Chemical Properties
Ammonium bifluoride.
Chemical Properties
white scales or flakes, also referred to asammonium hydrogen fluoride, anunonium difluoride and anunonium acid fluoride.
Physical properties
Orthorhombic or tetragonal crystals; etches glass; deliquescent; density 1.50 g/cm3; refractive index 1.390; melts at 125.6°C; very soluble in water; slightly soluble in alcohol.
Uses
In manufacture of Mg and Mg alloys; in brightening of Al; for purifying and cleansing various parts of beer-dispensing apparatus, tubes, etc., sterilizing dairy and other food equipment; in glass and porcelain industries; as mordant for aluminum; as a "sour" in laundering cloth. In lab production of HF.
Uses
Ammonium hydrogen fluoride is used as a chemical reagent in analysis and an antiseptic. It is also used in ceramics, electroplating, component of glass etchants as well as food processing equipment disinfectant. It acts as an intermediate in the production of hydrofluoric acid from hexafluorosilicic acid.
General Description
Ammonium bifluoride solution is the white crystalline solid dissolved in water. Ammonium hydrogen difluoride is corrosive to metals and tissue. Ammonium hydrogen difluoride is used in ceramics.
Air & Water Reactions
Dissolves in water and forms a weak solution of hydrofluoric acid.
Reactivity Profile
AMMONIUM BIFLUORIDE reacts violently with bases. In presence of moisture will corrode glass, cement, and most metals. Flammable hydrogen gas may collect in enclosed spaces. Do not use steel, nickel, or aluminum containers [USCG, 1999].
Hazard
Corrosive to skin.
Health Hazard
TOXIC; inhalation, ingestion or skin contact with material may cause severe injury or death. Contact with molten substance may cause severe burns to skin and eyes. Avoid any skin contact. Effects of contact or inhalation may be delayed. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause pollution.
Fire Hazard
Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Some are oxidizers and may ignite combustibles (wood, paper, oil, clothing, etc.). Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated.
Flammability and Explosibility
Non flammable
Safety Profile
Caustic poison and strong irritant by all routes. See also HYDROFLUORIC ACID. When heated to decomposition it emits very toxic fumes of F-, NO,, and NH3.
Potential Exposure
It is used as a sterilizer, in dairy and
brewery operations; in the ceramic, glass, and electroplating
industries; as a laundry sour.
Shipping
Administer oxygen if breathing is difficult. Remove and isolate
contaminated clothing and shoes. In case of contact with
substance, immediately flush skin or eyes with running
water for at least 20 minutes. For minor skin contact, avoid
spreading material on unaffected skin. Keep victim warm
and quiet. Effects of exposure (inhalation, ingestion or skin
contact) to substance may be delayed. Ensure that medical
personnel are aware of the material(s) involved and take precautions
to protect themselves. Medical observation is
recommended for 24 to 48 hours after breathing overexposure,
as pulmonary edema may be delayed. As first aid for
pulmonary edema, a doctor or authorized paramedic may
consider administering a drug or other inhalation therapy.
Properties and Applications
Ammonium hydrogen difluoride (NH4HF2) is an inexpensive reagent compared to known anticaries fluorides such as NaF, SnF2, etc. In addition, ammonium bifluoride is reported as a potent inhibitor of caries-like lesion formation in vitro. For instance, Tyler and Poole have studied fluoride uptake by human surface enamel from ammonium bifluoride in vitro. They noticed a reduction in the penetration of caries-like lesions in the case of specimens treated with 1% aq. NH4HF2. A study reports the fluorination of hydroxyapatite powder using ammonium hydrogen difluoride as a fluorinating agent by three different routes, viz., solid-state method, reflux method, and pH cycle method. The FT-IR and powder XRD results confirm the inter-diffusion of ‘F’ and ‘OH’- ions and the formation of homogeneous products of partially fluorinated hydroxyapatite. Compared to many other fluoride sources, NH4HF2 has the advantages of solubility and cost[1].
Incompatibilities
Incompatible with oxidizers (chlorates,
nitrates, peroxides, permanganates, perchlorates, chlorine,
bromine, fluorine, etc.); contact may cause fires or explosions.
Keep away from alkaline materials, strong bases,
strong acids, oxoacids, epoxides. In the presence of moisture
corrodes concrete, metals, glass.
Waste Disposal
May be buried in a specially
designated chemical landfill. Aqueous wastes may be reacted with an excess of lime followed by lagooning and
either recovery or land disposal of the separated calcium
fluoride.
References
[1] V. Geetha, G. Buvaneswari. “Ammonium hydrogen difluoride induced fluorination of hydroxyapatite.” Materials Research Bulletin 45 12 (2010): Pages 1866-1870.
