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.
Barbatic acid, C19H20O7, was first isolated from the lichen Usnea barbata by Stenhouse and Groves (Chem. Soc. Trans., 1880, 37, 405), in which it occurs in conjunction with usnic acid. Zopf (Annalen, 1897, 297, 271) found barbatic acid in the Usnea longissima, in the Electora ochroleuca (ibid., 1899, 306, 282), and in the Usnea dasypoga (ibid., 1902, 324, 39); Hesse (J. pr. Chem., 1898, ii., 57, 232) describes its presence in the Usnea longissima, Usnea barbata, and Usnea ceratina. Hesse (loc. cit.) originally considered that barbatic acid had the composition C22H24O8, and described potassium barium and copper salts and an ethyl ester, melting-point 132°, which apparently established this formula, but in a later paper (J. pr. Chem., 1903, ii., 68, i) he adopted Stenhouse and Groves' formula, C19H20O7. The sodium salt, C19H19O7Na, 2H2O, crystallises in straight-sided leaflets (compare also Zopf, 1902, 789). The action of acetic anhydride on barbatic acid leads to the formation of a compound which is probably the lactone of acetylbarbatic acid; this melts at 250° and on recrystallisation from acetic anhydride yields acetylbarbatic acid, C19H19(C2H3O)O7, melting-point 172°. By the hydrolysis of barbatic acid with aqueous alkalis betorcinol and rhizoninic acid are formed. Barbatic acid crystallises in colourless needles, melting-point 184° (Hesse, J. pr. Chem., 1906, (2), 73, 113).
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