Barium Sulfate(BaSO4)

(B) Precipitable barium sulfate
As well known as a method of detecting or quantitatively analysing the radical of sulfuric acid, barium sulfate is created by applying bariumate solution to a solution containing the radical of sulfuric acid.
Industrially, the barite powder mixed with reducers such as cokes and coal powders is reduced at 700~1000℃ in a rotary kiln. Apply the water to the black ashes obtained from this process to leach the barium sulfate.
Create a sediment by having the leached barium sulfate react with the refined sodium sulfate solution.
After separating the water from the sediment, make a product by rinsing, filtering, drying and then crushing the sediment.

BaSO4 + 4C → BaS + 4CO
BaS + NaSO4 → BaSO4 + Na2S

As the size of particles varies depending on the concentration of raw material solution, and temperature and velocity of reaction, set the reaction conditions according to applications.
There is also a method of having sulfuric acid, instead of sodium sulfate, react with barium sulfide.

BaS + H2SO4 → BaSO4 + H2S

There is another method available. This method is to have the barium chloride solution prepared by leaching black ashes with hydrochloric acid, not water, react with sodium sulfate or sulfuric acid.

BaS + 2HCl → BaCl2 + H2S
BaCl + Na2SO4 → BaSO4 + 2NaCl

This is also an method that is to have the barium chloride solution obtained by crushing the barite(BaSO4) and dissolving it in hydrochloric acid react with sulfuric acid or sodium sulfate.

BaCO3 + 2HCl → BaCl2 + H2O + CO3
BaCl2 + H2SO4 → BaSO4 + 2HCl

(C) Barite powder
After sorting out the barite(BaSO4) to remove impurities or poor quality parts, finely crush and sort it out again to remove coarse particles.
Add sulfuric acid, hydrochloric acid or other chemicals to such sorted baraite, and heat them to melt away impurities such as iron which are the cause of coloring.
Then, make a product through processes such as rinsing, filtering, drying and crushing. Various kinds of products are obtained according to difference in particle sizes by crushing and sorting, chemical treatment methods and conditions.

(D) Properties

1. Precipitable barium sulfate
   It is the barium sulfate(BaSO4) with high purity, which belongs to the orthorhombic system.
   It also has a high whiteness index. As chemically it is not affected by acid and alkali except for melting in copper sulfuric acid or melting alkali, it is very stable to moisture and gas.
   It is highly resistant to light, weather and heat.
   It is in the shape of the soft fine powder with specific gravity of 4.3~4.5 and particle diameter of 0.1~1μ(a particle diameter of 2~5㎛ is available), and has greater oil absorption as it is more tensile than the barite powder.
   It has the reflection coefficient of 1.64, and greater hiding power than the barite powder. If soaked in oil, it is somewhat less transparent than the barite powder.
   Generally the bariumate is toxic but the barium sulfate only is non-toxic.
2. Barite powder
   It has the same chemical properties as those of the precipitable barium sulfate.
   As it is made from crushed mineral, the powder is softer than the precipitable barium sulfate. It is small in volume but somewhat weighty.
   Its specific gravity is 4.0-4.5. The specific gravity will be lowered if it contains impurities such as kalium, alumina and silica but it is the heaviest among extender pigments.
   Its reflection coefficient is 1.63. As it has little difference from the linseed oil, so it mostly becomes transparent in oil.
   Its oil absorption is small, so it becomes the form of paste by the oil of about 9%.
3. Quality Standards
   For the precipitable barium sulfate, there are the following quality standards; JIS K5115 Precipitable Barium Sulfate and Barite Powder(Pigment), JIS K8991 Barium Sulfate(Reagent), and Japanese Pharmacopoeia Barium Sulfate. The JIS K5115 applies to the barite powder.

The standards for barite are shown in the Table 1 below

(E) Applications