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.
When natural indigo was at its zenith very numerous varieties of this dyestuff were placed on the market, but more recently, owing to its severe competition with the artificial colouring matter, many of these are now rarely met with. From Asia came the indigos of Bengal, Oudh, Madras, Java, Manilla; from Africa those of Egypt and Senegal; and from America those of Guatemala, Caracas, Mexico, Brazil, South Carolina, and the Antilles.
The best varieties are the Bengal, Java, and Guatemala, although in England the Bengal is now mainly employed. Java indigo, formerly largely esteemed for the manufacture of indigo extract, chiefly because of its general purity, at the present time appears to find its market chiefly in the East.
A good quality of natural indigo has a deep violet-blue colour; it acquires a coppery lustre when rubbed with the finger-nail; it is light, porous, adhering to the tongue, and can be readily broken and ground. Low qualities, which contain much extractive and mineral matter, are dull and greyish in appearance, heavy, tough, and hard, and do not become bronzy by rubbing with the finger-nail.
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