Barium oxide, also known as baria, is a white hygroscopic non-flammable compound with the formula BaO. It has a cubic structure and is used in cathode-ray tubes, crown glass, and catalysts. It is harmful to human skin and if swallowed in large quantity causes irritation. Excessive quantities of barium oxide may lead to death.
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 peroxideion ([O−O]2−, or O2−2) — with the same charge of O2−, and therefore keeping the electrochemical balance with the most stable Ba2+. Using the Kröger-Vink notation,
½O2(g) + O2– O ⇌ [O 2]2– O
where J O 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:
Barium oxide peroxidation from oxygen uptake, adapted from Middleburgh et al, 2012.
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).[4] 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.[5]
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.
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.[8]
See also
Barium– chemical element with symbol Ba and atomic number 56Pages displaying wikidata descriptions as a fallback
References
1 2 Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. ISBN978-0-618-94690-7.
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