Lapachol.(CHAPTER II. The Naphthoquinone 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 colouring matter has been obtained from the wood of the Lapacho tree, from Greenheart wood, and also from Bethaberra wood. It was from the first-named that Arnaudon (Comptes rend., 1858, 46, 1154) originally obtained it by extracting the wood with alcohol, and recrystallising the product from a mixture of alcohol and ether. Stein (J. f. pr. Chem., 99, 1) showed that the same colouring matter was present in Greenheart wood, whilst Green and Hooker (Amer. Chem. Jour., 11, 267) obtained it from Bethaberra wood.

According to Paternò (Gazetta, 12, 337; 21, 374) the colouring matter is best extracted from the wood by means of soda solution (1 gram soda crystals in 16 grams water for 20 grams finely divided wood), the product being precipitated from the combined extracts by means of hydrochloric acid, purified by extraction with barium hydroxide solution and reprecipitation with acid. The product thus obtained when recrystallised from benzene is readily obtained in a pure condition.

Kermes(CHAPTER I. The Anthraquinone 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.

Kermes is the most ancient dyestuff on record, for it was known in the time of Moses, and is mentioned in Scripture by its Hebrew name, "tola" or "tolaschani". According to Tychsen (Bancroft's "Philosophy of Permanent Colours," i, 394), "the scarlet or kermes dye was known in the East in the earliest ages before Moses, and was a discovery of Phoenicians in Palestine, but certainly not of the small wandering Hebrew tribes". Under the name "coccus" it is frequently referred to by the Greek and Latin writers.

Kermes is an insect found on the oak kermes (Quercus coccifera, Linn.), and when living the female insects, which are fixed to the twigs of the tree, resemble bluish berries, and are covered with a whitish powder. As soon as their eggs are on the point of hatching these insects should be collected, killed by exposure to the steam of vinegar, and dried, and the product has then the appearance of pale reddish-brown grains. According to Bancroft, it would require 10 or 12 lbs. of kermes to produce the effect of a single lb. of cochineal.

Kermesic acid, C₁₈H₁₂O₉, the colouring matter of kermes, was first isolated, in the crystalline condition, by Heisse (Arbeit, a. d. K. Gesundheitsamte, 1895, 513), and has since been examined by Dimroth (Ber., 1910, 43, 1387; and Annalen, 1913, 399, 43). To isolate the kermesic acid, the kermes is first extracted with ether to remove wax, and this has been examined by Dimroth and Sherndal (Annalen, 1913, 399, 43), and identified as ceryl cerotate, C₅₂H₁₀₄O₂. The residue is then allowed to stand overnight with an ethereal solution of hydrochloric acid, by which means the kermesic acid, which exists in kermes in the form of a salt, is liberated and made capable of removal by repeated extraction with ether. For the purification of the substance, it is converted into its sparingly soluble sodium salt, which allows of its separation from flavo-kermesic acid, a substance stated by Dimroth to be present in kermes dye to the extent of about 0.06 per cent. the sodium salt of this being soluble in hot 2N sodium acetate solution, whereas the disodium salt of kermesic acid is almost insoluble. The sodium salt when dissolved in boiling sodium hydroxide solution and treated, whilst boiling, with excess of hydrochloric acid, yields a crystalline precipitate of kermesic acid.

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Kermesic acid is thus closely related to carminic acid, which is also considered by Dimroth to be a derivative of anthraquinone.

Dyeing Properties.

According to Hellot (Bancroft, "Philosophy of Permanent Colours," i, 404), "the red draperies of the figures exhibited in the ancient Brussels and other Flemish tapestries were all dyed with kermes". "The fine red or crimson colour of these tapestries, which was originally called simply scarlet, took the name of Venetian scarlet, after the cochineal scarlet upon a tin base was discovered...."

For the production of this scarlet, the wool, previous to dyeing, was mordanted with alum and tartar; and, according to Bancroft, there is no evidence even in more recent years of the employment of a tin mordant in respect of this colouring matter, although the experiments he carried out indicated that by this latter method a scarlet could be produced "in every respect as beautiful and estimable as any which can be dyed with cochineal".

Lac Dye(CHAPTER I. The Anthraquinone 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.

Lac dye is produced by an insect, the Coccus lacca or ficus, living on the twigs of various kinds of trees, particularly the Ficus religiosa (Linn.), the Zizyphus jujuba (Lam.), and the Butea frondosa (Roxb.). These insects appear usually in November, and subsequently fasten themselves to the fleshy portions of the young branches. Gradually the abdomen of the insects becomes covered by a viscous fluid, which slowly forms a cellule surrounding the animal. The substance composing this cellule is the stick lac. The cellule attains its full size in March, and the insect then exhibits the appearance of a red oval- shaped, smoothly polished lifeless sack entirely filled with a beautiful red liquid; its size is then the same as that of the fully grown cochineal (Crookes, "Dyeing and CalicoPrinting," p. 354). Commercial stick lac is chiefly gathered on the hilly banks of the Ganges in India, that for dyeing purposes possessing a deep red colour, whereas the pale perforated kind in which no insects exist is employed for varnish-making, and constitutes the material for shellac.

Of lac, the following varieties occur: stick lac, the crude product together with the twigs upon which it is formed: grained lac, the material removed from the twigs; and caked lac, the latter variety fused and cast into moulds.

Such a resinous material is not suitable for dyeing purposes, and a simple process is adopted to remove the colouring matter from the resin, or at least to obtain it in a more concentrated form. This consists in extracting the stick lac with hot dilute sodium carbonate solution, evaporating the extract, and moulding the residue into square cakes. According to Crookes (loc. cit.) the product, which is lac dye, contains on an average about 50 per cent, of colouring matter, 25 per cent, of resin, and 22 per cent, of earthy impurities.

Lac dye is an extremely ancient dyestuff, and was employed in the East for many centuries before it was known in Europe. It appears to have been introduced into this country about 1790. Early in the last century, lac dye was a very important article of commerce, so much so that at one time shellac was practically a bye-product of its manufacture. The position of these products has now been reversed, for whereas the dyestuff is almost defunct, the shellac industry is of considerable importance.

According to the older writers, the colouring matter of lac dye was considered to be identical with that of cochineal, but that this is not the case has been clearly indicated by Schmidt (Ber., 20, 1285).

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Dyeing Properties.

The dyeing properties of lac dye are practically identical with those of cochineal, but the shades obtained are somewhat faster. Owing to the resinous and mineral impurities accompanying the colouring matter, it is not readily soluble in water, and before use it is therefore ground to a paste with the requisite quantity of tin spirit together with a little hydrochloric acid, and allowed to stand overnight. Cochineal and lac dye can be used together with advantage, or after the wool is dyed with lac it may be entered into a fresh bath with cochineal. Its employment at the present time is, however, extremely limited.

Fowler (Indian Textile Jour., 1917, 244) has made attempts to standardise various Indian colouring matters so that they may be marketed in uniform strengths. It would appear that "Lac dye" is one of those with which he has been concerned.