sodium tetraborate decahydrate borax

Sodium Tetraborate Decahydrate (Borax)‌

‌Sodium tetraborate decahydrate‌, commonly known as ‌borax‌, is a naturally occurring mineral and a versatile boron compound with a wide range of industrial, household, and scientific applications. Its chemical formula, ‌Na₂B₄O₇·10H₂O‌, reflects its composition of sodium, boron, oxygen, and water molecules in a crystalline structure.

‌1. Chemical Composition and Structure‌

• ‌Molecular Formula‌: Na₂B₄O₇·10H₂O

• Indicates the presence of two sodium (Na⁺) ions, four boron (B) atoms, seven oxygen (O²⁻) atoms, and ten water (H₂O) molecules per unit cell.

• ‌Crystal Structure‌: Forms colorless or white semi-transparent crystals, often appearing as granular or powdery material.

• ‌Boron Content‌: Contains approximately 11% boron by weight, making it a significant source of boron in industrial processes.

‌2. Physical Properties‌

• ‌Appearance‌: Fine, granular crystals with a smooth, soapy texture; odorless.

• ‌Solubility‌:

• Highly soluble in water (60 g/L at 20°C), forming a clear, slightly alkaline solution (pH ~9.5).

• Soluble in glycerol but sparingly soluble in ethanol.

• ‌Melting Point‌: 75°C (decahydrate form loses water at this temperature, transitioning to anhydrous sodium tetraborate).

• ‌Density‌: 1.73 g/cm³ at 25°C.

• ‌Stability‌:

• Stable under normal conditions but may slowly lose water (effloresce) in dry air.

• Decomposes at higher temperatures (~320°C), releasing water and forming anhydrous Na₂B₄O₇.

‌3. Natural Occurrence and Production‌

• ‌Mining‌: Extracted from evaporite deposits (dry lake beds) in regions like California, Turkey, and Argentina.

• ‌Processing‌:

• Mined ore is refined through dissolution, filtration, and crystallization to produce high-purity borax.

• Synthetic methods involve reacting boric acid with sodium hydroxide.

• ‌Historical Context‌: Used since ancient times for glassmaking and metallurgy; modern production scaled up in the 19th century.

‌4. Industrial and Household Applications‌

• ‌Cleaning Products‌:

• Acts as a mild abrasive and pH buffer in detergents, soaps, and laundry boosters.

• Softens water by sequestering calcium and magnesium ions, enhancing cleaning efficiency.

• ‌Industrial Processes‌:

• ‌Flux in Metallurgy‌: Used in soldering and welding to remove metal oxides (e.g., in gold refining).

• ‌Glass Manufacturing‌: Key ingredient in borosilicate glass (e.g., Pyrex) for its low thermal expansion properties.

• ‌Preservative‌: Employed as a fungicide and insecticide in wood preservation and agricultural treatments.

• ‌Laboratory Use‌:

• ‌Buffer Solution‌: Forms a borate buffer system (pH 7–10) for biological and chemical experiments.

• ‌Analytical Chemistry‌: Used to detect metal ions (e.g., cobalt, nickel) by forming colored borate complexes.

• ‌Consumer Products‌:

• ‌Cosmetics‌: Found in some skincare formulations as a mild antiseptic and pH adjuster.

• ‌DIY Crafts‌: Used in slime-making due to its ability to cross-link polymer chains (e.g., with polyvinyl alcohol).

‌5. Safety and Environmental Considerations‌

• ‌Toxicity‌:

• Low acute toxicity (LD₅₀ in rats: ~5.66 g/kg orally), but chronic exposure may cause irritation or systemic effects.

• May irritate skin, eyes, or respiratory tract; use with gloves and eye protection.

• ‌Environmental Impact‌:

• Generally low environmental toxicity but should be disposed of responsibly to avoid water contamination.

• Naturally occurring in ecosystems; mined forms require sustainable extraction practices.

‌6. Additional Notes‌

• ‌Synonyms‌: Also known as "sodium borate," "disodium tetraborate," or "月石砂" (traditional Chinese name).

• ‌Cultural Significance‌: Historically used in mummification and traditional medicine; modern applications focus on industrial efficiency.

This expanded description provides a detailed overview of sodium tetraborate decahydrate (borax), covering its chemistry, production, uses, and safety. Let me know if you'd like to focus on any specific aspect!