Ammonium Bifluoride, Ammonium Hydrogen Fluoride, Ammonium Hydrogen Difluoride, Etching Powder, 1341-49-7

Ammonium Bifluoride, Ammonium Hydrogen Fluoride, Ammonium Hydrogen Difluoride, Etching Powder, 1341-49-7
Ammonium Bifluoride (NH₄HF₂)

1. Chemical Identity

• Name: Ammonium Bifluoride (also called Ammonium Hydrogen Fluoride)

• Formula: NH₄HF₂

• Molecular Weight: 57.04 g/mol

• CAS Number: 1341-49-7

• Structure: Contains an ammonium cation (NH₄⁺) and a bifluoride anion (HF₂⁻). The HF₂⁻ ion is stabilized by a strong hydrogen bond, giving the compound high reactivity.

2. Physical and Chemical Properties

• Appearance: White, odorless crystalline solid (orthorhombic, tetragonal, or rhombic forms).

• Density: 1.50 g/cm³

• Melting Point: 125.6 °C

• Boiling Point: 240 °C

• Solubility: Highly soluble in water and ethanol; poorly soluble in ether.

• pH (5% solution): ~3.5 (acidic).

• Reactivity: Strongly corrosive, reacts violently with bases, and in humid conditions corrodes glass, cement, and metals.

3. Production

• Main route: Reaction of hydrofluoric acid (HF) with ammonia (NH₃).

• Alternative methods:

  • Dehydration of ammonium fluoride solutions.

  • Reaction involving sulfuric acid.

  • Reductive ammonation in glycol media.

4. Industrial Applications

• Glass industry: Etching and smoothing of silica-based glass surfaces.

• Electronics: Surface treatment and cleaning chemicals.

• Metallurgy:

  • Steel: Rust removal, surface preparation.

  • Aluminum: Polishing and etching.

• Petroleum & Gas:

  • Acidizing wells to dissolve silicates and sandstone.

  • Enhancing productivity by generating HF in situ.

• Energy plants: Cleaning calcium-silica deposits in cooling towers.

• Food industry: Sterilization of milk and certain food-processing equipment.

• Ceramics & coatings: Component in bright dipping baths and surface finishing agents.

• Cleaning products: Degreasing and heavy-duty detergents.

5. Safety and Health Hazards

• Corrosive: Causes severe burns on skin and eyes.

• Inhalation risk: Dust and vapors irritate respiratory tract.

• Toxicity: Can lead to hypocalcemia, cardiac arrhythmias, and respiratory distress.

• First aid measures:

  • Skin → rinse with water, apply calcium gluconate gel.

  • Eyes → flush with water for at least 15 minutes.

  • Inhalation → move to fresh air, provide oxygen if needed.

  • Ingestion → seek immediate medical attention (do not induce vomiting).

6. Environmental Impact

• Water pollution: Releases fluoride ions, toxic to aquatic life.

• Soil contamination: Alters pH, reduces fertility, harms microorganisms.

• Ecosystem risk: Hydrofluoric acid formation damages plants and animals.

7. Packaging and Trade

• Packaging: Resistant plastic bottles or drums (never steel, nickel, or aluminum).

• Labeling: Must include hazard warnings, handling instructions, and first aid guidelines.

• Trade: Subject to strict international regulations for transport, storage, and import/export.

8. Key Comparisons

• Ammonium Bifluoride vs. Hydrofluoric Acid:

  • ABF is a crystalline salt that releases HF upon dissolution.

  • HF is a pure, highly corrosive acid.

• Ammonium Bifluoride vs. Ammonium Chloride:

  • ABF is corrosive and fluoride-based.

  • Ammonium chloride is milder, often used as fertilizer.

Summary

Ammonium Bifluoride is a highly versatile but hazardous industrial chemical. It plays a critical role in glass etching, metal treatment, petroleum extraction, and cleaning formulations, but requires strict safety protocols due to its corrosive and toxic nature. Its dual role as a surface treatment agent and a controlled HF source makes it indispensable in several industries, yet environmentally and biologically dangerous if mishandled.