CAS Registry Number: 14075-53-7
Additional Names: Potassium borofluoride; potassium fluoborate; avogadrite
Molecular Formula: BF4K
Molecular Weight: 125.90
Percent Composition: B 8.59%, F 60.36%, K 31.06%
Line Formula: KBF4
Literature References: Prepared according to the eq H3BO3 + 4HF + KOH = KBF4 + 4H2O: Vorländer et al., Ber. 65, 535 (1932); Kwasnik in Handbook of Preparative Inorganic Chemistry vol. 1, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1963) p 223. For other methods of prepn see H. S. Booth, D. R. Martin, Boron Trifluoride and Its Derivatives (New York, 1949) pp 99-106.
Properties: Orthorhombic bipyramidal or cubic crystals. d420 2.505. mp 530°. Soly in water (g/100 g): 0.3 (3°); 0.448 (20°); 0.55 (25°); 1.4 (40°); 6.27 (100°). Index of refraction of solns is lower than that of water. A satd soln (0.6%) on heating gives color effects, if excess crystals are added. With a 10% aq soln a transparent blue color appears at 100°, turning green at 90°, and yellow at 60°. In a concd fluoboric acid soln these phenomena occur with variations in room temp. Aq solns of KBF4 are at first neutral to litmus, but upon standing, diluting, or heating become acidic without etching their glass containers. Slightly sol in boiling alc.
Melting point: mp 530°
Density: d420 2.505
Use: Has been proposed as a flux for soldering and brazing; filler in resin-bonded grinding wheels.
Potassium tetrafluoroborate is KBF4 orthorhombic or cubic crystal.It is used as a flux in welding and fusion of silver, gold, stainless steel, etc. to provide a net light metal waste.