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.
TURMERIC (Indian saffron; Terra merita). The so-called turmeric root of commerce is the underground stem or rhizome of Curcuma longa (Linn.), or of various species of Curcuma e.g. C. tinctoria, C. viridiflora (Roxb.), etc. These plants, belonging to the Scitamineæ, are indigenous to Southern Asia, and are there largely cultivated, being exported from China, Madras, Bengal, Java, Malabar, Batavia, and Barbadoes. Those varieties which are derived from the central rhizomes are more or less round (Curcuma rotunda, Linn.), while the lateral rhizomes are long and finger-shaped (C. longa]. When of good quality these commercial varieties are hard, and possess a dull, waxy, resinous fracture, the external colour being yellowishgrey, and internally orange-brown, but producing, when ground, a somewhat bright yellow powder, having a strong characteristic odour and a peppery bitter taste.
The rhizome of Canna speciosa, a West African plant, is said to be exactly similar to East Indian turmeric in taste, smell, and chemical reactions (Daniell, Pharm. J., 19, 258). It is cultivated in Sierra Leone, and furnishes the so-called "African turmeric".
According to Pelletier and Vogel (Annalen, 44, 297), turmeric contains cellulose, gum, starch, mineral matter, a strong-smelling volatile oil, a brown colouring matter, and a characteristic yellow colouring matter named by them Curcumin. Pectin and pectic acid are also present (Schützenberger). Kachler (Ber., 3, 713) found a notable quantity of potassium binoxalate.
Pelletier and Vogel's method of isolating the curcumin consisted in first removing the fatty, resinous, and other impurities by extracting pulverised turmeric with water and carbon disulphide, then dissolving out the colouring matter with boiling alcohol, and purifying it by successive solution in ether and alcohol, precipitation with lead acetate, and subsequent treatment with hydrogen sulphide and extraction of the product with ether. It was thus obtained as an amorphous yellow powder.
Lepage adopted a similar method, but after extraction with carbon disulphide the colouring matter was dissolved in alkali, precipitated with acid, and finally purified by means of ether.
Daube was the first to obtain curcumin in the crystalline state. He removed essential oil by passing a strong current of steam over the coarsely-ground turmeric, then thoroughly extracted it with hot water, and finally treated the dried residue with boiling benzene. On cooling the solution thus obtained, crude curcumin separated as bright orange-red crystalline crusts, which were pressed between blotting-paper, and dissolved in cold alcohol. After filtering off some yellow flocculent substance, the solution was precipitated with an alcoholic solution of neutral lead acetate, adding finally a little basic lead acetate in order to neutralise almost entirely the liberated acetic acid and prevent thereby any solution of the colour-lake. The brick-red precipitate was washed with alcohol, suspended in water, and decomposed with hydrogen sulphide. The liberated curcumin was extracted from the precipitate with boiling alcohol, from which it crystallised on slow evaporation.
Benzene is very suitable for the isolation of pure curcumin, for although it is very little soluble in this liquid, the resinous impurities are not dissolved thereby.
Gajewsky (Ber., 3, 265) obtained crystalline curcumin by first extracting turmeric root with carbon disulphide, then dissolving out the colouring matter with ether, and purifying it by fractional crystallisation from ether or benzene. He detected the presence of another colouring matter and also traces of an alkaloid. This chemist obtained an increased yield of colouring matter by washing the dry ethereal extract with dilute ammonia to remove resin, then dissolving the brittle residue in boiling concentrated ammonia solution and precipitating with carbon dioxide; 250 grms. ethereal extract gave 100 grms. flocculent curcumin, melting-point 140°. Jackson (Ber., 14, 485) also obtained crystallised curcumin by first removing the oil by long extraction with carbon disulphide (sixty hours), then thoroughly extracting (sixty hours) with ether, and after washing the orange- coloured product thus obtained with cold alcohol or ether, crystallising from hot alcohol.
Perkin (Chem. Soc. Trans., 1904, 85, 63) precipitates an alcoholic turmeric extract with lead acetate, washes the lead compound first with alcohol then with water, and decomposes it with dilute sulphuric acid. From the mixture of lead sulphate and curcumin the latter is removed with boiling alcohol and the extract evaporated and poured into ether, which causes the separation of tarry impurities. The ethereal solution, after evaporation to a small bulk, is treated with carbon disulphide and allowed to stand, the crystals which separate from time to time being removed. 0,56 per cent, of curcumin was thus obtained from turmeric.
[---]
Numerous compounds of this type have been described by Ryan and his co-workers, and in a paper by Ryan and Plumkett (ibid., 1916, 199) a list of the dyeing properties of some of the compounds on wool is given, of which the following is an abstract:
| Chromium. | Aluminum. | Tin. | Iron. | |
| Cinnamoyl-acetyl-methane | Dark yellow | Light yellow | - | Bright red |
| Cinnamoyl-benxoyl-methane | Dark yellow | Light yellow | - | Reddish brown |
| Methyl cinnamoyl-pyruvate | Russet-brown | Orange-yellow | Light orange-yellow | Reddish brown |
| Cinnamoyl-pyruvic acid | Brown | Orange | Orange | Deep reddish-brown |
| p-methoxycinnamoyl-pyruvic acid | Chocolate-brown | Bright orange | Bright orange | Reddish brown |
| 3.4 dimethoxycinnamoyl-pyruvic acid | Chocolate-red | Orange-red | Orange-brown | Dark chocolate-brown |
| Curcumin | Brown | Orange-yellow | Orange-red | Brown-black |
The shades given by these compounds are of a similar nature to those produced by curcumin itself, and the results of these authors thus support v. Kostanecki's formula for this compound. In comparing the three compounds, curcumin, methyl 3.4 dimethoxy cinnamoyl-pyruvate, and 3.4 dimethoxycinnamoyl pyruvic acid.
[---]
It is well known that a mixture of boric and hydrochloric acids imparts to turmeric paper a brown colour which is turned blue by alkalis. This reaction was investigated by Schlumberger (Bull. Soc. Chem., [ii.], 5, 194), who found that when an alcoholic extract of turmeric is heated in a sealed tube with boric acid, a red crystalline boric acid derivative is produced, soluble in alkaline solutions with a purple-violet colour. Boiling water decomposes this compound with elimination of boric acid, and formation of pseudo-curcumin, a yellow powder. If the alcoholic solution of the boric acid compound is digested with strong hydrochloric acid, a black substance separates, whereas boric acid remains in the liquid.
On extracting the black powder with a mixture of alcohol and acetic acid, the filtrate deposits green iridescent crystals of rosocyanine.
Rosocyanine is readily soluble in alcohol containing a trace of mineral acid and dissolves in ammonia solution with a blue colour. It is, according to Schlumberger, an unstable substance, and if boiled for a long time with alcohol, is converted into pseudo-curcumin.
Jackson and Clarke (loc. cit.) prepared rosocyanine by heating a solution of curcumin in dilute alcohol with boric and sulphuric acids, and describe it as a purplish-red powder, closely resembling powdered rosaniline. These authors considered it to be isomeric with curcumin, C14H14O4, and described an ammonium salt, C14H13O4NH4, and a potassium salt, C1413O4K, both of which possess an intense blue colour.
The tinctorial properties of curcumin are of special interest, for not only is it a strong colouring matter towards mordants, but with cotton, wool, and silk it behaves also as a substantive dyestuff. In the latter case it is only necessary to add the material to a boiling decoction of the colouring matter. Though considerably employed up to within recent years by the wool and silk dyer in the formation of olives, browns, and other compound colours, turmeric is now but rarely used for dyeing purposes in England. In India, however, it appears to be still in vogue.
Cotton is usually dyed in a decoction of turmeric rendered slightly acid by the addition of a little acetic acid, or alum may be employed The colour does not resist either the action of light or of alkalis, and readily acquires a brownish-red tint. Wool may be dyed without any addition, keeping the temperature about 60°. By previously mordanting with alum a brighter effect is produced, whereas tin mordant gives a more orange colour. Potassium dichromate and ferrous sulphate employed in a similar manner yield respectively olive and brown coloured shades.
Silk is preferably dyed in an acid bath, and is sometimes previously mordanted.
[---]
Ei kommentteja :
Lähetä kommentti