EXTRACTS OF DYE-WOODS.

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Saw-wort ( Serratula tinctoria). —This plant is stated by Bancroft to yieldyellow shades resembling those produced by weld.

Sunflower Seeds contain helianthic acid, which, when treated with dilutehydrochloric acid in a current of hydrogen, is resolved into glucose and aviolet dye.

“ Syria.”—Under this curious name is sold the imperfeCtly-exhaustedresidue of Coccus ilicis.

Viridic Acid, a colouring matter contained in unroasted coffee. It isturned a fine deep green by alkalies, and dissolves in sulphuric acid with acrimson colour, but on the addition of water is deposited in blue flakes.White of egg placed in contact with raw coffee-beans takes a fine green colourwhich might be advantageously used by confectioners, instead of the unwhole-some pigments sometimes employed.

Virginia Creeper (Ampelopsis hederacca). —The red leaves of this well-known climber contain a red colouring matter, cissotannic acid.

Preparation of Extracts of Dye-Woods.

We have now to turn our attention to a collateral branch of the dyeingoperations, viz., the mode of preparation of extradts of the dye-woods employedby the dyers and calico-printers. This manufacture has sprung up with themore extensive use of the wares in question, and is of comparatively recentdate, owing in part also its origin to the fact that the dye-woods are notdirectly fit for use in the calico-printing business. The manufacture of theseextracts is carried to a high degree of perfection, and is performed in thefollowing manner:—By means of suitable machinery, the woods are reducedto a coarse powder, or to small chips cut generally in a direction perpen-dicular to their fibres. This operation requires also a large amount of movingpower. The coarse powder or chips thus obtained are directly exhausted bymeans of water, or are left exposed in heaps, in a moist state, to a kind ofoxidising fermentation, whereby the solubility of the colouring matter isincreased and the exhaustion thereof by water facilitated. This is especiallydone for logwood.

It is clear that in order to carry on the exhaustion of the woods with theleast possible expenditure the quantity of water to be used should be as smallas possible, because the greater part of that vehicle has to be got rid of byevaporation. Some manufacturers carry on their operations in open tanks,applying water at 60° or ioo°, but others prefer to work at a temperature aboveloo 0 , and then of course in closed vessels. The annexed figure (Fig. 23) givesa view of the construction of these vessels: c represents a copper boiler fixedbetween two cast-iron columns, D, so as to be movable on the imaginary axis,a a, that is to say that c at the top of the figure can, by turning the boilerround that axis, be brought to where q stands in the figure, and be reversedagain if required; b, manhole, hermetically closed by means of the screw, c ;e e i two handles or rings, fit for lifting off the piece b , manhole cover; f, copper-made false bottom, perforated with holes; to this piece of copper is fasteneda piece of brass wire gauze of narrow gauge; K, perforated worm tube, whichby means of the pipe,!, communicates with a steam-boiler. The pipe g,which communicates with the cavity below the false bottom, is in con-nection with three tubes, furnished with three taps, 111, n, and 0 (the latter is not,