Barium peroxide

Barium peroxide is an inorganic compound with the formula BaO₂. This white solid (gray when impure) is one of the most common inorganic peroxides, and it was the first peroxide compound discovered. Being an oxidizer and giving a vivid green colour upon ignition (as do all barium compounds), it finds some use in fireworks; historically, it was also used as a precursor for hydrogen peroxide.^[3]

Barium peroxide

Barium cations Ba2+   Peroxide anions O2−2
Names
IUPAC name barium peroxide
Other names Barium binoxide, Barium dioxide
Identifiers
CAS Number	1304-29-6 Y
3D model (JSmol)	Interactive image
ChemSpider	14090 Y
ECHA InfoCard	100.013.754
EC Number	215-128-4
PubChem CID	14773
RTECS number	CR0175000
UNII	T892KY013Y Y
UN number	1449
CompTox Dashboard (EPA)	DTXSID9051294
InChI InChI=1S/Ba.O2/c;1-2/q+2;-2 Y Key: ZJRXSAYFZMGQFP-UHFFFAOYSA-N Y InChI=1/Ba.O2/c;1-2/q+2;-2 Key: ZJRXSAYFZMGQFP-UHFFFAOYAZ
SMILES [Ba+2].[O-][O-]
Properties
Chemical formula	BaO2
Molar mass	169.33 g/mol (anhydrous) 313.45 g/mol (octahydrate)
Appearance	Grey-white crystalline solid (anhydrous) Colorless solid (octahydrate)
Odor	Odorless
Density	5.68 g/cm3 (anhydrous) 2.292 g/cm3 (octahydrate)
Melting point	450 °C (842 °F; 723 K)
Boiling point	800 °C (1,470 °F; 1,070 K) (decomposes to BaO & O2.[1])
Solubility in water	0.091 g/(100 mL) (20 °C) (anhydrous) 0.168 g/cm3 (octahydrate)
Solubility	dissolves with decomposition in acid
Magnetic susceptibility (χ)	−40.6·10−6 cm3/mol
Structure
Crystal structure	Tetragonal[2]
Space group	D174h, I4/mmm, tI6
Coordination geometry	6
Hazards
GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H272, H302, H332
Precautionary statements	P210, P220, P221, P261, P264, P270, P271, P280, P301+P312, P304+P312, P304+P340, P312, P330, P370+P378, P501
NFPA 704 (fire diamond)	3 0 2 OX
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Structure

Barium peroxide consists of barium cations Ba²⁺ and peroxide anions O2−2. The solid is isomorphous to calcium carbide, CaC₂.

Preparation and use

Barium peroxide arises by the reversible reaction of O₂ with barium oxide. The peroxide forms around 500 °C and oxygen is released above 820 °C.^[1]

2 BaO + O₂ ⇌ 2 BaO₂

This reaction is the basis for the now-obsolete Brin process for separating oxygen from the atmosphere. Other oxides, e.g. Na₂O and SrO, behave similarly.^[4]

In another obsolete application, barium peroxide was once used to produce hydrogen peroxide via its reaction with sulfuric acid:^[3]

BaO₂ + H₂SO₄ → H₂O₂ + BaSO₄

The insoluble barium sulfate is filtered from the mixture.