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.
* In this chapter is embodied much of an article by the late J. J. Hummel in Thorpe's "Dictionary of Applied Chemistry".UNTIL the advent of the synthetic dyestuffs, the natural dyestuffs formed the only source of the manufacture of organic pigments (lakes), and though their importance for this purpose has been reduced to a minimum, some of these are, or were until recently, employed for the production of lakes for certain special purposes. A general account of the more important of these older lakes is given here, chiefly as a matter of historical interest, for there can be little doubt that all, or at least most of these will eventually become obsolete.
According to Pliny, the dried scum collected by the dyers of Tyrian purple from their dye liquors furnished a costly purple - coloured pigment employed by painters. The indicum of the Roman artists was probably obtained in the same manner from a woad or indigo vat. Caneparius, a Venetian writer on dyeing in 1619, states that it was the custom of dyers to evaporate the waste lac dye liquors in order to obtain an artificial lac used by artists.
Similar pigments were afterwards prepared or collected from the waste dye liquors of kermes, brazilwood, etc. Such pigments were called by the Italians laccae, and these were distinguished from each other by adding the name of the substance whence the colour was derived, e.g. lacca di verrino (brazilwood), lacca di grana (kermes), lacca di cremise, etc.
As to the word lake itself, the Indian "lac" or "lakh" means a hundred thousand, and refers to the immense numbers in which the lac insects (Coccus laccae] appear at certain seasons on the branches infested by them.
At the present time true lakes are like those of the early days, being, as is well known, insoluble metallic compounds of organic colouring matters.
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