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Element Index (B)
Barium
Beryllium
Bismuth
Bromine
Boron
Chemical's truth
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Ricin is a natural poison extracted from the castor oil bean with a quoted LD50 of 20,000 ng/kg. |
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Barium sulfate
(Barytes, Blanc fixe, Barosperse)
CAS no: 7727-43-7 Formula: BaSO4 Molecular weight: 233.391
Physical Data
Appearance: Fine, white polymorphous crystals.
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Melting point: 1580°C
Boiling point: -
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Density: 4.49 g/cm3
Solubility: 0.00031 g/100 g H2O (20°C)
Solubility product: 1.08 x 10-10
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Thermodynamic Data
Enthalpy of formation: -1473.2 kJ/mol
Gibbs energy of formation: -1362.2 kJ/mol
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Entropy: 132.2 J/mol K
Heat capacity: 101.8 J/mol K
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Production and preparation
Occurs in nature as barytes (barite or heavy spar), which is the chief ore of barium.
It can be prepared as a precipitate by adding dilute sulfuric acid to barium chloride solution.
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Behavior and Chemical Properties
It is practically insoluble in water, dilute acids and ethanol, but soluble in hot concentrated sulfuric acid.
The rhombic form of the crystals can be changed to monoclinic form around 1149°C.
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History and Uses
It is used in manufacture of photographic paper, artificial ivory, cellophane and filler for paper. For instance, baryta paper which is a
paper coated on one side with an emulsion of barium sulfate and gelatine for photographic printing paper. Also useful as
color pigment for paper and wallpaper and pigment extender in surface coating materials (blanc fixe).
It is also used as a suspension in the water for diagnostic aid and X-ray contrast medium of the stomach and intestine. The radiopaque
property is also found its use in heavy concrete for radiation shield.
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Hazard, Storage and Handling
Barium sulfate is stable in room temperature and decompose only at very high temperature to form oxides of sulfur, barium fume.
Store in a cool, dry and well ventilated area and away from incompatible materials, such as aluminium.
Barium compounds are usually very poisonous, but the sulfate is quite safe because its extrememly low solubility in water. However,
repeated exposure may cause baritosis characterized by deposition of particulate matter in the lung.
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(Last update: November 2004) |
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