ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Solubility of Trihydrogenboric Acid in Aqueous Solutions Containing Various Cations at Different pH Values

H. Langfelderová, Ľ. Macášková, D. Makáňová, A. Mašlejová, E. Ďurčanská, F. Krejči, and Ľ. Tibenský

Department of Inorganic Chemistry, Faculty of Chemical Technology, Slovak Technical University, CS-812 37 Bratislava

Abstract: Solubility of trihydrogenboric acid in aqueous solutions of sodium, potassium, calcium, and barium hydroxides at various pH values in the 5.5 to 12.5 range was investigated. Two solubility maxima in solutions of sodium or potassium hydroxides were found depending on the pH value. The first solubility maximum is in the neutral and the second one in the strongly basic pH range. The solubility of H₃BO₃ is in KOH solutions lower than in NaOH at the neutral reaction; in the basic pH range above the value of approximately 9 the solubility increases faster than in the presence of NaOH. Solubility of trihydrogenboric acid decreases monotonously in solutions containing calcium or barium hydroxides with the rise of the pH value. Solubility differences of H₃BO₃ in the presence of various cations and at different pH values are associated with the formation of polyborates and their different solubility. In systems with the highest solubility of trihydrogenboric acid sodium or potassium pentaborate (neutral region), or metaborates (basic region) are equilibrated with the saturated solutions.

Full paper in Portable Document Format: 471a23.pdf

Chemical Papers 47 (1) 23–27 (1993)