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An aquatic mite of the genus Hydrachna. The hydrachids, while young, are parasitic on fresh-water mussels.

An acid containing hydrogen; -- sometimes applied to distinguish acids like hydrochloric, hydrofluoric, and the like, which contain no oxygen, from the oxygen acids or oxacids. See Acid.

Pertaining to, or designating, an isomeric variety of lastic acid that breaks down into acrylic acid and water.

Any species or marine hydroids, of the genus Hydractinia and allied genera. These hydroids form, by their rootstalks, a firm, chitinous coating on shells and stones, and esp. on spiral shells occupied by hermit crabs. See Illust. of Athecata.

An abnormally watery state of the blood; anæmia.

A hydragogue medicine, usually a cathartic or diuretic.

One of a group of crystalline bodies produced by the action of ammonia on certain aldehydes.

l, organic bases, usually produced as thick viscous liquids by the action of ammonia on ethylene oxide. They have the properties both of alcohol and amines.

A genus of shrubby plants bearing opposite leaves and large heads of showy flowers, white, or of various colors. H. hortensis, the common garden species, is a native of China or Japan.

A discharge pipe with a valve and spout at which water may be drawn from the mains of waterworks; a water plug.

One of the nutritive zooids of a hydroid colony. Also applied to the proboscis or manubrium of a hydroid medusa. See Illust. of Hydroidea.

A compound of the bichloride of mercury with another chloride. [Obs.]

Of or pertaining to mercury; containing, or impregnated with, mercury. [R.]

A diseased condition produced by poisoning with hydrargyrum, or mercury; mercurialism.

Quicksilver; mercury.

An effusion of watery liquid into the cavity of a joint.

An alkaloid, found in the rootstock of the golden seal (Hydrastis Canadensis), and extracted as a bitter, white, crystalline substance. It is used as a tonic and febrifuge.

A substance which does not contain water as such, but has its constituents (hydrogen, oxygen, hydroxyl) so arranged that water may be eliminated; hence, a derivative of, or compound with, hydroxyl; hydroxide; as, ethyl hydrate, or common alcohol; calcium hydrate, or slaked lime.

Formed into a hydrate; combined with water.

The act of becoming, or state of being, a hydrate. Water of hydration (Chem.), water chemically combined with some substance to form a hydrate; -- distinguished from water of crystallization.