Nomenclature
CAS number: 14075-53-7
Potassium borofluoride; potassium fluoborate; avogadrite.
BF
4K; mol wt 125.90.
B 8.59%, F 60.36%, K 31.06%.
KBF
4.
Description and references
Prepared according to the eq H3BO3 + 4HF + KOH = KBF4 + 4H2O: Vorl"ander 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.Use
Has been proposed as a flux for soldering and brazing;
filler in resin-bonded grinding wheels.