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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.
Hydrofluosilicate
(Hy`dro*flu`o*sil"i*cate) n. (Chem.) A salt of hydrofluosilic acid; a silicofluoride. See
Silicofluoride.
Hydrofluosilicic
(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.
Hydrogalvanic
(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.]
Hydrogen
(Hy"dro*gen) n. [Hydro-, 1 + -gen: cf. F. hydrogène. 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 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 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, HO. — 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.
Hydrogenate
(Hy"dro*gen*ate) v. t. [imp. & p. p. Hydrogenated ; p. pr. & vb. n. Hydrogenating ]
(Chem.) To hydrogenize.
Hydrogenation
(Hy`dro*gen*a"tion) n. (Chem.) The act of combining with hydrogen, or the state of
being so combined.
Hydrogenide
(Hy"dro*gen*ide) n. (Chem.) A binary compound containing hydrogen; a hydride. [R.]
See Hydride.
Hydrogenium
(Hy`dro*ge"ni*um) n. [NL. See Hydrogen.] (Chem.) Hydrogen; — called also in view of
its supposed metallic nature. Graham.
Hydrogenize
(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.
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