Potassium dioxide

Potassium dioxide is the inorganic compound with the formula . It is a yellow paramagnetic solid that decomposes in moist air. It is a rare example of a stable salt of the superoxide ion. Potassium superoxide is used as a scrubber, dehumidifier and 2 generator in rebreathers, spacecraft, submarines and spacesuit life support systems.
==Production and reactions==
Potassium superoxide is produced by burning molten potassium in an atmosphere of oxygen.Harald Jakob, Stefan Leininger, Thomas Lehmann, Sylvia Jacobi, Sven Gutewort "Peroxo Compounds, Inorganic" Ullmann's Encyclopedia of Industrial Chemistry, 2007, Wiley-VCH, Weinheim. 
: + O2 → KO2
The salt consists of K+ and O2− ions, linked by ionic bonds. The O-O distance is 1.28 Å.
==Reactivity==
Hydrolysis gives oxygen gas and base:
:4 KO2 + 2 H2O → 4 KOH + 3 O2
Its degradation by carbon dioxide affords carbonates:
:4 KOH + 2 CO2 → 2 K2CO3 + 2 H2O
Combinations of these two reaction occur as well:
:4 KO2 + 2 CO2 → 2 K2CO3 + 3 O2
:4 KO2 + 4 CO2 + 2 H2O → 4 KHCO3 + 3 O2
Potassium superoxide finds only niche uses as a laboratory reagent. Because it reacts with water, KO2 is often studied in organic solvents. Since the salt is poorly soluble in nonpolar solvents, crown ethers are typically used. The tetraethylammonium salt is also known. Representative reactions of these salts involve the use of superoxide as a nucleophile, e.g., in the conversion of alkyl bromides to alcohols and acyl chlorides into diacyl peroxides.Roy A. Johnson, Javier Adrio, María Ribagorda "Potassium Superoxide" e-EROS Encyclopedia of Reagents for Organic Synthesis, 2001 John Wiley & Sons. 
==Applications==
The Russian Space Agency has had success using potassium superoxide in chemical oxygen generators for its spacesuits and Soyuz spacecraft. KO2 has also been utilized in canisters for rebreathers for fire fighting and mine rescue work, but had limited use in scuba rebreathers because of its dangerously explosive reaction with water. The theoretical capacity of KO2 is the absorption of 0.618 kg CO2 per kg of absorbent while 0.380 kg O2 are generated per kg of absorbent. For one KO2 molecule, it's one CO2 molecule but only 0.75 oxygen molecules. The human body though will produce less CO2 molecules than oxygen molecules needed because oxidation of food also needs oxygen to produce water and urea.
==Hazards==
Potassium superoxide is a potent oxidizer, and can produce explosive reactions when combined with a variety of substances, including water, acids, organics, or powdered graphite. Even dry superoxide can produce an impact-sensitive explosive compound when combined with organic oils such as kerosene. In 1999 at Oak Ridge National Laboratory, cleanup of potassium oxides from a NaK metal leak produced an impact-sensitive explosion while saturated with mineral oil. 
==References==
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