Zinc fluoride

Description

Zinc fluoride (ZnF2) is an inorganic chemical compound. Zinc fluoride is used in the fluorination of organic compounds, in the manufacturing of phosphors for fluorescent lights, in preserving wood, in electroplating baths, in galvanizing steel, and in ceramic manufacturing for glazes and enamels. It is also used as a termite repellent, in pharmaceuticals (e.g. the inhibition of dentin demineralization and collagen degradation), as a flux for welding and soldering (e.g. aluminum).

Chemical properties

White powder. Soluble in hot acids; slightly soluble in water; insoluble in alcohol.

Physical properties

Anhydrous zinc fluoride is a white hygroscopic solid; tetragonal needles; density 4.9 g/cm³; melts at 872°C; vaporizes at 1,500°C; vapor pressure 1 torr at 1,243°C and 5 torr at 1,328°C; practically insoluble in water, 5.2 mg/L; sparingly soluble in HCl, HNO₃ and ammonia solution
The hydrated salt, ZnF₂?4H₂O, is a white crystalline solid; rhombohedral crystals; density 2.30 g/cm3; loses water of crystallization at 100°C; sparinglysoluble in water, about 1.52 g/100mL at 20°C.

The Uses of Zinc fluoride

Zinc fluoride is a white crystalline powder, used in the manufacture of phosphors for fluorescent lights. It also is used in electroplating baths, in preservation of wood, in glazes and enamels for ceramics, and in fluorination reactions of organics.

The Uses of Zinc fluoride

Zinc Difluoride inhibits the erosion of enamel in vitro. It also functions as a fluorinating agent, Lewis acid catalyst and as an additive for catalytic transformations.

Preparation

Zinc fluoride may be prepared by heating zinc hydroxide or zinc carbonate with hydrogen fluoride:
Zn(OH)2 + 2HF → ZnF2 + 2H2O
ZnCO3 + 2HF → ZnF2 + CO2 + H2O
Also, it can be precipitated by adding a solution of sodium fluoride to that of zinc acetate:
(CH3COO)2Zn + 2NaF → ZnF2 + 2CH3COONa

Hazard

Toxic material.

Flammability and Explosibility

Not classified

Safety Profile

Poison by subcutaneous route. Can react violently with potassium. A fluorination agent. When heated to decomposition it emits toxic fumes of F and ZnO. See also FLUORIDES and ZINC COMPOUNDS.

Purification Methods

A possible impurity is H2O which can be removed by heating at 100o or by heating to 800o in a dry atmosphere. Heating in the presence of NH4F produces larger crystals. It is sparingly soluble in H2O (1.51g/100mL) but more soluble in HCl, HNO3 and NH4OH. It can be stored in glass bottles. [Kwasnik in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 242 1963.]

References

[1] http://www.npi.gov.au/resource/zinc-and-compounds
[2] https://hazmap.nlm.nih.gov/category-details?id=7782&table=copytblagents
[3] Patent EP 0001677 A1: Flux for soft soldering of aluminum, a fluxed solder composition containing said flux and a method of soft soldering aluminum using said flux