- Structure
- Nomenclature
- Physical properties
- Physical state
- Molecular weight
- Melting point
- Boiling point
- Density
- Solubility
- Chemical properties
- Risks
- Obtaining
- Applications
- As a desiccant for organic solvents
- In discharge lamps
- In the manufacture of ceramics
- In the preparation of cement mixtures
- In various applications
- References
The barium oxide is formed by an inorganic solid atom barium (Ba) and oxygen (O). Its chemical formula is BaO. It is a white crystalline solid and is hygroscopic, that is, it absorbs moisture from the air, but in doing so it reacts with it.
The rapid reaction of barium oxide with water makes it used in chemical analysis laboratories to dry out, that is, remove water from organic solvents, which are liquid compounds that serve to dissolve other substances.
Barium oxide BaO solid. Leiem. Source: Wikimedia Commons.
BaO behaves like a strong base, therefore it reacts with many types of acids. For example, it easily reacts with carbon dioxide CO 2 in the air to form barium carbonate BaCO 3.
It is used in the manufacture of polymers for power cables and as an ingredient for resins to seal holes in teeth that have been cured.
Barium oxide (BaO) is also used in the ceramic industry, both to coat it with glaze and to manufacture it. It is also used in cement mixtures to increase the compressive strength of the final product.
Structure
Barium oxide BaO is made up of a Ba 2+ cation and an oxygen O 2 - anion.
Barium oxide BaO ions. Author: Marilú Stea.
In its crystals, BaO forms cubic ionic networks (cube-shaped) of the sodium chloride type.
Cube-shaped crystalline structure of barium oxide BaO similar to sodium chloride. Green: barium. Blue: oxygen. Benjah-bmm27 (talk · contribs). Source: Wikimedia Commons.
The electron configuration of the barium ion is: 6s 0 because it has lost the two electrons of the 6s shell. This configuration is very stable.
Nomenclature
-Barium oxide
-Barium monoxide
Physical properties
Physical state
Yellowish-white crystalline solid.
Molecular weight
153.33 g / mol
Melting point
1923 ºC
Boiling point
Approximately 2000 ºC.
Density
5.72 g / cm 3
Solubility
Slightly soluble in water: 3.8 g / 100 mL at 20 ºC.
Chemical properties
Barium oxide BaO reacts rapidly with water, giving off heat and forming a corrosive solution of barium hydroxide Ba (OH) 2, which is the most soluble hydroxide of alkaline earth metal hydroxides.
BaO + H 2 O → Ba (OH) 2
BaO is a strong base. Reacts exothermically (ie with evolution of heat) with all types of acids.
With CO 2, BaO reacts to form barium carbonate BaCO 3.
BaO + CO 2 → BaCO 3
BaO is hygroscopic, so if it is left exposed to the environment, it joins little by little with the humidity of the air, forming Ba (OH) 2 which combines with the carbon dioxide CO 2 of the air to give barium carbonate BaCO 3.
When barium monoxide BaO is heated in the presence of air, it combines with oxygen to form barium peroxide BaO 2. The reaction is reversible.
2 BaO + O 2 ⇔ 2 BaO 2
In the presence of water, it can react with aluminum Al or zinc Zn, forming the oxides or hydroxides of said metals and generating hydrogen gas H 2.
May initiate polymerization of polymerizable organic compounds, such as epoxides.
Risks
May be toxic by ingestion. It must not come into contact with the skin. It is irritating to the eyes, skin and respiratory tract. It can be harmful to the nervous system. It is capable of causing low potassium levels, resulting in heart and muscle disorders.
Obtaining
Barium oxide BaO can be obtained by heating barium carbonate BaCO 3 with charcoal. BaO is formed and carbon monoxide gas CO is evolved.
BaCO 3 + C → BaO + 2 CO ↑
Applications
As a desiccant for organic solvents
Due to its ease of reacting with water, BaO has been used since the middle of the last century as a desiccant for gasoline and basic or neutral organic solvents.
BaO is very active drying around it, it takes up moisture very quickly, with considerable heat evolution, forming barium hydroxide Ba (OH) 2 which is stable up to 1000 ºC. For this reason, BaO can be used at high temperatures.
It also has a high water absorption capacity. For each molecule of BaO, one molecule of water can be absorbed and the resulting Ba (OH) 2 can also absorb a certain amount of water.
It is suitable for analytical chemistry laboratories. It is not sticky.
It can be used in desiccators, which are large glass containers with a lid where the internal environment is kept dry. The BaO keeps the miniature atmosphere of the desiccator dry.
Desiccators in a laboratory. Solid desiccant such as BaO is placed at the bottom of the base. The original uploader was Rifleman 82 at English Wikipedia.. Source: Wikimedia Commons.
These desiccators are used to place substances or reagents and thus prevent them from absorbing water from the environment.
It is also used to dry basic gases such as NH 3 ammonia.
In discharge lamps
BaO is placed on the electrodes of discharge lamps as an electron emitting material.
Discharge lamps are made of a tube of glass, quartz or other suitable material, they contain an inert gas and in most cases a metal vapor. The metallic vapor can be sodium or mercury.
Mercury lamp. Dmitry G. Source: Wikimedia Commons.
Electric discharges occur inside the tube because it has a positive and a negative electrode.
The BaO is placed on the electrodes of the lamp. The electrons that it emits collide with the atoms of the metal's vapor and transmits energy to them.
Passing an electrical current through this gas or vapor produces visible light or ultraviolet (UV) radiation.
In the manufacture of ceramics
BaO is used in ceramic glaze coating compositions.
Building facade covered with glazed ceramic. Penny Mayes / Glazed façade. Source: Wikimedia Commons.
However, it has also been tested as an additive in the preparation of glass-ceramic.
BaO effectively improves the mechanical characteristics and chemical resistance of this type of ceramic. It has a strong influence on the thermal properties and the composition of the crystalline phase of the materials obtained.
In the preparation of cement mixtures
BaO has been tested as a component of phosphoaluminate cement.
This type of cement is useful in marine environments, since it does not have the same tendency to hydrate as other types of cement, so it does not suffer from pore formation or expansion.
However, phosphoaluminate cements need to be strengthened in their mechanical performance in order to withstand ocean currents and blows from floating pieces of ice present in the ocean.
The addition of BaO to the phosphoaluminate cement modifies the mineral structure of said material, improves the pore structure and considerably increases the compressive strength of the cement paste.
In other words, BaO improves the compressive strength of this type of cement.
Mix for concrete. Barium oxide BaO is useful for improving certain properties of cement. Thamizhpparithi Maari. Source: Wikimedia Commons.
In various applications
It is used as an ingredient to provide opacity in dental resins for filling holes in teeth, performed by dentists.
It is also used as a nucleating agent for the preparation of polyvinylidene fluoride polymers that are used to insulate power cables.
References
- Partyka, J. et al. (2016). Effect of addition of BaO on sintering of glass-ceramic materials from SiO 2 -Al 2 O 3 -Na 2 O-K 2 O-CaO / MgO system. J Therm Anal Calorim (2016) 125: 1095. Recovered from link.springer.com.
- Zhang, P. et al. (2019). Effect of BaO on mineral structure and hydration behavior of phosphoaluminate cement. J Therm Anal Calorim (2019) 136: 2319. Recovered from link.springer.com.
- US National Library of Medicine. (2019). Barium oxide. Recovered from pubchem.ncbi.nlm.nih.gov.
- Smith, NA (2003). Lighting. Principle. In Electrical Engineer's Reference Book (Sixteenth Edition). Recovered from sciencedirect.com.
- Ebnesajjad, S. (2003). Fluoropolymer Foams. Foaming PVDF. In Melt Processible Fluoroplastics. Recovered from sciencedirect.com.
- Booth, HS and McIntyre, LH (1930). Barium Oxide as a Dessicant. Ind. Eng. Chem. Anal. Ed. 1930, 2, 1, 12-15. Recovered from pubs.acs.org.