RED WOODS.

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astringent principles, organic acids combined in various ways, resins, andmineral salts.* Hitherto only one colouring matter has been found in thesewoods, but the absence of others, however analogically probable, is notformally demonstrated. The colouring material is totally soluble in water, andcan be extradted from the ligneous matter by repeated decodtions or infusion.It exists in the wood in an almost colourless state, or at least its colour isonly a pale yellow, but on coming into contadt with air this hue becomesgradually darker, and at last red-brown. There appears to be slow oxidationof colourable matter to form a real pigment. The aqueous decodtions of thesewoods are yellow at first, and only assume a red by the adtion of air or theaddition of aerated water (that is, ordinary fresh water, which, not having beenboiled, contains air). This phenomenon, however, is somewhat dependent onthe variety of the wood, and also on the fadt of its more or less immediateuse after being ground to powder. The colouring matter is supposed bysome to exist in these woods as a glucoside, since the decodtion exerts verylittle reducing adtion upon a cupro-potassic solution ; but when the decodtionhas been heated for some time with either sulphuric or hydrochloric acids ityields, on treatment with the cupro-potassic test, an abundant precipitate ofred oxide of copper. After the splitting-up of the glucoside has beeneffedted the colouring matter exhibits a tendency to crystallise, which it didnot previously possess. It is only required to treat the acidified decodtionwhile yet hot ( T J 5 th of acid is sufficient) with an alkaline salt, when, oncooling the fluid, there will appear a more or less red-coloured crystallinesubstance, its shade depending on the degree of oxidation it has undergone.The addition of the alkaline salt has the effedt of diminishing the solubilityof the colouring matter. There exists, therefore, in the decodtions of the woodsa colourable glucoside in a more or less advanced state of oxidation ; and,moreover, a certain proportion of free colouring matter, which either pre-exists as such in the wood, or is formed during the boiling with water by thesplitting-up of the glucoside.

The colourable glucoside, which is very abundantly present in freshly-made decodtions of the wood, is not precipitated by neutral acetate of lead,but is thrown drown by the subacetate. When a solution of the neutralacetate is added to a decodtion there is formed a bulky brick-red precipitate,which contains, besides tannin and some foreign substances, chiefly bresi-line and colouring matters already oxidised. The filtrate from this precipitate,a faintly yellow liquid, dyes up shades of equal richness, but of far more beautythan the original decodtion. This liquid, moreover, yields, on being treatedwith basic acetate of lead, an abundant lilac precipitate. Oxidation of thecolouring matter is a slow process in the first place, and requires especiallyconditions which favour it, and among these ammoniacal vapours and thefaintest traces of potassa or soda are the chief agents. Decodtions of mostof these woods may be kept even in open vessels for several monthswithout any very prominent change being observable. The colour of theliquid remains bright yellow, while the rasped wood becomes rapidly brown,an effedt, as regards the latter, due to the presence in the wood of substances

* Generally speaking our knowledge about wood is very limited, and it is to be regrettedthat the wares here named have not been more fully studied. They deserve it equally withsuch kinds of wood as ebony and iron-wood, and many others, the products of warmer climes.

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