Gallium trihydroxide
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Product Description
Gallium(III) hydroxide, also known as gallium trihydroxide or simply gallium hydroxide, is an inorganic compound. It is a white, amorphous, or gel-like substance that is insoluble in water and is known for its amphoteric nature, meaning it can react with both acids and bases. This compound is formed as an unstable, gelatinous white precipitate when a base, such as ammonia, is added to a solution containing Ga³⁺ salts. In nature, it is found as the rare mineral söhngeite. Gallium(III) hydroxide is a crucial intermediate in gallium chemistry, particularly for the synthesis of advanced materials like gallium oxide.
Synthesis Methods
Gallium(III) hydroxide is typically synthesized by precipitating from a solution of a Ga(III) salt, such as gallium nitrate or gallium chloride, using a base like ammonia or sodium hydroxide. For example:
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Method 1: Adjusting the aqueous gallium salt solution to a pH of approximately 3.
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Method 2: Adding a base to the aqueous gallium salt solution.
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Example Reaction:
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Ga(NO3)3(aq)+3NH3(aq)+3H2O→Ga(OH)3(s)↓+3NH4NO3(aq)
- GaCl3(aq)+3NaOH(aq)→Ga(OH)3(s)↓+3NaCl(aq)
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The precipitate forms at a pH of around 2-3 and is typically complete by a pH of 4-5.
Uses
Gallium(III) hydroxide is primarily used as an intermediate in the synthesis of other gallium compounds, especially high-purity gallium oxide (Ga₂O₃), which has applications in:
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Semiconductor Materials: Used in the production of semiconductors due to gallium’s role in electronics.
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Gas Sensors: Utilized in the development of gas sensors.
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Phosphors: Incorporated in the manufacturing of phosphors.
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Water Purification: Acts as a coagulant to remove impurities from water, similar to aluminum hydroxide.
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Catalysis: Serves as a catalyst or catalyst support in certain organic reactions.
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Gallium Metal Production: Can be an intermediate in the purification and production of metallic gallium.
Properties and Characteristics
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Chemical Formula: Ga(OH)₃
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Molar Mass: ≈ 120.74 g/mol
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Appearance: White, amorphous or gelatinous solid
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Solubility:
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Insoluble in water.
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Soluble in strong acids, forming gallium salts.
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Soluble in strong bases, forming gallate ions [Ga(OH)4]−.
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Amphoteric Nature:
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Dissolves in strong acids:
Ga(OH)3+3HCl→GaCl3+3H2O -
Dissolves in strong bases:
Ga(OH)3+OH−→[Ga(OH)4]−
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Thermal Stability:
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Forms gallium hydroxide crystals upon heating to 170°C.
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Decomposes into oxides above 420°C:
2Ga(OH)3heatGa2O3+3H2O
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Safety and Handling
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Handling Precautions: Gallium(III) hydroxide is generally safe to handle but should be treated with care due to its amphoteric nature.
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Storage: Store in a cool, dry place, away from strong acids and bases to prevent undesired reactions.
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Environmental Impact: It may cause long-lasting harmful effects to aquatic life. Dispose of waste according to local regulations.