in water, and is said to melt above 190°. With alcoholic potassium acetate it gives a bright yellow monopotassium salt (Perkin, Chem. Soc. Trans., 1899, 75, 440).

According to Schmidt, violaquercitrin (violarutin) is identical with rutin (ibid.) 1908, 246, 274), and Perkin (ibid., 1910, 97, 1776) has shown that osyritin (Colpoon compressum, Berg.) (Osyris compressa) (ibid., 1902, 81, 477) and myrticolorin {Eucalyptus macrorhyncha, F. Muell.) (Smith, ibid., 1898, 73, 697) in reality consist of this substance (loc. cit.).

The dyeing properties of rutin are similar to, though weaker than those of quercitron bark. The following shades are given on mordanted woollen cloth:
Chromium. Brown-yellow.
Aluminium. Full golden-yellow.
Tin. Lemon-yellow.
Iron. Dull brown.

Quercitron BarkCommercial preparations: Flavin, Patent bark, Bark-liquor.(CHAPTER VII. Flavonol Group.)

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.

Quercitron Bark
Commercial Preparations.

Flavin.

This is the most important commercial preparation of quercitron bark; it seems to have been first imported into this country from America. The details of its manufacture have been guarded with much secrecy, and analyses of commercial samples show that different methods have been adopted by different makers. Some specimens consist essentially of quercitrin, and are known as yellow flavin, whilst others contain only quercetin, and are known as red flavin. The former have probably been prepared by merely extracting the bark with water and high-pressure steam, or, as it is said, with steam only at a temperature of 102-103°.

The best qualities of flavin are those in which the colouring matter is present as more or less pure quercitrin, and entirely free from woody fibre. Red flavin is prepared by rapidly extracting the powdery portion of rasped quercitron bark with ammonia or other alkali, and boiling the solution with sulphuric acid. The precipitate thus produced is ultimately collected, washed with cold water till free from acid, and finally dried. Flavin of this character has about sixteen times the tinctorial value of quercitron bark. It is not very soluble, but it yields with aluminium, and especially with tin mordants, much more brilliant colours than quercitron bark itself.

Patent bark.

Patent bark, or "commercial quercetin," is a preparation of quercitron bark analogous to the garancin made from madder. It is manufactured in a similar manner, viz. by boiling, for about two hours, 100 parts finely ground quercitron bark, 300 parts water, and 15 parts concentrated sulphuric acid. The product is collected on a filter, washed free from acid, and dried. The yield is about 85 per cent, of the bark employed, while its colouring power is much greater. It seems to have been first manufactured in 1855 by Leeshing.

Bark-liquor.

Bark-liquor is simply an aqueous extract of quercitron bark, and is sold with a specific gravity of 1.66-1.255.

Application.

Quercitron bark, patent bark, and bark extracts have been largely employed by the calico and woollen printer. The latter are used in the preparation of steam-yellows, olives, chocolates, etc., in conjunction with aluminium, tin, chromium, and iron mordants. The former at one time found employment in conjunction with garancin for the production of various compound shades, e.g. chocolate, dull red, orange, etc. Now they may be used in a similar manner along with alizarin. When used alone, quercitron bark and patent bark give, with aluminium mordant yellow, with tin orange, with chromium olive-yellow, with iron greenish-olive colours.

Flavin is chiefly serviceable in wool dyeing for the production, in single-bath, of bright yellow and orange, fast to milling, and was at one time largely used along with cochineal to obtain a bright scarlet. The mordant employed is stannous chloride and oxalic acid or cream of tartar.

On cotton all the quercitron colours are but moderately fast to light; on wool and silk the chromium, copper, and iron colours are fairly fast, whereas the aluminium and tin colours are only moderately so.

Quercitron Bark(CHAPTER VII. Flavonol Group.)(Osa artikkelista)

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.

This important yellow dyestuff, the latest addition to the somewhat meagre list of commercial natural colouring matters, was discovered and introduced by Bancroft in 1775. In his "Philosophy of Permanent Colours" he states (ii., 113): "Quercitron bark is one of the objects of a discovery of which the use and application for dyeing are exclusively vested in me, for a term of years by an Act of Parliament in the twenty-fifth year of his present Majesty's reign".

Quercitron bark is the inner bark of a species of oak known as Quercus discolor; Ait (Q. tinctoria), which is a native of the Middle and Southern States of America. The tree in the south is described as being from 60 to 80 feet high, with a trunk from 6 to 10 feet in diameter; but in the north it does not attain to this size. In order to obtain the dyestuff the epidermis or exterior blackish coat of bark is usually removed by shaving and the inner portion then detached and ground. The product may be separated into stringy fibres and a light fine powder, the latter of which contains the principal portion of the colouring matter.

Quercitron bark and its preparations are still used to a considerable extent, although not so much as was formerly the case. This is not only due to the introduction of the artificial colouring matters, but because it has been supplanted for many purposes by the less costly old fustic.

Quercetin, C₁₅H₁₀O₇;, the colouring matter of quercitron bark, has been the subject of numerous researches, and many of these unfortunately resulted in the publication of complicated and unsatisfactory formulæ. At an early stage it was ascertained that quercetin does not exist in the plant, at least to any extent in the free condition, but in the form of its glucoside quercitrin.

To prepare quercetin the following method devised by the late Sir W. H. Perkin, and employed by him for several years on the manufacturing scale, gives good resets. Quercitron bark dust is macerated with moderately strong salt solution to remove gummy substances, filtered, and then extracted with dilute ammonia. The cold ammoniacal liquid is treated with a slight excess of hydrochloric acid, causing the separation of certain impurities in the form of a brown flocculent precipitate. This is removed, and the pale yellow acid solution of the glucoside is boiled for about thirty minutes. The glucoside is thus hydrolysed and almost chemically pure quercetin separates in the form of pale yellow needles, which are collected while the mixture is still warm and washed with water. It is readily soluble in alcohol, and dissolves in alkaline solutions with a yellow colour. With aqueous lead acetate it gives a bright orange- red precipitate, and with alcoholic ferric chloride a dark green colour.

The most important of the early investigations of quercetin was carried out by Liebermann and Hamburger (Ber., 12, 1178), who assigned to it the formula C₂₄H₁₆O₁₁ and to quercitrin the formula C_26H38O₂₀ Herzig (Monatsh., 5, 72; 6, 863; 9, 537; 12, 172; 14, 53; 15, 697), who made an elaborate series of researches on this subject, at first adopted this formula. Subsequently it was ascertained that quercetin was in reality C₁₅H₁₀O₇, and this receivedsupport by the examination of its compounds with mineral acids (Perkin and Pate, Chem. Soc. Trans., 1895, 67, 647).

When quercetin is fused with alkali, it gives protocatechuic add and _{phloroglucinol}, and if its alkaline solution is oxidised with air, the same products are obtained. By the more gentle action of the alkali, Hlasiwetz and Pfaundler (Jahres., 1864, 561) obtained certain intermediate products of the hydrolysis, paradiscetin, C₁₅H₁₀O₆, yellow needles, quercetic acid, C₁₅H₁₀O₇, colourless needles, and quercimeric acid, C₈H₆O₅, H₂O, colourless crystals. Herzig and others who have reinvestigated this decomposition have been unable to obtain the substances of Hlasiwetz and Pfaundler, and if these compounds are in reality chemical individuals, it seems likely that their formation was due to the action of some special impurity contained in the alkali employed by these chemists.

[---]

Quercetin is a strong dyestuff, and gives with mordanted wool the following shades, which are almost identical with those produced by fisetin:
Chromium. Red-brown.
Aluminium. Brown-orange.
Tin. Bright orange.
Iron. Olive-black.

[---]

Quercitrin, the glucoside of quercetin, was first isolated from quercitron bark by Chevreul, and has been examined by numerous chemists. The method usually employed for the preparation of this substance is that devised by Zwenger and Dronke (Annalen, Suppl., 1, 267), and this was subsequently utilised by Liebermann and Hamburger (Ber., 12, 1179).

Quercitron bark is extracted with 5-6 times its weight of boiling 50 per cent, alcohol, the extract evaporated to one-half, and treated with a little acetic acid, followed by lead acetate solution. The precipitate is removed, sulphuretted hydrogen is passed through the filtrate, and after removal of lead sulphide the clear liquid is evaporated to dryness. The residue is dissolved in a little hot alcohol, the solution treated with water and the crude quercitrin which separates on cooling is purified by repeated crystallisation from water.

A very convenient source of quercitrin is yellow flavine (Perkin, private communication), which consists almost entirely of this substance, and is usually free from quercetin. A hot aqueous extract of this material gives, on cooling, a crystalline precipitate of the glucoside, and this by recrystallisation from water with the aid of animal charcoal is readily obtained pure.

[---]

It was formerly considered that the glucosides (colouring principles) were hydrolysed during the dyeing operation, and that the shades thus obtained were due not to the glucosides, but to the free colouring matters. This in certain cases is correct, especially when the plant contains an enzyme capable of effecting the hydrolysis; but on the other hand, in many cases the glucoside is itself the colouring matter and directly responsible for the dyeing effect. Quercitrin is an instance in point (Perkin, Chem. Soc. Trans., 1902, 81, 479), and gives upon mordanted fabrics shades which are distinct from those of quercetin itself.

Quercitrin.
Chromium - Full brown-yellow.
Aluminium - Full golden-yellow.
Tin - Lemon-yellow.
Iron - Deep olive.

Quercetin.
Chromium - Red-brown.
Aluminium - Brown-orange.
Tin - Bright orange..
Iron - Olive black.

Kaempferol.
Chromium - Brown-yellow.
Aluminium - Yellow.
Tin - Lemon-yellow..
Iron - Deep olive-brown.

In dyeing property quercitrin very closely resembles kaempferol, and, indeed, differs but little from morin (old fustic) and luteolin (weld) in this respect. It was thus probable, according to Perkin (loc. cit.), that the constitution of the glucoside is to be represented by one of the two following formulæ: [KUVA PUTTUU]

[---]

The colours given by quercitrin are somewhat faster than those derived from quercetin.

Yellow Cedar(CHAPTER VII. Flavonol Group.)

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.

The Rhodosphacra rhodanthema (Engl.) or yellow cedar, a tree growing to the height of 70 or 80 feet, is indigenous to the northern part of New South Wales.

The colouring matter of this dyewood is fisetin, which is readily isolated by the method described in connection with young fustic (Perkin, Chem. Soc. Trans., 1897, 71, 1194).

A second substance, C₃₆H₃₀O₁₆?, colourless needles, melting-point 215-217°, is also present in small amount, and may be identical with fustin, the glucoside of fisetin obtained from young fustic by Schmid (Ber., 1886, 19, 1755).

The shades given by the yellow cedar are slightly weaker and differ considerably from those given by young fustic (Rhus cotinus), although both contain the same colouring matter. Employing mordanted woollen cloth, the following distinctions are observed:
Young fustic - Chromium. Reddish-brown; Aluminium. Orange; Tin Orange-yellow; Iron. Brown-olive
Yellow cedar - Chromium Yellowish-brown; Aluminium. Brownish-yellow; Tin Golden-yellow; Iron Olive
and these may be due to varying amounts of the glucoside which is contained in both plants.

Young Fustic(CHAPTER VII. Flavonol Group.)

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.

Cotinus coggygria

Young fustic consists of the wood of the stem and larger branches of the Rhus cotinus (Linn.), a small tree which is a native of Southern Europe, and the West India Islands. It is a hard compact yellow wood, and is usually imported in small bundles or faggots. Within the last few years young fustic has almost disappeared from the market, not only on account of the artificial colouring matters, but because the shades it yields lack permanence, and the percentage of colouring matter it contains is small. The leaves of the R. cotinus constitute Venetian sumach, a tanning material which is employed to some extent in Italy and Southern Europe.

Fisetin, C₁₅H₁₀O₆, the colouring matter of young fustic, was first isolated by Chevreul ("Leçons de Chimie appliquee a la Teinture," A. ii., 150), who gave it the name "Fustin". Bolley (Schweiz. polyt. Zeitschr., 1864, 9, 22) considered that it was identical with quercetin, but Koch (Ber., 5, 285) maintained that fisetin was probably an aldehyde of quercetinic acid.

Schmid (Ber., 1886, 19, 1734), who carried out an exhaustive examination of this dyewood, obtained fisetin in a pure condition and proved that it was not identical with quercetin. He found that in addition to the free colouring matter, young fustic contains a glucoside of fisetin combined with tannic acid to which he gave the name of fustin tannide.

To prepare fisetin, Schmid (loc. cit.), and later Herzig (Monatsh., 12, 178), employed "cotinin" (v. infra), a commercial preparation of young fustic which is no longer on the market. According to Perkin and Pate (Chem. Soc. Trans., 1895, 67, 648), fisetin is readily isolated from the dyewood as follows:

Young fustic is extracted with boiling water, and the extract treated with lead acetate solution. The lead compound of the colouring matter is collected, made into a thin paste with water, and in a fine stream run into boiling dilute sulphuric acid. After removal of lead sulphate the dark-coloured filtrate, on cooling, deposits a semicrystalline brownish mass, which is collected and purified by crystallisation from dilute alcohol.

[---]

Fisetin is a strong colouring matter and gives shades which are almost identical with those produced by quercetin, rhamnetin, and myricetin. The colours given with wool mordanted with chromium, aluminium, and tin are, respectively, red-brown, brown-orange, and bright red-orange (Perkin and Hummel, Chem. Soc. Trans., 1896, 69, 1290).

The glucoside of fisetin, according to Schmid (loc. cit.), is prepared as follows: A boiling aqueous extract of young fustic is treated with lead acetate, the precipitate removed, the clear liquid freed from lead by means of sulphuretted hydrogen, and saturated with salt. The mixture is filtered, the filtrate extracted with ethyl acetate, and the extract evaporated. There is thus obtained a residue consisting of the crude fustin-tannide, which is purified by solution in water, precipitation with salt, and extraction with ethyl acetate.

Fustin tannide crystallises in long yellowish- white needles, which are easily soluble in water, alcohol, and ether. When heated it decomposes above 200°. If a solution of fustin tannide in hot acetic acid is treated with water, and allowed to stand for some time, colourless crystals of fustin are gradually deposited.

Fustin crystallises from water in yellowish-white needles, melting-point 218-219°, and when digested with boiling dilute sulphuric acid gives fisetin and a sugar, the nature of which has not been determined. The formula given to this glucoside C₅₈H₄₆O₂₃ by Schmid cannot be regarded as correct, in view of the fact that the true formula of fisetin is now known to be C₁₅H₁₀O₆.

Dyeing Properties of Young Fustic.

The colours derived from young fustic are all fugitive to light, hence this dyestuff has lost its importance. In silk dyeing it was formerly used for dyeing brown, the silk being mordanted with alum, and afterwards dyed with a decoction of young fustic, peachwood, and logwood. With the various metallic salts as mordants young fustic yields colours somewhat similar to those obtained from old fustic, the chromium colour is, however, much redder, being a reddish-brown, and the aluminium yellow is much duller; stannous chloride on the contrary gives an incomparably more brilliant orange, not unlike that obtainable from flavin or from Persian berries (Hummel).

Fisetin is present also as glucoside in the wood of the yellow cedar, Rhodosphacra rhodanthema, and in the wood of the Quebracho Colorado (loc. cit.).

The leaves of the R. cotinus contain myricetin.

Robinia pseud-acacia, Flowers (CHAPTER VII. Flavonol Group.)

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.

Robinin was first isolated from the flowers of the white Azalea by Zwengerand Dronke (Annalen, Supp., 1861, 1, 263), who considered that it was a glucoside of quercetin. Perkin (Chem. Soc. Trans., 1902, 81, 473) has shown that this is not the case.

To prepare the glucoside the flowers are exhausted with boiling alcohol, the solution concentrated by evaporation and poured into water. The mixture is extracted with ether, and the aqueous liquid distilled down to a small bulk. On standing, crystals of robinin separate, which are purified by crystallisation from water.

Robinin, according to Perkin, consists of pale yellow needles, sintering at 190 and melting at 196-197°, and when air-dried it possesses the formula C₂₃H₄₂O₂₀, 8H₂O.

Boiling dilute sulphuric acid hydrolyses robinin with formation of kaempferol, 2 molecules of rhamnose and 1 of glucose, according to the following equation:
C₂₃H₄₂O₂₀ + 4H₂O = C₁₅H₁₀O₆ + 2C₆H₁₄O₆ + C₆H₁₂O₆

Schmidt (Chem. Zentr., 1901, ii., 121), who examined robinin at almost the same time, also obtained by its hydrolysis a colouring matter C₁₅H₁₀O₆, the acetyl compound of which melts at 182-183° (evidently kaempferol), and Waljascko (J. Russ. Phys. Chem. Soc., 1904, 36, 421), again, no doubt, also unaware of the communication of Perkin, terms this colouring matter C₁₅H₁₆O₆, H₂O, robigenin. Robinin he considered to possess the formula C₃₃H₄₀O₁₉.7½H₂O, and the sugars that it yields by hydrolysis to consist of galactose (1 mol.) and rhamnose (2 mols.).

Robinin is a most interesting glucoside, and with the exception of xanthorhamnin is the only known substance of this class which yields three sugar nuclei. It is practically devoid of tinctorial property.

Interesting is the fact that whereas the bark of this plant contains acacetin, the monomethyl ether of the trihydroxyflavone, apigenin, its flowers yield the glucoside of the trihydroxyflavonol kaempferol. Whether the occurrence of distinct flavones in various portions of the same plant is exceptional or otherwise, has been little studied, and appears to have only been observed elsewhere in the cases of the yellow cedar (Rhodesphaera rhodanthema), the leaves of which contain quercetin and the stem fisetin, and the Venetian sumach, the stem of which contains fisetin and the leaves myricetin.