RIEMATO'XYLINE is a chromogen (a term used by chemists to denote certain nearly or quite colorless substances 'which, under certain influences, yield well-marked colors) obtained from logwood (hamataxylon compeachianum.) Its composition is tepee 'sented by the formula Cs,II1401, Gaq., and in its pure state it occurs in transparent glistening straw-colored prisms. It has a sweet and not astringent taste, is sparingly soluble in cold water, but dissolves readily in boiling water, alcohol, and ether. The watery solution is not affected by the oxygen of the air, but if a very small quantity of ammonia is added, it. assumes an intensely reddish purple color.
Hxmatoxyline is obtained by mixing powdered extract of logwood with quartzose sand (to prevent its agglomeration into lumps), and digesting this powdar for several clays with about six times its volume of ether. The is then distilled till the 'residue assumes the consistence of a sirup. If this residue is mixed with water, crys tals of brematoxyline are in a few days deposited, which on an average weigh about one-eighth of the extract that was employed.
The color reactions of this substance with metallic compounds are singular, and in consequence of the tinctorial power of some of them, deserve a brief notice. Solution
of acetate of lead gives with one of htematoxyline a white precipitate, which spcedily becomes blue; salts of copper give a dirty green precipitate, which also soon becomes blde; chloride of barium produces a red precipitate; protochloride of tin gives a rose colored, and iron alum, a scanty blackish precipitate.
The purple color which the solution of htematoxyline assumes if oxygen and ammonia are present, is due to a decomposition, of which a substance termed Iumatein is one of the products; the compound resulting from the union of hmmatein and ammonia possessing this tint.
The solution of hmtnatein-ammonia (or htemateate of ammonia, as sonic chemists have termed it) yields colored precipitates with many metallic salts; with acetate of lead, it gives a deep blue, with sulphate of copper, a violet blue, with protochloride of tin, a violet. and with iron alum. a black precipitate.
It is upon the reactions which have been described in the preceding para graphs that the value of logwood as a dye depends.
ILEMO—in compound words. See IIEM0—in compound words.