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.
Indigo gluten was first isolated from crude indigo by Berzelius (Berz. Jahresb., 7, 26) who extracted it with dilute acid, neutralised the extract with chalk, evaporated to dryness and dissolved out the gluten with alcohol. It was subsequently prepared by Orchardson, Wood, and Bloxam (J. Soc. Chem. Ind., 1907, 26, 4), who describe it as a horny mass, which on grinding gives a light biscuit-coloured powder, and when heated evolves ammonia. In cake indigo it appears to exist in combination with mineral matter, possibly as a calcium compound, for though itself readily soluble in water, it can only be removed from the dyestuff by means of dilute mineral acid. A considerable quantity of this substance is frequently present in indigo, and Perkin and Bloxam (loc. cit.} found that when the crude Bengal variety containing approximately 62 per cent, of indigotin was digested with dilute hydrochloric acid, it lost 21-5 per cent, of its weight. This figure naturally includes some quantity of mineral matter simultaneously removed by the acid. It has been suggested that this compound plays an important rdle in the dyeing operation, and accounts in part for the alleged superiority of natural over artificial indigo. This point, however, has not been scientifically investigated.
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