Effect of pressure on the dissociation constant of boric acid in water and seawater

Frank J Millero, Gary K. Ward, Antonio Lo Surdo, Fen Huang

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The sound speeds of boric acid and sodium borate in water and 0.725 m NaCl have been measured from 0 to 50 °C and to near 1 molal. These results have been used to determine the partial molal adiabatic compressibilities of B(OH) 3 and NaB(OH) 4. The partial molal volumes, v(i), and compressibilities, k(i), have been used to estimate the changes in the volume (ΔV) and compressibility (Δk) for the dissociation of boric acid in water and average seawater (0.725 m NaCl, S A ~ 35 g/kg) B(OH) 3 + H 2O = H + + B(OH) - 4 where The calculated values of ΔV and Δk were used to estimate the effect of applied pressure (P) on the dissociation constants (K P/K 0) ln(K P/K 0)=-ΔVP/RT + 0.5ΔkP 2/RT The new values of Δk in water from 0 to 1000 bar give values of K P/K 0 that are in good agreement with the measured values. The values of K P/K 0 at P = 1942 bar in water are slightly higher than the measured values. The new calculated values of K P/K 0 in seawater from 0 to 25 oC and to P = 1000 bar are in good agreement with the measured values. This means that the contributions of boric acid to the alkalinity of seawater in deep waters are not affected by the new values of K P/K 0 determined from volume studies.

Original languageEnglish (US)
Pages (from-to)83-92
Number of pages10
JournalGeochimica et Cosmochimica Acta
Volume76
DOIs
StatePublished - Jan 15 2012

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Seawater
compressibility
seawater
Compressibility
Water
acid
water
borate
alkalinity
Alkalinity
deep water
sodium
effect
boric acid
Acoustic waves

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Effect of pressure on the dissociation constant of boric acid in water and seawater. / Millero, Frank J; Ward, Gary K.; Surdo, Antonio Lo; Huang, Fen.

In: Geochimica et Cosmochimica Acta, Vol. 76, 15.01.2012, p. 83-92.

Research output: Contribution to journalArticle

Millero, Frank J ; Ward, Gary K. ; Surdo, Antonio Lo ; Huang, Fen. / Effect of pressure on the dissociation constant of boric acid in water and seawater. In: Geochimica et Cosmochimica Acta. 2012 ; Vol. 76. pp. 83-92.
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