RED • WOODS.

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well known to all dyers, may be explained by the slow alteration and decom-position of substances present in the decoCtion which afifeCt the purity of thehues; it is, moreover, possible that the colouring matter becomes reduced bya special fermentation.

Dr. Dingier* has made known a simple method for purifying from theyellow colouring pigment the decoCtions made with some of the inferior woods,viz., Bimas, Santa-Martha, Aniola, Nicaragua, Siam, and Sappan varieties,which by this method are as excellent for dyeing as the best Fernambucowood. It consists in adding to the boiling liquid wood and small quantitiesof very carefully skimmed milk. The coagulation of the casein causes theprecipitation of the yellow colouring matter along with the casein. Gelatinalso may be applied for the purification of the inferior qualities of these woods.If the shavings or raspings of the woods are moistened with water containing2 kilos, of gelatin to the half hectolitre, and the mass left for some days heapedtogether, the wood yields better results in the dye-beck, because'the colouringmatter is rendered more readily soluble, while the effect of a moist fermenta-tion, which as observed by M. Leuchs, greatly improves some kinds of thesewoods, may in the case mentioned have something to do with the improve-ment of the quality.

The colouring glucoside of Brazil wood is only imperfectly known. Accord-ing to Dr. P. Schutzenberger’s experiments, it is a non-crystallisablesubstancesoluble in water in every proportion, and also in alcohol. Its taste is bitter orsweetish; its colour is a beautifully bright yellow when the substance has notundergone any change. This glucoside maybe obtained by concentrating the de-codtion in vacuum at the ordinary temperature of the air to one-tenth of its originalvolume (sp. gr. 1*075), and then adding either sulphate of soda or common salt.It is thereby precipitated in the shape of a pasty mass completely soluble inpure water. The ordinary commercial extracts of the red woods (their sp. gr.yaries from 1*075 to 1*162) yield, on the addition of water, a yellowish-coloured flocculent precipitate, which would make it appear that the colouringmatter is more readily soluble in a concentrated than in a more dilute liquid,but this reaction is explained by the partial decomposition and oxidation theglucoside undergoes while the preparation of the extract is going on. Theproduct of the splitting-up is kept in solution owing to the state of concen-tration, and by the aid of the saccharine matters present in that solution, andthe precipitation of the more or less modified glucoside, is due to the faCt,that on the dilution of the extract with water the solvent influence of theother substances is decreased.

By the name of bresiline is understood the free colouring principle disengagedfrom its glucosic combination. Bresiline was first studied and isolated byM. Chevreul,f who obtained it by the following process:—The wood, pre-viously ground, is exhausted with water, and the fluid obtained is evaporatedto dryness on a water-bath ; the dry residue is taken up by water again, andthe fluid shaken with some hydrated oxide of lead, in order to saturate the.acids present; the liquid is next filtered, and then again evaporated to dryness,after which the residue is taken up by alcohol; this solution is first somewhat

* See “Annale.s de Chimie,” vol. xvii., p. 323. Dingler’s “ Polytechnisches Journal,”Yol.xxv., p. 80.

1 See “ Annales de Chimie ” (first series), vol. lxvi,, p. 225,