Webster's Dictionary, 1913

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Hydro-electric adjective [ 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.

Hydro-extractor noun [ Hydro- , 1 + extractor .] An apparatus for drying anything, as yarn, cloth, sugar, etc., by centrifugal force; a centrifugal.

Hydrocephalous adjective Having hydrocephalus. " Hydrocephalous offspring." G. Eliot.

Hydrocephalus noun [ New Latin , from Greek ... hydrocephalus; "y`dwr water + ... head.] (Medicine) 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.

Hydrochlorate noun (Chemistry) Same as Hydrochloride .

Hydrochloric adjective [ Hydro- , 2 + chloric : confer French hydrochlorique .] (Chemistry) Pertaining to, or compounded of, chlorine and hydrogen gas; as, hydrochloric acid; chlorhydric.

Hydrochloric acid (Chemistry) , 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 .

Hydrochloride noun (Chemistry) A compound of hydrochloric acid with a base; -- distinguished from a chloride , where only chlorine unites with the base.

Hydrocorallia noun plural [ New Latin See Hydra , and Coral .] (Zoology) 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 .

Hydrocyanate noun (Chemistry) See Hydrocyanide .

Hydrocyanic adjective [ Hydro- , 2 + anic : confer French hydrocyanique .] (Chemistry) Pertaining to, or derived from the combination of, hydrogen and cyanogen.

Hydrocyanic acid (Chemistry) , 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.

Hydrocyanide noun (Chemistry) A compound of hydrocyanic acid with a base; -- distinguished from a cyanide , in which only the cyanogen so combines.

Hydrodynamic, Hydrodynamical adjective [ Hydro- , 1 + dynamic , - ical : confer French 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.

Hydrodynamics noun [ Hydro- , 1 + dynamics : confer French 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 .

Hydrodynamometer noun [ Hydro- , 1 + dynamometer .] An instrument to measure the velocity of a liquid current by the force of its impact.

Hydroferricyanic noun [ Hydro- , 2 + ferricyanic .] (Chemistry) Pertaining to, or containing, or obtained from, hydrogen, ferric iron, and cyanogen; as, hydroferricyanic acid. See Ferricyanic .

Hydroferrocyanic adjective [ Hydro- , 2 + ferrocyanic .] (Chemistry) Pertaining to, or containing, or obtained from, hydrogen, ferrous iron, and cyanogen; as, hydroferrocyanic acid. See Ferrocyanic .

Hydrofluate noun (Chemistry) A supposed compound of hydrofluoris acid and a base; a fluoride. [ Archaic]

Hydrofluoric adjective [ Hydro- , 2 + fluoric .] (Chemistry) Pertaining to, or containing, hydrogen and fluorine; fluohydric; as, hydrofluoric acid.

Hydrofluoric acid (Chemistry) , 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.

Hydrofluosilicate noun (Chemistry) A salt of hydrofluosilic acid; a silicofluoride. See Silicofluoride .

Hydrofluosilicic adjective [ Hydro- , 2 + fluo rine + silicic .] (Chemistry) Pertaining to, or denoting, a compound consisting of a double fluoride of hydrogen and silicon; silicofluoric. See Silicofluoric .

Hydrogalvanic adjective [ Hydro- , 1 + galvanic .] Pertaining to, produced by, or consisting of, electricity evolved by the action or use of fluids; as, hydrogalvanic currents. [ R.]

Hydrogen noun [ Hydro- , 1 + -gen : confer French hydrogène . So called because water is generated by its combustion. See Hydra .] (Chemistry) 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, H 2 O 2 , 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, H 2 S, 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 .

Hydrogenate transitive verb [ imperfect & past participle Hydrogenated ; present participle & verbal noun Hydrogenating .] (Chemistry) To hydrogenize.

Hydrogenation noun (Chemistry) The act of combining with hydrogen, or the state of being so combined.

Hydrogenide noun (Chemistry) A binary compound containing hydrogen; a hydride. [ R.] See Hydride .

Hydrogenium noun [ New Latin See Hydrogen .] (Chemistry) Hydrogen; -- called also in view of its supposed metallic nature. Graham.

Hydrogenize transitive verb [ imperfect & past participle Hydrogenized ; present participle & verbal noun Hydrogenizing .] (Chemistry) To combine with hydrogen; to treat with, or subject to the action of, hydrogen; to reduce; -- contrasted with oxidize .

Hydrogenous adjective Of or pertaining to hydrogen; containing hydrogen.

Hydrognosy noun [ Hydro- , 1 + Greek ... knowledge.] A treatise upon, or a history and description of, the water of the earth.

Hydrogode noun [ Hydrog en + Greek ... way. path.] (Electricity) The negative pole or cathode. [ R.]

Hydrographer noun 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.

Hydrographic, Hydrographical adjective Of or relating to hydrography.

Hydrography noun [ Hydro- , 1 + -graphy : confer French 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.

Hydroguret noun [ From Hydrogen .] (Chemistry) A hydride. [ Obsolete]

Hydroid adjective [ Hydra + - oid .] (Zoology) Related to, or resembling, the hydra; of or pertaining to the Hydroidea. -- noun One of the Hydroideas.

Hydroidea noun plural [ New Latin See Hydra , and -oid .] (Zoology) An extensive order of Hydrozoa or Acalephæ. [ Written also Hydroida .]

» This order includes the hydras and the free-swimming hydromedusæ, 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 .

Hydrokinetic adjective [ 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.

Hydrological adjective Of or pertaining to hydrology.

Hydrologist noun One skilled in hydrology.

Hydrology noun [ Hydro- , 1 + -logy : confer French hydrologie .] The science of water, its properties, phenomena, and distribution over the earth's surface.

Hydrolysis noun [ Hydro- , 1 + -lysis .] (Chemistry) A chemical process involving the addition of the elements of water.

Hydrolytic adjective [ Hydro- , 1 + Greek ... to loose.] (Chemistry) 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.

Hydromagnesite (hī`dro*măg"ne*sīt) noun [ Hydro- , 1 + magnesite .] (Min.) A hydrous carbonate of magnesia occurring in white, earthy, amorphous masses.

Hydromancy noun [ Hydro- , 1 + -mancy : confer French hydromancie .] Divination by means of water, -- practiced by the ancients.

Hydromantic adjective [ Confer French hydromantique .] Of or pertaining to divination by water.

Hydromechanics noun [ Hydro- , 1 + mechanics .] That branch of physics which treats of the mechanics of liquids, or of their laws of equilibrium and of motion.

Hydromedusa noun ; plural Hydromedusæ . [ New Latin See Hydra , and Medusa .] (Zoology) Any medusa or jellyfish which is produced by budding from a hydroid. They are called also Craspedota , and naked-eyed medusæ .

» Such medusæ 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 medusæ 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 .

Hydromel noun [ Latin hydromel , hydromeli , Greek ...; ... water + ... honey: confer French hydromel .] A liquor consisting of honey diluted in water, and after fermentation called mead .

Hydromellonic adjective See Cyamellone .

Hydrometallurgical adjective 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 , adverb