Barium oxide

Uses

Barium oxide is used as a coating for hot cathodes, for example, those in cathode-ray tubes. It replaced lead(II) oxide in the production of certain kinds of glass such as optical crown glass. While lead oxide raised the refractive index, it also raised the dispersive power, 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.

It is most known for its use in the Brin process, named after its inventors, a reaction that was used as a large scale method to produce oxygen before air separation became the dominant method in the beginning of the 20th century, as BaO can be a source of pure oxygen through heat fluctuation.

BaO(s) + ½O2(g) ⇌ BaO2(s)

It oxidises to BaO2 by formation of a peroxide ion (, or ) — with the same charge of , and therefore keeping the electrochemical balance with the most stable . Using the Kröger-Vink notation,

½(g) + O ⇌ [O]

where J is the species J in the oxygen position within the rock-salt lattice. The complete peroxidation of BaO to BaO2 occurs at moderate temperatures by oxygen uptake within the BaO rock-salt lattice:

Calculations using Density Functional Theory (DFT) suggest that the oxygen incorporation reaction is exothermic, and that the most energetically favoured occupation site is indeed the peroxide ion at the oxide lattice — other than interstitial positions, for instance. However, the increased entropy of the system is what leads BaO2 to decompose to BaO and release O2 between 800 and 1100 K (520 and 820 °C). The reaction was used as a large scale method to produce oxygen before air separation became the dominant method in the beginning of the 20th century. The method was named the Brin process, after its inventors.

Preparation

Barium oxide from metallic barium readily forms from its exothermic oxidation with dioxygen in air:

2 Ba(s) + O2(g) → 2 BaO(s).

It's most commonly made by heating barium carbonate at temperatures of 1000–1450 °C.

BaCO3(s) → BaO(s) + CO2(g)

Likewise, it is often formed through the thermal decomposition of other barium salts, like barium nitrate.

Safety issues

Barium oxide is an irritant. If it contacts the skin or the eyes or is inhaled it causes pain and redness. However, it is more dangerous when ingested. It can cause nausea and diarrhea, muscle paralysis, cardiac arrhythmia, and can cause death. If ingested, medical attention should be sought immediately.

Barium oxide should not be released environmentally; it is harmful to aquatic organisms.

References

References

1. Zumdahl, Steven S.. (2009). "Chemical Principles 6th Ed.". Houghton Mifflin Company.
2. (2007). "Barium Oxide (chemical compound)".
3. (1980-07-01). "United States Patent 4210764".
4. Middleburgh, Simon C.. (2013). "Accommodation of Excess Oxygen in Group II Monoxides". Journal of the American Ceramic Society.
5. (2009). "The Origin of the Brin Process for the Manufacture of Oxygen". Journal of Chemical Education.
6. (2007-01-26). "Compounds of barium: barium (II) oxide". The University of Sheffield.
7. Pradyot Patnaik. ''Handbook of Inorganic Chemicals''. McGraw-Hill, 2002, {{ISBN. 0-07-049439-8
8. (October 1999). "Barium Oxide (ICSC)". IPCS.