IRLDIUM (i-rid'e-um), a tetrad me tallic element of the platinum group; symbol Ir.; at. wt. 193.1; discovered by Tennant in 1804, in the black powder which remains when crude platinum is dissolved in nitro-hydrochloric acid. This powder is an alloy of iridium and osmium, called iridosmine or osmiridium. Iridium is a white, brittle, very hard metal, fusible with great difficulty, in the flame of the oxy-hydrogen blowpipe. It is insoluble in all acids, but when re duced by hydrogen at a red heat it oxi dizes.slowly and dissolves in nitro-hydro chloric acid.
IRIS (i'ris), in classical mythology, the messenger of the gods who carries messages from Ida to Olympus, or from the gods to men. In the "Iliad" the rain bow also was called Iris.
In astronomy, an asteroid of the group between Mars and Jupiter, discovered by Hind in 1847.
In botany, the flower-de-luce, the typi cal genus of the order Iriclacem. The species are very numerous, and are gen erally remarkable for their large, yellow, white, or blue flowers, and sword-like leaves. They abound in Europe, but are
rare in America. The rhizomes of sev eral species are more or less purgative and emetic. Those of I. fiorentina, pall ida, and germanica possess a violet odor, and are used in perfumery for imparting an agreeable odor to the breath, and by the French especially for making issue peas. These rhizomes, dried and scraped, constitute the orris root of the shops. The roasted seeds of I. pseuda cora, the yellow flag, have been recom mended as a substitute for coffee, but they do not appear to have any of the valuable properties of that beverage. The genus is so named on account of the variety of colors exhibited by it.
In anatomy, the anterior part of the choroid coat of the eye, with superadded muscular fibers.
In jewelry, the name given by French jewelers to limpid and transparent stones, but chiefly to rock crystal when reflecting prismatic colors like opal, by means of natural internal flaws.