Acetylene tetrabromide, also known as 1,1,2,2-tetrabromoethane (C₂H₂Br₄), is a dense, non-flammable liquid widely used in industry as a flotation medium and in specialized chemical applications. Its high density, stability, and solubility profile make it valuable for mineral separation and laboratory processes, though its toxicity requires strict handling protocols.
🔬 Chemical Identity and Structure
- Formula: C₂H₂Br₄
- Molecular Weight: ~345.7 g/mol
- Synonyms: Acetylene tetrabromide, symmetrical tetrabromoethane, tetrabromoacetylene, TBE
- CAS Number: 79-27-6
- Structure: Derived from acetylene by substitution of four bromine atoms, resulting in a halogenated ethane derivative.
⚗️ Physical Properties
- Appearance: Colorless to pale yellow oily liquid, often amber in industrial samples
- Odor: Pungent, reminiscent of camphor or iodoform
- Boiling Point: ~243–244 °C (decomposes at high temperature)
- Melting Point: ~0–1 °C (solidifies near freezing)
- Density / Specific Gravity: ~2.97 g/cm³ at 25 °C (very dense compared to water)
- Solubility:
- Slightly soluble in water (~0.065–0.07% at 30 °C)
- Miscible with organic solvents such as alcohol, ether, chloroform, carbon tetrachloride, and acetic acid
- Vapor Pressure: Very low (~0.02 mmHg at 20 °C), reducing volatility hazards
⚙️ Industrial and Laboratory Applications
- Mineral Separation:
- Its high density makes acetylene tetrabromide ideal for heavy liquid separation in geology and mineralogy.
- Used to distinguish minerals based on specific gravity, particularly in petrographic and sedimentary studies.
- Chemical Intermediate:
- Serves as a reagent in organic synthesis, especially in halogenation reactions.
- Occasionally used in the preparation of other brominated compounds.
- Analytical Chemistry:
- Applied in density gradient experiments and as a calibration medium for specific gravity measurements.
⚠️ Safety and Hazards
- Toxicity: Classified as hazardous; inhalation or ingestion can cause serious injury.
- Regulatory Limits:
- OSHA Permissible Exposure Limit (PEL): 1 ppm (14 mg/m³)
- NIOSH IDLH (Immediately Dangerous to Life or Health): 8 ppm
- Health Risks:
- Can affect the liver, kidneys, and central nervous system.
- Prolonged exposure may lead to permanent injury.
- Fire/Explosion Risk: Non-flammable under typical conditions, but decomposes when heated strongly.
- Handling: Requires protective equipment (gloves, goggles, fume hood) and proper storage away from reducing metals and strong bases.
📖 Historical and Scientific Notes
- Discovery: Developed as a halogenated derivative of acetylene in the late 19th century.
- Legacy Use: Once considered for use in density-based separation processes before safer alternatives were developed.
- Modern Context: Still used in specialized laboratories, though environmental and health concerns have limited its widespread adoption.
✨ Conclusion
Acetylene tetrabromide is a dense, halogenated liquid with niche but important applications in mineral separation and chemical synthesis. Its unique physical properties—particularly high density and miscibility with organic solvents—make it valuable in technical fields. However, its toxicity and regulatory restrictions mean that it must be handled with extreme care. For geologists, chemists, and industrial users, acetylene tetrabromide remains a specialized tool where precision and density control are critical.
In short: Acetylene tetrabromide is a dense, non-flammable liquid used in mineral separation and synthesis, but requires strict safety precautions due to toxicity.
