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sulfide

(Encyclopedia)sulfide, chemical compound containing sulfur and one other element or sulfur and a radical. Sulfides may be salts or esters of hydrogen sulfide, H2S, or may be formed directly, e.g., by heating a meta...

ultramarine

(Encyclopedia)ultramarine, blue pigment used chiefly as a coloring material and as a bluing agent. A double silicate of sodium and aluminum with some sulfur, it is prepared commercially from kaolin, sulfur, soda as...

vulcanization

(Encyclopedia)vulcanization vŭlˌkənəzāˈshən [key], treatment of rubber to give it certain qualities, e.g., strength, elasticity, and resistance to solvents, and to render it impervious to moderate heat and c...

S

(Encyclopedia)S, 19th letter of the alphabet, representing the common sibilant, voiceless in spur, voiced in rose. Its Greek equivalent is sigma. In former times the nonterminal s was written or printed much like a...

cinnabar

(Encyclopedia)cinnabar sĭnˈəbär [key], mineral, the sulfide of mercury, HgS. Deep red in color, it is used as a pigment (see vermilion), but principally it is a source of the metal mercury. It is mined in Spain...

mixture

(Encyclopedia)mixture, in chemistry, a physical combination of two or more pure substances (i.e., elements or compounds). A mixture is distinguished from a compound, which is formed by the chemical combination of t...

acid rain

(Encyclopedia)acid rain or acid deposition, form of precipitation (rain, snow, sleet, or hail) containing high levels of sulfuric or nitric acids (pH below 5.5–5.6). Produced when sulfur dioxide and various nitro...

Volcano Islands

(Encyclopedia)Volcano Islands, Jap. Kazan-retto, island group, c.11 sq mi (30 sq km), W Pacific. The group consists of three islands, of which Iwo Jima (Iwo To) is the most important. The highest peak (3,181 ft/970...

nonmetal

(Encyclopedia)nonmetal, chemical element possessing certain properties by which it is distinguished from a metal. In general, this distinction is drawn on the basis that a nonmetal tends to accept electrons and for...

autotroph

(Encyclopedia)autotroph ôtˈətrōfˌ [key], in biology, an organism capable of synthesizing its own organic substances from inorganic compounds. Autotrophs produce their own sugars, lipids, and amino acids using ...