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.
During the past few years the growers of logwood in Jamaica have been greatly disturbed by the apparent increase on their properties of an unmerchantable variety of the tree known as "bastard" logwood. Bastard logwood is practically devoid of haematoxylin, but contains instead a yellowish-green pigment which, when admixed with the commercial extract, reduces its characteristic tinctorial properties. Chips of the bastard logwood present a yellow, pale pink, white, or even chocolate coloured surface instead of the dark red or purple-bronze tinted colour of the best Jamaican or Mexican logwoods of commerce.
So similar are the trees of the "true" and the "bastard" logwood, that it is frequently impossible to decide whether a tree is really a "mulatto" or not. When first cut a bastard tree is frequently dark enough internally to indicate that it is a good red-wood tree, but instead of darkening with age, as all the best wood does, it remains the same colour or becomes lighter rather than darker.
Chemical tests readily distinguish between the red and bastard wood, for whereas alkaline solutions turn an extract of true logwood a purple colour, with a bastard extract the shade of yellow is merely deepened. Again, mineral acids turn aqueous extracts of true logwood orange to bright red, whereas a bastard extract is not thereby affected.
Dyeing trials, employing stripe mordanted calico, are also serviceable, because, in the case of the bastard variety, the aluminium mordant remains practically colourless.
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