Barium sulfate BaSO4 or simply Barite is a white crystalline compound of sulfuric acid and Barium insoluble in water and alcohol.
This article explains barium sulfate, its formation, properties, uses, and solubility.
We will expound on water solubility and delve deeply into why BaSO4 is insoluble in most liquids. Stick to the end.
Is BaSO4 Soluble In Water? (Barium Sulfate)
What is BaSO4?
Barium sulfate is a white crystalline solid naturally found in nature or manufactured synthetically in a laboratory.
The compound results when Barium carbonate (BaCO3) reacts with sulfuric acid (H2SO4) to form barium sulfate, carbon dioxide, and water, as shown below
BaCO3 + H2SO4 ⇒ BaSO4 + CO2 + H2O
Properties of BaSO4
Chemical formula: BaSO4
Color: Synthetic BaSO4 is pure white, but the naturally occurring Barite ranges between green, yellow, red, and gray depending on the impurities.
Crystal structure: Rhombic (space group pnma)
Refractive index: 1.64
Melting point: BaSO4 has an average melting point of 1580 °C but will always decompose in temperatures above 1600°C
Hardness: The compound has a hardness of 4.3 and 4.6 on the Mohs scale.
Solubility: BaSO4 is virtually insoluble in alcohol and water at room temperature but soluble in concentrated sulfuric acid.
Lattice parameters: a = 8.896 Å, b = 5.462°, c = 7.171 Å, V = 348.4 Å3
Molecular weight: 233.3896 g/mol
Density: 4.50 g/cm3
What Does It Mean When a Substance Is Soluble in Water or Not?
Solubility is the ability of a substance in solid, liquid, or gaseous form to dissolve in a solvent, in most cases water, to create a solution.
The solubility of a substance in water is determined by several factors, including solvent used, temperature, and pressure.
The solubility of a solid at the right temperature and pressure proceeds to an optimal point where the solution is considered saturated.
In general, what circumstances have to exist for something to be soluble or not?
The following circumstances have to exist for a substance to be soluble in water;
The solubility of sulfates formed by alkaline earth metals such as magnesium and Barium decreases down the group in the periodic table.
This is because of the increase of hydration energy with the decrease in lattice enthalpy. Barium sulfate is therefore insoluble in water.
Some substances are insoluble in cold water, but solubility increases in warm or hot water, which means that the solubility of a given substance depends on temperature.
Heat increases the vibration energy of water molecules, which vibrate faster and breaks down the solute.
For example, sugar is more soluble in hot water compared to cold water.
Pressure has an enormous effect in breaking down the structure of solids.
If a substance remains hard under certain conditions and temperatures, adding some pressure may just do the trick.
Polarity in water, loosely translated, means that a solute dissolves best in a liquid that has a similar chemical structure.
In other words, polarity means that a solid will dissolve in liquids that share the same chemical characteristics.
For example, sugar easily dissolves in water, moderately in methanol, and never in non-polar liquids such as benzene because they have different chemical characteristics.
Why Does It Matter if Something Is Soluble or Not?
Solubility dictates the usability of a substance.
It dictates the methods of extraction and how the substance can be used.
Water-soluble sulfates of Barium, for example, are toxic.
Why Is BaSO4 Insoluble in Water?
We have already said that the solubility of sulfates of alkaline earth metals decreases down the group.
Sulfates’ lattice energy remains constant while hydration energy decreases from Be2+ to Ba2+ as the number of positive electrons increases down the group.
For example, Magnesium sulfate is more soluble than barium sulfate because it is higher up the group.
Barium sulfate is only soluble in hot concentrated sulfuric acid. Other insoluble sulfates in water apart from BaSO4 include;
· Calcium sulfate
· Strontium sulfate
· Barium sulfate
· Silver sulfate
· Lead sulfate
What Is Barium Sulphate Used For?
The crude oil industry consumes around 80% of Barite (natural barium sulfate) mined globally.
The purified mineral is used as weighing mud during the drilling of oil wells because it increases the hydrostatic pressure and the density of the resultant liquid, effectively lowering the chances of a blowout.
BaSO4 is commonly used in medical practice in different diagnostic procedures like X-ray imaging as a radiocontrast agent.
The patient is fed a “barium meal “orally, or it can be injected directly into the rectum in the form of an enema.
While the substance is tasteless, the thick white formulation the patients swallow often has sweeteners, and other flavorings added.
The X-ray machine can now easily track its movement down the gastrointestinal tract.
Despite being a heavy metal whose water-soluble compounds are highly toxic, there are several reasons for its medical use.
The low solubility means much of the metal will go through the GI tract unchanged, which keeps the patients from absorbing lethal amounts.
Unlike its predecessor Thorotrast, the body’s excretory system can easily get rid of barium sulfate.
Barium has a relatively high atomic number 56 thus can absorb the X rays more effectively than compounds with lighter nuclei.
The majority of artificially produced barium sulfate makes an essential raw material in various industries.
It is used to enhance the white component in paints.
For example, barium sulfate acts as a filler or modifies consistency in oil-based paints.
Widely available white paints from your local store can only reflect 80% to 90% sunlight, but barium sulfate helps to improve solar radiation reflection properties.
Combining zinc sulfide (ZnS) with BaSO4 produces a lithopone synthetic pigment.
Barium sulfate is also useful in photography because the white coating on specific photographic papers helps to diffuse light evenly.
The baryta or a thin layer of BaSO4 creates a base surface on the paper, which boosts the reflectiveness of the imprinted image.
This method of coating the baryta layer with a light-sensitive silver halide layer was discovered in Germany in 1884.
The baryta coating protects the paper fibers from coming into contact with the light-sensitive emulsion, thus creating more uniform blacks. BaSO4 also increases the “whiteness” or brightens the papers used for ink-jet printing.
Barium sulfate is also a common raw material in manufacturing plastic fillers for vibrational mass damping applications because it makes the polymer denser.
For example, BaSO4 makes up to 70% of filler in polystyrene and polypropylene plastics. Additionally, the material increases opacity and resistance to acids and bases.
The enhanced radio-opacity makes the composite useful in X-ray shielding material instead of steel shields.
· Soil testing: Small clay particles can block the expert from seeing the indicator color. Barium sulfate binds to this cloudy mixture which sinks to the bottom, giving a clearer solution.
· Colorimetry: BaSO4 is used to measure colors because it diffuses colors almost perfectly.
· Metal casting: a thin layer of BaSO4 is applied to the mold to keep it from bonding with the molten metal.
· The sulfate is also valuable for manufacturing root canal filling, anacoustic foams, and powder coatings.
Barium sulfate (BaSO4) is practically insoluble in water and alcohol.
The substance can only dissolve in hot concentrated sulfuric acid.
The solubility of substances in water is determined by the type of substance, temperature, polarity, and pressure.
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