ARCHIL, or Oltenia., is a coloring substance obtained from various species of lichens. • The A. is not originally present in the lichens, but is developed during a pro cess of putrefaction and fermentation. The lichens, collected from rocks near the sea, are cleaned, ground into a powder with water, placed in tanks, and ammoniacal liquids— such as purified gas liquor or stale urine—added; when, by the combined influence of the ammonia, air, water, and the constituents of the lichens, a violet-colored matter is generated, which appears for a time to dissolve in the water, but finally falls to the bottom of the vat in the condition, of a moist powder or paste. The latter is then mixed with some substance like chalk or stucco, to give it consistence. The lichens which yield the best A. in largest quantity, are roecella tinetoria and fucifornds. The former is called the Archil plant, and is obtained in large amount from the Canaries and Cape de Verd island, and the Levant. Another lichen, keanora tartarea, collected from rocks in Sweden, is largely imported into Britain. It is sometimes called cudbear (q.v.), or cudbear lichen, and sometimes white Swedish moss. A. is soluble in water and in alcohol, to either of which it imparts a violet color, with a good deal of a crimson hue. It is much employed in the dyeing of silks, where a beautiful lilac color is required; but though a brilliant rich hue is imparted to the silken fabric, the color is not a permanent one, being easily acted upon by the rays of the sun. Hence the A. is seldom used by itself, and the cloth is first dyed lilac by another coloring matter, and is then passed through an A. dye, which imparts a brilliant lilac hue to the cloth. A. is seldom employed to dye cotton cloth, but it is often used, along with indigo, in the dyeing of woolen cloth; and besides enabling the indigo color to go much further, it imparts its peculiar rich tint to the blue or black cloth or yarn immersed in it ; the color, however, so obtained is not so permanent as where the A. is left out. Cudbear (q.v.) and litmus (q.v.) are ainflorrous to A., and are obtained from the same lichens.
The lichen distinguished by the name of the A. plant or lichen, roceella tinctada, grows very sparingly on the southern coasts of England, but abundantly on the shores of the Mediterranean and of the neighboring parts of the Atlantic, where it often covers rocks near the sea, so as to form what has been likened to a sort of turf upon them. The
Spanish name is ordglia, from which the French orseille, the English A. or orehil, and even the botanical name roceella, are derived. It is of a substance between cartilagi nous and leathery, roundish, pretty erect, branching in a dichotomous manner, of a gray ish brown color, with powdery warts (soredia); the apothecia (q.v.) orbicular, fiat, horny, almost black, with a scarcely prominent border. That from the Canary isles is gen erally regarded as the best. It seldom exceeds the thickness of a pin, and about an inch and a half in length. A less branched and more slender, prostrate, or pendulous variety (roccella hypomecha of Bory de St. Vincent) is common at the cape of Good Hope and in the island of Mauritius, and appears in commerce along with the other, but is of very inferior quality. A variety remarkable for its large.size, or perhaps a distinct species (R. itaccida), is brought from Lima and other parts of the w. coast of South America; it is sometimes as thick as a goose-quill, and 6 or 8 in. long, and is of excellent quality. All these, and ,roceella fucifonnis, very generally receive in commerce, and from A. makers, the name of orchella weed, the different kinds being distinguished according to the countries from which they are imported. They are also popularly called dyer's moss.—R. fuciformi-s now yields perhaps more of the A. or orchella weed of commerce than R. tinetoria. It differs from R. tinetoria chiefly in being not rounded, but flat, and in having the apotheda, very distinctly bordered. tt grows in similar situations, and is also a native of Britain, but abundant only in warmer climates, as on the coasts of Africa, Madagascar, etc. That from Angola is reckoned of the very best quality.
Among the lichens from which A. is manufactured is the parelle Aurergne or orseille de terre (ground A.) of the French, e-ariotaria oreina or corallina, which is gath ered for this purpose in mountainous districts of the s. of France and other parts of the s. of Europe, and is also an article of export (with other similar lichens) from Sweden to Holland. But the greater facility with which A. of the finest quality can be procured from the species of roccella, and the increasinga bundanee of the supply from different quarters, particularly from Angola, tend to oiminish the demand for other lichens.