The potassium oxide, also called dipotassium oxide is an ionic salt and potassium oxygen with the formula K 2 O. Its structure is presented in Figure 1 (EMBL-EBI, 2016).
K 2 O is the simplest potassium oxide, it is a highly reactive compound and rarely found. Some commercial materials, such as fertilizers and cements, are tested assuming the percentage of composition that would be equivalent to the mixture of chemical compounds K 2 O.
Figure 1: structure of potassium oxide.
Potassium oxide is produced from potassium hydroxide (caustic potash) and metallic potassium at 450 ° C producing molecular hydrogen (POTASSIUM OXIDE K2O, SF) according to the equation:
2K + 2KOH * 2K 2 O + H 2 (450 ° C).
It is also obtained by reducing potassium peroxide according to the reaction:
2K 2 O 2 → K 2 O + O 2 (530 ° C).
Another method of obtaining potassium oxide is by heating potassium carbonate at high temperatures as indicated by the following reaction:
K 2 CO 3 ⇌ K 2 O + CO 2 (T> 1200 ° C).
However, the main way to obtain potassium oxide is by heating the potassium nitrate, obtaining molecular nitrogen as indicated by the following reaction:
2KNO 3 + 10K → 6K 2 O + N 2
Physical and chemical properties
Potassium oxide are yellowish tetrahedral crystals without a characteristic aroma (National Center for Biotechnology Information., 2017). Its appearance is shown in figure 2 (american elements, SF).
Figure 2: appearance of potassium oxide.
The compound has a molecular weight of 94.2 g / mol and a density of 2.13 g / ml at 24 ° C. It has a melting point of 740 ° C although it begins to decompose at 300 ° C (Royal Society of Chemistry, 2015).
The compound is heat resistant and soluble in ethanol and ether. K 2 O crystallizes in the antifluorite structure. For this reason, the positions of the anions and cations are reversed relative to their positions in CaF 2, with potassium ions coordinated at 4 oxide ions and oxide ions coordinated at 8 potassium.
K 2 O is a basic oxide and reacts violently with water to produce caustic potassium hydroxide. It is deliquescent and absorbs water from the atmosphere, initiating this vigorous reaction.
Potassium oxide is reversibly oxidized to potassium peroxide at 350 ° C, reacts violently with acids, such as hydrochloric acid, to form potassium salts according to the reaction:
K 2 O + 2HCl → 2KCl + H 2 O.
The compound reacts with nitrogen dioxide to form potassium nitrate and nitrite at temperatures between 150 and 200 ° C:
K 2 O + 2NO 2 = KNO 2 + KNO 3
Potassium oxide reacts at low temperatures with ammonia to form amides and potassium hydroxide according to the reaction:
K 2 O + NH 3 (1) → KNH 2 ↓ + KOH (-50 ° C).
Reactivity and hazards
Potassium oxide is an unstable substance. It is easily oxidized to other potassium oxides, peroxide, or potassium acid oxide (KHO). The compound is not combustible but reacts vigorously and exothermically with water to form potassium hydroxide (KOH).
The solution of potassium oxide in water is a strong base, it reacts violently with acid and is corrosive. Reacts violently with water producing potassium hydroxide. Attacks many metals in the presence of water (National Institute for Occupational Safety and Health, 2014).
The substance is corrosive to the eyes, the skin and the respiratory tract, as well as when ingested. Inhalation of aerosol can cause pulmonary edema. Symptoms of pulmonary edema often do not appear for a few hours and are aggravated by physical exertion.
In case of contact with the eyes, check whether you are wearing contact lenses and remove them immediately. Eyes should be flushed with running water for at least 15 minutes, with the eyelids open. Cold water can be used. Eye ointment should not be used.
If the chemical comes into contact with clothing, remove it as quickly as possible, protecting your own hands and body. Place the victim under a safety shower.
If the chemical accumulates on the victim's exposed skin, such as hands, the contaminated skin is gently and carefully washed with running water and non-abrasive soap. Cold water can be used. If irritation persists, seek medical attention. Wash the contaminated clothing before using it again.
If the contact with the skin is severe, it should be washed with a disinfectant soap and cover the contaminated skin with an antibacterial cream.
In case of inhalation, the victim should be allowed to rest in a well-ventilated area. If inhalation is severe, the victim should be evacuated to a safe area as soon as possible.
Loosen tight clothing such as a collar, belt, or tie. If it is difficult for the victim to breathe, oxygen should be administered. If the victim is not breathing, mouth-to-mouth resuscitation is performed.
Always keeping in mind that it may be dangerous for the person providing aid to give mouth-to-mouth resuscitation when the inhaled material is toxic, infectious, or corrosive.
In case of ingestion, do not induce vomiting. Loosen tight clothing such as shirt collars, belts, or ties. If the victim is not breathing, perform mouth-to-mouth resuscitation. In all cases, immediate medical attention should be sought (IPCS, SF).
Applications
The chemical formula K 2 O (or simply "K") is used in several industrial contexts: NPK numbers for fertilizers, in cement formulas and in glass formulas.
Potassium oxide is often not used directly in these products, but the amount of potassium is reported in terms of K 2 O equivalents for any type of potassium compounds used, such as potassium carbonate.
Potassium oxide is about 83% potassium by weight, while potassium chloride is only 52%. Potassium chloride provides less potassium than an equal amount of potassium oxide.
Therefore, if a fertilizer is 30% potassium chloride by weight, its standard potassium value, based on potassium oxide, would be only 18.8%. Between 10 and 100 tonnes per year of this substance is manufactured and / or imported into the European Economic Area.
This substance is used in laboratory chemicals, fertilizers, polymers, and plant protection products. K 2 O has an industrial use that results in the manufacture of another substance (use of intermediate products).
Potassium oxide is used in the areas of mixing formulation and / or repackaging and agriculture, forestry and fishing. This substance is used for the manufacture of chemicals, plastic products and mineral products (eg plaster, cement).
The release into the environment of potassium oxide is likely to occur through industrial use: as an intermediate step in the manufacture of another substance (use of intermediates), formulation of mixtures, as a processing aid and industrial processing of abrasion with low speed release, cutting, machining or polishing metal).
Other environmental release of this substance is possible from indoor use eg, machine wash / detergent fluids, car care products, paints and coatings or adhesives, fragrances and air fresheners.
Also for indoor use in closed systems with minimal release such as cooling fluids in refrigerators, oil-based electric heaters.
Potassium oxide is used outdoors in long-lasting materials with a low release rate, for example metal, wood and plastic building and construction materials.
Indoors, it is used in long-lasting materials with low release rate such as furniture, toys, building materials, curtains, footwear, leather products, paper and cardboard products, electronic equipment.
This substance can be found in products with stone, plaster, cement, glass or ceramic-based material (for example, dishes, pots / pans, food storage containers, construction material and insulation) (European chemical agency, 2017).
Potassium oxide is a thermally stable, highly insoluble source of potassium suitable for glass, optical and ceramic applications. Oxide compounds do not conduct electricity.
However, certain structured oxides of perovskite are electronic conductors that find application in the cathode of solid oxide fuel cells and oxygen generation systems.
They are compounds that contain at least one oxygen anion and one metal cation. They are extremely stable making them useful in producing ceramic structures such as clay bowls or for advanced electronics.
It is also used in lightweight structural components in aerospace and electrochemical applications such as fuel cells where they exhibit ionic conductivity.
Metal oxide compounds are basic anhydrides and therefore can react with acids and strong reducing agents in redox reactions.
References
- American elements. (SF). Potassium Oxide. Recovered from americanelements.com.
- EMBL-EBI. (2016, September 19). potassium oxide. Recovered from ChEBI: ebi.ac.uk.
- European chemical agency. (2017, January 12). Dipotassium oxide. Recovered from echa.europa.eu.
- (SF). POTASSIUM OXIDE. Recovered from inchem.org.
- National Center for Biotechnology Information.. (2017, April 29). PubChem Compound Database; CID = 9989219. Recovered from pubchem.ncbi.nlm.nih.gov.
- National Institute for Occupational Safety and Health. (2014, July 1). POTASSIUM OXIDE. Recovered from cdc.gov.
- POTASSIUM OXIDE K2O. (SF). Recovered from allreactions.com.
- Royal Society of Chemistry. (2015). Potassium oxidopotassium. Recovered from chemspider.com.