Chapter 119

Hy`dri*od"ic (?), a. [Hydr- + iodic: cf. F. hydriodique.] (Chem.) Pertaining to, or derived from, hydrogen and iodine; -- said of an acid produced by the combination of these elements.

Hydriodic acid (Chem.), a pungent, colorless gas, HI, usually prepared as a solution in water. It is strong reducing agent. Called also hydrogen iodide.

Hy*dri"o*dide (?), n. (Chem.) A compound of hydriodic acid with a base; -- distinguished from an iodide, in which only the iodine combines with the base.

{ Hy"dro- (?), Hy"dr-. } 1. A combining form from Gr. &?;, &?;, water (see Hydra).

2. (Chem.) A combining form of hydrogen, indicating hydrogen as an ingredient, as hydrochloric; or a reduction product obtained by hydrogen, as hydroquinone.

Hy`dro*ba*rom"e*ter (?), n. [Hydro- , 1 + barometer.] An instrument for determining the depth of the sea water by its pressure.

Hy`dro*bil`i*ru"bin (?), n. [Hydro- , 2 + bilirubin.] (Physiol. Chem.) A body formed from bilirubin, identical with urobilin.

||Hy`dro*bran`chi*a"ta (?), n. pl. [NL., fr. Gr. "y`dwr water + &?; ||gills.] (Zoˆl.) An extensive artificial division of gastropod ||mollusks, including those that breathe by gills, as contrasted with ||the Pulmonifera. -- Hy`dro*bran"chi*ate (#), a.

Hy`dro*bro"mate (?), n. (Chem.) Same as Hydrobromide.

Hy`dro*bro"mic (?), a. [Hydro-, 2 + bromic.] (Chem.) Composed of hydrogen and bromine; as, hydrobromic acid.

Hydrobromic acid (Chem.), a colorless, pungent, corrosive gas, HBr, usually collected as a solution in water. It resembles hydrochloric acid, but is weaker and less stable. Called also hydrogen bromide.

Hy`dro*bro"mide (?), n. (Chem.) A compound of hydrobromic acid with a base; -- distinguished from a bromide, in which only the bromine unites with the base.

Hy`dro*car"bon (?), n. [Hydro-, 2 + carbon.] (Chem.) A compound containing only hydrogen and carbon, as methane, benzene, etc.; also, by extension, any of their derivatives.

Hydrocarbon burner, furnace, stove, a burner, furnace, or stove with which liquid fuel, as petroleum, is used.

Hy`dro*car`bo*na"ceous (?), a. Of the nature, or containing, hydrocarbons.

Hy`dro*car"bon*ate (?), n. (a) (Old Chem.) A hydrocarbon. [Obs.] (b) (Chem.) A hydrous carbonate, as malachite.

Hy`dro*car`bo*sty"ril (?), n. [Hydro-, 2 + carbostyril.] (Chem.) A white, crystalline, nitrogenous hydrocarbon, C9H9NO, obtained from certain derivatives of cinnamic acid and closely related to quinoline and carbostyril.

Hy`dro*car"bu*ret (?), n. [Hydro- , 2 + carburet.] (Chem.) Carbureted hydrogen; also, a hydrocarbon. [Obs.]

Hy`dro*cau"lus (?), n.; pl. Hydrocauli (#). [NL., fr. Gr. "y`dwr water + &?; a stalk.] (Zoˆl.) The hollow stem of a hydroid, either simple or branched. See Illust. of Gymnoblastea and Hydroidea.

Hy`dro*cele (?), n. [L., fr. Gr. &?;; "y`dwr water + &?; tumor.] (Med.) A collection of serous fluid in the areolar texture of the scrotum or in the coverings, especially in the serous sac, investing the testicle or the spermatic cord; dropsy of the testicle.

Hy`dro*ce*phal"ic (?), a. Relating to, or connected with, hydrocephalus, or dropsy of the brain.

Hy`dro*ceph"a*loid (?), a. [Hydrocephalus + -oid.] (Med.) Resembling hydrocephalus.

Hydrocephaloid affection (Med.), the group of symptoms which follow exhausting diarrhea in young children, resembling those of acute hydrocephalus, or tubercular meningitis.

Hy`dro*ceph"a*lous (?), a. Having hydrocephalus. "Hydrocephalous offspring." G. Eliot.

Hy`dro*ceph"a*lus (?), n. [NL., fr. Gr. &?; hydrocephalus; "y`dwr water + &?; head.] (Med.) An accumulation of liquid within the cavity of the cranium, especially within the ventricles of the brain; dropsy of the brain. It is due usually to tubercular meningitis. When it occurs in infancy, it often enlarges the head enormously.

Hy`dro*chlo"rate (?), n. (Chem.) Same as Hydrochloride.

Hy`dro*chlo"ric (?), a. [Hydro-, 2 + chloric: cf. F. hydrochlorique.] (Chem.) Pertaining to, or compounded of, chlorine and hydrogen gas; as, hydrochloric acid; chlorhydric.

Hydrochloric acid (Chem.), hydrogen chloride; a colorless, corrosive gas, HCl, of pungent, suffocating odor. It is made in great quantities in the soda process, by the action of sulphuric acid on common salt. It has a great affinity for water, and the commercial article is a strong solution of the gas in water. It is a typical acid, and is an indispensable agent in commercial and general chemical work. Called also muriatic, ∧ chlorhydric, acid.

Hy`dro*chlo"ride (?), n. (Chem.) A compound of hydrochloric acid with a base; -- distinguished from a chloride, where only chlorine unites with the base.

||Hy`dro*co*ral"li*a (?), n. pl. [NL. See Hydra, and Coral.] (Zoˆl.) A ||division of Hydroidea, including those genera that secrete a stony ||coral, as Millepora and Stylaster. Two forms of zooids in life ||project from small pores in the coral and resemble those of other ||hydroids. See Millepora.

Hy`dro*cy"a*nate (?), n. (Chem.) See Hydrocyanide.

Hy`dro*cy*an"ic (?), a. [Hydro-, 2 + anic: cf. F. hydrocyanique.] (Chem.) Pertaining to, or derived from the combination of, hydrogen and cyanogen.

Hydrocyanic acid (Chem.), a colorless, mobile, volatile liquid, HCN, having a characteristic peach-blossom odor. It is one of the most deadly poisons. It is made by the action of sulphuric acid on yellow prussiate of potassium (potassium ferrocyanide), and chemically resembles hydrochloric and hydrobromic acids. Called also prussic acid, hydrogen cyanide, etc.

Hy`dro*cy"a*nide (?), n. (Chem.) A compound of hydrocyanic acid with a base; -- distinguished from a cyanide, in which only the cyanogen so combines.

{ Hy`dro*dy*nam"ic (?), Hy`dro*dy*nam"ic*al (?), } a. [Hydro-, 1 + dynamic, - ical: cf. F. hydrodynamique.] Pertaining to, or derived from, the dynamical action of water of a liquid; of or pertaining to water power.

Hydrodynamic friction, friction produced by the viscosity of a liquid in motion.

Hy`dro*dy*nam"ics (?), n. [Hydro- , 1 + dynamics: cf. F. hydrodynamique.] That branch of the science of mechanics which relates to fluids, or, as usually limited, which treats of the laws of motion and action of nonelastic fluids, whether as investigated mathematically, or by observation and experiment; the principles of dynamics, as applied to water and other fluids.

The word is sometimes used as a general term, including both hydrostatics and hydraulics, together with pneumatics and acoustics. See Hydraulics.

Hy`dro*dy`na*mom"e*ter (?), n. [Hydro-, 1 + dynamometer.] An instrument to measure the velocity of a liquid current by the force of its impact.

Hy`dro-e*lec"tric (?), a. [Hydro- , 1 + electric.] Pertaining to, employed in, or produced by, the evolution of electricity by means of a battery in which water or steam is used.

Hydro-electric machine (Physics), an apparatus invented by Sir William Armstrong of England for generating electricity by the escape of high-pressure steam from a series of jets connected with a strong boiler, in which the steam is produced.

Hy`dro-ex*tract"or (?), n. [Hydro- , 1 + extractor.] An apparatus for drying anything, as yarn, cloth, sugar, etc., by centrifugal force; a centrifugal.

Hy`dro*fer`ri*cy*an"ic (?), n. [Hydro-, 2 + ferricyanic.] (Chem.) Pertaining to, or containing, or obtained from, hydrogen, ferric iron, and cyanogen; as, hydroferricyanic acid. See Ferricyanic.

Hy`dro*fer`ro*cy*an"ic (?), a. [Hydro-, 2 + ferrocyanic.] (Chem.) Pertaining to, or containing, or obtained from, hydrogen, ferrous iron, and cyanogen; as, hydroferrocyanic acid. See Ferrocyanic.

Hy`dro*flu"ate (?), n. (Chem.) A supposed compound of hydrofluoris acid and a base; a fluoride. [Archaic]

Hy`dro*flu*or"ic (?), a. [Hydro- , 2 + fluoric.] (Chem.) Pertaining to, or containing, hydrogen and fluorine; fluohydric; as, hydrofluoric acid.

Hydrofluoric acid (Chem.), a colorless, mobile, volatile liquid, HF, very corrosive in its action, and having a strong, pungent, suffocating odor. It is produced by the action of sulphuric acid on fluorite, and is usually collected as a solution in water. It attacks all silicates, as glass or porcelain, is the agent employed in etching glass, and is preserved only in vessels of platinum, lead, caoutchouc, or gutta-percha.

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Hy`dro*flu`o*sil"i*cate (?), n. (Chem.) A salt of hydrofluosilic acid; a silicofluoride. See Silicofluoride.

Hy`dro*flu`o*si*lic"ic (?), a. [Hydro-, 2 + fluorine + silicic.] (Chem.) Pertaining to, or denoting, a compound consisting of a double fluoride of hydrogen and silicon; silicofluoric. See Silicofluoric.

Hy`dro*gal*van"ic (?), a. [Hydro- , 1 + galvanic.] Pertaining to, produced by, or consisting of, electricity evolved by the action or use of fluids; as, hydrogalvanic currents. [R.]

Hy"dro*gen (?), n. [Hydro-, 1 + -gen: cf. F. hydrogËne. So called because water is generated by its combustion. See Hydra.] (Chem.) A gaseous element, colorless, tasteless, and odorless, the lightest known substance, being fourteen and a half times lighter than air (hence its use in filling balloons), and over eleven thousand times lighter than water. It is very abundant, being an ingredient of water and of many other substances, especially those of animal or vegetable origin. It may by produced in many ways, but is chiefly obtained by the action of acids (as sulphuric) on metals, as zinc, iron, etc. It is very inflammable, and is an ingredient of coal gas and water gas. It is standard of chemical equivalents or combining weights, and also of valence, being the typical monad. Symbol H. Atomic weight 1.

Although a gas, hydrogen is chemically similar to the metals in its nature, having the properties of a weak base. It is, in all acids, the base which is replaced by metals and basic radicals to form salts. Like all other gases, it is condensed by great cold and pressure to a liquid which freezes and solidifies by its own evaporation. It is absorbed in large quantities by certain metals (esp. palladium), forming alloy-like compounds; hence, in view of quasi-metallic nature, it is sometimes called hydrogenium. It is the typical reducing agent, as opposed to oxidizers, as oxygen, chlorine, etc.

Bicarbureted hydrogen, an old name for ethylene. -- Carbureted hydrogen gas. See under Carbureted. -- Hydrogen dioxide, a thick, colorless liquid, H2O2, resembling water, but having a bitter, sour taste, produced by the action of acids on barium peroxide. It decomposes into water and oxygen, and is manufactured in large quantities for an oxidizing and bleaching agent. Called also oxygenated water. -- Hydrogen oxide, a chemical name for water, H&?;O. -- Hydrogen sulphide, a colorless inflammable gas, H2S, having the characteristic odor of bad eggs, and found in many mineral springs. It is produced by the action of acids on metallic sulphides, and is an important chemical reagent. Called also sulphureted hydrogen.

Hy"dro*gen*ate (?), v. t. [imp. & p. p. Hydrogenated (?); p. pr. & vb. n. Hydrogenating (?).] (Chem.) To hydrogenize.

Hy`dro*gen*a"tion (?), n. (Chem.) The act of combining with hydrogen, or the state of being so combined.

Hy"dro*gen*ide (?), n. (Chem.) A binary compound containing hydrogen; a hydride. [R.] See Hydride.

Hy`dro*ge"ni*um (?), n. [NL. See Hydrogen.] (Chem.) Hydrogen; -- called also in view of its supposed metallic nature. Graham.

Hy"dro*gen*ize (?), v. t. [imp. & p. p. Hydrogenized (?); p. pr. & vb. n. Hydrogenizing (?).] (Chem.) To combine with hydrogen; to treat with, or subject to the action of, hydrogen; to reduce; -- contrasted with oxidize.

Hy*drog"e*nous (?), a. Of or pertaining to hydrogen; containing hydrogen.

Hy*drog"no*sy (?), n. [Hydro-, 1 + Gr. &?; knowledge.] A treatise upon, or a history and description of, the water of the earth.

Hy"drog*ode (?), n. [Hydrogen + Gr. &?; way. path.] (Elec.) The negative pole or cathode. [R.]

Hy*drog"ra*pher (?), n. One skilled in the hydrography; one who surveys, or draws maps or charts of, the sea, lakes, or other waters, with the adjacent shores; one who describes the sea or other waters. Boyle.

{ Hy`dro*graph"ic (?), Hy`dro*graph"ic*al (?), } a. Of or relating to hydrography.

Hy*drog"ra*phy (?), n. [Hydro-, 1 + -graphy: cf. F. hydrographie.] 1. The art of measuring and describing the sea, lakes, rivers, and other waters, with their phenomena.

2. That branch of surveying which embraces the determination of the contour of the bottom of a harbor or other sheet of water, the depth of soundings, the position of channels and shoals, with the construction of charts exhibiting these particulars.

Hy*drog"u*ret (?), n. [From Hydrogen.] (Chem.) A hydride. [Obs.]

Hy"droid (?), a. [Hydra + - oid.] (Zoˆl.) Related to, or resembling, the hydra; of or pertaining to the Hydroidea. -- n. One of the Hydroideas.

||Hy*droi"de*a, n. pl. [NL. See Hydra, and -oid.] (Zoˆl.) An extensive ||order of Hydrozoa or AcalephÊ. [Written also Hydroida.]

This order includes the hydras and the free-swimming hydromedusÊ, together with a great variety of marine attached hydroids, many of which grow up into large, elegantly branched forms, consisting of a vast number of zooids (hydranths, gonophores, etc.), united by hollow stems. All the zooids of a colony are produced from one primary zooid, by successive buddings. The Siphonophora have also been included in this order by some writers. See Gymnoblastea, Hydromedusa, Gonosome, Gonotheca.

Hy`dro*ki*net"ic (?), a. [Hydro- , 1 + kinetic.] Of or pertaining to the motions of fluids, or the forces which produce or affect such motions; -- opposed to hydrostatic. Sir W. Thomson.

Hy`dro*log"ic*al (?), a. Of or pertaining to hydrology.

Hy*drol"o*gist (?), n. One skilled in hydrology.

Hy*drol"o*gy (?), n. [Hydro-, 1 + -logy: cf. F. hydrologie.] The science of water, its properties, phenomena, and distribution over the earth's surface.

Hy`dro*lyt"ic (?), a. [Hydro-, 1 + Gr. &?; to loose.] (Chem.) Tending to remove or separate water; eliminating water.

Hydrolytic agents, such as sulphuric acid or caustic alkali.

Encyc. Brit.

Hydrolytic ferment (Physiol. Chem.), a ferment, enzyme, or chemical ferment, which acts only in the presence of water, and which causes the substance acted upon to take up a molecule of water. Thus, diastase of malt, ptyalin of saliva, and boiling dilute sulphuric acid all convert starch by hydration into dextrin and sugar. Nearly all of the digestive ferments are hydrolytic in their action.

Hy`dro*mag"ne*site (h`dr*mg"n*st), n. [Hydro-, 1 + magnesite.] (Min.) A hydrous carbonate of magnesia occurring in white, earthy, amorphous masses.

Hy"dro*man`cy (?), n. [Hydro-, 1 + -mancy: cf. F. hydromancie.] Divination by means of water, -- practiced by the ancients.

Hy`dro*man"tic (?), a. [Cf. F. hydromantique.] Of or pertaining to divination by water.

Hy`dro*me*chan"ics (?), n. [Hydro- , 1 + mechanics.] That branch of physics which treats of the mechanics of liquids, or of their laws of equilibrium and of motion.

||Hy`dro*me*du"sa (?), n.; pl. HydromedusÊ (#). [NL. See Hydra, and ||Medusa.] (Zoˆl.) Any medusa or jellyfish which is produced by budding ||from a hydroid. They are called also Craspedota, and naked-eyed ||medusÊ.

Such medusÊ are the reproductive zooids or gonophores, either male or female, of the hydroid from which they arise, whether they become free or remain attached to the hydroid colony. They in turn produce the eggs from which the hydroids are developed. The name is also applied to other similar medusÊ which are not known to bud from a hydroid colony, and even to some which are known to develop directly from the eggs, but which in structure agree essentially with those produced from hydroids. See Hydroidea, and Gymnoblastea.

Hy"dro*mel (?), n. [L. hydromel, hydromeli, Gr. &?;; &?; water + &?; honey: cf. F. hydromel.] A liquor consisting of honey diluted in water, and after fermentation called mead.

Hy`dro*mel*lon"ic (?), a. See Cyamellone.

Hy`dro*met`al*lur"gic*al (?), a. Of or pertaining to hydrometallurgy; involving the use of liquid reagents in the treatment or reduction of ores. -- Hy`dro*met`al*lur"gic*al*ly, adv.

Hy`dro*met"al*lur`gy (?), n. [Hydro- , 1 + metallurgy.] The art or process of assaying or reducing ores by means of liquid reagents.

Hy`dro*me"te*or (?), n. [Hydro-, 1 + meteor.] A meteor or atmospheric phenomenon dependent upon the vapor of water; -- in the pl., a general term for the whole aqueous phenomena of the atmosphere, as rain, snow, hail, etc. Nichol.

Hy`dro*me`te*or`o*log"ic*al (?), a. Of or pertaining to hydrometeorology, or to rain, clouds, storms, etc.

Hy`dro*me`te*or*ol"o*gy (?), n. [Hydro-, 1 + meteorology.] That branch of meteorology which relates to, or treats of, water in the atmosphere, or its phenomena, as rain, clouds, snow, hail, storms, etc.

Hy*drom"e*ter (?), n. [Hydro-, 1 + -meter: cf. F. hydromËtre.] 1. (Physics) An instrument for determining the specific gravities of liquids, and thence the strength spirituous liquors, saline solutions, etc.

It is usually made of glass with a graduated stem, and indicates the specific gravity of a liquid by the depth to which it sinks in it, the zero of the scale marking the depth to which it sinks in pure water. Extra weights are sometimes used to adapt the scale to liquids of different densities.

2. An instrument, variously constructed, used for measuring the velocity or discharge of water, as in rivers, from reservoirs, etc., and called by various specific names according to its construction or use, as tachometer, rheometer, hydrometer, pendulum, etc.; a current gauge.

{ Hy`dro*met"ric (?), Hy`dro*met"ric*al (?), } a. [Cf. F. hydromËtrique.] 1. Of or pertaining to an hydrometer, or to the determination of the specific gravity of fluids.

2. Of or pertaining to measurement of the velocity, discharge, etc., of running water.

3. Made by means of an hydrometer; as, hydrometric observations.

Hydrometric pendulum, a species of hydrometer consisting of a hollow ball of ivory or metal suspended by a treated from the center of a graduated quadrant, and held in a stream to measure the velocity of the water by the inclination given to the thread; a kind of current gauge.

Hy`dro*met"ro*graph (?), n. [Hydro- , 1 + Gr. &?; measure + -graph.] An instrument for determining and recording the quantity of water discharged from a pipe, orifice, etc., in a given time.

Hy*drom"e*try (?), n. [Cf. F. hydromËtrique.] 1. The art of determining the specific gravity of liquids, and thence the strength of spirituous liquors, saline solutions, etc.

2. The art or operation of measuring the velocity or discharge of running water, as in rivers, etc.

Hy`dro*mi"ca (?), n. [Hydro-, 1 + mica.] (Min.) A variety of potash mica containing water. It is less elastic than ordinary muscovite.

Hydromica schist (Min.), a mica schist characterized by the presence of hydromica. It often has a silky luster and almost soapy feel.

||Hy`dro*ne*phro"sis (?), n. [NL., Gr. "y`dwr water + &?; a kidney.] ||(Med.) An accumulation of urine in the pelvis of the kidney, ||occasioned by obstruction in the urinary passages.

Hy"dro*path (?), n. [Cf. F. hydropathe.] A hydropathist.

{ Hy`dro*path"ic (?), Hy`dro*path"ic*al (?), } a. Of or pertaining to hydropathy.

Hy*drop"a*thist (?), n. One who practices hydropathy; a water-cure doctor.

Hy*drop"a*thy (?), n. [Hydro-, 1 + Gr. &?;, &?;, to suffer.] The water cure; a mode of treating diseases by the copious and frequent use of pure water, both internally and externally.

||Hy`dro*per`i*to*ne"um (?), n. [NL. See Hydro-, and Peritoneum.] ||(Med.) Same as Ascites.

Hy"dro*phane (?), n. [Hydro-, 1 + Gr. &?; to show, appear: cf. F. hydrophane.] (Min.) A semitranslucent variety of opal that becomes translucent or transparent on immersion in water.

Hy*droph"a*nous (?), a. (Min.) Made transparent by immersion in water.

Hy"dro*phid (?), n. [Hydro-, 1 + Gr. &?; a small serpent.] (Zoˆl.) Any sea snake of the genus Hydrophys and allied genera. These snakes are venomous, live upon fishes, and have a flattened tail for swimming.

Hy`dro*phlo"rone (?), n. [Hydro- , 2 + phlorone.] (Chem.) A white, crystalline benzene derivative, C8H10O2, obtained by the reduction of phlorone.

Hy`dro*pho"bi*a (?), n. [L., fr. Gr. &?;; "y`dwr water + &?; fear: cf. F. hydrophobie.] (Med.) (a) An abnormal dread of water, said to be a symptom of canine madness; hence: (b) The disease caused by a bite form, or inoculation with the saliva of, a rabid creature, of which the chief symptoms are, a sense of dryness and construction in the throat, causing difficulty in deglutition, and a marked heightening of reflex excitability, producing convulsions whenever the patient attempts to swallow, or is disturbed in any way, as by the sight or sound of water; rabies; canine madness. [Written also hydrophoby.]

Hy`dro*phob"ic (?), a. [L. hydrophobicus, Gr. &?;: cf. F. hydrophobique.] Of or pertaining to hydrophobia; producing or caused by rabies; as, hydrophobic symptoms; the hydrophobic poison.

Hy"dro*pho`by (?), n. See Hydrophobia.

||Hy*droph"o*ra (?), n. pl. [NL., fr. E. hydra + Gr. &?; to bear.] ||(Zoˆl.) The Hydroidea.

Hy"dro*phore (?), n. [Gr. "y`dwr water + &?; to bear.] An instrument used for the purpose of obtaining specimens of water from any desired depth, as in a river, a lake, or the ocean.

||Hy`dro*phyl"li*um (?), n.; pl. L. Hydrophyllia (#), E. Hydrophylliums ||(#). [NL., fr. Gr. "y`dwr water + &?; a leaf.] (Zoˆl.) One of the ||flat, leaflike, protective zooids, covering other zooids of certain ||Siphonophora.

Hy"dro*phyte (?), n. [Gr. &?; + &?; plant: cf. F. hydrophyte.] An aquatic plant; an alga.

Hy*droph`y*tol"o*gy (?), n. [Hydro- + phyte + -logy.] The branch of botany which treats of water plants.

{ Hy*drop"ic (?), Hy*drop"ic*al (?), } a. [L. hydropicus, Gr. &?;: cf. F. hydropique. See Dropsy.] Dropsical, or resembling dropsy.

Every lust is a kind of hydropic distemper, and the more we drink the more we shall thirst.

Tillotson.

Hy*drop"ic*al*ly, adv. In a hydropical manner.

||Hy"dro*pi`per (?), n. [NL., fr. Gr. "y`dwr water + L. piper a ||pepper.] (Bot.) A species (Polygonum Hydropiper) of knotweed with ||acrid foliage; water pepper; smartweed.

Hy`dro*pneu*mat"ic (?), a. [Hydro- , 1 + pneumatic: cf. F. hydropneumatique.] Pertaining to, or depending upon, both liquid and gaseous substances; as, hydropneumatic apparatus for collecting gases over water or other liquids.

Hy"drop`sy (?), n. Same as Dropsy.

Hy"dro*pult (?), n. [Hydro-, 1 + Gr. &?; to hurl.] A machine for throwing water by hand power, as a garden engine, a fire extinguisher, etc.

Hy`dro*qui"none (?), n. [Hydro-, 2 + quinone.] (Chem.) A white crystalline substance, C6H4(OH)2, obtained by the reduction of quinone. It is a diacid phenol, resembling, and metameric with, pyrocatechin and resorcin. Called also dihydroxy benzene.

||Hy`dro*rhi"za (?), n.; pl. L. HydrorhizÊ (#), E. Hydrorhizas (#). ||[NL., fr. E. hydra + Gr. &?; a root.] (Zoˆl.) The rootstock or ||decumbent stem by which a hydroid is attached to other objects. See ||Illust. under Hydroidea.

Hy"dro*salt` (?), n. [Hydro-, 1 + salt.] (Chem.) (a) A salt supposed to be formed by a hydracid and a base. (b) An acid salt. [R.] (c) A hydrous salt; a salt combined with water of hydration or crystallization.

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Hy"dro*scope (?), n. [Hydro-, 1 + -scope.] 1. An instrument designed to mark the presence of water, especially in air. Weale.

2. A kind of water clock, used anciently for measuring time, the water tricking from an orifice at the end of a graduated tube.

{ Hy"dro*some (?), ||Hy`dro*so"ma (?) }, n. [NL. hydrosoma. See Hydra, and -some body.] (Zoˆl.) All the zooids of a hydroid colony collectively, including the nutritive and reproductive zooids, and often other kinds.