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.
When "seeth" water, the liquid from which the indigo precipitate settles out at the conclusion of the oxidation process, is evaporated to dryness, yellowish-brown to deep brown residues are obtained. These products are extremely hygroscopic and when ground emit an odour resembling that of decayed cheese. Three samples of this material were examined by Perkin (Chem. Soc. Trans., 1916, 109, 211), the first and most important of which, derived from water drawn from an oxidation vat in the Purtabphore factory in India, represented 075 per cent, of the original liquid. As in the process of manufacture 100 parts of I. sumatrana underwent fermentation in the presence of 540 parts of water, this residue corresponded to 4 per cent, of the original plant. Sample (b) consisted of evaporated drainings from the mahl table of the same factory and formed 077 per cent, of the original liquid, whereas the origin of sample (c) was doubtful.
The samples were neutral, in the main dissolved readily in water, and these liquids on acidification emitted a strong odour of volatile aliphatic acids. When incinerated, all yielded considerable amounts of mineral matter which consisted mainly of the oxides of calcium magnesium and potassium, traces of manganese oxide and alumina being also present.
When agitated with boiling water, a small amount of an insoluble brown precipitate separated which in appearance closely resembled indigo brown, and was found to consist of a mixture of compounds of variable nitrogen content. The main constituent isolated as a dark brown amorphous powder, gave on analysis C = 65,70; H = 5,07; N = 8,03 per cent, figures somewhat lower than those found for the main constituent of indigo brown (loc. cit.), whereas the more soluble fraction again contained still more oxygen, C = 64,7; H = 5,0; N = 4,6. From the neutral filtrate a small amount of succinic acid was isolated, the main bulk, approximately 20 per cent, of the "seeth" water residue, consisting of a protein-like compound (N = 8,22) which on heating evolved ammonia and in general property resembled the so-called "indigo gluten" of crude indigo. It consisted of a friable mass, and to the presence of this substance the very hygroscopic nature of the dried "seeth" residue was evidently due.
The following table illustrates the main results obtained by the analysis of the three samples of "seeth" water residue:
| (a) Per cent. | (b) Per cent. | (c) Per cent. | |
| Nitrogen | 2,25 | 2,77 | 2,72 |
| Ash | 27,30 | 25,90 | 26,87 |
| Volatile acids | 23,80 | 21,04 | - |
| Succinic acid | 2,21 | 2,18 | - |
| Brown matter | 5,58 | 12,03 | 11,18 |
| Indigotin | 0,18 | 0,10 | 0,082 |
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