very powerful diuretic. Another crystallisable resinous body named arbutin has also been discovered in them. Bearberry leaves either in the form of powder, infusion, or extract, are chiefly used in chronic diseases of the bladder, in which there is an abnormal secretion of mucus, such as catarrhus vesicæ, but neither acute nor active inflammation.
VACCINA′TION. See Cow-pox. (Pox.)
VAC′CINE MATTER. Syn. Lympha vacciniæ, L. This is collected either upon the points of lancet-like pieces of ivory, or by opening the pustule, and applying a small glass ball and tube (like those called by the boys in London candle-pops, or fire-pops) to the orifice, expelling part of the air in the ball by bringing a lighted taper near it; then, withdrawing the taper, the matter is sucked into the ball, in which it may be sealed up hermetically or cemented, and thus kept for a length of time. It is, however, now generally preserved between two small pieces of glass, or in straight capillary glass tubes. It is said that cotton thread is a convenient and efficient vehicle. The matter may be liquefied with a little clean water before application. A degree of heat scarcely higher than that of the blood lessens its efficacy.
VAC′UUM. Empty space; a portion of space void of matter. For experimental and manufacturing purposes, a sufficient vacuum is produced either by means of the air-pump, or by filling an inclosed space by steam, which is then condensed by the application of cold. Evaporation proceeds much more rapidly, and liquids boil at much lower temperatures in an exhausted receiver than when exposed to the air. Thus, under ordinary circumstances, in the air, ether boils at 96°, alcohol at 177°, and Water at 212° Fahr.; but in vacuo water boils at about 88°, alcohol at 56°, and ether at -20° Fahr. In the best vacuum obtainable by a powerful air-pump, water placed over oil of vitriol, to absorb the aqueous vapour as it forms, will often enter into violent ebullition whilst ice is in the act of formation on its surface. The reduction of the boiling-point with reduced pressure is practically taken advantage of by the pharmaceutist in the preparation of extracts, by the sugar refiner in the evaporation of his syrups, by the distiller in the production of certain liqueurs, and by the chemist in a variety of processes of interest or utility. See Extracts, Evaporation, Refrigeration, &c.
VALE′′RIAN. Syn. Valerianæ radix (B. P.), Valerianæ radix, Valeriana (Ph. L. E. & D.), L. “The root of the wild plant Valeriana officinalis (Linn.), or wild valerian.” (Ph. L.) An excitant, antispasmodic, tonic, and emmenagogue, not only acting on the secretions, but exercising a specific influence over the cerebro-spinal system, and in large
quantities producing agitation, mental exaltation, and even intoxication.—Dose, 10 to 30 or 40 gr., thrice daily; in hysteria, epilepsy, headache (affecting only one side), morbid nervous sensibility, &c. Even the odour of it exerts a species of fascination over cats.
VALERIAN′IC ACID. HC5H9O2. Syn. Valeric acid; Acidum valerianicum, A. valericum, L. Prep. 1. A mixture of potato oil or corn-spirit oil (hydrated oxide of amyl) with about 10 times its weight of quicklime and hydrate of potassa in equal proportions, placed in a glass flask, is kept heated to about 400° Fahr., for 10 or 12 hours, by means of a bath of oil or fusible metal; the nearly white solid residuum is mixed with water, an excess of sulphuric acid added to the mixture, and the whole subjected to distillation; the distillate is supersaturated with potassa, evaporated nearly to dryness, to dissipate any undecomposed potato oil, and then mixed with weak sulphuric acid in excess; a light oily liquid (terhydrated valerianic acid) separates, which by cautious rectification, yields at first water containing a little acid, and afterwards pure monohydrated valerianic acid, which is perfectly identical with that prepared from valerian root.
2. (Ph. D.) See Valerianate of Sodium. This is a most economical process.
Prop., &c. A limpid oily liquid, smelling strongly of valerian root; it has an acid taste and reaction, and leaves a sensation of sweetness and a white spot on the tongue; is inflammable; boils at 347°; is freely soluble in alcohol and ether; dissolves in 30 parts of water, and forms salts called valerianates, most of which have a sweetish taste, are soluble, and uncrystallisable; sp. gr. ·937; placed in contact with water, it absorbs a portion of it, and is converted into the terhydrated acid, with increase of sp. gr., and reduction of the boiling-point.
VALE′′RIC ACID. See Valerianic acid.