Ure says or-molu contains more copper and less zinc than ordinary brass, and that although, in many of its applications, the colour is heightened by means of a gold lacquer, in some cases the true colour of the alloy is best preserved after it has been properly developed by means of dilute sulphuric acid.
ORMSKIRK MEDICINE. A nostrum supposed to prevent hydrophobia, so named after the residence of its inventor, Mr Hill, of Ormskirk. It is said to have consisted of the ingredients named below, but nothing certain is known on the subject, as the inventor died without revealing its secret:—Chalk, 1⁄2 oz.; Armenian bole, 3 dr.; elecampane root, 1 dr.; alum, 10 gr.; oil of aniseed, 5 or 6 drops; all in fine powder. For a dose, to be taken for 6 successive mornings, in a glass of weak milk and water.
OR′PIMENT. Native yellow sulphide of arsenic. The finest samples used by artists (golden orpiment) come from Persia. See Arsenic (Tersulphuret).
OR′RIS. Syn. Orris root, Florentine r.; Radix iridis, L. The dried rhizome of Iris Florentina, pallida, and Germanica. Sialogogue, irritant, subacrid, and errhine. Chiefly employed to impart a violet odour to oils, tooth powder, snuffs, spirits, &c.; and when cut into peas to keep open issues.
ORSE′DEW. Dutch leaf-gold.
ORSEL′LIC ACID. Two compounds pass under this name—ALPHA-ORSELLIC ACID and BETA-ORSELLIC ACID. They closely resemble each other, and are obtained in a similar manner; the first from the South American variety of Rocella tinctoria, the last from that grown at the Cape.
ORSELLIN′IC ACID. Syn. Lecanoric acid. A compound formed along with picroerythrine, by boiling erythric acid for some time with water. It is also formed by boiling alpha-orsellic acid with water. In both cases, if the ebullition is too long continued, the new acid is wholly or in part converted into orcin.
Prop., &c. Crystallisable; bitter-tasted; soluble in water; its aqueous solution, by exposure to the air, assumes a beautiful purple colour.
ORTHOCLASE. Syn. Potassium felspar. This material, which is a double silicate of potassium and aluminium, enters into the composition of many rocks, and is a common ingredient in granite. It has the following composition:—Silica, 64·8 parts; alumina, 18·4 parts; and potash, 16·8 parts. Part of the potassium is frequently replaced by small quantities of calcium, magnesium, and sodium.
Orthoclase is used for glazing the finest varieties of porcelain, a very intense heat being necessary to effect its fusion in the porcelain furnace. By the Chinese potters it is called petuntze. “The name ‘orthoclase’ is generally restricted to the subtranslucent varieties, there