Ventilago madraspatana(CHAPTER I. The Anthraquinone 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.

Ventilago madraspatana (Gaertn.) is a large climbing shrub belonging to the order Rhamnaceæ, the root-bark of which furnishes a dyestuff much valued in Southern India. It is very common in the Western Peninsula from the Konkan southwards, as well as in Ceylon and Burma, and, according to Lostard, it is collected in Mysore at certain periods of the year and exported to other districts of India.

The following are a few of its vernacular names: pitti (Hindi); raktapita (Bengali); pappili-chakka, surralpattai (Tamil); poplichukai (Kan); lokandi, kanwail (Bomb).

The root-bark appears as dark purplish-brown scales, ribbons, or filaments, the dust from which, when it is ground to powder, irritates the throat in a marked manner. When treated with boiling water or alcohol it gives a red solution, which on addition of caustic alkali, changes to a deep crimson.

Perkin and Hummel (Chem. Soc. Trans., 1894, 65, 923), who examined this dyestuff, extracted the root-bark with carbon disulphide, and obtained in this manner a resinous colouring matter, ventilagin, together with the crystalline non-tinctorial substances described below.

Ventilagin, C₁₅H₁₄O₆, consists of a reddish-brown brittle resin which, when distilled with zinc-dust, gives α-methyl anthracene, and when treated with zinc-dust in alkaline solution behaves as a derivative of methyl anthraquinone. Dilute alkalis dissolve it with a purple-violet coloration, and the corresponding salts are obtained as violet precipitates on adding sodium or potassium chlorides to these solutions. According to Perkin and Hummel, ventilagin is possibly allied to alkannin C₁₅H₁₄O₄, the colouring matter of alkanet, Anchusa tinctoria (Lam.), and may differ from this merely by the possession of two additional hydroxyl groups.

Emodin monomethyl ether, C₁₆H₁₂O₅, melting-point 200°, consists of orange-red needles, and is identical with that subsequently isolated from the root of the Polygonum cuspidatum (Sieb. and Zucc.) (Perkin, Chem. Soc. Trans., 1895, 67, 1084). A similar, if not identical, substance was isolated by Schwabe (Arch. Pharm., 1888, 26, 569), and by Thorpe and Miller (Chem. Soc. Trans., 1892, 64, 6) from the bark of the Rhamnus frangula (Linn.), and it is also present in rhubarb and the Rumex ecklonianus (loc. cit.) and Goa powder.

Trihydroxy-a-methyl anthranol-monomethyl ether (A), C₁₆H₁₄O₄, colourless needles, decomposes about 260° before melting, and is soluble in alkaline solutions with a yellowish-brown coloration. On gentle oxidation with chromic acid it is converted into emodin methyl ether, melting-point 200° (loc. cit.), and the same reaction takes place when its alkaline solution is oxidised with hydrogen peroxide. It closely resembles the dehydro-emodin anthranol monomethyl ether, subsequently isolated from Goa powder by Tutin and Clewer (Chem. Soc. Trans., 1912, 101, 290).

Trihydroxy-a-methyl anthranol-monomethyl ether (B), C₁₆H₁₄O₄, pale yellow needles, melting-point 173°, when oxidised with chromic acid is also converted into the emodin methyl ether, melting-point 200°. As two methyl anthranols are capable of existence, the isomerism of these compounds may possibly be thus explained: [KUVA PUUTTUU]

Substance C₁₆H₈O₈, orange-red crystalline powder, melting-point 275-280°, is soluble in alkaline solutions with an orange-red coloration, and when heated with zinc-dust gives a hydrocarbon which resembles α-methyl anthracene.

Substance C₁₇H₁₂O₅? is a chocolate, crystalline powder, soluble in dilute alkali with a yellow coloration, and this solution, on exposure to air, deposits a blue amorphous precipitate.

Dyeing Properties.

On striped printed calico the root-bark gives with alumina mordant a claret-red, not unlike that of alizarin bordeaux; with iron mordant a greyish-lilac, which in strong colours approaches a black; and with a mixture of the two a very purplish dark chocolate. The colours are moderately fast to soap, although considerably behind the alizarin colours in this respect. On oil-prepared calico ventilago gives with alumina mordant a rich claret brown, with chromium mordant a very black purple, and with iron mordant a good purplish-black shade. On wool chromium mordant gives a good purplish-brown, alumina a bordeaux red, tin a brighter red similar to an alizarin red with alumina mordant, and iron mordant gives dark dull purple and black. On silk similar colours are produced. No difficulty is experienced in dyeing with ventilago, and no additions to the dye-bath are necessary, except in the case of wool, with which it is desirable to add calcium acetate in order to correct the strong acidity of the mordanted fibre. Owing to the slight solubility of the colouring matter in water, the dyeing does not commence until the temperature reaches 70-80°. The root-bark appears to contain from 8-10 per cent, of ventilagin.