Abstract
Boron is known to interact with a wide variety of protonated ligands(HL) creating complexes of the form B(OH)2L-.Investigation of the interaction of boric acid and bicarbonate in aqueoussolution can be interpreted in terms of the equilibrium
\(B(OH)_3^0 + HCO_3^ - \rightleftharpoons B(OH)_2 CO_3^ - + H_2 O\)
The formation constant for this reaction at 25 °C and 0.7 molkg-1 ionic strength is
\(K_{BC} = \left[ {B(OH)_2 CO_3^ - } \right]\left[ {B(OH)_3^0 } \right]^{ - 1} \left[ {HCO_3^ - } \right]^{ - 1} = 2.6 \pm 1.7\)
where brackets represent the total concentration of each indicatedspecies. This formation constant indicates that theB(OH)2 \(CO_3^ - \) concentration inseawater at 25 °C is on the order of 2 μmol kg-1. Dueto the presence of B(OH)2 \(CO_3^ - \), theboric acid dissociation constant (\(K\prime _B \)) in natural seawaterdiffers from \(K\prime _B \) determined in the absence of bicarbonate byapproximately 0.5%. Similarly, the dissociation constants of carbonicacid and bicarbonate in natural seawater differ from dissociation constantsdetermined in the absence of boric acid by about 0.1%. Thesedifferences, although small, are systematic and exert observable influenceson equilibrium predictions relating CO2 fugacity, pH, totalcarbon and alkalinity in seawater.
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McElligott, S., Byrne, R.H. Interaction of B\((OH)_3^0 \) and \(HCO_3^ - \) in Seawater: Formation of B\((OH)_2 CO_3^ - \) . Aquatic Geochemistry 3, 345–356 (1997). https://doi.org/10.1023/A:1009633804274
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DOI: https://doi.org/10.1023/A:1009633804274