Barium oxide

Physical properties

Barium Oxide is a white, hygroscopic formed by the burning of Ba metal in oxygen or the decomposition of the carbonate salt:
2Ba＋ O2→2BaO
BaCO3→BaO＋ CO2
It transforms into the hydroxide on contact with water.
BaO＋H2O→Ba(OH)2
It is soluble in ethanol, dilute acids and alkalis but insoluble in acetone and liquid ammonia.
The monoxide is formed when the metal burns in air, but is usually prepared by the ignition of the nitrate, oxygen and oxides of nitrogen being liberated. It can also be obtained by the ignition of an intimate mixture of the carbonate and carbon, and in small quantities by the ignition of the iodate.

Uses

Barium oxide is used as a coating for “hot cathodes” in a variety of electronic devices such as TV’s and lamps. It replaced lead oxide in the production of certain kinds of glass. While lead oxide raised the refractive index of the glass, it also raised the dispersion, i.e refraction of various colors of light resulting in distortion of images which barium oxide does not alter. Barium oxide also has use as an ethoxylation catalyst in the reaction of ethylene oxide and alcohols which takes place between 150 and 200°C.
The thermionic emission from thin evaporated films of barium oxide has been studied extensively. Thin barium oxide films have a good emission following evaporation. The emission improves a little during heat treatment, and is then similar to that from a sprayed cathode coating of barium oxide.

Definition

barium oxide: A white or yellowishsolid, BaO, obtained by heating bariumin oxygen or by the thermal decompositionof barium carbonate ornitrate; cubic; r.d. 5.72; m.p. 1923°C;b.p. 2000°C. When barium oxide isheated in oxygen the peroxide, BaO₂,is formed in a reversible reactionthat was once used as a method forobtaining oxygen (the Brin process).Barium oxide is now used in themanufacture of lubricating-oil additives.

Preparation

Barium oxide is made by heating barium carbonate with coke, carbon black or tar:
BaCO₃ + C→ BaO + 2CO

It may be also prepared by thermal decomposition of barium nitrate.

General Description

A white to yellow powder. May be toxic by ingestion. Irritates skin, eyes and mucous membranes. Used as a drying agent for gasoline and solvents.

Air & Water Reactions

Hygroscopic. Reacts readily and exothermically with water to form a solution of corrosive barium hydroxide [Merck 11th ed. 1989].

Reactivity Profile

BARIUM OXIDE reacts as a strong base. Combines exothermically with all categories of acids. Reacts with carbon dioxide to form barium carbonate [Merck 11th ed. 1989]. Ignites hydroxylamine on contact [Mellor 8:291 1946-47]. Mixtures with mercurous or nickel oxide react vigorously with hydrogen sulfide in air. Explosions may result [Mellor 10:140 1946-47]. Can react, particularly in the presence of moisture, with aluminum and zinc)to form oxides or hydroxides of the metal and generate gaseous hydrogen. May initiate polymerization reactions in polymerizable organic compounds, especially epoxides. May generate flammable and/or toxic gases with ammonium salts, nitrides, halogenated organics, peroxides, and hydroperoxides.

Hazard

Toxic by ingestion. See barium.

Health Hazard

TOXIC; inhalation, ingestion or contact (skin, eyes) with vapors, dusts or substance may cause severe injury, burns or death. Reaction with water or moist air will release toxic, corrosive or flammable gases. Reaction with water may generate much heat that will increase the concentration of fumes in the air. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause pollution.

Fire Hazard

Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Vapors may accumulate in confined areas (basement, tanks, hopper/tank cars etc.). Substance will react with water (some violently), releasing corrosive and/or toxic gases and runoff. Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated or if contaminated with water.

Safety Profile

A poison via subcutaneous route. See also BARIUM COMPOUNDS (soluble). Combustible by spontaneous chemical reaction; produces heat on contact with water or steam. Reacts with H2O, Ba(OH)2. Incompatible with H2S, hydroxylamine, N2O4, triuranium octaoxide, so3.

Potential Exposure

It is used to dry gases and solvents and in producing detergents for lubricating oils.

Shipping

UN1884 Barium oxide, Hazard Class: 6.1; Labels: 6.1—Poisonous materials.

Incompatibilities

Reacts with water, forming the strong base, barium hydroxide. Keep away from acids, hydrogen sulfide, carbon dioxide; hydroxylamine, nitrogen tetroxide; sulfur trioxide; since violent reactions occur. Reacts with triuranium. Never pour water into this chemical.