ARCHIL, iirtkil (of uncertain origin), or ORCHIL, or'kil (Orseille). A coloring sub stance obtained from various species of lichens. The archil is not originally present in the lichens, but is developed by the following treatment : The lichens, collected from rocks near the sea, are ground into a pulp with water and diluted am monia is added; certain colorless acids (erythric acid, etc:) contained in the lichens gradually change, under this treatment, into a purple sub stance, orecin, which is the coloring principle of archil, (If in the same process. the carbonate of sodium or of potassium is added to the pulp, ordinary litmus is produced in place of orrein.) Archil is used in the dyeing of silks and of woolen cloth where a beautiful brown color is re quired; but though a brilliant rich hue is im parted to the fabric, the color is not permanent, being easily acted upon by the rays of the sun.
Hence archil is seldom used by itself : the fabric is first dyed by another coloring matter. and then archil is applied to impart to it a brilliant lustre.
Arehil imparts a beautiful and durable violet color to marble. It has also been used in coloring willes. It is brought into the market in three di rent forms. The name archil is commonly applied to the ordinary pasty form. When offered in the form of a dry mass it is called persis, while powdered archil is known as cud bear. The lichens used in the manufacture of archil grow on the rocky coasts of South America, Madagascar, Zanzibar, the Canary Isles, and a number of other places. They belong principally to the genus Poccella. They are sometimes called orchella-weed, or dyer's moss.