Green EbonyCHAPTER XVIII. Colouring Matters of Unknown Constitution.(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.

Green ebony is a yellow dyewood formerly employed to some extent in this country, but is now almost entirely replaced by other colouring matters. It is a native of Jamaica or West India, and is obtained from the Excœcaria glandulosa (Siv.) or Jacaranda ovalifolia (R. Br.). The trunk of the tree is about 6 inches in diameter; the wood is very hard, and of an orange -brown colour when freshly cut, and stains the hands yellow. References to this dyestuff are meagre, and it does not appear to have been ever largely employed. Bancroft ("Philosophy of Permanent Colours," 1813, ii., 106) states that green ebony contains a species of colouring matter very similar to that of the Chlorophora tinctoria (Gaudich) (Old fustic), and is sometimes employed in its stead; and O. Neill ("Dictionary of Calico Printing and Dyeing," 1862) mentions that it is used in dyeing greens and other compound shades. Until recently it had a limited sale in Yorkshire as a dye for leather, but appears to have entirely passed out of use as a woollen dyestuff. It is now little used in silk dyeing, but was formerly employed for greening blacks.

Green ebony contains two crystalline colouring matters, which are distinguished by the fact that whereas one, exccecarin, is not precipitated by lead acetate solution, the second, jacarandin, is completely deposited by this reagent (Perkin and Briggs, Chem. Soc. Trans., 1902, 81, 210).

Excœcarin, C₁₃H₁₂O₅, crystallises in lemon - yellow needles, sparingly soluble in cold alcohol, and melting with effervescence at 219-22°1. It is soluble in aqueous and alcoholic alkaline solutions with a violet-red coloration, and these liquids, on exposure to air, are rapidly oxidised, and assume a brown tint.

Excœcarin does not dye mordanted fabrics, but is a substantive dyestuff in that it has a weak but decided affinity for the animal fibres with which it gives, preferably in the presence of tartaric or oxalic acid, yellow shades.

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Jacarandin, C₁₄H₁₂O₆, yellow plates or leaflets, melting-point 243-245°, dissolves sparingly in alcohol and the usual solvents to form pale yellow liquids having a green fluorescence. With caustic alkali solutions it gives orange-red liquids; with alcoholic lead acetate a bright orange coloured precipitate; and with alcoholic ferric chloride a dark greenish-black solution. It dyes mordanted woollen fabrics the following shades:
Chromium. - Dull yellow-brown.
Aluminium. - Orange-brown.
Tin. - Bright golden yellow.
Iron. - Deep olive.

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As indicated by Bancroft (lot. cit.) the colours given by green ebony are similar in character to those yielded by old fustic. Employing mordanted woollen cloth the following shades are produced:
Chromium. - Dull yellow-brown.
Aluminium. - Dull brown-yellow.
Tin. - Golden yellow.
Copper. - Pale brown.
Iron. - Olive-green.

Rith 40 per cent, of the dyewood the iron mordant gives greener and brighter shades than with larger amounts, in which case a browner colour is produced. Possibly from this green shade, and the extremely hard and compact nature of the wood, the name "green ebony" has originated.