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.
Prunicyanin, the pigment of the sloe (blackthorn, Prunus spinosa, Linn.), is a compound that closely resembles mekocyanin.
A certain amount of information has been obtained concerning this pigment by Willstatter and Zollinger (Annalen, 1916, 412, 164), but the results published are only preliminary, and the colouring matter has not, as yet, been obtained in a crystalline condition. Only the skins of the fruit were used for the preparation of the pigment, these being extracted with glacial acetic acid, and after addition of alcohol, the colouring matter precipitated by means of ether. After several fractional precipitations from alcoholic solution by addition of ether, various methods of purification were resorted to, and the pigment finally obtained as small spherical particles - "kuglig kryst. Gebilde".
Prunicyanin chloride, thus prepared, closely resembles mekocyanin in most of its properties, viz. an acid solution on addition of sodium carbonate gives a bluish-violet colour, with caustic soda blue; ferric chloride added to an alcoholic solution produces a pure blue coloration. Like mekocyanin chloride, it is unusually soluble in hydrochloric acid of various concentrations, and also has the interesting property of passing into solution in a small quantity of cold ethyl alcohol and being again deposited from this in a bulky sponge-like form possibly micro-crystalline. It differs from mekocyanin chloride in having a distribution number (viz. 9.5) very close to that obtained for normal monoglucoside anthocyans, but as hydrolysis of prunicyanin chloride, together with pentose estimations, prove that it yields cyanidin chloride, rhamnose, and a hexose (not yet identified), probably in molecular proportions, the high distribution number is not explained by its being a monosaccharide, but by the presence of rhamnose in the molecule (cf. keracyanin and violanin).
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