Barium carbonate
| Barium carbonate | |
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Other names
Witherite
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| Identifiers | |
| CAS number | 513-77-9  |
| ChemSpider | 10121 |
| EC number | 208-167-3 |
| UN number | 1564 |
| RTECS number | CQ8600000 |
| SMILES |
[Ba+2].[O-]C([O-])=O
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| InChI |
1/CH2O3.Ba/c2-1(3)4;/h(H2,2,3,4);/q;+2/p-2
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| InChI key | AYJRCSIUFZENHW-NUQVWONBAT |
| Properties | |
| Molecular formula | BaCO3 |
| Molar mass | 197.34 g/mol |
| Appearance | white crystals |
| Density | 4.286 g/cm3 |
| Melting point |
811 °C |
| Boiling point |
1360 °C (decomp) |
| Solubility in water | 0.0024 g/100 mL (20 °C) |
| Solubility | soluble in HCl, HNO3, ethanol insoluble in H2SO4 |
| Refractive index (nD) | 1.60 |
| Hazards | |
| MSDS | ICSC 0777 |
| EU Index | 056-003-00-2 |
| EU classification | Harmful (Xn) |
| R-phrases | R22 |
| S-phrases | (S2), S24/25 |
| NFPA 704 |
 0
2
0
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| Flash point | Non-flammable |
| LD50 | 418 mg/kg, oral (rat) |
| Related compounds | |
| Other cations | Magnesium carbonate Calcium carbonate Strontium carbonate |
 (what is this?) (verify)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Barium carbonate (BaCO3), also known as witherite, is a chemical compound used in rat poison, bricks, ceramic glazes and cement.
Witherite crystallizes in the orthorhombic system. The crystals are invariably twinned together in groups of three, giving rise to pseudo-hexagonal forms somewhat resembling bipyramidal crystals of quartz, the faces are usually rough and striated horizontally.
The mineral is named after William Withering, who in 1784 recognized it to be chemically distinct from barytes. It occurs in veins of lead ore at Hexham in Northumberland, Alston in Cumbria, Anglezarke, near Chorley in Lancashire and a few other localities. Witherite is readily altered to barium sulfate by the action of water containing calcium sulfate in solution and crystals are therefore frequently encrusted with barytes. It is the chief source of barium salts and is mined in considerable amounts in Northumberland. It is used for the preparation of rat poison, in the manufacture of glass and porcelain, and formerly for refining sugar. It is also used for controlling the chromate to sulfate ratio in chromium electroplating baths.1
Contents
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Preparation
Barium carbonate is made commercially from barium sulfide either by treatment with sodium carbonate at 60 to 70 °C (soda ash method) or by passing carbon dioxide at 40 to 90 °C.
In the soda ash process, solid or dissolved sodium carbonate is added to barium sulfide solution, and the barium carbonate precipitate is filtered, washed and dried.2
Reactions
Barium carbonate reacts with acids such as hydrochloric acid to soluble barium salts, such as barium chloride:
- BaCO3 (s) + 2 HCl (aq) → BaCl2 (aq) + CO2 (g) + H2O (l)
However, the reaction with sulfuric acid is poor, because barium sulfate is highly insoluble.
Uses
Barium carbonate is widely used in the ceramics industry as an ingredient in glazes. It acts as a flux, a matting and crystallizing agent and combines with certain coloring oxides to produce unique colors not easily attainable by other means. Its use is somewhat controversial since some claim that it can leach from glazes into food and drink. To provide a safe means of use, BaO is often used in fritted form.
In the brick, tile, earthenware and pottery industries barium carbonate is added to clays to precipitate soluble salts (calcium and magnesium sulfates) that cause efflorescence.
References
- ^ Whitelaw, G.P. (2003-10-25). "Standard Chrome Bath Control". finishing.com. http://www.finishing.com/Library/Whitelawchrome.html. Retrieved 2006-11-29.
- ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0070494398
This article incorporates text from the Encyclopædia Britannica, Eleventh Edition, a publication now in the public domain.
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